public static MemoryStream Decompress(Stream data)
{
int comptype = data.ReadByte();
if (comptype == 0)
throw new NotImplementedException("Compression type 0 is not currently supported");
LinkedNode tail = BuildList(sPrime[comptype]);
LinkedNode head = BuildTree(tail);
MemoryStream outputstream = new MemoryStream();
BitStream bitstream = new BitStream(data);
int decoded;
do
{
LinkedNode node = Decode(bitstream, head);
decoded = node.DecompressedValue;
switch(decoded)
{
case 256:
break;
case 257:
int newvalue = bitstream.ReadBits(8);
outputstream.WriteByte((byte)newvalue);
tail = InsertNode(tail, newvalue);
break;
default:
outputstream.WriteByte((byte)decoded);
break;
}
} while (decoded != 256);
outputstream.Seek(0, SeekOrigin.Begin);
return outputstream;
}
private static LinkedNode Decode(BitStream input, LinkedNode head)
{
LinkedNode node = head;
while(node.Child0 != null)
{
int bit = input.ReadBits(1);
if (bit == -1)
throw new Exception("Unexpected end of file");
node = bit == 0 ? node.Child0 : node.Child1;
}
return node;
}
public PKLibDecompress(Stream input)
{
_bitstream = new BitStream(input);
_compressionType = (CompressionType)input.ReadByte();
if (_compressionType != CompressionType.Binary && _compressionType != CompressionType.Ascii)
throw new InvalidDataException("Invalid compression type: " + _compressionType);
_dictSizeBits = input.ReadByte();
// This is 6 in test cases
if(4 > _dictSizeBits || _dictSizeBits > 6)
throw new InvalidDataException("Invalid dictionary size: " + _dictSizeBits);
}