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Updated FSE

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Faster speed on barely compressible data
This commit is contained in:
Yann Collet
2015-02-21 03:31:59 +01:00
parent 00be3437a8
commit a3c75bad5a
2 changed files with 108 additions and 15 deletions
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lib/zstd.c
+7 -5
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@@ -613,25 +613,27 @@ static size_t ZSTD_compressLiterals (void* dst, size_t dstSize,
size_t errorCode;
const size_t minGain = ZSTD_minGain(srcSize);
// early out
/* early out */
if (dstSize < FSE_compressBound(srcSize)) return (size_t)-ZSTD_ERROR_maxDstSize_tooSmall;
// Scan input and build symbol stats
/* Scan input and build symbol stats */
errorCode = FSE_count (count, ip, srcSize, &maxSymbolValue);
if (FSE_isError(errorCode)) return (size_t)-ZSTD_ERROR_GENERIC;
if (errorCode == srcSize) return 1;
if (errorCode < ((srcSize * 7) >> 10)) return 0;
//if (errorCode < ((srcSize * 7) >> 10)) return 0;
//if (errorCode < (srcSize >> 7)) return 0;
if (errorCode < (srcSize >> 6)) return 0; /* heuristic : probably not compressible enough */
tableLog = FSE_optimalTableLog(tableLog, srcSize, maxSymbolValue);
errorCode = (int)FSE_normalizeCount (norm, tableLog, count, srcSize, maxSymbolValue);
if (FSE_isError(errorCode)) return (size_t)-ZSTD_ERROR_GENERIC;
// Write table description header
/* Write table description header */
errorCode = FSE_writeHeader (op, FSE_MAX_HEADERSIZE, norm, maxSymbolValue, tableLog);
if (FSE_isError(errorCode)) return (size_t)-ZSTD_ERROR_GENERIC;
op += errorCode;
// Compress
/* Compress */
errorCode = FSE_buildCTable (&CTable, norm, maxSymbolValue, tableLog);
if (FSE_isError(errorCode)) return (size_t)-ZSTD_ERROR_GENERIC;
errorCode = ZSTD_compressLiterals_usingCTable(op, oend - op, ip, srcSize, &CTable);