Google Git
Sign in
fuchsia / third_party / cmake / refs/heads/main / . / Utilities / cmzstd / lib / compress / zstd_lazy.c
blob: 5ba88e8678fe36f96b55de8e7bba2c7292fccbfa [file] [log] [blame]
/*
* Copyright (c) Meta Platforms, Inc. and affiliates.
* All rights reserved.
*
* This source code is licensed under both the BSD-style license (found in the
* LICENSE file in the root directory of this source tree) and the GPLv2 (found
* in the COPYING file in the root directory of this source tree).
* You may select, at your option, one of the above-listed licenses.
*/
#include "zstd_compress_internal.h"
#include "zstd_lazy.h"
#include "../common/bits.h" /* ZSTD_countTrailingZeros64 */
#define kLazySkippingStep 8
/*-*************************************
* Binary Tree search
***************************************/
static void
ZSTD_updateDUBT(ZSTD_matchState_t* ms,
const BYTE* ip, const BYTE* iend,
U32 mls)
{
const ZSTD_compressionParameters* const cParams = &ms->cParams;
U32* const hashTable = ms->hashTable;
U32 const hashLog = cParams->hashLog;
U32* const bt = ms->chainTable;
U32 const btLog = cParams->chainLog - 1;
U32 const btMask = (1 << btLog) - 1;
const BYTE* const base = ms->window.base;
U32 const target = (U32)(ip - base);
U32 idx = ms->nextToUpdate;
if (idx != target)
DEBUGLOG(7, "ZSTD_updateDUBT, from %u to %u (dictLimit:%u)",
idx, target, ms->window.dictLimit);
assert(ip + 8 <= iend); /* condition for ZSTD_hashPtr */
(void)iend;
assert(idx >= ms->window.dictLimit); /* condition for valid base+idx */
for ( ; idx < target ; idx++) {
size_t const h = ZSTD_hashPtr(base + idx, hashLog, mls); /* assumption : ip + 8 <= iend */
U32 const matchIndex = hashTable[h];
U32* const nextCandidatePtr = bt + 2*(idx&btMask);
U32* const sortMarkPtr = nextCandidatePtr + 1;
DEBUGLOG(8, "ZSTD_updateDUBT: insert %u", idx);
hashTable[h] = idx; /* Update Hash Table */
*nextCandidatePtr = matchIndex; /* update BT like a chain */
*sortMarkPtr = ZSTD_DUBT_UNSORTED_MARK;
}
ms->nextToUpdate = target;
}
/** ZSTD_insertDUBT1() :
* sort one already inserted but unsorted position
* assumption : curr >= btlow == (curr - btmask)
* doesn't fail */
static void
ZSTD_insertDUBT1(const ZSTD_matchState_t* ms,
U32 curr, const BYTE* inputEnd,
U32 nbCompares, U32 btLow,
const ZSTD_dictMode_e dictMode)
{
const ZSTD_compressionParameters* const cParams = &ms->cParams;
U32* const bt = ms->chainTable;
U32 const btLog = cParams->chainLog - 1;
U32 const btMask = (1 << btLog) - 1;
size_t commonLengthSmaller=0, commonLengthLarger=0;
const BYTE* const base = ms->window.base;
const BYTE* const dictBase = ms->window.dictBase;
const U32 dictLimit = ms->window.dictLimit;
const BYTE* const ip = (curr>=dictLimit) ? base + curr : dictBase + curr;
const BYTE* const iend = (curr>=dictLimit) ? inputEnd : dictBase + dictLimit;
const BYTE* const dictEnd = dictBase + dictLimit;
const BYTE* const prefixStart = base + dictLimit;
const BYTE* match;
U32* smallerPtr = bt + 2*(curr&btMask);
U32* largerPtr = smallerPtr + 1;
U32 matchIndex = *smallerPtr; /* this candidate is unsorted : next sorted candidate is reached through *smallerPtr, while *largerPtr contains previous unsorted candidate (which is already saved and can be overwritten) */
U32 dummy32; /* to be nullified at the end */
U32 const windowValid = ms->window.lowLimit;
U32 const maxDistance = 1U << cParams->windowLog;
U32 const windowLow = (curr - windowValid > maxDistance) ? curr - maxDistance : windowValid;
DEBUGLOG(8, "ZSTD_insertDUBT1(%u) (dictLimit=%u, lowLimit=%u)",
curr, dictLimit, windowLow);
assert(curr >= btLow);
assert(ip < iend); /* condition for ZSTD_count */
for (; nbCompares && (matchIndex > windowLow); --nbCompares) {
U32* const nextPtr = bt + 2*(matchIndex & btMask);
size_t matchLength = MIN(commonLengthSmaller, commonLengthLarger); /* guaranteed minimum nb of common bytes */
assert(matchIndex < curr);
/* note : all candidates are now supposed sorted,
* but it's still possible to have nextPtr[1] == ZSTD_DUBT_UNSORTED_MARK
* when a real index has the same value as ZSTD_DUBT_UNSORTED_MARK */
if ( (dictMode != ZSTD_extDict)
|| (matchIndex+matchLength >= dictLimit) /* both in current segment*/
|| (curr < dictLimit) /* both in extDict */) {
const BYTE* const mBase = ( (dictMode != ZSTD_extDict)
|| (matchIndex+matchLength >= dictLimit)) ?
base : dictBase;
assert( (matchIndex+matchLength >= dictLimit) /* might be wrong if extDict is incorrectly set to 0 */
|| (curr < dictLimit) );
match = mBase + matchIndex;
matchLength += ZSTD_count(ip+matchLength, match+matchLength, iend);
} else {
match = dictBase + matchIndex;
matchLength += ZSTD_count_2segments(ip+matchLength, match+matchLength, iend, dictEnd, prefixStart);
if (matchIndex+matchLength >= dictLimit)
match = base + matchIndex; /* preparation for next read of match[matchLength] */
}
DEBUGLOG(8, "ZSTD_insertDUBT1: comparing %u with %u : found %u common bytes ",
curr, matchIndex, (U32)matchLength);
if (ip+matchLength == iend) { /* equal : no way to know if inf or sup */
break; /* drop , to guarantee consistency ; miss a bit of compression, but other solutions can corrupt tree */
}
if (match[matchLength] < ip[matchLength]) { /* necessarily within buffer */
/* match is smaller than current */
*smallerPtr = matchIndex; /* update smaller idx */
commonLengthSmaller = matchLength; /* all smaller will now have at least this guaranteed common length */
if (matchIndex <= btLow) { smallerPtr=&dummy32; break; } /* beyond tree size, stop searching */
DEBUGLOG(8, "ZSTD_insertDUBT1: %u (>btLow=%u) is smaller : next => %u",
matchIndex, btLow, nextPtr[1]);
smallerPtr = nextPtr+1; /* new "candidate" => larger than match, which was smaller than target */
matchIndex = nextPtr[1]; /* new matchIndex, larger than previous and closer to current */
} else {
/* match is larger than current */
*largerPtr = matchIndex;
commonLengthLarger = matchLength;
if (matchIndex <= btLow) { largerPtr=&dummy32; break; } /* beyond tree size, stop searching */
DEBUGLOG(8, "ZSTD_insertDUBT1: %u (>btLow=%u) is larger => %u",
matchIndex, btLow, nextPtr[0]);
largerPtr = nextPtr;
matchIndex = nextPtr[0];
} }
*smallerPtr = *largerPtr = 0;
}
static size_t
ZSTD_DUBT_findBetterDictMatch (
const ZSTD_matchState_t* ms,
const BYTE* const ip, const BYTE* const iend,
size_t* offsetPtr,
size_t bestLength,
U32 nbCompares,
U32 const mls,
const ZSTD_dictMode_e dictMode)
{
const ZSTD_matchState_t * const dms = ms->dictMatchState;
const ZSTD_compressionParameters* const dmsCParams = &dms->cParams;
const U32 * const dictHashTable = dms->hashTable;
U32 const hashLog = dmsCParams->hashLog;
size_t const h = ZSTD_hashPtr(ip, hashLog, mls);
U32 dictMatchIndex = dictHashTable[h];
const BYTE* const base = ms->window.base;
const BYTE* const prefixStart = base + ms->window.dictLimit;
U32 const curr = (U32)(ip-base);
const BYTE* const dictBase = dms->window.base;
const BYTE* const dictEnd = dms->window.nextSrc;
U32 const dictHighLimit = (U32)(dms->window.nextSrc - dms->window.base);
U32 const dictLowLimit = dms->window.lowLimit;
U32 const dictIndexDelta = ms->window.lowLimit - dictHighLimit;
U32* const dictBt = dms->chainTable;
U32 const btLog = dmsCParams->chainLog - 1;
U32 const btMask = (1 << btLog) - 1;
U32 const btLow = (btMask >= dictHighLimit - dictLowLimit) ? dictLowLimit : dictHighLimit - btMask;
size_t commonLengthSmaller=0, commonLengthLarger=0;
(void)dictMode;
assert(dictMode == ZSTD_dictMatchState);
for (; nbCompares && (dictMatchIndex > dictLowLimit); --nbCompares) {
U32* const nextPtr = dictBt + 2*(dictMatchIndex & btMask);
size_t matchLength = MIN(commonLengthSmaller, commonLengthLarger); /* guaranteed minimum nb of common bytes */
const BYTE* match = dictBase + dictMatchIndex;
matchLength += ZSTD_count_2segments(ip+matchLength, match+matchLength, iend, dictEnd, prefixStart);
if (dictMatchIndex+matchLength >= dictHighLimit)
match = base + dictMatchIndex + dictIndexDelta; /* to prepare for next usage of match[matchLength] */
if (matchLength > bestLength) {
U32 matchIndex = dictMatchIndex + dictIndexDelta;
if ( (4*(int)(matchLength-bestLength)) > (int)(ZSTD_highbit32(curr-matchIndex+1) - ZSTD_highbit32((U32)offsetPtr[0]+1)) ) {
DEBUGLOG(9, "ZSTD_DUBT_findBetterDictMatch(%u) : found better match length %u -> %u and offsetCode %u -> %u (dictMatchIndex %u, matchIndex %u)",
curr, (U32)bestLength, (U32)matchLength, (U32)*offsetPtr, OFFSET_TO_OFFBASE(curr - matchIndex), dictMatchIndex, matchIndex);
bestLength = matchLength, *offsetPtr = OFFSET_TO_OFFBASE(curr - matchIndex);
}
if (ip+matchLength == iend) { /* reached end of input : ip[matchLength] is not valid, no way to know if it's larger or smaller than match */
break; /* drop, to guarantee consistency (miss a little bit of compression) */
}
}
if (match[matchLength] < ip[matchLength]) {
if (dictMatchIndex <= btLow) { break; } /* beyond tree size, stop the search */
commonLengthSmaller = matchLength; /* all smaller will now have at least this guaranteed common length */
dictMatchIndex = nextPtr[1]; /* new matchIndex larger than previous (closer to current) */
} else {
/* match is larger than current */
if (dictMatchIndex <= btLow) { break; } /* beyond tree size, stop the search */
commonLengthLarger = matchLength;
dictMatchIndex = nextPtr[0];
}
}
if (bestLength >= MINMATCH) {
U32 const mIndex = curr - (U32)OFFBASE_TO_OFFSET(*offsetPtr); (void)mIndex;
DEBUGLOG(8, "ZSTD_DUBT_findBetterDictMatch(%u) : found match of length %u and offsetCode %u (pos %u)",
curr, (U32)bestLength, (U32)*offsetPtr, mIndex);
}
return bestLength;
}
static size_t
ZSTD_DUBT_findBestMatch(ZSTD_matchState_t* ms,
const BYTE* const ip, const BYTE* const iend,
size_t* offBasePtr,
U32 const mls,
const ZSTD_dictMode_e dictMode)
{
const ZSTD_compressionParameters* const cParams = &ms->cParams;
U32* const hashTable = ms->hashTable;
U32 const hashLog = cParams->hashLog;
size_t const h = ZSTD_hashPtr(ip, hashLog, mls);
U32 matchIndex = hashTable[h];
const BYTE* const base = ms->window.base;
U32 const curr = (U32)(ip-base);
U32 const windowLow = ZSTD_getLowestMatchIndex(ms, curr, cParams->windowLog);
U32* const bt = ms->chainTable;
U32 const btLog = cParams->chainLog - 1;
U32 const btMask = (1 << btLog) - 1;
U32 const btLow = (btMask >= curr) ? 0 : curr - btMask;
U32 const unsortLimit = MAX(btLow, windowLow);
U32* nextCandidate = bt + 2*(matchIndex&btMask);
U32* unsortedMark = bt + 2*(matchIndex&btMask) + 1;
U32 nbCompares = 1U << cParams->searchLog;
U32 nbCandidates = nbCompares;
U32 previousCandidate = 0;
DEBUGLOG(7, "ZSTD_DUBT_findBestMatch (%u) ", curr);
assert(ip <= iend-8); /* required for h calculation */
assert(dictMode != ZSTD_dedicatedDictSearch);
/* reach end of unsorted candidates list */
while ( (matchIndex > unsortLimit)
&& (*unsortedMark == ZSTD_DUBT_UNSORTED_MARK)
&& (nbCandidates > 1) ) {
DEBUGLOG(8, "ZSTD_DUBT_findBestMatch: candidate %u is unsorted",
matchIndex);
*unsortedMark = previousCandidate; /* the unsortedMark becomes a reversed chain, to move up back to original position */
previousCandidate = matchIndex;
matchIndex = *nextCandidate;
nextCandidate = bt + 2*(matchIndex&btMask);
unsortedMark = bt + 2*(matchIndex&btMask) + 1;
nbCandidates --;
}
/* nullify last candidate if it's still unsorted
* simplification, detrimental to compression ratio, beneficial for speed */
if ( (matchIndex > unsortLimit)
&& (*unsortedMark==ZSTD_DUBT_UNSORTED_MARK) ) {
DEBUGLOG(7, "ZSTD_DUBT_findBestMatch: nullify last unsorted candidate %u",
matchIndex);
*nextCandidate = *unsortedMark = 0;
}
/* batch sort stacked candidates */
matchIndex = previousCandidate;
while (matchIndex) { /* will end on matchIndex == 0 */
U32* const nextCandidateIdxPtr = bt + 2*(matchIndex&btMask) + 1;
U32 const nextCandidateIdx = *nextCandidateIdxPtr;
ZSTD_insertDUBT1(ms, matchIndex, iend,
nbCandidates, unsortLimit, dictMode);
matchIndex = nextCandidateIdx;
nbCandidates++;
}
/* find longest match */
{ size_t commonLengthSmaller = 0, commonLengthLarger = 0;
const BYTE* const dictBase = ms->window.dictBase;
const U32 dictLimit = ms->window.dictLimit;
const BYTE* const dictEnd = dictBase + dictLimit;
const BYTE* const prefixStart = base + dictLimit;
U32* smallerPtr = bt + 2*(curr&btMask);
U32* largerPtr = bt + 2*(curr&btMask) + 1;
U32 matchEndIdx = curr + 8 + 1;
U32 dummy32; /* to be nullified at the end */
size_t bestLength = 0;
matchIndex = hashTable[h];
hashTable[h] = curr; /* Update Hash Table */
for (; nbCompares && (matchIndex > windowLow); --nbCompares) {
U32* const nextPtr = bt + 2*(matchIndex & btMask);
size_t matchLength = MIN(commonLengthSmaller, commonLengthLarger); /* guaranteed minimum nb of common bytes */
const BYTE* match;
if ((dictMode != ZSTD_extDict) || (matchIndex+matchLength >= dictLimit)) {
match = base + matchIndex;
matchLength += ZSTD_count(ip+matchLength, match+matchLength, iend);
} else {
match = dictBase + matchIndex;
matchLength += ZSTD_count_2segments(ip+matchLength, match+matchLength, iend, dictEnd, prefixStart);
if (matchIndex+matchLength >= dictLimit)
match = base + matchIndex; /* to prepare for next usage of match[matchLength] */
}
if (matchLength > bestLength) {
if (matchLength > matchEndIdx - matchIndex)
matchEndIdx = matchIndex + (U32)matchLength;
if ( (4*(int)(matchLength-bestLength)) > (int)(ZSTD_highbit32(curr - matchIndex + 1) - ZSTD_highbit32((U32)*offBasePtr)) )
bestLength = matchLength, *offBasePtr = OFFSET_TO_OFFBASE(curr - matchIndex);
if (ip+matchLength == iend) { /* equal : no way to know if inf or sup */
if (dictMode == ZSTD_dictMatchState) {
nbCompares = 0; /* in addition to avoiding checking any
* further in this loop, make sure we
* skip checking in the dictionary. */
}
break; /* drop, to guarantee consistency (miss a little bit of compression) */
}
}
if (match[matchLength] < ip[matchLength]) {
/* match is smaller than current */
*smallerPtr = matchIndex; /* update smaller idx */
commonLengthSmaller = matchLength; /* all smaller will now have at least this guaranteed common length */
if (matchIndex <= btLow) { smallerPtr=&dummy32; break; } /* beyond tree size, stop the search */
smallerPtr = nextPtr+1; /* new "smaller" => larger of match */
matchIndex = nextPtr[1]; /* new matchIndex larger than previous (closer to current) */
} else {
/* match is larger than current */
*largerPtr = matchIndex;
commonLengthLarger = matchLength;
if (matchIndex <= btLow) { largerPtr=&dummy32; break; } /* beyond tree size, stop the search */
largerPtr = nextPtr;
matchIndex = nextPtr[0];
} }
*smallerPtr = *largerPtr = 0;
assert(nbCompares <= (1U << ZSTD_SEARCHLOG_MAX)); /* Check we haven't underflowed. */
if (dictMode == ZSTD_dictMatchState && nbCompares) {
bestLength = ZSTD_DUBT_findBetterDictMatch(
ms, ip, iend,
offBasePtr, bestLength, nbCompares,
mls, dictMode);
}
assert(matchEndIdx > curr+8); /* ensure nextToUpdate is increased */
ms->nextToUpdate = matchEndIdx - 8; /* skip repetitive patterns */
if (bestLength >= MINMATCH) {
U32 const mIndex = curr - (U32)OFFBASE_TO_OFFSET(*offBasePtr); (void)mIndex;
DEBUGLOG(8, "ZSTD_DUBT_findBestMatch(%u) : found match of length %u and offsetCode %u (pos %u)",
curr, (U32)bestLength, (U32)*offBasePtr, mIndex);
}
return bestLength;
}
}
/** ZSTD_BtFindBestMatch() : Tree updater, providing best match */
FORCE_INLINE_TEMPLATE size_t
ZSTD_BtFindBestMatch( ZSTD_matchState_t* ms,
const BYTE* const ip, const BYTE* const iLimit,
size_t* offBasePtr,
const U32 mls /* template */,
const ZSTD_dictMode_e dictMode)
{
DEBUGLOG(7, "ZSTD_BtFindBestMatch");
if (ip < ms->window.base + ms->nextToUpdate) return 0; /* skipped area */
ZSTD_updateDUBT(ms, ip, iLimit, mls);
return ZSTD_DUBT_findBestMatch(ms, ip, iLimit, offBasePtr, mls, dictMode);
}
/***********************************
* Dedicated dict search
***********************************/
void ZSTD_dedicatedDictSearch_lazy_loadDictionary(ZSTD_matchState_t* ms, const BYTE* const ip)
{
const BYTE* const base = ms->window.base;
U32 const target = (U32)(ip - base);
U32* const hashTable = ms->hashTable;
U32* const chainTable = ms->chainTable;
U32 const chainSize = 1 << ms->cParams.chainLog;
U32 idx = ms->nextToUpdate;
U32 const minChain = chainSize < target - idx ? target - chainSize : idx;
U32 const bucketSize = 1 << ZSTD_LAZY_DDSS_BUCKET_LOG;
U32 const cacheSize = bucketSize - 1;
U32 const chainAttempts = (1 << ms->cParams.searchLog) - cacheSize;
U32 const chainLimit = chainAttempts > 255 ? 255 : chainAttempts;
/* We know the hashtable is oversized by a factor of `bucketSize`.
* We are going to temporarily pretend `bucketSize == 1`, keeping only a
* single entry. We will use the rest of the space to construct a temporary
* chaintable.
*/
U32 const hashLog = ms->cParams.hashLog - ZSTD_LAZY_DDSS_BUCKET_LOG;
U32* const tmpHashTable = hashTable;
U32* const tmpChainTable = hashTable + ((size_t)1 << hashLog);
U32 const tmpChainSize = (U32)((1 << ZSTD_LAZY_DDSS_BUCKET_LOG) - 1) << hashLog;
U32 const tmpMinChain = tmpChainSize < target ? target - tmpChainSize : idx;
U32 hashIdx;
assert(ms->cParams.chainLog <= 24);
assert(ms->cParams.hashLog > ms->cParams.chainLog);
assert(idx != 0);
assert(tmpMinChain <= minChain);
/* fill conventional hash table and conventional chain table */
for ( ; idx < target; idx++) {
U32 const h = (U32)ZSTD_hashPtr(base + idx, hashLog, ms->cParams.minMatch);
if (idx >= tmpMinChain) {
tmpChainTable[idx - tmpMinChain] = hashTable[h];
}
tmpHashTable[h] = idx;
}
/* sort chains into ddss chain table */
{
U32 chainPos = 0;
for (hashIdx = 0; hashIdx < (1U << hashLog); hashIdx++) {
U32 count;
U32 countBeyondMinChain = 0;
U32 i = tmpHashTable[hashIdx];
for (count = 0; i >= tmpMinChain && count < cacheSize; count++) {
/* skip through the chain to the first position that won't be
* in the hash cache bucket */
if (i < minChain) {
countBeyondMinChain++;
}
i = tmpChainTable[i - tmpMinChain];
}
if (count == cacheSize) {
for (count = 0; count < chainLimit;) {
if (i < minChain) {
if (!i || ++countBeyondMinChain > cacheSize) {
/* only allow pulling `cacheSize` number of entries
* into the cache or chainTable beyond `minChain`,
* to replace the entries pulled out of the
* chainTable into the cache. This lets us reach
* back further without increasing the total number
* of entries in the chainTable, guaranteeing the
* DDSS chain table will fit into the space
* allocated for the regular one. */
break;
}
}
chainTable[chainPos++] = i;
count++;
if (i < tmpMinChain) {
break;
}
i = tmpChainTable[i - tmpMinChain];
}
} else {
count = 0;
}
if (count) {
tmpHashTable[hashIdx] = ((chainPos - count) << 8) + count;
} else {
tmpHashTable[hashIdx] = 0;
}
}
assert(chainPos <= chainSize); /* I believe this is guaranteed... */
}
/* move chain pointers into the last entry of each hash bucket */
for (hashIdx = (1 << hashLog); hashIdx; ) {
U32 const bucketIdx = --hashIdx << ZSTD_LAZY_DDSS_BUCKET_LOG;
U32 const chainPackedPointer = tmpHashTable[hashIdx];
U32 i;
for (i = 0; i < cacheSize; i++) {
hashTable[bucketIdx + i] = 0;
}
hashTable[bucketIdx + bucketSize - 1] = chainPackedPointer;
}
/* fill the buckets of the hash table */
for (idx = ms->nextToUpdate; idx < target; idx++) {
U32 const h = (U32)ZSTD_hashPtr(base + idx, hashLog, ms->cParams.minMatch)
<< ZSTD_LAZY_DDSS_BUCKET_LOG;
U32 i;
/* Shift hash cache down 1. */
for (i = cacheSize - 1; i; i--)
hashTable[h + i] = hashTable[h + i - 1];
hashTable[h] = idx;
}
ms->nextToUpdate = target;
}
/* Returns the longest match length found in the dedicated dict search structure.
* If none are longer than the argument ml, then ml will be returned.
*/
FORCE_INLINE_TEMPLATE
size_t ZSTD_dedicatedDictSearch_lazy_search(size_t* offsetPtr, size_t ml, U32 nbAttempts,
const ZSTD_matchState_t* const dms,
const BYTE* const ip, const BYTE* const iLimit,
const BYTE* const prefixStart, const U32 curr,
const U32 dictLimit, const size_t ddsIdx) {
const U32 ddsLowestIndex = dms->window.dictLimit;
const BYTE* const ddsBase = dms->window.base;
const BYTE* const ddsEnd = dms->window.nextSrc;
const U32 ddsSize = (U32)(ddsEnd - ddsBase);
const U32 ddsIndexDelta = dictLimit - ddsSize;
const U32 bucketSize = (1 << ZSTD_LAZY_DDSS_BUCKET_LOG);
const U32 bucketLimit = nbAttempts < bucketSize - 1 ? nbAttempts : bucketSize - 1;
U32 ddsAttempt;
U32 matchIndex;
for (ddsAttempt = 0; ddsAttempt < bucketSize - 1; ddsAttempt++) {
PREFETCH_L1(ddsBase + dms->hashTable[ddsIdx + ddsAttempt]);
}
{
U32 const chainPackedPointer = dms->hashTable[ddsIdx + bucketSize - 1];
U32 const chainIndex = chainPackedPointer >> 8;
PREFETCH_L1(&dms->chainTable[chainIndex]);
}
for (ddsAttempt = 0; ddsAttempt < bucketLimit; ddsAttempt++) {
size_t currentMl=0;
const BYTE* match;
matchIndex = dms->hashTable[ddsIdx + ddsAttempt];
match = ddsBase + matchIndex;
if (!matchIndex) {
return ml;
}
/* guaranteed by table construction */
(void)ddsLowestIndex;
assert(matchIndex >= ddsLowestIndex);
assert(match+4 <= ddsEnd);
if (MEM_read32(match) == MEM_read32(ip)) {
/* assumption : matchIndex <= dictLimit-4 (by table construction) */
currentMl = ZSTD_count_2segments(ip+4, match+4, iLimit, ddsEnd, prefixStart) + 4;
}
/* save best solution */
if (currentMl > ml) {
ml = currentMl;
*offsetPtr = OFFSET_TO_OFFBASE(curr - (matchIndex + ddsIndexDelta));
if (ip+currentMl == iLimit) {
/* best possible, avoids read overflow on next attempt */
return ml;
}
}
}
{
U32 const chainPackedPointer = dms->hashTable[ddsIdx + bucketSize - 1];
U32 chainIndex = chainPackedPointer >> 8;
U32 const chainLength = chainPackedPointer & 0xFF;
U32 const chainAttempts = nbAttempts - ddsAttempt;
U32 const chainLimit = chainAttempts > chainLength ? chainLength : chainAttempts;
U32 chainAttempt;
for (chainAttempt = 0 ; chainAttempt < chainLimit; chainAttempt++) {
PREFETCH_L1(ddsBase + dms->chainTable[chainIndex + chainAttempt]);
}
for (chainAttempt = 0 ; chainAttempt < chainLimit; chainAttempt++, chainIndex++) {
size_t currentMl=0;
const BYTE* match;
matchIndex = dms->chainTable[chainIndex];
match = ddsBase + matchIndex;
/* guaranteed by table construction */
assert(matchIndex >= ddsLowestIndex);
assert(match+4 <= ddsEnd);
if (MEM_read32(match) == MEM_read32(ip)) {
/* assumption : matchIndex <= dictLimit-4 (by table construction) */
currentMl = ZSTD_count_2segments(ip+4, match+4, iLimit, ddsEnd, prefixStart) + 4;
}
/* save best solution */
if (currentMl > ml) {
ml = currentMl;
*offsetPtr = OFFSET_TO_OFFBASE(curr - (matchIndex + ddsIndexDelta));
if (ip+currentMl == iLimit) break; /* best possible, avoids read overflow on next attempt */
}
}
}
return ml;
}
/* *********************************
* Hash Chain
***********************************/
#define NEXT_IN_CHAIN(d, mask) chainTable[(d) & (mask)]
/* Update chains up to ip (excluded)
Assumption : always within prefix (i.e. not within extDict) */
FORCE_INLINE_TEMPLATE U32 ZSTD_insertAndFindFirstIndex_internal(
ZSTD_matchState_t* ms,
const ZSTD_compressionParameters* const cParams,
const BYTE* ip, U32 const mls, U32 const lazySkipping)
{
U32* const hashTable = ms->hashTable;
const U32 hashLog = cParams->hashLog;
U32* const chainTable = ms->chainTable;
const U32 chainMask = (1 << cParams->chainLog) - 1;
const BYTE* const base = ms->window.base;
const U32 target = (U32)(ip - base);
U32 idx = ms->nextToUpdate;
while(idx < target) { /* catch up */
size_t const h = ZSTD_hashPtr(base+idx, hashLog, mls);
NEXT_IN_CHAIN(idx, chainMask) = hashTable[h];
hashTable[h] = idx;
idx++;
/* Stop inserting every position when in the lazy skipping mode. */
if (lazySkipping)
break;
}
ms->nextToUpdate = target;
return hashTable[ZSTD_hashPtr(ip, hashLog, mls)];
}
U32 ZSTD_insertAndFindFirstIndex(ZSTD_matchState_t* ms, const BYTE* ip) {
const ZSTD_compressionParameters* const cParams = &ms->cParams;
return ZSTD_insertAndFindFirstIndex_internal(ms, cParams, ip, ms->cParams.minMatch, /* lazySkipping*/ 0);
}
/* inlining is important to hardwire a hot branch (template emulation) */
FORCE_INLINE_TEMPLATE
size_t ZSTD_HcFindBestMatch(
ZSTD_matchState_t* ms,
const BYTE* const ip, const BYTE* const iLimit,
size_t* offsetPtr,
const U32 mls, const ZSTD_dictMode_e dictMode)
{
const ZSTD_compressionParameters* const cParams = &ms->cParams;
U32* const chainTable = ms->chainTable;
const U32 chainSize = (1 << cParams->chainLog);
const U32 chainMask = chainSize-1;
const BYTE* const base = ms->window.base;
const BYTE* const dictBase = ms->window.dictBase;
const U32 dictLimit = ms->window.dictLimit;
const BYTE* const prefixStart = base + dictLimit;
const BYTE* const dictEnd = dictBase + dictLimit;
const U32 curr = (U32)(ip-base);
const U32 maxDistance = 1U << cParams->windowLog;
const U32 lowestValid = ms->window.lowLimit;
const U32 withinMaxDistance = (curr - lowestValid > maxDistance) ? curr - maxDistance : lowestValid;
const U32 isDictionary = (ms->loadedDictEnd != 0);
const U32 lowLimit = isDictionary ? lowestValid : withinMaxDistance;
const U32 minChain = curr > chainSize ? curr - chainSize : 0;
U32 nbAttempts = 1U << cParams->searchLog;
size_t ml=4-1;
const ZSTD_matchState_t* const dms = ms->dictMatchState;
const U32 ddsHashLog = dictMode == ZSTD_dedicatedDictSearch
? dms->cParams.hashLog - ZSTD_LAZY_DDSS_BUCKET_LOG : 0;
const size_t ddsIdx = dictMode == ZSTD_dedicatedDictSearch
? ZSTD_hashPtr(ip, ddsHashLog, mls) << ZSTD_LAZY_DDSS_BUCKET_LOG : 0;
U32 matchIndex;
if (dictMode == ZSTD_dedicatedDictSearch) {
const U32* entry = &dms->hashTable[ddsIdx];
PREFETCH_L1(entry);
}
/* HC4 match finder */
matchIndex = ZSTD_insertAndFindFirstIndex_internal(ms, cParams, ip, mls, ms->lazySkipping);
for ( ; (matchIndex>=lowLimit) & (nbAttempts>0) ; nbAttempts--) {
size_t currentMl=0;
if ((dictMode != ZSTD_extDict) || matchIndex >= dictLimit) {
const BYTE* const match = base + matchIndex;
assert(matchIndex >= dictLimit); /* ensures this is true if dictMode != ZSTD_extDict */
/* read 4B starting from (match + ml + 1 - sizeof(U32)) */
if (MEM_read32(match + ml - 3) == MEM_read32(ip + ml - 3)) /* potentially better */
currentMl = ZSTD_count(ip, match, iLimit);
} else {
const BYTE* const match = dictBase + matchIndex;
assert(match+4 <= dictEnd);
if (MEM_read32(match) == MEM_read32(ip)) /* assumption : matchIndex <= dictLimit-4 (by table construction) */
currentMl = ZSTD_count_2segments(ip+4, match+4, iLimit, dictEnd, prefixStart) + 4;
}
/* save best solution */
if (currentMl > ml) {
ml = currentMl;
*offsetPtr = OFFSET_TO_OFFBASE(curr - matchIndex);
if (ip+currentMl == iLimit) break; /* best possible, avoids read overflow on next attempt */
}
if (matchIndex <= minChain) break;
matchIndex = NEXT_IN_CHAIN(matchIndex, chainMask);
}
assert(nbAttempts <= (1U << ZSTD_SEARCHLOG_MAX)); /* Check we haven't underflowed. */
if (dictMode == ZSTD_dedicatedDictSearch) {
ml = ZSTD_dedicatedDictSearch_lazy_search(offsetPtr, ml, nbAttempts, dms,
ip, iLimit, prefixStart, curr, dictLimit, ddsIdx);
} else if (dictMode == ZSTD_dictMatchState) {
const U32* const dmsChainTable = dms->chainTable;
const U32 dmsChainSize = (1 << dms->cParams.chainLog);
const U32 dmsChainMask = dmsChainSize - 1;
const U32 dmsLowestIndex = dms->window.dictLimit;
const BYTE* const dmsBase = dms->window.base;
const BYTE* const dmsEnd = dms->window.nextSrc;
const U32 dmsSize = (U32)(dmsEnd - dmsBase);
const U32 dmsIndexDelta = dictLimit - dmsSize;
const U32 dmsMinChain = dmsSize > dmsChainSize ? dmsSize - dmsChainSize : 0;
matchIndex = dms->hashTable[ZSTD_hashPtr(ip, dms->cParams.hashLog, mls)];
for ( ; (matchIndex>=dmsLowestIndex) & (nbAttempts>0) ; nbAttempts--) {
size_t currentMl=0;
const BYTE* const match = dmsBase + matchIndex;
assert(match+4 <= dmsEnd);
if (MEM_read32(match) == MEM_read32(ip)) /* assumption : matchIndex <= dictLimit-4 (by table construction) */
currentMl = ZSTD_count_2segments(ip+4, match+4, iLimit, dmsEnd, prefixStart) + 4;
/* save best solution */
if (currentMl > ml) {
ml = currentMl;
assert(curr > matchIndex + dmsIndexDelta);
*offsetPtr = OFFSET_TO_OFFBASE(curr - (matchIndex + dmsIndexDelta));
if (ip+currentMl == iLimit) break; /* best possible, avoids read overflow on next attempt */
}
if (matchIndex <= dmsMinChain) break;
matchIndex = dmsChainTable[matchIndex & dmsChainMask];
}
}
return ml;
}
/* *********************************
* (SIMD) Row-based matchfinder
***********************************/
/* Constants for row-based hash */
#define ZSTD_ROW_HASH_TAG_MASK ((1u << ZSTD_ROW_HASH_TAG_BITS) - 1)
#define ZSTD_ROW_HASH_MAX_ENTRIES 64 /* absolute maximum number of entries per row, for all configurations */
#define ZSTD_ROW_HASH_CACHE_MASK (ZSTD_ROW_HASH_CACHE_SIZE - 1)
typedef U64 ZSTD_VecMask; /* Clarifies when we are interacting with a U64 representing a mask of matches */
/* ZSTD_VecMask_next():
* Starting from the LSB, returns the idx of the next non-zero bit.
* Basically counting the nb of trailing zeroes.
*/
MEM_STATIC U32 ZSTD_VecMask_next(ZSTD_VecMask val) {
return ZSTD_countTrailingZeros64(val);
}
/* ZSTD_row_nextIndex():
* Returns the next index to insert at within a tagTable row, and updates the "head"
* value to reflect the update. Essentially cycles backwards from [1, {entries per row})
*/
FORCE_INLINE_TEMPLATE U32 ZSTD_row_nextIndex(BYTE* const tagRow, U32 const rowMask) {
U32 next = (*tagRow-1) & rowMask;
next += (next == 0) ? rowMask : 0; /* skip first position */
*tagRow = (BYTE)next;
return next;
}
/* ZSTD_isAligned():
* Checks that a pointer is aligned to "align" bytes which must be a power of 2.
*/
MEM_STATIC int ZSTD_isAligned(void const* ptr, size_t align) {
assert((align & (align - 1)) == 0);
return (((size_t)ptr) & (align - 1)) == 0;
}
/* ZSTD_row_prefetch():
* Performs prefetching for the hashTable and tagTable at a given row.
*/
FORCE_INLINE_TEMPLATE void ZSTD_row_prefetch(U32 const* hashTable, BYTE const* tagTable, U32 const relRow, U32 const rowLog) {
PREFETCH_L1(hashTable + relRow);
if (rowLog >= 5) {
PREFETCH_L1(hashTable + relRow + 16);
/* Note: prefetching more of the hash table does not appear to be beneficial for 128-entry rows */
}
PREFETCH_L1(tagTable + relRow);
if (rowLog == 6) {
PREFETCH_L1(tagTable + relRow + 32);
}
assert(rowLog == 4 || rowLog == 5 || rowLog == 6);
assert(ZSTD_isAligned(hashTable + relRow, 64)); /* prefetched hash row always 64-byte aligned */
assert(ZSTD_isAligned(tagTable + relRow, (size_t)1 << rowLog)); /* prefetched tagRow sits on correct multiple of bytes (32,64,128) */
}
/* ZSTD_row_fillHashCache():
* Fill up the hash cache starting at idx, prefetching up to ZSTD_ROW_HASH_CACHE_SIZE entries,
* but not beyond iLimit.
*/
FORCE_INLINE_TEMPLATE void ZSTD_row_fillHashCache(ZSTD_matchState_t* ms, const BYTE* base,
U32 const rowLog, U32 const mls,
U32 idx, const BYTE* const iLimit)
{
U32 const* const hashTable = ms->hashTable;
BYTE const* const tagTable = ms->tagTable;
U32 const hashLog = ms->rowHashLog;
U32 const maxElemsToPrefetch = (base + idx) > iLimit ? 0 : (U32)(iLimit - (base + idx) + 1);
U32 const lim = idx + MIN(ZSTD_ROW_HASH_CACHE_SIZE, maxElemsToPrefetch);
for (; idx < lim; ++idx) {
U32 const hash = (U32)ZSTD_hashPtrSalted(base + idx, hashLog + ZSTD_ROW_HASH_TAG_BITS, mls, ms->hashSalt);
U32 const row = (hash >> ZSTD_ROW_HASH_TAG_BITS) << rowLog;
ZSTD_row_prefetch(hashTable, tagTable, row, rowLog);
ms->hashCache[idx & ZSTD_ROW_HASH_CACHE_MASK] = hash;
}
DEBUGLOG(6, "ZSTD_row_fillHashCache(): [%u %u %u %u %u %u %u %u]", ms->hashCache[0], ms->hashCache[1],
ms->hashCache[2], ms->hashCache[3], ms->hashCache[4],
ms->hashCache[5], ms->hashCache[6], ms->hashCache[7]);
}
/* ZSTD_row_nextCachedHash():
* Returns the hash of base + idx, and replaces the hash in the hash cache with the byte at
* base + idx + ZSTD_ROW_HASH_CACHE_SIZE. Also prefetches the appropriate rows from hashTable and tagTable.
*/
FORCE_INLINE_TEMPLATE U32 ZSTD_row_nextCachedHash(U32* cache, U32 const* hashTable,
BYTE const* tagTable, BYTE const* base,
U32 idx, U32 const hashLog,
U32 const rowLog, U32 const mls,
U64 const hashSalt)
{
U32 const newHash = (U32)ZSTD_hashPtrSalted(base+idx+ZSTD_ROW_HASH_CACHE_SIZE, hashLog + ZSTD_ROW_HASH_TAG_BITS, mls, hashSalt);
U32 const row = (newHash >> ZSTD_ROW_HASH_TAG_BITS) << rowLog;
ZSTD_row_prefetch(hashTable, tagTable, row, rowLog);
{ U32 const hash = cache[idx & ZSTD_ROW_HASH_CACHE_MASK];
cache[idx & ZSTD_ROW_HASH_CACHE_MASK] = newHash;
return hash;
}
}
/* ZSTD_row_update_internalImpl():
* Updates the hash table with positions starting from updateStartIdx until updateEndIdx.
*/
FORCE_INLINE_TEMPLATE void ZSTD_row_update_internalImpl(ZSTD_matchState_t* ms,
U32 updateStartIdx, U32 const updateEndIdx,
U32 const mls, U32 const rowLog,
U32 const rowMask, U32 const useCache)
{
U32* const hashTable = ms->hashTable;
BYTE* const tagTable = ms->tagTable;
U32 const hashLog = ms->rowHashLog;
const BYTE* const base = ms->window.base;
DEBUGLOG(6, "ZSTD_row_update_internalImpl(): updateStartIdx=%u, updateEndIdx=%u", updateStartIdx, updateEndIdx);
for (; updateStartIdx < updateEndIdx; ++updateStartIdx) {
U32 const hash = useCache ? ZSTD_row_nextCachedHash(ms->hashCache, hashTable, tagTable, base, updateStartIdx, hashLog, rowLog, mls, ms->hashSalt)
: (U32)ZSTD_hashPtrSalted(base + updateStartIdx, hashLog + ZSTD_ROW_HASH_TAG_BITS, mls, ms->hashSalt);
U32 const relRow = (hash >> ZSTD_ROW_HASH_TAG_BITS) << rowLog;
U32* const row = hashTable + relRow;
BYTE* tagRow = tagTable + relRow;
U32 const pos = ZSTD_row_nextIndex(tagRow, rowMask);
assert(hash == ZSTD_hashPtrSalted(base + updateStartIdx, hashLog + ZSTD_ROW_HASH_TAG_BITS, mls, ms->hashSalt));
tagRow[pos] = hash & ZSTD_ROW_HASH_TAG_MASK;
row[pos] = updateStartIdx;
}
}
/* ZSTD_row_update_internal():
* Inserts the byte at ip into the appropriate position in the hash table, and updates ms->nextToUpdate.
* Skips sections of long matches as is necessary.
*/
FORCE_INLINE_TEMPLATE void ZSTD_row_update_internal(ZSTD_matchState_t* ms, const BYTE* ip,
U32 const mls, U32 const rowLog,
U32 const rowMask, U32 const useCache)
{
U32 idx = ms->nextToUpdate;
const BYTE* const base = ms->window.base;
const U32 target = (U32)(ip - base);
const U32 kSkipThreshold = 384;
const U32 kMaxMatchStartPositionsToUpdate = 96;
const U32 kMaxMatchEndPositionsToUpdate = 32;
if (useCache) {
/* Only skip positions when using hash cache, i.e.
* if we are loading a dict, don't skip anything.
* If we decide to skip, then we only update a set number
* of positions at the beginning and end of the match.
*/
if (UNLIKELY(target - idx > kSkipThreshold)) {
U32 const bound = idx + kMaxMatchStartPositionsToUpdate;
ZSTD_row_update_internalImpl(ms, idx, bound, mls, rowLog, rowMask, useCache);
idx = target - kMaxMatchEndPositionsToUpdate;
ZSTD_row_fillHashCache(ms, base, rowLog, mls, idx, ip+1);
}
}
assert(target >= idx);
ZSTD_row_update_internalImpl(ms, idx, target, mls, rowLog, rowMask, useCache);
ms->nextToUpdate = target;
}
/* ZSTD_row_update():
* External wrapper for ZSTD_row_update_internal(). Used for filling the hashtable during dictionary
* processing.
*/
void ZSTD_row_update(ZSTD_matchState_t* const ms, const BYTE* ip) {
const U32 rowLog = BOUNDED(4, ms->cParams.searchLog, 6);
const U32 rowMask = (1u << rowLog) - 1;
const U32 mls = MIN(ms->cParams.minMatch, 6 /* mls caps out at 6 */);
DEBUGLOG(5, "ZSTD_row_update(), rowLog=%u", rowLog);
ZSTD_row_update_internal(ms, ip, mls, rowLog, rowMask, 0 /* don't use cache */);
}
/* Returns the mask width of bits group of which will be set to 1. Given not all
* architectures have easy movemask instruction, this helps to iterate over
* groups of bits easier and faster.
*/
FORCE_INLINE_TEMPLATE U32
ZSTD_row_matchMaskGroupWidth(const U32 rowEntries)
{
assert((rowEntries == 16) || (rowEntries == 32) || rowEntries == 64);
assert(rowEntries <= ZSTD_ROW_HASH_MAX_ENTRIES);
(void)rowEntries;
#if defined(ZSTD_ARCH_ARM_NEON)
/* NEON path only works for little endian */
if (!MEM_isLittleEndian()) {
return 1;
}
if (rowEntries == 16) {
return 4;
}
if (rowEntries == 32) {
return 2;
}
if (rowEntries == 64) {
return 1;
}
#endif
return 1;
}
#if defined(ZSTD_ARCH_X86_SSE2)
FORCE_INLINE_TEMPLATE ZSTD_VecMask
ZSTD_row_getSSEMask(int nbChunks, const BYTE* const src, const BYTE tag, const U32 head)
{
const __m128i comparisonMask = _mm_set1_epi8((char)tag);
int matches[4] = {0};
int i;
assert(nbChunks == 1 || nbChunks == 2 || nbChunks == 4);
for (i=0; i<nbChunks; i++) {
const __m128i chunk = _mm_loadu_si128((const __m128i*)(const void*)(src + 16*i));
const __m128i equalMask = _mm_cmpeq_epi8(chunk, comparisonMask);
matches[i] = _mm_movemask_epi8(equalMask);
}
if (nbChunks == 1) return ZSTD_rotateRight_U16((U16)matches[0], head);
if (nbChunks == 2) return ZSTD_rotateRight_U32((U32)matches[1] << 16 | (U32)matches[0], head);
assert(nbChunks == 4);
return ZSTD_rotateRight_U64((U64)matches[3] << 48 | (U64)matches[2] << 32 | (U64)matches[1] << 16 | (U64)matches[0], head);
}
#endif
#if defined(ZSTD_ARCH_ARM_NEON)
FORCE_INLINE_TEMPLATE ZSTD_VecMask
ZSTD_row_getNEONMask(const U32 rowEntries, const BYTE* const src, const BYTE tag, const U32 headGrouped)
{
assert((rowEntries == 16) || (rowEntries == 32) || rowEntries == 64);
if (rowEntries == 16) {
/* vshrn_n_u16 shifts by 4 every u16 and narrows to 8 lower bits.
* After that groups of 4 bits represent the equalMask. We lower
* all bits except the highest in these groups by doing AND with
* 0x88 = 0b10001000.
*/
const uint8x16_t chunk = vld1q_u8(src);
const uint16x8_t equalMask = vreinterpretq_u16_u8(vceqq_u8(chunk, vdupq_n_u8(tag)));
const uint8x8_t res = vshrn_n_u16(equalMask, 4);
const U64 matches = vget_lane_u64(vreinterpret_u64_u8(res), 0);
return ZSTD_rotateRight_U64(matches, headGrouped) & 0x8888888888888888ull;
} else if (rowEntries == 32) {
/* Same idea as with rowEntries == 16 but doing AND with
* 0x55 = 0b01010101.
*/
const uint16x8x2_t chunk = vld2q_u16((const uint16_t*)(const void*)src);
const uint8x16_t chunk0 = vreinterpretq_u8_u16(chunk.val[0]);
const uint8x16_t chunk1 = vreinterpretq_u8_u16(chunk.val[1]);
const uint8x16_t dup = vdupq_n_u8(tag);
const uint8x8_t t0 = vshrn_n_u16(vreinterpretq_u16_u8(vceqq_u8(chunk0, dup)), 6);
const uint8x8_t t1 = vshrn_n_u16(vreinterpretq_u16_u8(vceqq_u8(chunk1, dup)), 6);
const uint8x8_t res = vsli_n_u8(t0, t1, 4);
const U64 matches = vget_lane_u64(vreinterpret_u64_u8(res), 0) ;
return ZSTD_rotateRight_U64(matches, headGrouped) & 0x5555555555555555ull;
} else { /* rowEntries == 64 */
const uint8x16x4_t chunk = vld4q_u8(src);
const uint8x16_t dup = vdupq_n_u8(tag);
const uint8x16_t cmp0 = vceqq_u8(chunk.val[0], dup);
const uint8x16_t cmp1 = vceqq_u8(chunk.val[1], dup);
const uint8x16_t cmp2 = vceqq_u8(chunk.val[2], dup);
const uint8x16_t cmp3 = vceqq_u8(chunk.val[3], dup);
const uint8x16_t t0 = vsriq_n_u8(cmp1, cmp0, 1);
const uint8x16_t t1 = vsriq_n_u8(cmp3, cmp2, 1);
const uint8x16_t t2 = vsriq_n_u8(t1, t0, 2);
const uint8x16_t t3 = vsriq_n_u8(t2, t2, 4);
const uint8x8_t t4 = vshrn_n_u16(vreinterpretq_u16_u8(t3), 4);
const U64 matches = vget_lane_u64(vreinterpret_u64_u8(t4), 0);
return ZSTD_rotateRight_U64(matches, headGrouped);
}
}
#endif
/* Returns a ZSTD_VecMask (U64) that has the nth group (determined by
* ZSTD_row_matchMaskGroupWidth) of bits set to 1 if the newly-computed "tag"
* matches the hash at the nth position in a row of the tagTable.
* Each row is a circular buffer beginning at the value of "headGrouped". So we
* must rotate the "matches" bitfield to match up with the actual layout of the
* entries within the hashTable */
FORCE_INLINE_TEMPLATE ZSTD_VecMask
ZSTD_row_getMatchMask(const BYTE* const tagRow, const BYTE tag, const U32 headGrouped, const U32 rowEntries)
{
const BYTE* const src = tagRow;
assert((rowEntries == 16) || (rowEntries == 32) || rowEntries == 64);
assert(rowEntries <= ZSTD_ROW_HASH_MAX_ENTRIES);
assert(ZSTD_row_matchMaskGroupWidth(rowEntries) * rowEntries <= sizeof(ZSTD_VecMask) * 8);
#if defined(ZSTD_ARCH_X86_SSE2)
return ZSTD_row_getSSEMask(rowEntries / 16, src, tag, headGrouped);
#else /* SW or NEON-LE */
# if defined(ZSTD_ARCH_ARM_NEON)
/* This NEON path only works for little endian - otherwise use SWAR below */
if (MEM_isLittleEndian()) {
return ZSTD_row_getNEONMask(rowEntries, src, tag, headGrouped);
}
# endif /* ZSTD_ARCH_ARM_NEON */
/* SWAR */
{ const int chunkSize = sizeof(size_t);
const size_t shiftAmount = ((chunkSize * 8) - chunkSize);
const size_t xFF = ~((size_t)0);
const size_t x01 = xFF / 0xFF;
const size_t x80 = x01 << 7;
const size_t splatChar = tag * x01;
ZSTD_VecMask matches = 0;
int i = rowEntries - chunkSize;
assert((sizeof(size_t) == 4) || (sizeof(size_t) == 8));
if (MEM_isLittleEndian()) { /* runtime check so have two loops */
const size_t extractMagic = (xFF / 0x7F) >> chunkSize;
do {
size_t chunk = MEM_readST(&src[i]);
chunk ^= splatChar;
chunk = (((chunk | x80) - x01) | chunk) & x80;
matches <<= chunkSize;
matches |= (chunk * extractMagic) >> shiftAmount;
i -= chunkSize;
} while (i >= 0);
} else { /* big endian: reverse bits during extraction */
const size_t msb = xFF ^ (xFF >> 1);
const size_t extractMagic = (msb / 0x1FF) | msb;
do {
size_t chunk = MEM_readST(&src[i]);
chunk ^= splatChar;
chunk = (((chunk | x80) - x01) | chunk) & x80;
matches <<= chunkSize;
matches |= ((chunk >> 7) * extractMagic) >> shiftAmount;
i -= chunkSize;
} while (i >= 0);
}
matches = ~matches;
if (rowEntries == 16) {
return ZSTD_rotateRight_U16((U16)matches, headGrouped);
} else if (rowEntries == 32) {
return ZSTD_rotateRight_U32((U32)matches, headGrouped);
} else {
return ZSTD_rotateRight_U64((U64)matches, headGrouped);
}
}
#endif
}
/* The high-level approach of the SIMD row based match finder is as follows:
* - Figure out where to insert the new entry:
* - Generate a hash from a byte along with an additional 1-byte "short hash". The additional byte is our "tag"
* - The hashTable is effectively split into groups or "rows" of 16 or 32 entries of U32, and the hash determines
* which row to insert into.
* - Determine the correct position within the row to insert the entry into. Each row of 16 or 32 can
* be considered as a circular buffer with a "head" index that resides in the tagTable.
* - Also insert the "tag" into the equivalent row and position in the tagTable.
* - Note: The tagTable has 17 or 33 1-byte entries per row, due to 16 or 32 tags, and 1 "head" entry.
* The 17 or 33 entry rows are spaced out to occur every 32 or 64 bytes, respectively,
* for alignment/performance reasons, leaving some bytes unused.
* - Use SIMD to efficiently compare the tags in the tagTable to the 1-byte "short hash" and
* generate a bitfield that we can cycle through to check the collisions in the hash table.
* - Pick the longest match.
*/
FORCE_INLINE_TEMPLATE
size_t ZSTD_RowFindBestMatch(
ZSTD_matchState_t* ms,
const BYTE* const ip, const BYTE* const iLimit,
size_t* offsetPtr,
const U32 mls, const ZSTD_dictMode_e dictMode,
const U32 rowLog)
{
U32* const hashTable = ms->hashTable;
BYTE* const tagTable = ms->tagTable;
U32* const hashCache = ms->hashCache;
const U32 hashLog = ms->rowHashLog;
const ZSTD_compressionParameters* const cParams = &ms->cParams;
const BYTE* const base = ms->window.base;
const BYTE* const dictBase = ms->window.dictBase;
const U32 dictLimit = ms->window.dictLimit;
const BYTE* const prefixStart = base + dictLimit;
const BYTE* const dictEnd = dictBase + dictLimit;
const U32 curr = (U32)(ip-base);
const U32 maxDistance = 1U << cParams->windowLog;
const U32 lowestValid = ms->window.lowLimit;
const U32 withinMaxDistance = (curr - lowestValid > maxDistance) ? curr - maxDistance : lowestValid;
const U32 isDictionary = (ms->loadedDictEnd != 0);
const U32 lowLimit = isDictionary ? lowestValid : withinMaxDistance;
const U32 rowEntries = (1U << rowLog);
const U32 rowMask = rowEntries - 1;
const U32 cappedSearchLog = MIN(cParams->searchLog, rowLog); /* nb of searches is capped at nb entries per row */
const U32 groupWidth = ZSTD_row_matchMaskGroupWidth(rowEntries);
const U64 hashSalt = ms->hashSalt;
U32 nbAttempts = 1U << cappedSearchLog;
size_t ml=4-1;
U32 hash;
/* DMS/DDS variables that may be referenced laster */
const ZSTD_matchState_t* const dms = ms->dictMatchState;
/* Initialize the following variables to satisfy static analyzer */
size_t ddsIdx = 0;
U32 ddsExtraAttempts = 0; /* cctx hash tables are limited in searches, but allow extra searches into DDS */
U32 dmsTag = 0;
U32* dmsRow = NULL;
BYTE* dmsTagRow = NULL;
if (dictMode == ZSTD_dedicatedDictSearch) {
const U32 ddsHashLog = dms->cParams.hashLog - ZSTD_LAZY_DDSS_BUCKET_LOG;
{ /* Prefetch DDS hashtable entry */
ddsIdx = ZSTD_hashPtr(ip, ddsHashLog, mls) << ZSTD_LAZY_DDSS_BUCKET_LOG;
PREFETCH_L1(&dms->hashTable[ddsIdx]);
}
ddsExtraAttempts = cParams->searchLog > rowLog ? 1U << (cParams->searchLog - rowLog) : 0;
}
if (dictMode == ZSTD_dictMatchState) {
/* Prefetch DMS rows */
U32* const dmsHashTable = dms->hashTable;
BYTE* const dmsTagTable = dms->tagTable;
U32 const dmsHash = (U32)ZSTD_hashPtr(ip, dms->rowHashLog + ZSTD_ROW_HASH_TAG_BITS, mls);
U32 const dmsRelRow = (dmsHash >> ZSTD_ROW_HASH_TAG_BITS) << rowLog;
dmsTag = dmsHash & ZSTD_ROW_HASH_TAG_MASK;
dmsTagRow = (BYTE*)(dmsTagTable + dmsRelRow);
dmsRow = dmsHashTable + dmsRelRow;
ZSTD_row_prefetch(dmsHashTable, dmsTagTable, dmsRelRow, rowLog);
}
/* Update the hashTable and tagTable up to (but not including) ip */
if (!ms->lazySkipping) {
ZSTD_row_update_internal(ms, ip, mls, rowLog, rowMask, 1 /* useCache */);
hash = ZSTD_row_nextCachedHash(hashCache, hashTable, tagTable, base, curr, hashLog, rowLog, mls, hashSalt);
} else {
/* Stop inserting every position when in the lazy skipping mode.
* The hash cache is also not kept up to date in this mode.
*/
hash = (U32)ZSTD_hashPtrSalted(ip, hashLog + ZSTD_ROW_HASH_TAG_BITS, mls, hashSalt);
ms->nextToUpdate = curr;
}
ms->hashSaltEntropy += hash; /* collect salt entropy */
{ /* Get the hash for ip, compute the appropriate row */
U32 const relRow = (hash >> ZSTD_ROW_HASH_TAG_BITS) << rowLog;
U32 const tag = hash & ZSTD_ROW_HASH_TAG_MASK;
U32* const row = hashTable + relRow;
BYTE* tagRow = (BYTE*)(tagTable + relRow);
U32 const headGrouped = (*tagRow & rowMask) * groupWidth;
U32 matchBuffer[ZSTD_ROW_HASH_MAX_ENTRIES];
size_t numMatches = 0;
size_t currMatch = 0;
ZSTD_VecMask matches = ZSTD_row_getMatchMask(tagRow, (BYTE)tag, headGrouped, rowEntries);
/* Cycle through the matches and prefetch */
for (; (matches > 0) && (nbAttempts > 0); matches &= (matches - 1)) {
U32 const matchPos = ((headGrouped + ZSTD_VecMask_next(matches)) / groupWidth) & rowMask;
U32 const matchIndex = row[matchPos];
if(matchPos == 0) continue;
assert(numMatches < rowEntries);
if (matchIndex < lowLimit)
break;
if ((dictMode != ZSTD_extDict) || matchIndex >= dictLimit) {
PREFETCH_L1(base + matchIndex);
} else {
PREFETCH_L1(dictBase + matchIndex);
}
matchBuffer[numMatches++] = matchIndex;
--nbAttempts;
}
/* Speed opt: insert current byte into hashtable too. This allows us to avoid one iteration of the loop
in ZSTD_row_update_internal() at the next search. */
{
U32 const pos = ZSTD_row_nextIndex(tagRow, rowMask);
tagRow[pos] = (BYTE)tag;
row[pos] = ms->nextToUpdate++;
}
/* Return the longest match */
for (; currMatch < numMatches; ++currMatch) {
U32 const matchIndex = matchBuffer[currMatch];
size_t currentMl=0;
assert(matchIndex < curr);
assert(matchIndex >= lowLimit);
if ((dictMode != ZSTD_extDict) || matchIndex >= dictLimit) {
const BYTE* const match = base + matchIndex;
assert(matchIndex >= dictLimit); /* ensures this is true if dictMode != ZSTD_extDict */
/* read 4B starting from (match + ml + 1 - sizeof(U32)) */
if (MEM_read32(match + ml - 3) == MEM_read32(ip + ml - 3)) /* potentially better */
currentMl = ZSTD_count(ip, match, iLimit);
} else {
const BYTE* const match = dictBase + matchIndex;
assert(match+4 <= dictEnd);
if (MEM_read32(match) == MEM_read32(ip)) /* assumption : matchIndex <= dictLimit-4 (by table construction) */
currentMl = ZSTD_count_2segments(ip+4, match+4, iLimit, dictEnd, prefixStart) + 4;
}
/* Save best solution */
if (currentMl > ml) {
ml = currentMl;
*offsetPtr = OFFSET_TO_OFFBASE(curr - matchIndex);
if (ip+currentMl == iLimit) break; /* best possible, avoids read overflow on next attempt */
}
}
}
assert(nbAttempts <= (1U << ZSTD_SEARCHLOG_MAX)); /* Check we haven't underflowed. */
if (dictMode == ZSTD_dedicatedDictSearch) {
ml = ZSTD_dedicatedDictSearch_lazy_search(offsetPtr, ml, nbAttempts + ddsExtraAttempts, dms,
ip, iLimit, prefixStart, curr, dictLimit, ddsIdx);
} else if (dictMode == ZSTD_dictMatchState) {
/* TODO: Measure and potentially add prefetching to DMS */
const U32 dmsLowestIndex = dms->window.dictLimit;
const BYTE* const dmsBase = dms->window.base;
const BYTE* const dmsEnd = dms->window.nextSrc;
const U32 dmsSize = (U32)(dmsEnd - dmsBase);
const U32 dmsIndexDelta = dictLimit - dmsSize;
{ U32 const headGrouped = (*dmsTagRow & rowMask) * groupWidth;
U32 matchBuffer[ZSTD_ROW_HASH_MAX_ENTRIES];
size_t numMatches = 0;
size_t currMatch = 0;
ZSTD_VecMask matches = ZSTD_row_getMatchMask(dmsTagRow, (BYTE)dmsTag, headGrouped, rowEntries);
for (; (matches > 0) && (nbAttempts > 0); matches &= (matches - 1)) {
U32 const matchPos = ((headGrouped + ZSTD_VecMask_next(matches)) / groupWidth) & rowMask;
U32 const matchIndex = dmsRow[matchPos];
if(matchPos == 0) continue;
if (matchIndex < dmsLowestIndex)
break;
PREFETCH_L1(dmsBase + matchIndex);
matchBuffer[numMatches++] = matchIndex;
--nbAttempts;
}
/* Return the longest match */
for (; currMatch < numMatches; ++currMatch) {
U32 const matchIndex = matchBuffer[currMatch];
size_t currentMl=0;
assert(matchIndex >= dmsLowestIndex);
assert(matchIndex < curr);
{ const BYTE* const match = dmsBase + matchIndex;
assert(match+4 <= dmsEnd);
if (MEM_read32(match) == MEM_read32(ip))
currentMl = ZSTD_count_2segments(ip+4, match+4, iLimit, dmsEnd, prefixStart) + 4;
}
if (currentMl > ml) {
ml = currentMl;
assert(curr > matchIndex + dmsIndexDelta);
*offsetPtr = OFFSET_TO_OFFBASE(curr - (matchIndex + dmsIndexDelta));
if (ip+currentMl == iLimit) break;
}
}
}
}
return ml;
}
/**
* Generate search functions templated on (dictMode, mls, rowLog).
* These functions are outlined for code size & compilation time.
* ZSTD_searchMax() dispatches to the correct implementation function.
*
* TODO: The start of the search function involves loading and calculating a
* bunch of constants from the ZSTD_matchState_t. These computations could be
* done in an initialization function, and saved somewhere in the match state.
* Then we could pass a pointer to the saved state instead of the match state,
* and avoid duplicate computations.
*
* TODO: Move the match re-winding into searchMax. This improves compression
* ratio, and unlocks further simplifications with the next TODO.
*
* TODO: Try moving the repcode search into searchMax. After the re-winding
* and repcode search are in searchMax, there is no more logic in the match
* finder loop that requires knowledge about the dictMode. So we should be
* able to avoid force inlining it, and we can join the extDict loop with
* the single segment loop. It should go in searchMax instead of its own
* function to avoid having multiple virtual function calls per search.
*/
#define ZSTD_BT_SEARCH_FN(dictMode, mls) ZSTD_BtFindBestMatch_##dictMode##_##mls
#define ZSTD_HC_SEARCH_FN(dictMode, mls) ZSTD_HcFindBestMatch_##dictMode##_##mls
#define ZSTD_ROW_SEARCH_FN(dictMode, mls, rowLog) ZSTD_RowFindBestMatch_##dictMode##_##mls##_##rowLog
#define ZSTD_SEARCH_FN_ATTRS FORCE_NOINLINE
#define GEN_ZSTD_BT_SEARCH_FN(dictMode, mls) \
ZSTD_SEARCH_FN_ATTRS size_t ZSTD_BT_SEARCH_FN(dictMode, mls)( \
ZSTD_matchState_t* ms, \
const BYTE* ip, const BYTE* const iLimit, \
size_t* offBasePtr) \
{ \
assert(MAX(4, MIN(6, ms->cParams.minMatch)) == mls); \
return ZSTD_BtFindBestMatch(ms, ip, iLimit, offBasePtr, mls, ZSTD_##dictMode); \
} \
#define GEN_ZSTD_HC_SEARCH_FN(dictMode, mls) \
ZSTD_SEARCH_FN_ATTRS size_t ZSTD_HC_SEARCH_FN(dictMode, mls)( \
ZSTD_matchState_t* ms, \
const BYTE* ip, const BYTE* const iLimit, \
size_t* offsetPtr) \
{ \
assert(MAX(4, MIN(6, ms->cParams.minMatch)) == mls); \
return ZSTD_HcFindBestMatch(ms, ip, iLimit, offsetPtr, mls, ZSTD_##dictMode); \
} \
#define GEN_ZSTD_ROW_SEARCH_FN(dictMode, mls, rowLog) \
ZSTD_SEARCH_FN_ATTRS size_t ZSTD_ROW_SEARCH_FN(dictMode, mls, rowLog)( \
ZSTD_matchState_t* ms, \
const BYTE* ip, const BYTE* const iLimit, \
size_t* offsetPtr) \
{ \
assert(MAX(4, MIN(6, ms->cParams.minMatch)) == mls); \
assert(MAX(4, MIN(6, ms->cParams.searchLog)) == rowLog); \
return ZSTD_RowFindBestMatch(ms, ip, iLimit, offsetPtr, mls, ZSTD_##dictMode, rowLog); \
} \
#define ZSTD_FOR_EACH_ROWLOG(X, dictMode, mls) \
X(dictMode, mls, 4) \
X(dictMode, mls, 5) \
X(dictMode, mls, 6)
#define ZSTD_FOR_EACH_MLS_ROWLOG(X, dictMode) \
ZSTD_FOR_EACH_ROWLOG(X, dictMode, 4) \
ZSTD_FOR_EACH_ROWLOG(X, dictMode, 5) \
ZSTD_FOR_EACH_ROWLOG(X, dictMode, 6)
#define ZSTD_FOR_EACH_MLS(X, dictMode) \
X(dictMode, 4) \
X(dictMode, 5) \
X(dictMode, 6)
#define ZSTD_FOR_EACH_DICT_MODE(X, ...) \
X(__VA_ARGS__, noDict) \
X(__VA_ARGS__, extDict) \
X(__VA_ARGS__, dictMatchState) \
X(__VA_ARGS__, dedicatedDictSearch)
/* Generate row search fns for each combination of (dictMode, mls, rowLog) */
ZSTD_FOR_EACH_DICT_MODE(ZSTD_FOR_EACH_MLS_ROWLOG, GEN_ZSTD_ROW_SEARCH_FN)
/* Generate binary Tree search fns for each combination of (dictMode, mls) */
ZSTD_FOR_EACH_DICT_MODE(ZSTD_FOR_EACH_MLS, GEN_ZSTD_BT_SEARCH_FN)
/* Generate hash chain search fns for each combination of (dictMode, mls) */
ZSTD_FOR_EACH_DICT_MODE(ZSTD_FOR_EACH_MLS, GEN_ZSTD_HC_SEARCH_FN)
typedef enum { search_hashChain=0, search_binaryTree=1, search_rowHash=2 } searchMethod_e;
#define GEN_ZSTD_CALL_BT_SEARCH_FN(dictMode, mls) \
case mls: \
return ZSTD_BT_SEARCH_FN(dictMode, mls)(ms, ip, iend, offsetPtr);
#define GEN_ZSTD_CALL_HC_SEARCH_FN(dictMode, mls) \
case mls: \
return ZSTD_HC_SEARCH_FN(dictMode, mls)(ms, ip, iend, offsetPtr);
#define GEN_ZSTD_CALL_ROW_SEARCH_FN(dictMode, mls, rowLog) \
case rowLog: \
return ZSTD_ROW_SEARCH_FN(dictMode, mls, rowLog)(ms, ip, iend, offsetPtr);
#define ZSTD_SWITCH_MLS(X, dictMode) \
switch (mls) { \
ZSTD_FOR_EACH_MLS(X, dictMode) \
}
#define ZSTD_SWITCH_ROWLOG(dictMode, mls) \
case mls: \
switch (rowLog) { \
ZSTD_FOR_EACH_ROWLOG(GEN_ZSTD_CALL_ROW_SEARCH_FN, dictMode, mls) \
} \
ZSTD_UNREACHABLE; \
break;
#define ZSTD_SWITCH_SEARCH_METHOD(dictMode) \
switch (searchMethod) { \
case search_hashChain: \
ZSTD_SWITCH_MLS(GEN_ZSTD_CALL_HC_SEARCH_FN, dictMode) \
break; \
case search_binaryTree: \
ZSTD_SWITCH_MLS(GEN_ZSTD_CALL_BT_SEARCH_FN, dictMode) \
break; \
case search_rowHash: \
ZSTD_SWITCH_MLS(ZSTD_SWITCH_ROWLOG, dictMode) \
break; \
} \
ZSTD_UNREACHABLE;
/**
* Searches for the longest match at @p ip.
* Dispatches to the correct implementation function based on the
* (searchMethod, dictMode, mls, rowLog). We use switch statements
* here instead of using an indirect function call through a function
* pointer because after Spectre and Meltdown mitigations, indirect
* function calls can be very costly, especially in the kernel.
*
* NOTE: dictMode and searchMethod should be templated, so those switch
* statements should be optimized out. Only the mls & rowLog switches
* should be left.
*
* @param ms The match state.
* @param ip The position to search at.
* @param iend The end of the input data.
* @param[out] offsetPtr Stores the match offset into this pointer.
* @param mls The minimum search length, in the range [4, 6].
* @param rowLog The row log (if applicable), in the range [4, 6].
* @param searchMethod The search method to use (templated).
* @param dictMode The dictMode (templated).
*
* @returns The length of the longest match found, or < mls if no match is found.
* If a match is found its offset is stored in @p offsetPtr.
*/
FORCE_INLINE_TEMPLATE size_t ZSTD_searchMax(
ZSTD_matchState_t* ms,
const BYTE* ip,
const BYTE* iend,
size_t* offsetPtr,
U32 const mls,
U32 const rowLog,
searchMethod_e const searchMethod,
ZSTD_dictMode_e const dictMode)
{
if (dictMode == ZSTD_noDict) {
ZSTD_SWITCH_SEARCH_METHOD(noDict)
} else if (dictMode == ZSTD_extDict) {
ZSTD_SWITCH_SEARCH_METHOD(extDict)
} else if (dictMode == ZSTD_dictMatchState) {
ZSTD_SWITCH_SEARCH_METHOD(dictMatchState)
} else if (dictMode == ZSTD_dedicatedDictSearch) {
ZSTD_SWITCH_SEARCH_METHOD(dedicatedDictSearch)
}
ZSTD_UNREACHABLE;
return 0;
}
/* *******************************
* Common parser - lazy strategy
*********************************/
FORCE_INLINE_TEMPLATE size_t
ZSTD_compressBlock_lazy_generic(
ZSTD_matchState_t* ms, seqStore_t* seqStore,
U32 rep[ZSTD_REP_NUM],
const void* src, size_t srcSize,
const searchMethod_e searchMethod, const U32 depth,
ZSTD_dictMode_e const dictMode)
{
const BYTE* const istart = (const BYTE*)src;
const BYTE* ip = istart;
const BYTE* anchor = istart;
const BYTE* const iend = istart + srcSize;
const BYTE* const ilimit = (searchMethod == search_rowHash) ? iend - 8 - ZSTD_ROW_HASH_CACHE_SIZE : iend - 8;
const BYTE* const base = ms->window.base;
const U32 prefixLowestIndex = ms->window.dictLimit;
const BYTE* const prefixLowest = base + prefixLowestIndex;
const U32 mls = BOUNDED(4, ms->cParams.minMatch, 6);
const U32 rowLog = BOUNDED(4, ms->cParams.searchLog, 6);
U32 offset_1 = rep[0], offset_2 = rep[1];
U32 offsetSaved1 = 0, offsetSaved2 = 0;
const int isDMS = dictMode == ZSTD_dictMatchState;
const int isDDS = dictMode == ZSTD_dedicatedDictSearch;
const int isDxS = isDMS || isDDS;
const ZSTD_matchState_t* const dms = ms->dictMatchState;
const U32 dictLowestIndex = isDxS ? dms->window.dictLimit : 0;
const BYTE* const dictBase = isDxS ? dms->window.base : NULL;
const BYTE* const dictLowest = isDxS ? dictBase + dictLowestIndex : NULL;
const BYTE* const dictEnd = isDxS ? dms->window.nextSrc : NULL;
const U32 dictIndexDelta = isDxS ?
prefixLowestIndex - (U32)(dictEnd - dictBase) :
0;
const U32 dictAndPrefixLength = (U32)((ip - prefixLowest) + (dictEnd - dictLowest));
DEBUGLOG(5, "ZSTD_compressBlock_lazy_generic (dictMode=%u) (searchFunc=%u)", (U32)dictMode, (U32)searchMethod);
ip += (dictAndPrefixLength == 0);
if (dictMode == ZSTD_noDict) {
U32 const curr = (U32)(ip - base);
U32 const windowLow = ZSTD_getLowestPrefixIndex(ms, curr, ms->cParams.windowLog);
U32 const maxRep = curr - windowLow;
if (offset_2 > maxRep) offsetSaved2 = offset_2, offset_2 = 0;
if (offset_1 > maxRep) offsetSaved1 = offset_1, offset_1 = 0;
}
if (isDxS) {
/* dictMatchState repCode checks don't currently handle repCode == 0
* disabling. */
assert(offset_1 <= dictAndPrefixLength);
assert(offset_2 <= dictAndPrefixLength);
}
/* Reset the lazy skipping state */
ms->lazySkipping = 0;
if (searchMethod == search_rowHash) {
ZSTD_row_fillHashCache(ms, base, rowLog, mls, ms->nextToUpdate, ilimit);
}
/* Match Loop */
#if defined(__GNUC__) && defined(__x86_64__)
/* I've measured random a 5% speed loss on levels 5 & 6 (greedy) when the
* code alignment is perturbed. To fix the instability align the loop on 32-bytes.
*/
__asm__(".p2align 5");
#endif
while (ip < ilimit) {
size_t matchLength=0;
size_t offBase = REPCODE1_TO_OFFBASE;
const BYTE* start=ip+1;
DEBUGLOG(7, "search baseline (depth 0)");
/* check repCode */
if (isDxS) {
const U32 repIndex = (U32)(ip - base) + 1 - offset_1;
const BYTE* repMatch = ((dictMode == ZSTD_dictMatchState || dictMode == ZSTD_dedicatedDictSearch)
&& repIndex < prefixLowestIndex) ?
dictBase + (repIndex - dictIndexDelta) :
base + repIndex;
if (((U32)((prefixLowestIndex-1) - repIndex) >= 3 /* intentional underflow */)
&& (MEM_read32(repMatch) == MEM_read32(ip+1)) ) {
const BYTE* repMatchEnd = repIndex < prefixLowestIndex ? dictEnd : iend;
matchLength = ZSTD_count_2segments(ip+1+4, repMatch+4, iend, repMatchEnd, prefixLowest) + 4;
if (depth==0) goto _storeSequence;
}
}
if ( dictMode == ZSTD_noDict
&& ((offset_1 > 0) & (MEM_read32(ip+1-offset_1) == MEM_read32(ip+1)))) {
matchLength = ZSTD_count(ip+1+4, ip+1+4-offset_1, iend) + 4;
if (depth==0) goto _storeSequence;
}
/* first search (depth 0) */
{ size_t offbaseFound = 999999999;
size_t const ml2 = ZSTD_searchMax(ms, ip, iend, &offbaseFound, mls, rowLog, searchMethod, dictMode);
if (ml2 > matchLength)
matchLength = ml2, start = ip, offBase = offbaseFound;
}
if (matchLength < 4) {
size_t const step = ((size_t)(ip-anchor) >> kSearchStrength) + 1; /* jump faster over incompressible sections */;
ip += step;
/* Enter the lazy skipping mode once we are skipping more than 8 bytes at a time.
* In this mode we stop inserting every position into our tables, and only insert
* positions that we search, which is one in step positions.
* The exact cutoff is flexible, I've just chosen a number that is reasonably high,
* so we minimize the compression ratio loss in "normal" scenarios. This mode gets
* triggered once we've gone 2KB without finding any matches.
*/
ms->lazySkipping = step > kLazySkippingStep;
continue;
}
/* let's try to find a better solution */
if (depth>=1)
while (ip<ilimit) {
DEBUGLOG(7, "search depth 1");
ip ++;
if ( (dictMode == ZSTD_noDict)
&& (offBase) && ((offset_1>0) & (MEM_read32(ip) == MEM_read32(ip - offset_1)))) {
size_t const mlRep = ZSTD_count(ip+4, ip+4-offset_1, iend) + 4;
int const gain2 = (int)(mlRep * 3);
int const gain1 = (int)(matchLength*3 - ZSTD_highbit32((U32)offBase) + 1);
if ((mlRep >= 4) && (gain2 > gain1))
matchLength = mlRep, offBase = REPCODE1_TO_OFFBASE, start = ip;
}
if (isDxS) {
const U32 repIndex = (U32)(ip - base) - offset_1;
const BYTE* repMatch = repIndex < prefixLowestIndex ?
dictBase + (repIndex - dictIndexDelta) :
base + repIndex;
if (((U32)((prefixLowestIndex-1) - repIndex) >= 3 /* intentional underflow */)
&& (MEM_read32(repMatch) == MEM_read32(ip)) ) {
const BYTE* repMatchEnd = repIndex < prefixLowestIndex ? dictEnd : iend;
size_t const mlRep = ZSTD_count_2segments(ip+4, repMatch+4, iend, repMatchEnd, prefixLowest) + 4;
int const gain2 = (int)(mlRep * 3);
int const gain1 = (int)(matchLength*3 - ZSTD_highbit32((U32)offBase) + 1);
if ((mlRep >= 4) && (gain2 > gain1))
matchLength = mlRep, offBase = REPCODE1_TO_OFFBASE, start = ip;
}
}
{ size_t ofbCandidate=999999999;
size_t const ml2 = ZSTD_searchMax(ms, ip, iend, &ofbCandidate, mls, rowLog, searchMethod, dictMode);
int const gain2 = (int)(ml2*4 - ZSTD_highbit32((U32)ofbCandidate)); /* raw approx */
int const gain1 = (int)(matchLength*4 - ZSTD_highbit32((U32)offBase) + 4);
if ((ml2 >= 4) && (gain2 > gain1)) {
matchLength = ml2, offBase = ofbCandidate, start = ip;
continue; /* search a better one */
} }
/* let's find an even better one */
if ((depth==2) && (ip<ilimit)) {
DEBUGLOG(7, "search depth 2");
ip ++;
if ( (dictMode == ZSTD_noDict)
&& (offBase) && ((offset_1>0) & (MEM_read32(ip) == MEM_read32(ip - offset_1)))) {
size_t const mlRep = ZSTD_count(ip+4, ip+4-offset_1, iend) + 4;
int const gain2 = (int)(mlRep * 4);
int const gain1 = (int)(matchLength*4 - ZSTD_highbit32((U32)offBase) + 1);
if ((mlRep >= 4) && (gain2 > gain1))
matchLength = mlRep, offBase = REPCODE1_TO_OFFBASE, start = ip;
}
if (isDxS) {
const U32 repIndex = (U32)(ip - base) - offset_1;
const BYTE* repMatch = repIndex < prefixLowestIndex ?
dictBase + (repIndex - dictIndexDelta) :
base + repIndex;
if (((U32)((prefixLowestIndex-1) - repIndex) >= 3 /* intentional underflow */)
&& (MEM_read32(repMatch) == MEM_read32(ip)) ) {
const BYTE* repMatchEnd = repIndex < prefixLowestIndex ? dictEnd : iend;
size_t const mlRep = ZSTD_count_2segments(ip+4, repMatch+4, iend, repMatchEnd, prefixLowest) + 4;
int const gain2 = (int)(mlRep * 4);
int const gain1 = (int)(matchLength*4 - ZSTD_highbit32((U32)offBase) + 1);
if ((mlRep >= 4) && (gain2 > gain1))
matchLength = mlRep, offBase = REPCODE1_TO_OFFBASE, start = ip;
}
}
{ size_t ofbCandidate=999999999;
size_t const ml2 = ZSTD_searchMax(ms, ip, iend, &ofbCandidate, mls, rowLog, searchMethod, dictMode);
int const gain2 = (int)(ml2*4 - ZSTD_highbit32((U32)ofbCandidate)); /* raw approx */
int const gain1 = (int)(matchLength*4 - ZSTD_highbit32((U32)offBase) + 7);
if ((ml2 >= 4) && (gain2 > gain1)) {
matchLength = ml2, offBase = ofbCandidate, start = ip;
continue;
} } }
break; /* nothing found : store previous solution */
}
/* NOTE:
* Pay attention that `start[-value]` can lead to strange undefined behavior
* notably if `value` is unsigned, resulting in a large positive `-value`.
*/
/* catch up */
if (OFFBASE_IS_OFFSET(offBase)) {
if (dictMode == ZSTD_noDict) {
while ( ((start > anchor) & (start - OFFBASE_TO_OFFSET(offBase) > prefixLowest))
&& (start[-1] == (start-OFFBASE_TO_OFFSET(offBase))[-1]) ) /* only search for offset within prefix */
{ start--; matchLength++; }
}
if (isDxS) {
U32 const matchIndex = (U32)((size_t)(start-base) - OFFBASE_TO_OFFSET(offBase));
const BYTE* match = (matchIndex < prefixLowestIndex) ? dictBase + matchIndex - dictIndexDelta : base + matchIndex;
const BYTE* const mStart = (matchIndex < prefixLowestIndex) ? dictLowest : prefixLowest;
while ((start>anchor) && (match>mStart) && (start[-1] == match[-1])) { start--; match--; matchLength++; } /* catch up */
}
offset_2 = offset_1; offset_1 = (U32)OFFBASE_TO_OFFSET(offBase);
}
/* store sequence */
_storeSequence:
{ size_t const litLength = (size_t)(start - anchor);
ZSTD_storeSeq(seqStore, litLength, anchor, iend, (U32)offBase, matchLength);
anchor = ip = start + matchLength;
}
if (ms->lazySkipping) {
/* We've found a match, disable lazy skipping mode, and refill the hash cache. */
if (searchMethod == search_rowHash) {
ZSTD_row_fillHashCache(ms, base, rowLog, mls, ms->nextToUpdate, ilimit);
}
ms->lazySkipping = 0;
}
/* check immediate repcode */
if (isDxS) {
while (ip <= ilimit) {
U32 const current2 = (U32)(ip-base);
U32 const repIndex = current2 - offset_2;
const BYTE* repMatch = repIndex < prefixLowestIndex ?
dictBase - dictIndexDelta + repIndex :
base + repIndex;
if ( ((U32)((prefixLowestIndex-1) - (U32)repIndex) >= 3 /* intentional overflow */)
&& (MEM_read32(repMatch) == MEM_read32(ip)) ) {
const BYTE* const repEnd2 = repIndex < prefixLowestIndex ? dictEnd : iend;
matchLength = ZSTD_count_2segments(ip+4, repMatch+4, iend, repEnd2, prefixLowest) + 4;
offBase = offset_2; offset_2 = offset_1; offset_1 = (U32)offBase; /* swap offset_2 <=> offset_1 */
ZSTD_storeSeq(seqStore, 0, anchor, iend, REPCODE1_TO_OFFBASE, matchLength);
ip += matchLength;
anchor = ip;
continue;
}
break;
}
}
if (dictMode == ZSTD_noDict) {
while ( ((ip <= ilimit) & (offset_2>0))
&& (MEM_read32(ip) == MEM_read32(ip - offset_2)) ) {
/* store sequence */
matchLength = ZSTD_count(ip+4, ip+4-offset_2, iend) + 4;
offBase = offset_2; offset_2 = offset_1; offset_1 = (U32)offBase; /* swap repcodes */
ZSTD_storeSeq(seqStore, 0, anchor, iend, REPCODE1_TO_OFFBASE, matchLength);
ip += matchLength;
anchor = ip;
continue; /* faster when present ... (?) */
} } }
/* If offset_1 started invalid (offsetSaved1 != 0) and became valid (offset_1 != 0),
* rotate saved offsets. See comment in ZSTD_compressBlock_fast_noDict for more context. */
offsetSaved2 = ((offsetSaved1 != 0) && (offset_1 != 0)) ? offsetSaved1 : offsetSaved2;
/* save reps for next block */
rep[0] = offset_1 ? offset_1 : offsetSaved1;
rep[1] = offset_2 ? offset_2 : offsetSaved2;
/* Return the last literals size */
return (size_t)(iend - anchor);
}
size_t ZSTD_compressBlock_btlazy2(
ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
void const* src, size_t srcSize)
{
return ZSTD_compressBlock_lazy_generic(ms, seqStore, rep, src, srcSize, search_binaryTree, 2, ZSTD_noDict);
}
size_t ZSTD_compressBlock_lazy2(
ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
void const* src, size_t srcSize)
{
return ZSTD_compressBlock_lazy_generic(ms, seqStore, rep, src, srcSize, search_hashChain, 2, ZSTD_noDict);
}
size_t ZSTD_compressBlock_lazy(
ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
void const* src, size_t srcSize)
{
return ZSTD_compressBlock_lazy_generic(ms, seqStore, rep, src, srcSize, search_hashChain, 1, ZSTD_noDict);
}
size_t ZSTD_compressBlock_greedy(
ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
void const* src, size_t srcSize)
{
return ZSTD_compressBlock_lazy_generic(ms, seqStore, rep, src, srcSize, search_hashChain, 0, ZSTD_noDict);
}
size_t ZSTD_compressBlock_btlazy2_dictMatchState(
ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
void const* src, size_t srcSize)
{
return ZSTD_compressBlock_lazy_generic(ms, seqStore, rep, src, srcSize, search_binaryTree, 2, ZSTD_dictMatchState);
}
size_t ZSTD_compressBlock_lazy2_dictMatchState(
ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
void const* src, size_t srcSize)
{
return ZSTD_compressBlock_lazy_generic(ms, seqStore, rep, src, srcSize, search_hashChain, 2, ZSTD_dictMatchState);
}
size_t ZSTD_compressBlock_lazy_dictMatchState(
ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
void const* src, size_t srcSize)
{
return ZSTD_compressBlock_lazy_generic(ms, seqStore, rep, src, srcSize, search_hashChain, 1, ZSTD_dictMatchState);
}
size_t ZSTD_compressBlock_greedy_dictMatchState(
ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
void const* src, size_t srcSize)
{
return ZSTD_compressBlock_lazy_generic(ms, seqStore, rep, src, srcSize, search_hashChain, 0, ZSTD_dictMatchState);
}
size_t ZSTD_compressBlock_lazy2_dedicatedDictSearch(
ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
void const* src, size_t srcSize)
{
return ZSTD_compressBlock_lazy_generic(ms, seqStore, rep, src, srcSize, search_hashChain, 2, ZSTD_dedicatedDictSearch);
}
size_t ZSTD_compressBlock_lazy_dedicatedDictSearch(
ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
void const* src, size_t srcSize)
{
return ZSTD_compressBlock_lazy_generic(ms, seqStore, rep, src, srcSize, search_hashChain, 1, ZSTD_dedicatedDictSearch);
}
size_t ZSTD_compressBlock_greedy_dedicatedDictSearch(
ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
void const* src, size_t srcSize)
{
return ZSTD_compressBlock_lazy_generic(ms, seqStore, rep, src, srcSize, search_hashChain, 0, ZSTD_dedicatedDictSearch);
}
/* Row-based matchfinder */
size_t ZSTD_compressBlock_lazy2_row(
ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
void const* src, size_t srcSize)
{
return ZSTD_compressBlock_lazy_generic(ms, seqStore, rep, src, srcSize, search_rowHash, 2, ZSTD_noDict);
}
size_t ZSTD_compressBlock_lazy_row(
ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
void const* src, size_t srcSize)
{
return ZSTD_compressBlock_lazy_generic(ms, seqStore, rep, src, srcSize, search_rowHash, 1, ZSTD_noDict);
}
size_t ZSTD_compressBlock_greedy_row(
ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
void const* src, size_t srcSize)
{
return ZSTD_compressBlock_lazy_generic(ms, seqStore, rep, src, srcSize, search_rowHash, 0, ZSTD_noDict);
}
size_t ZSTD_compressBlock_lazy2_dictMatchState_row(
ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
void const* src, size_t srcSize)
{
return ZSTD_compressBlock_lazy_generic(ms, seqStore, rep, src, srcSize, search_rowHash, 2, ZSTD_dictMatchState);
}
size_t ZSTD_compressBlock_lazy_dictMatchState_row(
ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
void const* src, size_t srcSize)
{
return ZSTD_compressBlock_lazy_generic(ms, seqStore, rep, src, srcSize, search_rowHash, 1, ZSTD_dictMatchState);
}
size_t ZSTD_compressBlock_greedy_dictMatchState_row(
ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
void const* src, size_t srcSize)
{
return ZSTD_compressBlock_lazy_generic(ms, seqStore, rep, src, srcSize, search_rowHash, 0, ZSTD_dictMatchState);
}
size_t ZSTD_compressBlock_lazy2_dedicatedDictSearch_row(
ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
void const* src, size_t srcSize)
{
return ZSTD_compressBlock_lazy_generic(ms, seqStore, rep, src, srcSize, search_rowHash, 2, ZSTD_dedicatedDictSearch);
}
size_t ZSTD_compressBlock_lazy_dedicatedDictSearch_row(
ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
void const* src, size_t srcSize)
{
return ZSTD_compressBlock_lazy_generic(ms, seqStore, rep, src, srcSize, search_rowHash, 1, ZSTD_dedicatedDictSearch);
}
size_t ZSTD_compressBlock_greedy_dedicatedDictSearch_row(
ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
void const* src, size_t srcSize)
{
return ZSTD_compressBlock_lazy_generic(ms, seqStore, rep, src, srcSize, search_rowHash, 0, ZSTD_dedicatedDictSearch);
}
FORCE_INLINE_TEMPLATE
size_t ZSTD_compressBlock_lazy_extDict_generic(
ZSTD_matchState_t* ms, seqStore_t* seqStore,
U32 rep[ZSTD_REP_NUM],
const void* src, size_t srcSize,
const searchMethod_e searchMethod, const U32 depth)
{
const BYTE* const istart = (const BYTE*)src;
const BYTE* ip = istart;
const BYTE* anchor = istart;
const BYTE* const iend = istart + srcSize;
const BYTE* const ilimit = searchMethod == search_rowHash ? iend - 8 - ZSTD_ROW_HASH_CACHE_SIZE : iend - 8;
const BYTE* const base = ms->window.base;
const U32 dictLimit = ms->window.dictLimit;
const BYTE* const prefixStart = base + dictLimit;
const BYTE* const dictBase = ms->window.dictBase;
const BYTE* const dictEnd = dictBase + dictLimit;
const BYTE* const dictStart = dictBase + ms->window.lowLimit;
const U32 windowLog = ms->cParams.windowLog;
const U32 mls = BOUNDED(4, ms->cParams.minMatch, 6);
const U32 rowLog = BOUNDED(4, ms->cParams.searchLog, 6);
U32 offset_1 = rep[0], offset_2 = rep[1];
DEBUGLOG(5, "ZSTD_compressBlock_lazy_extDict_generic (searchFunc=%u)", (U32)searchMethod);
/* Reset the lazy skipping state */
ms->lazySkipping = 0;
/* init */
ip += (ip == prefixStart);
if (searchMethod == search_rowHash) {
ZSTD_row_fillHashCache(ms, base, rowLog, mls, ms->nextToUpdate, ilimit);
}
/* Match Loop */
#if defined(__GNUC__) && defined(__x86_64__)
/* I've measured random a 5% speed loss on levels 5 & 6 (greedy) when the
* code alignment is perturbed. To fix the instability align the loop on 32-bytes.
*/
__asm__(".p2align 5");
#endif
while (ip < ilimit) {
size_t matchLength=0;
size_t offBase = REPCODE1_TO_OFFBASE;
const BYTE* start=ip+1;
U32 curr = (U32)(ip-base);
/* check repCode */
{ const U32 windowLow = ZSTD_getLowestMatchIndex(ms, curr+1, windowLog);
const U32 repIndex = (U32)(curr+1 - offset_1);
const BYTE* const repBase = repIndex < dictLimit ? dictBase : base;
const BYTE* const repMatch = repBase + repIndex;
if ( ((U32)((dictLimit-1) - repIndex) >= 3) /* intentional overflow */
& (offset_1 <= curr+1 - windowLow) ) /* note: we are searching at curr+1 */
if (MEM_read32(ip+1) == MEM_read32(repMatch)) {
/* repcode detected we should take it */
const BYTE* const repEnd = repIndex < dictLimit ? dictEnd : iend;
matchLength = ZSTD_count_2segments(ip+1+4, repMatch+4, iend, repEnd, prefixStart) + 4;
if (depth==0) goto _storeSequence;
} }
/* first search (depth 0) */
{ size_t ofbCandidate = 999999999;
size_t const ml2 = ZSTD_searchMax(ms, ip, iend, &ofbCandidate, mls, rowLog, searchMethod, ZSTD_extDict);
if (ml2 > matchLength)
matchLength = ml2, start = ip, offBase = ofbCandidate;
}
if (matchLength < 4) {
size_t const step = ((size_t)(ip-anchor) >> kSearchStrength);
ip += step + 1; /* jump faster over incompressible sections */
/* Enter the lazy skipping mode once we are skipping more than 8 bytes at a time.
* In this mode we stop inserting every position into our tables, and only insert
* positions that we search, which is one in step positions.
* The exact cutoff is flexible, I've just chosen a number that is reasonably high,
* so we minimize the compression ratio loss in "normal" scenarios. This mode gets
* triggered once we've gone 2KB without finding any matches.
*/
ms->lazySkipping = step > kLazySkippingStep;
continue;
}
/* let's try to find a better solution */
if (depth>=1)
while (ip<ilimit) {
ip ++;
curr++;
/* check repCode */
if (offBase) {
const U32 windowLow = ZSTD_getLowestMatchIndex(ms, curr, windowLog);
const U32 repIndex = (U32)(curr - offset_1);
const BYTE* const repBase = repIndex < dictLimit ? dictBase : base;
const BYTE* const repMatch = repBase + repIndex;
if ( ((U32)((dictLimit-1) - repIndex) >= 3) /* intentional overflow : do not test positions overlapping 2 memory segments */
& (offset_1 <= curr - windowLow) ) /* equivalent to `curr > repIndex >= windowLow` */
if (MEM_read32(ip) == MEM_read32(repMatch)) {
/* repcode detected */
const BYTE* const repEnd = repIndex < dictLimit ? dictEnd : iend;
size_t const repLength = ZSTD_count_2segments(ip+4, repMatch+4, iend, repEnd, prefixStart) + 4;
int const gain2 = (int)(repLength * 3);
int const gain1 = (int)(matchLength*3 - ZSTD_highbit32((U32)offBase) + 1);
if ((repLength >= 4) && (gain2 > gain1))
matchLength = repLength, offBase = REPCODE1_TO_OFFBASE, start = ip;
} }
/* search match, depth 1 */
{ size_t ofbCandidate = 999999999;
size_t const ml2 = ZSTD_searchMax(ms, ip, iend, &ofbCandidate, mls, rowLog, searchMethod, ZSTD_extDict);
int const gain2 = (int)(ml2*4 - ZSTD_highbit32((U32)ofbCandidate)); /* raw approx */
int const gain1 = (int)(matchLength*4 - ZSTD_highbit32((U32)offBase) + 4);
if ((ml2 >= 4) && (gain2 > gain1)) {
matchLength = ml2, offBase = ofbCandidate, start = ip;
continue; /* search a better one */
} }
/* let's find an even better one */
if ((depth==2) && (ip<ilimit)) {
ip ++;
curr++;
/* check repCode */
if (offBase) {
const U32 windowLow = ZSTD_getLowestMatchIndex(ms, curr, windowLog);
const U32 repIndex = (U32)(curr - offset_1);
const BYTE* const repBase = repIndex < dictLimit ? dictBase : base;
const BYTE* const repMatch = repBase + repIndex;
if ( ((U32)((dictLimit-1) - repIndex) >= 3) /* intentional overflow : do not test positions overlapping 2 memory segments */
& (offset_1 <= curr - windowLow) ) /* equivalent to `curr > repIndex >= windowLow` */
if (MEM_read32(ip) == MEM_read32(repMatch)) {
/* repcode detected */
const BYTE* const repEnd = repIndex < dictLimit ? dictEnd : iend;
size_t const repLength = ZSTD_count_2segments(ip+4, repMatch+4, iend, repEnd, prefixStart) + 4;
int const gain2 = (int)(repLength * 4);
int const gain1 = (int)(matchLength*4 - ZSTD_highbit32((U32)offBase) + 1);
if ((repLength >= 4) && (gain2 > gain1))
matchLength = repLength, offBase = REPCODE1_TO_OFFBASE, start = ip;
} }
/* search match, depth 2 */
{ size_t ofbCandidate = 999999999;
size_t const ml2 = ZSTD_searchMax(ms, ip, iend, &ofbCandidate, mls, rowLog, searchMethod, ZSTD_extDict);
int const gain2 = (int)(ml2*4 - ZSTD_highbit32((U32)ofbCandidate)); /* raw approx */
int const gain1 = (int)(matchLength*4 - ZSTD_highbit32((U32)offBase) + 7);
if ((ml2 >= 4) && (gain2 > gain1)) {
matchLength = ml2, offBase = ofbCandidate, start = ip;
continue;
} } }
break; /* nothing found : store previous solution */
}
/* catch up */
if (OFFBASE_IS_OFFSET(offBase)) {
U32 const matchIndex = (U32)((size_t)(start-base) - OFFBASE_TO_OFFSET(offBase));
const BYTE* match = (matchIndex < dictLimit) ? dictBase + matchIndex : base + matchIndex;
const BYTE* const mStart = (matchIndex < dictLimit) ? dictStart : prefixStart;
while ((start>anchor) && (match>mStart) && (start[-1] == match[-1])) { start--; match--; matchLength++; } /* catch up */
offset_2 = offset_1; offset_1 = (U32)OFFBASE_TO_OFFSET(offBase);
}
/* store sequence */
_storeSequence:
{ size_t const litLength = (size_t)(start - anchor);
ZSTD_storeSeq(seqStore, litLength, anchor, iend, (U32)offBase, matchLength);
anchor = ip = start + matchLength;
}
if (ms->lazySkipping) {
/* We've found a match, disable lazy skipping mode, and refill the hash cache. */
if (searchMethod == search_rowHash) {
ZSTD_row_fillHashCache(ms, base, rowLog, mls, ms->nextToUpdate, ilimit);
}
ms->lazySkipping = 0;
}
/* check immediate repcode */
while (ip <= ilimit) {
const U32 repCurrent = (U32)(ip-base);
const U32 windowLow = ZSTD_getLowestMatchIndex(ms, repCurrent, windowLog);
const U32 repIndex = repCurrent - offset_2;
const BYTE* const repBase = repIndex < dictLimit ? dictBase : base;
const BYTE* const repMatch = repBase + repIndex;
if ( ((U32)((dictLimit-1) - repIndex) >= 3) /* intentional overflow : do not test positions overlapping 2 memory segments */
& (offset_2 <= repCurrent - windowLow) ) /* equivalent to `curr > repIndex >= windowLow` */
if (MEM_read32(ip) == MEM_read32(repMatch)) {
/* repcode detected we should take it */
const BYTE* const repEnd = repIndex < dictLimit ? dictEnd : iend;
matchLength = ZSTD_count_2segments(ip+4, repMatch+4, iend, repEnd, prefixStart) + 4;
offBase = offset_2; offset_2 = offset_1; offset_1 = (U32)offBase; /* swap offset history */
ZSTD_storeSeq(seqStore, 0, anchor, iend, REPCODE1_TO_OFFBASE, matchLength);
ip += matchLength;
anchor = ip;
continue; /* faster when present ... (?) */
}
break;
} }
/* Save reps for next block */
rep[0] = offset_1;
rep[1] = offset_2;
/* Return the last literals size */
return (size_t)(iend - anchor);
}
size_t ZSTD_compressBlock_greedy_extDict(
ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
void const* src, size_t srcSize)
{
return ZSTD_compressBlock_lazy_extDict_generic(ms, seqStore, rep, src, srcSize, search_hashChain, 0);
}
size_t ZSTD_compressBlock_lazy_extDict(
ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
void const* src, size_t srcSize)
{
return ZSTD_compressBlock_lazy_extDict_generic(ms, seqStore, rep, src, srcSize, search_hashChain, 1);
}
size_t ZSTD_compressBlock_lazy2_extDict(
ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
void const* src, size_t srcSize)
{
return ZSTD_compressBlock_lazy_extDict_generic(ms, seqStore, rep, src, srcSize, search_hashChain, 2);
}
size_t ZSTD_compressBlock_btlazy2_extDict(
ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
void const* src, size_t srcSize)
{
return ZSTD_compressBlock_lazy_extDict_generic(ms, seqStore, rep, src, srcSize, search_binaryTree, 2);
}
size_t ZSTD_compressBlock_greedy_extDict_row(
ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
void const* src, size_t srcSize)
{
return ZSTD_compressBlock_lazy_extDict_generic(ms, seqStore, rep, src, srcSize, search_rowHash, 0);
}
size_t ZSTD_compressBlock_lazy_extDict_row(
ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
void const* src, size_t srcSize)
{
return ZSTD_compressBlock_lazy_extDict_generic(ms, seqStore, rep, src, srcSize, search_rowHash, 1);
}
size_t ZSTD_compressBlock_lazy2_extDict_row(
ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
void const* src, size_t srcSize)
{
return ZSTD_compressBlock_lazy_extDict_generic(ms, seqStore, rep, src, srcSize, search_rowHash, 2);
}