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added negative compression levels

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negative compression level trade compression ratio for more compression speed.
They turn off huffman compression of literals,
and use row 0 as baseline with a stepSize = -cLevel.

added associated test in fuzzer

also added : new advanced parameter ZSTD_p_literalCompression
This commit is contained in:
Yann Collet
2018-03-11 05:21:53 -07:00
parent facc09aa03
commit a146ee04ae
5 changed files with 133 additions and 110 deletions
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lib/compress/zstd_fast.c
+24 -21
View File
@@ -42,7 +42,7 @@ FORCE_INLINE_TEMPLATE
size_t ZSTD_compressBlock_fast_generic(
ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
void const* src, size_t srcSize,
U32 const hlog, U32 const mls)
U32 const hlog, U32 const stepSize, U32 const mls)
{
U32* const hashTable = ms->hashTable;
const BYTE* const base = ms->window.base;
@@ -77,19 +77,19 @@ size_t ZSTD_compressBlock_fast_generic(
ip++;
ZSTD_storeSeq(seqStore, ip-anchor, anchor, 0, mLength-MINMATCH);
} else {
U32 offset;
if ( (matchIndex <= lowestIndex) || (MEM_read32(match) != MEM_read32(ip)) ) {
ip += ((ip-anchor) >> kSearchStrength) + 1;
if ( (matchIndex <= lowestIndex)
|| (MEM_read32(match) != MEM_read32(ip)) ) {
assert(stepSize >= 1);
ip += ((ip-anchor) >> kSearchStrength) + stepSize;
continue;
}
mLength = ZSTD_count(ip+4, match+4, iend) + 4;
offset = (U32)(ip-match);
while (((ip>anchor) & (match>lowest)) && (ip[-1] == match[-1])) { ip--; match--; mLength++; } /* catch up */
offset_2 = offset_1;
offset_1 = offset;
ZSTD_storeSeq(seqStore, ip-anchor, anchor, offset + ZSTD_REP_MOVE, mLength-MINMATCH);
}
{ U32 const offset = (U32)(ip-match);
while (((ip>anchor) & (match>lowest)) && (ip[-1] == match[-1])) { ip--; match--; mLength++; } /* catch up */
offset_2 = offset_1;
offset_1 = offset;
ZSTD_storeSeq(seqStore, ip-anchor, anchor, offset + ZSTD_REP_MOVE, mLength-MINMATCH);
} }
/* match found */
ip += mLength;
@@ -128,17 +128,18 @@ size_t ZSTD_compressBlock_fast(
{
U32 const hlog = cParams->hashLog;
U32 const mls = cParams->searchLength;
U32 const stepSize = cParams->targetLength;
switch(mls)
{
default: /* includes case 3 */
case 4 :
return ZSTD_compressBlock_fast_generic(ms, seqStore, rep, src, srcSize, hlog, 4);
return ZSTD_compressBlock_fast_generic(ms, seqStore, rep, src, srcSize, hlog, stepSize, 4);
case 5 :
return ZSTD_compressBlock_fast_generic(ms, seqStore, rep, src, srcSize, hlog, 5);
return ZSTD_compressBlock_fast_generic(ms, seqStore, rep, src, srcSize, hlog, stepSize, 5);
case 6 :
return ZSTD_compressBlock_fast_generic(ms, seqStore, rep, src, srcSize, hlog, 6);
return ZSTD_compressBlock_fast_generic(ms, seqStore, rep, src, srcSize, hlog, stepSize, 6);
case 7 :
return ZSTD_compressBlock_fast_generic(ms, seqStore, rep, src, srcSize, hlog, 7);
return ZSTD_compressBlock_fast_generic(ms, seqStore, rep, src, srcSize, hlog, stepSize, 7);
}
}
@@ -146,7 +147,7 @@ size_t ZSTD_compressBlock_fast(
static size_t ZSTD_compressBlock_fast_extDict_generic(
ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
void const* src, size_t srcSize,
U32 const hlog, U32 const mls)
U32 const hlog, U32 const stepSize, U32 const mls)
{
U32* hashTable = ms->hashTable;
const BYTE* const base = ms->window.base;
@@ -185,7 +186,8 @@ static size_t ZSTD_compressBlock_fast_extDict_generic(
} else {
if ( (matchIndex < lowestIndex) ||
(MEM_read32(match) != MEM_read32(ip)) ) {
ip += ((ip-anchor) >> kSearchStrength) + 1;
assert(stepSize >= 1);
ip += ((ip-anchor) >> kSearchStrength) + stepSize;
continue;
}
{ const BYTE* matchEnd = matchIndex < dictLimit ? dictEnd : iend;
@@ -241,16 +243,17 @@ size_t ZSTD_compressBlock_fast_extDict(
{
U32 const hlog = cParams->hashLog;
U32 const mls = cParams->searchLength;
U32 const stepSize = cParams->targetLength;
switch(mls)
{
default: /* includes case 3 */
case 4 :
return ZSTD_compressBlock_fast_extDict_generic(ms, seqStore, rep, src, srcSize, hlog, 4);
return ZSTD_compressBlock_fast_extDict_generic(ms, seqStore, rep, src, srcSize, hlog, stepSize, 4);
case 5 :
return ZSTD_compressBlock_fast_extDict_generic(ms, seqStore, rep, src, srcSize, hlog, 5);
return ZSTD_compressBlock_fast_extDict_generic(ms, seqStore, rep, src, srcSize, hlog, stepSize, 5);
case 6 :
return ZSTD_compressBlock_fast_extDict_generic(ms, seqStore, rep, src, srcSize, hlog, 6);
return ZSTD_compressBlock_fast_extDict_generic(ms, seqStore, rep, src, srcSize, hlog, stepSize, 6);
case 7 :
return ZSTD_compressBlock_fast_extDict_generic(ms, seqStore, rep, src, srcSize, hlog, 7);
return ZSTD_compressBlock_fast_extDict_generic(ms, seqStore, rep, src, srcSize, hlog, stepSize, 7);
}
}