Dim ROMData() As Byte 'Dynamic array for storing ROM data
Dim ROMSize As Double 'For the file's full size
Dim FileNum As Long 'File number... a BASIC thing.

'Get an unused file number, then open the file
FileNum = FreeFile
Open "ROM.rom" For Binary Access Read As FileNum
    ROMSize = LoF(FileNum) 'Get the file's size
    ReDim ROMData(0 To ROMSize - 1) As Byte 'Allocate memory
    Get FileNum, 1, ROMData 'Load the data from file
Close FileNum

// Decodes a data stream to B.O.B.'s specifications
unsigned int lzDec(unsigned int DecLen,
                   unsigned char *Src, unsigned char *Dst) {
    unsigned int sOff = 0, dOff = 0, Temp, Dist;
    unsigned char cHdr, Bit, BitVal, Leng;

    // Keep going 'til it's all decoded
    while (dOff < DecLen) {
      // Chunk header
      cHdr = Src[sOff]; sOff++;

      // Cycle through bits
      for (Bit = 0; Bit < 8; Bit++) {
        BitVal = (cHdr >> (7 - Bit)) & 1;

        // Literal
        if (BitVal == 0) {
          Dst[dOff] = Src[sOff];
          sOff++; dOff++;

        // Distance/length pair
        } else { 
          Temp = Src[sOff] | (Src[sOff + 1] << 8);
          Dist = Temp & 0x7FF;
          Leng = (Temp >> 11) + 3;
          sOff += 2;

          // Prevent out of bounds for bad data
          if (Dist > dOff || Dist == 0) return 0;

          // Copy Length bytes from output buffer
          for (Temp = 0; Temp < Leng; Temp++) {
            Dst[dOff] = Dst[dOff - Dist];
            dOff++; if (dOff == DecLen) break;
          } // for
        } // if
        if (dOff == DecLen) break;
      } // for

    } // while

    // Return size of packed data
    return sOff;
}

// Encodes a data stream to B.O.B.'s specifications
unsigned int lzEnc(unsigned int DecLen, 
                   unsigned char *Src, unsigned char *Dst) {
    unsigned int sOff = 1, dOff = 2, HdrOff = 0, Temp;
    unsigned char cHdr = 0, Bit = 1, tLen;
    unsigned int mDist, MaxLeng, mOff, LongLeng, LongDist;

    // Write the first byte as literal
    Dst[1] = Src[0];

    // Encode until done
    while (sOff < DecLen) {
      // Calculate starting distance
      if (sOff < 0x7FF) mDist = sOff;
      else mDist = 0x7FF;

      // Find the longest match
      LongLeng = 0;
      for (mOff = sOff - mDist; mOff < sOff; mOff++) {
        // Match was found; find its length
        if (Src[mOff] == Src[sOff]) {
          // Calculate maximum possible length
          MaxLeng = DecLen - mOff;
          if (MaxLeng > 0x22) MaxLeng = 0x22;

          // Scan bytes and check reported length
          for (tLen = 1; tLen <= MaxLeng; tLen++)
            if (Src[mOff + tLen] != Src[sOff + tLen]) break;
          if (tLen > MaxLeng) tLen = MaxLeng; // For loop quirk

          // If this is the longest match so-far, record it
          if (tLen >= LongLeng) {
            LongLeng = tLen;
            LongDist = sOff - mOff;
          } // if
        } // if
      } // for

      // Literal byte
      if (LongLeng < 3) {
        Dst[dOff] = Src[sOff];
        dOff++; sOff++;

      // Distance/length pair
      } else {
        Temp = LongDist | ((LongLeng - 3) << 11);
        Dst[dOff] = Temp & 0xFF;
        Dst[dOff + 1] = (Temp >> 8);
        cHdr |= (0x80 >> Bit);
        dOff += 2; sOff += LongLeng;
      }

      // Write out a chunk header if needed
      Bit++;
      if (Bit == 8) {
        Dst[HdrOff] = cHdr;
        cHdr = 0; Bit = 0;
        HdrOff = dOff; dOff++;
      }

    } // while

    // Write the last chunk header if needed and return output size
    if (Bit > 0) Dst[HdrOff] = cHdr;
    return dOff;
}