Decompiled Tetris Decompress method

Decompress.cpp

#define g_p_BOLTcursor (*(byte **)(unaff_A5 + -0x15f0))
#define g_BOLT_bytes_available (*(int *)(unaff_A5 + -0x15f8))

#define NEXT_BYTE(r) nBytesAvailable--;\
                    if (nBytesAvailable < 0) { NextBlock(); pData = g_p_BOLTcursor; nBytesAvailable = g_BOLT_bytes_available; }\
                    r = *pData++;

byte * Decompress(byte *pResult, uint result_filesize, ushort flags)
{
  ushort uVar2;
  uint uVar1;
  int nBytesAvailable;
  byte bVar4;
  uint uVar5;
  uint uVar6;
  ushort uVar7;
  byte *pData;
  byte *pbVar9;
  byte *pbVar10;
  byte *pOutputPtr;
  int unaff_A5;
  byte next_byte;
  
  if (!pResult) {
    pResult = (byte *)SysBOLTAlloc(result_filesize);
    if (!pResult) return NULL;
  }

  pData = g_p_BOLTcursor;
  nBytesAvailable = g_BOLT_bytes_available;
  pOutputPtr = pResult;
  if ((flags & 8) == 0) { // compressed
    while ((int)result_filesize >= 1) {
      NEXT_BYTE(bytevalue);

      switch((bytevalue & 0xf0) >> 4) {
      case 0x0:
      case 0x1:
        uVar5 = (uint)(bytevalue & 0x1f);
        result_filesize -= uVar5 + 1;
        if ((int)uVar5 < nBytesAvailable) {
          nBytesAvailable -= uVar5 + 1;
          do {
            *pOutputPtr++ = *pData++;
            uVar5--;
          } while (uVar5 != -1);
        }
        else {
          do {
            NEXT_BYTE(*pOutputPtr);
            pOutputPtr++;
            uVar5--;
          } while (uVar5 != -1);
        }
        continue;
      case 0x2:
        uVar7 = bytevalue & 0xf;
        bVar4 = 0;
        goto LAB_00009076;
      case 0x3:
        NEXT_BYTE(bVar4);
        uVar7 = (bytevalue & 0xf) + 2;
  LAB_00009076:
        result_filesize -= uVar7 + 1;
        do {
          *pOutputPtr++ = bVar4;
          uVar7--;
        } while (uVar7 != -1);
        continue;
      case 0x4:
      case 0x5:
      case 0x6:
      case 0x7:
        uVar6 = (uint)(ushort)((bytevalue & 7) + 1);
        pbVar10 = pOutputPtr - (int)(short)((bytevalue >> 3 & 7) + 1);
        break;
      case 0x8:
        NEXT_BYTE(next_byte);
        uVar6 = (uint)(ushort)((next_byte & 0x3f) + 2);
        pbVar10 = pOutputPtr - (int)(short)((CONCAT11(bytevalue,next_byte) >> 6 & 0x3f) + 1);
        break;
      case 0x9:
        NEXT_BYTE(next_byte);
        uVar6 = (uint)(ushort)((next_byte & 3) + 2);
        pbVar10 = pOutputPtr - (int)(short)((CONCAT11(bytevalue,next_byte) >> 2 & 0x3ff) + 1);
        break;
      case 0xA:
        NEXT_BYTE(next_byte);
        uVar2 = (ushort)next_byte << 8;
        NEXT_BYTE(next_byte);
        uVar6 = (uint)(ushort)((uVar2 & 0xff00 | (ushort)next_byte) - 1);
        pbVar10 = pOutputPtr - (int)(short)((bytevalue & 0xf) + 1);
        break;
      case 0xB:
        NEXT_BYTE(next_byte);
        uVar1 = (uint)next_byte << 8;
        NEXT_BYTE(next_byte);
        uVar6 = (uint)(ushort)(((ushort)uVar1 & 0x300 | (ushort)next_byte) + 3);
        pbVar10 = pOutputPtr - (int)(short)(((ushort)((uVar1 & 0xff00 | bytevalue << 0x10) >> 10) & 0x3ff) + 1);
        break;
      case 0xC:
      case 0xD:
        uVar6 = (uint)(ushort)((bytevalue & 3) + 1);
        pbVar10 = pOutputPtr - (int)(short)(bytevalue >> 2 & 7);
        goto LAB_000091d4;
      case 0xE:
        NEXT_BYTE(next_byte);
        uVar6 = (uint)(ushort)((next_byte & 0x3f) + 2);
        pbVar10 = pOutputPtr - (int)(short)(CONCAT11(bytevalue,next_byte) >> 6 & 0x3f );
        goto LAB_000091d4;
      case 0xF:
        NEXT_BYTE(next_byte);
        uVar1 = (uint)next_byte << 8;
        NEXT_BYTE(next_byte);
        uVar6 = (uint)(ushort)(((ushort)uVar1 & 0x300 | (ushort)next_byte) + 3) ;
        pbVar10 = pOutputPtr - (int)(short)((ushort)((uVar1 & 0xff00 | bytevalue << 0x10) >> 10) & 0x3ff);
  LAB_000091d4:
        result_filesize -= uVar6 + 1;
        do {
          pbVar10--;
          *pOutputPtr++ = *pbVar10;
          uVar6--;
        } while (uVar6 != -1);
        continue;
      }
      result_filesize -= uVar6 + 1;
      do {
        *pOutputPtr++ = *pbVar10++;
        uVar6--;
      } while (uVar6 != -1);
    }
  }
  else {
    // uncompressed
    while ((uVar7 = (short)result_filesize - 1,
            result_filesize = result_filesize & 0xffff0000 | (uint)uVar7, uVar7 != 0xffff ||
            (result_filesize = result_filesize - 0x10000, -1 < (int)result_filesize))) {
      NEXT_BYTE(next_byte);
      *pOutputPtr = next_byte;
      pOutputPtr++;
    }
  }

  g_BOLT_bytes_available = nBytesAvailable;
  g_p_BOLTcursor = pData;
  return pResult;
}