public override byte[] Decompress(byte[] buf)
{
var tableID = BitList.From(buf).SetMinimumSize(16).ToUInt16();
if (FixedTableCompressions.TryGetValue(tableID, out var compType))
{
var comp = Activator.CreateInstance(compType) as CompressionBase;
return(comp.Decompress(buf));
}
else
{
return((new CompressionHuffmanCoding()).Decompress(buf));
}
}
public BitList GetBitResult(INode leaf)
{
var ret = new List <bool>();
InternalNode parent = null;
for (var node = leaf; node != null; node = parent)
{
parent = GetParent(node);
if (parent != null)
{
ret.Add(ReferenceEquals(node, parent.Right));
}
}
return(BitList.From(((IEnumerable <bool>)ret).Reverse()));
}
public override byte[] Decompress(byte[] buf)
{
var bits = new BitList(buf);
if (bits.Count < 24)
{
throw new Exception("Table Format Error: Size is not enough");
}
var tableID = bits.SetMinimumSize(16).ToUInt16();
if (tableID != 0xffff)
{
throw new Exception("Table Format Error");
}
return(bits.ToBytes().Skip(2).ToArray());
}
public override byte[] Compress(byte[] buf)
{
var ret = MakeTableBinary(TableID, Table, out var table);
// ADD DATA FIELDS
ret.Add(BitList.MakeVariableBits((UInt64)buf.Length)); // [DA] Data Bytes
foreach (var c in buf)
{
ret.Add(table[c]); // [DB] Huffman code
if (ret.ByteCount >= LimitSize)
{
return(null);
}
}
ret.AddPad(); // [DC] padding
return(ret.ToByteArray());
}
public static Dictionary <BitList, byte> ReadTableBinary(BitList bits, out int nextBitIndex)
{
// === READ TABLE ===
var table = new Dictionary <BitList, byte>();
var tableCount = BitList.From(bits.Subbit(0, 16)).SetMinimumSize(16).ToUInt16(); // [TA]
Debug.Assert(tableCount < 32768);
nextBitIndex = 16;
for (var i = 0; i < tableCount; i++)
{
var value = BitList.From(bits.Subbit(nextBitIndex, 8)).ToByte(); // [TB]
nextBitIndex += 8;
var bitLen = (int)BitList.GetNumberFromVariableBits(bits.Subbit(nextBitIndex), out var numbits);
nextBitIndex += numbits;
table[BitList.From(bits.Subbit(nextBitIndex, bitLen))] = value; // [TE]
nextBitIndex += bitLen;
}
if (nextBitIndex % 8 != 0)
{
nextBitIndex += 8 - nextBitIndex % 8; // [TF]
}
return(table);
}
/// <summary>
/// copy constructor
/// </summary>
/// <param name="from"></param>
public BitList(BitList from)
{
Bytes.AddRange(from.Bytes);
Count = from.Count;
}
