public bool ReadGzipFooter()
{
input.SkipToByteBoundary();
if (gzipFooterSubstate == GZIPHeaderState.ReadingCRC)
{
while (loopCounter < 4)
{
int bits = input.GetBits(8);
if (bits < 0)
{
return(false);
}
gzipCrc32 |= ((uint)bits << (8 * loopCounter));
loopCounter++;
}
gzipFooterSubstate = GZIPHeaderState.ReadingFileSize;
loopCounter = 0;
}
if (gzipFooterSubstate == GZIPHeaderState.ReadingFileSize)
{
if (loopCounter == 0)
{
gzipOutputStreamSize = 0;
}
while (loopCounter < 4)
{
int bits = input.GetBits(8);
if (bits < 0)
{
return(false);
}
gzipOutputStreamSize |= ((uint)bits << (8 * loopCounter));
loopCounter++;
}
}
return(true);
}
// Format of Non-compressed blocks (BTYPE=00):
//
// Any bits of input up to the next byte boundary are ignored.
// The rest of the block consists of the following information:
//
// 0 1 2 3 4...
// +---+---+---+---+================================+
// | LEN | NLEN |... LEN bytes of literal data...|
// +---+---+---+---+================================+
//
// LEN is the number of data bytes in the block. NLEN is the
// one's complement of LEN.
private bool DecodeUncompressedBlock(out bool endOfBlock)
{
endOfBlock = false;
while (true)
{
switch (_state)
{
case InflaterState.UncompressedAligning: // intial state when calling this function
// we must skip to a byte boundary
_input.SkipToByteBoundary();
_state = InflaterState.UncompressedByte1;
goto case InflaterState.UncompressedByte1;
case InflaterState.UncompressedByte1: // decoding block length
case InflaterState.UncompressedByte2:
case InflaterState.UncompressedByte3:
case InflaterState.UncompressedByte4:
int bits = _input.GetBits(8);
if (bits < 0)
{
return false;
}
_blockLengthBuffer[_state - InflaterState.UncompressedByte1] = (byte) bits;
if (_state == InflaterState.UncompressedByte4)
{
_blockLength = _blockLengthBuffer[0] + (_blockLengthBuffer[1])*256;
int blockLengthComplement = _blockLengthBuffer[2] + (_blockLengthBuffer[3])*256;
// make sure complement matches
if ((ushort) _blockLength != (ushort) (~blockLengthComplement))
{
throw new InvalidDataException("SR.InvalidBlockLength");
}
}
_state += 1;
break;
case InflaterState.DecodingUncompressed: // copying block data
// Directly copy bytes from input to output.
int bytesCopied = _output.CopyFrom(_input, _blockLength);
_blockLength -= bytesCopied;
if (_blockLength == 0)
{
// Done with this block, need to re-init bit buffer for next block
_state = InflaterState.ReadingBFinal;
endOfBlock = true;
return true;
}
// We can fail to copy all bytes for two reasons:
// Running out of Input
// running out of free space in output window
if (_output.FreeBytes == 0)
{
return true;
}
return false;
default:
Debug.Assert(false, "check why we are here!");
throw new InvalidDataException("SR.UnknownState");
}
}
}