osdsys_decompress.c

#include <stdint.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>


uint32_t decompress_osdsys(uint8_t *src, uint8_t *dst)
{
  uint32_t run = 0;
  uint32_t length = *((uint32_t *)src);
  uint8_t *buffer = src + 4;
  uint32_t _DAT_002c9250;
  uint32_t _DAT_002c924c;
  uint32_t _DAT_002c9254;
  uint32_t _DAT_002c9258;
  
  uint8_t *dst_cur = dst;
  do {
    if (run == 0) {
      run = 0x1e;
      _DAT_002c9250 = (uint32_t)(uint8_t)(buffer[3] & 3);
      _DAT_002c924c = (buffer[0] << 24) | (buffer[1] << 16) | (buffer[2] << 8) | (buffer[3]);
      _DAT_002c9254 = 0xe - _DAT_002c9250;
      _DAT_002c9258 = 0x3fff >> _DAT_002c9250;
      buffer += 4;
    }
    uint8_t uVar1 = *buffer;
    uint8_t *puVar4 = buffer + 1;
    if ((_DAT_002c924c & 0x80000000) == 0) {
      buffer = puVar4;
      *dst_cur = uVar1;
      dst_cur += 1;
    }
    else {
      buffer += 2;
      uint16_t uVar2 = (uVar1 << 8) | (*puVar4);
      puVar4 = dst_cur - ((uVar2 & _DAT_002c9258) + 1);
      uint32_t iVar3 = (uint32_t)(uVar2 >> (_DAT_002c9254 & 0x1f)) + 2;
      *dst_cur = *puVar4;
      uint8_t *puVar6 = dst_cur + 1;
      if (iVar3 == 0) {
        dst_cur += 1;
      }
      else {
        do {
          puVar4 += 1;
          iVar3 -= 1;
          *puVar6 = *puVar4;
          puVar6 += 1;
          dst_cur = puVar6;
        } while (iVar3 != 0);
      }
    }
    if ((dst_cur - dst == length) ||
       (run -= 1, length < dst_cur - dst)) {
      return length;
    }
    _DAT_002c924c <<= 1;
  } while( true );
  return length;
}

int main(int argc, char** argv)
{
  if (argc != 3)
    return 1;
  FILE* infile = fopen(argv[1], "rb");
  if (!infile)
    return 2;
  fseek(infile, 0, SEEK_END);
  uint32_t cmp_sz = ftell(infile);
  fseek(infile, 0, SEEK_SET);
  uint32_t unc_sz = 0;
  size_t read_header_sz = fread(&unc_sz, 1, 4, infile);
  if (read_header_sz != 4)
    return 3;
  fseek(infile, 0, SEEK_SET);
  uint8_t *cmp_dat = malloc(cmp_sz);
  if (!cmp_dat)
    return 4;
  uint8_t *unc_dat = malloc(unc_sz);
  if (!unc_dat)
    return 5;
  size_t read_cmp_sz = fread(cmp_dat, 1, cmp_sz, infile);
  if (read_cmp_sz != cmp_sz)
    return 6;
  fclose(infile);
  uint32_t uncmp_sz = decompress_osdsys(cmp_dat, unc_dat);
  free(cmp_dat);
  FILE* outfile = fopen(argv[2], "wb");
  if (!outfile)
    return 7;
  fwrite(unc_dat, 1, uncmp_sz, outfile);
  fclose(outfile);
  return 0;
}