private static int DecodeLiteral(BitStreamReader bitStream, PkLibCompressionType compressionType)
{
Contract.Requires(bitStream != null);
// Return values:
// 0x000 to 0x0ff: One byte from compressed file.
// 0x100 to 0x305: Copy previous block (0x100 = 1 byte).
// -1: End of stream.
switch (bitStream.ReadBits(1))
{
case -1:
return(-1);
case 1:
// The next bits are positions in buffers.
int pos = _sPosition2[bitStream.PeekByte()];
// Skip the bits we just used.
var numBits = _sLenBits[pos];
Contract.Assume(numBits < BitStreamReader.MaxBitCount);
if (bitStream.ReadBits(numBits) == -1)
{
return(-1);
}
var nBits = _sExLenBits[pos];
if (nBits != 0)
{
Contract.Assume(nBits < BitStreamReader.MaxBitCount);
var val2 = bitStream.ReadBits(nBits);
if (val2 == -1 && (pos + val2 != 0x10e))
{
return(-1);
}
pos = _sLenBase[pos] + val2;
}
return(pos + 0x100); // Return number of bytes to repeat.
case 0:
if (compressionType == PkLibCompressionType.Binary)
{
return(bitStream.ReadBits(sizeof(byte) * 8));
}
// TODO: Implement ASCII mode.
throw new NotImplementedException("ASCII mode is not yet implemented.");
default:
return(0);
}
}
private static int DecodeDistance(BitStreamReader bitStream, int length, int dictSizeBits)
{
Contract.Requires(bitStream != null);
Contract.Requires(length >= 0);
Contract.Requires(dictSizeBits >= 0);
Contract.Requires(dictSizeBits < BitStreamReader.MaxBitCount);
if (bitStream.EnsureBits(8) == false)
{
return(0);
}
var pos = (int)_sPosition1[bitStream.PeekByte()];
var skip = _sDistBits[pos]; // Number of bits to skip.
// Skip the appropriate number of bits
Contract.Assume(skip < BitStreamReader.MaxBitCount);
if (bitStream.ReadBits(skip) == -1)
{
return(0);
}
if (length == 2)
{
if (bitStream.EnsureBits(2) == false)
{
return(0);
}
pos = (pos << 2) | bitStream.ReadBits(2);
}
else
{
if (bitStream.EnsureBits(dictSizeBits) == false)
{
return(0);
}
pos = ((pos << dictSizeBits)) | bitStream.ReadBits(dictSizeBits);
}
return(pos + 1);
}
private static int DecodeDistance(BitStreamReader bitStream, int length, int dictSizeBits)
{
Contract.Requires(bitStream != null);
Contract.Requires(length >= 0);
Contract.Requires(dictSizeBits >= 0);
Contract.Requires(dictSizeBits < BitStreamReader.MaxBitCount);
if (bitStream.EnsureBits(8) == false)
return 0;
var pos = (int)_sPosition1[bitStream.PeekByte()];
var skip = _sDistBits[pos]; // Number of bits to skip.
// Skip the appropriate number of bits
Contract.Assume(skip < BitStreamReader.MaxBitCount);
if (bitStream.ReadBits(skip) == -1)
return 0;
if (length == 2)
{
if (bitStream.EnsureBits(2) == false)
return 0;
pos = (pos << 2) | bitStream.ReadBits(2);
}
else
{
if (bitStream.EnsureBits(dictSizeBits) == false)
return 0;
pos = ((pos << dictSizeBits)) | bitStream.ReadBits(dictSizeBits);
}
return pos + 1;
}
private static int DecodeLiteral(BitStreamReader bitStream, PkLibCompressionType compressionType)
{
Contract.Requires(bitStream != null);
// Return values:
// 0x000 to 0x0ff: One byte from compressed file.
// 0x100 to 0x305: Copy previous block (0x100 = 1 byte).
// -1: End of stream.
switch (bitStream.ReadBits(1))
{
case -1:
return -1;
case 1:
// The next bits are positions in buffers.
int pos = _sPosition2[bitStream.PeekByte()];
// Skip the bits we just used.
var numBits = _sLenBits[pos];
Contract.Assume(numBits < BitStreamReader.MaxBitCount);
if (bitStream.ReadBits(numBits) == -1)
return -1;
var nBits = _sExLenBits[pos];
if (nBits != 0)
{
Contract.Assume(nBits < BitStreamReader.MaxBitCount);
var val2 = bitStream.ReadBits(nBits);
if (val2 == -1 && (pos + val2 != 0x10e))
return -1;
pos = _sLenBase[pos] + val2;
}
return pos + 0x100; // Return number of bytes to repeat.
case 0:
if (compressionType == PkLibCompressionType.Binary)
return bitStream.ReadBits(sizeof(byte) * 8);
// TODO: Implement ASCII mode.
throw new NotImplementedException("ASCII mode is not yet implemented.");
default:
return 0;
}
}
