ddidderr/zstd-rs
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minor compression gain

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This commit is contained in:
Yann Collet
2016-01-31 00:58:06 +01:00
parent a6f54ddb2c
commit e93d6ced17
6 changed files with 95 additions and 57 deletions
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lib/zstd_compress.c
+31 -18
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@@ -547,9 +547,13 @@ size_t ZSTD_compressSequences(ZSTD_CCtx* zc,
if ((oend-op) < MIN_SEQUENCES_SIZE)
return ERROR(dstSize_tooSmall);
MEM_writeLE16(op, (U16)nbSeq); op+=2;
seqHead = op;
if (nbSeq==0) goto _check_compressibility;
/* dumps : contains rests of large lengths */
if ((oend-op) < 3 /* dumps */ + 1 /*seqHead*/)
return ERROR(dstSize_tooSmall);
seqHead = op;
{
size_t dumpsLength = seqStorePtr->dumps - seqStorePtr->dumpsStart;
if (dumpsLength < 512) {
@@ -572,9 +576,9 @@ size_t ZSTD_compressSequences(ZSTD_CCtx* zc,
/* CTable for Literal Lengths */
max = MaxLL;
mostFrequent = FSE_countFast(count, &max, seqStorePtr->litLengthStart, nbSeq);
mostFrequent = FSE_countFast(count, &max, llTable, nbSeq);
if ((mostFrequent == nbSeq) && (nbSeq > 2)) {
*op++ = *(seqStorePtr->litLengthStart);
*op++ = llTable[0];
FSE_buildCTable_rle(CTable_LitLength, (BYTE)max);
LLtype = FSE_ENCODING_RLE;
} else if ((zc->flagStaticTables) && (nbSeq < MAX_SEQ_FOR_STATIC_FSE)) {
@@ -584,8 +588,10 @@ size_t ZSTD_compressSequences(ZSTD_CCtx* zc,
LLtype = FSE_ENCODING_RAW;
} else {
size_t NCountSize;
size_t nbSeq_1 = nbSeq;
U32 tableLog = FSE_optimalTableLog(LLFSELog, nbSeq, max);
FSE_normalizeCount(norm, tableLog, count, nbSeq, max);
if (count[llTable[nbSeq-1]]>1) { count[llTable[nbSeq-1]]--; nbSeq_1--; }
FSE_normalizeCount(norm, tableLog, count, nbSeq_1, max);
NCountSize = FSE_writeNCount(op, oend-op, norm, max, tableLog); /* overflow protected */
if (FSE_isError(NCountSize)) return ERROR(GENERIC);
op += NCountSize;
@@ -603,7 +609,7 @@ size_t ZSTD_compressSequences(ZSTD_CCtx* zc,
max = MaxOff;
mostFrequent = FSE_countFast(count, &max, offCodeTable, nbSeq);
if ((mostFrequent == nbSeq) && (nbSeq > 2)) {
*op++ = *offCodeTable;
*op++ = offCodeTable[0];
FSE_buildCTable_rle(CTable_OffsetBits, (BYTE)max);
Offtype = FSE_ENCODING_RLE;
} else if ((zc->flagStaticTables) && (nbSeq < MAX_SEQ_FOR_STATIC_FSE)) {
@@ -613,8 +619,10 @@ size_t ZSTD_compressSequences(ZSTD_CCtx* zc,
Offtype = FSE_ENCODING_RAW;
} else {
size_t NCountSize;
size_t nbSeq_1 = nbSeq;
U32 tableLog = FSE_optimalTableLog(OffFSELog, nbSeq, max);
FSE_normalizeCount(norm, tableLog, count, nbSeq, max);
if (count[offCodeTable[nbSeq-1]]>1) { count[offCodeTable[nbSeq-1]]--; nbSeq_1--; }
FSE_normalizeCount(norm, tableLog, count, nbSeq_1, max);
NCountSize = FSE_writeNCount(op, oend-op, norm, max, tableLog); /* overflow protected */
if (FSE_isError(NCountSize)) return ERROR(GENERIC);
op += NCountSize;
@@ -624,9 +632,9 @@ size_t ZSTD_compressSequences(ZSTD_CCtx* zc,
/* CTable for MatchLengths */
max = MaxML;
mostFrequent = FSE_countFast(count, &max, seqStorePtr->matchLengthStart, nbSeq);
mostFrequent = FSE_countFast(count, &max, mlTable, nbSeq);
if ((mostFrequent == nbSeq) && (nbSeq > 2)) {
*op++ = *seqStorePtr->matchLengthStart;
*op++ = *mlTable;
FSE_buildCTable_rle(CTable_MatchLength, (BYTE)max);
MLtype = FSE_ENCODING_RLE;
} else if ((zc->flagStaticTables) && (nbSeq < MAX_SEQ_FOR_STATIC_FSE)) {
@@ -659,22 +667,26 @@ size_t ZSTD_compressSequences(ZSTD_CCtx* zc,
errorCode = BIT_initCStream(&blockStream, op, oend-op);
if (ERR_isError(errorCode)) return ERROR(dstSize_tooSmall); /* not enough space remaining */
FSE_initCState(&stateMatchLength, CTable_MatchLength);
FSE_initCState(&stateOffsetBits, CTable_OffsetBits);
FSE_initCState(&stateLitLength, CTable_LitLength);
for (i=(int)nbSeq-1; i>=0; i--) {
/* first symbols */
FSE_initCState2(&stateMatchLength, CTable_MatchLength, mlTable[nbSeq-1]);
FSE_initCState2(&stateOffsetBits, CTable_OffsetBits, offCodeTable[nbSeq-1]);
FSE_initCState2(&stateLitLength, CTable_LitLength, llTable[nbSeq-1]);
BIT_addBits(&blockStream, offsetTable[nbSeq-1], offCodeTable[nbSeq-1] ? (offCodeTable[nbSeq-1]-1) : 0);
BIT_flushBits(&blockStream);
for (i=(int)nbSeq-2; i>=0; i--) {
BYTE mlCode = mlTable[i];
U32 offset = offsetTable[i];
BYTE offCode = offCodeTable[i]; /* 32b*/ /* 64b*/
U32 nbBits = (offCode-1) * (!!offCode);
U32 nbBits = (offCode-1) + (!offCode);
BYTE litLength = llTable[i]; /* (7)*/ /* (7)*/
FSE_encodeSymbol(&blockStream, &stateMatchLength, mlCode); /* 17 */ /* 17 */
if (MEM_32bits()) BIT_flushBits(&blockStream); /* 7 */
BIT_addBits(&blockStream, offset, nbBits); /* 31 */ /* 42 */ /* 24 bits max in 32-bits mode */
if (MEM_32bits()) BIT_flushBits(&blockStream); /* 7 */
FSE_encodeSymbol(&blockStream, &stateOffsetBits, offCode); /* 16 */ /* 51 */
FSE_encodeSymbol(&blockStream, &stateLitLength, litLength); /* 26 */ /* 61 */
FSE_encodeSymbol(&blockStream, &stateOffsetBits, offCode); /* 16 */ /* 51 */
if (MEM_32bits()) BIT_flushBits(&blockStream); /* 7 */
BIT_addBits(&blockStream, offset, nbBits); /* 31 */ /* 42 */ /* 24 bits max in 32-bits mode */
BIT_flushBits(&blockStream); /* 7 */ /* 7 */
}
@@ -688,14 +700,15 @@ size_t ZSTD_compressSequences(ZSTD_CCtx* zc,
}
/* check compressibility */
_check_compressibility:
if ((size_t)(op-ostart) >= maxCSize) return 0;
return op - ostart;
}
/** ZSTD_storeSeq
Store a sequence (literal length, literals, offset code and match length) into seqStore_t
/*! ZSTD_storeSeq
Store a sequence (literal length, literals, offset code and match length code) into seqStore_t
@offsetCode : distance to match, or 0 == repCode
@matchCode : matchLength - MINMATCH
*/