blues/ja/unpack.c

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2018-12-16 13:34:03 +01:00
/* uncompress data packed with DIET by T.Matsumoto */
#include "unpack.h"
#include "util.h"
struct unpack_eat_t {
FILE *fp;
uint8_t len;
uint16_t bits;
uint8_t *dst;
};
static struct unpack_eat_t g_unpack;
static int next_bit(struct unpack_eat_t *u) {
const int bit = (u->bits & (1 << (16 - u->len))) != 0;
--u->len;
if (u->len == 0) {
u->bits = fread_le16(u->fp);
u->len = 16;
}
return bit;
}
static int zero_bits(struct unpack_eat_t *u, int count) {
int i = 0;
for (; i < count; ++i) {
if (next_bit(u)) {
break;
}
}
return i;
}
static uint8_t get_bits(struct unpack_eat_t *u, int count) {
assert(count < 8);
uint8_t val = 0;
for (int i = 0; i < count; ++i) {
val = (val << 1) | next_bit(u);
}
return val;
}
static void copy_reference(struct unpack_eat_t *u, int count, int offset_hi, int offset_lo) {
const int16_t offset = offset_hi * 256 + offset_lo;
for (int i = 0; i < count; ++i) {
const uint8_t value = u->dst[offset];
*u->dst++ = value;
}
}
static int unpack_eat(struct unpack_eat_t *u, uint8_t *output_buffer, int output_buffer_size) {
uint8_t buffer[17];
const int header_size = fread(buffer, 1, sizeof(buffer), u->fp);
if (header_size != 17 || READ_LE_UINT16(buffer + 4) != 0x899D || READ_LE_UINT16(buffer + 6) != 0x6C64) {
print_error("Unexpected signature for .eat file");
return 0;
}
const uint16_t crc = READ_LE_UINT16(buffer + 12);
const int output_size = (buffer[14] << 14) + READ_LE_UINT16(buffer + 15);
print_debug(DBG_UNPACK, "uncompressed size %d crc 0x%04x", output_size, crc);
if (output_size > output_buffer_size) {
print_error("Invalid output buffer size %d, need %d", output_buffer_size, output_size);
return 0;
}
u->dst = output_buffer;
u->len = 16;
u->bits = fread_le16(u->fp);
while (1) {
while (next_bit(u)) {
*u->dst++ = fgetc(u->fp);
}
const int b = next_bit(u);
const int offset_lo = fgetc(u->fp);
if (b) {
int offset_hi = 0xFE | next_bit(u);
if (!next_bit(u)) {
int i = 1;
for (; i < 4 && !next_bit(u); ++i) {
offset_hi = (offset_hi << 1) | next_bit(u);
}
offset_hi -= (1 << i);
}
const int n = zero_bits(u, 4);
if (n != 4) {
copy_reference(u, n + 3, offset_hi, offset_lo);
} else if (next_bit(u)) {
copy_reference(u, next_bit(u) + 7, offset_hi, offset_lo);
} else if (!next_bit(u)) {
copy_reference(u, get_bits(u, 3) + 9, offset_hi, offset_lo);
} else {
copy_reference(u, fgetc(u->fp) + 17, offset_hi, offset_lo);
}
} else {
if (next_bit(u)) {
const int offset_hi = (0xF8 | get_bits(u, 3)) - 1;
copy_reference(u, 2, offset_hi, offset_lo);
} else if (offset_lo == 0xFF) {
break;
} else {
copy_reference(u, 2, 0xFF, offset_lo);
}
}
}
assert((u->dst - output_buffer) == output_size);
return output_size;
}
int unpack(const char *filename, uint8_t *dst, int size) {
int uncompressed_size = 0;
FILE *fp = fopen(filename, "rb");
if (fp) {
memset(&g_unpack, 0, sizeof(struct unpack_eat_t));
g_unpack.fp = fp;
uncompressed_size = unpack_eat(&g_unpack, dst, size);
fclose(fp);
} else {
print_error("Unable to open '%s'", filename);
}
return uncompressed_size;
}