/*
LodePNG version 20201017

Copyright (c) 2005-2020 Lode Vandevenne
Copyright (c) 2021 Marvin Borner

This software is provided 'as-is', without any express or implied
warranty. In no event will the authors be held liable for any damages
arising from the use of this software.

Permission is granted to anyone to use this software for any purpose,
including commercial applications, and to alter it and redistribute it
freely, subject to the following restrictions:

    1. The origin of this software must not be misrepresented; you must not
    claim that you wrote the original software. If you use this software
    in a product, an acknowledgment in the product documentation would be
    appreciated but is not required.

    2. Altered source versions must be plainly marked as such, and must not be
    misrepresented as being the original software.

    3. This notice may not be removed or altered from any source
    distribution.
*/

/*
The manual and changelog are in the header file "png.h"
Rename this file to png.cpp to use it for C++, or to png.c to use it for C.
*/

#include <def.h>
#include <libgui/png.h>
#include <mem.h>
#include <sys.h>

#if defined(_MSC_VER) &&                                                                           \
	(_MSC_VER >= 1310) /*Visual Studio: A few warning types are not desired here.*/
#pragma warning(                                                                                   \
	disable : 4244) /*implicit conversions: not warned by gcc -Wall -Wextra and requires too much casts*/
#pragma warning(                                                                                   \
	disable : 4996) /*VS does not like fopen, but fopen_s is not standard C so unusable here*/
#endif /*_MSC_VER */

const char *PNG_VERSION_STRING = "20201017";

/*
This source file is built up in the following large parts. The code sections
with the "PNG_COMPILE_" #defines divide this up further in an intermixed way.
-Tools for C and common code for PNG and Zlib
-C Code for Zlib (huffman, deflate, ...)
-C Code for PNG (file format chunks, adam7, PNG filters, color conversions, ...)
-The C++ wrapper around all of the above
*/

/* ////////////////////////////////////////////////////////////////////////// */
/* ////////////////////////////////////////////////////////////////////////// */
/* // Tools for C, and common code for PNG and Zlib.                       // */
/* ////////////////////////////////////////////////////////////////////////// */
/* ////////////////////////////////////////////////////////////////////////// */

/*The malloc, realloc and free functions defined here with "png_" in front
of the name, so that you can easily change them to others related to your
platform if needed. Everything else in the code calls these. Pass
-DPNG_NO_COMPILE_ALLOCATORS to the compiler, or comment out
#define PNG_COMPILE_ALLOCATORS in the header, to disable the ones here and
define them in your own project's source files without needing to change
png source code. Don't forget to remove "static" if you copypaste them
from here.*/

#ifdef PNG_COMPILE_ALLOCATORS
static void *png_malloc(u32 size)
{
#ifdef PNG_MAX_ALLOC
	if (size > PNG_MAX_ALLOC)
		return 0;
#endif
	return malloc(size);
}

/* NOTE: when realloc returns NULL, it leaves the original memory untouched */
static void *png_realloc(void *ptr, u32 new_size)
{
#ifdef PNG_MAX_ALLOC
	if (new_size > PNG_MAX_ALLOC)
		return 0;
#endif
	return realloc(ptr, new_size);
}

static void png_free(void *ptr)
{
	if (ptr)
		free(ptr);
}
#else /*PNG_COMPILE_ALLOCATORS*/
/* TODO: support giving additional void* payload to the custom allocators */
void *png_malloc(u32 size);
void *png_realloc(void *ptr, u32 new_size);
void png_free(void *ptr);
#endif /*PNG_COMPILE_ALLOCATORS*/

/* convince the compiler to inline a function, for use when this measurably improves performance */
/* inline is not available in C90, but use it when supported by the compiler */
#if (defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L)) ||                                \
	(defined(__cplusplus) && (__cplusplus >= 199711L))
#define PNG_INLINE inline
#else
#define PNG_INLINE /* not available */
#endif

/* restrict is not available in C90, but use it when supported by the compiler */
#if (defined(__GNUC__) && (__GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 1))) ||             \
	(defined(_MSC_VER) && (_MSC_VER >= 1400)) ||                                               \
	(defined(__WATCOMC__) && (__WATCOMC__ >= 1250) && !defined(__cplusplus))
#define PNG_RESTRICT __restrict
#else
#define PNG_RESTRICT /* not available */
#endif

/* Replacements for C library functions such as memcpy and strlen, to support platforms
where a full C library is not available. The compiler can recognize them and compile
to something as fast. */

static void png_memcpy(void *PNG_RESTRICT dst, const void *PNG_RESTRICT src, u32 size)
{
	u32 i;
	for (i = 0; i < size; i++)
		((char *)dst)[i] = ((const char *)src)[i];
}

static void png_memset(void *PNG_RESTRICT dst, int value, u32 num)
{
	u32 i;
	for (i = 0; i < num; i++)
		((char *)dst)[i] = (char)value;
}

/* does not check memory out of bounds, do not use on untrusted data */
static u32 png_strlen(const char *a)
{
	const char *orig = a;
	/* avoid warning about unused function in case of disabled COMPILE... macros */
	(void)(&png_strlen);
	while (*a)
		a++;
	return (u32)(a - orig);
}

#define PNG_MAX(a, b) (((a) > (b)) ? (a) : (b))
#define PNG_MIN(a, b) (((a) < (b)) ? (a) : (b))
#define PNG_ABS(x) ((x) < 0 ? -(x) : (x))

#if defined(PNG_COMPILE_PNG) || defined(PNG_COMPILE_DECODER)
/* Safely check if adding two integers will overflow (no undefined
behavior, compiler removing the code, etc...) and output result. */
static int png_addofl(u32 a, u32 b, u32 *result)
{
	*result = a + b; /* u32 addition is well defined and safe in C90 */
	return *result < a;
}
#endif /*defined(PNG_COMPILE_PNG) || defined(PNG_COMPILE_DECODER)*/

#ifdef PNG_COMPILE_DECODER
/* Safely check if multiplying two integers will overflow (no undefined
behavior, compiler removing the code, etc...) and output result. */
static int png_mulofl(u32 a, u32 b, u32 *result)
{
	*result = a * b; /* u32 multiplication is well defined and safe in C90 */
	return (a != 0 && *result / a != b);
}

#ifdef PNG_COMPILE_ZLIB
/* Safely check if a + b > c, even if overflow could happen. */
static int png_gtofl(u32 a, u32 b, u32 c)
{
	u32 d;
	if (png_addofl(a, b, &d))
		return 1;
	return d > c;
}
#endif /*PNG_COMPILE_ZLIB*/
#endif /*PNG_COMPILE_DECODER*/

/*
Often in case of an error a value is assigned to a variable and then it breaks
out of a loop (to go to the cleanup phase of a function). This macro does that.
It makes the error handling code shorter and more readable.

Example: if(!uivector_resize(&lz77_encoded, datasize)) ERROR_BREAK(83);
*/
#define CERROR_BREAK(errorvar, code)                                                               \
	{                                                                                          \
		errorvar = code;                                                                   \
		break;                                                                             \
	}

/*version of CERROR_BREAK that assumes the common case where the error variable is named "error"*/
#define ERROR_BREAK(code) CERROR_BREAK(error, code)

/*Set error var to the error code, and return it.*/
#define CERROR_RETURN_ERROR(errorvar, code)                                                        \
	{                                                                                          \
		errorvar = code;                                                                   \
		return code;                                                                       \
	}

/*Try the code, if it returns error, also return the error.*/
#define CERROR_TRY_RETURN(call)                                                                    \
	{                                                                                          \
		u32 error = call;                                                                  \
		if (error)                                                                         \
			return error;                                                              \
	}

/*Set error var to the error code, and return from the void function.*/
#define CERROR_RETURN(errorvar, code)                                                              \
	{                                                                                          \
		errorvar = code;                                                                   \
		return;                                                                            \
	}

/*
About uivector, ucvector and string:
-All of them wrap dynamic arrays or text strings in a similar way.
-png was originally written in C++. The vectors replace the std::vectors that were used in the C++ version.
-The string tools are made to avoid problems with compilers that declare things like strncat as deprecated.
-They're not used in the interface, only internally in this file as static functions.
-As with many other structs in this file, the init and cleanup functions serve as ctor and dtor.
*/

#ifdef PNG_COMPILE_ZLIB
#ifdef PNG_COMPILE_ENCODER
/*dynamic vector of u32 ints*/
typedef struct uivector {
	u32 *data;
	u32 size; /*size in number of u32 longs*/
	u32 allocsize; /*allocated size in bytes*/
} uivector;

static void uivector_cleanup(void *p)
{
	((uivector *)p)->size = ((uivector *)p)->allocsize = 0;
	png_free(((uivector *)p)->data);
	((uivector *)p)->data = NULL;
}

/*returns 1 if success, 0 if failure ==> nothing done*/
static u32 uivector_resize(uivector *p, u32 size)
{
	u32 allocsize = size * sizeof(u32);
	if (allocsize > p->allocsize) {
		u32 newsize = allocsize + (p->allocsize >> 1u);
		void *data = png_realloc(p->data, newsize);
		if (data) {
			p->allocsize = newsize;
			p->data = (u32 *)data;
		} else
			return 0; /*error: not enough memory*/
	}
	p->size = size;
	return 1; /*success*/
}

static void uivector_init(uivector *p)
{
	p->data = NULL;
	p->size = p->allocsize = 0;
}

/*returns 1 if success, 0 if failure ==> nothing done*/
static u32 uivector_push_back(uivector *p, u32 c)
{
	if (!uivector_resize(p, p->size + 1))
		return 0;
	p->data[p->size - 1] = c;
	return 1;
}
#endif /*PNG_COMPILE_ENCODER*/
#endif /*PNG_COMPILE_ZLIB*/

/* /////////////////////////////////////////////////////////////////////////// */

/*dynamic vector of u8s*/
typedef struct ucvector {
	u8 *data;
	u32 size; /*used size*/
	u32 allocsize; /*allocated size*/
} ucvector;

/*returns 1 if success, 0 if failure ==> nothing done*/
static u32 ucvector_resize(ucvector *p, u32 size)
{
	if (size > p->allocsize) {
		u32 newsize = size + (p->allocsize >> 1u);
		void *data = png_realloc(p->data, newsize);
		if (data) {
			p->allocsize = newsize;
			p->data = (u8 *)data;
		} else
			return 0; /*error: not enough memory*/
	}
	p->size = size;
	return 1; /*success*/
}

static ucvector ucvector_init(u8 *buffer, u32 size)
{
	ucvector v;
	v.data = buffer;
	v.allocsize = v.size = size;
	return v;
}

/* ////////////////////////////////////////////////////////////////////////// */

#ifdef PNG_COMPILE_PNG
#ifdef PNG_COMPILE_ANCILLARY_CHUNKS

/*free string pointer and set it to NULL*/
static void string_cleanup(char **out)
{
	png_free(*out);
	*out = NULL;
}

/*also appends null termination character*/
static char *alloc_string_sized(const char *in, u32 insize)
{
	char *out = (char *)png_malloc(insize + 1);
	if (out) {
		png_memcpy(out, in, insize);
		out[insize] = 0;
	}
	return out;
}

/* dynamically allocates a new string with a copy of the null terminated input text */
static char *alloc_string(const char *in)
{
	return alloc_string_sized(in, png_strlen(in));
}
#endif /*PNG_COMPILE_ANCILLARY_CHUNKS*/
#endif /*PNG_COMPILE_PNG*/

/* ////////////////////////////////////////////////////////////////////////// */

#if defined(PNG_COMPILE_DECODER) || defined(PNG_COMPILE_PNG)
static u32 png_read32bitInt(const u8 *buffer)
{
	return (((u32)buffer[0] << 24u) | ((u32)buffer[1] << 16u) | ((u32)buffer[2] << 8u) |
		(u32)buffer[3]);
}
#endif /*defined(PNG_COMPILE_DECODER) || defined(PNG_COMPILE_PNG)*/

#if defined(PNG_COMPILE_PNG) || defined(PNG_COMPILE_ENCODER)
/*buffer must have at least 4 allocated bytes available*/
static void png_set32bitInt(u8 *buffer, u32 value)
{
	buffer[0] = (u8)((value >> 24) & 0xff);
	buffer[1] = (u8)((value >> 16) & 0xff);
	buffer[2] = (u8)((value >> 8) & 0xff);
	buffer[3] = (u8)((value)&0xff);
}
#endif /*defined(PNG_COMPILE_PNG) || defined(PNG_COMPILE_ENCODER)*/

/* ////////////////////////////////////////////////////////////////////////// */
/* / File IO                                                                / */
/* ////////////////////////////////////////////////////////////////////////// */

#ifdef PNG_COMPILE_DISK

/* returns negative value on error. This should be pure C compatible, so no fstat. */
static long png_filesize(const char *filename)
{
	struct stat s = { 0 };
	stat(filename, &s);
	return s.size;
}

/* load file into buffer that already has the correct allocated size. Returns error code.*/
static u32 png_buffer_file(u8 *out, u32 size, const char *filename)
{
	if (!out)
		return 78;

	u32 readsize = read(filename, out, 0, size);

	if (readsize != size)
		return 78;
	return 0;
}

u32 png_load_file(u8 **out, u32 *outsize, const char *filename)
{
	long size = png_filesize(filename);
	if (size < 0)
		return 78;
	*outsize = (u32)size;

	*out = (u8 *)png_malloc((u32)size);
	if (!(*out) && size > 0)
		return 83; /*the above malloc failed*/

	return png_buffer_file(*out, (u32)size, filename);
}

/*write given buffer to the file, overwriting the file, it doesn't append to it.*/
u32 png_save_file(const u8 *buffer, u32 buffersize, const char *filename)
{
	if (write(filename, buffer, 0, buffersize) <= 0)
		return 79;
	return 0;
}

#endif /*PNG_COMPILE_DISK*/

/* ////////////////////////////////////////////////////////////////////////// */
/* ////////////////////////////////////////////////////////////////////////// */
/* // End of common code and tools. Begin of Zlib related code.            // */
/* ////////////////////////////////////////////////////////////////////////// */
/* ////////////////////////////////////////////////////////////////////////// */

#ifdef PNG_COMPILE_ZLIB
#ifdef PNG_COMPILE_ENCODER

typedef struct {
	ucvector *data;
	u8 bp; /*ok to overflow, indicates bit pos inside byte*/
} pngBitWriter;

static void pngBitWriter_init(pngBitWriter *writer, ucvector *data)
{
	writer->data = data;
	writer->bp = 0;
}

/*TODO: this ignores potential out of memory errors*/
#define WRITEBIT(writer, bit)                                                                      \
	{                                                                                          \
		/* append new byte */                                                              \
		if (((writer->bp) & 7u) == 0) {                                                    \
			if (!ucvector_resize(writer->data, writer->data->size + 1))                \
				return;                                                            \
			writer->data->data[writer->data->size - 1] = 0;                            \
		}                                                                                  \
		(writer->data->data[writer->data->size - 1]) |= (bit << ((writer->bp) & 7u));      \
		++writer->bp;                                                                      \
	}

/* LSB of value is written first, and LSB of bytes is used first */
static void writeBits(pngBitWriter *writer, u32 value, u32 nbits)
{
	if (nbits == 1) { /* compiler should statically compile this case if nbits == 1 */
		WRITEBIT(writer, value);
	} else {
		/* TODO: increase output size only once here rather than in each WRITEBIT */
		u32 i;
		for (i = 0; i != nbits; ++i) {
			WRITEBIT(writer, (u8)((value >> i) & 1));
		}
	}
}

/* This one is to use for adding huffman symbol, the value bits are written MSB first */
static void writeBitsReversed(pngBitWriter *writer, u32 value, u32 nbits)
{
	u32 i;
	for (i = 0; i != nbits; ++i) {
		/* TODO: increase output size only once here rather than in each WRITEBIT */
		WRITEBIT(writer, (u8)((value >> (nbits - 1u - i)) & 1u));
	}
}
#endif /*PNG_COMPILE_ENCODER*/

#ifdef PNG_COMPILE_DECODER

typedef struct {
	const u8 *data;
	u32 size; /*size of data in bytes*/
	u32 bitsize; /*size of data in bits, end of valid bp values, should be 8*size*/
	u32 bp;
	u32 buffer; /*buffer for reading bits. NOTE: 'u32' must support at least 32 bits*/
} pngBitReader;

/* data size argument is in bytes. Returns error if size too large causing overflow */
static u32 pngBitReader_init(pngBitReader *reader, const u8 *data, u32 size)
{
	u32 temp;
	reader->data = data;
	reader->size = size;
	/* size in bits, return error if overflow (if u32 is 32 bit this supports up to 500MB)  */
	if (png_mulofl(size, 8u, &reader->bitsize))
		return 105;
	/*ensure incremented bp can be compared to bitsize without overflow even when it would be incremented 32 too much and
  trying to ensure 32 more bits*/
	if (png_addofl(reader->bitsize, 64u, &temp))
		return 105;
	reader->bp = 0;
	reader->buffer = 0;
	return 0; /*ok*/
}

/*
ensureBits functions:
Ensures the reader can at least read nbits bits in one or more readBits calls,
safely even if not enough bits are available.
Returns 1 if there are enough bits available, 0 if not.
*/

/*See ensureBits documentation above. This one ensures exactly 1 bit */
/*static u32 ensureBits1(pngBitReader* reader) {
  if(reader->bp >= reader->bitsize) return 0;
  reader->buffer = (u32)reader->data[reader->bp >> 3u] >> (reader->bp & 7u);
  return 1;
}*/

/*See ensureBits documentation above. This one ensures up to 9 bits */
static u32 ensureBits9(pngBitReader *reader, u32 nbits)
{
	u32 start = reader->bp >> 3u;
	u32 size = reader->size;
	if (start + 1u < size) {
		reader->buffer =
			(u32)reader->data[start + 0] | ((u32)reader->data[start + 1] << 8u);
		reader->buffer >>= (reader->bp & 7u);
		return 1;
	} else {
		reader->buffer = 0;
		if (start + 0u < size)
			reader->buffer |= reader->data[start + 0];
		reader->buffer >>= (reader->bp & 7u);
		return reader->bp + nbits <= reader->bitsize;
	}
}

/*See ensureBits documentation above. This one ensures up to 17 bits */
static u32 ensureBits17(pngBitReader *reader, u32 nbits)
{
	u32 start = reader->bp >> 3u;
	u32 size = reader->size;
	if (start + 2u < size) {
		reader->buffer = (u32)reader->data[start + 0] |
				 ((u32)reader->data[start + 1] << 8u) |
				 ((u32)reader->data[start + 2] << 16u);
		reader->buffer >>= (reader->bp & 7u);
		return 1;
	} else {
		reader->buffer = 0;
		if (start + 0u < size)
			reader->buffer |= reader->data[start + 0];
		if (start + 1u < size)
			reader->buffer |= ((u32)reader->data[start + 1] << 8u);
		reader->buffer >>= (reader->bp & 7u);
		return reader->bp + nbits <= reader->bitsize;
	}
}

/*See ensureBits documentation above. This one ensures up to 25 bits */
static PNG_INLINE u32 ensureBits25(pngBitReader *reader, u32 nbits)
{
	u32 start = reader->bp >> 3u;
	u32 size = reader->size;
	if (start + 3u < size) {
		reader->buffer = (u32)reader->data[start + 0] |
				 ((u32)reader->data[start + 1] << 8u) |
				 ((u32)reader->data[start + 2] << 16u) |
				 ((u32)reader->data[start + 3] << 24u);
		reader->buffer >>= (reader->bp & 7u);
		return 1;
	} else {
		reader->buffer = 0;
		if (start + 0u < size)
			reader->buffer |= reader->data[start + 0];
		if (start + 1u < size)
			reader->buffer |= ((u32)reader->data[start + 1] << 8u);
		if (start + 2u < size)
			reader->buffer |= ((u32)reader->data[start + 2] << 16u);
		reader->buffer >>= (reader->bp & 7u);
		return reader->bp + nbits <= reader->bitsize;
	}
}

/*See ensureBits documentation above. This one ensures up to 32 bits */
static PNG_INLINE u32 ensureBits32(pngBitReader *reader, u32 nbits)
{
	u32 start = reader->bp >> 3u;
	u32 size = reader->size;
	if (start + 4u < size) {
		reader->buffer = (u32)reader->data[start + 0] |
				 ((u32)reader->data[start + 1] << 8u) |
				 ((u32)reader->data[start + 2] << 16u) |
				 ((u32)reader->data[start + 3] << 24u);
		reader->buffer >>= (reader->bp & 7u);
		reader->buffer |=
			(((u32)reader->data[start + 4] << 24u) << (8u - (reader->bp & 7u)));
		return 1;
	} else {
		reader->buffer = 0;
		if (start + 0u < size)
			reader->buffer |= reader->data[start + 0];
		if (start + 1u < size)
			reader->buffer |= ((u32)reader->data[start + 1] << 8u);
		if (start + 2u < size)
			reader->buffer |= ((u32)reader->data[start + 2] << 16u);
		if (start + 3u < size)
			reader->buffer |= ((u32)reader->data[start + 3] << 24u);
		reader->buffer >>= (reader->bp & 7u);
		return reader->bp + nbits <= reader->bitsize;
	}
}

/* Get bits without advancing the bit pointer. Must have enough bits available with ensureBits. Max nbits is 31. */
static u32 peekBits(pngBitReader *reader, u32 nbits)
{
	/* The shift allows nbits to be only up to 31. */
	return reader->buffer & ((1u << nbits) - 1u);
}

/* Must have enough bits available with ensureBits */
static void advanceBits(pngBitReader *reader, u32 nbits)
{
	reader->buffer >>= nbits;
	reader->bp += nbits;
}

/* Must have enough bits available with ensureBits */
static u32 readBits(pngBitReader *reader, u32 nbits)
{
	u32 result = peekBits(reader, nbits);
	advanceBits(reader, nbits);
	return result;
}

/* Public for testing only. steps and result must have numsteps values. */
/*static u32 png_test_bitreader(const u8 *data, u32 size, u32 numsteps, const u32 *steps, u32 *result)
{
	u32 i;
	pngBitReader reader;
	u32 error = pngBitReader_init(&reader, data, size);
	if (error)
		return 0;
	for (i = 0; i < numsteps; i++) {
		u32 step = steps[i];
		u32 ok;
		if (step > 25)
			ok = ensureBits32(&reader, step);
		else if (step > 17)
			ok = ensureBits25(&reader, step);
		else if (step > 9)
			ok = ensureBits17(&reader, step);
		else
			ok = ensureBits9(&reader, step);
		if (!ok)
			return 0;
		result[i] = readBits(&reader, step);
	}
	return 1;
}*/
#endif /*PNG_COMPILE_DECODER*/

static u32 reverseBits(u32 bits, u32 num)
{
	/*TODO: implement faster lookup table based version when needed*/
	u32 i, result = 0;
	for (i = 0; i < num; i++)
		result |= ((bits >> (num - i - 1u)) & 1u) << i;
	return result;
}

/* ////////////////////////////////////////////////////////////////////////// */
/* / Deflate - Huffman                                                      / */
/* ////////////////////////////////////////////////////////////////////////// */

#define FIRST_LENGTH_CODE_INDEX 257
#define LAST_LENGTH_CODE_INDEX 285
/*256 literals, the end code, some length codes, and 2 unused codes*/
#define NUM_DEFLATE_CODE_SYMBOLS 288
/*the distance codes have their own symbols, 30 used, 2 unused*/
#define NUM_DISTANCE_SYMBOLS 32
/*the code length codes. 0-15: code lengths, 16: copy previous 3-6 times, 17: 3-10 zeros, 18: 11-138 zeros*/
#define NUM_CODE_LENGTH_CODES 19

/*the base lengths represented by codes 257-285*/
static const u32 LENGTHBASE[29] = { 3,	4,  5,	6,  7,	8,  9,	10, 11,	 13,  15,  17,	19,  23, 27,
				    31, 35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258 };

/*the extra bits used by codes 257-285 (added to base length)*/
static const u32 LENGTHEXTRA[29] = { 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2,
				     2, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0 };

/*the base backwards distances (the bits of distance codes appear after length codes and use their own huffman tree)*/
static const u32 DISTANCEBASE[30] = {
	1,   2,	  3,   4,   5,	 7,    9,    13,   17,	 25,   33,   49,   65,	  97,	 129,
	193, 257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145, 8193, 12289, 16385, 24577
};

/*the extra bits of backwards distances (added to base)*/
static const u32 DISTANCEEXTRA[30] = { 0, 0, 0, 0, 1, 1, 2, 2,	3,  3,	4,  4,	5,  5,	6,
				       6, 7, 7, 8, 8, 9, 9, 10, 10, 11, 11, 12, 12, 13, 13 };

/*the order in which "code length alphabet code lengths" are stored as specified by deflate, out of this the huffman
tree of the dynamic huffman tree lengths is generated*/
static const u32 CLCL_ORDER[NUM_CODE_LENGTH_CODES] = { 16, 17, 18, 0, 8,  7, 9,	 6, 10, 5,
						       11, 4,  12, 3, 13, 2, 14, 1, 15 };

/* ////////////////////////////////////////////////////////////////////////// */

/*
Huffman tree struct, containing multiple representations of the tree
*/
typedef struct HuffmanTree {
	u32 *codes; /*the huffman codes (bit patterns representing the symbols)*/
	u32 *lengths; /*the lengths of the huffman codes*/
	u32 maxbitlen; /*maximum number of bits a single code can get*/
	u32 numcodes; /*number of symbols in the alphabet = number of codes*/
	/* for reading only */
	u8 *table_len; /*length of symbol from lookup table, or max length if secondary lookup needed*/
	u16 *table_value; /*value of symbol from lookup table, or pointer to secondary table if needed*/
} HuffmanTree;

static void HuffmanTree_init(HuffmanTree *tree)
{
	tree->codes = 0;
	tree->lengths = 0;
	tree->table_len = 0;
	tree->table_value = 0;
}

static void HuffmanTree_cleanup(HuffmanTree *tree)
{
	png_free(tree->codes);
	png_free(tree->lengths);
	png_free(tree->table_len);
	png_free(tree->table_value);
}

/* amount of bits for first huffman table lookup (aka root bits), see HuffmanTree_makeTable and huffmanDecodeSymbol.*/
/* values 8u and 9u work the fastest */
#define FIRSTBITS 9u

/* a symbol value too big to represent any valid symbol, to indicate reading disallowed huffman bits combination,
which is possible in case of only 0 or 1 present symbols. */
#define INVALIDSYMBOL 65535u

/* make table for huffman decoding */
static u32 HuffmanTree_makeTable(HuffmanTree *tree)
{
	static const u32 headsize = 1u << FIRSTBITS; /*size of the first table*/
	static const u32 mask = (1u << FIRSTBITS) /*headsize*/ - 1u;
	u32 i, numpresent, pointer, size; /*total table size*/
	u32 *maxlens = (u32 *)png_malloc(headsize * sizeof(u32));
	if (!maxlens)
		return 83; /*alloc fail*/

	/* compute maxlens: max total bit length of symbols sharing prefix in the first table*/
	png_memset(maxlens, 0, headsize * sizeof(*maxlens));
	for (i = 0; i < tree->numcodes; i++) {
		u32 symbol = tree->codes[i];
		u32 l = tree->lengths[i];
		u32 index;
		if (l <= FIRSTBITS)
			continue; /*symbols that fit in first table don't increase secondary table size*/
		/*get the FIRSTBITS MSBs, the MSBs of the symbol are encoded first. See later comment about the reversing*/
		index = reverseBits(symbol >> (l - FIRSTBITS), FIRSTBITS);
		maxlens[index] = PNG_MAX(maxlens[index], l);
	}
	/* compute total table size: size of first table plus all secondary tables for symbols longer than FIRSTBITS */
	size = headsize;
	for (i = 0; i < headsize; ++i) {
		u32 l = maxlens[i];
		if (l > FIRSTBITS)
			size += (1u << (l - FIRSTBITS));
	}
	tree->table_len = (u8 *)png_malloc(size * sizeof(*tree->table_len));
	tree->table_value = (u16 *)png_malloc(size * sizeof(*tree->table_value));
	if (!tree->table_len || !tree->table_value) {
		png_free(maxlens);
		/* freeing tree->table values is done at a higher scope */
		return 83; /*alloc fail*/
	}
	/*initialize with an invalid length to indicate unused entries*/
	for (i = 0; i < size; ++i)
		tree->table_len[i] = 16;

	/*fill in the first table for long symbols: max prefix size and pointer to secondary tables*/
	pointer = headsize;
	for (i = 0; i < headsize; ++i) {
		u32 l = maxlens[i];
		if (l <= FIRSTBITS)
			continue;
		tree->table_len[i] = l;
		tree->table_value[i] = pointer;
		pointer += (1u << (l - FIRSTBITS));
	}
	png_free(maxlens);

	/*fill in the first table for short symbols, or secondary table for long symbols*/
	numpresent = 0;
	for (i = 0; i < tree->numcodes; ++i) {
		u32 l = tree->lengths[i];
		u32 symbol = tree->codes[i]; /*the huffman bit pattern. i itself is the value.*/
		/*reverse bits, because the huffman bits are given in MSB first order but the bit reader reads LSB first*/
		u32 reverse = reverseBits(symbol, l);
		if (l == 0)
			continue;
		numpresent++;

		if (l <= FIRSTBITS) {
			/*short symbol, fully in first table, replicated num times if l < FIRSTBITS*/
			u32 num = 1u << (FIRSTBITS - l);
			u32 j;
			for (j = 0; j < num; ++j) {
				/*bit reader will read the l bits of symbol first, the remaining FIRSTBITS - l bits go to the MSB's*/
				u32 index = reverse | (j << l);
				if (tree->table_len[index] != 16)
					return 55; /*invalid tree: long symbol shares prefix with short symbol*/
				tree->table_len[index] = l;
				tree->table_value[index] = i;
			}
		} else {
			/*long symbol, shares prefix with other long symbols in first lookup table, needs second lookup*/
			/*the FIRSTBITS MSBs of the symbol are the first table index*/
			u32 index = reverse & mask;
			u32 maxlen = tree->table_len[index];
			/*log2 of secondary table length, should be >= l - FIRSTBITS*/
			u32 tablelen = maxlen - FIRSTBITS;
			u32 start = tree->table_value[index]; /*starting index in secondary table*/
			u32 num =
				1u
				<< (tablelen -
				    (l -
				     FIRSTBITS)); /*amount of entries of this symbol in secondary table*/
			u32 j;
			if (maxlen < l)
				return 55; /*invalid tree: long symbol shares prefix with short symbol*/
			for (j = 0; j < num; ++j) {
				u32 reverse2 = reverse >> FIRSTBITS; /* l - FIRSTBITS bits */
				u32 index2 = start + (reverse2 | (j << (l - FIRSTBITS)));
				tree->table_len[index2] = l;
				tree->table_value[index2] = i;
			}
		}
	}

	if (numpresent < 2) {
		/* In case of exactly 1 symbol, in theory the huffman symbol needs 0 bits,
    but deflate uses 1 bit instead. In case of 0 symbols, no symbols can
    appear at all, but such huffman tree could still exist (e.g. if distance
    codes are never used). In both cases, not all symbols of the table will be
    filled in. Fill them in with an invalid symbol value so returning them from
    huffmanDecodeSymbol will cause error. */
		for (i = 0; i < size; ++i) {
			if (tree->table_len[i] == 16) {
				/* As length, use a value smaller than FIRSTBITS for the head table,
        and a value larger than FIRSTBITS for the secondary table, to ensure
        valid behavior for advanceBits when reading this symbol. */
				tree->table_len[i] = (i < headsize) ? 1 : (FIRSTBITS + 1);
				tree->table_value[i] = INVALIDSYMBOL;
			}
		}
	} else {
		/* A good huffman tree has N * 2 - 1 nodes, of which N - 1 are internal nodes.
    If that is not the case (due to too long length codes), the table will not
    have been fully used, and this is an error (not all bit combinations can be
    decoded): an oversubscribed huffman tree, indicated by error 55. */
		for (i = 0; i < size; ++i) {
			if (tree->table_len[i] == 16)
				return 55;
		}
	}

	return 0;
}

/*
Second step for the ...makeFromLengths and ...makeFromFrequencies functions.
numcodes, lengths and maxbitlen must already be filled in correctly. return
value is error.
*/
static u32 HuffmanTree_makeFromLengths2(HuffmanTree *tree)
{
	u32 *blcount;
	u32 *nextcode;
	u32 error = 0;
	u32 bits, n;

	tree->codes = (u32 *)png_malloc(tree->numcodes * sizeof(u32));
	blcount = (u32 *)png_malloc((tree->maxbitlen + 1) * sizeof(u32));
	nextcode = (u32 *)png_malloc((tree->maxbitlen + 1) * sizeof(u32));
	if (!tree->codes || !blcount || !nextcode)
		error = 83; /*alloc fail*/

	if (!error) {
		for (n = 0; n != tree->maxbitlen + 1; n++)
			blcount[n] = nextcode[n] = 0;
		/*step 1: count number of instances of each code length*/
		for (bits = 0; bits != tree->numcodes; ++bits)
			++blcount[tree->lengths[bits]];
		/*step 2: generate the nextcode values*/
		for (bits = 1; bits <= tree->maxbitlen; ++bits) {
			nextcode[bits] = (nextcode[bits - 1] + blcount[bits - 1]) << 1u;
		}
		/*step 3: generate all the codes*/
		for (n = 0; n != tree->numcodes; ++n) {
			if (tree->lengths[n] != 0) {
				tree->codes[n] = nextcode[tree->lengths[n]]++;
				/*remove superfluous bits from the code*/
				tree->codes[n] &= ((1u << tree->lengths[n]) - 1u);
			}
		}
	}

	png_free(blcount);
	png_free(nextcode);

	if (!error)
		error = HuffmanTree_makeTable(tree);
	return error;
}

/*
given the code lengths (as stored in the PNG file), generate the tree as defined
by Deflate. maxbitlen is the maximum bits that a code in the tree can have.
return value is error.
*/
static u32 HuffmanTree_makeFromLengths(HuffmanTree *tree, const u32 *bitlen, u32 numcodes,
				       u32 maxbitlen)
{
	u32 i;
	tree->lengths = (u32 *)png_malloc(numcodes * sizeof(u32));
	if (!tree->lengths)
		return 83; /*alloc fail*/
	for (i = 0; i != numcodes; ++i)
		tree->lengths[i] = bitlen[i];
	tree->numcodes = (u32)numcodes; /*number of symbols*/
	tree->maxbitlen = maxbitlen;
	return HuffmanTree_makeFromLengths2(tree);
}

#ifdef PNG_COMPILE_ENCODER

/*BPM: Boundary Package Merge, see "A Fast and Space-Economical Algorithm for Length-Limited Coding",
Jyrki Katajainen, Alistair Moffat, Andrew Turpin, 1995.*/

/*chain node for boundary package merge*/
typedef struct BPMNode {
	int weight; /*the sum of all weights in this chain*/
	u32 index; /*index of this leaf node (called "count" in the paper)*/
	struct BPMNode *tail; /*the next nodes in this chain (null if last)*/
	int in_use;
} BPMNode;

/*lists of chains*/
typedef struct BPMLists {
	/*memory pool*/
	u32 memsize;
	BPMNode *memory;
	u32 numfree;
	u32 nextfree;
	BPMNode **freelist;
	/*two heads of lookahead chains per list*/
	u32 listsize;
	BPMNode **chains0;
	BPMNode **chains1;
} BPMLists;

/*creates a new chain node with the given parameters, from the memory in the lists */
static BPMNode *bpmnode_create(BPMLists *lists, int weight, u32 index, BPMNode *tail)
{
	u32 i;
	BPMNode *result;

	/*memory full, so garbage collect*/
	if (lists->nextfree >= lists->numfree) {
		/*mark only those that are in use*/
		for (i = 0; i != lists->memsize; ++i)
			lists->memory[i].in_use = 0;
		for (i = 0; i != lists->listsize; ++i) {
			BPMNode *node;
			for (node = lists->chains0[i]; node != 0; node = node->tail)
				node->in_use = 1;
			for (node = lists->chains1[i]; node != 0; node = node->tail)
				node->in_use = 1;
		}
		/*collect those that are free*/
		lists->numfree = 0;
		for (i = 0; i != lists->memsize; ++i) {
			if (!lists->memory[i].in_use)
				lists->freelist[lists->numfree++] = &lists->memory[i];
		}
		lists->nextfree = 0;
	}

	result = lists->freelist[lists->nextfree++];
	result->weight = weight;
	result->index = index;
	result->tail = tail;
	return result;
}

/*sort the leaves with stable mergesort*/
static void bpmnode_sort(BPMNode *leaves, u32 num)
{
	BPMNode *mem = (BPMNode *)png_malloc(sizeof(*leaves) * num);
	u32 width, counter = 0;
	for (width = 1; width < num; width *= 2) {
		BPMNode *a = (counter & 1) ? mem : leaves;
		BPMNode *b = (counter & 1) ? leaves : mem;
		u32 p;
		for (p = 0; p < num; p += 2 * width) {
			u32 q = (p + width > num) ? num : (p + width);
			u32 r = (p + 2 * width > num) ? num : (p + 2 * width);
			u32 i = p, j = q, k;
			for (k = p; k < r; k++) {
				if (i < q && (j >= r || a[i].weight <= a[j].weight))
					b[k] = a[i++];
				else
					b[k] = a[j++];
			}
		}
		counter++;
	}
	if (counter & 1)
		png_memcpy(leaves, mem, sizeof(*leaves) * num);
	png_free(mem);
}

/*Boundary Package Merge step, numpresent is the amount of leaves, and c is the current chain.*/
static void boundaryPM(BPMLists *lists, BPMNode *leaves, u32 numpresent, int c, int num)
{
	u32 lastindex = lists->chains1[c]->index;

	if (c == 0) {
		if (lastindex >= numpresent)
			return;
		lists->chains0[c] = lists->chains1[c];
		lists->chains1[c] =
			bpmnode_create(lists, leaves[lastindex].weight, lastindex + 1, 0);
	} else {
		/*sum of the weights of the head nodes of the previous lookahead chains.*/
		int sum = lists->chains0[c - 1]->weight + lists->chains1[c - 1]->weight;
		lists->chains0[c] = lists->chains1[c];
		if (lastindex < numpresent && sum > leaves[lastindex].weight) {
			lists->chains1[c] = bpmnode_create(lists, leaves[lastindex].weight,
							   lastindex + 1, lists->chains1[c]->tail);
			return;
		}
		lists->chains1[c] = bpmnode_create(lists, sum, lastindex, lists->chains1[c - 1]);
		/*in the end we are only interested in the chain of the last list, so no
    need to recurse if we're at the last one (this gives measurable speedup)*/
		if (num + 1 < (int)(2 * numpresent - 2)) {
			boundaryPM(lists, leaves, numpresent, c - 1, num);
			boundaryPM(lists, leaves, numpresent, c - 1, num);
		}
	}
}

u32 png_huffman_code_lengths(u32 *lengths, const u32 *frequencies, u32 numcodes, u32 maxbitlen)
{
	u32 error = 0;
	u32 i;
	u32 numpresent = 0; /*number of symbols with non-zero frequency*/
	BPMNode *leaves; /*the symbols, only those with > 0 frequency*/

	if (numcodes == 0)
		return 80; /*error: a tree of 0 symbols is not supposed to be made*/
	if ((1u << maxbitlen) < (u32)numcodes)
		return 80; /*error: represent all symbols*/

	leaves = (BPMNode *)png_malloc(numcodes * sizeof(*leaves));
	if (!leaves)
		return 83; /*alloc fail*/

	for (i = 0; i != numcodes; ++i) {
		if (frequencies[i] > 0) {
			leaves[numpresent].weight = (int)frequencies[i];
			leaves[numpresent].index = i;
			++numpresent;
		}
	}

	png_memset(lengths, 0, numcodes * sizeof(*lengths));

	/*ensure at least two present symbols. There should be at least one symbol
  according to RFC 1951 section 3.2.7. Some decoders incorrectly require two. To
  make these work as well ensure there are at least two symbols. The
  Package-Merge code below also doesn't work correctly if there's only one
  symbol, it'd give it the theoretical 0 bits but in practice zlib wants 1 bit*/
	if (numpresent == 0) {
		lengths[0] = lengths[1] =
			1; /*note that for RFC 1951 section 3.2.7, only lengths[0] = 1 is needed*/
	} else if (numpresent == 1) {
		lengths[leaves[0].index] = 1;
		lengths[leaves[0].index == 0 ? 1 : 0] = 1;
	} else {
		BPMLists lists;
		BPMNode *node;

		bpmnode_sort(leaves, numpresent);

		lists.listsize = maxbitlen;
		lists.memsize = 2 * maxbitlen * (maxbitlen + 1);
		lists.nextfree = 0;
		lists.numfree = lists.memsize;
		lists.memory = (BPMNode *)png_malloc(lists.memsize * sizeof(*lists.memory));
		lists.freelist = (BPMNode **)png_malloc(lists.memsize * sizeof(BPMNode *));
		lists.chains0 = (BPMNode **)png_malloc(lists.listsize * sizeof(BPMNode *));
		lists.chains1 = (BPMNode **)png_malloc(lists.listsize * sizeof(BPMNode *));
		if (!lists.memory || !lists.freelist || !lists.chains0 || !lists.chains1)
			error = 83; /*alloc fail*/

		if (!error) {
			for (i = 0; i != lists.memsize; ++i)
				lists.freelist[i] = &lists.memory[i];

			bpmnode_create(&lists, leaves[0].weight, 1, 0);
			bpmnode_create(&lists, leaves[1].weight, 2, 0);

			for (i = 0; i != lists.listsize; ++i) {
				lists.chains0[i] = &lists.memory[0];
				lists.chains1[i] = &lists.memory[1];
			}

			/*each boundaryPM call adds one chain to the last list, and we need 2 * numpresent - 2 chains.*/
			for (i = 2; i != 2 * numpresent - 2; ++i)
				boundaryPM(&lists, leaves, numpresent, (int)maxbitlen - 1, (int)i);

			for (node = lists.chains1[maxbitlen - 1]; node; node = node->tail) {
				for (i = 0; i != node->index; ++i)
					++lengths[leaves[i].index];
			}
		}

		png_free(lists.memory);
		png_free(lists.freelist);
		png_free(lists.chains0);
		png_free(lists.chains1);
	}

	png_free(leaves);
	return error;
}

/*Create the Huffman tree given the symbol frequencies*/
static u32 HuffmanTree_makeFromFrequencies(HuffmanTree *tree, const u32 *frequencies, u32 mincodes,
					   u32 numcodes, u32 maxbitlen)
{
	u32 error = 0;
	while (!frequencies[numcodes - 1] && numcodes > mincodes)
		--numcodes; /*trim zeroes*/
	tree->lengths = (u32 *)png_malloc(numcodes * sizeof(u32));
	if (!tree->lengths)
		return 83; /*alloc fail*/
	tree->maxbitlen = maxbitlen;
	tree->numcodes = (u32)numcodes; /*number of symbols*/

	error = png_huffman_code_lengths(tree->lengths, frequencies, numcodes, maxbitlen);
	if (!error)
		error = HuffmanTree_makeFromLengths2(tree);
	return error;
}
#endif /*PNG_COMPILE_ENCODER*/

/*get the literal and length code tree of a deflated block with fixed tree, as per the deflate specification*/
static u32 generateFixedLitLenTree(HuffmanTree *tree)
{
	u32 i, error = 0;
	u32 *bitlen = (u32 *)png_malloc(NUM_DEFLATE_CODE_SYMBOLS * sizeof(u32));
	if (!bitlen)
		return 83; /*alloc fail*/

	/*288 possible codes: 0-255=literals, 256=endcode, 257-285=lengthcodes, 286-287=unused*/
	for (i = 0; i <= 143; ++i)
		bitlen[i] = 8;
	for (i = 144; i <= 255; ++i)
		bitlen[i] = 9;
	for (i = 256; i <= 279; ++i)
		bitlen[i] = 7;
	for (i = 280; i <= 287; ++i)
		bitlen[i] = 8;

	error = HuffmanTree_makeFromLengths(tree, bitlen, NUM_DEFLATE_CODE_SYMBOLS, 15);

	png_free(bitlen);
	return error;
}

/*get the distance code tree of a deflated block with fixed tree, as specified in the deflate specification*/
static u32 generateFixedDistanceTree(HuffmanTree *tree)
{
	u32 i, error = 0;
	u32 *bitlen = (u32 *)png_malloc(NUM_DISTANCE_SYMBOLS * sizeof(u32));
	if (!bitlen)
		return 83; /*alloc fail*/

	/*there are 32 distance codes, but 30-31 are unused*/
	for (i = 0; i != NUM_DISTANCE_SYMBOLS; ++i)
		bitlen[i] = 5;
	error = HuffmanTree_makeFromLengths(tree, bitlen, NUM_DISTANCE_SYMBOLS, 15);

	png_free(bitlen);
	return error;
}

#ifdef PNG_COMPILE_DECODER

/*
returns the code. The bit reader must already have been ensured at least 15 bits
*/
static u32 huffmanDecodeSymbol(pngBitReader *reader, const HuffmanTree *codetree)
{
	u16 code = peekBits(reader, FIRSTBITS);
	u16 l = codetree->table_len[code];
	u16 value = codetree->table_value[code];
	if (l <= FIRSTBITS) {
		advanceBits(reader, l);
		return value;
	} else {
		u32 index2;
		advanceBits(reader, FIRSTBITS);
		index2 = value + peekBits(reader, l - FIRSTBITS);
		advanceBits(reader, codetree->table_len[index2] - FIRSTBITS);
		return codetree->table_value[index2];
	}
}
#endif /*PNG_COMPILE_DECODER*/

#ifdef PNG_COMPILE_DECODER

/* ////////////////////////////////////////////////////////////////////////// */
/* / Inflator (Decompressor)                                                / */
/* ////////////////////////////////////////////////////////////////////////// */

/*get the tree of a deflated block with fixed tree, as specified in the deflate specification
Returns error code.*/
static u32 getTreeInflateFixed(HuffmanTree *tree_ll, HuffmanTree *tree_d)
{
	u32 error = generateFixedLitLenTree(tree_ll);
	if (error)
		return error;
	return generateFixedDistanceTree(tree_d);
}

/*get the tree of a deflated block with dynamic tree, the tree itself is also Huffman compressed with a known tree*/
static u32 getTreeInflateDynamic(HuffmanTree *tree_ll, HuffmanTree *tree_d, pngBitReader *reader)
{
	/*make sure that length values that aren't filled in will be 0, or a wrong tree will be generated*/
	u32 error = 0;
	u32 n, HLIT, HDIST, HCLEN, i;

	/*see comments in deflateDynamic for explanation of the context and these variables, it is analogous*/
	u32 *bitlen_ll = 0; /*lit,len code lengths*/
	u32 *bitlen_d = 0; /*dist code lengths*/
	/*code length code lengths ("clcl"), the bit lengths of the huffman tree used to compress bitlen_ll and bitlen_d*/
	u32 *bitlen_cl = 0;
	HuffmanTree
		tree_cl; /*the code tree for code length codes (the huffman tree for compressed huffman trees)*/

	if (!ensureBits17(reader, 14))
		return 49; /*error: the bit pointer is or will go past the memory*/

	/*number of literal/length codes + 257. Unlike the spec, the value 257 is added to it here already*/
	HLIT = readBits(reader, 5) + 257;
	/*number of distance codes. Unlike the spec, the value 1 is added to it here already*/
	HDIST = readBits(reader, 5) + 1;
	/*number of code length codes. Unlike the spec, the value 4 is added to it here already*/
	HCLEN = readBits(reader, 4) + 4;

	bitlen_cl = (u32 *)png_malloc(NUM_CODE_LENGTH_CODES * sizeof(u32));
	if (!bitlen_cl)
		return 83 /*alloc fail*/;

	HuffmanTree_init(&tree_cl);

	while (!error) {
		/*read the code length codes out of 3 * (amount of code length codes) bits*/
		if (png_gtofl(reader->bp, HCLEN * 3, reader->bitsize)) {
			ERROR_BREAK(50); /*error: the bit pointer is or will go past the memory*/
		}
		for (i = 0; i != HCLEN; ++i) {
			ensureBits9(reader, 3); /*out of bounds already checked above */
			bitlen_cl[CLCL_ORDER[i]] = readBits(reader, 3);
		}
		for (i = HCLEN; i != NUM_CODE_LENGTH_CODES; ++i) {
			bitlen_cl[CLCL_ORDER[i]] = 0;
		}

		error = HuffmanTree_makeFromLengths(&tree_cl, bitlen_cl, NUM_CODE_LENGTH_CODES, 7);
		if (error)
			break;

		/*now we can use this tree to read the lengths for the tree that this function will return*/
		bitlen_ll = (u32 *)png_malloc(NUM_DEFLATE_CODE_SYMBOLS * sizeof(u32));
		bitlen_d = (u32 *)png_malloc(NUM_DISTANCE_SYMBOLS * sizeof(u32));
		if (!bitlen_ll || !bitlen_d)
			ERROR_BREAK(83 /*alloc fail*/);
		png_memset(bitlen_ll, 0, NUM_DEFLATE_CODE_SYMBOLS * sizeof(*bitlen_ll));
		png_memset(bitlen_d, 0, NUM_DISTANCE_SYMBOLS * sizeof(*bitlen_d));

		/*i is the current symbol we're reading in the part that contains the code lengths of lit/len and dist codes*/
		i = 0;
		while (i < HLIT + HDIST) {
			u32 code;
			ensureBits25(
				reader,
				22); /* up to 15 bits for huffman code, up to 7 extra bits below*/
			code = huffmanDecodeSymbol(reader, &tree_cl);
			if (code <= 15) /*a length code*/ {
				if (i < HLIT)
					bitlen_ll[i] = code;
				else
					bitlen_d[i - HLIT] = code;
				++i;
			} else if (code == 16) /*repeat previous*/ {
				u32 replength =
					3; /*read in the 2 bits that indicate repeat length (3-6)*/
				u32 value; /*set value to the previous code*/

				if (i == 0)
					ERROR_BREAK(54); /*can't repeat previous if i is 0*/

				replength += readBits(reader, 2);

				if (i < HLIT + 1)
					value = bitlen_ll[i - 1];
				else
					value = bitlen_d[i - HLIT - 1];
				/*repeat this value in the next lengths*/
				for (n = 0; n < replength; ++n) {
					if (i >= HLIT + HDIST)
						ERROR_BREAK(
							13); /*error: i is larger than the amount of codes*/
					if (i < HLIT)
						bitlen_ll[i] = value;
					else
						bitlen_d[i - HLIT] = value;
					++i;
				}
			} else if (code == 17) /*repeat "0" 3-10 times*/ {
				u32 replength = 3; /*read in the bits that indicate repeat length*/
				replength += readBits(reader, 3);

				/*repeat this value in the next lengths*/
				for (n = 0; n < replength; ++n) {
					if (i >= HLIT + HDIST)
						ERROR_BREAK(
							14); /*error: i is larger than the amount of codes*/

					if (i < HLIT)
						bitlen_ll[i] = 0;
					else
						bitlen_d[i - HLIT] = 0;
					++i;
				}
			} else if (code == 18) /*repeat "0" 11-138 times*/ {
				u32 replength = 11; /*read in the bits that indicate repeat length*/
				replength += readBits(reader, 7);

				/*repeat this value in the next lengths*/
				for (n = 0; n < replength; ++n) {
					if (i >= HLIT + HDIST)
						ERROR_BREAK(
							15); /*error: i is larger than the amount of codes*/

					if (i < HLIT)
						bitlen_ll[i] = 0;
					else
						bitlen_d[i - HLIT] = 0;
					++i;
				}
			} else /*if(code == INVALIDSYMBOL)*/ {
				ERROR_BREAK(16); /*error: tried to read disallowed huffman symbol*/
			}
			/*check if any of the ensureBits above went out of bounds*/
			if (reader->bp > reader->bitsize) {
				/*return error code 10 or 11 depending on the situation that happened in huffmanDecodeSymbol
        (10=no endcode, 11=wrong jump outside of tree)*/
				/* TODO: revise error codes 10,11,50: the above comment is no longer valid */
				ERROR_BREAK(50); /*error, bit pointer jumps past memory*/
			}
		}
		if (error)
			break;

		if (bitlen_ll[256] == 0)
			ERROR_BREAK(64); /*the length of the end code 256 must be larger than 0*/

		/*now we've finally got HLIT and HDIST, so generate the code trees, and the function is done*/
		error = HuffmanTree_makeFromLengths(tree_ll, bitlen_ll, NUM_DEFLATE_CODE_SYMBOLS,
						    15);
		if (error)
			break;
		error = HuffmanTree_makeFromLengths(tree_d, bitlen_d, NUM_DISTANCE_SYMBOLS, 15);

		break; /*end of error-while*/
	}

	png_free(bitlen_cl);
	png_free(bitlen_ll);
	png_free(bitlen_d);
	HuffmanTree_cleanup(&tree_cl);

	return error;
}

/*inflate a block with dynamic of fixed Huffman tree. btype must be 1 or 2.*/
static u32 inflateHuffmanBlock(ucvector *out, pngBitReader *reader, u32 btype, u32 max_output_size)
{
	u32 error = 0;
	HuffmanTree tree_ll; /*the huffman tree for literal and length codes*/
	HuffmanTree tree_d; /*the huffman tree for distance codes*/

	HuffmanTree_init(&tree_ll);
	HuffmanTree_init(&tree_d);

	if (btype == 1)
		error = getTreeInflateFixed(&tree_ll, &tree_d);
	else /*if(btype == 2)*/
		error = getTreeInflateDynamic(&tree_ll, &tree_d, reader);

	while (!error) /*decode all symbols until end reached, breaks at end code*/ {
		/*code_ll is literal, length or end code*/
		u32 code_ll;
		ensureBits25(
			reader,
			20); /* up to 15 for the huffman symbol, up to 5 for the length extra bits */
		code_ll = huffmanDecodeSymbol(reader, &tree_ll);
		if (code_ll <= 255) /*literal symbol*/ {
			if (!ucvector_resize(out, out->size + 1))
				ERROR_BREAK(83 /*alloc fail*/);
			out->data[out->size - 1] = (u8)code_ll;
		} else if (code_ll >= FIRST_LENGTH_CODE_INDEX &&
			   code_ll <= LAST_LENGTH_CODE_INDEX) /*length code*/ {
			u32 code_d, distance;
			u32 numextrabits_l, numextrabits_d; /*extra bits for length and distance*/
			u32 start, backward, length;

			/*part 1: get length base*/
			length = LENGTHBASE[code_ll - FIRST_LENGTH_CODE_INDEX];

			/*part 2: get extra bits and add the value of that to length*/
			numextrabits_l = LENGTHEXTRA[code_ll - FIRST_LENGTH_CODE_INDEX];
			if (numextrabits_l != 0) {
				/* bits already ensured above */
				length += readBits(reader, numextrabits_l);
			}

			/*part 3: get distance code*/
			ensureBits32(
				reader,
				28); /* up to 15 for the huffman symbol, up to 13 for the extra bits */
			code_d = huffmanDecodeSymbol(reader, &tree_d);
			if (code_d > 29) {
				if (code_d <= 31) {
					ERROR_BREAK(
						18); /*error: invalid distance code (30-31 are never used)*/
				} else /* if(code_d == INVALIDSYMBOL) */ {
					ERROR_BREAK(
						16); /*error: tried to read disallowed huffman symbol*/
				}
			}
			distance = DISTANCEBASE[code_d];

			/*part 4: get extra bits from distance*/
			numextrabits_d = DISTANCEEXTRA[code_d];
			if (numextrabits_d != 0) {
				/* bits already ensured above */
				distance += readBits(reader, numextrabits_d);
			}

			/*part 5: fill in all the out[n] values based on the length and dist*/
			start = out->size;
			if (distance > start)
				ERROR_BREAK(52); /*too long backward distance*/
			backward = start - distance;

			if (!ucvector_resize(out, out->size + length))
				ERROR_BREAK(83 /*alloc fail*/);
			if (distance < length) {
				u32 forward;
				png_memcpy(out->data + start, out->data + backward, distance);
				start += distance;
				for (forward = distance; forward < length; ++forward) {
					out->data[start++] = out->data[backward++];
				}
			} else {
				png_memcpy(out->data + start, out->data + backward, length);
			}
		} else if (code_ll == 256) {
			break; /*end code, break the loop*/
		} else /*if(code_ll == INVALIDSYMBOL)*/ {
			ERROR_BREAK(16); /*error: tried to read disallowed huffman symbol*/
		}
		/*check if any of the ensureBits above went out of bounds*/
		if (reader->bp > reader->bitsize) {
			/*return error code 10 or 11 depending on the situation that happened in huffmanDecodeSymbol
      (10=no endcode, 11=wrong jump outside of tree)*/
			/* TODO: revise error codes 10,11,50: the above comment is no longer valid */
			ERROR_BREAK(51); /*error, bit pointer jumps past memory*/
		}
		if (max_output_size && out->size > max_output_size) {
			ERROR_BREAK(109); /*error, larger than max size*/
		}
	}

	HuffmanTree_cleanup(&tree_ll);
	HuffmanTree_cleanup(&tree_d);

	return error;
}

static u32 inflateNoCompression(ucvector *out, pngBitReader *reader,
				const pngDecompressSettings *settings)
{
	u32 bytepos;
	u32 size = reader->size;
	u32 LEN, NLEN, error = 0;

	/*go to first boundary of byte*/
	bytepos = (reader->bp + 7u) >> 3u;

	/*read LEN (2 bytes) and NLEN (2 bytes)*/
	if (bytepos + 4 >= size)
		return 52; /*error, bit pointer will jump past memory*/
	LEN = (u32)reader->data[bytepos] + ((u32)reader->data[bytepos + 1] << 8u);
	bytepos += 2;
	NLEN = (u32)reader->data[bytepos] + ((u32)reader->data[bytepos + 1] << 8u);
	bytepos += 2;

	/*check if 16-bit NLEN is really the one's complement of LEN*/
	if (!settings->ignore_nlen && LEN + NLEN != 65535) {
		return 21; /*error: NLEN is not one's complement of LEN*/
	}

	if (!ucvector_resize(out, out->size + LEN))
		return 83; /*alloc fail*/

	/*read the literal data: LEN bytes are now stored in the out buffer*/
	if (bytepos + LEN > size)
		return 23; /*error: reading outside of in buffer*/

	png_memcpy(out->data + out->size - LEN, reader->data + bytepos, LEN);
	bytepos += LEN;

	reader->bp = bytepos << 3u;

	return error;
}

static u32 png_inflatev(ucvector *out, const u8 *in, u32 insize,
			const pngDecompressSettings *settings)
{
	u32 BFINAL = 0;
	pngBitReader reader;
	u32 error = pngBitReader_init(&reader, in, insize);

	if (error)
		return error;

	while (!BFINAL) {
		u32 BTYPE;
		if (!ensureBits9(&reader, 3))
			return 52; /*error, bit pointer will jump past memory*/
		BFINAL = readBits(&reader, 1);
		BTYPE = readBits(&reader, 2);

		if (BTYPE == 3)
			return 20; /*error: invalid BTYPE*/
		else if (BTYPE == 0)
			error = inflateNoCompression(out, &reader, settings); /*no compression*/
		else
			error = inflateHuffmanBlock(
				out, &reader, BTYPE,
				settings->max_output_size); /*compression, BTYPE 01 or 10*/
		if (!error && settings->max_output_size && out->size > settings->max_output_size)
			error = 109;
		if (error)
			break;
	}

	return error;
}

u32 png_inflate(u8 **out, u32 *outsize, const u8 *in, u32 insize,
		const pngDecompressSettings *settings)
{
	ucvector v = ucvector_init(*out, *outsize);
	u32 error = png_inflatev(&v, in, insize, settings);
	*out = v.data;
	*outsize = v.size;
	return error;
}

static u32 inflatev(ucvector *out, const u8 *in, u32 insize, const pngDecompressSettings *settings)
{
	if (settings->custom_inflate) {
		u32 error = settings->custom_inflate(&out->data, &out->size, in, insize, settings);
		out->allocsize = out->size;
		if (error) {
			/*the custom inflate is allowed to have its own error codes, however, we translate it to code 110*/
			error = 110;
			/*if there's a max output size, and the custom zlib returned error, then indicate that error instead*/
			if (settings->max_output_size && out->size > settings->max_output_size)
				error = 109;
		}
		return error;
	} else {
		return png_inflatev(out, in, insize, settings);
	}
}

#endif /*PNG_COMPILE_DECODER*/

#ifdef PNG_COMPILE_ENCODER

/* ////////////////////////////////////////////////////////////////////////// */
/* / Deflator (Compressor)                                                  / */
/* ////////////////////////////////////////////////////////////////////////// */

static const u32 MAX_SUPPORTED_DEFLATE_LENGTH = 258;

/*search the index in the array, that has the largest value smaller than or equal to the given value,
given array must be sorted (if no value is smaller, it returns the size of the given array)*/
static u32 searchCodeIndex(const u32 *array, u32 array_size, u32 value)
{
	/*binary search (only small gain over linear). TODO: use CPU log2 instruction for getting symbols instead*/
	u32 left = 1;
	u32 right = array_size - 1;

	while (left <= right) {
		u32 mid = (left + right) >> 1;
		if (array[mid] >= value)
			right = mid - 1;
		else
			left = mid + 1;
	}
	if (left >= array_size || array[left] > value)
		left--;
	return left;
}

static void addLengthDistance(uivector *values, u32 length, u32 distance)
{
	/*values in encoded vector are those used by deflate:
  0-255: literal bytes
  256: end
  257-285: length/distance pair (length code, followed by extra length bits, distance code, extra distance bits)
  286-287: invalid*/

	u32 length_code = (u32)searchCodeIndex(LENGTHBASE, 29, length);
	u32 extra_length = (u32)(length - LENGTHBASE[length_code]);
	u32 dist_code = (u32)searchCodeIndex(DISTANCEBASE, 30, distance);
	u32 extra_distance = (u32)(distance - DISTANCEBASE[dist_code]);

	u32 pos = values->size;
	/*TODO: return error when this fails (out of memory)*/
	u32 ok = uivector_resize(values, values->size + 4);
	if (ok) {
		values->data[pos + 0] = length_code + FIRST_LENGTH_CODE_INDEX;
		values->data[pos + 1] = extra_length;
		values->data[pos + 2] = dist_code;
		values->data[pos + 3] = extra_distance;
	}
}

/*3 bytes of data get encoded into two bytes. The hash cannot use more than 3
bytes as input because 3 is the minimum match length for deflate*/
static const u32 HASH_NUM_VALUES = 65536;
static const u32 HASH_BIT_MASK =
	65535; /*HASH_NUM_VALUES - 1, but C90 does not like that as initializer*/

typedef struct Hash {
	int *head; /*hash value to head circular pos - can be outdated if went around window*/
	/*circular pos to prev circular pos*/
	u16 *chain;
	int *val; /*circular pos to hash value*/

	/*TODO: do this not only for zeros but for any repeated byte. However for PNG
  it's always going to be the zeros that dominate, so not important for PNG*/
	int *headz; /*similar to head, but for chainz*/
	u16 *chainz; /*those with same amount of zeros*/
	u16 *zeros; /*length of zeros streak, used as a second hash chain*/
} Hash;

static u32 hash_init(Hash *hash, u32 windowsize)
{
	u32 i;
	hash->head = (int *)png_malloc(sizeof(int) * HASH_NUM_VALUES);
	hash->val = (int *)png_malloc(sizeof(int) * windowsize);
	hash->chain = (u16 *)png_malloc(sizeof(u16) * windowsize);

	hash->zeros = (u16 *)png_malloc(sizeof(u16) * windowsize);
	hash->headz = (int *)png_malloc(sizeof(int) * (MAX_SUPPORTED_DEFLATE_LENGTH + 1));
	hash->chainz = (u16 *)png_malloc(sizeof(u16) * windowsize);

	if (!hash->head || !hash->chain || !hash->val || !hash->headz || !hash->chainz ||
	    !hash->zeros) {
		return 83; /*alloc fail*/
	}

	/*initialize hash table*/
	for (i = 0; i != HASH_NUM_VALUES; ++i)
		hash->head[i] = -1;
	for (i = 0; i != windowsize; ++i)
		hash->val[i] = -1;
	for (i = 0; i != windowsize; ++i)
		hash->chain[i] = i; /*same value as index indicates uninitialized*/

	for (i = 0; i <= MAX_SUPPORTED_DEFLATE_LENGTH; ++i)
		hash->headz[i] = -1;
	for (i = 0; i != windowsize; ++i)
		hash->chainz[i] = i; /*same value as index indicates uninitialized*/

	return 0;
}

static void hash_cleanup(Hash *hash)
{
	png_free(hash->head);
	png_free(hash->val);
	png_free(hash->chain);

	png_free(hash->zeros);
	png_free(hash->headz);
	png_free(hash->chainz);
}

static u32 getHash(const u8 *data, u32 size, u32 pos)
{
	u32 result = 0;
	if (pos + 2 < size) {
		/*A simple shift and xor hash is used. Since the data of PNGs is dominated
    by zeroes due to the filters, a better hash does not have a significant
    effect on speed in traversing the chain, and causes more time spend on
    calculating the hash.*/
		result ^= ((u32)data[pos + 0] << 0u);
		result ^= ((u32)data[pos + 1] << 4u);
		result ^= ((u32)data[pos + 2] << 8u);
	} else {
		u32 amount, i;
		if (pos >= size)
			return 0;
		amount = size - pos;
		for (i = 0; i != amount; ++i)
			result ^= ((u32)data[pos + i] << (i * 8u));
	}
	return result & HASH_BIT_MASK;
}

static u32 countZeros(const u8 *data, u32 size, u32 pos)
{
	const u8 *start = data + pos;
	const u8 *end = start + MAX_SUPPORTED_DEFLATE_LENGTH;
	if (end > data + size)
		end = data + size;
	data = start;
	while (data != end && *data == 0)
		++data;
	/*subtracting two addresses returned as 32-bit number (max value is MAX_SUPPORTED_DEFLATE_LENGTH)*/
	return (u32)(data - start);
}

/*wpos = pos & (windowsize - 1)*/
static void updateHashChain(Hash *hash, u32 wpos, u32 hashval, u16 numzeros)
{
	hash->val[wpos] = (int)hashval;
	if (hash->head[hashval] != -1)
		hash->chain[wpos] = hash->head[hashval];
	hash->head[hashval] = (int)wpos;

	hash->zeros[wpos] = numzeros;
	if (hash->headz[numzeros] != -1)
		hash->chainz[wpos] = hash->headz[numzeros];
	hash->headz[numzeros] = (int)wpos;
}

/*
LZ77-encode the data. Return value is error code. The input are raw bytes, the output
is in the form of u32 integers with codes representing for example literal bytes, or
length/distance pairs.
It uses a hash table technique to let it encode faster. When doing LZ77 encoding, a
sliding window (of windowsize) is used, and all past bytes in that window can be used as
the "dictionary". A brute force search through all possible distances would be slow, and
this hash technique is one out of several ways to speed this up.
*/
static u32 encodeLZ77(uivector *out, Hash *hash, const u8 *in, u32 inpos, u32 insize,
		      u32 windowsize, u32 minmatch, u32 nicematch, u32 lazymatching)
{
	u32 pos;
	u32 i, error = 0;
	/*for large window lengths, assume the user wants no compression loss. Otherwise, max hash chain length speedup.*/
	u32 maxchainlength = windowsize >= 8192 ? windowsize : windowsize / 8u;
	u32 maxlazymatch = windowsize >= 8192 ? MAX_SUPPORTED_DEFLATE_LENGTH : 64;

	u32 usezeros =
		1; /*not sure if setting it to false for windowsize < 8192 is better or worse*/
	u32 numzeros = 0;

	u32 offset; /*the offset represents the distance in LZ77 terminology*/
	u32 length;
	u32 lazy = 0;
	u32 lazylength = 0, lazyoffset = 0;
	u32 hashval;
	u32 current_offset, current_length;
	u32 prev_offset;
	const u8 *lastptr, *foreptr, *backptr;
	u32 hashpos;

	if (windowsize == 0 || windowsize > 32768)
		return 60; /*error: windowsize smaller/larger than allowed*/
	if ((windowsize & (windowsize - 1)) != 0)
		return 90; /*error: must be power of two*/

	if (nicematch > MAX_SUPPORTED_DEFLATE_LENGTH)
		nicematch = MAX_SUPPORTED_DEFLATE_LENGTH;

	for (pos = inpos; pos < insize; ++pos) {
		u32 wpos = pos & (windowsize - 1); /*position for in 'circular' hash buffers*/
		u32 chainlength = 0;

		hashval = getHash(in, insize, pos);

		if (usezeros && hashval == 0) {
			if (numzeros == 0)
				numzeros = countZeros(in, insize, pos);
			else if (pos + numzeros > insize || in[pos + numzeros - 1] != 0)
				--numzeros;
		} else {
			numzeros = 0;
		}

		updateHashChain(hash, wpos, hashval, numzeros);

		/*the length and offset found for the current position*/
		length = 0;
		offset = 0;

		hashpos = hash->chain[wpos];

		lastptr = &in[insize < pos + MAX_SUPPORTED_DEFLATE_LENGTH ?
					    insize :
					    pos + MAX_SUPPORTED_DEFLATE_LENGTH];

		/*search for the longest string*/
		prev_offset = 0;
		for (;;) {
			if (chainlength++ >= maxchainlength)
				break;
			current_offset = (u32)(hashpos <= wpos ? wpos - hashpos :
								       wpos - hashpos + windowsize);

			if (current_offset < prev_offset)
				break; /*stop when went completely around the circular buffer*/
			prev_offset = current_offset;
			if (current_offset > 0) {
				/*test the next characters*/
				foreptr = &in[pos];
				backptr = &in[pos - current_offset];

				/*common case in PNGs is lots of zeros. Quickly skip over them as a speedup*/
				if (numzeros >= 3) {
					u32 skip = hash->zeros[hashpos];
					if (skip > numzeros)
						skip = numzeros;
					backptr += skip;
					foreptr += skip;
				}

				while (foreptr != lastptr &&
				       *backptr ==
					       *foreptr) /*maximum supported length by deflate is max length*/
				{
					++backptr;
					++foreptr;
				}
				current_length = (u32)(foreptr - &in[pos]);

				if (current_length > length) {
					length = current_length; /*the longest length*/
					offset =
						current_offset; /*the offset that is related to this longest length*/
					/*jump out once a length of max length is found (speed gain). This also jumps
          out if length is MAX_SUPPORTED_DEFLATE_LENGTH*/
					if (current_length >= nicematch)
						break;
				}
			}

			if (hashpos == hash->chain[hashpos])
				break;

			if (numzeros >= 3 && length > numzeros) {
				hashpos = hash->chainz[hashpos];
				if (hash->zeros[hashpos] != numzeros)
					break;
			} else {
				hashpos = hash->chain[hashpos];
				/*outdated hash value, happens if particular value was not encountered in whole last window*/
				if (hash->val[hashpos] != (int)hashval)
					break;
			}
		}

		if (lazymatching) {
			if (!lazy && length >= 3 && length <= maxlazymatch &&
			    length < MAX_SUPPORTED_DEFLATE_LENGTH) {
				lazy = 1;
				lazylength = length;
				lazyoffset = offset;
				continue; /*try the next byte*/
			}
			if (lazy) {
				lazy = 0;
				if (pos == 0)
					ERROR_BREAK(81);
				if (length > lazylength + 1) {
					/*push the previous character as literal*/
					if (!uivector_push_back(out, in[pos - 1]))
						ERROR_BREAK(83 /*alloc fail*/);
				} else {
					length = lazylength;
					offset = lazyoffset;
					hash->head[hashval] =
						-1; /*the same hashchain update will be done, this ensures no wrong alteration*/
					hash->headz[numzeros] = -1; /*idem*/
					--pos;
				}
			}
		}
		if (length >= 3 && offset > windowsize)
			ERROR_BREAK(86 /*too big (or overflown negative) offset*/);

		/*encode it as length/distance pair or literal value*/
		if (length <
		    3) /*only lengths of 3 or higher are supported as length/distance pair*/ {
			if (!uivector_push_back(out, in[pos]))
				ERROR_BREAK(83 /*alloc fail*/);
		} else if (length < minmatch || (length == 3 && offset > 4096)) {
			/*compensate for the fact that longer offsets have more extra bits, a
      length of only 3 may be not worth it then*/
			if (!uivector_push_back(out, in[pos]))
				ERROR_BREAK(83 /*alloc fail*/);
		} else {
			addLengthDistance(out, length, offset);
			for (i = 1; i < length; ++i) {
				++pos;
				wpos = pos & (windowsize - 1);
				hashval = getHash(in, insize, pos);
				if (usezeros && hashval == 0) {
					if (numzeros == 0)
						numzeros = countZeros(in, insize, pos);
					else if (pos + numzeros > insize ||
						 in[pos + numzeros - 1] != 0)
						--numzeros;
				} else {
					numzeros = 0;
				}
				updateHashChain(hash, wpos, hashval, numzeros);
			}
		}
	} /*end of the loop through each character of input*/

	return error;
}

/* /////////////////////////////////////////////////////////////////////////// */

static u32 deflateNoCompression(ucvector *out, const u8 *data, u32 datasize)
{
	/*non compressed deflate block data: 1 bit BFINAL,2 bits BTYPE,(5 bits): it jumps to start of next byte,
  2 bytes LEN, 2 bytes NLEN, LEN bytes literal DATA*/

	u32 i, numdeflateblocks = (datasize + 65534u) / 65535u;
	u32 datapos = 0;
	for (i = 0; i != numdeflateblocks; ++i) {
		u32 BFINAL, BTYPE, LEN, NLEN;
		u8 firstbyte;
		u32 pos = out->size;

		BFINAL = (i == numdeflateblocks - 1);
		BTYPE = 0;

		LEN = 65535;
		if (datasize - datapos < 65535u)
			LEN = (u32)datasize - datapos;
		NLEN = 65535 - LEN;

		if (!ucvector_resize(out, out->size + LEN + 5))
			return 83; /*alloc fail*/

		firstbyte = (u8)(BFINAL + ((BTYPE & 1u) << 1u) + ((BTYPE & 2u) << 1u));
		out->data[pos + 0] = firstbyte;
		out->data[pos + 1] = (u8)(LEN & 255);
		out->data[pos + 2] = (u8)(LEN >> 8u);
		out->data[pos + 3] = (u8)(NLEN & 255);
		out->data[pos + 4] = (u8)(NLEN >> 8u);
		png_memcpy(out->data + pos + 5, data + datapos, LEN);
		datapos += LEN;
	}

	return 0;
}

/*
write the lz77-encoded data, which has lit, len and dist codes, to compressed stream using huffman trees.
tree_ll: the tree for lit and len codes.
tree_d: the tree for distance codes.
*/
static void writeLZ77data(pngBitWriter *writer, const uivector *lz77_encoded,
			  const HuffmanTree *tree_ll, const HuffmanTree *tree_d)
{
	u32 i = 0;
	for (i = 0; i != lz77_encoded->size; ++i) {
		u32 val = lz77_encoded->data[i];
		writeBitsReversed(writer, tree_ll->codes[val], tree_ll->lengths[val]);
		if (val > 256) /*for a length code, 3 more things have to be added*/ {
			u32 length_index = val - FIRST_LENGTH_CODE_INDEX;
			u32 n_length_extra_bits = LENGTHEXTRA[length_index];
			u32 length_extra_bits = lz77_encoded->data[++i];

			u32 distance_code = lz77_encoded->data[++i];

			u32 distance_index = distance_code;
			u32 n_distance_extra_bits = DISTANCEEXTRA[distance_index];
			u32 distance_extra_bits = lz77_encoded->data[++i];

			writeBits(writer, length_extra_bits, n_length_extra_bits);
			writeBitsReversed(writer, tree_d->codes[distance_code],
					  tree_d->lengths[distance_code]);
			writeBits(writer, distance_extra_bits, n_distance_extra_bits);
		}
	}
}

/*Deflate for a block of type "dynamic", that is, with freely, optimally, created huffman trees*/
static u32 deflateDynamic(pngBitWriter *writer, Hash *hash, const u8 *data, u32 datapos,
			  u32 dataend, const pngCompressSettings *settings, u32 final)
{
	u32 error = 0;

	/*
  A block is compressed as follows: The PNG data is lz77 encoded, resulting in
  literal bytes and length/distance pairs. This is then huffman compressed with
  two huffman trees. One huffman tree is used for the lit and len values ("ll"),
  another huffman tree is used for the dist values ("d"). These two trees are
  stored using their code lengths, and to compress even more these code lengths
  are also run-length encoded and huffman compressed. This gives a huffman tree
  of code lengths "cl". The code lengths used to describe this third tree are
  the code length code lengths ("clcl").
  */

	/*The lz77 encoded data, represented with integers since there will also be length and distance codes in it*/
	uivector lz77_encoded;
	HuffmanTree tree_ll; /*tree for lit,len values*/
	HuffmanTree tree_d; /*tree for distance codes*/
	HuffmanTree tree_cl; /*tree for encoding the code lengths representing tree_ll and tree_d*/
	u32 *frequencies_ll = 0; /*frequency of lit,len codes*/
	u32 *frequencies_d = 0; /*frequency of dist codes*/
	u32 *frequencies_cl = 0; /*frequency of code length codes*/
	u32 *bitlen_lld =
		0; /*lit,len,dist code lengths (int bits), literally (without repeat codes).*/
	u32 *bitlen_lld_e =
		0; /*bitlen_lld encoded with repeat codes (this is a rudimentary run length compression)*/
	u32 datasize = dataend - datapos;

	/*
  If we could call "bitlen_cl" the the code length code lengths ("clcl"), that is the bit lengths of codes to represent
  tree_cl in CLCL_ORDER, then due to the huffman compression of huffman tree representations ("two levels"), there are
  some analogies:
  bitlen_lld is to tree_cl what data is to tree_ll and tree_d.
  bitlen_lld_e is to bitlen_lld what lz77_encoded is to data.
  bitlen_cl is to bitlen_lld_e what bitlen_lld is to lz77_encoded.
  */

	u32 BFINAL = final;
	u32 i;
	u32 numcodes_ll, numcodes_d, numcodes_lld, numcodes_lld_e, numcodes_cl;
	u32 HLIT, HDIST, HCLEN;

	uivector_init(&lz77_encoded);
	HuffmanTree_init(&tree_ll);
	HuffmanTree_init(&tree_d);
	HuffmanTree_init(&tree_cl);
	/* could fit on stack, but >1KB is on the larger side so allocate instead */
	frequencies_ll = (u32 *)png_malloc(286 * sizeof(*frequencies_ll));
	frequencies_d = (u32 *)png_malloc(30 * sizeof(*frequencies_d));
	frequencies_cl = (u32 *)png_malloc(NUM_CODE_LENGTH_CODES * sizeof(*frequencies_cl));

	if (!frequencies_ll || !frequencies_d || !frequencies_cl)
		error = 83; /*alloc fail*/

	/*This while loop never loops due to a break at the end, it is here to
  allow breaking out of it to the cleanup phase on error conditions.*/
	while (!error) {
		png_memset(frequencies_ll, 0, 286 * sizeof(*frequencies_ll));
		png_memset(frequencies_d, 0, 30 * sizeof(*frequencies_d));
		png_memset(frequencies_cl, 0, NUM_CODE_LENGTH_CODES * sizeof(*frequencies_cl));

		if (settings->use_lz77) {
			error = encodeLZ77(&lz77_encoded, hash, data, datapos, dataend,
					   settings->windowsize, settings->minmatch,
					   settings->nicematch, settings->lazymatching);
			if (error)
				break;
		} else {
			if (!uivector_resize(&lz77_encoded, datasize))
				ERROR_BREAK(83 /*alloc fail*/);
			for (i = datapos; i < dataend; ++i)
				lz77_encoded.data[i - datapos] =
					data[i]; /*no LZ77, but still will be Huffman compressed*/
		}

		/*Count the frequencies of lit, len and dist codes*/
		for (i = 0; i != lz77_encoded.size; ++i) {
			u32 symbol = lz77_encoded.data[i];
			++frequencies_ll[symbol];
			if (symbol > 256) {
				u32 dist = lz77_encoded.data[i + 2];
				++frequencies_d[dist];
				i += 3;
			}
		}
		frequencies_ll[256] =
			1; /*there will be exactly 1 end code, at the end of the block*/

		/*Make both huffman trees, one for the lit and len codes, one for the dist codes*/
		error = HuffmanTree_makeFromFrequencies(&tree_ll, frequencies_ll, 257, 286, 15);
		if (error)
			break;
		/*2, not 1, is chosen for mincodes: some buggy PNG decoders require at least 2 symbols in the dist tree*/
		error = HuffmanTree_makeFromFrequencies(&tree_d, frequencies_d, 2, 30, 15);
		if (error)
			break;

		numcodes_ll = PNG_MIN(tree_ll.numcodes, 286);
		numcodes_d = PNG_MIN(tree_d.numcodes, 30);
		/*store the code lengths of both generated trees in bitlen_lld*/
		numcodes_lld = numcodes_ll + numcodes_d;
		bitlen_lld = (u32 *)png_malloc(numcodes_lld * sizeof(*bitlen_lld));
		/*numcodes_lld_e never needs more size than bitlen_lld*/
		bitlen_lld_e = (u32 *)png_malloc(numcodes_lld * sizeof(*bitlen_lld_e));
		if (!bitlen_lld || !bitlen_lld_e)
			ERROR_BREAK(83); /*alloc fail*/
		numcodes_lld_e = 0;

		for (i = 0; i != numcodes_ll; ++i)
			bitlen_lld[i] = tree_ll.lengths[i];
		for (i = 0; i != numcodes_d; ++i)
			bitlen_lld[numcodes_ll + i] = tree_d.lengths[i];

		/*run-length compress bitlen_ldd into bitlen_lld_e by using repeat codes 16 (copy length 3-6 times),
    17 (3-10 zeroes), 18 (11-138 zeroes)*/
		for (i = 0; i != numcodes_lld; ++i) {
			u32 j = 0; /*amount of repetitions*/
			while (i + j + 1 < numcodes_lld && bitlen_lld[i + j + 1] == bitlen_lld[i])
				++j;

			if (bitlen_lld[i] == 0 && j >= 2) /*repeat code for zeroes*/ {
				++j; /*include the first zero*/
				if (j <= 10) /*repeat code 17 supports max 10 zeroes*/ {
					bitlen_lld_e[numcodes_lld_e++] = 17;
					bitlen_lld_e[numcodes_lld_e++] = j - 3;
				} else /*repeat code 18 supports max 138 zeroes*/ {
					if (j > 138)
						j = 138;
					bitlen_lld_e[numcodes_lld_e++] = 18;
					bitlen_lld_e[numcodes_lld_e++] = j - 11;
				}
				i += (j - 1);
			} else if (j >= 3) /*repeat code for value other than zero*/ {
				u32 k;
				u32 num = j / 6u, rest = j % 6u;
				bitlen_lld_e[numcodes_lld_e++] = bitlen_lld[i];
				for (k = 0; k < num; ++k) {
					bitlen_lld_e[numcodes_lld_e++] = 16;
					bitlen_lld_e[numcodes_lld_e++] = 6 - 3;
				}
				if (rest >= 3) {
					bitlen_lld_e[numcodes_lld_e++] = 16;
					bitlen_lld_e[numcodes_lld_e++] = rest - 3;
				} else
					j -= rest;
				i += j;
			} else /*too short to benefit from repeat code*/ {
				bitlen_lld_e[numcodes_lld_e++] = bitlen_lld[i];
			}
		}

		/*generate tree_cl, the huffmantree of huffmantrees*/
		for (i = 0; i != numcodes_lld_e; ++i) {
			++frequencies_cl[bitlen_lld_e[i]];
			/*after a repeat code come the bits that specify the number of repetitions,
      those don't need to be in the frequencies_cl calculation*/
			if (bitlen_lld_e[i] >= 16)
				++i;
		}

		error = HuffmanTree_makeFromFrequencies(
			&tree_cl, frequencies_cl, NUM_CODE_LENGTH_CODES, NUM_CODE_LENGTH_CODES, 7);
		if (error)
			break;

		/*compute amount of code-length-code-lengths to output*/
		numcodes_cl = NUM_CODE_LENGTH_CODES;
		/*trim zeros at the end (using CLCL_ORDER), but minimum size must be 4 (see HCLEN below)*/
		while (numcodes_cl > 4u && tree_cl.lengths[CLCL_ORDER[numcodes_cl - 1u]] == 0) {
			numcodes_cl--;
		}

		/*
    Write everything into the output

    After the BFINAL and BTYPE, the dynamic block consists out of the following:
    - 5 bits HLIT, 5 bits HDIST, 4 bits HCLEN
    - (HCLEN+4)*3 bits code lengths of code length alphabet
    - HLIT + 257 code lengths of lit/length alphabet (encoded using the code length
      alphabet, + possible repetition codes 16, 17, 18)
    - HDIST + 1 code lengths of distance alphabet (encoded using the code length
      alphabet, + possible repetition codes 16, 17, 18)
    - compressed data
    - 256 (end code)
    */

		/*Write block type*/
		writeBits(writer, BFINAL, 1);
		writeBits(writer, 0, 1); /*first bit of BTYPE "dynamic"*/
		writeBits(writer, 1, 1); /*second bit of BTYPE "dynamic"*/

		/*write the HLIT, HDIST and HCLEN values*/
		/*all three sizes take trimmed ending zeroes into account, done either by HuffmanTree_makeFromFrequencies
    or in the loop for numcodes_cl above, which saves space. */
		HLIT = (u32)(numcodes_ll - 257);
		HDIST = (u32)(numcodes_d - 1);
		HCLEN = (u32)(numcodes_cl - 4);
		writeBits(writer, HLIT, 5);
		writeBits(writer, HDIST, 5);
		writeBits(writer, HCLEN, 4);

		/*write the code lengths of the code length alphabet ("bitlen_cl")*/
		for (i = 0; i != numcodes_cl; ++i)
			writeBits(writer, tree_cl.lengths[CLCL_ORDER[i]], 3);

		/*write the lengths of the lit/len AND the dist alphabet*/
		for (i = 0; i != numcodes_lld_e; ++i) {
			writeBitsReversed(writer, tree_cl.codes[bitlen_lld_e[i]],
					  tree_cl.lengths[bitlen_lld_e[i]]);
			/*extra bits of repeat codes*/
			if (bitlen_lld_e[i] == 16)
				writeBits(writer, bitlen_lld_e[++i], 2);
			else if (bitlen_lld_e[i] == 17)
				writeBits(writer, bitlen_lld_e[++i], 3);
			else if (bitlen_lld_e[i] == 18)
				writeBits(writer, bitlen_lld_e[++i], 7);
		}

		/*write the compressed data symbols*/
		writeLZ77data(writer, &lz77_encoded, &tree_ll, &tree_d);
		/*error: the length of the end code 256 must be larger than 0*/
		if (tree_ll.lengths[256] == 0)
			ERROR_BREAK(64);

		/*write the end code*/
		writeBitsReversed(writer, tree_ll.codes[256], tree_ll.lengths[256]);

		break; /*end of error-while*/
	}

	/*cleanup*/
	uivector_cleanup(&lz77_encoded);
	HuffmanTree_cleanup(&tree_ll);
	HuffmanTree_cleanup(&tree_d);
	HuffmanTree_cleanup(&tree_cl);
	png_free(frequencies_ll);
	png_free(frequencies_d);
	png_free(frequencies_cl);
	png_free(bitlen_lld);
	png_free(bitlen_lld_e);

	return error;
}

static u32 deflateFixed(pngBitWriter *writer, Hash *hash, const u8 *data, u32 datapos, u32 dataend,
			const pngCompressSettings *settings, u32 final)
{
	HuffmanTree tree_ll; /*tree for literal values and length codes*/
	HuffmanTree tree_d; /*tree for distance codes*/

	u32 BFINAL = final;
	u32 error = 0;
	u32 i;

	HuffmanTree_init(&tree_ll);
	HuffmanTree_init(&tree_d);

	error = generateFixedLitLenTree(&tree_ll);
	if (!error)
		error = generateFixedDistanceTree(&tree_d);

	if (!error) {
		writeBits(writer, BFINAL, 1);
		writeBits(writer, 1, 1); /*first bit of BTYPE*/
		writeBits(writer, 0, 1); /*second bit of BTYPE*/

		if (settings->use_lz77) /*LZ77 encoded*/ {
			uivector lz77_encoded;
			uivector_init(&lz77_encoded);
			error = encodeLZ77(&lz77_encoded, hash, data, datapos, dataend,
					   settings->windowsize, settings->minmatch,
					   settings->nicematch, settings->lazymatching);
			if (!error)
				writeLZ77data(writer, &lz77_encoded, &tree_ll, &tree_d);
			uivector_cleanup(&lz77_encoded);
		} else /*no LZ77, but still will be Huffman compressed*/ {
			for (i = datapos; i < dataend; ++i) {
				writeBitsReversed(writer, tree_ll.codes[data[i]],
						  tree_ll.lengths[data[i]]);
			}
		}
		/*add END code*/
		if (!error)
			writeBitsReversed(writer, tree_ll.codes[256], tree_ll.lengths[256]);
	}

	/*cleanup*/
	HuffmanTree_cleanup(&tree_ll);
	HuffmanTree_cleanup(&tree_d);

	return error;
}

static u32 png_deflatev(ucvector *out, const u8 *in, u32 insize,
			const pngCompressSettings *settings)
{
	u32 error = 0;
	u32 i, blocksize, numdeflateblocks;
	Hash hash;
	pngBitWriter writer;

	pngBitWriter_init(&writer, out);

	if (settings->btype > 2)
		return 61;
	else if (settings->btype == 0)
		return deflateNoCompression(out, in, insize);
	else if (settings->btype == 1)
		blocksize = insize;
	else /*if(settings->btype == 2)*/ {
		/*on PNGs, deflate blocks of 65-262k seem to give most dense encoding*/
		blocksize = insize / 8u + 8;
		if (blocksize < 65536)
			blocksize = 65536;
		if (blocksize > 262144)
			blocksize = 262144;
	}

	numdeflateblocks = (insize + blocksize - 1) / blocksize;
	if (numdeflateblocks == 0)
		numdeflateblocks = 1;

	error = hash_init(&hash, settings->windowsize);

	if (!error) {
		for (i = 0; i != numdeflateblocks && !error; ++i) {
			u32 final = (i == numdeflateblocks - 1);
			u32 start = i * blocksize;
			u32 end = start + blocksize;
			if (end > insize)
				end = insize;

			if (settings->btype == 1)
				error = deflateFixed(&writer, &hash, in, start, end, settings,
						     final);
			else if (settings->btype == 2)
				error = deflateDynamic(&writer, &hash, in, start, end, settings,
						       final);
		}
	}

	hash_cleanup(&hash);

	return error;
}

u32 png_deflate(u8 **out, u32 *outsize, const u8 *in, u32 insize,
		const pngCompressSettings *settings)
{
	ucvector v = ucvector_init(*out, *outsize);
	u32 error = png_deflatev(&v, in, insize, settings);
	*out = v.data;
	*outsize = v.size;
	return error;
}

static u32 deflate(u8 **out, u32 *outsize, const u8 *in, u32 insize,
		   const pngCompressSettings *settings)
{
	if (settings->custom_deflate) {
		u32 error = settings->custom_deflate(out, outsize, in, insize, settings);
		/*the custom deflate is allowed to have its own error codes, however, we translate it to code 111*/
		return error ? 111 : 0;
	} else {
		return png_deflate(out, outsize, in, insize, settings);
	}
}

#endif /*PNG_COMPILE_DECODER*/

/* ////////////////////////////////////////////////////////////////////////// */
/* / Adler32                                                                / */
/* ////////////////////////////////////////////////////////////////////////// */

static u32 update_adler32(u32 adler, const u8 *data, u32 len)
{
	u32 s1 = adler & 0xffffu;
	u32 s2 = (adler >> 16u) & 0xffffu;

	while (len != 0u) {
		u32 i;
		/*at least 5552 sums can be done before the sums overflow, saving a lot of module divisions*/
		u32 amount = len > 5552u ? 5552u : len;
		len -= amount;
		for (i = 0; i != amount; ++i) {
			s1 += (*data++);
			s2 += s1;
		}
		s1 %= 65521u;
		s2 %= 65521u;
	}

	return (s2 << 16u) | s1;
}

/*Return the adler32 of the bytes data[0..len-1]*/
static u32 adler32(const u8 *data, u32 len)
{
	return update_adler32(1u, data, len);
}

/* ////////////////////////////////////////////////////////////////////////// */
/* / Zlib                                                                   / */
/* ////////////////////////////////////////////////////////////////////////// */

#ifdef PNG_COMPILE_DECODER

static u32 png_zlib_decompressv(ucvector *out, const u8 *in, u32 insize,
				const pngDecompressSettings *settings)
{
	u32 error = 0;
	u32 CM, CINFO, FDICT;

	if (insize < 2)
		return 53; /*error, size of zlib data too small*/
	/*read information from zlib header*/
	if ((in[0] * 256 + in[1]) % 31 != 0) {
		/*error: 256 * in[0] + in[1] must be a multiple of 31, the FCHECK value is supposed to be made that way*/
		return 24;
	}

	CM = in[0] & 15;
	CINFO = (in[0] >> 4) & 15;
	/*FCHECK = in[1] & 31;*/ /*FCHECK is already tested above*/
	FDICT = (in[1] >> 5) & 1;
	/*FLEVEL = (in[1] >> 6) & 3;*/ /*FLEVEL is not used here*/

	if (CM != 8 || CINFO > 7) {
		/*error: only compression method 8: inflate with sliding window of 32k is supported by the PNG spec*/
		return 25;
	}
	if (FDICT != 0) {
		/*error: the specification of PNG says about the zlib stream:
      "The additional flags shall not specify a preset dictionary."*/
		return 26;
	}

	error = inflatev(out, in + 2, insize - 2, settings);
	if (error)
		return error;

	if (!settings->ignore_adler32) {
		u32 ADLER32 = png_read32bitInt(&in[insize - 4]);
		u32 checksum = adler32(out->data, (u32)(out->size));
		if (checksum != ADLER32)
			return 58; /*error, adler checksum not correct, data must be corrupted*/
	}

	return 0; /*no error*/
}

u32 png_zlib_decompress(u8 **out, u32 *outsize, const u8 *in, u32 insize,
			const pngDecompressSettings *settings)
{
	ucvector v = ucvector_init(*out, *outsize);
	u32 error = png_zlib_decompressv(&v, in, insize, settings);
	*out = v.data;
	*outsize = v.size;
	return error;
}

/*expected_size is expected output size, to avoid intermediate allocations. Set to 0 if not known. */
static u32 zlib_decompress(u8 **out, u32 *outsize, u32 expected_size, const u8 *in, u32 insize,
			   const pngDecompressSettings *settings)
{
	u32 error;
	if (settings->custom_zlib) {
		error = settings->custom_zlib(out, outsize, in, insize, settings);
		if (error) {
			/*the custom zlib is allowed to have its own error codes, however, we translate it to code 110*/
			error = 110;
			/*if there's a max output size, and the custom zlib returned error, then indicate that error instead*/
			if (settings->max_output_size && *outsize > settings->max_output_size)
				error = 109;
		}
	} else {
		ucvector v = ucvector_init(*out, *outsize);
		if (expected_size) {
			/*reserve the memory to avoid intermediate reallocations*/
			ucvector_resize(&v, *outsize + expected_size);
			v.size = *outsize;
		}
		error = png_zlib_decompressv(&v, in, insize, settings);
		*out = v.data;
		*outsize = v.size;
	}
	return error;
}

#endif /*PNG_COMPILE_DECODER*/

#ifdef PNG_COMPILE_ENCODER

u32 png_zlib_compress(u8 **out, u32 *outsize, const u8 *in, u32 insize,
		      const pngCompressSettings *settings)
{
	u32 i;
	u32 error;
	u8 *deflatedata = 0;
	u32 deflatesize = 0;

	error = deflate(&deflatedata, &deflatesize, in, insize, settings);

	*out = NULL;
	*outsize = 0;
	if (!error) {
		*outsize = deflatesize + 6;
		*out = (u8 *)png_malloc(*outsize);
		if (!*out)
			error = 83; /*alloc fail*/
	}

	if (!error) {
		u32 ADLER32 = adler32(in, (u32)insize);
		/*zlib data: 1 byte CMF (CM+CINFO), 1 byte FLG, deflate data, 4 byte ADLER32 checksum of the Decompressed data*/
		u32 CMF =
			120; /*0b01111000: CM 8, CINFO 7. With CINFO 7, any window size up to 32768 can be used.*/
		u32 FLEVEL = 0;
		u32 FDICT = 0;
		u32 CMFFLG = 256 * CMF + FDICT * 32 + FLEVEL * 64;
		u32 FCHECK = 31 - CMFFLG % 31;
		CMFFLG += FCHECK;

		(*out)[0] = (u8)(CMFFLG >> 8);
		(*out)[1] = (u8)(CMFFLG & 255);
		for (i = 0; i != deflatesize; ++i)
			(*out)[i + 2] = deflatedata[i];
		png_set32bitInt(&(*out)[*outsize - 4], ADLER32);
	}

	png_free(deflatedata);
	return error;
}

/* compress using the default or custom zlib function */
static u32 zlib_compress(u8 **out, u32 *outsize, const u8 *in, u32 insize,
			 const pngCompressSettings *settings)
{
	if (settings->custom_zlib) {
		u32 error = settings->custom_zlib(out, outsize, in, insize, settings);
		/*the custom zlib is allowed to have its own error codes, however, we translate it to code 111*/
		return error ? 111 : 0;
	} else {
		return png_zlib_compress(out, outsize, in, insize, settings);
	}
}

#endif /*PNG_COMPILE_ENCODER*/

#else /*no PNG_COMPILE_ZLIB*/

#ifdef PNG_COMPILE_DECODER
static u32 zlib_decompress(u8 **out, u32 *outsize, u32 expected_size, const u8 *in, u32 insize,
			   const pngDecompressSettings *settings)
{
	if (!settings->custom_zlib)
		return 87; /*no custom zlib function provided */
	(void)expected_size;
	return settings->custom_zlib(out, outsize, in, insize, settings);
}
#endif /*PNG_COMPILE_DECODER*/
#ifdef PNG_COMPILE_ENCODER
static u32 zlib_compress(u8 **out, u32 *outsize, const u8 *in, u32 insize,
			 const pngCompressSettings *settings)
{
	if (!settings->custom_zlib)
		return 87; /*no custom zlib function provided */
	return settings->custom_zlib(out, outsize, in, insize, settings);
}
#endif /*PNG_COMPILE_ENCODER*/

#endif /*PNG_COMPILE_ZLIB*/

/* ////////////////////////////////////////////////////////////////////////// */

#ifdef PNG_COMPILE_ENCODER

/*this is a good tradeoff between speed and compression ratio*/
#define DEFAULT_WINDOWSIZE 2048

void png_compress_settings_init(pngCompressSettings *settings)
{
	/*compress with dynamic huffman tree (not in the mathematical sense, just not the predefined one)*/
	settings->btype = 2;
	settings->use_lz77 = 1;
	settings->windowsize = DEFAULT_WINDOWSIZE;
	settings->minmatch = 3;
	settings->nicematch = 128;
	settings->lazymatching = 1;

	settings->custom_zlib = 0;
	settings->custom_deflate = 0;
	settings->custom_context = 0;
}

const pngCompressSettings png_default_compress_settings = { 2, 1, DEFAULT_WINDOWSIZE, 3, 128, 1, 0,
							    0, 0 };

#endif /*PNG_COMPILE_ENCODER*/

#ifdef PNG_COMPILE_DECODER

void png_decompress_settings_init(pngDecompressSettings *settings)
{
	settings->ignore_adler32 = 0;
	settings->ignore_nlen = 0;
	settings->max_output_size = 0;

	settings->custom_zlib = 0;
	settings->custom_inflate = 0;
	settings->custom_context = 0;
}

const pngDecompressSettings png_default_decompress_settings = { 0, 0, 0, 0, 0, 0 };

#endif /*PNG_COMPILE_DECODER*/

/* ////////////////////////////////////////////////////////////////////////// */
/* ////////////////////////////////////////////////////////////////////////// */
/* // End of Zlib related code. Begin of PNG related code.                 // */
/* ////////////////////////////////////////////////////////////////////////// */
/* ////////////////////////////////////////////////////////////////////////// */

#ifdef PNG_COMPILE_PNG

/* ////////////////////////////////////////////////////////////////////////// */
/* / CRC32                                                                  / */
/* ////////////////////////////////////////////////////////////////////////// */

#ifndef PNG_NO_COMPILE_CRC
/* CRC polynomial: 0xedb88320 */
static u32 png_crc32_table[256] = {
	0u,	     1996959894u, 3993919788u, 2567524794u, 124634137u,	 1886057615u, 3915621685u,
	2657392035u, 249268274u,  2044508324u, 3772115230u, 2547177864u, 162941995u,  2125561021u,
	3887607047u, 2428444049u, 498536548u,  1789927666u, 4089016648u, 2227061214u, 450548861u,
	1843258603u, 4107580753u, 2211677639u, 325883990u,  1684777152u, 4251122042u, 2321926636u,
	335633487u,  1661365465u, 4195302755u, 2366115317u, 997073096u,	 1281953886u, 3579855332u,
	2724688242u, 1006888145u, 1258607687u, 3524101629u, 2768942443u, 901097722u,  1119000684u,
	3686517206u, 2898065728u, 853044451u,  1172266101u, 3705015759u, 2882616665u, 651767980u,
	1373503546u, 3369554304u, 3218104598u, 565507253u,  1454621731u, 3485111705u, 3099436303u,
	671266974u,  1594198024u, 3322730930u, 2970347812u, 795835527u,	 1483230225u, 3244367275u,
	3060149565u, 1994146192u, 31158534u,   2563907772u, 4023717930u, 1907459465u, 112637215u,
	2680153253u, 3904427059u, 2013776290u, 251722036u,  2517215374u, 3775830040u, 2137656763u,
	141376813u,  2439277719u, 3865271297u, 1802195444u, 476864866u,	 2238001368u, 4066508878u,
	1812370925u, 453092731u,  2181625025u, 4111451223u, 1706088902u, 314042704u,  2344532202u,
	4240017532u, 1658658271u, 366619977u,  2362670323u, 4224994405u, 1303535960u, 984961486u,
	2747007092u, 3569037538u, 1256170817u, 1037604311u, 2765210733u, 3554079995u, 1131014506u,
	879679996u,  2909243462u, 3663771856u, 1141124467u, 855842277u,	 2852801631u, 3708648649u,
	1342533948u, 654459306u,  3188396048u, 3373015174u, 1466479909u, 544179635u,  3110523913u,
	3462522015u, 1591671054u, 702138776u,  2966460450u, 3352799412u, 1504918807u, 783551873u,
	3082640443u, 3233442989u, 3988292384u, 2596254646u, 62317068u,	 1957810842u, 3939845945u,
	2647816111u, 81470997u,	  1943803523u, 3814918930u, 2489596804u, 225274430u,  2053790376u,
	3826175755u, 2466906013u, 167816743u,  2097651377u, 4027552580u, 2265490386u, 503444072u,
	1762050814u, 4150417245u, 2154129355u, 426522225u,  1852507879u, 4275313526u, 2312317920u,
	282753626u,  1742555852u, 4189708143u, 2394877945u, 397917763u,	 1622183637u, 3604390888u,
	2714866558u, 953729732u,  1340076626u, 3518719985u, 2797360999u, 1068828381u, 1219638859u,
	3624741850u, 2936675148u, 906185462u,  1090812512u, 3747672003u, 2825379669u, 829329135u,
	1181335161u, 3412177804u, 3160834842u, 628085408u,  1382605366u, 3423369109u, 3138078467u,
	570562233u,  1426400815u, 3317316542u, 2998733608u, 733239954u,	 1555261956u, 3268935591u,
	3050360625u, 752459403u,  1541320221u, 2607071920u, 3965973030u, 1969922972u, 40735498u,
	2617837225u, 3943577151u, 1913087877u, 83908371u,   2512341634u, 3803740692u, 2075208622u,
	213261112u,  2463272603u, 3855990285u, 2094854071u, 198958881u,	 2262029012u, 4057260610u,
	1759359992u, 534414190u,  2176718541u, 4139329115u, 1873836001u, 414664567u,  2282248934u,
	4279200368u, 1711684554u, 285281116u,  2405801727u, 4167216745u, 1634467795u, 376229701u,
	2685067896u, 3608007406u, 1308918612u, 956543938u,  2808555105u, 3495958263u, 1231636301u,
	1047427035u, 2932959818u, 3654703836u, 1088359270u, 936918000u,	 2847714899u, 3736837829u,
	1202900863u, 817233897u,  3183342108u, 3401237130u, 1404277552u, 615818150u,  3134207493u,
	3453421203u, 1423857449u, 601450431u,  3009837614u, 3294710456u, 1567103746u, 711928724u,
	3020668471u, 3272380065u, 1510334235u, 755167117u
};

/*Return the CRC of the bytes buf[0..len-1].*/
u32 png_crc32(const u8 *data, u32 length)
{
	u32 r = 0xffffffffu;
	u32 i;
	for (i = 0; i < length; ++i) {
		r = png_crc32_table[(r ^ data[i]) & 0xffu] ^ (r >> 8u);
	}
	return r ^ 0xffffffffu;
}
#else /* !PNG_NO_COMPILE_CRC */
u32 png_crc32(const u8 *data, u32 length);
#endif /* !PNG_NO_COMPILE_CRC */

/* ////////////////////////////////////////////////////////////////////////// */
/* / Reading and writing PNG color channel bits                             / */
/* ////////////////////////////////////////////////////////////////////////// */

/* The color channel bits of less-than-8-bit pixels are read with the MSB of bytes first,
so pngBitWriter and pngBitReader can't be used for those. */

static u8 readBitFromReversedStream(u32 *bitpointer, const u8 *bitstream)
{
	u8 result = (u8)((bitstream[(*bitpointer) >> 3] >> (7 - ((*bitpointer) & 0x7))) & 1);
	++(*bitpointer);
	return result;
}

/* TODO: make this faster */
static u32 readBitsFromReversedStream(u32 *bitpointer, const u8 *bitstream, u32 nbits)
{
	u32 result = 0;
	u32 i;
	for (i = 0; i < nbits; ++i) {
		result <<= 1u;
		result |= (u32)readBitFromReversedStream(bitpointer, bitstream);
	}
	return result;
}

static void setBitOfReversedStream(u32 *bitpointer, u8 *bitstream, u8 bit)
{
	/*the current bit in bitstream may be 0 or 1 for this to work*/
	if (bit == 0)
		bitstream[(*bitpointer) >> 3u] &= (u8)(~(1u << (7u - ((*bitpointer) & 7u))));
	else
		bitstream[(*bitpointer) >> 3u] |= (1u << (7u - ((*bitpointer) & 7u)));
	++(*bitpointer);
}

/* ////////////////////////////////////////////////////////////////////////// */
/* / PNG chunks                                                             / */
/* ////////////////////////////////////////////////////////////////////////// */

u32 png_chunk_length(const u8 *chunk)
{
	return png_read32bitInt(&chunk[0]);
}

void png_chunk_type(char type[5], const u8 *chunk)
{
	u32 i;
	for (i = 0; i != 4; ++i)
		type[i] = (char)chunk[4 + i];
	type[4] = 0; /*null termination char*/
}

u8 png_chunk_type_equals(const u8 *chunk, const char *type)
{
	if (png_strlen(type) != 4)
		return 0;
	return (chunk[4] == type[0] && chunk[5] == type[1] && chunk[6] == type[2] &&
		chunk[7] == type[3]);
}

u8 png_chunk_ancillary(const u8 *chunk)
{
	return ((chunk[4] & 32) != 0);
}

u8 png_chunk_private(const u8 *chunk)
{
	return ((chunk[6] & 32) != 0);
}

u8 png_chunk_safetocopy(const u8 *chunk)
{
	return ((chunk[7] & 32) != 0);
}

u8 *png_chunk_data(u8 *chunk)
{
	return &chunk[8];
}

const u8 *png_chunk_data_const(const u8 *chunk)
{
	return &chunk[8];
}

u32 png_chunk_check_crc(const u8 *chunk)
{
	u32 length = png_chunk_length(chunk);
	u32 CRC = png_read32bitInt(&chunk[length + 8]);
	/*the CRC is taken of the data and the 4 chunk type letters, not the length*/
	u32 checksum = png_crc32(&chunk[4], length + 4);
	if (CRC != checksum)
		return 1;
	else
		return 0;
}

void png_chunk_generate_crc(u8 *chunk)
{
	u32 length = png_chunk_length(chunk);
	u32 CRC = png_crc32(&chunk[4], length + 4);
	png_set32bitInt(chunk + 8 + length, CRC);
}

u8 *png_chunk_next(u8 *chunk, u8 *end)
{
	if (chunk >= end || end - chunk < 12)
		return end; /*too small to contain a chunk*/
	if (chunk[0] == 0x89 && chunk[1] == 0x50 && chunk[2] == 0x4e && chunk[3] == 0x47 &&
	    chunk[4] == 0x0d && chunk[5] == 0x0a && chunk[6] == 0x1a && chunk[7] == 0x0a) {
		/* Is PNG magic header at start of PNG file. Jump to first actual chunk. */
		return chunk + 8;
	} else {
		u32 total_chunk_length;
		u8 *result;
		if (png_addofl(png_chunk_length(chunk), 12, &total_chunk_length))
			return end;
		result = chunk + total_chunk_length;
		if (result < chunk)
			return end; /*pointer overflow*/
		return result;
	}
}

const u8 *png_chunk_next_const(const u8 *chunk, const u8 *end)
{
	if (chunk >= end || end - chunk < 12)
		return end; /*too small to contain a chunk*/
	if (chunk[0] == 0x89 && chunk[1] == 0x50 && chunk[2] == 0x4e && chunk[3] == 0x47 &&
	    chunk[4] == 0x0d && chunk[5] == 0x0a && chunk[6] == 0x1a && chunk[7] == 0x0a) {
		/* Is PNG magic header at start of PNG file. Jump to first actual chunk. */
		return chunk + 8;
	} else {
		u32 total_chunk_length;
		const u8 *result;
		if (png_addofl(png_chunk_length(chunk), 12, &total_chunk_length))
			return end;
		result = chunk + total_chunk_length;
		if (result < chunk)
			return end; /*pointer overflow*/
		return result;
	}
}

u8 *png_chunk_find(u8 *chunk, u8 *end, const char type[5])
{
	for (;;) {
		if (chunk >= end || end - chunk < 12)
			return 0; /* past file end: chunk + 12 > end */
		if (png_chunk_type_equals(chunk, type))
			return chunk;
		chunk = png_chunk_next(chunk, end);
	}
}

const u8 *png_chunk_find_const(const u8 *chunk, const u8 *end, const char type[5])
{
	for (;;) {
		if (chunk >= end || end - chunk < 12)
			return 0; /* past file end: chunk + 12 > end */
		if (png_chunk_type_equals(chunk, type))
			return chunk;
		chunk = png_chunk_next_const(chunk, end);
	}
}

u32 png_chunk_append(u8 **out, u32 *outsize, const u8 *chunk)
{
	u32 i;
	u32 total_chunk_length, new_length;
	u8 *chunk_start, *new_buffer;

	if (png_addofl(png_chunk_length(chunk), 12, &total_chunk_length))
		return 77;
	if (png_addofl(*outsize, total_chunk_length, &new_length))
		return 77;

	new_buffer = (u8 *)png_realloc(*out, new_length);
	if (!new_buffer)
		return 83; /*alloc fail*/
	(*out) = new_buffer;
	(*outsize) = new_length;
	chunk_start = &(*out)[new_length - total_chunk_length];

	for (i = 0; i != total_chunk_length; ++i)
		chunk_start[i] = chunk[i];

	return 0;
}

/*Sets length and name and allocates the space for data and crc but does not
set data or crc yet. Returns the start of the chunk in chunk. The start of
the data is at chunk + 8. To finalize chunk, add the data, then use
png_chunk_generate_crc */
static u32 png_chunk_init(u8 **chunk, ucvector *out, u32 length, const char *type)
{
	u32 new_length = out->size;
	if (png_addofl(new_length, length, &new_length))
		return 77;
	if (png_addofl(new_length, 12, &new_length))
		return 77;
	if (!ucvector_resize(out, new_length))
		return 83; /*alloc fail*/
	*chunk = out->data + new_length - length - 12u;

	/*1: length*/
	png_set32bitInt(*chunk, length);

	/*2: chunk name (4 letters)*/
	png_memcpy(*chunk + 4, type, 4);

	return 0;
}

/* like png_chunk_create but with custom allocsize */
static u32 png_chunk_createv(ucvector *out, u32 length, const char *type, const u8 *data)
{
	u8 *chunk;
	CERROR_TRY_RETURN(png_chunk_init(&chunk, out, length, type));

	/*3: the data*/
	png_memcpy(chunk + 8, data, length);

	/*4: CRC (of the chunkname characters and the data)*/
	png_chunk_generate_crc(chunk);

	return 0;
}

u32 png_chunk_create(u8 **out, u32 *outsize, u32 length, const char *type, const u8 *data)
{
	ucvector v = ucvector_init(*out, *outsize);
	u32 error = png_chunk_createv(&v, length, type, data);
	*out = v.data;
	*outsize = v.size;
	return error;
}

/* ////////////////////////////////////////////////////////////////////////// */
/* / Color types, channels, bits                                            / */
/* ////////////////////////////////////////////////////////////////////////// */

/*checks if the colortype is valid and the bitdepth bd is allowed for this colortype.
Return value is a png error code.*/
static u32 checkColorValidity(pngColorType colortype, u32 bd)
{
	switch (colortype) {
	case LCT_GREY:
		if (!(bd == 1 || bd == 2 || bd == 4 || bd == 8 || bd == 16))
			return 37;
		break;
	case LCT_RGB:
		if (!(bd == 8 || bd == 16))
			return 37;
		break;
	case LCT_PALETTE:
		if (!(bd == 1 || bd == 2 || bd == 4 || bd == 8))
			return 37;
		break;
	case LCT_GREY_ALPHA:
		if (!(bd == 8 || bd == 16))
			return 37;
		break;
	case LCT_RGBA:
		if (!(bd == 8 || bd == 16))
			return 37;
		break;
	case LCT_MAX_OCTET_VALUE:
		return 31; /* invalid color type */
	default:
		return 31; /* invalid color type */
	}
	return 0; /*allowed color type / bits combination*/
}

static u32 getNumColorChannels(pngColorType colortype)
{
	switch (colortype) {
	case LCT_GREY:
		return 1;
	case LCT_RGB:
		return 3;
	case LCT_PALETTE:
		return 1;
	case LCT_GREY_ALPHA:
		return 2;
	case LCT_RGBA:
		return 4;
	case LCT_MAX_OCTET_VALUE:
		return 0; /* invalid color type */
	default:
		return 0; /*invalid color type*/
	}
}

static u32 png_get_bpp_lct(pngColorType colortype, u32 bitdepth)
{
	/*bits per pixel is amount of channels * bits per channel*/
	return getNumColorChannels(colortype) * bitdepth;
}

/* ////////////////////////////////////////////////////////////////////////// */

void png_color_mode_init(pngColorMode *info)
{
	info->key_defined = 0;
	info->key_r = info->key_g = info->key_b = 0;
	info->colortype = LCT_RGBA;
	info->bitdepth = 8;
	info->palette = 0;
	info->palettesize = 0;
}

/*allocates palette memory if needed, and initializes all colors to black*/
static void png_color_mode_alloc_palette(pngColorMode *info)
{
	u32 i;
	/*if the palette is already allocated, it will have size 1024 so no reallocation needed in that case*/
	/*the palette must have room for up to 256 colors with 4 bytes each.*/
	if (!info->palette)
		info->palette = (u8 *)png_malloc(1024);
	if (!info->palette)
		return; /*alloc fail*/
	for (i = 0; i != 256; ++i) {
		/*Initialize all unused colors with black, the value used for invalid palette indices.
    This is an error according to the PNG spec, but common PNG decoders make it black instead.
    That makes color conversion slightly faster due to no error handling needed.*/
		info->palette[i * 4 + 0] = 0;
		info->palette[i * 4 + 1] = 0;
		info->palette[i * 4 + 2] = 0;
		info->palette[i * 4 + 3] = 255;
	}
}

void png_color_mode_cleanup(pngColorMode *info)
{
	png_palette_clear(info);
}

u32 png_color_mode_copy(pngColorMode *dest, const pngColorMode *source)
{
	png_color_mode_cleanup(dest);
	png_memcpy(dest, source, sizeof(pngColorMode));
	if (source->palette) {
		dest->palette = (u8 *)png_malloc(1024);
		if (!dest->palette && source->palettesize)
			return 83; /*alloc fail*/
		png_memcpy(dest->palette, source->palette, source->palettesize * 4);
	}
	return 0;
}

pngColorMode png_color_mode_make(pngColorType colortype, u32 bitdepth)
{
	pngColorMode result;
	png_color_mode_init(&result);
	result.colortype = colortype;
	result.bitdepth = bitdepth;
	return result;
}

static int png_color_mode_equal(const pngColorMode *a, const pngColorMode *b)
{
	u32 i;
	if (a->colortype != b->colortype)
		return 0;
	if (a->bitdepth != b->bitdepth)
		return 0;
	if (a->key_defined != b->key_defined)
		return 0;
	if (a->key_defined) {
		if (a->key_r != b->key_r)
			return 0;
		if (a->key_g != b->key_g)
			return 0;
		if (a->key_b != b->key_b)
			return 0;
	}
	if (a->palettesize != b->palettesize)
		return 0;
	for (i = 0; i != a->palettesize * 4; ++i) {
		if (a->palette[i] != b->palette[i])
			return 0;
	}
	return 1;
}

void png_palette_clear(pngColorMode *info)
{
	if (info->palette)
		png_free(info->palette);
	info->palette = 0;
	info->palettesize = 0;
}

u32 png_palette_add(pngColorMode *info, u8 r, u8 g, u8 b, u8 a)
{
	if (!info->palette) /*allocate palette if empty*/ {
		png_color_mode_alloc_palette(info);
		if (!info->palette)
			return 83; /*alloc fail*/
	}
	if (info->palettesize >= 256) {
		return 108; /*too many palette values*/
	}
	info->palette[4 * info->palettesize + 0] = r;
	info->palette[4 * info->palettesize + 1] = g;
	info->palette[4 * info->palettesize + 2] = b;
	info->palette[4 * info->palettesize + 3] = a;
	++info->palettesize;
	return 0;
}

/*calculate bits per pixel out of colortype and bitdepth*/
u32 png_get_bpp(const pngColorMode *info)
{
	return png_get_bpp_lct(info->colortype, info->bitdepth);
}

u32 png_get_channels(const pngColorMode *info)
{
	return getNumColorChannels(info->colortype);
}

u32 png_is_greyscale_type(const pngColorMode *info)
{
	return info->colortype == LCT_GREY || info->colortype == LCT_GREY_ALPHA;
}

u32 png_is_alpha_type(const pngColorMode *info)
{
	return (info->colortype & 4) != 0; /*4 or 6*/
}

u32 png_is_palette_type(const pngColorMode *info)
{
	return info->colortype == LCT_PALETTE;
}

u32 png_has_palette_alpha(const pngColorMode *info)
{
	u32 i;
	for (i = 0; i != info->palettesize; ++i) {
		if (info->palette[i * 4 + 3] < 255)
			return 1;
	}
	return 0;
}

u32 png_can_have_alpha(const pngColorMode *info)
{
	return info->key_defined || png_is_alpha_type(info) || png_has_palette_alpha(info);
}

static u32 png_get_raw_size_lct(u32 w, u32 h, pngColorType colortype, u32 bitdepth)
{
	u32 bpp = png_get_bpp_lct(colortype, bitdepth);
	u32 n = (u32)w * (u32)h;
	return ((n / 8u) * bpp) + ((n & 7u) * bpp + 7u) / 8u;
}

u32 png_get_raw_size(u32 w, u32 h, const pngColorMode *color)
{
	return png_get_raw_size_lct(w, h, color->colortype, color->bitdepth);
}

#ifdef PNG_COMPILE_PNG

/*in an idat chunk, each scanline is a multiple of 8 bits, unlike the png output buffer,
and in addition has one extra byte per line: the filter byte. So this gives a larger
result than png_get_raw_size. Set h to 1 to get the size of 1 row including filter byte. */
static u32 png_get_raw_size_idat(u32 w, u32 h, u32 bpp)
{
	/* + 1 for the filter byte, and possibly plus padding bits per line. */
	/* Ignoring casts, the expression is equal to (w * bpp + 7) / 8 + 1, but avoids overflow of w * bpp */
	u32 line = ((u32)(w / 8u) * bpp) + 1u + ((w & 7u) * bpp + 7u) / 8u;
	return (u32)h * line;
}

#ifdef PNG_COMPILE_DECODER
/*Safely checks whether u32 overflow can be caused due to amount of pixels.
This check is overcautious rather than precise. If this check indicates no overflow,
you can safely compute in a u32 (but not an u32):
-(u32)w * (u32)h * 8
-amount of bytes in IDAT (including filter, padding and Adam7 bytes)
-amount of bytes in raw color model
Returns 1 if overflow possible, 0 if not.
*/
static int png_pixel_overflow(u32 w, u32 h, const pngColorMode *pngcolor,
			      const pngColorMode *rawcolor)
{
	u32 bpp = PNG_MAX(png_get_bpp(pngcolor), png_get_bpp(rawcolor));
	u32 numpixels, total;
	u32 line; /* bytes per line in worst case */

	if (png_mulofl((u32)w, (u32)h, &numpixels))
		return 1;
	if (png_mulofl(numpixels, 8, &total))
		return 1; /* bit pointer with 8-bit color, or 8 bytes per channel color */

	/* Bytes per scanline with the expression "(w / 8u) * bpp) + ((w & 7u) * bpp + 7u) / 8u" */
	if (png_mulofl((u32)(w / 8u), bpp, &line))
		return 1;
	if (png_addofl(line, ((w & 7u) * bpp + 7u) / 8u, &line))
		return 1;

	if (png_addofl(line, 5, &line))
		return 1; /* 5 bytes overhead per line: 1 filterbyte, 4 for Adam7 worst case */
	if (png_mulofl(line, h, &total))
		return 1; /* Total bytes in worst case */

	return 0; /* no overflow */
}
#endif /*PNG_COMPILE_DECODER*/
#endif /*PNG_COMPILE_PNG*/

#ifdef PNG_COMPILE_ANCILLARY_CHUNKS

static void pngUnknownChunks_init(pngInfo *info)
{
	u32 i;
	for (i = 0; i != 3; ++i)
		info->unknown_chunks_data[i] = 0;
	for (i = 0; i != 3; ++i)
		info->unknown_chunks_size[i] = 0;
}

static void pngUnknownChunks_cleanup(pngInfo *info)
{
	u32 i;
	for (i = 0; i != 3; ++i)
		png_free(info->unknown_chunks_data[i]);
}

static u32 pngUnknownChunks_copy(pngInfo *dest, const pngInfo *src)
{
	u32 i;

	pngUnknownChunks_cleanup(dest);

	for (i = 0; i != 3; ++i) {
		u32 j;
		dest->unknown_chunks_size[i] = src->unknown_chunks_size[i];
		dest->unknown_chunks_data[i] = (u8 *)png_malloc(src->unknown_chunks_size[i]);
		if (!dest->unknown_chunks_data[i] && dest->unknown_chunks_size[i])
			return 83; /*alloc fail*/
		for (j = 0; j < src->unknown_chunks_size[i]; ++j) {
			dest->unknown_chunks_data[i][j] = src->unknown_chunks_data[i][j];
		}
	}

	return 0;
}

/******************************************************************************/

static void pngText_init(pngInfo *info)
{
	info->text_num = 0;
	info->text_keys = NULL;
	info->text_strings = NULL;
}

static void pngText_cleanup(pngInfo *info)
{
	u32 i;
	for (i = 0; i != info->text_num; ++i) {
		string_cleanup(&info->text_keys[i]);
		string_cleanup(&info->text_strings[i]);
	}
	png_free(info->text_keys);
	png_free(info->text_strings);
}

static u32 pngText_copy(pngInfo *dest, const pngInfo *source)
{
	u32 i = 0;
	dest->text_keys = NULL;
	dest->text_strings = NULL;
	dest->text_num = 0;
	for (i = 0; i != source->text_num; ++i) {
		CERROR_TRY_RETURN(
			png_add_text(dest, source->text_keys[i], source->text_strings[i]));
	}
	return 0;
}

static u32 png_add_text_sized(pngInfo *info, const char *key, const char *str, u32 size)
{
	char **new_keys =
		(char **)(png_realloc(info->text_keys, sizeof(char *) * (info->text_num + 1)));
	char **new_strings =
		(char **)(png_realloc(info->text_strings, sizeof(char *) * (info->text_num + 1)));

	if (new_keys)
		info->text_keys = new_keys;
	if (new_strings)
		info->text_strings = new_strings;

	if (!new_keys || !new_strings)
		return 83; /*alloc fail*/

	++info->text_num;
	info->text_keys[info->text_num - 1] = alloc_string(key);
	info->text_strings[info->text_num - 1] = alloc_string_sized(str, size);
	if (!info->text_keys[info->text_num - 1] || !info->text_strings[info->text_num - 1])
		return 83; /*alloc fail*/

	return 0;
}

u32 png_add_text(pngInfo *info, const char *key, const char *str)
{
	return png_add_text_sized(info, key, str, png_strlen(str));
}

void png_clear_text(pngInfo *info)
{
	pngText_cleanup(info);
}

/******************************************************************************/

static void pngIText_init(pngInfo *info)
{
	info->itext_num = 0;
	info->itext_keys = NULL;
	info->itext_langtags = NULL;
	info->itext_transkeys = NULL;
	info->itext_strings = NULL;
}

static void pngIText_cleanup(pngInfo *info)
{
	u32 i;
	for (i = 0; i != info->itext_num; ++i) {
		string_cleanup(&info->itext_keys[i]);
		string_cleanup(&info->itext_langtags[i]);
		string_cleanup(&info->itext_transkeys[i]);
		string_cleanup(&info->itext_strings[i]);
	}
	png_free(info->itext_keys);
	png_free(info->itext_langtags);
	png_free(info->itext_transkeys);
	png_free(info->itext_strings);
}

static u32 pngIText_copy(pngInfo *dest, const pngInfo *source)
{
	u32 i = 0;
	dest->itext_keys = NULL;
	dest->itext_langtags = NULL;
	dest->itext_transkeys = NULL;
	dest->itext_strings = NULL;
	dest->itext_num = 0;
	for (i = 0; i != source->itext_num; ++i) {
		CERROR_TRY_RETURN(
			png_add_itext(dest, source->itext_keys[i], source->itext_langtags[i],
				      source->itext_transkeys[i], source->itext_strings[i]));
	}
	return 0;
}

void png_clear_itext(pngInfo *info)
{
	pngIText_cleanup(info);
}

static u32 png_add_itext_sized(pngInfo *info, const char *key, const char *langtag,
			       const char *transkey, const char *str, u32 size)
{
	char **new_keys =
		(char **)(png_realloc(info->itext_keys, sizeof(char *) * (info->itext_num + 1)));
	char **new_langtags = (char **)(png_realloc(info->itext_langtags,
						    sizeof(char *) * (info->itext_num + 1)));
	char **new_transkeys = (char **)(png_realloc(info->itext_transkeys,
						     sizeof(char *) * (info->itext_num + 1)));
	char **new_strings =
		(char **)(png_realloc(info->itext_strings, sizeof(char *) * (info->itext_num + 1)));

	if (new_keys)
		info->itext_keys = new_keys;
	if (new_langtags)
		info->itext_langtags = new_langtags;
	if (new_transkeys)
		info->itext_transkeys = new_transkeys;
	if (new_strings)
		info->itext_strings = new_strings;

	if (!new_keys || !new_langtags || !new_transkeys || !new_strings)
		return 83; /*alloc fail*/

	++info->itext_num;

	info->itext_keys[info->itext_num - 1] = alloc_string(key);
	info->itext_langtags[info->itext_num - 1] = alloc_string(langtag);
	info->itext_transkeys[info->itext_num - 1] = alloc_string(transkey);
	info->itext_strings[info->itext_num - 1] = alloc_string_sized(str, size);

	return 0;
}

u32 png_add_itext(pngInfo *info, const char *key, const char *langtag, const char *transkey,
		  const char *str)
{
	return png_add_itext_sized(info, key, langtag, transkey, str, png_strlen(str));
}

/* same as set but does not delete */
static u32 png_assign_icc(pngInfo *info, const char *name, const u8 *profile, u32 profile_size)
{
	if (profile_size == 0)
		return 100; /*invalid ICC profile size*/

	info->iccp_name = alloc_string(name);
	info->iccp_profile = (u8 *)png_malloc(profile_size);

	if (!info->iccp_name || !info->iccp_profile)
		return 83; /*alloc fail*/

	png_memcpy(info->iccp_profile, profile, profile_size);
	info->iccp_profile_size = profile_size;

	return 0; /*ok*/
}

u32 png_set_icc(pngInfo *info, const char *name, const u8 *profile, u32 profile_size)
{
	if (info->iccp_name)
		png_clear_icc(info);
	info->iccp_defined = 1;

	return png_assign_icc(info, name, profile, profile_size);
}

void png_clear_icc(pngInfo *info)
{
	string_cleanup(&info->iccp_name);
	png_free(info->iccp_profile);
	info->iccp_profile = NULL;
	info->iccp_profile_size = 0;
	info->iccp_defined = 0;
}
#endif /*PNG_COMPILE_ANCILLARY_CHUNKS*/

void png_info_init(pngInfo *info)
{
	png_color_mode_init(&info->color);
	info->interlace_method = 0;
	info->compression_method = 0;
	info->filter_method = 0;
#ifdef PNG_COMPILE_ANCILLARY_CHUNKS
	info->background_defined = 0;
	info->background_r = info->background_g = info->background_b = 0;

	pngText_init(info);
	pngIText_init(info);

	info->time_defined = 0;
	info->phys_defined = 0;

	info->gama_defined = 0;
	info->chrm_defined = 0;
	info->srgb_defined = 0;
	info->iccp_defined = 0;
	info->iccp_name = NULL;
	info->iccp_profile = NULL;

	pngUnknownChunks_init(info);
#endif /*PNG_COMPILE_ANCILLARY_CHUNKS*/
}

void png_info_cleanup(pngInfo *info)
{
	png_color_mode_cleanup(&info->color);
#ifdef PNG_COMPILE_ANCILLARY_CHUNKS
	pngText_cleanup(info);
	pngIText_cleanup(info);

	png_clear_icc(info);

	pngUnknownChunks_cleanup(info);
#endif /*PNG_COMPILE_ANCILLARY_CHUNKS*/
}

u32 png_info_copy(pngInfo *dest, const pngInfo *source)
{
	png_info_cleanup(dest);
	png_memcpy(dest, source, sizeof(pngInfo));
	png_color_mode_init(&dest->color);
	CERROR_TRY_RETURN(png_color_mode_copy(&dest->color, &source->color));

#ifdef PNG_COMPILE_ANCILLARY_CHUNKS
	CERROR_TRY_RETURN(pngText_copy(dest, source));
	CERROR_TRY_RETURN(pngIText_copy(dest, source));
	if (source->iccp_defined) {
		CERROR_TRY_RETURN(png_assign_icc(dest, source->iccp_name, source->iccp_profile,
						 source->iccp_profile_size));
	}

	pngUnknownChunks_init(dest);
	CERROR_TRY_RETURN(pngUnknownChunks_copy(dest, source));
#endif /*PNG_COMPILE_ANCILLARY_CHUNKS*/
	return 0;
}

/* ////////////////////////////////////////////////////////////////////////// */

/*index: bitgroup index, bits: bitgroup size(1, 2 or 4), in: bitgroup value, out: octet array to add bits to*/
static void addColorBits(u8 *out, u32 index, u32 bits, u32 in)
{
	u32 m = bits == 1 ? 7 : bits == 2 ? 3 : 1; /*8 / bits - 1*/
	/*p = the partial index in the byte, e.g. with 4 palettebits it is 0 for first half or 1 for second half*/
	u32 p = index & m;
	in &= (1u << bits) - 1u; /*filter out any other bits of the input value*/
	in = in << (bits * (m - p));
	if (p == 0)
		out[index * bits / 8u] = in;
	else
		out[index * bits / 8u] |= in;
}

typedef struct ColorTree ColorTree;

/*
One node of a color tree
This is the data structure used to count the number of unique colors and to get a palette
index for a color. It's like an octree, but because the alpha channel is used too, each
node has 16 instead of 8 children.
*/
struct ColorTree {
	ColorTree *children[16]; /*up to 16 pointers to ColorTree of next level*/
	int index; /*the payload. Only has a meaningful value if this is in the last level*/
};

static void color_tree_init(ColorTree *tree)
{
	png_memset(tree->children, 0, 16 * sizeof(*tree->children));
	tree->index = -1;
}

static void color_tree_cleanup(ColorTree *tree)
{
	int i;
	for (i = 0; i != 16; ++i) {
		if (tree->children[i]) {
			color_tree_cleanup(tree->children[i]);
			png_free(tree->children[i]);
		}
	}
}

/*returns -1 if color not present, its index otherwise*/
static int color_tree_get(ColorTree *tree, u8 r, u8 g, u8 b, u8 a)
{
	int bit = 0;
	for (bit = 0; bit < 8; ++bit) {
		int i = 8 * ((r >> bit) & 1) + 4 * ((g >> bit) & 1) + 2 * ((b >> bit) & 1) +
			1 * ((a >> bit) & 1);
		if (!tree->children[i])
			return -1;
		else
			tree = tree->children[i];
	}
	return tree ? tree->index : -1;
}

#ifdef PNG_COMPILE_ENCODER
static int color_tree_has(ColorTree *tree, u8 r, u8 g, u8 b, u8 a)
{
	return color_tree_get(tree, r, g, b, a) >= 0;
}
#endif /*PNG_COMPILE_ENCODER*/

/*color is not allowed to already exist.
Index should be >= 0 (it's signed to be compatible with using -1 for "doesn't exist")
Returns error code, or 0 if ok*/
static u32 color_tree_add(ColorTree *tree, u8 r, u8 g, u8 b, u8 a, u32 index)
{
	int bit;
	for (bit = 0; bit < 8; ++bit) {
		int i = 8 * ((r >> bit) & 1) + 4 * ((g >> bit) & 1) + 2 * ((b >> bit) & 1) +
			1 * ((a >> bit) & 1);
		if (!tree->children[i]) {
			tree->children[i] = (ColorTree *)png_malloc(sizeof(ColorTree));
			if (!tree->children[i])
				return 83; /*alloc fail*/
			color_tree_init(tree->children[i]);
		}
		tree = tree->children[i];
	}
	tree->index = (int)index;
	return 0;
}

/*put a pixel, given its RGBA color, into image of any color type*/
static u32 rgba8ToPixel(u8 *out, u32 i, const pngColorMode *mode, ColorTree *tree /*for palette*/,
			u8 r, u8 g, u8 b, u8 a)
{
	if (mode->colortype == LCT_GREY) {
		u8 gray = r; /*((u16)r + g + b) / 3u;*/
		if (mode->bitdepth == 8)
			out[i] = gray;
		else if (mode->bitdepth == 16)
			out[i * 2 + 0] = out[i * 2 + 1] = gray;
		else {
			/*take the most significant bits of gray*/
			gray = ((u32)gray >> (8u - mode->bitdepth)) & ((1u << mode->bitdepth) - 1u);
			addColorBits(out, i, mode->bitdepth, gray);
		}
	} else if (mode->colortype == LCT_RGB) {
		if (mode->bitdepth == 8) {
			out[i * 3 + 0] = r;
			out[i * 3 + 1] = g;
			out[i * 3 + 2] = b;
		} else {
			out[i * 6 + 0] = out[i * 6 + 1] = r;
			out[i * 6 + 2] = out[i * 6 + 3] = g;
			out[i * 6 + 4] = out[i * 6 + 5] = b;
		}
	} else if (mode->colortype == LCT_PALETTE) {
		int index = color_tree_get(tree, r, g, b, a);
		if (index < 0)
			return 82; /*color not in palette*/
		if (mode->bitdepth == 8)
			out[i] = index;
		else
			addColorBits(out, i, mode->bitdepth, (u32)index);
	} else if (mode->colortype == LCT_GREY_ALPHA) {
		u8 gray = r; /*((u16)r + g + b) / 3u;*/
		if (mode->bitdepth == 8) {
			out[i * 2 + 0] = gray;
			out[i * 2 + 1] = a;
		} else if (mode->bitdepth == 16) {
			out[i * 4 + 0] = out[i * 4 + 1] = gray;
			out[i * 4 + 2] = out[i * 4 + 3] = a;
		}
	} else if (mode->colortype == LCT_RGBA) {
		if (mode->bitdepth == 8) {
			out[i * 4 + 0] = r;
			out[i * 4 + 1] = g;
			out[i * 4 + 2] = b;
			out[i * 4 + 3] = a;
		} else {
			out[i * 8 + 0] = out[i * 8 + 1] = r;
			out[i * 8 + 2] = out[i * 8 + 3] = g;
			out[i * 8 + 4] = out[i * 8 + 5] = b;
			out[i * 8 + 6] = out[i * 8 + 7] = a;
		}
	}

	return 0; /*no error*/
}

/*put a pixel, given its RGBA16 color, into image of any color 16-bitdepth type*/
static void rgba16ToPixel(u8 *out, u32 i, const pngColorMode *mode, u16 r, u16 g, u16 b, u16 a)
{
	if (mode->colortype == LCT_GREY) {
		u16 gray = r; /*((u32)r + g + b) / 3u;*/
		out[i * 2 + 0] = (gray >> 8) & 255;
		out[i * 2 + 1] = gray & 255;
	} else if (mode->colortype == LCT_RGB) {
		out[i * 6 + 0] = (r >> 8) & 255;
		out[i * 6 + 1] = r & 255;
		out[i * 6 + 2] = (g >> 8) & 255;
		out[i * 6 + 3] = g & 255;
		out[i * 6 + 4] = (b >> 8) & 255;
		out[i * 6 + 5] = b & 255;
	} else if (mode->colortype == LCT_GREY_ALPHA) {
		u16 gray = r; /*((u32)r + g + b) / 3u;*/
		out[i * 4 + 0] = (gray >> 8) & 255;
		out[i * 4 + 1] = gray & 255;
		out[i * 4 + 2] = (a >> 8) & 255;
		out[i * 4 + 3] = a & 255;
	} else if (mode->colortype == LCT_RGBA) {
		out[i * 8 + 0] = (r >> 8) & 255;
		out[i * 8 + 1] = r & 255;
		out[i * 8 + 2] = (g >> 8) & 255;
		out[i * 8 + 3] = g & 255;
		out[i * 8 + 4] = (b >> 8) & 255;
		out[i * 8 + 5] = b & 255;
		out[i * 8 + 6] = (a >> 8) & 255;
		out[i * 8 + 7] = a & 255;
	}
}

/*Get RGBA8 color of pixel with index i (y * width + x) from the raw image with given color type.*/
static void getPixelColorRGBA8(u8 *r, u8 *g, u8 *b, u8 *a, const u8 *in, u32 i,
			       const pngColorMode *mode)
{
	if (mode->colortype == LCT_GREY) {
		if (mode->bitdepth == 8) {
			*r = *g = *b = in[i];
			if (mode->key_defined && *r == mode->key_r)
				*a = 0;
			else
				*a = 255;
		} else if (mode->bitdepth == 16) {
			*r = *g = *b = in[i * 2 + 0];
			if (mode->key_defined &&
			    256U * in[i * 2 + 0] + in[i * 2 + 1] == mode->key_r)
				*a = 0;
			else
				*a = 255;
		} else {
			u32 highest = ((1U << mode->bitdepth) -
				       1U); /*highest possible value for this bit depth*/
			u32 j = i * mode->bitdepth;
			u32 value = readBitsFromReversedStream(&j, in, mode->bitdepth);

			if (highest)
				*r = *g = *b = (value * 255) / highest;
			else
				*r = *g = *b = value;

			if (mode->key_defined && value == mode->key_r)
				*a = 0;
			else
				*a = 255;
		}
	} else if (mode->colortype == LCT_RGB) {
		if (mode->bitdepth == 8) {
			*r = in[i * 3 + 0];
			*g = in[i * 3 + 1];
			*b = in[i * 3 + 2];
			if (mode->key_defined && *r == mode->key_r && *g == mode->key_g &&
			    *b == mode->key_b)
				*a = 0;
			else
				*a = 255;
		} else {
			*r = in[i * 6 + 0];
			*g = in[i * 6 + 2];
			*b = in[i * 6 + 4];
			if (mode->key_defined &&
			    256U * in[i * 6 + 0] + in[i * 6 + 1] == mode->key_r &&
			    256U * in[i * 6 + 2] + in[i * 6 + 3] == mode->key_g &&
			    256U * in[i * 6 + 4] + in[i * 6 + 5] == mode->key_b)
				*a = 0;
			else
				*a = 255;
		}
	} else if (mode->colortype == LCT_PALETTE) {
		u32 index;
		if (mode->bitdepth == 8)
			index = in[i];
		else {
			u32 j = i * mode->bitdepth;
			index = readBitsFromReversedStream(&j, in, mode->bitdepth);
		}
		/*out of bounds of palette not checked: see png_color_mode_alloc_palette.*/
		*r = mode->palette[index * 4 + 0];
		*g = mode->palette[index * 4 + 1];
		*b = mode->palette[index * 4 + 2];
		*a = mode->palette[index * 4 + 3];
	} else if (mode->colortype == LCT_GREY_ALPHA) {
		if (mode->bitdepth == 8) {
			*r = *g = *b = in[i * 2 + 0];
			*a = in[i * 2 + 1];
		} else {
			*r = *g = *b = in[i * 4 + 0];
			*a = in[i * 4 + 2];
		}
	} else if (mode->colortype == LCT_RGBA) {
		if (mode->bitdepth == 8) {
			*r = in[i * 4 + 0];
			*g = in[i * 4 + 1];
			*b = in[i * 4 + 2];
			*a = in[i * 4 + 3];
		} else {
			*r = in[i * 8 + 0];
			*g = in[i * 8 + 2];
			*b = in[i * 8 + 4];
			*a = in[i * 8 + 6];
		}
	}
}

/*Similar to getPixelColorRGBA8, but with all the for loops inside of the color
mode test cases, optimized to convert the colors much faster, when converting
to the common case of RGBA with 8 bit per channel. buffer must be RGBA with
enough memory.*/
static void getPixelColorsRGBA8(u8 *PNG_RESTRICT buffer, u32 numpixels, const u8 *PNG_RESTRICT in,
				const pngColorMode *mode)
{
	u32 num_channels = 4;
	u32 i;
	if (mode->colortype == LCT_GREY) {
		if (mode->bitdepth == 8) {
			for (i = 0; i != numpixels; ++i, buffer += num_channels) {
				buffer[0] = buffer[1] = buffer[2] = in[i];
				buffer[3] = 255;
			}
			if (mode->key_defined) {
				buffer -= numpixels * num_channels;
				for (i = 0; i != numpixels; ++i, buffer += num_channels) {
					if (buffer[0] == mode->key_r)
						buffer[3] = 0;
				}
			}
		} else if (mode->bitdepth == 16) {
			for (i = 0; i != numpixels; ++i, buffer += num_channels) {
				buffer[0] = buffer[1] = buffer[2] = in[i * 2];
				buffer[3] =
					mode->key_defined && 256U * in[i * 2 + 0] + in[i * 2 + 1] ==
								     mode->key_r ?
						      0 :
						      255;
			}
		} else {
			u32 highest = ((1U << mode->bitdepth) -
				       1U); /*highest possible value for this bit depth*/
			u32 j = 0;
			for (i = 0; i != numpixels; ++i, buffer += num_channels) {
				u32 value = readBitsFromReversedStream(&j, in, mode->bitdepth);
				buffer[0] = buffer[1] = buffer[2] = (value * 255) / highest;
				buffer[3] = mode->key_defined && value == mode->key_r ? 0 : 255;
			}
		}
	} else if (mode->colortype == LCT_RGB) {
		if (mode->bitdepth == 8) {
			for (i = 0; i != numpixels; ++i, buffer += num_channels) {
				png_memcpy(buffer, &in[i * 3], 3);
				buffer[3] = 255;
			}
			if (mode->key_defined) {
				buffer -= numpixels * num_channels;
				for (i = 0; i != numpixels; ++i, buffer += num_channels) {
					if (buffer[0] == mode->key_r && buffer[1] == mode->key_g &&
					    buffer[2] == mode->key_b)
						buffer[3] = 0;
				}
			}
		} else {
			for (i = 0; i != numpixels; ++i, buffer += num_channels) {
				buffer[0] = in[i * 6 + 0];
				buffer[1] = in[i * 6 + 2];
				buffer[2] = in[i * 6 + 4];
				buffer[3] = mode->key_defined &&
							    256U * in[i * 6 + 0] + in[i * 6 + 1] ==
								    mode->key_r &&
							    256U * in[i * 6 + 2] + in[i * 6 + 3] ==
								    mode->key_g &&
							    256U * in[i * 6 + 4] + in[i * 6 + 5] ==
								    mode->key_b ?
							  0 :
							  255;
			}
		}
	} else if (mode->colortype == LCT_PALETTE) {
		if (mode->bitdepth == 8) {
			for (i = 0; i != numpixels; ++i, buffer += num_channels) {
				u32 index = in[i];
				/*out of bounds of palette not checked: see png_color_mode_alloc_palette.*/
				png_memcpy(buffer, &mode->palette[index * 4], 4);
			}
		} else {
			u32 j = 0;
			for (i = 0; i != numpixels; ++i, buffer += num_channels) {
				u32 index = readBitsFromReversedStream(&j, in, mode->bitdepth);
				/*out of bounds of palette not checked: see png_color_mode_alloc_palette.*/
				png_memcpy(buffer, &mode->palette[index * 4], 4);
			}
		}
	} else if (mode->colortype == LCT_GREY_ALPHA) {
		if (mode->bitdepth == 8) {
			for (i = 0; i != numpixels; ++i, buffer += num_channels) {
				buffer[0] = buffer[1] = buffer[2] = in[i * 2 + 0];
				buffer[3] = in[i * 2 + 1];
			}
		} else {
			for (i = 0; i != numpixels; ++i, buffer += num_channels) {
				buffer[0] = buffer[1] = buffer[2] = in[i * 4 + 0];
				buffer[3] = in[i * 4 + 2];
			}
		}
	} else if (mode->colortype == LCT_RGBA) {
		if (mode->bitdepth == 8) {
			png_memcpy(buffer, in, numpixels * 4);
		} else {
			for (i = 0; i != numpixels; ++i, buffer += num_channels) {
				buffer[0] = in[i * 8 + 0];
				buffer[1] = in[i * 8 + 2];
				buffer[2] = in[i * 8 + 4];
				buffer[3] = in[i * 8 + 6];
			}
		}
	}
}

/*Similar to getPixelColorsRGBA8, but with 3-channel RGB output.*/
static void getPixelColorsRGB8(u8 *PNG_RESTRICT buffer, u32 numpixels, const u8 *PNG_RESTRICT in,
			       const pngColorMode *mode)
{
	const u32 num_channels = 3;
	u32 i;
	if (mode->colortype == LCT_GREY) {
		if (mode->bitdepth == 8) {
			for (i = 0; i != numpixels; ++i, buffer += num_channels) {
				buffer[0] = buffer[1] = buffer[2] = in[i];
			}
		} else if (mode->bitdepth == 16) {
			for (i = 0; i != numpixels; ++i, buffer += num_channels) {
				buffer[0] = buffer[1] = buffer[2] = in[i * 2];
			}
		} else {
			u32 highest = ((1U << mode->bitdepth) -
				       1U); /*highest possible value for this bit depth*/
			u32 j = 0;
			for (i = 0; i != numpixels; ++i, buffer += num_channels) {
				u32 value = readBitsFromReversedStream(&j, in, mode->bitdepth);
				buffer[0] = buffer[1] = buffer[2] = (value * 255) / highest;
			}
		}
	} else if (mode->colortype == LCT_RGB) {
		if (mode->bitdepth == 8) {
			png_memcpy(buffer, in, numpixels * 3);
		} else {
			for (i = 0; i != numpixels; ++i, buffer += num_channels) {
				buffer[0] = in[i * 6 + 0];
				buffer[1] = in[i * 6 + 2];
				buffer[2] = in[i * 6 + 4];
			}
		}
	} else if (mode->colortype == LCT_PALETTE) {
		if (mode->bitdepth == 8) {
			for (i = 0; i != numpixels; ++i, buffer += num_channels) {
				u32 index = in[i];
				/*out of bounds of palette not checked: see png_color_mode_alloc_palette.*/
				png_memcpy(buffer, &mode->palette[index * 4], 3);
			}
		} else {
			u32 j = 0;
			for (i = 0; i != numpixels; ++i, buffer += num_channels) {
				u32 index = readBitsFromReversedStream(&j, in, mode->bitdepth);
				/*out of bounds of palette not checked: see png_color_mode_alloc_palette.*/
				png_memcpy(buffer, &mode->palette[index * 4], 3);
			}
		}
	} else if (mode->colortype == LCT_GREY_ALPHA) {
		if (mode->bitdepth == 8) {
			for (i = 0; i != numpixels; ++i, buffer += num_channels) {
				buffer[0] = buffer[1] = buffer[2] = in[i * 2 + 0];
			}
		} else {
			for (i = 0; i != numpixels; ++i, buffer += num_channels) {
				buffer[0] = buffer[1] = buffer[2] = in[i * 4 + 0];
			}
		}
	} else if (mode->colortype == LCT_RGBA) {
		if (mode->bitdepth == 8) {
			for (i = 0; i != numpixels; ++i, buffer += num_channels) {
				png_memcpy(buffer, &in[i * 4], 3);
			}
		} else {
			for (i = 0; i != numpixels; ++i, buffer += num_channels) {
				buffer[0] = in[i * 8 + 0];
				buffer[1] = in[i * 8 + 2];
				buffer[2] = in[i * 8 + 4];
			}
		}
	}
}

/*Get RGBA16 color of pixel with index i (y * width + x) from the raw image with
given color type, but the given color type must be 16-bit itself.*/
static void getPixelColorRGBA16(u16 *r, u16 *g, u16 *b, u16 *a, const u8 *in, u32 i,
				const pngColorMode *mode)
{
	if (mode->colortype == LCT_GREY) {
		*r = *g = *b = 256 * in[i * 2 + 0] + in[i * 2 + 1];
		if (mode->key_defined && 256U * in[i * 2 + 0] + in[i * 2 + 1] == mode->key_r)
			*a = 0;
		else
			*a = 65535;
	} else if (mode->colortype == LCT_RGB) {
		*r = 256u * in[i * 6 + 0] + in[i * 6 + 1];
		*g = 256u * in[i * 6 + 2] + in[i * 6 + 3];
		*b = 256u * in[i * 6 + 4] + in[i * 6 + 5];
		if (mode->key_defined && 256u * in[i * 6 + 0] + in[i * 6 + 1] == mode->key_r &&
		    256u * in[i * 6 + 2] + in[i * 6 + 3] == mode->key_g &&
		    256u * in[i * 6 + 4] + in[i * 6 + 5] == mode->key_b)
			*a = 0;
		else
			*a = 65535;
	} else if (mode->colortype == LCT_GREY_ALPHA) {
		*r = *g = *b = 256u * in[i * 4 + 0] + in[i * 4 + 1];
		*a = 256u * in[i * 4 + 2] + in[i * 4 + 3];
	} else if (mode->colortype == LCT_RGBA) {
		*r = 256u * in[i * 8 + 0] + in[i * 8 + 1];
		*g = 256u * in[i * 8 + 2] + in[i * 8 + 3];
		*b = 256u * in[i * 8 + 4] + in[i * 8 + 5];
		*a = 256u * in[i * 8 + 6] + in[i * 8 + 7];
	}
}

u32 png_convert(u8 *out, const u8 *in, const pngColorMode *mode_out, const pngColorMode *mode_in,
		u32 w, u32 h)
{
	u32 i;
	ColorTree tree;
	u32 numpixels = (u32)w * (u32)h;
	u32 error = 0;

	if (mode_in->colortype == LCT_PALETTE && !mode_in->palette) {
		return 107; /* error: must provide palette if input mode is palette */
	}

	if (png_color_mode_equal(mode_out, mode_in)) {
		u32 numbytes = png_get_raw_size(w, h, mode_in);
		png_memcpy(out, in, numbytes);
		return 0;
	}

	if (mode_out->colortype == LCT_PALETTE) {
		u32 palettesize = mode_out->palettesize;
		const u8 *palette = mode_out->palette;
		u32 palsize = (u32)1u << mode_out->bitdepth;
		/*if the user specified output palette but did not give the values, assume
    they want the values of the input color type (assuming that one is palette).
    Note that we never create a new palette ourselves.*/
		if (palettesize == 0) {
			palettesize = mode_in->palettesize;
			palette = mode_in->palette;
			/*if the input was also palette with same bitdepth, then the color types are also
      equal, so copy literally. This to preserve the exact indices that were in the PNG
      even in case there are duplicate colors in the palette.*/
			if (mode_in->colortype == LCT_PALETTE &&
			    mode_in->bitdepth == mode_out->bitdepth) {
				u32 numbytes = png_get_raw_size(w, h, mode_in);
				png_memcpy(out, in, numbytes);
				return 0;
			}
		}
		if (palettesize < palsize)
			palsize = palettesize;
		color_tree_init(&tree);
		for (i = 0; i != palsize; ++i) {
			const u8 *p = &palette[i * 4];
			error = color_tree_add(&tree, p[0], p[1], p[2], p[3], (u32)i);
			if (error)
				break;
		}
	}

	if (!error) {
		if (mode_in->bitdepth == 16 && mode_out->bitdepth == 16) {
			for (i = 0; i != numpixels; ++i) {
				u16 r = 0, g = 0, b = 0, a = 0;
				getPixelColorRGBA16(&r, &g, &b, &a, in, i, mode_in);
				rgba16ToPixel(out, i, mode_out, r, g, b, a);
			}
		} else if (mode_out->bitdepth == 8 && mode_out->colortype == LCT_RGBA) {
			getPixelColorsRGBA8(out, numpixels, in, mode_in);
		} else if (mode_out->bitdepth == 8 && mode_out->colortype == LCT_RGB) {
			getPixelColorsRGB8(out, numpixels, in, mode_in);
		} else {
			u8 r = 0, g = 0, b = 0, a = 0;
			for (i = 0; i != numpixels; ++i) {
				getPixelColorRGBA8(&r, &g, &b, &a, in, i, mode_in);
				error = rgba8ToPixel(out, i, mode_out, &tree, r, g, b, a);
				if (error)
					break;
			}
		}
	}

	if (mode_out->colortype == LCT_PALETTE) {
		color_tree_cleanup(&tree);
	}

	return error;
}

#ifdef PNG_COMPILE_ENCODER

/* Converts a single rgb color without alpha from one type to another, color bits truncated to
their bitdepth. In case of single channel (gray or palette), only the r channel is used. Slow
function, do not use to process all pixels of an image. Alpha channel not supported on purpose:
this is for bKGD, supporting alpha may prevent it from finding a color in the palette, from the
specification it looks like bKGD should ignore the alpha values of the palette since it can use
any palette index but doesn't have an alpha channel. Idem with ignoring color key. */
static u32 png_convert_rgb(u32 *r_out, u32 *g_out, u32 *b_out, u32 r_in, u32 g_in, u32 b_in,
			   const pngColorMode *mode_out, const pngColorMode *mode_in)
{
	u32 r = 0, g = 0, b = 0;
	u32 mul = 65535 / ((1u << mode_in->bitdepth) - 1u); /*65535, 21845, 4369, 257, 1*/
	u32 shift = 16 - mode_out->bitdepth;

	if (mode_in->colortype == LCT_GREY || mode_in->colortype == LCT_GREY_ALPHA) {
		r = g = b = r_in * mul;
	} else if (mode_in->colortype == LCT_RGB || mode_in->colortype == LCT_RGBA) {
		r = r_in * mul;
		g = g_in * mul;
		b = b_in * mul;
	} else if (mode_in->colortype == LCT_PALETTE) {
		if (r_in >= mode_in->palettesize)
			return 82;
		r = mode_in->palette[r_in * 4 + 0] * 257u;
		g = mode_in->palette[r_in * 4 + 1] * 257u;
		b = mode_in->palette[r_in * 4 + 2] * 257u;
	} else {
		return 31;
	}

	/* now convert to output format */
	if (mode_out->colortype == LCT_GREY || mode_out->colortype == LCT_GREY_ALPHA) {
		*r_out = r >> shift;
	} else if (mode_out->colortype == LCT_RGB || mode_out->colortype == LCT_RGBA) {
		*r_out = r >> shift;
		*g_out = g >> shift;
		*b_out = b >> shift;
	} else if (mode_out->colortype == LCT_PALETTE) {
		u32 i;
		/* a 16-bit color cannot be in the palette */
		if ((r >> 8) != (r & 255) || (g >> 8) != (g & 255) || (b >> 8) != (b & 255))
			return 82;
		for (i = 0; i < mode_out->palettesize; i++) {
			u32 j = i * 4;
			if ((r >> 8) == mode_out->palette[j + 0] &&
			    (g >> 8) == mode_out->palette[j + 1] &&
			    (b >> 8) == mode_out->palette[j + 2]) {
				*r_out = i;
				return 0;
			}
		}
		return 82;
	} else {
		return 31;
	}

	return 0;
}

void png_color_stats_init(pngColorStats *stats)
{
	/*stats*/
	stats->colored = 0;
	stats->key = 0;
	stats->key_r = stats->key_g = stats->key_b = 0;
	stats->alpha = 0;
	stats->numcolors = 0;
	stats->bits = 1;
	stats->numpixels = 0;
	/*settings*/
	stats->allow_palette = 1;
	stats->allow_greyscale = 1;
}

/*function used for debug purposes with C++*/
/*void printColorStats(pngColorStats* p) {
  std::cout << "colored: " << (int)p->colored << ", ";
  std::cout << "key: " << (int)p->key << ", ";
  std::cout << "key_r: " << (int)p->key_r << ", ";
  std::cout << "key_g: " << (int)p->key_g << ", ";
  std::cout << "key_b: " << (int)p->key_b << ", ";
  std::cout << "alpha: " << (int)p->alpha << ", ";
  std::cout << "numcolors: " << (int)p->numcolors << ", ";
  std::cout << "bits: " << (int)p->bits << std::endl;
}*/

/*Returns how many bits needed to represent given value (max 8 bit)*/
static u32 getValueRequiredBits(u8 value)
{
	if (value == 0 || value == 255)
		return 1;
	/*The scaling of 2-bit and 4-bit values uses multiples of 85 and 17*/
	if (value % 17 == 0)
		return value % 85 == 0 ? 2 : 4;
	return 8;
}

/*stats must already have been inited. */
u32 png_compute_color_stats(pngColorStats *stats, const u8 *in, u32 w, u32 h,
			    const pngColorMode *mode_in)
{
	u32 i;
	ColorTree tree;
	u32 numpixels = (u32)w * (u32)h;
	u32 error = 0;

	/* mark things as done already if it would be impossible to have a more expensive case */
	u32 colored_done = png_is_greyscale_type(mode_in) ? 1 : 0;
	u32 alpha_done = png_can_have_alpha(mode_in) ? 0 : 1;
	u32 numcolors_done = 0;
	u32 bpp = png_get_bpp(mode_in);
	u32 bits_done = (stats->bits == 1 && bpp == 1) ? 1 : 0;
	u32 sixteen = 0; /* whether the input image is 16 bit */
	u32 maxnumcolors = 257;
	if (bpp <= 8)
		maxnumcolors = PNG_MIN(257, stats->numcolors + (1u << bpp));

	stats->numpixels += numpixels;

	/*if palette not allowed, no need to compute numcolors*/
	if (!stats->allow_palette)
		numcolors_done = 1;

	color_tree_init(&tree);

	/*If the stats was already filled in from previous data, fill its palette in tree
  and mark things as done already if we know they are the most expensive case already*/
	if (stats->alpha)
		alpha_done = 1;
	if (stats->colored)
		colored_done = 1;
	if (stats->bits == 16)
		numcolors_done = 1;
	if (stats->bits >= bpp)
		bits_done = 1;
	if (stats->numcolors >= maxnumcolors)
		numcolors_done = 1;

	if (!numcolors_done) {
		for (i = 0; i < stats->numcolors; i++) {
			const u8 *color = &stats->palette[i * 4];
			error = color_tree_add(&tree, color[0], color[1], color[2], color[3], i);
			if (error)
				goto cleanup;
		}
	}

	/*Check if the 16-bit input is truly 16-bit*/
	if (mode_in->bitdepth == 16 && !sixteen) {
		u16 r = 0, g = 0, b = 0, a = 0;
		for (i = 0; i != numpixels; ++i) {
			getPixelColorRGBA16(&r, &g, &b, &a, in, i, mode_in);
			if ((r & 255) != ((r >> 8) & 255) || (g & 255) != ((g >> 8) & 255) ||
			    (b & 255) != ((b >> 8) & 255) ||
			    (a & 255) != ((a >> 8) & 255)) /*first and second byte differ*/ {
				stats->bits = 16;
				sixteen = 1;
				bits_done = 1;
				numcolors_done =
					1; /*counting colors no longer useful, palette doesn't support 16-bit*/
				break;
			}
		}
	}

	if (sixteen) {
		u16 r = 0, g = 0, b = 0, a = 0;

		for (i = 0; i != numpixels; ++i) {
			getPixelColorRGBA16(&r, &g, &b, &a, in, i, mode_in);

			if (!colored_done && (r != g || r != b)) {
				stats->colored = 1;
				colored_done = 1;
			}

			if (!alpha_done) {
				u32 matchkey = (r == stats->key_r && g == stats->key_g &&
						b == stats->key_b);
				if (a != 65535 && (a != 0 || (stats->key && !matchkey))) {
					stats->alpha = 1;
					stats->key = 0;
					alpha_done = 1;
				} else if (a == 0 && !stats->alpha && !stats->key) {
					stats->key = 1;
					stats->key_r = r;
					stats->key_g = g;
					stats->key_b = b;
				} else if (a == 65535 && stats->key && matchkey) {
					/* Color key cannot be used if an opaque pixel also has that RGB color. */
					stats->alpha = 1;
					stats->key = 0;
					alpha_done = 1;
				}
			}
			if (alpha_done && numcolors_done && colored_done && bits_done)
				break;
		}

		if (stats->key && !stats->alpha) {
			for (i = 0; i != numpixels; ++i) {
				getPixelColorRGBA16(&r, &g, &b, &a, in, i, mode_in);
				if (a != 0 && r == stats->key_r && g == stats->key_g &&
				    b == stats->key_b) {
					/* Color key cannot be used if an opaque pixel also has that RGB color. */
					stats->alpha = 1;
					stats->key = 0;
					alpha_done = 1;
				}
			}
		}
	} else /* < 16-bit */ {
		u8 r = 0, g = 0, b = 0, a = 0;
		for (i = 0; i != numpixels; ++i) {
			getPixelColorRGBA8(&r, &g, &b, &a, in, i, mode_in);

			if (!bits_done && stats->bits < 8) {
				/*only r is checked, < 8 bits is only relevant for grayscale*/
				u32 bits = getValueRequiredBits(r);
				if (bits > stats->bits)
					stats->bits = bits;
			}
			bits_done = (stats->bits >= bpp);

			if (!colored_done && (r != g || r != b)) {
				stats->colored = 1;
				colored_done = 1;
				if (stats->bits < 8)
					stats->bits =
						8; /*PNG has no colored modes with less than 8-bit per channel*/
			}

			if (!alpha_done) {
				u32 matchkey = (r == stats->key_r && g == stats->key_g &&
						b == stats->key_b);
				if (a != 255 && (a != 0 || (stats->key && !matchkey))) {
					stats->alpha = 1;
					stats->key = 0;
					alpha_done = 1;
					if (stats->bits < 8)
						stats->bits =
							8; /*PNG has no alphachannel modes with less than 8-bit per channel*/
				} else if (a == 0 && !stats->alpha && !stats->key) {
					stats->key = 1;
					stats->key_r = r;
					stats->key_g = g;
					stats->key_b = b;
				} else if (a == 255 && stats->key && matchkey) {
					/* Color key cannot be used if an opaque pixel also has that RGB color. */
					stats->alpha = 1;
					stats->key = 0;
					alpha_done = 1;
					if (stats->bits < 8)
						stats->bits =
							8; /*PNG has no alphachannel modes with less than 8-bit per channel*/
				}
			}

			if (!numcolors_done) {
				if (!color_tree_has(&tree, r, g, b, a)) {
					error = color_tree_add(&tree, r, g, b, a, stats->numcolors);
					if (error)
						goto cleanup;
					if (stats->numcolors < 256) {
						u8 *p = stats->palette;
						u32 n = stats->numcolors;
						p[n * 4 + 0] = r;
						p[n * 4 + 1] = g;
						p[n * 4 + 2] = b;
						p[n * 4 + 3] = a;
					}
					++stats->numcolors;
					numcolors_done = stats->numcolors >= maxnumcolors;
				}
			}

			if (alpha_done && numcolors_done && colored_done && bits_done)
				break;
		}

		if (stats->key && !stats->alpha) {
			for (i = 0; i != numpixels; ++i) {
				getPixelColorRGBA8(&r, &g, &b, &a, in, i, mode_in);
				if (a != 0 && r == stats->key_r && g == stats->key_g &&
				    b == stats->key_b) {
					/* Color key cannot be used if an opaque pixel also has that RGB color. */
					stats->alpha = 1;
					stats->key = 0;
					alpha_done = 1;
					if (stats->bits < 8)
						stats->bits =
							8; /*PNG has no alphachannel modes with less than 8-bit per channel*/
				}
			}
		}

		/*make the stats's key always 16-bit for consistency - repeat each byte twice*/
		stats->key_r += (stats->key_r << 8);
		stats->key_g += (stats->key_g << 8);
		stats->key_b += (stats->key_b << 8);
	}

cleanup:
	color_tree_cleanup(&tree);
	return error;
}

#ifdef PNG_COMPILE_ANCILLARY_CHUNKS
/*Adds a single color to the color stats. The stats must already have been inited. The color must be given as 16-bit
(with 2 bytes repeating for 8-bit and 65535 for opaque alpha channel). This function is expensive, do not call it for
all pixels of an image but only for a few additional values. */
static u32 png_color_stats_add(pngColorStats *stats, u32 r, u32 g, u32 b, u32 a)
{
	u32 error = 0;
	u8 image[8];
	pngColorMode mode;
	png_color_mode_init(&mode);
	image[0] = r >> 8;
	image[1] = r;
	image[2] = g >> 8;
	image[3] = g;
	image[4] = b >> 8;
	image[5] = b;
	image[6] = a >> 8;
	image[7] = a;
	mode.bitdepth = 16;
	mode.colortype = LCT_RGBA;
	error = png_compute_color_stats(stats, image, 1, 1, &mode);
	png_color_mode_cleanup(&mode);
	return error;
}
#endif /*PNG_COMPILE_ANCILLARY_CHUNKS*/

/*Computes a minimal PNG color model that can contain all colors as indicated by the stats.
The stats should be computed with png_compute_color_stats.
mode_in is raw color profile of the image the stats were computed on, to copy palette order from when relevant.
Minimal PNG color model means the color type and bit depth that gives smallest amount of bits in the output image,
e.g. gray if only grayscale pixels, palette if less than 256 colors, color key if only single transparent color, ...
This is used if auto_convert is enabled (it is by default).
*/
static u32 auto_choose_color(pngColorMode *mode_out, const pngColorMode *mode_in,
			     const pngColorStats *stats)
{
	u32 error = 0;
	u32 palettebits;
	u32 i, n;
	u32 numpixels = stats->numpixels;
	u32 palette_ok, gray_ok;

	u32 alpha = stats->alpha;
	u32 key = stats->key;
	u32 bits = stats->bits;

	mode_out->key_defined = 0;

	if (key && numpixels <= 16) {
		alpha = 1; /*too few pixels to justify tRNS chunk overhead*/
		key = 0;
		if (bits < 8)
			bits = 8; /*PNG has no alphachannel modes with less than 8-bit per channel*/
	}

	gray_ok = !stats->colored;
	if (!stats->allow_greyscale)
		gray_ok = 0;
	if (!gray_ok && bits < 8)
		bits = 8;

	n = stats->numcolors;
	palettebits = n <= 2 ? 1 : (n <= 4 ? 2 : (n <= 16 ? 4 : 8));
	palette_ok =
		n <= 256 && bits <= 8 && n != 0; /*n==0 means likely numcolors wasn't computed*/
	if (numpixels < n * 2)
		palette_ok = 0; /*don't add palette overhead if image has only a few pixels*/
	if (gray_ok && !alpha && bits <= palettebits)
		palette_ok = 0; /*gray is less overhead*/
	if (!stats->allow_palette)
		palette_ok = 0;

	if (palette_ok) {
		const u8 *p = stats->palette;
		png_palette_clear(mode_out); /*remove potential earlier palette*/
		for (i = 0; i != stats->numcolors; ++i) {
			error = png_palette_add(mode_out, p[i * 4 + 0], p[i * 4 + 1], p[i * 4 + 2],
						p[i * 4 + 3]);
			if (error)
				break;
		}

		mode_out->colortype = LCT_PALETTE;
		mode_out->bitdepth = palettebits;

		if (mode_in->colortype == LCT_PALETTE &&
		    mode_in->palettesize >= mode_out->palettesize &&
		    mode_in->bitdepth == mode_out->bitdepth) {
			/*If input should have same palette colors, keep original to preserve its order and prevent conversion*/
			png_color_mode_cleanup(mode_out);
			png_color_mode_copy(mode_out, mode_in);
		}
	} else /*8-bit or 16-bit per channel*/ {
		mode_out->bitdepth = bits;
		mode_out->colortype = alpha ? (gray_ok ? LCT_GREY_ALPHA : LCT_RGBA) :
						    (gray_ok ? LCT_GREY : LCT_RGB);
		if (key) {
			u32 mask = (1u << mode_out->bitdepth) -
				   1u; /*stats always uses 16-bit, mask converts it*/
			mode_out->key_r = stats->key_r & mask;
			mode_out->key_g = stats->key_g & mask;
			mode_out->key_b = stats->key_b & mask;
			mode_out->key_defined = 1;
		}
	}

	return error;
}

#endif /* #ifdef PNG_COMPILE_ENCODER */

/*
Paeth predictor, used by PNG filter type 4
The parameters are of type short, but should come from u8s, the shorts
are only needed to make the paeth calculation correct.
*/
static u8 paethPredictor(short a, short b, short c)
{
	short pa = PNG_ABS(b - c);
	short pb = PNG_ABS(a - c);
	short pc = PNG_ABS(a + b - c - c);
	/* return input value associated with smallest of pa, pb, pc (with certain priority if equal) */
	if (pb < pa) {
		a = b;
		pa = pb;
	}
	return (pc < pa) ? c : a;
}

/*shared values used by multiple Adam7 related functions*/

static const u32 ADAM7_IX[7] = { 0, 4, 0, 2, 0, 1, 0 }; /*x start values*/
static const u32 ADAM7_IY[7] = { 0, 0, 4, 0, 2, 0, 1 }; /*y start values*/
static const u32 ADAM7_DX[7] = { 8, 8, 4, 4, 2, 2, 1 }; /*x delta values*/
static const u32 ADAM7_DY[7] = { 8, 8, 8, 4, 4, 2, 2 }; /*y delta values*/

/*
Outputs various dimensions and positions in the image related to the Adam7 reduced images.
passw: output containing the width of the 7 passes
passh: output containing the height of the 7 passes
filter_passstart: output containing the index of the start and end of each
 reduced image with filter bytes
padded_passstart output containing the index of the start and end of each
 reduced image when without filter bytes but with padded scanlines
passstart: output containing the index of the start and end of each reduced
 image without padding between scanlines, but still padding between the images
w, h: width and height of non-interlaced image
bpp: bits per pixel
"padded" is only relevant if bpp is less than 8 and a scanline or image does not
 end at a full byte
*/
static void Adam7_getpassvalues(u32 passw[7], u32 passh[7], u32 filter_passstart[8],
				u32 padded_passstart[8], u32 passstart[8], u32 w, u32 h, u32 bpp)
{
	/*the passstart values have 8 values: the 8th one indicates the byte after the end of the 7th (= last) pass*/
	u32 i;

	/*calculate width and height in pixels of each pass*/
	for (i = 0; i != 7; ++i) {
		passw[i] = (w + ADAM7_DX[i] - ADAM7_IX[i] - 1) / ADAM7_DX[i];
		passh[i] = (h + ADAM7_DY[i] - ADAM7_IY[i] - 1) / ADAM7_DY[i];
		if (passw[i] == 0)
			passh[i] = 0;
		if (passh[i] == 0)
			passw[i] = 0;
	}

	filter_passstart[0] = padded_passstart[0] = passstart[0] = 0;
	for (i = 0; i != 7; ++i) {
		/*if passw[i] is 0, it's 0 bytes, not 1 (no filtertype-byte)*/
		filter_passstart[i + 1] =
			filter_passstart[i] +
			((passw[i] && passh[i]) ? passh[i] * (1u + (passw[i] * bpp + 7u) / 8u) : 0);
		/*bits padded if needed to fill full byte at end of each scanline*/
		padded_passstart[i + 1] =
			padded_passstart[i] + passh[i] * ((passw[i] * bpp + 7u) / 8u);
		/*only padded at end of reduced image*/
		passstart[i + 1] = passstart[i] + (passh[i] * passw[i] * bpp + 7u) / 8u;
	}
}

#ifdef PNG_COMPILE_DECODER

/* ////////////////////////////////////////////////////////////////////////// */
/* / PNG Decoder                                                            / */
/* ////////////////////////////////////////////////////////////////////////// */

/*read the information from the header and store it in the pngInfo. return value is error*/
u32 png_inspect(u32 *w, u32 *h, pngState *state, const u8 *in, u32 insize)
{
	u32 width, height;
	pngInfo *info = &state->info_png;
	if (insize == 0 || in == 0) {
		CERROR_RETURN_ERROR(state->error, 48); /*error: the given data is empty*/
	}
	if (insize < 33) {
		CERROR_RETURN_ERROR(
			state->error,
			27); /*error: the data length is smaller than the length of a PNG header*/
	}

	/*when decoding a new PNG image, make sure all parameters created after previous decoding are reset*/
	/* TODO: remove this. One should use a new pngState for new sessions */
	png_info_cleanup(info);
	png_info_init(info);

	if (in[0] != 137 || in[1] != 80 || in[2] != 78 || in[3] != 71 || in[4] != 13 ||
	    in[5] != 10 || in[6] != 26 || in[7] != 10) {
		CERROR_RETURN_ERROR(
			state->error,
			28); /*error: the first 8 bytes are not the correct PNG signature*/
	}
	if (png_chunk_length(in + 8) != 13) {
		CERROR_RETURN_ERROR(state->error, 94); /*error: header size must be 13 bytes*/
	}
	if (!png_chunk_type_equals(in + 8, "IHDR")) {
		CERROR_RETURN_ERROR(state->error,
				    29); /*error: it doesn't start with a IHDR chunk!*/
	}

	/*read the values given in the header*/
	width = png_read32bitInt(&in[16]);
	height = png_read32bitInt(&in[20]);
	/*TODO: remove the undocumented feature that allows to give null pointers to width or height*/
	if (w)
		*w = width;
	if (h)
		*h = height;
	info->color.bitdepth = in[24];
	info->color.colortype = (pngColorType)in[25];
	info->compression_method = in[26];
	info->filter_method = in[27];
	info->interlace_method = in[28];

	/*errors returned only after the parsing so other values are still output*/

	/*error: invalid image size*/
	if (width == 0 || height == 0)
		CERROR_RETURN_ERROR(state->error, 93);
	/*error: invalid colortype or bitdepth combination*/
	state->error = checkColorValidity(info->color.colortype, info->color.bitdepth);
	if (state->error)
		return state->error;
	/*error: only compression method 0 is allowed in the specification*/
	if (info->compression_method != 0)
		CERROR_RETURN_ERROR(state->error, 32);
	/*error: only filter method 0 is allowed in the specification*/
	if (info->filter_method != 0)
		CERROR_RETURN_ERROR(state->error, 33);
	/*error: only interlace methods 0 and 1 exist in the specification*/
	if (info->interlace_method > 1)
		CERROR_RETURN_ERROR(state->error, 34);

	if (!state->decoder.ignore_crc) {
		u32 CRC = png_read32bitInt(&in[29]);
		u32 checksum = png_crc32(&in[12], 17);
		if (CRC != checksum) {
			CERROR_RETURN_ERROR(state->error, 57); /*invalid CRC*/
		}
	}

	return state->error;
}

static u32 unfilterScanline(u8 *recon, const u8 *scanline, const u8 *precon, u32 bytewidth,
			    u8 filterType, u32 length)
{
	/*
  For PNG filter method 0
  unfilter a PNG image scanline by scanline. when the pixels are smaller than 1 byte,
  the filter works byte per byte (bytewidth = 1)
  precon is the previous unfiltered scanline, recon the result, scanline the current one
  the incoming scanlines do NOT include the filtertype byte, that one is given in the parameter filterType instead
  recon and scanline MAY be the same memory address! precon must be disjoint.
  */

	u32 i;
	switch (filterType) {
	case 0:
		for (i = 0; i != length; ++i)
			recon[i] = scanline[i];
		break;
	case 1:
		for (i = 0; i != bytewidth; ++i)
			recon[i] = scanline[i];
		for (i = bytewidth; i < length; ++i)
			recon[i] = scanline[i] + recon[i - bytewidth];
		break;
	case 2:
		if (precon) {
			for (i = 0; i != length; ++i)
				recon[i] = scanline[i] + precon[i];
		} else {
			for (i = 0; i != length; ++i)
				recon[i] = scanline[i];
		}
		break;
	case 3:
		if (precon) {
			for (i = 0; i != bytewidth; ++i)
				recon[i] = scanline[i] + (precon[i] >> 1u);
			for (i = bytewidth; i < length; ++i)
				recon[i] = scanline[i] + ((recon[i - bytewidth] + precon[i]) >> 1u);
		} else {
			for (i = 0; i != bytewidth; ++i)
				recon[i] = scanline[i];
			for (i = bytewidth; i < length; ++i)
				recon[i] = scanline[i] + (recon[i - bytewidth] >> 1u);
		}
		break;
	case 4:
		if (precon) {
			for (i = 0; i != bytewidth; ++i) {
				recon[i] =
					(scanline[i] +
					 precon[i]); /*paethPredictor(0, precon[i], 0) is always precon[i]*/
			}

			/* Unroll independent paths of the paeth predictor. A 6x and 8x version would also be possible but that
        adds too much code. Whether this actually speeds anything up at all depends on compiler and settings. */
			if (bytewidth >= 4) {
				for (; i + 3 < length; i += 4) {
					u32 j = i - bytewidth;
					u8 s0 = scanline[i + 0], s1 = scanline[i + 1],
					   s2 = scanline[i + 2], s3 = scanline[i + 3];
					u8 r0 = recon[j + 0], r1 = recon[j + 1], r2 = recon[j + 2],
					   r3 = recon[j + 3];
					u8 p0 = precon[i + 0], p1 = precon[i + 1],
					   p2 = precon[i + 2], p3 = precon[i + 3];
					u8 q0 = precon[j + 0], q1 = precon[j + 1],
					   q2 = precon[j + 2], q3 = precon[j + 3];
					recon[i + 0] = s0 + paethPredictor(r0, p0, q0);
					recon[i + 1] = s1 + paethPredictor(r1, p1, q1);
					recon[i + 2] = s2 + paethPredictor(r2, p2, q2);
					recon[i + 3] = s3 + paethPredictor(r3, p3, q3);
				}
			} else if (bytewidth >= 3) {
				for (; i + 2 < length; i += 3) {
					u32 j = i - bytewidth;
					u8 s0 = scanline[i + 0], s1 = scanline[i + 1],
					   s2 = scanline[i + 2];
					u8 r0 = recon[j + 0], r1 = recon[j + 1], r2 = recon[j + 2];
					u8 p0 = precon[i + 0], p1 = precon[i + 1],
					   p2 = precon[i + 2];
					u8 q0 = precon[j + 0], q1 = precon[j + 1],
					   q2 = precon[j + 2];
					recon[i + 0] = s0 + paethPredictor(r0, p0, q0);
					recon[i + 1] = s1 + paethPredictor(r1, p1, q1);
					recon[i + 2] = s2 + paethPredictor(r2, p2, q2);
				}
			} else if (bytewidth >= 2) {
				for (; i + 1 < length; i += 2) {
					u32 j = i - bytewidth;
					u8 s0 = scanline[i + 0], s1 = scanline[i + 1];
					u8 r0 = recon[j + 0], r1 = recon[j + 1];
					u8 p0 = precon[i + 0], p1 = precon[i + 1];
					u8 q0 = precon[j + 0], q1 = precon[j + 1];
					recon[i + 0] = s0 + paethPredictor(r0, p0, q0);
					recon[i + 1] = s1 + paethPredictor(r1, p1, q1);
				}
			}

			for (; i != length; ++i) {
				recon[i] = (scanline[i] + paethPredictor(recon[i - bytewidth],
									 precon[i],
									 precon[i - bytewidth]));
			}
		} else {
			for (i = 0; i != bytewidth; ++i) {
				recon[i] = scanline[i];
			}
			for (i = bytewidth; i < length; ++i) {
				/*paethPredictor(recon[i - bytewidth], 0, 0) is always recon[i - bytewidth]*/
				recon[i] = (scanline[i] + recon[i - bytewidth]);
			}
		}
		break;
	default:
		return 36; /*error: invalid filter type given*/
	}
	return 0;
}

static u32 unfilter(u8 *out, const u8 *in, u32 w, u32 h, u32 bpp)
{
	/*
  For PNG filter method 0
  this function unfilters a single image (e.g. without interlacing this is called once, with Adam7 seven times)
  out must have enough bytes allocated already, in must have the scanlines + 1 filtertype byte per scanline
  w and h are image dimensions or dimensions of reduced image, bpp is bits per pixel
  in and out are allowed to be the same memory address (but aren't the same size since in has the extra filter bytes)
  */

	u32 y;
	u8 *prevline = 0;

	/*bytewidth is used for filtering, is 1 when bpp < 8, number of bytes per pixel otherwise*/
	u32 bytewidth = (bpp + 7u) / 8u;
	/*the width of a scanline in bytes, not including the filter type*/
	u32 linebytes = png_get_raw_size_idat(w, 1, bpp) - 1u;

	for (y = 0; y < h; ++y) {
		u32 outindex = linebytes * y;
		u32 inindex = (1 + linebytes) * y; /*the extra filterbyte added to each row*/
		u8 filterType = in[inindex];

		CERROR_TRY_RETURN(unfilterScanline(&out[outindex], &in[inindex + 1], prevline,
						   bytewidth, filterType, linebytes));

		prevline = &out[outindex];
	}

	return 0;
}

/*
in: Adam7 interlaced image, with no padding bits between scanlines, but between
 reduced images so that each reduced image starts at a byte.
out: the same pixels, but re-ordered so that they're now a non-interlaced image with size w*h
bpp: bits per pixel
out has the following size in bits: w * h * bpp.
in is possibly bigger due to padding bits between reduced images.
out must be big enough AND must be 0 everywhere if bpp < 8 in the current implementation
(because that's likely a little bit faster)
NOTE: comments about padding bits are only relevant if bpp < 8
*/
static void Adam7_deinterlace(u8 *out, const u8 *in, u32 w, u32 h, u32 bpp)
{
	u32 passw[7], passh[7];
	u32 filter_passstart[8], padded_passstart[8], passstart[8];
	u32 i;

	Adam7_getpassvalues(passw, passh, filter_passstart, padded_passstart, passstart, w, h, bpp);

	if (bpp >= 8) {
		for (i = 0; i != 7; ++i) {
			u32 x, y, b;
			u32 bytewidth = bpp / 8u;
			for (y = 0; y < passh[i]; ++y)
				for (x = 0; x < passw[i]; ++x) {
					u32 pixelinstart =
						passstart[i] + (y * passw[i] + x) * bytewidth;
					u32 pixeloutstart =
						((ADAM7_IY[i] + (u32)y * ADAM7_DY[i]) * (u32)w +
						 ADAM7_IX[i] + (u32)x * ADAM7_DX[i]) *
						bytewidth;
					for (b = 0; b < bytewidth; ++b) {
						out[pixeloutstart + b] = in[pixelinstart + b];
					}
				}
		}
	} else /*bpp < 8: Adam7 with pixels < 8 bit is a bit trickier: with bit pointers*/ {
		for (i = 0; i != 7; ++i) {
			u32 x, y, b;
			u32 ilinebits = bpp * passw[i];
			u32 olinebits = bpp * w;
			u32 obp, ibp; /*bit pointers (for out and in buffer)*/
			for (y = 0; y < passh[i]; ++y)
				for (x = 0; x < passw[i]; ++x) {
					ibp = (8 * passstart[i]) + (y * ilinebits + x * bpp);
					obp = (ADAM7_IY[i] + (u32)y * ADAM7_DY[i]) * olinebits +
					      (ADAM7_IX[i] + (u32)x * ADAM7_DX[i]) * bpp;
					for (b = 0; b < bpp; ++b) {
						u8 bit = readBitFromReversedStream(&ibp, in);
						setBitOfReversedStream(&obp, out, bit);
					}
				}
		}
	}
}

static void removePaddingBits(u8 *out, const u8 *in, u32 olinebits, u32 ilinebits, u32 h)
{
	/*
  After filtering there are still padding bits if scanlines have non multiple of 8 bit amounts. They need
  to be removed (except at last scanline of (Adam7-reduced) image) before working with pure image buffers
  for the Adam7 code, the color convert code and the output to the user.
  in and out are allowed to be the same buffer, in may also be higher but still overlapping; in must
  have >= ilinebits*h bits, out must have >= olinebits*h bits, olinebits must be <= ilinebits
  also used to move bits after earlier such operations happened, e.g. in a sequence of reduced images from Adam7
  only useful if (ilinebits - olinebits) is a value in the range 1..7
  */
	u32 y;
	u32 diff = ilinebits - olinebits;
	u32 ibp = 0, obp = 0; /*input and output bit pointers*/
	for (y = 0; y < h; ++y) {
		u32 x;
		for (x = 0; x < olinebits; ++x) {
			u8 bit = readBitFromReversedStream(&ibp, in);
			setBitOfReversedStream(&obp, out, bit);
		}
		ibp += diff;
	}
}

/*out must be buffer big enough to contain full image, and in must contain the full decompressed data from
the IDAT chunks (with filter index bytes and possible padding bits)
return value is error*/
static u32 postProcessScanlines(u8 *out, u8 *in, u32 w, u32 h, const pngInfo *info_png)
{
	/*
  This function converts the filtered-padded-interlaced data into pure 2D image buffer with the PNG's colortype.
  Steps:
  *) if no Adam7: 1) unfilter 2) remove padding bits (= possible extra bits per scanline if bpp < 8)
  *) if adam7: 1) 7x unfilter 2) 7x remove padding bits 3) Adam7_deinterlace
  NOTE: the in buffer will be overwritten with intermediate data!
  */
	u32 bpp = png_get_bpp(&info_png->color);
	if (bpp == 0)
		return 31; /*error: invalid colortype*/

	if (info_png->interlace_method == 0) {
		if (bpp < 8 && w * bpp != ((w * bpp + 7u) / 8u) * 8u) {
			CERROR_TRY_RETURN(unfilter(in, in, w, h, bpp));
			removePaddingBits(out, in, w * bpp, ((w * bpp + 7u) / 8u) * 8u, h);
		}
		/*we can immediately filter into the out buffer, no other steps needed*/
		else
			CERROR_TRY_RETURN(unfilter(out, in, w, h, bpp));
	} else /*interlace_method is 1 (Adam7)*/ {
		u32 passw[7], passh[7];
		u32 filter_passstart[8], padded_passstart[8], passstart[8];
		u32 i;

		Adam7_getpassvalues(passw, passh, filter_passstart, padded_passstart, passstart, w,
				    h, bpp);

		for (i = 0; i != 7; ++i) {
			CERROR_TRY_RETURN(unfilter(&in[padded_passstart[i]],
						   &in[filter_passstart[i]], passw[i], passh[i],
						   bpp));
			/*TODO: possible efficiency improvement: if in this reduced image the bits fit nicely in 1 scanline,
      move bytes instead of bits or move not at all*/
			if (bpp < 8) {
				/*remove padding bits in scanlines; after this there still may be padding
        bits between the different reduced images: each reduced image still starts nicely at a byte*/
				removePaddingBits(&in[passstart[i]], &in[padded_passstart[i]],
						  passw[i] * bpp, ((passw[i] * bpp + 7u) / 8u) * 8u,
						  passh[i]);
			}
		}

		Adam7_deinterlace(out, in, w, h, bpp);
	}

	return 0;
}

static u32 readChunk_PLTE(pngColorMode *color, const u8 *data, u32 chunkLength)
{
	u32 pos = 0, i;
	color->palettesize = chunkLength / 3u;
	if (color->palettesize == 0 || color->palettesize > 256)
		return 38; /*error: palette too small or big*/
	png_color_mode_alloc_palette(color);
	if (!color->palette && color->palettesize) {
		color->palettesize = 0;
		return 83; /*alloc fail*/
	}

	for (i = 0; i != color->palettesize; ++i) {
		color->palette[4 * i + 0] = data[pos++]; /*R*/
		color->palette[4 * i + 1] = data[pos++]; /*G*/
		color->palette[4 * i + 2] = data[pos++]; /*B*/
		color->palette[4 * i + 3] = 255; /*alpha*/
	}

	return 0; /* OK */
}

static u32 readChunk_tRNS(pngColorMode *color, const u8 *data, u32 chunkLength)
{
	u32 i;
	if (color->colortype == LCT_PALETTE) {
		/*error: more alpha values given than there are palette entries*/
		if (chunkLength > color->palettesize)
			return 39;

		for (i = 0; i != chunkLength; ++i)
			color->palette[4 * i + 3] = data[i];
	} else if (color->colortype == LCT_GREY) {
		/*error: this chunk must be 2 bytes for grayscale image*/
		if (chunkLength != 2)
			return 30;

		color->key_defined = 1;
		color->key_r = color->key_g = color->key_b = 256u * data[0] + data[1];
	} else if (color->colortype == LCT_RGB) {
		/*error: this chunk must be 6 bytes for RGB image*/
		if (chunkLength != 6)
			return 41;

		color->key_defined = 1;
		color->key_r = 256u * data[0] + data[1];
		color->key_g = 256u * data[2] + data[3];
		color->key_b = 256u * data[4] + data[5];
	} else
		return 42; /*error: tRNS chunk not allowed for other color models*/

	return 0; /* OK */
}

#ifdef PNG_COMPILE_ANCILLARY_CHUNKS
/*background color chunk (bKGD)*/
static u32 readChunk_bKGD(pngInfo *info, const u8 *data, u32 chunkLength)
{
	if (info->color.colortype == LCT_PALETTE) {
		/*error: this chunk must be 1 byte for indexed color image*/
		if (chunkLength != 1)
			return 43;

		/*error: invalid palette index, or maybe this chunk appeared before PLTE*/
		if (data[0] >= info->color.palettesize)
			return 103;

		info->background_defined = 1;
		info->background_r = info->background_g = info->background_b = data[0];
	} else if (info->color.colortype == LCT_GREY || info->color.colortype == LCT_GREY_ALPHA) {
		/*error: this chunk must be 2 bytes for grayscale image*/
		if (chunkLength != 2)
			return 44;

		/*the values are truncated to bitdepth in the PNG file*/
		info->background_defined = 1;
		info->background_r = info->background_g = info->background_b =
			256u * data[0] + data[1];
	} else if (info->color.colortype == LCT_RGB || info->color.colortype == LCT_RGBA) {
		/*error: this chunk must be 6 bytes for grayscale image*/
		if (chunkLength != 6)
			return 45;

		/*the values are truncated to bitdepth in the PNG file*/
		info->background_defined = 1;
		info->background_r = 256u * data[0] + data[1];
		info->background_g = 256u * data[2] + data[3];
		info->background_b = 256u * data[4] + data[5];
	}

	return 0; /* OK */
}

/*text chunk (tEXt)*/
static u32 readChunk_tEXt(pngInfo *info, const u8 *data, u32 chunkLength)
{
	u32 error = 0;
	char *key = 0, *str = 0;

	while (!error) /*not really a while loop, only used to break on error*/ {
		u32 length, string2_begin;

		length = 0;
		while (length < chunkLength && data[length] != 0)
			++length;
		/*even though it's not allowed by the standard, no error is thrown if
    there's no null termination char, if the text is empty*/
		if (length < 1 || length > 79)
			CERROR_BREAK(error, 89); /*keyword too short or long*/

		key = (char *)png_malloc(length + 1);
		if (!key)
			CERROR_BREAK(error, 83); /*alloc fail*/

		png_memcpy(key, data, length);
		key[length] = 0;

		string2_begin = length + 1; /*skip keyword null terminator*/

		length = (u32)(chunkLength < string2_begin ? 0 : chunkLength - string2_begin);
		str = (char *)png_malloc(length + 1);
		if (!str)
			CERROR_BREAK(error, 83); /*alloc fail*/

		png_memcpy(str, data + string2_begin, length);
		str[length] = 0;

		error = png_add_text(info, key, str);

		break;
	}

	png_free(key);
	png_free(str);

	return error;
}

/*compressed text chunk (zTXt)*/
static u32 readChunk_zTXt(pngInfo *info, const pngDecoderSettings *decoder, const u8 *data,
			  u32 chunkLength)
{
	u32 error = 0;

	/*copy the object to change parameters in it*/
	pngDecompressSettings zlibsettings = decoder->zlibsettings;

	u32 length, string2_begin;
	char *key = 0;
	u8 *str = 0;
	u32 size = 0;

	while (!error) /*not really a while loop, only used to break on error*/ {
		for (length = 0; length < chunkLength && data[length] != 0; ++length)
			;
		if (length + 2 >= chunkLength)
			CERROR_BREAK(error, 75); /*no null termination, corrupt?*/
		if (length < 1 || length > 79)
			CERROR_BREAK(error, 89); /*keyword too short or long*/

		key = (char *)png_malloc(length + 1);
		if (!key)
			CERROR_BREAK(error, 83); /*alloc fail*/

		png_memcpy(key, data, length);
		key[length] = 0;

		if (data[length + 1] != 0)
			CERROR_BREAK(error, 72); /*the 0 byte indicating compression must be 0*/

		string2_begin = length + 2;
		if (string2_begin > chunkLength)
			CERROR_BREAK(error, 75); /*no null termination, corrupt?*/

		length = (u32)chunkLength - string2_begin;
		zlibsettings.max_output_size = decoder->max_text_size;
		/*will fail if zlib error, e.g. if length is too small*/
		error = zlib_decompress(&str, &size, 0, &data[string2_begin], length,
					&zlibsettings);
		/*error: compressed text larger than  decoder->max_text_size*/
		if (error && size > zlibsettings.max_output_size)
			error = 112;
		if (error)
			break;
		error = png_add_text_sized(info, key, (char *)str, size);
		break;
	}

	png_free(key);
	png_free(str);

	return error;
}

/*international text chunk (iTXt)*/
static u32 readChunk_iTXt(pngInfo *info, const pngDecoderSettings *decoder, const u8 *data,
			  u32 chunkLength)
{
	u32 error = 0;
	u32 i;

	/*copy the object to change parameters in it*/
	pngDecompressSettings zlibsettings = decoder->zlibsettings;

	u32 length, begin, compressed;
	char *key = 0, *langtag = 0, *transkey = 0;

	while (!error) /*not really a while loop, only used to break on error*/ {
		/*Quick check if the chunk length isn't too small. Even without check
    it'd still fail with other error checks below if it's too short. This just gives a different error code.*/
		if (chunkLength < 5)
			CERROR_BREAK(error, 30); /*iTXt chunk too short*/

		/*read the key*/
		for (length = 0; length < chunkLength && data[length] != 0; ++length)
			;
		if (length + 3 >= chunkLength)
			CERROR_BREAK(error, 75); /*no null termination char, corrupt?*/
		if (length < 1 || length > 79)
			CERROR_BREAK(error, 89); /*keyword too short or long*/

		key = (char *)png_malloc(length + 1);
		if (!key)
			CERROR_BREAK(error, 83); /*alloc fail*/

		png_memcpy(key, data, length);
		key[length] = 0;

		/*read the compression method*/
		compressed = data[length + 1];
		if (data[length + 2] != 0)
			CERROR_BREAK(error, 72); /*the 0 byte indicating compression must be 0*/

		/*even though it's not allowed by the standard, no error is thrown if
    there's no null termination char, if the text is empty for the next 3 texts*/

		/*read the langtag*/
		begin = length + 3;
		length = 0;
		for (i = begin; i < chunkLength && data[i] != 0; ++i)
			++length;

		langtag = (char *)png_malloc(length + 1);
		if (!langtag)
			CERROR_BREAK(error, 83); /*alloc fail*/

		png_memcpy(langtag, data + begin, length);
		langtag[length] = 0;

		/*read the transkey*/
		begin += length + 1;
		length = 0;
		for (i = begin; i < chunkLength && data[i] != 0; ++i)
			++length;

		transkey = (char *)png_malloc(length + 1);
		if (!transkey)
			CERROR_BREAK(error, 83); /*alloc fail*/

		png_memcpy(transkey, data + begin, length);
		transkey[length] = 0;

		/*read the actual text*/
		begin += length + 1;

		length = (u32)chunkLength < begin ? 0 : (u32)chunkLength - begin;

		if (compressed) {
			u8 *str = 0;
			u32 size = 0;
			zlibsettings.max_output_size = decoder->max_text_size;
			/*will fail if zlib error, e.g. if length is too small*/
			error = zlib_decompress(&str, &size, 0, &data[begin], length,
						&zlibsettings);
			/*error: compressed text larger than  decoder->max_text_size*/
			if (error && size > zlibsettings.max_output_size)
				error = 112;
			if (!error)
				error = png_add_itext_sized(info, key, langtag, transkey,
							    (char *)str, size);
			png_free(str);
		} else {
			error = png_add_itext_sized(info, key, langtag, transkey,
						    (const char *)(data + begin), length);
		}

		break;
	}

	png_free(key);
	png_free(langtag);
	png_free(transkey);

	return error;
}

static u32 readChunk_tIME(pngInfo *info, const u8 *data, u32 chunkLength)
{
	if (chunkLength != 7)
		return 73; /*invalid tIME chunk size*/

	info->time_defined = 1;
	info->time.year = 256u * data[0] + data[1];
	info->time.month = data[2];
	info->time.day = data[3];
	info->time.hour = data[4];
	info->time.minute = data[5];
	info->time.second = data[6];

	return 0; /* OK */
}

static u32 readChunk_pHYs(pngInfo *info, const u8 *data, u32 chunkLength)
{
	if (chunkLength != 9)
		return 74; /*invalid pHYs chunk size*/

	info->phys_defined = 1;
	info->phys_x = 16777216u * data[0] + 65536u * data[1] + 256u * data[2] + data[3];
	info->phys_y = 16777216u * data[4] + 65536u * data[5] + 256u * data[6] + data[7];
	info->phys_unit = data[8];

	return 0; /* OK */
}

static u32 readChunk_gAMA(pngInfo *info, const u8 *data, u32 chunkLength)
{
	if (chunkLength != 4)
		return 96; /*invalid gAMA chunk size*/

	info->gama_defined = 1;
	info->gama_gamma = 16777216u * data[0] + 65536u * data[1] + 256u * data[2] + data[3];

	return 0; /* OK */
}

static u32 readChunk_cHRM(pngInfo *info, const u8 *data, u32 chunkLength)
{
	if (chunkLength != 32)
		return 97; /*invalid cHRM chunk size*/

	info->chrm_defined = 1;
	info->chrm_white_x = 16777216u * data[0] + 65536u * data[1] + 256u * data[2] + data[3];
	info->chrm_white_y = 16777216u * data[4] + 65536u * data[5] + 256u * data[6] + data[7];
	info->chrm_red_x = 16777216u * data[8] + 65536u * data[9] + 256u * data[10] + data[11];
	info->chrm_red_y = 16777216u * data[12] + 65536u * data[13] + 256u * data[14] + data[15];
	info->chrm_green_x = 16777216u * data[16] + 65536u * data[17] + 256u * data[18] + data[19];
	info->chrm_green_y = 16777216u * data[20] + 65536u * data[21] + 256u * data[22] + data[23];
	info->chrm_blue_x = 16777216u * data[24] + 65536u * data[25] + 256u * data[26] + data[27];
	info->chrm_blue_y = 16777216u * data[28] + 65536u * data[29] + 256u * data[30] + data[31];

	return 0; /* OK */
}

static u32 readChunk_sRGB(pngInfo *info, const u8 *data, u32 chunkLength)
{
	if (chunkLength != 1)
		return 98; /*invalid sRGB chunk size (this one is never ignored)*/

	info->srgb_defined = 1;
	info->srgb_intent = data[0];

	return 0; /* OK */
}

static u32 readChunk_iCCP(pngInfo *info, const pngDecoderSettings *decoder, const u8 *data,
			  u32 chunkLength)
{
	u32 error = 0;
	u32 i;
	u32 size = 0;
	/*copy the object to change parameters in it*/
	pngDecompressSettings zlibsettings = decoder->zlibsettings;

	u32 length, string2_begin;

	info->iccp_defined = 1;
	if (info->iccp_name)
		png_clear_icc(info);

	for (length = 0; length < chunkLength && data[length] != 0; ++length)
		;
	if (length + 2 >= chunkLength)
		return 75; /*no null termination, corrupt?*/
	if (length < 1 || length > 79)
		return 89; /*keyword too short or long*/

	info->iccp_name = (char *)png_malloc(length + 1);
	if (!info->iccp_name)
		return 83; /*alloc fail*/

	info->iccp_name[length] = 0;
	for (i = 0; i != length; ++i)
		info->iccp_name[i] = (char)data[i];

	if (data[length + 1] != 0)
		return 72; /*the 0 byte indicating compression must be 0*/

	string2_begin = length + 2;
	if (string2_begin > chunkLength)
		return 75; /*no null termination, corrupt?*/

	length = (u32)chunkLength - string2_begin;
	zlibsettings.max_output_size = decoder->max_icc_size;
	error = zlib_decompress(&info->iccp_profile, &size, 0, &data[string2_begin], length,
				&zlibsettings);
	/*error: ICC profile larger than  decoder->max_icc_size*/
	if (error && size > zlibsettings.max_output_size)
		error = 113;
	info->iccp_profile_size = size;
	if (!error && !info->iccp_profile_size)
		error = 100; /*invalid ICC profile size*/
	return error;
}
#endif /*PNG_COMPILE_ANCILLARY_CHUNKS*/

u32 png_inspect_chunk(pngState *state, u32 pos, const u8 *in, u32 insize)
{
	const u8 *chunk = in + pos;
	u32 chunkLength;
	const u8 *data;
	u32 unhandled = 0;
	u32 error = 0;

	if (pos + 4 > insize)
		return 30;
	chunkLength = png_chunk_length(chunk);
	if (chunkLength > 2147483647)
		return 63;
	data = png_chunk_data_const(chunk);
	if (data + chunkLength + 4 > in + insize)
		return 30;

	if (png_chunk_type_equals(chunk, "PLTE")) {
		error = readChunk_PLTE(&state->info_png.color, data, chunkLength);
	} else if (png_chunk_type_equals(chunk, "tRNS")) {
		error = readChunk_tRNS(&state->info_png.color, data, chunkLength);
#ifdef PNG_COMPILE_ANCILLARY_CHUNKS
	} else if (png_chunk_type_equals(chunk, "bKGD")) {
		error = readChunk_bKGD(&state->info_png, data, chunkLength);
	} else if (png_chunk_type_equals(chunk, "tEXt")) {
		error = readChunk_tEXt(&state->info_png, data, chunkLength);
	} else if (png_chunk_type_equals(chunk, "zTXt")) {
		error = readChunk_zTXt(&state->info_png, &state->decoder, data, chunkLength);
	} else if (png_chunk_type_equals(chunk, "iTXt")) {
		error = readChunk_iTXt(&state->info_png, &state->decoder, data, chunkLength);
	} else if (png_chunk_type_equals(chunk, "tIME")) {
		error = readChunk_tIME(&state->info_png, data, chunkLength);
	} else if (png_chunk_type_equals(chunk, "pHYs")) {
		error = readChunk_pHYs(&state->info_png, data, chunkLength);
	} else if (png_chunk_type_equals(chunk, "gAMA")) {
		error = readChunk_gAMA(&state->info_png, data, chunkLength);
	} else if (png_chunk_type_equals(chunk, "cHRM")) {
		error = readChunk_cHRM(&state->info_png, data, chunkLength);
	} else if (png_chunk_type_equals(chunk, "sRGB")) {
		error = readChunk_sRGB(&state->info_png, data, chunkLength);
	} else if (png_chunk_type_equals(chunk, "iCCP")) {
		error = readChunk_iCCP(&state->info_png, &state->decoder, data, chunkLength);
#endif /*PNG_COMPILE_ANCILLARY_CHUNKS*/
	} else {
		/* unhandled chunk is ok (is not an error) */
		unhandled = 1;
	}

	if (!error && !unhandled && !state->decoder.ignore_crc) {
		if (png_chunk_check_crc(chunk))
			return 57; /*invalid CRC*/
	}

	return error;
}

/*read a PNG, the result will be in the same color type as the PNG (hence "generic")*/
static void decodeGeneric(u8 **out, u32 *w, u32 *h, pngState *state, const u8 *in, u32 insize)
{
	u8 IEND = 0;
	const u8 *chunk;
	u8 *idat; /*the data from idat chunks, zlib compressed*/
	u32 idatsize = 0;
	u8 *scanlines = 0;
	u32 scanlines_size = 0, expected_size = 0;
	u32 outsize = 0;

	/*for unknown chunk order*/
	u32 unknown = 0;
#ifdef PNG_COMPILE_ANCILLARY_CHUNKS
	u32 critical_pos = 1; /*1 = after IHDR, 2 = after PLTE, 3 = after IDAT*/
#endif /*PNG_COMPILE_ANCILLARY_CHUNKS*/

	/* safe output values in case error happens */
	*out = 0;
	*w = *h = 0;

	state->error =
		png_inspect(w, h, state, in,
			    insize); /*reads header and resets other parameters in state->info_png*/
	if (state->error)
		return;

	if (png_pixel_overflow(*w, *h, &state->info_png.color, &state->info_raw)) {
		CERROR_RETURN(state->error, 92); /*overflow possible due to amount of pixels*/
	}

	/*the input filesize is a safe upper bound for the sum of idat chunks size*/
	idat = (u8 *)png_malloc(insize);
	if (!idat)
		CERROR_RETURN(state->error, 83); /*alloc fail*/

	chunk = &in[33]; /*first byte of the first chunk after the header*/

	/*loop through the chunks, ignoring unknown chunks and stopping at IEND chunk.
  IDAT data is put at the start of the in buffer*/
	while (!IEND && !state->error) {
		u32 chunkLength;
		const u8 *data; /*the data in the chunk*/

		/*error: size of the in buffer too small to contain next chunk*/
		if ((u32)((chunk - in) + 12) > insize || chunk < in) {
			if (state->decoder.ignore_end)
				break; /*other errors may still happen though*/
			CERROR_BREAK(state->error, 30);
		}

		/*length of the data of the chunk, excluding the length bytes, chunk type and CRC bytes*/
		chunkLength = png_chunk_length(chunk);
		/*error: chunk length larger than the max PNG chunk size*/
		if (chunkLength > 2147483647) {
			if (state->decoder.ignore_end)
				break; /*other errors may still happen though*/
			CERROR_BREAK(state->error, 63);
		}

		if ((u32)((chunk - in) + chunkLength + 12) > insize ||
		    (chunk + chunkLength + 12) < in) {
			CERROR_BREAK(
				state->error,
				64); /*error: size of the in buffer too small to contain next chunk*/
		}

		data = png_chunk_data_const(chunk);

		unknown = 0;

		/*IDAT chunk, containing compressed image data*/
		if (png_chunk_type_equals(chunk, "IDAT")) {
			u32 newsize;
			if (png_addofl(idatsize, chunkLength, &newsize))
				CERROR_BREAK(state->error, 95);
			if (newsize > insize)
				CERROR_BREAK(state->error, 95);
			png_memcpy(idat + idatsize, data, chunkLength);
			idatsize += chunkLength;
#ifdef PNG_COMPILE_ANCILLARY_CHUNKS
			critical_pos = 3;
#endif /*PNG_COMPILE_ANCILLARY_CHUNKS*/
		} else if (png_chunk_type_equals(chunk, "IEND")) {
			/*IEND chunk*/
			IEND = 1;
		} else if (png_chunk_type_equals(chunk, "PLTE")) {
			/*palette chunk (PLTE)*/
			state->error = readChunk_PLTE(&state->info_png.color, data, chunkLength);
			if (state->error)
				break;
#ifdef PNG_COMPILE_ANCILLARY_CHUNKS
			critical_pos = 2;
#endif /*PNG_COMPILE_ANCILLARY_CHUNKS*/
		} else if (png_chunk_type_equals(chunk, "tRNS")) {
			/*palette transparency chunk (tRNS). Even though this one is an ancillary chunk , it is still compiled
      in without 'PNG_COMPILE_ANCILLARY_CHUNKS' because it contains essential color information that
      affects the alpha channel of pixels. */
			state->error = readChunk_tRNS(&state->info_png.color, data, chunkLength);
			if (state->error)
				break;
#ifdef PNG_COMPILE_ANCILLARY_CHUNKS
			/*background color chunk (bKGD)*/
		} else if (png_chunk_type_equals(chunk, "bKGD")) {
			state->error = readChunk_bKGD(&state->info_png, data, chunkLength);
			if (state->error)
				break;
		} else if (png_chunk_type_equals(chunk, "tEXt")) {
			/*text chunk (tEXt)*/
			if (state->decoder.read_text_chunks) {
				state->error = readChunk_tEXt(&state->info_png, data, chunkLength);
				if (state->error)
					break;
			}
		} else if (png_chunk_type_equals(chunk, "zTXt")) {
			/*compressed text chunk (zTXt)*/
			if (state->decoder.read_text_chunks) {
				state->error = readChunk_zTXt(&state->info_png, &state->decoder,
							      data, chunkLength);
				if (state->error)
					break;
			}
		} else if (png_chunk_type_equals(chunk, "iTXt")) {
			/*international text chunk (iTXt)*/
			if (state->decoder.read_text_chunks) {
				state->error = readChunk_iTXt(&state->info_png, &state->decoder,
							      data, chunkLength);
				if (state->error)
					break;
			}
		} else if (png_chunk_type_equals(chunk, "tIME")) {
			state->error = readChunk_tIME(&state->info_png, data, chunkLength);
			if (state->error)
				break;
		} else if (png_chunk_type_equals(chunk, "pHYs")) {
			state->error = readChunk_pHYs(&state->info_png, data, chunkLength);
			if (state->error)
				break;
		} else if (png_chunk_type_equals(chunk, "gAMA")) {
			state->error = readChunk_gAMA(&state->info_png, data, chunkLength);
			if (state->error)
				break;
		} else if (png_chunk_type_equals(chunk, "cHRM")) {
			state->error = readChunk_cHRM(&state->info_png, data, chunkLength);
			if (state->error)
				break;
		} else if (png_chunk_type_equals(chunk, "sRGB")) {
			state->error = readChunk_sRGB(&state->info_png, data, chunkLength);
			if (state->error)
				break;
		} else if (png_chunk_type_equals(chunk, "iCCP")) {
			state->error = readChunk_iCCP(&state->info_png, &state->decoder, data,
						      chunkLength);
			if (state->error)
				break;
#endif /*PNG_COMPILE_ANCILLARY_CHUNKS*/
		} else /*it's not an implemented chunk type, so ignore it: skip over the data*/ {
			/*error: unknown critical chunk (5th bit of first byte of chunk type is 0)*/
			if (!state->decoder.ignore_critical && !png_chunk_ancillary(chunk)) {
				CERROR_BREAK(state->error, 69);
			}

			unknown = 1;
#ifdef PNG_COMPILE_ANCILLARY_CHUNKS
			if (state->decoder.remember_unknown_chunks) {
				state->error = png_chunk_append(
					&state->info_png.unknown_chunks_data[critical_pos - 1],
					&state->info_png.unknown_chunks_size[critical_pos - 1],
					chunk);
				if (state->error)
					break;
			}
#endif /*PNG_COMPILE_ANCILLARY_CHUNKS*/
		}

		if (!state->decoder.ignore_crc &&
		    !unknown) /*check CRC if wanted, only on known chunk types*/ {
			if (png_chunk_check_crc(chunk))
				CERROR_BREAK(state->error, 57); /*invalid CRC*/
		}

		if (!IEND)
			chunk = png_chunk_next_const(chunk, in + insize);
	}

	if (!state->error && state->info_png.color.colortype == LCT_PALETTE &&
	    !state->info_png.color.palette) {
		state->error =
			106; /* error: PNG file must have PLTE chunk if color type is palette */
	}

	if (!state->error) {
		/*predict output size, to allocate exact size for output buffer to avoid more dynamic allocation.
    If the decompressed size does not match the prediction, the image must be corrupt.*/
		if (state->info_png.interlace_method == 0) {
			u32 bpp = png_get_bpp(&state->info_png.color);
			expected_size = png_get_raw_size_idat(*w, *h, bpp);
		} else {
			u32 bpp = png_get_bpp(&state->info_png.color);
			/*Adam-7 interlaced: expected size is the sum of the 7 sub-images sizes*/
			expected_size = 0;
			expected_size += png_get_raw_size_idat((*w + 7) >> 3, (*h + 7) >> 3, bpp);
			if (*w > 4)
				expected_size +=
					png_get_raw_size_idat((*w + 3) >> 3, (*h + 7) >> 3, bpp);
			expected_size += png_get_raw_size_idat((*w + 3) >> 2, (*h + 3) >> 3, bpp);
			if (*w > 2)
				expected_size +=
					png_get_raw_size_idat((*w + 1) >> 2, (*h + 3) >> 2, bpp);
			expected_size += png_get_raw_size_idat((*w + 1) >> 1, (*h + 1) >> 2, bpp);
			if (*w > 1)
				expected_size +=
					png_get_raw_size_idat((*w + 0) >> 1, (*h + 1) >> 1, bpp);
			expected_size += png_get_raw_size_idat((*w + 0), (*h + 0) >> 1, bpp);
		}

		state->error = zlib_decompress(&scanlines, &scanlines_size, expected_size, idat,
					       idatsize, &state->decoder.zlibsettings);
	}
	if (!state->error && scanlines_size != expected_size)
		state->error = 91; /*decompressed size doesn't match prediction*/
	png_free(idat);

	if (!state->error) {
		outsize = png_get_raw_size(*w, *h, &state->info_png.color);
		*out = (u8 *)png_malloc(outsize);
		if (!*out)
			state->error = 83; /*alloc fail*/
	}
	if (!state->error) {
		png_memset(*out, 0, outsize);
		state->error = postProcessScanlines(*out, scanlines, *w, *h, &state->info_png);
	}
	png_free(scanlines);
}

u32 png_decode(u8 **out, u32 *w, u32 *h, pngState *state, const u8 *in, u32 insize)
{
	*out = 0;
	decodeGeneric(out, w, h, state, in, insize);
	if (state->error)
		return state->error;
	if (!state->decoder.color_convert ||
	    png_color_mode_equal(&state->info_raw, &state->info_png.color)) {
		/*same color type, no copying or converting of data needed*/
		/*store the info_png color settings on the info_raw so that the info_raw still reflects what colortype
    the raw image has to the end user*/
		if (!state->decoder.color_convert) {
			state->error =
				png_color_mode_copy(&state->info_raw, &state->info_png.color);
			if (state->error)
				return state->error;
		}
	} else { /*color conversion needed*/
		u8 *data = *out;
		u32 outsize;

		/*TODO: check if this works according to the statement in the documentation: "The converter can convert
    from grayscale input color type, to 8-bit grayscale or grayscale with alpha"*/
		if (!(state->info_raw.colortype == LCT_RGB ||
		      state->info_raw.colortype == LCT_RGBA) &&
		    !(state->info_raw.bitdepth == 8)) {
			return 56; /*unsupported color mode conversion*/
		}

		outsize = png_get_raw_size(*w, *h, &state->info_raw);
		*out = (u8 *)png_malloc(outsize);
		if (!(*out)) {
			state->error = 83; /*alloc fail*/
		} else
			state->error = png_convert(*out, data, &state->info_raw,
						   &state->info_png.color, *w, *h);
		png_free(data);
	}
	return state->error;
}

u32 png_decode_memory(u8 **out, u32 *w, u32 *h, const u8 *in, u32 insize, pngColorType colortype,
		      u32 bitdepth)
{
	u32 error;
	pngState state;
	png_state_init(&state);
	state.info_raw.colortype = colortype;
	state.info_raw.bitdepth = bitdepth;
#ifdef PNG_COMPILE_ANCILLARY_CHUNKS
	/*disable reading things that this function doesn't output*/
	state.decoder.read_text_chunks = 0;
	state.decoder.remember_unknown_chunks = 0;
#endif /*PNG_COMPILE_ANCILLARY_CHUNKS*/
	error = png_decode(out, w, h, &state, in, insize);
	png_state_cleanup(&state);
	return error;
}

u32 png_decode32(u8 **out, u32 *w, u32 *h, const u8 *in, u32 insize)
{
	return png_decode_memory(out, w, h, in, insize, LCT_RGBA, 8);
}

u32 png_decode24(u8 **out, u32 *w, u32 *h, const u8 *in, u32 insize)
{
	return png_decode_memory(out, w, h, in, insize, LCT_RGB, 8);
}

#ifdef PNG_COMPILE_DISK
u32 png_decode_file(u8 **out, u32 *w, u32 *h, const char *filename, pngColorType colortype,
		    u32 bitdepth)
{
	u8 *buffer = 0;
	u32 buffersize;
	u32 error;
	/* safe output values in case error happens */
	*out = 0;
	*w = *h = 0;
	error = png_load_file(&buffer, &buffersize, filename);
	if (!error)
		error = png_decode_memory(out, w, h, buffer, buffersize, colortype, bitdepth);
	png_free(buffer);
	return error;
}

u32 png_decode32_file(u8 **out, u32 *w, u32 *h, const char *filename)
{
	return png_decode_file(out, w, h, filename, LCT_RGBA, 8);
}

u32 png_decode24_file(u8 **out, u32 *w, u32 *h, const char *filename)
{
	return png_decode_file(out, w, h, filename, LCT_RGB, 8);
}
#endif /*PNG_COMPILE_DISK*/

void png_decoder_settings_init(pngDecoderSettings *settings)
{
	settings->color_convert = 1;
#ifdef PNG_COMPILE_ANCILLARY_CHUNKS
	settings->read_text_chunks = 1;
	settings->remember_unknown_chunks = 0;
	settings->max_text_size = 16777216;
	settings->max_icc_size =
		16777216; /* 16MB is much more than enough for any reasonable ICC profile */
#endif /*PNG_COMPILE_ANCILLARY_CHUNKS*/
	settings->ignore_crc = 0;
	settings->ignore_critical = 0;
	settings->ignore_end = 0;
	png_decompress_settings_init(&settings->zlibsettings);
}

#endif /*PNG_COMPILE_DECODER*/

#if defined(PNG_COMPILE_DECODER) || defined(PNG_COMPILE_ENCODER)

void png_state_init(pngState *state)
{
#ifdef PNG_COMPILE_DECODER
	png_decoder_settings_init(&state->decoder);
#endif /*PNG_COMPILE_DECODER*/
#ifdef PNG_COMPILE_ENCODER
	png_encoder_settings_init(&state->encoder);
#endif /*PNG_COMPILE_ENCODER*/
	png_color_mode_init(&state->info_raw);
	png_info_init(&state->info_png);
	state->error = 1;
}

void png_state_cleanup(pngState *state)
{
	png_color_mode_cleanup(&state->info_raw);
	png_info_cleanup(&state->info_png);
}

void png_state_copy(pngState *dest, const pngState *source)
{
	png_state_cleanup(dest);
	*dest = *source;
	png_color_mode_init(&dest->info_raw);
	png_info_init(&dest->info_png);
	dest->error = png_color_mode_copy(&dest->info_raw, &source->info_raw);
	if (dest->error)
		return;
	dest->error = png_info_copy(&dest->info_png, &source->info_png);
	if (dest->error)
		return;
}

#endif /* defined(PNG_COMPILE_DECODER) || defined(PNG_COMPILE_ENCODER) */

#ifdef PNG_COMPILE_ENCODER

/* ////////////////////////////////////////////////////////////////////////// */
/* / PNG Encoder                                                            / */
/* ////////////////////////////////////////////////////////////////////////// */

static u32 writeSignature(ucvector *out)
{
	u32 pos = out->size;
	const u8 signature[] = { 137, 80, 78, 71, 13, 10, 26, 10 };
	/*8 bytes PNG signature, aka the magic bytes*/
	if (!ucvector_resize(out, out->size + 8))
		return 83; /*alloc fail*/
	png_memcpy(out->data + pos, signature, 8);
	return 0;
}

static u32 addChunk_IHDR(ucvector *out, u32 w, u32 h, pngColorType colortype, u32 bitdepth,
			 u32 interlace_method)
{
	u8 *chunk, *data;
	CERROR_TRY_RETURN(png_chunk_init(&chunk, out, 13, "IHDR"));
	data = chunk + 8;

	png_set32bitInt(data + 0, w); /*width*/
	png_set32bitInt(data + 4, h); /*height*/
	data[8] = (u8)bitdepth; /*bit depth*/
	data[9] = (u8)colortype; /*color type*/
	data[10] = 0; /*compression method*/
	data[11] = 0; /*filter method*/
	data[12] = interlace_method; /*interlace method*/

	png_chunk_generate_crc(chunk);
	return 0;
}

/* only adds the chunk if needed (there is a key or palette with alpha) */
static u32 addChunk_PLTE(ucvector *out, const pngColorMode *info)
{
	u8 *chunk;
	u32 i, j = 8;

	CERROR_TRY_RETURN(png_chunk_init(&chunk, out, info->palettesize * 3, "PLTE"));

	for (i = 0; i != info->palettesize; ++i) {
		/*add all channels except alpha channel*/
		chunk[j++] = info->palette[i * 4 + 0];
		chunk[j++] = info->palette[i * 4 + 1];
		chunk[j++] = info->palette[i * 4 + 2];
	}

	png_chunk_generate_crc(chunk);
	return 0;
}

static u32 addChunk_tRNS(ucvector *out, const pngColorMode *info)
{
	u8 *chunk = 0;

	if (info->colortype == LCT_PALETTE) {
		u32 i, amount = info->palettesize;
		/*the tail of palette values that all have 255 as alpha, does not have to be encoded*/
		for (i = info->palettesize; i != 0; --i) {
			if (info->palette[4 * (i - 1) + 3] != 255)
				break;
			--amount;
		}
		if (amount) {
			CERROR_TRY_RETURN(png_chunk_init(&chunk, out, amount, "tRNS"));
			/*add the alpha channel values from the palette*/
			for (i = 0; i != amount; ++i)
				chunk[8 + i] = info->palette[4 * i + 3];
		}
	} else if (info->colortype == LCT_GREY) {
		if (info->key_defined) {
			CERROR_TRY_RETURN(png_chunk_init(&chunk, out, 2, "tRNS"));
			chunk[8] = (u8)(info->key_r >> 8);
			chunk[9] = (u8)(info->key_r & 255);
		}
	} else if (info->colortype == LCT_RGB) {
		if (info->key_defined) {
			CERROR_TRY_RETURN(png_chunk_init(&chunk, out, 6, "tRNS"));
			chunk[8] = (u8)(info->key_r >> 8);
			chunk[9] = (u8)(info->key_r & 255);
			chunk[10] = (u8)(info->key_g >> 8);
			chunk[11] = (u8)(info->key_g & 255);
			chunk[12] = (u8)(info->key_b >> 8);
			chunk[13] = (u8)(info->key_b & 255);
		}
	}

	if (chunk)
		png_chunk_generate_crc(chunk);
	return 0;
}

static u32 addChunk_IDAT(ucvector *out, const u8 *data, u32 datasize,
			 pngCompressSettings *zlibsettings)
{
	u32 error = 0;
	u8 *zlib = 0;
	u32 zlibsize = 0;

	error = zlib_compress(&zlib, &zlibsize, data, datasize, zlibsettings);
	if (!error) {
		error = png_chunk_createv(out, zlibsize, "IDAT", zlib);
	}
	png_free(zlib);
	return error;
}

static u32 addChunk_IEND(ucvector *out)
{
	return png_chunk_createv(out, 0, "IEND", 0);
}

#ifdef PNG_COMPILE_ANCILLARY_CHUNKS

static u32 addChunk_tEXt(ucvector *out, const char *keyword, const char *textstring)
{
	u8 *chunk = 0;
	u32 keysize = png_strlen(keyword), textsize = png_strlen(textstring);
	u32 size = keysize + 1 + textsize;
	if (keysize < 1 || keysize > 79)
		return 89; /*error: invalid keyword size*/
	CERROR_TRY_RETURN(png_chunk_init(&chunk, out, size, "tEXt"));
	png_memcpy(chunk + 8, keyword, keysize);
	chunk[8 + keysize] = 0; /*null termination char*/
	png_memcpy(chunk + 9 + keysize, textstring, textsize);
	png_chunk_generate_crc(chunk);
	return 0;
}

static u32 addChunk_zTXt(ucvector *out, const char *keyword, const char *textstring,
			 pngCompressSettings *zlibsettings)
{
	u32 error = 0;
	u8 *chunk = 0;
	u8 *compressed = 0;
	u32 compressedsize = 0;
	u32 textsize = png_strlen(textstring);
	u32 keysize = png_strlen(keyword);
	if (keysize < 1 || keysize > 79)
		return 89; /*error: invalid keyword size*/

	error = zlib_compress(&compressed, &compressedsize, (const u8 *)textstring, textsize,
			      zlibsettings);
	if (!error) {
		u32 size = keysize + 2 + compressedsize;
		error = png_chunk_init(&chunk, out, size, "zTXt");
	}
	if (!error) {
		png_memcpy(chunk + 8, keyword, keysize);
		chunk[8 + keysize] = 0; /*null termination char*/
		chunk[9 + keysize] = 0; /*compression method: 0*/
		png_memcpy(chunk + 10 + keysize, compressed, compressedsize);
		png_chunk_generate_crc(chunk);
	}

	png_free(compressed);
	return error;
}

static u32 addChunk_iTXt(ucvector *out, u32 compress, const char *keyword, const char *langtag,
			 const char *transkey, const char *textstring,
			 pngCompressSettings *zlibsettings)
{
	u32 error = 0;
	u8 *chunk = 0;
	u8 *compressed = 0;
	u32 compressedsize = 0;
	u32 textsize = png_strlen(textstring);
	u32 keysize = png_strlen(keyword), langsize = png_strlen(langtag),
	    transsize = png_strlen(transkey);

	if (keysize < 1 || keysize > 79)
		return 89; /*error: invalid keyword size*/

	if (compress) {
		error = zlib_compress(&compressed, &compressedsize, (const u8 *)textstring,
				      textsize, zlibsettings);
	}
	if (!error) {
		u32 size = keysize + 3 + langsize + 1 + transsize + 1 +
			   (compress ? compressedsize : textsize);
		error = png_chunk_init(&chunk, out, size, "iTXt");
	}
	if (!error) {
		u32 pos = 8;
		png_memcpy(chunk + pos, keyword, keysize);
		pos += keysize;
		chunk[pos++] = 0; /*null termination char*/
		chunk[pos++] = (compress ? 1 : 0); /*compression flag*/
		chunk[pos++] = 0; /*compression method: 0*/
		png_memcpy(chunk + pos, langtag, langsize);
		pos += langsize;
		chunk[pos++] = 0; /*null termination char*/
		png_memcpy(chunk + pos, transkey, transsize);
		pos += transsize;
		chunk[pos++] = 0; /*null termination char*/
		if (compress) {
			png_memcpy(chunk + pos, compressed, compressedsize);
		} else {
			png_memcpy(chunk + pos, textstring, textsize);
		}
		png_chunk_generate_crc(chunk);
	}

	png_free(compressed);
	return error;
}

static u32 addChunk_bKGD(ucvector *out, const pngInfo *info)
{
	u8 *chunk = 0;
	if (info->color.colortype == LCT_GREY || info->color.colortype == LCT_GREY_ALPHA) {
		CERROR_TRY_RETURN(png_chunk_init(&chunk, out, 2, "bKGD"));
		chunk[8] = (u8)(info->background_r >> 8);
		chunk[9] = (u8)(info->background_r & 255);
	} else if (info->color.colortype == LCT_RGB || info->color.colortype == LCT_RGBA) {
		CERROR_TRY_RETURN(png_chunk_init(&chunk, out, 6, "bKGD"));
		chunk[8] = (u8)(info->background_r >> 8);
		chunk[9] = (u8)(info->background_r & 255);
		chunk[10] = (u8)(info->background_g >> 8);
		chunk[11] = (u8)(info->background_g & 255);
		chunk[12] = (u8)(info->background_b >> 8);
		chunk[13] = (u8)(info->background_b & 255);
	} else if (info->color.colortype == LCT_PALETTE) {
		CERROR_TRY_RETURN(png_chunk_init(&chunk, out, 1, "bKGD"));
		chunk[8] = (u8)(info->background_r & 255); /*palette index*/
	}
	if (chunk)
		png_chunk_generate_crc(chunk);
	return 0;
}

static u32 addChunk_tIME(ucvector *out, const pngTime *time)
{
	u8 *chunk;
	CERROR_TRY_RETURN(png_chunk_init(&chunk, out, 7, "tIME"));
	chunk[8] = (u8)(time->year >> 8);
	chunk[9] = (u8)(time->year & 255);
	chunk[10] = (u8)time->month;
	chunk[11] = (u8)time->day;
	chunk[12] = (u8)time->hour;
	chunk[13] = (u8)time->minute;
	chunk[14] = (u8)time->second;
	png_chunk_generate_crc(chunk);
	return 0;
}

static u32 addChunk_pHYs(ucvector *out, const pngInfo *info)
{
	u8 *chunk;
	CERROR_TRY_RETURN(png_chunk_init(&chunk, out, 9, "pHYs"));
	png_set32bitInt(chunk + 8, info->phys_x);
	png_set32bitInt(chunk + 12, info->phys_y);
	chunk[16] = info->phys_unit;
	png_chunk_generate_crc(chunk);
	return 0;
}

static u32 addChunk_gAMA(ucvector *out, const pngInfo *info)
{
	u8 *chunk;
	CERROR_TRY_RETURN(png_chunk_init(&chunk, out, 4, "gAMA"));
	png_set32bitInt(chunk + 8, info->gama_gamma);
	png_chunk_generate_crc(chunk);
	return 0;
}

static u32 addChunk_cHRM(ucvector *out, const pngInfo *info)
{
	u8 *chunk;
	CERROR_TRY_RETURN(png_chunk_init(&chunk, out, 32, "cHRM"));
	png_set32bitInt(chunk + 8, info->chrm_white_x);
	png_set32bitInt(chunk + 12, info->chrm_white_y);
	png_set32bitInt(chunk + 16, info->chrm_red_x);
	png_set32bitInt(chunk + 20, info->chrm_red_y);
	png_set32bitInt(chunk + 24, info->chrm_green_x);
	png_set32bitInt(chunk + 28, info->chrm_green_y);
	png_set32bitInt(chunk + 32, info->chrm_blue_x);
	png_set32bitInt(chunk + 36, info->chrm_blue_y);
	png_chunk_generate_crc(chunk);
	return 0;
}

static u32 addChunk_sRGB(ucvector *out, const pngInfo *info)
{
	u8 data = info->srgb_intent;
	return png_chunk_createv(out, 1, "sRGB", &data);
}

static u32 addChunk_iCCP(ucvector *out, const pngInfo *info, pngCompressSettings *zlibsettings)
{
	u32 error = 0;
	u8 *chunk = 0;
	u8 *compressed = 0;
	u32 compressedsize = 0;
	u32 keysize = png_strlen(info->iccp_name);

	if (keysize < 1 || keysize > 79)
		return 89; /*error: invalid keyword size*/
	error = zlib_compress(&compressed, &compressedsize, info->iccp_profile,
			      info->iccp_profile_size, zlibsettings);
	if (!error) {
		u32 size = keysize + 2 + compressedsize;
		error = png_chunk_init(&chunk, out, size, "iCCP");
	}
	if (!error) {
		png_memcpy(chunk + 8, info->iccp_name, keysize);
		chunk[8 + keysize] = 0; /*null termination char*/
		chunk[9 + keysize] = 0; /*compression method: 0*/
		png_memcpy(chunk + 10 + keysize, compressed, compressedsize);
		png_chunk_generate_crc(chunk);
	}

	png_free(compressed);
	return error;
}

#endif /*PNG_COMPILE_ANCILLARY_CHUNKS*/

static void filterScanline(u8 *out, const u8 *scanline, const u8 *prevline, u32 length,
			   u32 bytewidth, u8 filterType)
{
	u32 i;
	switch (filterType) {
	case 0: /*None*/
		for (i = 0; i != length; ++i)
			out[i] = scanline[i];
		break;
	case 1: /*Sub*/
		for (i = 0; i != bytewidth; ++i)
			out[i] = scanline[i];
		for (i = bytewidth; i < length; ++i)
			out[i] = scanline[i] - scanline[i - bytewidth];
		break;
	case 2: /*Up*/
		if (prevline) {
			for (i = 0; i != length; ++i)
				out[i] = scanline[i] - prevline[i];
		} else {
			for (i = 0; i != length; ++i)
				out[i] = scanline[i];
		}
		break;
	case 3: /*Average*/
		if (prevline) {
			for (i = 0; i != bytewidth; ++i)
				out[i] = scanline[i] - (prevline[i] >> 1);
			for (i = bytewidth; i < length; ++i)
				out[i] = scanline[i] -
					 ((scanline[i - bytewidth] + prevline[i]) >> 1);
		} else {
			for (i = 0; i != bytewidth; ++i)
				out[i] = scanline[i];
			for (i = bytewidth; i < length; ++i)
				out[i] = scanline[i] - (scanline[i - bytewidth] >> 1);
		}
		break;
	case 4: /*Paeth*/
		if (prevline) {
			/*paethPredictor(0, prevline[i], 0) is always prevline[i]*/
			for (i = 0; i != bytewidth; ++i)
				out[i] = (scanline[i] - prevline[i]);
			for (i = bytewidth; i < length; ++i) {
				out[i] = (scanline[i] - paethPredictor(scanline[i - bytewidth],
								       prevline[i],
								       prevline[i - bytewidth]));
			}
		} else {
			for (i = 0; i != bytewidth; ++i)
				out[i] = scanline[i];
			/*paethPredictor(scanline[i - bytewidth], 0, 0) is always scanline[i - bytewidth]*/
			for (i = bytewidth; i < length; ++i)
				out[i] = (scanline[i] - scanline[i - bytewidth]);
		}
		break;
	default:
		return; /*invalid filter type given*/
	}
}

/* integer binary logarithm, max return value is 31 */
static u32 ilog2(u32 i)
{
	u32 result = 0;
	if (i >= 65536) {
		result += 16;
		i >>= 16;
	}
	if (i >= 256) {
		result += 8;
		i >>= 8;
	}
	if (i >= 16) {
		result += 4;
		i >>= 4;
	}
	if (i >= 4) {
		result += 2;
		i >>= 2;
	}
	if (i >= 2) {
		result += 1; /*i >>= 1;*/
	}
	return result;
}

/* integer approximation for i * log2(i), helper function for LFS_ENTROPY */
static u32 ilog2i(u32 i)
{
	u32 l;
	if (i == 0)
		return 0;
	l = ilog2(i);
	/* approximate i*log2(i): l is integer logarithm, ((i - (1u << l)) << 1u)
  linearly approximates the missing fractional part multiplied by i */
	return i * l + ((i - (1u << l)) << 1u);
}

static u32 filter(u8 *out, const u8 *in, u32 w, u32 h, const pngColorMode *color,
		  const pngEncoderSettings *settings)
{
	/*
  For PNG filter method 0
  out must be a buffer with as size: h + (w * h * bpp + 7u) / 8u, because there are
  the scanlines with 1 extra byte per scanline
  */

	u32 bpp = png_get_bpp(color);
	/*the width of a scanline in bytes, not including the filter type*/
	u32 linebytes = png_get_raw_size_idat(w, 1, bpp) - 1u;

	/*bytewidth is used for filtering, is 1 when bpp < 8, number of bytes per pixel otherwise*/
	u32 bytewidth = (bpp + 7u) / 8u;
	const u8 *prevline = 0;
	u32 x, y;
	u32 error = 0;
	pngFilterStrategy strategy = settings->filter_strategy;

	/*
  There is a heuristic called the minimum sum of absolute differences heuristic, suggested by the PNG standard:
   *  If the image type is Palette, or the bit depth is smaller than 8, then do not filter the image (i.e.
      use fixed filtering, with the filter None).
   * (The other case) If the image type is Grayscale or RGB (with or without Alpha), and the bit depth is
     not smaller than 8, then use adaptive filtering heuristic as follows: independently for each row, apply
     all five filters and select the filter that produces the smallest sum of absolute values per row.
  This heuristic is used if filter strategy is LFS_MINSUM and filter_palette_zero is true.

  If filter_palette_zero is true and filter_strategy is not LFS_MINSUM, the above heuristic is followed,
  but for "the other case", whatever strategy filter_strategy is set to instead of the minimum sum
  heuristic is used.
  */
	if (settings->filter_palette_zero &&
	    (color->colortype == LCT_PALETTE || color->bitdepth < 8))
		strategy = LFS_ZERO;

	if (bpp == 0)
		return 31; /*error: invalid color type*/

	if (strategy >= LFS_ZERO && strategy <= LFS_FOUR) {
		u8 type = (u8)strategy;
		for (y = 0; y != h; ++y) {
			u32 outindex =
				(1 + linebytes) * y; /*the extra filterbyte added to each row*/
			u32 inindex = linebytes * y;
			out[outindex] = type; /*filter type byte*/
			filterScanline(&out[outindex + 1], &in[inindex], prevline, linebytes,
				       bytewidth, type);
			prevline = &in[inindex];
		}
	} else if (strategy == LFS_MINSUM) {
		/*adaptive filtering*/
		u8 *attempt[5]; /*five filtering attempts, one for each filter type*/
		u32 smallest = 0;
		u8 type, bestType = 0;

		for (type = 0; type != 5; ++type) {
			attempt[type] = (u8 *)png_malloc(linebytes);
			if (!attempt[type])
				error = 83; /*alloc fail*/
		}

		if (!error) {
			for (y = 0; y != h; ++y) {
				/*try the 5 filter types*/
				for (type = 0; type != 5; ++type) {
					u32 sum = 0;
					filterScanline(attempt[type], &in[y * linebytes], prevline,
						       linebytes, bytewidth, type);

					/*calculate the sum of the result*/
					if (type == 0) {
						for (x = 0; x != linebytes; ++x)
							sum += (u8)(attempt[type][x]);
					} else {
						for (x = 0; x != linebytes; ++x) {
							/*For differences, each byte should be treated as signed, values above 127 are negative
              (converted to signed char). Filtertype 0 isn't a difference though, so use u32 there.
              This means filtertype 0 is almost never chosen, but that is justified.*/
							u8 s = attempt[type][x];
							sum += s < 128 ? s : (255U - s);
						}
					}

					/*check if this is smallest sum (or if type == 0 it's the first case so always store the values)*/
					if (type == 0 || sum < smallest) {
						bestType = type;
						smallest = sum;
					}
				}

				prevline = &in[y * linebytes];

				/*now fill the out values*/
				out[y * (linebytes + 1)] =
					bestType; /*the first byte of a scanline will be the filter type*/
				for (x = 0; x != linebytes; ++x)
					out[y * (linebytes + 1) + 1 + x] = attempt[bestType][x];
			}
		}

		for (type = 0; type != 5; ++type)
			png_free(attempt[type]);
	} else if (strategy == LFS_ENTROPY) {
		u8 *attempt[5]; /*five filtering attempts, one for each filter type*/
		u32 bestSum = 0;
		u32 type, bestType = 0;
		u32 count[256];

		for (type = 0; type != 5; ++type) {
			attempt[type] = (u8 *)png_malloc(linebytes);
			if (!attempt[type])
				error = 83; /*alloc fail*/
		}

		if (!error) {
			for (y = 0; y != h; ++y) {
				/*try the 5 filter types*/
				for (type = 0; type != 5; ++type) {
					u32 sum = 0;
					filterScanline(attempt[type], &in[y * linebytes], prevline,
						       linebytes, bytewidth, type);
					png_memset(count, 0, 256 * sizeof(*count));
					for (x = 0; x != linebytes; ++x)
						++count[attempt[type][x]];
					++count[type]; /*the filter type itself is part of the scanline*/
					for (x = 0; x != 256; ++x) {
						sum += ilog2i(count[x]);
					}
					/*check if this is smallest sum (or if type == 0 it's the first case so always store the values)*/
					if (type == 0 || sum > bestSum) {
						bestType = type;
						bestSum = sum;
					}
				}

				prevline = &in[y * linebytes];

				/*now fill the out values*/
				out[y * (linebytes + 1)] =
					bestType; /*the first byte of a scanline will be the filter type*/
				for (x = 0; x != linebytes; ++x)
					out[y * (linebytes + 1) + 1 + x] = attempt[bestType][x];
			}
		}

		for (type = 0; type != 5; ++type)
			png_free(attempt[type]);
	} else if (strategy == LFS_PREDEFINED) {
		for (y = 0; y != h; ++y) {
			u32 outindex =
				(1 + linebytes) * y; /*the extra filterbyte added to each row*/
			u32 inindex = linebytes * y;
			u8 type = settings->predefined_filters[y];
			out[outindex] = type; /*filter type byte*/
			filterScanline(&out[outindex + 1], &in[inindex], prevline, linebytes,
				       bytewidth, type);
			prevline = &in[inindex];
		}
	} else if (strategy == LFS_BRUTE_FORCE) {
		/*brute force filter chooser.
    deflate the scanline after every filter attempt to see which one deflates best.
    This is very slow and gives only slightly smaller, sometimes even larger, result*/
		u32 size[5];
		u8 *attempt[5]; /*five filtering attempts, one for each filter type*/
		u32 smallest = 0;
		u32 type = 0, bestType = 0;
		u8 *dummy;
		pngCompressSettings zlibsettings;
		png_memcpy(&zlibsettings, &settings->zlibsettings, sizeof(pngCompressSettings));
		/*use fixed tree on the attempts so that the tree is not adapted to the filtertype on purpose,
    to simulate the true case where the tree is the same for the whole image. Sometimes it gives
    better result with dynamic tree anyway. Using the fixed tree sometimes gives worse, but in rare
    cases better compression. It does make this a bit less slow, so it's worth doing this.*/
		zlibsettings.btype = 1;
		/*a custom encoder likely doesn't read the btype setting and is optimized for complete PNG
    images only, so disable it*/
		zlibsettings.custom_zlib = 0;
		zlibsettings.custom_deflate = 0;
		for (type = 0; type != 5; ++type) {
			attempt[type] = (u8 *)png_malloc(linebytes);
			if (!attempt[type])
				error = 83; /*alloc fail*/
		}
		if (!error) {
			for (y = 0; y != h; ++y) /*try the 5 filter types*/ {
				for (type = 0; type != 5; ++type) {
					u32 testsize = (u32)linebytes;
					/*if(testsize > 8) testsize /= 8;*/ /*it already works good enough by testing a part of the row*/

					filterScanline(attempt[type], &in[y * linebytes], prevline,
						       linebytes, bytewidth, type);
					size[type] = 0;
					dummy = 0;
					zlib_compress(&dummy, &size[type], attempt[type], testsize,
						      &zlibsettings);
					png_free(dummy);
					/*check if this is smallest size (or if type == 0 it's the first case so always store the values)*/
					if (type == 0 || size[type] < smallest) {
						bestType = type;
						smallest = size[type];
					}
				}
				prevline = &in[y * linebytes];
				out[y * (linebytes + 1)] =
					bestType; /*the first byte of a scanline will be the filter type*/
				for (x = 0; x != linebytes; ++x)
					out[y * (linebytes + 1) + 1 + x] = attempt[bestType][x];
			}
		}
		for (type = 0; type != 5; ++type)
			png_free(attempt[type]);
	} else
		return 88; /* unknown filter strategy */

	return error;
}

static void addPaddingBits(u8 *out, const u8 *in, u32 olinebits, u32 ilinebits, u32 h)
{
	/*The opposite of the removePaddingBits function
  olinebits must be >= ilinebits*/
	u32 y;
	u32 diff = olinebits - ilinebits;
	u32 obp = 0, ibp = 0; /*bit pointers*/
	for (y = 0; y != h; ++y) {
		u32 x;
		for (x = 0; x < ilinebits; ++x) {
			u8 bit = readBitFromReversedStream(&ibp, in);
			setBitOfReversedStream(&obp, out, bit);
		}
		/*obp += diff; --> no, fill in some value in the padding bits too, to avoid
    "Use of uninitialised value of size ###" warning from valgrind*/
		for (x = 0; x != diff; ++x)
			setBitOfReversedStream(&obp, out, 0);
	}
}

/*
in: non-interlaced image with size w*h
out: the same pixels, but re-ordered according to PNG's Adam7 interlacing, with
 no padding bits between scanlines, but between reduced images so that each
 reduced image starts at a byte.
bpp: bits per pixel
there are no padding bits, not between scanlines, not between reduced images
in has the following size in bits: w * h * bpp.
out is possibly bigger due to padding bits between reduced images
NOTE: comments about padding bits are only relevant if bpp < 8
*/
static void Adam7_interlace(u8 *out, const u8 *in, u32 w, u32 h, u32 bpp)
{
	u32 passw[7], passh[7];
	u32 filter_passstart[8], padded_passstart[8], passstart[8];
	u32 i;

	Adam7_getpassvalues(passw, passh, filter_passstart, padded_passstart, passstart, w, h, bpp);

	if (bpp >= 8) {
		for (i = 0; i != 7; ++i) {
			u32 x, y, b;
			u32 bytewidth = bpp / 8u;
			for (y = 0; y < passh[i]; ++y)
				for (x = 0; x < passw[i]; ++x) {
					u32 pixelinstart = ((ADAM7_IY[i] + y * ADAM7_DY[i]) * w +
							    ADAM7_IX[i] + x * ADAM7_DX[i]) *
							   bytewidth;
					u32 pixeloutstart =
						passstart[i] + (y * passw[i] + x) * bytewidth;
					for (b = 0; b < bytewidth; ++b) {
						out[pixeloutstart + b] = in[pixelinstart + b];
					}
				}
		}
	} else /*bpp < 8: Adam7 with pixels < 8 bit is a bit trickier: with bit pointers*/ {
		for (i = 0; i != 7; ++i) {
			u32 x, y, b;
			u32 ilinebits = bpp * passw[i];
			u32 olinebits = bpp * w;
			u32 obp, ibp; /*bit pointers (for out and in buffer)*/
			for (y = 0; y < passh[i]; ++y)
				for (x = 0; x < passw[i]; ++x) {
					ibp = (ADAM7_IY[i] + y * ADAM7_DY[i]) * olinebits +
					      (ADAM7_IX[i] + x * ADAM7_DX[i]) * bpp;
					obp = (8 * passstart[i]) + (y * ilinebits + x * bpp);
					for (b = 0; b < bpp; ++b) {
						u8 bit = readBitFromReversedStream(&ibp, in);
						setBitOfReversedStream(&obp, out, bit);
					}
				}
		}
	}
}

/*out must be buffer big enough to contain uncompressed IDAT chunk data, and in must contain the full image.
return value is error**/
static u32 preProcessScanlines(u8 **out, u32 *outsize, const u8 *in, u32 w, u32 h,
			       const pngInfo *info_png, const pngEncoderSettings *settings)
{
	/*
  This function converts the pure 2D image with the PNG's colortype, into filtered-padded-interlaced data. Steps:
  *) if no Adam7: 1) add padding bits (= possible extra bits per scanline if bpp < 8) 2) filter
  *) if adam7: 1) Adam7_interlace 2) 7x add padding bits 3) 7x filter
  */
	u32 bpp = png_get_bpp(&info_png->color);
	u32 error = 0;

	if (info_png->interlace_method == 0) {
		*outsize =
			h +
			(h *
			 ((w * bpp + 7u) /
			  8u)); /*image size plus an extra byte per scanline + possible padding bits*/
		*out = (u8 *)png_malloc(*outsize);
		if (!(*out) && (*outsize))
			error = 83; /*alloc fail*/

		if (!error) {
			/*non multiple of 8 bits per scanline, padding bits needed per scanline*/
			if (bpp < 8 && w * bpp != ((w * bpp + 7u) / 8u) * 8u) {
				u8 *padded = (u8 *)png_malloc(h * ((w * bpp + 7u) / 8u));
				if (!padded)
					error = 83; /*alloc fail*/
				if (!error) {
					addPaddingBits(padded, in, ((w * bpp + 7u) / 8u) * 8u,
						       w * bpp, h);
					error = filter(*out, padded, w, h, &info_png->color,
						       settings);
				}
				png_free(padded);
			} else {
				/*we can immediately filter into the out buffer, no other steps needed*/
				error = filter(*out, in, w, h, &info_png->color, settings);
			}
		}
	} else /*interlace_method is 1 (Adam7)*/ {
		u32 passw[7], passh[7];
		u32 filter_passstart[8], padded_passstart[8], passstart[8];
		u8 *adam7;

		Adam7_getpassvalues(passw, passh, filter_passstart, padded_passstart, passstart, w,
				    h, bpp);

		*outsize = filter_passstart
			[7]; /*image size plus an extra byte per scanline + possible padding bits*/
		*out = (u8 *)png_malloc(*outsize);
		if (!(*out))
			error = 83; /*alloc fail*/

		adam7 = (u8 *)png_malloc(passstart[7]);
		if (!adam7 && passstart[7])
			error = 83; /*alloc fail*/

		if (!error) {
			u32 i;

			Adam7_interlace(adam7, in, w, h, bpp);
			for (i = 0; i != 7; ++i) {
				if (bpp < 8) {
					u8 *padded = (u8 *)png_malloc(padded_passstart[i + 1] -
								      padded_passstart[i]);
					if (!padded)
						ERROR_BREAK(83); /*alloc fail*/
					addPaddingBits(padded, &adam7[passstart[i]],
						       ((passw[i] * bpp + 7u) / 8u) * 8u,
						       passw[i] * bpp, passh[i]);
					error = filter(&(*out)[filter_passstart[i]], padded,
						       passw[i], passh[i], &info_png->color,
						       settings);
					png_free(padded);
				} else {
					error = filter(&(*out)[filter_passstart[i]],
						       &adam7[padded_passstart[i]], passw[i],
						       passh[i], &info_png->color, settings);
				}

				if (error)
					break;
			}
		}

		png_free(adam7);
	}

	return error;
}

#ifdef PNG_COMPILE_ANCILLARY_CHUNKS
static u32 addUnknownChunks(ucvector *out, u8 *data, u32 datasize)
{
	u8 *inchunk = data;
	while ((u32)(inchunk - data) < datasize) {
		CERROR_TRY_RETURN(png_chunk_append(&out->data, &out->size, inchunk));
		out->allocsize = out->size; /*fix the allocsize again*/
		inchunk = png_chunk_next(inchunk, data + datasize);
	}
	return 0;
}

static u32 isGrayICCProfile(const u8 *profile, u32 size)
{
	/*
  It is a gray profile if bytes 16-19 are "GRAY", rgb profile if bytes 16-19
  are "RGB ". We do not perform any full parsing of the ICC profile here, other
  than check those 4 bytes to grayscale profile. Other than that, validity of
  the profile is not checked. This is needed only because the PNG specification
  requires using a non-gray color model if there is an ICC profile with "RGB "
  (sadly limiting compression opportunities if the input data is grayscale RGB
  data), and requires using a gray color model if it is "GRAY".
  */
	if (size < 20)
		return 0;
	return profile[16] == 'G' && profile[17] == 'R' && profile[18] == 'A' && profile[19] == 'Y';
}

static u32 isRGBICCProfile(const u8 *profile, u32 size)
{
	/* See comment in isGrayICCProfile*/
	if (size < 20)
		return 0;
	return profile[16] == 'R' && profile[17] == 'G' && profile[18] == 'B' && profile[19] == ' ';
}
#endif /*PNG_COMPILE_ANCILLARY_CHUNKS*/

u32 png_encode(u8 **out, u32 *outsize, const u8 *image, u32 w, u32 h, pngState *state)
{
	u8 *data = 0; /*uncompressed version of the IDAT chunk data*/
	u32 datasize = 0;
	ucvector outv = ucvector_init(NULL, 0);
	pngInfo info;
	const pngInfo *info_png = &state->info_png;

	png_info_init(&info);

	/*provide some proper output values if error will happen*/
	*out = 0;
	*outsize = 0;
	state->error = 0;

	/*check input values validity*/
	if ((info_png->color.colortype == LCT_PALETTE || state->encoder.force_palette) &&
	    (info_png->color.palettesize == 0 || info_png->color.palettesize > 256)) {
		state->error = 68; /*invalid palette size, it is only allowed to be 1-256*/
		goto cleanup;
	}
	if (state->encoder.zlibsettings.btype > 2) {
		state->error = 61; /*error: invalid btype*/
		goto cleanup;
	}
	if (info_png->interlace_method > 1) {
		state->error = 71; /*error: invalid interlace mode*/
		goto cleanup;
	}
	state->error = checkColorValidity(info_png->color.colortype, info_png->color.bitdepth);
	if (state->error)
		goto cleanup; /*error: invalid color type given*/
	state->error = checkColorValidity(state->info_raw.colortype, state->info_raw.bitdepth);
	if (state->error)
		goto cleanup; /*error: invalid color type given*/

	/* color convert and compute scanline filter types */
	png_info_copy(&info, &state->info_png);
	if (state->encoder.auto_convert) {
		pngColorStats stats;
		png_color_stats_init(&stats);
#ifdef PNG_COMPILE_ANCILLARY_CHUNKS
		if (info_png->iccp_defined &&
		    isGrayICCProfile(info_png->iccp_profile, info_png->iccp_profile_size)) {
			/*the PNG specification does not allow to use palette with a GRAY ICC profile, even
      if the palette has only gray colors, so disallow it.*/
			stats.allow_palette = 0;
		}
		if (info_png->iccp_defined &&
		    isRGBICCProfile(info_png->iccp_profile, info_png->iccp_profile_size)) {
			/*the PNG specification does not allow to use grayscale color with RGB ICC profile, so disallow gray.*/
			stats.allow_greyscale = 0;
		}
#endif /* PNG_COMPILE_ANCILLARY_CHUNKS */
		state->error = png_compute_color_stats(&stats, image, w, h, &state->info_raw);
		if (state->error)
			goto cleanup;
#ifdef PNG_COMPILE_ANCILLARY_CHUNKS
		if (info_png->background_defined) {
			/*the background chunk's color must be taken into account as well*/
			u32 r = 0, g = 0, b = 0;
			pngColorMode mode16 = png_color_mode_make(LCT_RGB, 16);
			png_convert_rgb(&r, &g, &b, info_png->background_r, info_png->background_g,
					info_png->background_b, &mode16, &info_png->color);
			state->error = png_color_stats_add(&stats, r, g, b, 65535);
			if (state->error)
				goto cleanup;
		}
#endif /* PNG_COMPILE_ANCILLARY_CHUNKS */
		state->error = auto_choose_color(&info.color, &state->info_raw, &stats);
		if (state->error)
			goto cleanup;
#ifdef PNG_COMPILE_ANCILLARY_CHUNKS
		/*also convert the background chunk*/
		if (info_png->background_defined) {
			if (png_convert_rgb(&info.background_r, &info.background_g,
					    &info.background_b, info_png->background_r,
					    info_png->background_g, info_png->background_b,
					    &info.color, &info_png->color)) {
				state->error = 104;
				goto cleanup;
			}
		}
#endif /* PNG_COMPILE_ANCILLARY_CHUNKS */
	}
#ifdef PNG_COMPILE_ANCILLARY_CHUNKS
	if (info_png->iccp_defined) {
		u32 gray_icc =
			isGrayICCProfile(info_png->iccp_profile, info_png->iccp_profile_size);
		u32 rgb_icc = isRGBICCProfile(info_png->iccp_profile, info_png->iccp_profile_size);
		u32 gray_png =
			info.color.colortype == LCT_GREY || info.color.colortype == LCT_GREY_ALPHA;
		if (!gray_icc && !rgb_icc) {
			state->error = 100; /* Disallowed profile color type for PNG */
			goto cleanup;
		}
		if (gray_icc != gray_png) {
			/*Not allowed to use RGB/RGBA/palette with GRAY ICC profile or vice versa,
      or in case of auto_convert, it wasn't possible to find appropriate model*/
			state->error = state->encoder.auto_convert ? 102 : 101;
			goto cleanup;
		}
	}
#endif /*PNG_COMPILE_ANCILLARY_CHUNKS*/
	if (!png_color_mode_equal(&state->info_raw, &info.color)) {
		u8 *converted;
		u32 size = ((u32)w * (u32)h * (u32)png_get_bpp(&info.color) + 7u) / 8u;

		converted = (u8 *)png_malloc(size);
		if (!converted && size)
			state->error = 83; /*alloc fail*/
		if (!state->error) {
			state->error =
				png_convert(converted, image, &info.color, &state->info_raw, w, h);
		}
		if (!state->error) {
			state->error = preProcessScanlines(&data, &datasize, converted, w, h, &info,
							   &state->encoder);
		}
		png_free(converted);
		if (state->error)
			goto cleanup;
	} else {
		state->error =
			preProcessScanlines(&data, &datasize, image, w, h, &info, &state->encoder);
		if (state->error)
			goto cleanup;
	}

	/* output all PNG chunks */ {
#ifdef PNG_COMPILE_ANCILLARY_CHUNKS
		u32 i;
#endif /*PNG_COMPILE_ANCILLARY_CHUNKS*/
		/*write signature and chunks*/
		state->error = writeSignature(&outv);
		if (state->error)
			goto cleanup;
		/*IHDR*/
		state->error = addChunk_IHDR(&outv, w, h, info.color.colortype, info.color.bitdepth,
					     info.interlace_method);
		if (state->error)
			goto cleanup;
#ifdef PNG_COMPILE_ANCILLARY_CHUNKS
		/*unknown chunks between IHDR and PLTE*/
		if (info.unknown_chunks_data[0]) {
			state->error = addUnknownChunks(&outv, info.unknown_chunks_data[0],
							info.unknown_chunks_size[0]);
			if (state->error)
				goto cleanup;
		}
		/*color profile chunks must come before PLTE */
		if (info.iccp_defined) {
			state->error = addChunk_iCCP(&outv, &info, &state->encoder.zlibsettings);
			if (state->error)
				goto cleanup;
		}
		if (info.srgb_defined) {
			state->error = addChunk_sRGB(&outv, &info);
			if (state->error)
				goto cleanup;
		}
		if (info.gama_defined) {
			state->error = addChunk_gAMA(&outv, &info);
			if (state->error)
				goto cleanup;
		}
		if (info.chrm_defined) {
			state->error = addChunk_cHRM(&outv, &info);
			if (state->error)
				goto cleanup;
		}
#endif /*PNG_COMPILE_ANCILLARY_CHUNKS*/
		/*PLTE*/
		if (info.color.colortype == LCT_PALETTE) {
			state->error = addChunk_PLTE(&outv, &info.color);
			if (state->error)
				goto cleanup;
		}
		if (state->encoder.force_palette &&
		    (info.color.colortype == LCT_RGB || info.color.colortype == LCT_RGBA)) {
			/*force_palette means: write suggested palette for truecolor in PLTE chunk*/
			state->error = addChunk_PLTE(&outv, &info.color);
			if (state->error)
				goto cleanup;
		}
		/*tRNS (this will only add if when necessary) */
		state->error = addChunk_tRNS(&outv, &info.color);
		if (state->error)
			goto cleanup;
#ifdef PNG_COMPILE_ANCILLARY_CHUNKS
		/*bKGD (must come between PLTE and the IDAt chunks*/
		if (info.background_defined) {
			state->error = addChunk_bKGD(&outv, &info);
			if (state->error)
				goto cleanup;
		}
		/*pHYs (must come before the IDAT chunks)*/
		if (info.phys_defined) {
			state->error = addChunk_pHYs(&outv, &info);
			if (state->error)
				goto cleanup;
		}

		/*unknown chunks between PLTE and IDAT*/
		if (info.unknown_chunks_data[1]) {
			state->error = addUnknownChunks(&outv, info.unknown_chunks_data[1],
							info.unknown_chunks_size[1]);
			if (state->error)
				goto cleanup;
		}
#endif /*PNG_COMPILE_ANCILLARY_CHUNKS*/
		/*IDAT (multiple IDAT chunks must be consecutive)*/
		state->error = addChunk_IDAT(&outv, data, datasize, &state->encoder.zlibsettings);
		if (state->error)
			goto cleanup;
#ifdef PNG_COMPILE_ANCILLARY_CHUNKS
		/*tIME*/
		if (info.time_defined) {
			state->error = addChunk_tIME(&outv, &info.time);
			if (state->error)
				goto cleanup;
		}
		/*tEXt and/or zTXt*/
		for (i = 0; i != info.text_num; ++i) {
			if (png_strlen(info.text_keys[i]) > 79) {
				state->error = 66; /*text chunk too large*/
				goto cleanup;
			}
			if (png_strlen(info.text_keys[i]) < 1) {
				state->error = 67; /*text chunk too small*/
				goto cleanup;
			}
			if (state->encoder.text_compression) {
				state->error = addChunk_zTXt(&outv, info.text_keys[i],
							     info.text_strings[i],
							     &state->encoder.zlibsettings);
				if (state->error)
					goto cleanup;
			} else {
				state->error = addChunk_tEXt(&outv, info.text_keys[i],
							     info.text_strings[i]);
				if (state->error)
					goto cleanup;
			}
		}
		/*png version id in text chunk*/
		if (state->encoder.add_id) {
			u32 already_added_id_text = 0;
			for (i = 0; i != info.text_num; ++i) {
				const char *k = info.text_keys[i];
				/* Could use strcmp, but we're not calling or reimplementing this C library function for this use only */
				if (k[0] == 'L' && k[1] == 'o' && k[2] == 'd' && k[3] == 'e' &&
				    k[4] == 'P' && k[5] == 'N' && k[6] == 'G' && k[7] == '\0') {
					already_added_id_text = 1;
					break;
				}
			}
			if (already_added_id_text == 0) {
				state->error = addChunk_tEXt(
					&outv, "png",
					PNG_VERSION_STRING); /*it's shorter as tEXt than as zTXt chunk*/
				if (state->error)
					goto cleanup;
			}
		}
		/*iTXt*/
		for (i = 0; i != info.itext_num; ++i) {
			if (png_strlen(info.itext_keys[i]) > 79) {
				state->error = 66; /*text chunk too large*/
				goto cleanup;
			}
			if (png_strlen(info.itext_keys[i]) < 1) {
				state->error = 67; /*text chunk too small*/
				goto cleanup;
			}
			state->error = addChunk_iTXt(&outv, state->encoder.text_compression,
						     info.itext_keys[i], info.itext_langtags[i],
						     info.itext_transkeys[i], info.itext_strings[i],
						     &state->encoder.zlibsettings);
			if (state->error)
				goto cleanup;
		}

		/*unknown chunks between IDAT and IEND*/
		if (info.unknown_chunks_data[2]) {
			state->error = addUnknownChunks(&outv, info.unknown_chunks_data[2],
							info.unknown_chunks_size[2]);
			if (state->error)
				goto cleanup;
		}
#endif /*PNG_COMPILE_ANCILLARY_CHUNKS*/
		state->error = addChunk_IEND(&outv);
		if (state->error)
			goto cleanup;
	}

cleanup:
	png_info_cleanup(&info);
	png_free(data);

	/*instead of cleaning the vector up, give it to the output*/
	*out = outv.data;
	*outsize = outv.size;

	return state->error;
}

u32 png_encode_memory(u8 **out, u32 *outsize, const u8 *image, u32 w, u32 h, pngColorType colortype,
		      u32 bitdepth)
{
	u32 error;
	pngState state;
	png_state_init(&state);
	state.info_raw.colortype = colortype;
	state.info_raw.bitdepth = bitdepth;
	state.info_png.color.colortype = colortype;
	state.info_png.color.bitdepth = bitdepth;
	png_encode(out, outsize, image, w, h, &state);
	error = state.error;
	png_state_cleanup(&state);
	return error;
}

u32 png_encode32(u8 **out, u32 *outsize, const u8 *image, u32 w, u32 h)
{
	return png_encode_memory(out, outsize, image, w, h, LCT_RGBA, 8);
}

u32 png_encode24(u8 **out, u32 *outsize, const u8 *image, u32 w, u32 h)
{
	return png_encode_memory(out, outsize, image, w, h, LCT_RGB, 8);
}

#ifdef PNG_COMPILE_DISK
u32 png_encode_file(const char *filename, const u8 *image, u32 w, u32 h, pngColorType colortype,
		    u32 bitdepth)
{
	u8 *buffer;
	u32 buffersize;
	u32 error = png_encode_memory(&buffer, &buffersize, image, w, h, colortype, bitdepth);
	if (!error)
		error = png_save_file(buffer, buffersize, filename);
	png_free(buffer);
	return error;
}

u32 png_encode32_file(const char *filename, const u8 *image, u32 w, u32 h)
{
	return png_encode_file(filename, image, w, h, LCT_RGBA, 8);
}

u32 png_encode24_file(const char *filename, const u8 *image, u32 w, u32 h)
{
	return png_encode_file(filename, image, w, h, LCT_RGB, 8);
}
#endif /*PNG_COMPILE_DISK*/

void png_encoder_settings_init(pngEncoderSettings *settings)
{
	png_compress_settings_init(&settings->zlibsettings);
	settings->filter_palette_zero = 1;
	settings->filter_strategy = LFS_MINSUM;
	settings->auto_convert = 1;
	settings->force_palette = 0;
	settings->predefined_filters = 0;
#ifdef PNG_COMPILE_ANCILLARY_CHUNKS
	settings->add_id = 0;
	settings->text_compression = 1;
#endif /*PNG_COMPILE_ANCILLARY_CHUNKS*/
}

#endif /*PNG_COMPILE_ENCODER*/
#endif /*PNG_COMPILE_PNG*/

#ifdef PNG_COMPILE_ERROR_TEXT
/*
This returns the description of a numerical error code in English. This is also
the documentation of all the error codes.
*/
const char *png_error_text(u32 code)
{
	switch (code) {
	case 0:
		return "no error, everything went ok";
	case 1:
		return "nothing done yet"; /*the Encoder/Decoder has done nothing yet, error checking makes no sense yet*/
	case 10:
		return "end of input memory reached without huffman end code"; /*while huffman decoding*/
	case 11:
		return "error in code tree made it jump outside of huffman tree"; /*while huffman decoding*/
	case 13:
		return "problem while processing dynamic deflate block";
	case 14:
		return "problem while processing dynamic deflate block";
	case 15:
		return "problem while processing dynamic deflate block";
	/*this error could happen if there are only 0 or 1 symbols present in the huffman code:*/
	case 16:
		return "invalid code while processing dynamic deflate block";
	case 17:
		return "end of out buffer memory reached while inflating";
	case 18:
		return "invalid distance code while inflating";
	case 19:
		return "end of out buffer memory reached while inflating";
	case 20:
		return "invalid deflate block BTYPE encountered while decoding";
	case 21:
		return "NLEN is not ones complement of LEN in a deflate block";

	/*end of out buffer memory reached while inflating:
    This can happen if the inflated deflate data is longer than the amount of bytes required to fill up
    all the pixels of the image, given the color depth and image dimensions. Something that doesn't
    happen in a normal, well encoded, PNG image.*/
	case 22:
		return "end of out buffer memory reached while inflating";
	case 23:
		return "end of in buffer memory reached while inflating";
	case 24:
		return "invalid FCHECK in zlib header";
	case 25:
		return "invalid compression method in zlib header";
	case 26:
		return "FDICT encountered in zlib header while it's not used for PNG";
	case 27:
		return "PNG file is smaller than a PNG header";
	/*Checks the magic file header, the first 8 bytes of the PNG file*/
	case 28:
		return "incorrect PNG signature, it's no PNG or corrupted";
	case 29:
		return "first chunk is not the header chunk";
	case 30:
		return "chunk length too large, chunk broken off at end of file";
	case 31:
		return "illegal PNG color type or bpp";
	case 32:
		return "illegal PNG compression method";
	case 33:
		return "illegal PNG filter method";
	case 34:
		return "illegal PNG interlace method";
	case 35:
		return "chunk length of a chunk is too large or the chunk too small";
	case 36:
		return "illegal PNG filter type encountered";
	case 37:
		return "illegal bit depth for this color type given";
	case 38:
		return "the palette is too small or too big"; /*0, or more than 256 colors*/
	case 39:
		return "tRNS chunk before PLTE or has more entries than palette size";
	case 40:
		return "tRNS chunk has wrong size for grayscale image";
	case 41:
		return "tRNS chunk has wrong size for RGB image";
	case 42:
		return "tRNS chunk appeared while it was not allowed for this color type";
	case 43:
		return "bKGD chunk has wrong size for palette image";
	case 44:
		return "bKGD chunk has wrong size for grayscale image";
	case 45:
		return "bKGD chunk has wrong size for RGB image";
	case 48:
		return "empty input buffer given to decoder. Maybe caused by non-existing file?";
	case 49:
		return "jumped past memory while generating dynamic huffman tree";
	case 50:
		return "jumped past memory while generating dynamic huffman tree";
	case 51:
		return "jumped past memory while inflating huffman block";
	case 52:
		return "jumped past memory while inflating";
	case 53:
		return "size of zlib data too small";
	case 54:
		return "repeat symbol in tree while there was no value symbol yet";
	/*jumped past tree while generating huffman tree, this could be when the
    tree will have more leaves than symbols after generating it out of the
    given lengths. They call this an oversubscribed dynamic bit lengths tree in zlib.*/
	case 55:
		return "jumped past tree while generating huffman tree";
	case 56:
		return "given output image colortype or bitdepth not supported for color conversion";
	case 57:
		return "invalid CRC encountered (checking CRC can be disabled)";
	case 58:
		return "invalid ADLER32 encountered (checking ADLER32 can be disabled)";
	case 59:
		return "requested color conversion not supported";
	case 60:
		return "invalid window size given in the settings of the encoder (must be 0-32768)";
	case 61:
		return "invalid BTYPE given in the settings of the encoder (only 0, 1 and 2 are allowed)";
	/*png leaves the choice of RGB to grayscale conversion formula to the user.*/
	case 62:
		return "conversion from color to grayscale not supported";
	/*(2^31-1)*/
	case 63:
		return "length of a chunk too long, max allowed for PNG is 2147483647 bytes per chunk";
	/*this would result in the inability of a deflated block to ever contain an end code. It must be at least 1.*/
	case 64:
		return "the length of the END symbol 256 in the Huffman tree is 0";
	case 66:
		return "the length of a text chunk keyword given to the encoder is longer than the maximum of 79 bytes";
	case 67:
		return "the length of a text chunk keyword given to the encoder is smaller than the minimum of 1 byte";
	case 68:
		return "tried to encode a PLTE chunk with a palette that has less than 1 or more than 256 colors";
	case 69:
		return "unknown chunk type with 'critical' flag encountered by the decoder";
	case 71:
		return "invalid interlace mode given to encoder (must be 0 or 1)";
	case 72:
		return "while decoding, invalid compression method encountering in zTXt or iTXt chunk (it must be 0)";
	case 73:
		return "invalid tIME chunk size";
	case 74:
		return "invalid pHYs chunk size";
	/*length could be wrong, or data chopped off*/
	case 75:
		return "no null termination char found while decoding text chunk";
	case 76:
		return "iTXt chunk too short to contain required bytes";
	case 77:
		return "integer overflow in buffer size";
	case 78:
		return "failed to open file for reading"; /*file doesn't exist or couldn't be opened for reading*/
	case 79:
		return "failed to open file for writing";
	case 80:
		return "tried creating a tree of 0 symbols";
	case 81:
		return "lazy matching at pos 0 is impossible";
	case 82:
		return "color conversion to palette requested while a color isn't in palette, or index out of bounds";
	case 83:
		return "memory allocation failed";
	case 84:
		return "given image too small to contain all pixels to be encoded";
	case 86:
		return "impossible offset in lz77 encoding (internal bug)";
	case 87:
		return "must provide custom zlib function pointer if PNG_COMPILE_ZLIB is not defined";
	case 88:
		return "invalid filter strategy given for pngEncoderSettings.filter_strategy";
	case 89:
		return "text chunk keyword too short or long: must have size 1-79";
	/*the windowsize in the pngCompressSettings. Requiring POT(==> & instead of %) makes encoding 12% faster.*/
	case 90:
		return "windowsize must be a power of two";
	case 91:
		return "invalid decompressed idat size";
	case 92:
		return "integer overflow due to too many pixels";
	case 93:
		return "zero width or height is invalid";
	case 94:
		return "header chunk must have a size of 13 bytes";
	case 95:
		return "integer overflow with combined idat chunk size";
	case 96:
		return "invalid gAMA chunk size";
	case 97:
		return "invalid cHRM chunk size";
	case 98:
		return "invalid sRGB chunk size";
	case 99:
		return "invalid sRGB rendering intent";
	case 100:
		return "invalid ICC profile color type, the PNG specification only allows RGB or GRAY";
	case 101:
		return "PNG specification does not allow RGB ICC profile on gray color types and vice versa";
	case 102:
		return "not allowed to set grayscale ICC profile with colored pixels by PNG specification";
	case 103:
		return "invalid palette index in bKGD chunk. Maybe it came before PLTE chunk?";
	case 104:
		return "invalid bKGD color while encoding (e.g. palette index out of range)";
	case 105:
		return "integer overflow of bitsize";
	case 106:
		return "PNG file must have PLTE chunk if color type is palette";
	case 107:
		return "color convert from palette mode requested without setting the palette data in it";
	case 108:
		return "tried to add more than 256 values to a palette";
	/*this limit can be configured in pngDecompressSettings*/
	case 109:
		return "tried to decompress zlib or deflate data larger than desired max_output_size";
	case 110:
		return "custom zlib or inflate decompression failed";
	case 111:
		return "custom zlib or deflate compression failed";
	/*max text size limit can be configured in pngDecoderSettings. This error prevents
    unreasonable memory consumption when decoding due to impossibly large text sizes.*/
	case 112:
		return "compressed text unreasonably large";
	/*max ICC size limit can be configured in pngDecoderSettings. This error prevents
    unreasonable memory consumption when decoding due to impossibly large ICC profile*/
	case 113:
		return "ICC profile unreasonably large";
	default:
		return "unknown error code";
	}
}
#endif /*PNG_COMPILE_ERROR_TEXT*/

/* ////////////////////////////////////////////////////////////////////////// */
/* ////////////////////////////////////////////////////////////////////////// */
/* // C++ Wrapper                                                          // */
/* ////////////////////////////////////////////////////////////////////////// */
/* ////////////////////////////////////////////////////////////////////////// */

#ifdef PNG_COMPILE_CPP
namespace png
{
#ifdef PNG_COMPILE_DISK
u32 load_file(std::vector<u8> &buffer, const std::string &filename)
{
	long size = png_filesize(filename.c_str());
	if (size < 0)
		return 78;
	buffer.resize((u32)size);
	return size == 0 ? 0 : png_buffer_file(&buffer[0], (u32)size, filename.c_str());
}

/*write given buffer to the file, overwriting the file, it doesn't append to it.*/
u32 save_file(const std::vector<u8> &buffer, const std::string &filename)
{
	return png_save_file(buffer.empty() ? 0 : &buffer[0], buffer.size(), filename.c_str());
}
#endif /* PNG_COMPILE_DISK */

#ifdef PNG_COMPILE_ZLIB
#ifdef PNG_COMPILE_DECODER
u32 decompress(std::vector<u8> &out, const u8 *in, u32 insize,
	       const pngDecompressSettings &settings)
{
	u8 *buffer = 0;
	u32 buffersize = 0;
	u32 error = zlib_decompress(&buffer, &buffersize, 0, in, insize, &settings);
	if (buffer) {
		out.insert(out.end(), &buffer[0], &buffer[buffersize]);
		png_free(buffer);
	}
	return error;
}

u32 decompress(std::vector<u8> &out, const std::vector<u8> &in,
	       const pngDecompressSettings &settings)
{
	return decompress(out, in.empty() ? 0 : &in[0], in.size(), settings);
}
#endif /* PNG_COMPILE_DECODER */

#ifdef PNG_COMPILE_ENCODER
u32 compress(std::vector<u8> &out, const u8 *in, u32 insize, const pngCompressSettings &settings)
{
	u8 *buffer = 0;
	u32 buffersize = 0;
	u32 error = zlib_compress(&buffer, &buffersize, in, insize, &settings);
	if (buffer) {
		out.insert(out.end(), &buffer[0], &buffer[buffersize]);
		png_free(buffer);
	}
	return error;
}

u32 compress(std::vector<u8> &out, const std::vector<u8> &in, const pngCompressSettings &settings)
{
	return compress(out, in.empty() ? 0 : &in[0], in.size(), settings);
}
#endif /* PNG_COMPILE_ENCODER */
#endif /* PNG_COMPILE_ZLIB */

#ifdef PNG_COMPILE_PNG

State::State()
{
	png_state_init(this);
}

State::State(const State &other)
{
	png_state_init(this);
	png_state_copy(this, &other);
}

State::~State()
{
	png_state_cleanup(this);
}

State &State::operator=(const State &other)
{
	png_state_copy(this, &other);
	return *this;
}

#ifdef PNG_COMPILE_DECODER

u32 decode(std::vector<u8> &out, u32 &w, u32 &h, const u8 *in, u32 insize, pngColorType colortype,
	   u32 bitdepth)
{
	u8 *buffer = 0;
	u32 error = png_decode_memory(&buffer, &w, &h, in, insize, colortype, bitdepth);
	if (buffer && !error) {
		State state;
		state.info_raw.colortype = colortype;
		state.info_raw.bitdepth = bitdepth;
		u32 buffersize = png_get_raw_size(w, h, &state.info_raw);
		out.insert(out.end(), &buffer[0], &buffer[buffersize]);
	}
	png_free(buffer);
	return error;
}

u32 decode(std::vector<u8> &out, u32 &w, u32 &h, const std::vector<u8> &in, pngColorType colortype,
	   u32 bitdepth)
{
	return decode(out, w, h, in.empty() ? 0 : &in[0], (u32)in.size(), colortype, bitdepth);
}

u32 decode(std::vector<u8> &out, u32 &w, u32 &h, State &state, const u8 *in, u32 insize)
{
	u8 *buffer = NULL;
	u32 error = png_decode(&buffer, &w, &h, &state, in, insize);
	if (buffer && !error) {
		u32 buffersize = png_get_raw_size(w, h, &state.info_raw);
		out.insert(out.end(), &buffer[0], &buffer[buffersize]);
	}
	png_free(buffer);
	return error;
}

u32 decode(std::vector<u8> &out, u32 &w, u32 &h, State &state, const std::vector<u8> &in)
{
	return decode(out, w, h, state, in.empty() ? 0 : &in[0], in.size());
}

#ifdef PNG_COMPILE_DISK
u32 decode(std::vector<u8> &out, u32 &w, u32 &h, const std::string &filename,
	   pngColorType colortype, u32 bitdepth)
{
	std::vector<u8> buffer;
	/* safe output values in case error happens */
	w = h = 0;
	u32 error = load_file(buffer, filename);
	if (error)
		return error;
	return decode(out, w, h, buffer, colortype, bitdepth);
}
#endif /* PNG_COMPILE_DECODER */
#endif /* PNG_COMPILE_DISK */

#ifdef PNG_COMPILE_ENCODER
u32 encode(std::vector<u8> &out, const u8 *in, u32 w, u32 h, pngColorType colortype, u32 bitdepth)
{
	u8 *buffer;
	u32 buffersize;
	u32 error = png_encode_memory(&buffer, &buffersize, in, w, h, colortype, bitdepth);
	if (buffer) {
		out.insert(out.end(), &buffer[0], &buffer[buffersize]);
		png_free(buffer);
	}
	return error;
}

u32 encode(std::vector<u8> &out, const std::vector<u8> &in, u32 w, u32 h, pngColorType colortype,
	   u32 bitdepth)
{
	if (png_get_raw_size_lct(w, h, colortype, bitdepth) > in.size())
		return 84;
	return encode(out, in.empty() ? 0 : &in[0], w, h, colortype, bitdepth);
}

u32 encode(std::vector<u8> &out, const u8 *in, u32 w, u32 h, State &state)
{
	u8 *buffer;
	u32 buffersize;
	u32 error = png_encode(&buffer, &buffersize, in, w, h, &state);
	if (buffer) {
		out.insert(out.end(), &buffer[0], &buffer[buffersize]);
		png_free(buffer);
	}
	return error;
}

u32 encode(std::vector<u8> &out, const std::vector<u8> &in, u32 w, u32 h, State &state)
{
	if (png_get_raw_size(w, h, &state.info_raw) > in.size())
		return 84;
	return encode(out, in.empty() ? 0 : &in[0], w, h, state);
}

#ifdef PNG_COMPILE_DISK
u32 encode(const std::string &filename, const u8 *in, u32 w, u32 h, pngColorType colortype,
	   u32 bitdepth)
{
	std::vector<u8> buffer;
	u32 error = encode(buffer, in, w, h, colortype, bitdepth);
	if (!error)
		error = save_file(buffer, filename);
	return error;
}

u32 encode(const std::string &filename, const std::vector<u8> &in, u32 w, u32 h,
	   pngColorType colortype, u32 bitdepth)
{
	if (png_get_raw_size_lct(w, h, colortype, bitdepth) > in.size())
		return 84;
	return encode(filename, in.empty() ? 0 : &in[0], w, h, colortype, bitdepth);
}
#endif /* PNG_COMPILE_DISK */
#endif /* PNG_COMPILE_ENCODER */
#endif /* PNG_COMPILE_PNG */
} /* namespace png */
#endif /*PNG_COMPILE_CPP*/