private static void Push(UInt16BE_NE_H_OutputBitStream bitStream, bool bit, Stream destination, MemoryStream data)
{
if (bitStream.Push(bit))
{
byte[] bytes = data.ToArray();
destination.Write(bytes, 0, bytes.Length);
data.SetLength(0);
}
}
private static void EncodeInternal(Stream destination, byte[] buffer, long slidingWindow, long recLength, long size)
{
UInt16BE_NE_H_OutputBitStream bitStream = new UInt16BE_NE_H_OutputBitStream(destination);
MemoryStream data = new MemoryStream();
if (size > 0)
{
long bPointer = 2, longestMatchOffset = 0;
bitStream.Push(false);
NeutralEndian.Write1(data, buffer[0]);
NeutralEndian.Write1(data, buffer[1]);
while (bPointer < size)
{
long matchMax = Math.Min(recLength, size - bPointer);
long backSearchMax = Math.Max(bPointer - slidingWindow, 0);
long longestMatch = 2;
long backSearch = bPointer;
do
{
backSearch -= 2;
long currentCount = 0;
while (buffer[backSearch + currentCount] == buffer[bPointer + currentCount] && buffer[backSearch + currentCount + 1] == buffer[bPointer + currentCount + 1])
{
currentCount += 2;
if (currentCount >= matchMax)
{
// Match is as big as the look-forward buffer (or file) will let it be
break;
}
}
if (currentCount > longestMatch)
{
// New 'best' match
longestMatch = currentCount;
longestMatchOffset = backSearch;
}
} while (backSearch > backSearchMax); // Repeat for as far back as search buffer will let us
long iCount = longestMatch / 2; // Comper counts in words (16 bits)
long iOffset = (longestMatchOffset - bPointer) / 2; // Comper's offsets count in words (16-bits)
if (iCount == 1)
{
// Symbolwise match
Push(bitStream, false, destination, data);
NeutralEndian.Write1(data, buffer[bPointer]);
NeutralEndian.Write1(data, buffer[bPointer + 1]);
}
else
{
// Dictionary match
Push(bitStream, true, destination, data);
NeutralEndian.Write1(data, (byte)(iOffset));
NeutralEndian.Write1(data, (byte)(iCount - 1));
}
bPointer += iCount * 2; // iCount counts in words (16-bits), so we correct it to bytes (8-bits) here
}
}
Push(bitStream, true, destination, data);
NeutralEndian.Write1(data, 0);
NeutralEndian.Write1(data, 0);
bitStream.Flush(true);
byte[] bytes = data.ToArray();
destination.Write(bytes, 0, bytes.Length);
}
