public override CompressionResult Compress(byte[] source, int sourceOffset, int sourceLength, byte[] compressed, int compressedOffset, ref int compressedLength)
{
uint sourcePointer = 0;
uint sourceCurrentBlock = 0;
uint destPointer = 0;
// Set up the Lz Compression Dictionary
LzWindowDictionary lzDictionary = new LzWindowDictionary();
bool nonZeroDataFound = false;
for (int subBlock = 0; subBlock < sourceLength; subBlock += BlockSize)
{
lzDictionary.MinMatchAmount = 3;
sourceCurrentBlock = sourcePointer;
uint decompressedSize = (uint)Math.Min(sourceLength - subBlock, BlockSize);
uint compressedSize = 0;
// Start compression
uint headerPosition = destPointer;
compressed[compressedOffset + destPointer] = compressed[compressedOffset + destPointer + 1] = 0;
destPointer += 2;
while (sourcePointer - subBlock < decompressedSize)
{
if (destPointer + 1 >= compressedLength)
{
return(CompressionResult.Incompressible);
}
byte bitFlag = 0x0;
uint flagPosition = destPointer;
compressed[compressedOffset + destPointer] = bitFlag; // It will be filled in later
compressedSize++;
destPointer++;
for (int i = 0; i < 8; i++)
{
int lengthBits = 16 - s_compressionBits[sourcePointer - subBlock];
ushort lengthMask = (ushort)((1 << s_compressionBits[sourcePointer - subBlock]) - 1);
lzDictionary.MaxMatchAmount = Math.Min(1 << lengthBits, BlockSize - 1);
int[] lzSearchMatch = lzDictionary.Search(source, sourceOffset + subBlock, (uint)(sourcePointer - subBlock), decompressedSize);
if (lzSearchMatch[1] > 0)
{
// There is a compression match
if (destPointer + 2 >= compressedLength)
{
return(CompressionResult.Incompressible);
}
bitFlag |= (byte)(1 << i);
int rawOffset = lzSearchMatch[0];
int rawLength = lzSearchMatch[1];
int convertedOffset = (rawOffset - 1) << lengthBits;
int convertedSize = (rawLength - 3) & ((1 << lengthMask) - 1);
ushort convertedData = (ushort)(convertedOffset | convertedSize);
Utilities.WriteBytesLittleEndian(convertedData, compressed, compressedOffset + (int)destPointer);
lzDictionary.AddEntryRange(source, sourceOffset + subBlock, (int)(sourcePointer - subBlock), lzSearchMatch[1]);
sourcePointer += (uint)lzSearchMatch[1];
destPointer += 2;
compressedSize += 2;
}
else
{
// There wasn't a match
if (destPointer + 1 >= compressedLength)
{
return(CompressionResult.Incompressible);
}
bitFlag |= (byte)(0 << i);
if (source[sourceOffset + sourcePointer] != 0)
{
nonZeroDataFound = true;
}
compressed[compressedOffset + destPointer] = source[sourceOffset + sourcePointer];
lzDictionary.AddEntry(source, sourceOffset + subBlock, (int)(sourcePointer - subBlock));
sourcePointer++;
destPointer++;
compressedSize++;
}
// Check for out of bounds
if (sourcePointer - subBlock >= decompressedSize)
{
break;
}
}
// Write the real flag.
compressed[compressedOffset + flagPosition] = bitFlag;
}
// If compressed size >= block size just store block
if (compressedSize >= BlockSize)
{
// Set the header to indicate non-compressed block
Utilities.WriteBytesLittleEndian((ushort)(0x3000 | (BlockSize - 1)), compressed, compressedOffset + (int)headerPosition);
Array.Copy(source, (int)(sourceOffset + sourceCurrentBlock), compressed, (int)(compressedOffset + headerPosition + 2), BlockSize);
destPointer = (uint)(headerPosition + 2 + BlockSize);
// Make sure decompression stops by setting the next two bytes to null, prevents us from having to
// clear the rest of the array.
compressed[destPointer] = 0;
compressed[destPointer + 1] = 0;
}
else
{
// Set the header to indicate compressed and the right length
Utilities.WriteBytesLittleEndian((ushort)(0xb000 | (compressedSize - 1)), compressed, compressedOffset + (int)headerPosition);
}
lzDictionary.Reset();
}
if (destPointer >= sourceLength)
{
compressedLength = 0;
return(CompressionResult.Incompressible);
}
else if (nonZeroDataFound)
{
compressedLength = (int)destPointer;
return(CompressionResult.Compressed);
}
else
{
compressedLength = 0;
return(CompressionResult.AllZeros);
}
}
public override CompressionResult Compress(byte[] source, int sourceOffset, int sourceLength, byte[] compressed, int compressedOffset, ref int compressedLength)
{
uint sourcePointer = 0;
uint sourceCurrentBlock = 0;
uint destPointer = 0;
// Set up the Lz Compression Dictionary
LzWindowDictionary lzDictionary = new LzWindowDictionary();
bool nonZeroDataFound = false;
for (int subBlock = 0; subBlock < sourceLength; subBlock += BlockSize)
{
lzDictionary.MinMatchAmount = 3;
sourceCurrentBlock = sourcePointer;
uint decompressedSize = (uint)Math.Min(sourceLength - subBlock, BlockSize);
uint compressedSize = 0;
// Start compression
uint headerPosition = destPointer;
compressed[compressedOffset + destPointer] = compressed[compressedOffset + destPointer + 1] = 0;
destPointer += 2;
while (sourcePointer - subBlock < decompressedSize)
{
if (destPointer + 1 >= compressedLength)
{
return CompressionResult.Incompressible;
}
byte bitFlag = 0x0;
uint flagPosition = destPointer;
compressed[compressedOffset + destPointer] = bitFlag; // It will be filled in later
compressedSize++;
destPointer++;
for (int i = 0; i < 8; i++)
{
int lengthBits = 16 - s_compressionBits[sourcePointer - subBlock];
ushort lengthMask = (ushort)((1 << s_compressionBits[sourcePointer - subBlock]) - 1);
lzDictionary.MaxMatchAmount = Math.Min(1 << lengthBits, BlockSize - 1);
int[] lzSearchMatch = lzDictionary.Search(source, sourceOffset + subBlock, (uint)(sourcePointer - subBlock), decompressedSize);
if (lzSearchMatch[1] > 0)
{
// There is a compression match
if (destPointer + 2 >= compressedLength)
{
return CompressionResult.Incompressible;
}
bitFlag |= (byte)(1 << i);
int rawOffset = lzSearchMatch[0];
int rawLength = lzSearchMatch[1];
int convertedOffset = (rawOffset - 1) << lengthBits;
int convertedSize = (rawLength - 3) & ((1 << lengthMask) - 1);
ushort convertedData = (ushort)(convertedOffset | convertedSize);
Utilities.WriteBytesLittleEndian(convertedData, compressed, compressedOffset + (int)destPointer);
lzDictionary.AddEntryRange(source, sourceOffset + subBlock, (int)(sourcePointer - subBlock), lzSearchMatch[1]);
sourcePointer += (uint)lzSearchMatch[1];
destPointer += 2;
compressedSize += 2;
}
else
{
// There wasn't a match
if (destPointer + 1 >= compressedLength)
{
return CompressionResult.Incompressible;
}
bitFlag |= (byte)(0 << i);
if (source[sourceOffset + sourcePointer] != 0)
{
nonZeroDataFound = true;
}
compressed[compressedOffset + destPointer] = source[sourceOffset + sourcePointer];
lzDictionary.AddEntry(source, sourceOffset + subBlock, (int)(sourcePointer - subBlock));
sourcePointer++;
destPointer++;
compressedSize++;
}
// Check for out of bounds
if (sourcePointer - subBlock >= decompressedSize)
{
break;
}
}
// Write the real flag.
compressed[compressedOffset + flagPosition] = bitFlag;
}
// If compressed size >= block size just store block
if (compressedSize >= BlockSize)
{
// Set the header to indicate non-compressed block
Utilities.WriteBytesLittleEndian((ushort)(0x3000 | (BlockSize - 1)), compressed, compressedOffset + (int)headerPosition);
Array.Copy(source, (int)sourceOffset + sourceCurrentBlock, compressed, compressedOffset + headerPosition + 2, BlockSize);
destPointer = (uint)(headerPosition + 2 + BlockSize);
// Make sure decompression stops by setting the next two bytes to null, prevents us from having to
// clear the rest of the array.
compressed[destPointer] = 0;
compressed[destPointer + 1] = 0;
}
else
{
// Set the header to indicate compressed and the right length
Utilities.WriteBytesLittleEndian((ushort)(0xb000 | (compressedSize - 1)), compressed, compressedOffset + (int)headerPosition);
}
lzDictionary.Reset();
}
if (destPointer >= sourceLength)
{
compressedLength = 0;
return CompressionResult.Incompressible;
}
else if (nonZeroDataFound)
{
compressedLength = (int)destPointer;
return CompressionResult.Compressed;
}
else
{
compressedLength = 0;
return CompressionResult.AllZeros;
}
}
