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// Copyright (c) 2024, Marvin Borner <dev@marvinborner.de>
// SPDX-License-Identifier: MIT
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <term.h>
#include <spec.h>
#include <parse.h>
#include <log.h>
#define BIT_AT(i) ((term[(i) / 8] & (1 << (7 - ((i) % 8)))) >> (7 - ((i) % 8)))
// parses bloc's bit-encoded blc
// 010M -> abstraction of M
// 00MN -> application of M and N
// 1X0 -> bruijn index, amount of 1s in X
// 011I -> 2B index to entry
static struct term *parse_bloc_bblc(const char *term, size_t *bit)
{
struct term *res = 0;
if (!BIT_AT(*bit) && BIT_AT(*bit + 1) && !BIT_AT(*bit + 2)) {
(*bit) += 3;
res = new_term(ABS);
res->u.abs.term = parse_bloc_bblc(term, bit);
} else if (!BIT_AT(*bit) && !BIT_AT(*bit + 1)) {
(*bit) += 2;
res = new_term(APP);
res->u.app.lhs = parse_bloc_bblc(term, bit);
res->u.app.rhs = parse_bloc_bblc(term, bit);
} else if (BIT_AT(*bit)) {
const size_t cur = *bit;
while (BIT_AT(*bit))
(*bit)++;
res = new_term(VAR);
res->u.var.index = *bit - cur - 1;
(*bit)++;
} else if (!BIT_AT(*bit) && BIT_AT(*bit + 1) && BIT_AT(*bit + 2)) {
(*bit) += 3;
// selected bit pattern, see readme
int sel = (2 << (BIT_AT(*bit) * 2 + BIT_AT(*bit + 1) + 2));
(*bit) += 2;
res = new_term(REF);
size_t index = 0;
for (int i = 0; i < sel; i++) {
index |= BIT_AT(*bit) << i;
(*bit) += 1;
}
res->u.ref.index = index;
} else {
(*bit)++;
res = parse_bloc_bblc(term, bit);
}
return res;
}
struct bloc_parsed *parse_bloc(const void *bloc)
{
const struct bloc_header *header = bloc;
if (memcmp(header->identifier, BLOC_IDENTIFIER,
(size_t)BLOC_IDENTIFIER_LENGTH)) {
fatal("invalid BLoC identifier!\n");
return 0;
}
struct bloc_parsed *parsed = malloc(sizeof(*parsed));
parsed->length = header->length;
parsed->entries = malloc(header->length * sizeof(struct term *));
const struct bloc_entry *current = (const void *)&header->entries;
for (size_t i = 0; i < parsed->length; i++) {
size_t len = 0;
parsed->entries[i] =
parse_bloc_bblc((const char *)current, &len);
current =
(const struct bloc_entry *)(((const char *)current) +
(len / 8) + (len % 8 != 0));
}
return parsed;
}
void free_bloc(struct bloc_parsed *bloc)
{
for (size_t i = 0; i < bloc->length; i++) {
free_term(bloc->entries[i]);
}
free(bloc->entries);
free(bloc);
}
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