private BestResult FindBest(byte[] window, byte[] nextBytes)
{
BestResult result = new BestResult();
result.Length = 1;
result.Character = nextBytes[0];
for (int i = window.Length - 1; i >= 0; i--)
{
//if window matches first next byte
if (window[i] == nextBytes[0])
{
ushort length = 1;
List <byte> expandingWindow = new List <byte>(window);
expandingWindow.Add(nextBytes[0]);
for (int j = 1; j < nextBytes.Length; j++)
{
if (expandingWindow[i + j] != nextBytes[j])
{
break;
}
expandingWindow.Add(nextBytes[j]);
length++;
}
if (length > result.Length)
{
result.Length = length;
result.Offset = (ushort)i;
}
}
}
result.IsCompressed = result.Length != 1;
return(result);
}
private void compress_Mode(byte[] buffer, byte mode, ushort windowSize)
{
int restBytes = (int)(16 - Math.Log(windowSize, 2));
int nextBytesSize = (int)Math.Pow(2, restBytes) + 1;
using (BinaryWriter writer = new BinaryWriter(new FileStream(FilePath, FileMode.Create)))
{
writer.Write(LZSSHeader.GetBytes(), 0, 16);
writer.Write(buffer[0]);
byte[] chunk = new byte[17];
byte chunkLength = 1;
sbyte flagpos = 7;
for (int i = 1; i < buffer.Length; i++)
{
if (flagpos == -1)
{
writer.Write(chunk, 0, chunkLength);
flagpos = 7;
chunkLength = 1;
chunk[0] = 0;
}
byte[] window;
if (i < windowSize)
{
window = new byte[i];
}
else
{
window = new byte[windowSize];
}
if (i > windowSize)
{
Array.Copy(buffer, i - windowSize, window, 0, window.Length);
}
else
{
Array.Copy(buffer, 0, window, 0, window.Length);
}
byte[] nextBytes = new byte[nextBytesSize];
if (i + nextBytesSize > buffer.Length)
{
Array.Copy(buffer, i, nextBytes, 0, buffer.Length - i);
}
else
{
Array.Copy(buffer, i, nextBytes, 0, nextBytesSize);
}
BestResult result = FindBest(window, nextBytes);
if (result.IsCompressed)
{
if (result.Length + i > buffer.Length)
{
result.Length = (byte)(buffer.Length - i);
}
CompressedWord word = new CompressedWord(result.Offset, result.Length);
byte[] wordBytes = word.GetBytes(mode);
Array.Copy(wordBytes, 0, chunk, chunkLength, 2);
chunkLength += 2;
chunk[0] |= (byte)(1 << flagpos);
i += result.Length - 1;
}
else
{
byte[] compressed = new byte[1];
compressed[0] = result.Character;
Array.Copy(compressed, 0, chunk, chunkLength, 1);
chunkLength += 1;
}
flagpos--;
}
if (flagpos != -1)
{
writer.Write(chunk, 0, chunkLength);
}
}
}
