Function GetBits

3rdParty/StormLib/src/SBaseFileTable.cpp:83–147

}

void GetBits(
    TBitArray * pArray,
    unsigned int nBitPosition,
    unsigned int nBitLength,
    void * pvBuffer,
    int nResultByteSize)
{
    unsigned char * pbBuffer = (unsigned char *)pvBuffer;
    unsigned int nBytePosition0 = (nBitPosition / 8);
    unsigned int nBytePosition1 = nBytePosition0 + 1;
    unsigned int nByteLength = (nBitLength / 8);
    unsigned int nBitOffset = (nBitPosition & 0x07);
    unsigned char BitBuffer;

    // Keep compiler happy for platforms where nResultByteSize is not used
    nResultByteSize = nResultByteSize;

#ifdef _DEBUG
    // Check if the target is properly zeroed
    for(int i = 0; i < nResultByteSize; i++)
        assert(pbBuffer[i] == 0);
#endif

#ifndef PLATFORM_LITTLE_ENDIAN
    // Adjust the buffer pointer for big endian platforms
    pbBuffer += (nResultByteSize - 1);
#endif

    // Copy whole bytes, if any
    while(nByteLength > 0)
    {
        // Is the current position in the Elements byte-aligned?
        if(nBitOffset != 0)
        {
            BitBuffer = (unsigned char)((pArray->Elements[nBytePosition0] >> nBitOffset) | (pArray->Elements[nBytePosition1] << (0x08 - nBitOffset)));
        }
        else
        {
            BitBuffer = pArray->Elements[nBytePosition0];
        }

#ifdef PLATFORM_LITTLE_ENDIAN
        *pbBuffer++ = BitBuffer;
#else
        *pbBuffer-- = BitBuffer;
#endif

        // Move byte positions and lengths
        nBytePosition1++;
        nBytePosition0++;
        nByteLength--;
    }

    // Get the rest of the bits
    nBitLength = (nBitLength & 0x07);
    if(nBitLength != 0)
    {
        *pbBuffer = (unsigned char)(pArray->Elements[nBytePosition0] >> nBitOffset);