// Calculate the huffman code for each character based on the code length for each character.
// This algorithm is described in standard RFC 1951
private uint[] CalculateHuffmanCode()
{
uint[] bitLengthCount = new uint[17];
foreach (int codeLength in _codeLengthArray)
{
bitLengthCount[codeLength]++;
}
bitLengthCount[0] = 0; // clear count for length 0
uint[] nextCode = new uint[17];
uint tempCode = 0;
for (int bits = 1; bits <= 16; bits++)
{
tempCode = (tempCode + bitLengthCount[bits - 1]) << 1;
nextCode[bits] = tempCode;
}
uint[] code = new uint[MaxLiteralTreeElements];
for (int i = 0; i < _codeLengthArray.Length; i++)
{
int len = _codeLengthArray[i];
if (len > 0)
{
code[i] = DecodeHelper.BitReverse(nextCode[len], len);
nextCode[len]++;
}
}
return(code);
}
public int Inflate(byte[] bytes, int offset, int length)
{
// copy bytes from output to outputbytes if we have aviable bytes
// if buffer is not filled up. keep decoding until no input are available
// if decodeBlock returns false. Throw an exception.
int count = 0;
do
{
int copied = _output.CopyTo(bytes, offset, length);
if (copied > 0)
{
if (_usingGzip)
{
_crc32 = DecodeHelper.UpdateCrc32(_crc32, bytes, offset, copied);
uint n = _streamSize + (uint) copied;
if (n < _streamSize)
{
// overflow, the gzip stream is probably malicious.
throw new InvalidDataException("SR.StreamSizeOverflow");
}
_streamSize = n;
}
offset += copied;
count += copied;
length -= copied;
}
if (length == 0)
{
// filled in the bytes array
break;
}
// Decode will return false when more input is needed
} while (!Finished() && Decode());
if (_state == InflaterState.VerifyingGZIPFooter)
{
// finished reading CRC
// In this case finished is true and output window has all the data.
// But some data in output window might not be copied out.
if (_output.AvailableBytes == 0)
{
if (_crc32 != _gZipDecoder.Crc32)
{
throw new InvalidDataException("SR.InvalidCRC");
}
if (_streamSize != _gZipDecoder.StreamSize)
{
throw new InvalidDataException("SR.InvalidStreamSize");
}
}
}
return count;
}
//
// Copy the compressed byte to outputBuffer
// Returns the bytes we have copied. The caller needs to provide the buffer
// to avoid extra coping.
//
public int GetCompressedOutput(byte[] outputBuffer)
{
Debug.Assert(!NeedsInput(), "call SetInput before trying to compress!");
_output.UpdateBuffer(outputBuffer);
if (_usingGzip && !_hasGzipHeader)
{
// Write the GZIP header only once
_output.WriteGzipHeader(3);
_hasGzipHeader = true;
}
if (!_hasBlockHeader)
{
// Output dynamic block header only once
_hasBlockHeader = true;
_output.WritePreamble();
}
do
{
// read more input data into the window if there is space available
int bytesToCopy = (_inputBuffer.Count < _inputWindow.FreeWindowSpace) ?
_inputBuffer.Count : _inputWindow.FreeWindowSpace;
if (bytesToCopy > 0)
{
// copy data into history window
_inputWindow.CopyBytes(_inputBuffer.Buffer, _inputBuffer.StartIndex, bytesToCopy);
if (_usingGzip)
{
// update CRC for gzip stream
_gzipCrc32 = DecodeHelper.UpdateCrc32(_gzipCrc32, _inputBuffer.Buffer, _inputBuffer.StartIndex, bytesToCopy);
uint n = _inputStreamSize + (uint)bytesToCopy;
if (n < _inputStreamSize)
{ // overflow, gzip doesn't support compressing more than Int32.Maxvalue bytes.
throw new InvalidDataException("SR.StreamSizeOverflow");
}
_inputStreamSize = n;
}
_inputBuffer.ConsumeBytes(bytesToCopy);
}
// compress the bytes in input history window
while (_inputWindow.BytesAvailable > 0 && _output.SafeToWriteTo())
{
// Find next match. A match can be a symbol,
// a distance/length pair, a symbol followed by a distance/Length pair
_inputWindow.GetNextSymbolOrMatch(_currentMatch);
if (_currentMatch.State == MatchState.HasSymbol)
{
_output.WriteChar(_currentMatch.Symbol);
}
else if (_currentMatch.State == MatchState.HasMatch)
{
_output.WriteMatch(_currentMatch.Length, _currentMatch.Position);
}
else
{
_output.WriteChar(_currentMatch.Symbol);
_output.WriteMatch(_currentMatch.Length, _currentMatch.Position);
}
}
} while (_output.SafeToWriteTo() && !NeedsInput());
// update book keeping needed to write end of block data
_needsEob = true;
return(_output.BytesWritten); // number of bytes we have written
}
