public bool ReadFooter(InputBuffer input)
{
input.SkipToByteBoundary();
if (gzipFooterSubstate == GzipHeaderState.ReadingCRC)
{
while (loopCounter < 4)
{
int bits = input.GetBits(8);
if (bits < 0)
{
return(false);
}
expectedCrc32 |= ((uint)bits << (8 * loopCounter));
loopCounter++;
}
gzipFooterSubstate = GzipHeaderState.ReadingFileSize;
loopCounter = 0;
}
if (gzipFooterSubstate == GzipHeaderState.ReadingFileSize)
{
if (loopCounter == 0)
{
expectedOutputStreamSize = 0;
}
while (loopCounter < 4)
{
int bits = input.GetBits(8);
if (bits < 0)
{
return(false);
}
expectedOutputStreamSize |= ((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 end_of_block)
{
end_of_block = 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] + ((int)blockLengthBuffer[1]) * 256;
int blockLengthComplement = blockLengthBuffer[2] + ((int)blockLengthBuffer[3]) * 256;
// make sure complement matches
if ((ushort)blockLength != (ushort)(~blockLengthComplement))
{
throw new InvalidDataException("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;
end_of_block = true;
Debug.WriteLineIf(CompressionTracingSwitch.Informational, "End of Block", "Compression");
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("UnknownState");
}
}
}