/// <summary>
/// Encode given data using LZ coding and given dictionary
/// </summary>
/// <param name="input">Byte array to encode</param>
/// <param name="encoderDic">Dictionary implementation</param>
/// <returns>Encoded byte array</returns>
private static byte[] _asLZEncoded(this byte[] input, ILZ78CodingTable <int> encoderDic)
{
var twoPass = true;
for (int i = 0; i < 256; i++)
{
var searchKey = new[] { (byte)i };
var codeWord = i;
encoderDic.Insert(searchKey, codeWord);
}
var addedCodeWords = 0;
using (var encodedOutput = new ByteMemoryStream((int)(input.Length / 0.6))) {
var P = new byte[] { input[0] };
for (int i = 1; i < input.Length; i++)
{
var C = new byte[] { input[i] };
var PC = P.Concatenate(C);
var item = encoderDic.Search(PC);
if (item != null)
{
P = PC;
}
else
{
var item2 = encoderDic.Search(P);
encodedOutput.AddBytes(item2.CodeWord.AsBytes());
addedCodeWords++;
encoderDic.Insert(PC, encoderDic.Count);
P = C;
}
}
var item3 = encoderDic.Search(P);
encodedOutput.AddBytes(item3.CodeWord.AsBytes());
addedCodeWords++;
var encodedBytes = encodedOutput.ReadBytes();
if (twoPass)
{
return(encodedBytes.AsCompressed(encoderDic.Count - 1, addedCodeWords));
}
else
{
return(encodedBytes);
}
}
}
/// <summary>
/// Decodes LZ compressed bytes
/// </summary>
/// <param name="codes">Compressed bytes</param>
/// <param name="decoderDic">Dictionary to use in decoding</param>
/// <returns>Decompressed data</returns>
private static byte[] _asLZDecoded(byte[] codes, ILZ78CodingTable <byte[]> decoderDic)
{
for (int i = 0; i < 256; i++)
{
var searchKey = i.AsBytes();
var codeWord = new[] { (byte)i };
decoderDic.Insert(searchKey, codeWord);
}
//decompress compressed codes as int 32 byte array
var decompressedCodes = codes.AsDecompressed();
using (var decodedOutPut = new ByteMemoryStream(decompressedCodes.Length * 2)) {
var O = decompressedCodes.AsInt(0).AsBytes();
var S = new byte[0];
var C2 = new byte[0];
var item = decoderDic.Search(O);
decodedOutPut.AddBytes(item.CodeWord);
for (int i = 4; i < decompressedCodes.Length; i += 4)
{
var N = decompressedCodes.AsInt(i).AsBytes();
var itemN = decoderDic.Search(N);
var itemO = decoderDic.Search(O);
if (itemN == null)
{
S = itemO.CodeWord.Concatenate(C2);
}
else
{
S = itemN.CodeWord;
}
decodedOutPut.AddBytes(S);
C2 = new byte[] { S[0] };
var C3 = itemO.CodeWord.Concatenate(C2);
decoderDic.Insert(((decoderDic.Count)).AsBytes(), C3);
O = N;
}
return(decodedOutPut.ReadBytes());
}
}