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faster string in string, WIP

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dwsJason 2020-07-15 23:59:33 -04:00
parent e358c2a937
commit 955e8cf1d5
1 changed files with 85 additions and 10 deletions
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95
source/lzb.cpp
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@ -27,7 +27,7 @@ static int EmitReference(unsigned char *pDest, int dictionaryOffset, DataString&
static int DictionaryMatch(const DataString& data, int dictionarySize);
// Stuff I need for a faster version
static DataString LongestMatch(const DataString& data, const DataString* dictionary);
static DataString LongestMatch(const DataString& data, const DataString& dictionary);
//
// New Version, still Brute Force, but not as many times
@ -47,7 +47,7 @@ int LZB_Compress(unsigned char* pDest, unsigned char* pSource, int sourceSize)
sourceData.size = sourceSize;
// Remember, this eventually will point at the frame buffer
dictionaryData.pData = pSource
dictionaryData.pData = pSource;
dictionaryData.size = 0;
// dumb last emit is a literal stuff
@ -61,7 +61,7 @@ int LZB_Compress(unsigned char* pDest, unsigned char* pSource, int sourceSize)
if (0 == candidateData.size)
{
candidateData.size = 1;
candidateData.pData = sourceData;
candidateData.pData = sourceData.pData;
}
// Adjust source stream
@ -73,13 +73,13 @@ int LZB_Compress(unsigned char* pDest, unsigned char* pSource, int sourceSize)
if (candidateData.size > 3)
{
// Emit a dictionary reference
pDest += EmitReference(pDest, candidateData.pData - pSource, candidateData);
pDest += (int)EmitReference(pDest, (int)(candidateData.pData - dictionaryData.pData), candidateData);
bLastEmitIsLiteral = false;
}
else if (bLastEmitIsLiteral)
{
// Concatenate this literal onto the previous literal
pDest += ConcatLiteral(pLastLiteralDest, candidateData);
bLastEmitIsLiteral = false;
}
else
{
@ -90,7 +90,7 @@ int LZB_Compress(unsigned char* pDest, unsigned char* pSource, int sourceSize)
}
}
return pDest - pOriginalDest;
return (int)(pDest - pOriginalDest);
}
@ -98,7 +98,7 @@ int LZB_Compress(unsigned char* pDest, unsigned char* pSource, int sourceSize)
// This works, but it's stupidly slow, because it uses brute force, and
// because the brute force starts over everytime I grow the data string
//
int OLD_LZB_Compress(unsigned char* pDest, unsigned char* pSource, int sourceSize)
int old_LZB_Compress(unsigned char* pDest, unsigned char* pSource, int sourceSize)
{
printf("LZB_Compress %d bytes\n", sourceSize);
@ -226,6 +226,10 @@ static int AddDictionary(const DataString& data, int dictionarySize)
return dictionarySize;
}
//------------------------------------------------------------------------------
//
// Return longest match of data, in dictionary
//
DataString LongestMatch(const DataString& data, const DataString& dictionary)
{
@ -234,11 +238,84 @@ DataString LongestMatch(const DataString& data, const DataString& dictionary)
result.size = 0;
// Find the longest matching data in the dictionary
if (dictionary.size > 0)
if ((dictionary.size > 0) && (data.size > 0))
{
DataString candidate;
candidate.pData = data.pData;
candidate.size = 0;
// First Check for a pattern / run-length style match
// Check the end of the dictionary, to see if this data could be a
// pattern "run" (where we can repeat a pattern for X many times for free
// using the memcpy with overlapping source/dest buffers)
// (This is a dictionary based pattern run/length)
{
// Check for pattern sizes, start small
int max_pattern_size = 4096;
if (dictionary.size < max_pattern_size) max_pattern_size = dictionary.size;
if (data.size < max_pattern_size) max_pattern_size = data.size;
for (int pattern_size = 1; pattern_size <= max_pattern_size; ++pattern_size)
{
bool bMatch = true;
int pattern_start = dictionary.size - pattern_size;
for (int dataIndex = 0; dataIndex < data.size; ++dataIndex)
{
if (data.pData[ dataIndex ] == dictionary.pData[ pattern_start + (dataIndex % pattern_size) ])
{
candidate.pData = dictionary.pData + pattern_start;
candidate.size = dataIndex+1;
continue;
}
bMatch = false;
break;
}
if (candidate.size < pattern_size)
break;
if (candidate.size > result.size)
{
result = candidate;
}
}
}
// As an optimization
int dictionarySize = dictionary.size - 1; // This last string has already been checked by, the
// run-length matcher above
if (dictionarySize >= candidate.size)
{
// Check the dictionary for a match, brute force
for (int idx = 0; idx <= (dictionarySize-candidate.size); ++idx)
{
bool bMatch = true;
for (int dataIdx = 0; dataIdx < data.size; ++dataIdx)
{
if (data.pData[ dataIdx ] == dictionary.pData[ idx + dataIdx ])
{
if (dataIdx > (candidate.size-1))
{
candidate.pData = dictionary.pData + idx;
candidate.size = dataIdx - 1;
}
continue;
}
bMatch = false;
break;
}
if (candidate.size > result.size)
{
result = candidate;
break;
}
}
}
}
return result;
@ -302,8 +379,6 @@ static int DictionaryMatch(const DataString& data, int dictionarySize)
return -1;
}
int dictionaryOffset = 0;
int result = -1;
// Check the dictionary for a match, brute force