// Copy the compressed bytes to output buffer as a block. maxBytesToCopy limits the number of
// bytes we can copy from input. Set to any value < 1 if no limit
internal void GetBlock(DeflateInput input, OutputBuffer output, int maxBytesToCopy)
{
Debug.Assert(InputAvailable(input), "call SetInput before trying to compress!");
WriteDeflatePreamble(output);
GetCompressedOutput(input, output, maxBytesToCopy);
WriteEndOfBlock(output);
}
private void WriteEndOfBlock(OutputBuffer output)
{
// The fast encoder outputs one long block, so it just needs to terminate this block
const int EndOfBlockCode = 256;
uint code_info = FastEncoderStatics.FastEncoderLiteralCodeInfo[EndOfBlockCode];
int code_len = (int)(code_info & 31);
output.WriteBits(code_len, code_info >> 5);
}
internal DeflaterManaged()
{
deflateEncoder = new FastEncoder();
copyEncoder = new CopyEncoder();
input = new DeflateInput();
output = new OutputBuffer();
processingState = DeflaterState.NotStarted;
}
private void WriteLenNLen(ushort len, OutputBuffer output)
{
// len
output.WriteUInt16(len);
// nlen
ushort onesComp = (ushort)(~(ushort)len);
output.WriteUInt16(onesComp);
}
// null input means write an empty payload with formatting info. This is needed for the final block.
public void GetBlock(DeflateInput input, OutputBuffer output, bool isFinal)
{
Debug.Assert(output != null);
Debug.Assert(output.FreeBytes >= PaddingSize);
// determine number of bytes to write
int count = 0;
if (input != null)
{
// allow space for padding and bits not yet flushed to buffer
count = Math.Min(input.Count, output.FreeBytes - PaddingSize - output.BitsInBuffer);
// we don't expect the output buffer to ever be this big (currently 4K), but we'll check this
// just in case that changes.
if (count > MaxUncompressedBlockSize - PaddingSize)
{
count = MaxUncompressedBlockSize - PaddingSize;
}
}
// write header and flush bits
if (isFinal)
{
output.WriteBits(FastEncoderStatics.BFinalNoCompressionHeaderBitCount,
FastEncoderStatics.BFinalNoCompressionHeader);
}
else
{
output.WriteBits(FastEncoderStatics.NoCompressionHeaderBitCount,
FastEncoderStatics.NoCompressionHeader);
}
// now we're aligned
output.FlushBits();
// write len, nlen
WriteLenNLen((ushort)count, output);
// write uncompressed bytes
if (input != null && count > 0)
{
output.WriteBytes(input.Buffer, input.StartIndex, count);
input.ConsumeBytes(count);
}
}
// maxBytesToCopy limits the number of bytes we can copy from input. Set to any value < 1 if no limit
private void GetCompressedOutput(DeflateInput input, OutputBuffer output, int maxBytesToCopy)
{
// snapshot for compression ratio stats
int bytesWrittenPre = output.BytesWritten;
int bytesConsumedFromInput = 0;
int inputBytesPre = BytesInHistory + input.Count;
do
{
// read more input data into the window if there is space available
int bytesToCopy = (input.Count < inputWindow.FreeWindowSpace) ?
input.Count : inputWindow.FreeWindowSpace;
if (maxBytesToCopy >= 1)
{
bytesToCopy = Math.Min(bytesToCopy, maxBytesToCopy - bytesConsumedFromInput);
}
if (bytesToCopy > 0)
{
// copy data into history window
inputWindow.CopyBytes(input.Buffer, input.StartIndex, bytesToCopy);
input.ConsumeBytes(bytesToCopy);
bytesConsumedFromInput += bytesToCopy;
}
GetCompressedOutput(output);
} while (SafeToWriteTo(output) && InputAvailable(input) && (maxBytesToCopy < 1 || bytesConsumedFromInput < maxBytesToCopy));
// determine compression ratio, save
int bytesWrittenPost = output.BytesWritten;
int bytesWritten = bytesWrittenPost - bytesWrittenPre;
int inputBytesPost = BytesInHistory + input.Count;
int totalBytesConsumed = inputBytesPre - inputBytesPost;
if (bytesWritten != 0)
{
lastCompressionRatio = (double)bytesWritten / (double)totalBytesConsumed;
}
}
// compress the bytes in input history window
private void GetCompressedOutput(OutputBuffer output)
{
while (inputWindow.BytesAvailable > 0 && SafeToWriteTo(output))
{
// 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)
{
WriteChar(currentMatch.Symbol, output);
}
else if (currentMatch.State == MatchState.HasMatch)
{
WriteMatch(currentMatch.Length, currentMatch.Position, output);
}
else
{
WriteChar(currentMatch.Symbol, output);
WriteMatch(currentMatch.Length, currentMatch.Position, output);
}
}
}
internal void GetBlockFooter(OutputBuffer output)
{
WriteEndOfBlock(output);
}
internal void GetBlockHeader(OutputBuffer output)
{
WriteDeflatePreamble(output);
}
// Compress data but don't format as block (doesn't have header and footer)
internal void GetCompressedData(DeflateInput input, OutputBuffer output)
{
GetCompressedOutput(input, output, -1);
}
static internal void WriteChar(byte b, OutputBuffer output)
{
uint code = FastEncoderStatics.FastEncoderLiteralCodeInfo[b];
output.WriteBits((int)code & 31, code >> 5);
}
private bool SafeToWriteTo(OutputBuffer output) // can we safely continue writing to output buffer
{
return(output.FreeBytes > FastEncoderStatics.MaxCodeLen);
}