50 lines
1.1 KiB
C
50 lines
1.1 KiB
C
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#include "unpack.h"
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#include "util.h"
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struct unpack_t {
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uint8_t dict_buf[0x200 * 2];
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};
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static struct unpack_t g_unpack;
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int unpack(FILE *in, uint8_t *dst) {
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uint8_t buf[6];
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fread(buf, 1, 6, in);
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const int uncompressed_size = (READ_LE_UINT16(buf) << 16) + READ_LE_UINT16(buf + 2);
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const int dict_len = READ_LE_UINT16(buf + 4);
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print_debug(DBG_UNPACK, "SQV uncompressed size %d dict_len %d", uncompressed_size, dict_len);
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fread(g_unpack.dict_buf, 1, dict_len, in);
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const uint8_t *start = dst;
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int bits_count = 1;
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uint16_t bits = 0;
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uint16_t val = 0;
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while ((dst - start) < uncompressed_size) {
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--bits_count;
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if (bits_count == 0) {
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if (fread(buf, 1, 2, in) == 0) {
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break;
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}
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bits = READ_BE_UINT16(buf);
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bits_count = 16;
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}
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const bool carry = (bits & 0x8000) != 0;
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bits <<= 1;
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if (carry) {
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val += 2;
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}
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assert((val & 1) == 0);
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assert(val < dict_len);
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val = READ_LE_UINT16(g_unpack.dict_buf + val);
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if ((val & 0x8000) == 0) {
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continue;
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}
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assert((val & 0x7F00) == 0);
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*dst++ = val & 255;
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val = 0;
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}
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assert((dst - start) == uncompressed_size);
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return uncompressed_size;
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}
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