// Output the block type and tree structure for our hard-coded trees.
// Contains following data:
// "final" block flag 1 bit
// BLOCKTYPE_DYNAMIC 2 bits
// FastEncoderLiteralTreeLength
// FastEncoderDistanceTreeLength
//
internal static void WriteDeflatePreamble(OutputBuffer output)
{
//Debug.Assert( bitCount == 0, "bitCount must be zero before writing tree bit!");
output.WriteBytes(FastEncoderStatics.FastEncoderTreeStructureData, 0, FastEncoderStatics.FastEncoderTreeStructureData.Length);
output.WriteBits(FastEncoderStatics.FastEncoderPostTreeBitCount, FastEncoderStatics.FastEncoderPostTreeBitBuf);
}
// 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);
}
}