public static BitList MakeTableBinary(byte[] buf, out Dictionary <byte, BitList> table)
{
// Make Huffman Tree
var nodemap = Collection.Seq(256).Select(a => new ValueCount {
Value = (byte)a, Count = 0,
}).ToDictionary(a => a.Value);
for (var i = 0; i < buf.Length; i++)
{
nodemap[buf[i]].Count++;
}
var htree = new HuffmanTree(nodemap.Values.Where(a => a.Count > 0))
.Build();
table = new Dictionary <byte, BitList>();
foreach (ValueCount vc in htree)
{
table[vc.Value] = htree.GetBitResult(vc);
}
var ret = new BitList();
ret.Add((UInt16)table.Count); // [TA] TABLE COUNT (16bits) / < 32767 = Count
foreach (var kv in table)
{
ret.Add(kv.Key); // [TB] VALUE (8bits)
var lenbits = BitList.MakeVariableBits((UInt64)kv.Value.Count);
ret.Add(lenbits); // [TC] LENGTH OF BITPATTERN
ret.Add(kv.Value); // [TE] BIT Pattern (n bits)
}
ret.AddPad(); // [TF] padding
return(ret);
}
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());
}