1 files changed, 121 insertions, 0 deletions
diff --git a/libs/libc/mem.c b/libs/libc/mem.c
new file mode 100644
index 0000000..95242e4
--- /dev/null
+++ b/libs/libc/mem.c
@@ -0,0 +1,121 @@
+// MIT License, Copyright (c) 2020 Marvin Borner
+
+#include <assert.h>
+#include <def.h>
+#include <mem.h>
+#include <sys.h>
+
+void *memcpy(void *dest, const void *src, u32 n)
+{
+#ifdef userspace
+	// Inspired by Jeko at osdev
+	u8 *dest_byte = dest;
+	const u8 *src_byte = src;
+	for (u32 i = 0; i < n / 16; i++) {
+		__asm__ volatile("movups (%0), %%xmm0\n"
+				 "movntdq %%xmm0, (%1)\n" ::"r"(src_byte),
+				 "r"(dest_byte)
+				 : "memory");
+
+		src_byte += 16;
+		dest_byte += 16;
+	}
+
+	if (n & 7) {
+		n = n & 7;
+
+		int d0, d1, d2;
+		__asm__ volatile("rep ; movsl\n\t"
+				 "testb $2,%b4\n\t"
+				 "je 1f\n\t"
+				 "movsw\n"
+				 "1:\ttestb $1,%b4\n\t"
+				 "je 2f\n\t"
+				 "movsb\n"
+				 "2:"
+				 : "=&c"(d0), "=&D"(d1), "=&S"(d2)
+				 : "0"(n / 4), "q"(n), "1"((long)dest_byte), "2"((long)src_byte)
+				 : "memory");
+	}
+	return dest_byte;
+#else
+	// Inspired by jgraef at osdev
+	u32 num_dwords = n / 4;
+	u32 num_bytes = n % 4;
+	u32 *dest32 = (u32 *)dest;
+	const u32 *src32 = (const u32 *)src;
+	u8 *dest8 = ((u8 *)dest) + num_dwords * 4;
+	const u8 *src8 = ((const u8 *)src) + num_dwords * 4;
+
+	// TODO: What's faster?
+	__asm__ volatile("rep movsl\n"
+			 : "=S"(src32), "=D"(dest32), "=c"(num_dwords)
+			 : "S"(src32), "D"(dest32), "c"(num_dwords)
+			 : "memory");
+
+	/* for (u32 i = 0; i < num_dwords; i++) { */
+	/* 	dest32[i] = src32[i]; */
+	/* } */
+
+	for (u32 i = 0; i < num_bytes; i++) {
+		dest8[i] = src8[i];
+	}
+	return dest;
+#endif
+}
+
+void *memset(void *dest, int val, u32 n)
+{
+	u32 uval = val;
+	u32 num_dwords = n / 4;
+	u32 num_bytes = n % 4;
+	u32 *dest32 = (u32 *)dest;
+	u8 *dest8 = ((u8 *)dest) + num_dwords * 4;
+	u8 val8 = (u8)val;
+	u32 val32 = uval | (uval << 8) | (uval << 16) | (uval << 24);
+
+	// TODO: What's faster?
+	__asm__ volatile("rep stosl\n"
+			 : "=D"(dest32), "=c"(num_dwords)
+			 : "D"(dest32), "c"(num_dwords), "a"(val32)
+			 : "memory");
+
+	/* for (u32 i = 0; i < num_dwords; i++) { */
+	/* 	dest32[i] = val32; */
+	/* } */
+
+	for (u32 i = 0; i < num_bytes; i++) {
+		dest8[i] = val8;
+	}
+	return dest;
+}
+
+void *memchr(void *src, int c, u32 n)
+{
+	u8 *s = (u8 *)src;
+
+	while (n-- > 0) {
+		if (*s == c)
+			return s;
+		s++;
+	}
+	return NULL;
+}
+
+int memcmp(const void *s1, const void *s2, u32 n)
+{
+	const u8 *a = (const u8 *)s1;
+	const u8 *b = (const u8 *)s2;
+	for (u32 i = 0; i < n; i++) {
+		if (a[i] < b[i])
+			return -1;
+		else if (b[i] < a[i])
+			return 1;
+	}
+	return 0;
+}
+
+int mememp(const u8 *buf, u32 n)
+{
+	return buf[0] == 0 && !memcmp(buf, buf + 1, n - 1);
+}