void dwgCompressor::decrypt18Hdr(duint8 *buf, duint64 size, duint64 offset){
    duint8 max = size / 4;
    duint32 secMask = 0x4164536b ^ offset;
    duint32* pHdr = reinterpret_cast<duint32*>(buf);
    for (duint8 j = 0; j < max; j++)
        *pHdr++ ^= secMask;
}
void dwgCompressor::decrypt18Hdr(duint8 *buf, duint64 size, duint64 offset){
    duint8 max = size / 4;
    duint32 secMask = 0x4164536b ^ offset;
    duint32* pHdr = reinterpret_cast<duint32*>(buf);
    for (duint8 j = 0; j < max; j++)
        *pHdr++ ^= secMask;
}