private byte[] PatternCompress(byte[] data)
{
for (int i=0;i<data.Length;i++)
{
UInt16 matchCount=0;
int current = data[i];
int lookupPos = 0;
UInt16 bestMatchCount = 0;
int bestMatchPos = 0;
if (i<data.Length-2)
{
byte current2 = data[i+1];
byte current3 = data[i+2];
ulong key = (ulong)current << 16;
key |= (ulong)current2 << 8;
key |= (ulong)current3 ;
int prevIndex = (int)patternHashArray[key];
int currentPrevIndex = prevIndex;
bestMatchCount = 0;
bestMatchPos = 0;
if (prevIndex != 0)
{
do
{
matchCount = 0;
PatternLink link = patternLinkArray[currentPrevIndex];
lookupPos = (int)link.FilePosition;
while (matchCount+i < data.Length && matchCount < UInt16.MaxValue && data[i+matchCount] == data[lookupPos+matchCount])
matchCount++;
//matchCount --;
if (matchCount > bestMatchCount)
{
bestMatchCount = matchCount;
bestMatchPos = lookupPos;
}
currentPrevIndex = link.NextMatch;
}while (currentPrevIndex != 0);
}
patternHashArray[key] = (ulong)i+1;
PatternLink newLink = new PatternLink() ;
newLink.FilePosition = (ulong)i;
newLink.NextMatch = prevIndex;
patternLinkArray[i+1]=newLink;
}
int relativeLookupPos = i-bestMatchPos;
if (bestMatchCount > 4 && relativeLookupPos < 0x100 && bestMatchCount < 0x100)
{
WriteBytes (escapeByte,1);
WriteBytes (0u,1); // 0 = short relative
WriteBytes((ulong)bestMatchCount,1);
WriteBytes((ulong)relativeLookupPos,1);
i += bestMatchCount-1;
}
else if (bestMatchCount > 5 && relativeLookupPos < 0x10000 && bestMatchCount <0x100)
{
WriteBytes (escapeByte,1);
WriteBytes (1u,1); // 1 = 65k range relative
WriteBytes((ulong)bestMatchCount,1);
WriteBytes((ulong)relativeLookupPos,2);
i += bestMatchCount-1;
}
else
if (bestMatchCount > 8 )
{
WriteBytes (escapeByte,1);
WriteBytes (2u,1); // long lookup
WriteBytes((ulong)bestMatchCount,2);
WriteBytes((ulong)bestMatchPos,4);
i += bestMatchCount-1;
}
else
{
WriteBytes((ulong)current,1);
}
}
byte[] compressedBytes = new byte[compressedStream.Length] ;
compressedStream.Position = 0;
compressedStream.Read(compressedBytes,0,compressedBytes.Length);
return compressedBytes;
}
private byte[] PatternCompress(byte[] data)
{
for (int i = 0; i < data.Length; i++)
{
UInt16 matchCount = 0;
int current = data[i];
int lookupPos = 0;
UInt16 bestMatchCount = 0;
int bestMatchPos = 0;
if (i < data.Length - 2)
{
byte current2 = data[i + 1];
byte current3 = data[i + 2];
ulong key = (ulong)current << 16;
key |= (ulong)current2 << 8;
key |= (ulong)current3;
int prevIndex = (int)patternHashArray[key];
int currentPrevIndex = prevIndex;
bestMatchCount = 0;
bestMatchPos = 0;
if (prevIndex != 0)
{
do
{
matchCount = 0;
PatternLink link = patternLinkArray[currentPrevIndex];
lookupPos = (int)link.FilePosition;
while (matchCount + i < data.Length && matchCount < UInt16.MaxValue && data[i + matchCount] == data[lookupPos + matchCount])
{
matchCount++;
}
//matchCount --;
if (matchCount > bestMatchCount)
{
bestMatchCount = matchCount;
bestMatchPos = lookupPos;
}
currentPrevIndex = link.NextMatch;
}while (currentPrevIndex != 0);
}
patternHashArray[key] = (ulong)i + 1;
PatternLink newLink = new PatternLink();
newLink.FilePosition = (ulong)i;
newLink.NextMatch = prevIndex;
patternLinkArray[i + 1] = newLink;
}
int relativeLookupPos = i - bestMatchPos;
if (bestMatchCount > 4 && relativeLookupPos < 0x100 && bestMatchCount < 0x100)
{
WriteBytes(escapeByte, 1);
WriteBytes(0u, 1); // 0 = short relative
WriteBytes((ulong)bestMatchCount, 1);
WriteBytes((ulong)relativeLookupPos, 1);
i += bestMatchCount - 1;
}
else if (bestMatchCount > 5 && relativeLookupPos < 0x10000 && bestMatchCount < 0x100)
{
WriteBytes(escapeByte, 1);
WriteBytes(1u, 1); // 1 = 65k range relative
WriteBytes((ulong)bestMatchCount, 1);
WriteBytes((ulong)relativeLookupPos, 2);
i += bestMatchCount - 1;
}
else
if (bestMatchCount > 8)
{
WriteBytes(escapeByte, 1);
WriteBytes(2u, 1); // long lookup
WriteBytes((ulong)bestMatchCount, 2);
WriteBytes((ulong)bestMatchPos, 4);
i += bestMatchCount - 1;
}
else
{
WriteBytes((ulong)current, 1);
}
}
byte[] compressedBytes = new byte[compressedStream.Length];
compressedStream.Position = 0;
compressedStream.Read(compressedBytes, 0, compressedBytes.Length);
return(compressedBytes);
}