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hc simplication

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This commit is contained in:
Yann Collet
2015-11-23 14:37:59 +01:00
parent 06eade5102
commit c1e52f0f05
1 changed files with 25 additions and 76 deletions
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101
lib/zstd_compress.c
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@@ -1206,78 +1206,11 @@ static U32 ZSTD_insertAndFindFirstIndex (ZSTD_CCtx* zc, const BYTE* ip, U32 mls)
FORCE_INLINE /* inlining is important to hardwire a hot branch (template emulation) */ FORCE_INLINE /* inlining is important to hardwire a hot branch (template emulation) */
size_t ZSTD_HcFindBestMatch ( size_t ZSTD_HcFindBestMatch_generic (
ZSTD_CCtx* zc, /* Index table will be updated */ ZSTD_CCtx* zc, /* Index table will be updated */
const BYTE* const ip, const BYTE* const iLimit, const BYTE* const ip, const BYTE* const iLimit,
size_t* offsetPtr, size_t* offsetPtr,
const U32 maxNbAttempts, const U32 matchLengthSearch) const U32 maxNbAttempts, const U32 mls, const U32 extDict)
{
const BYTE* const base = zc->base;
const U32 current = (U32)(ip-base);
U32* const chainTable = zc->contentTable;
const U32 chainSize = (1 << zc->params.contentLog);
const U32 minChain = current > chainSize ? current - chainSize : 0;
const U32 chainMask = chainSize-1;
const U32 lowLimit = zc->dictLimit; /* should be == zc->lowLimit, but safer to use this one if they are not, since dictLimit >= lowLimit */
U32 matchIndex;
const BYTE* match;
int nbAttempts=maxNbAttempts;
size_t ml=0;
/* HC4 match finder */
matchIndex = ZSTD_insertAndFindFirstIndex (zc, ip, matchLengthSearch);
while ((matchIndex>lowLimit) && (nbAttempts))
{
nbAttempts--;
match = base + matchIndex;
if (match[ml] == ip[ml]) /* potentially better */
{
const size_t mlt = ZSTD_count(ip, match, iLimit);
if (mlt > ml)
//if ( (4*(int)(mlt-ml)) > (int)(ZSTD_highbit(current-matchIndex+1) - ZSTD_highbit((U32)(*offsetPtr) + 1)) ) /* stronger but slower */
{
ml = mlt; *offsetPtr = ip-match;
if (ip+mlt >= iLimit) break; /* max ml possible; avoid risk of reading too far when testing ip[ml] */
}
}
if (matchIndex <= minChain) break;
matchIndex = NEXT_IN_CHAIN(matchIndex, chainMask);
}
return ml;
}
FORCE_INLINE /* inlining is important to hardwire a hot branch (template emulation) */
size_t ZSTD_HcFindBestMatch_extDict (
ZSTD_CCtx* zc, /* Index table will be updated */
const BYTE* const ip, const BYTE* const iLimit,
size_t* offsetPtr,
const U32 maxNbAttempts, const U32 matchLengthSearch);
FORCE_INLINE size_t ZSTD_HcFindBestMatch_selectMLS (
ZSTD_CCtx* zc, /* Index table will be updated */
const BYTE* ip, const BYTE* const iLimit,
size_t* offsetPtr,
const U32 maxNbAttempts, const U32 matchLengthSearch)
{
switch(matchLengthSearch)
{
default :
case 4 : return ZSTD_HcFindBestMatch(zc, ip, iLimit, offsetPtr, maxNbAttempts, 4);
case 5 : return ZSTD_HcFindBestMatch(zc, ip, iLimit, offsetPtr, maxNbAttempts, 5);
case 6 : return ZSTD_HcFindBestMatch(zc, ip, iLimit, offsetPtr, maxNbAttempts, 6);
}
}
FORCE_INLINE /* inlining is important to hardwire a hot branch (template emulation) */
size_t ZSTD_HcFindBestMatch_extDict (
ZSTD_CCtx* zc, /* Index table will be updated */
const BYTE* const ip, const BYTE* const iLimit,
size_t* offsetPtr,
const U32 maxNbAttempts, const U32 matchLengthSearch)
{ {
U32* const chainTable = zc->contentTable; U32* const chainTable = zc->contentTable;
const U32 chainSize = (1 << zc->params.contentLog); const U32 chainSize = (1 << zc->params.contentLog);
@@ -1296,13 +1229,13 @@ size_t ZSTD_HcFindBestMatch_extDict (
size_t ml=MINMATCH-1; size_t ml=MINMATCH-1;
/* HC4 match finder */ /* HC4 match finder */
matchIndex = ZSTD_insertAndFindFirstIndex (zc, ip, matchLengthSearch); matchIndex = ZSTD_insertAndFindFirstIndex (zc, ip, mls);
while ((matchIndex>lowLimit) && (nbAttempts)) while ((matchIndex>lowLimit) && (nbAttempts))
{ {
size_t currentMl=0; size_t currentMl=0;
nbAttempts--; nbAttempts--;
if (matchIndex >= dictLimit) if ((!extDict) || matchIndex >= dictLimit)
{ {
match = base + matchIndex; match = base + matchIndex;
if (match[ml] == ip[ml]) /* potentially better */ if (match[ml] == ip[ml]) /* potentially better */
@@ -1326,8 +1259,8 @@ size_t ZSTD_HcFindBestMatch_extDict (
} }
FORCE_INLINE size_t ZSTD_HcFindBestMatch_extDict_selectMLS ( FORCE_INLINE size_t ZSTD_HcFindBestMatch_selectMLS (
ZSTD_CCtx* zc, /* Index table will be updated */ ZSTD_CCtx* zc,
const BYTE* ip, const BYTE* const iLimit, const BYTE* ip, const BYTE* const iLimit,
size_t* offsetPtr, size_t* offsetPtr,
const U32 maxNbAttempts, const U32 matchLengthSearch) const U32 maxNbAttempts, const U32 matchLengthSearch)
@@ -1335,9 +1268,25 @@ FORCE_INLINE size_t ZSTD_HcFindBestMatch_extDict_selectMLS (
switch(matchLengthSearch) switch(matchLengthSearch)
{ {
default : default :
case 4 : return ZSTD_HcFindBestMatch_extDict(zc, ip, iLimit, offsetPtr, maxNbAttempts, 4); case 4 : return ZSTD_HcFindBestMatch_generic(zc, ip, iLimit, offsetPtr, maxNbAttempts, 4, 0);
case 5 : return ZSTD_HcFindBestMatch_extDict(zc, ip, iLimit, offsetPtr, maxNbAttempts, 5); case 5 : return ZSTD_HcFindBestMatch_generic(zc, ip, iLimit, offsetPtr, maxNbAttempts, 5, 0);
case 6 : return ZSTD_HcFindBestMatch_extDict(zc, ip, iLimit, offsetPtr, maxNbAttempts, 6); case 6 : return ZSTD_HcFindBestMatch_generic(zc, ip, iLimit, offsetPtr, maxNbAttempts, 6, 0);
}
}
FORCE_INLINE size_t ZSTD_HcFindBestMatch_extDict_selectMLS (
ZSTD_CCtx* zc,
const BYTE* ip, const BYTE* const iLimit,
size_t* offsetPtr,
const U32 maxNbAttempts, const U32 matchLengthSearch)
{
switch(matchLengthSearch)
{
default :
case 4 : return ZSTD_HcFindBestMatch_generic(zc, ip, iLimit, offsetPtr, maxNbAttempts, 4, 1);
case 5 : return ZSTD_HcFindBestMatch_generic(zc, ip, iLimit, offsetPtr, maxNbAttempts, 5, 1);
case 6 : return ZSTD_HcFindBestMatch_generic(zc, ip, iLimit, offsetPtr, maxNbAttempts, 6, 1);
} }
} }