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zstd_opt.c
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zstd_opt.c
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#ifndef USE_EXTERNAL_ZSTD
/*
* 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 "hist.h"
#include "zstd_opt.h"
#define ZSTD_LITFREQ_ADD 2 /* scaling factor for litFreq, so that frequencies adapt faster to new stats */
#define ZSTD_MAX_PRICE (1<<30)
#define ZSTD_PREDEF_THRESHOLD 8 /* if srcSize < ZSTD_PREDEF_THRESHOLD, symbols' cost is assumed static, directly determined by pre-defined distributions */
/*-*************************************
* Price functions for optimal parser
***************************************/
#if 0 /* approximation at bit level (for tests) */
# define BITCOST_ACCURACY 0
# define BITCOST_MULTIPLIER (1 << BITCOST_ACCURACY)
# define WEIGHT(stat, opt) ((void)(opt), ZSTD_bitWeight(stat))
#elif 0 /* fractional bit accuracy (for tests) */
# define BITCOST_ACCURACY 8
# define BITCOST_MULTIPLIER (1 << BITCOST_ACCURACY)
# define WEIGHT(stat,opt) ((void)(opt), ZSTD_fracWeight(stat))
#else /* opt==approx, ultra==accurate */
# define BITCOST_ACCURACY 8
# define BITCOST_MULTIPLIER (1 << BITCOST_ACCURACY)
# define WEIGHT(stat,opt) ((opt) ? ZSTD_fracWeight(stat) : ZSTD_bitWeight(stat))
#endif
/* ZSTD_bitWeight() :
* provide estimated "cost" of a stat in full bits only */
MEM_STATIC U32 ZSTD_bitWeight(U32 stat)
{
return (ZSTD_highbit32(stat+1) * BITCOST_MULTIPLIER);
}
/* ZSTD_fracWeight() :
* provide fractional-bit "cost" of a stat,
* using linear interpolation approximation */
MEM_STATIC U32 ZSTD_fracWeight(U32 rawStat)
{
U32 const stat = rawStat + 1;
U32 const hb = ZSTD_highbit32(stat);
U32 const BWeight = hb * BITCOST_MULTIPLIER;
/* Fweight was meant for "Fractional weight"
* but it's effectively a value between 1 and 2
* using fixed point arithmetic */
U32 const FWeight = (stat << BITCOST_ACCURACY) >> hb;
U32 const weight = BWeight + FWeight;
assert(hb + BITCOST_ACCURACY < 31);
return weight;
}
#if (DEBUGLEVEL>=2)
/* debugging function,
* @return price in bytes as fractional value
* for debug messages only */
MEM_STATIC double ZSTD_fCost(int price)
{
return (double)price / (BITCOST_MULTIPLIER*8);
}
#endif
static int ZSTD_compressedLiterals(optState_t const* const optPtr)
{
return optPtr->literalCompressionMode != ZSTD_ps_disable;
}
static void ZSTD_setBasePrices(optState_t* optPtr, int optLevel)
{
if (ZSTD_compressedLiterals(optPtr))
optPtr->litSumBasePrice = WEIGHT(optPtr->litSum, optLevel);
optPtr->litLengthSumBasePrice = WEIGHT(optPtr->litLengthSum, optLevel);
optPtr->matchLengthSumBasePrice = WEIGHT(optPtr->matchLengthSum, optLevel);
optPtr->offCodeSumBasePrice = WEIGHT(optPtr->offCodeSum, optLevel);
}
static U32 sum_u32(const unsigned table[], size_t nbElts)
{
size_t n;
U32 total = 0;
for (n=0; n<nbElts; n++) {
total += table[n];
}
return total;
}
typedef enum { base_0possible=0, base_1guaranteed=1 } base_directive_e;
static U32
ZSTD_downscaleStats(unsigned* table, U32 lastEltIndex, U32 shift, base_directive_e base1)
{
U32 s, sum=0;
DEBUGLOG(5, "ZSTD_downscaleStats (nbElts=%u, shift=%u)",
(unsigned)lastEltIndex+1, (unsigned)shift );
assert(shift < 30);
for (s=0; s<lastEltIndex+1; s++) {
unsigned const base = base1 ? 1 : (table[s]>0);
unsigned const newStat = base + (table[s] >> shift);
sum += newStat;
table[s] = newStat;
}
return sum;
}
/* ZSTD_scaleStats() :
* reduce all elt frequencies in table if sum too large
* return the resulting sum of elements */
static U32 ZSTD_scaleStats(unsigned* table, U32 lastEltIndex, U32 logTarget)
{
U32 const prevsum = sum_u32(table, lastEltIndex+1);
U32 const factor = prevsum >> logTarget;
DEBUGLOG(5, "ZSTD_scaleStats (nbElts=%u, target=%u)", (unsigned)lastEltIndex+1, (unsigned)logTarget);
assert(logTarget < 30);
if (factor <= 1) return prevsum;
return ZSTD_downscaleStats(table, lastEltIndex, ZSTD_highbit32(factor), base_1guaranteed);
}
/* ZSTD_rescaleFreqs() :
* if first block (detected by optPtr->litLengthSum == 0) : init statistics
* take hints from dictionary if there is one
* and init from zero if there is none,
* using src for literals stats, and baseline stats for sequence symbols
* otherwise downscale existing stats, to be used as seed for next block.
*/
static void
ZSTD_rescaleFreqs(optState_t* const optPtr,
const BYTE* const src, size_t const srcSize,
int const optLevel)
{
int const compressedLiterals = ZSTD_compressedLiterals(optPtr);
DEBUGLOG(5, "ZSTD_rescaleFreqs (srcSize=%u)", (unsigned)srcSize);
optPtr->priceType = zop_dynamic;
if (optPtr->litLengthSum == 0) { /* no literals stats collected -> first block assumed -> init */
/* heuristic: use pre-defined stats for too small inputs */
if (srcSize <= ZSTD_PREDEF_THRESHOLD) {
DEBUGLOG(5, "srcSize <= %i : use predefined stats", ZSTD_PREDEF_THRESHOLD);
optPtr->priceType = zop_predef;
}
assert(optPtr->symbolCosts != NULL);
if (optPtr->symbolCosts->huf.repeatMode == HUF_repeat_valid) {
/* huffman stats covering the full value set : table presumed generated by dictionary */
optPtr->priceType = zop_dynamic;
if (compressedLiterals) {
/* generate literals statistics from huffman table */
unsigned lit;
assert(optPtr->litFreq != NULL);
optPtr->litSum = 0;
for (lit=0; lit<=MaxLit; lit++) {
U32 const scaleLog = 11; /* scale to 2K */
U32 const bitCost = HUF_getNbBitsFromCTable(optPtr->symbolCosts->huf.CTable, lit);
assert(bitCost <= scaleLog);
optPtr->litFreq[lit] = bitCost ? 1 << (scaleLog-bitCost) : 1 /*minimum to calculate cost*/;
optPtr->litSum += optPtr->litFreq[lit];
} }
{ unsigned ll;
FSE_CState_t llstate;
FSE_initCState(&llstate, optPtr->symbolCosts->fse.litlengthCTable);
optPtr->litLengthSum = 0;
for (ll=0; ll<=MaxLL; ll++) {
U32 const scaleLog = 10; /* scale to 1K */
U32 const bitCost = FSE_getMaxNbBits(llstate.symbolTT, ll);
assert(bitCost < scaleLog);
optPtr->litLengthFreq[ll] = bitCost ? 1 << (scaleLog-bitCost) : 1 /*minimum to calculate cost*/;
optPtr->litLengthSum += optPtr->litLengthFreq[ll];
} }
{ unsigned ml;
FSE_CState_t mlstate;
FSE_initCState(&mlstate, optPtr->symbolCosts->fse.matchlengthCTable);
optPtr->matchLengthSum = 0;
for (ml=0; ml<=MaxML; ml++) {
U32 const scaleLog = 10;
U32 const bitCost = FSE_getMaxNbBits(mlstate.symbolTT, ml);
assert(bitCost < scaleLog);
optPtr->matchLengthFreq[ml] = bitCost ? 1 << (scaleLog-bitCost) : 1 /*minimum to calculate cost*/;
optPtr->matchLengthSum += optPtr->matchLengthFreq[ml];
} }
{ unsigned of;
FSE_CState_t ofstate;
FSE_initCState(&ofstate, optPtr->symbolCosts->fse.offcodeCTable);
optPtr->offCodeSum = 0;
for (of=0; of<=MaxOff; of++) {
U32 const scaleLog = 10;
U32 const bitCost = FSE_getMaxNbBits(ofstate.symbolTT, of);
assert(bitCost < scaleLog);
optPtr->offCodeFreq[of] = bitCost ? 1 << (scaleLog-bitCost) : 1 /*minimum to calculate cost*/;
optPtr->offCodeSum += optPtr->offCodeFreq[of];
} }
} else { /* first block, no dictionary */
assert(optPtr->litFreq != NULL);
if (compressedLiterals) {
/* base initial cost of literals on direct frequency within src */
unsigned lit = MaxLit;
HIST_count_simple(optPtr->litFreq, &lit, src, srcSize); /* use raw first block to init statistics */
optPtr->litSum = ZSTD_downscaleStats(optPtr->litFreq, MaxLit, 8, base_0possible);
}
{ unsigned const baseLLfreqs[MaxLL+1] = {
4, 2, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1
};
ZSTD_memcpy(optPtr->litLengthFreq, baseLLfreqs, sizeof(baseLLfreqs));
optPtr->litLengthSum = sum_u32(baseLLfreqs, MaxLL+1);
}
{ unsigned ml;
for (ml=0; ml<=MaxML; ml++)
optPtr->matchLengthFreq[ml] = 1;
}
optPtr->matchLengthSum = MaxML+1;
{ unsigned const baseOFCfreqs[MaxOff+1] = {
6, 2, 1, 1, 2, 3, 4, 4,
4, 3, 2, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1
};
ZSTD_memcpy(optPtr->offCodeFreq, baseOFCfreqs, sizeof(baseOFCfreqs));
optPtr->offCodeSum = sum_u32(baseOFCfreqs, MaxOff+1);
}
}
} else { /* new block : scale down accumulated statistics */
if (compressedLiterals)
optPtr->litSum = ZSTD_scaleStats(optPtr->litFreq, MaxLit, 12);
optPtr->litLengthSum = ZSTD_scaleStats(optPtr->litLengthFreq, MaxLL, 11);
optPtr->matchLengthSum = ZSTD_scaleStats(optPtr->matchLengthFreq, MaxML, 11);
optPtr->offCodeSum = ZSTD_scaleStats(optPtr->offCodeFreq, MaxOff, 11);
}
ZSTD_setBasePrices(optPtr, optLevel);
}
/* ZSTD_rawLiteralsCost() :
* price of literals (only) in specified segment (which length can be 0).
* does not include price of literalLength symbol */
static U32 ZSTD_rawLiteralsCost(const BYTE* const literals, U32 const litLength,
const optState_t* const optPtr,
int optLevel)
{
if (litLength == 0) return 0;
if (!ZSTD_compressedLiterals(optPtr))
return (litLength << 3) * BITCOST_MULTIPLIER; /* Uncompressed - 8 bytes per literal. */
if (optPtr->priceType == zop_predef)
return (litLength*6) * BITCOST_MULTIPLIER; /* 6 bit per literal - no statistic used */
/* dynamic statistics */
{ U32 price = optPtr->litSumBasePrice * litLength;
U32 const litPriceMax = optPtr->litSumBasePrice - BITCOST_MULTIPLIER;
U32 u;
assert(optPtr->litSumBasePrice >= BITCOST_MULTIPLIER);
for (u=0; u < litLength; u++) {
U32 litPrice = WEIGHT(optPtr->litFreq[literals[u]], optLevel);
if (UNLIKELY(litPrice > litPriceMax)) litPrice = litPriceMax;
price -= litPrice;
}
return price;
}
}
/* ZSTD_litLengthPrice() :
* cost of literalLength symbol */
static U32 ZSTD_litLengthPrice(U32 const litLength, const optState_t* const optPtr, int optLevel)
{
assert(litLength <= ZSTD_BLOCKSIZE_MAX);
if (optPtr->priceType == zop_predef)
return WEIGHT(litLength, optLevel);
/* ZSTD_LLcode() can't compute litLength price for sizes >= ZSTD_BLOCKSIZE_MAX
* because it isn't representable in the zstd format.
* So instead just pretend it would cost 1 bit more than ZSTD_BLOCKSIZE_MAX - 1.
* In such a case, the block would be all literals.
*/
if (litLength == ZSTD_BLOCKSIZE_MAX)
return BITCOST_MULTIPLIER + ZSTD_litLengthPrice(ZSTD_BLOCKSIZE_MAX - 1, optPtr, optLevel);
/* dynamic statistics */
{ U32 const llCode = ZSTD_LLcode(litLength);
return (LL_bits[llCode] * BITCOST_MULTIPLIER)
+ optPtr->litLengthSumBasePrice
- WEIGHT(optPtr->litLengthFreq[llCode], optLevel);
}
}
/* ZSTD_getMatchPrice() :
* Provides the cost of the match part (offset + matchLength) of a sequence.
* Must be combined with ZSTD_fullLiteralsCost() to get the full cost of a sequence.
* @offBase : sumtype, representing an offset or a repcode, and using numeric representation of ZSTD_storeSeq()
* @optLevel: when <2, favors small offset for decompression speed (improved cache efficiency)
*/
FORCE_INLINE_TEMPLATE U32
ZSTD_getMatchPrice(U32 const offBase,
U32 const matchLength,
const optState_t* const optPtr,
int const optLevel)
{
U32 price;
U32 const offCode = ZSTD_highbit32(offBase);
U32 const mlBase = matchLength - MINMATCH;
assert(matchLength >= MINMATCH);
if (optPtr->priceType == zop_predef) /* fixed scheme, does not use statistics */
return WEIGHT(mlBase, optLevel)
+ ((16 + offCode) * BITCOST_MULTIPLIER); /* emulated offset cost */
/* dynamic statistics */
price = (offCode * BITCOST_MULTIPLIER) + (optPtr->offCodeSumBasePrice - WEIGHT(optPtr->offCodeFreq[offCode], optLevel));
if ((optLevel<2) /*static*/ && offCode >= 20)
price += (offCode-19)*2 * BITCOST_MULTIPLIER; /* handicap for long distance offsets, favor decompression speed */
/* match Length */
{ U32 const mlCode = ZSTD_MLcode(mlBase);
price += (ML_bits[mlCode] * BITCOST_MULTIPLIER) + (optPtr->matchLengthSumBasePrice - WEIGHT(optPtr->matchLengthFreq[mlCode], optLevel));
}
price += BITCOST_MULTIPLIER / 5; /* heuristic : make matches a bit more costly to favor less sequences -> faster decompression speed */
DEBUGLOG(8, "ZSTD_getMatchPrice(ml:%u) = %u", matchLength, price);
return price;
}
/* ZSTD_updateStats() :
* assumption : literals + litLength <= iend */
static void ZSTD_updateStats(optState_t* const optPtr,
U32 litLength, const BYTE* literals,
U32 offBase, U32 matchLength)
{
/* literals */
if (ZSTD_compressedLiterals(optPtr)) {
U32 u;
for (u=0; u < litLength; u++)
optPtr->litFreq[literals[u]] += ZSTD_LITFREQ_ADD;
optPtr->litSum += litLength*ZSTD_LITFREQ_ADD;
}
/* literal Length */
{ U32 const llCode = ZSTD_LLcode(litLength);
optPtr->litLengthFreq[llCode]++;
optPtr->litLengthSum++;
}
/* offset code : follows storeSeq() numeric representation */
{ U32 const offCode = ZSTD_highbit32(offBase);
assert(offCode <= MaxOff);
optPtr->offCodeFreq[offCode]++;
optPtr->offCodeSum++;
}
/* match Length */
{ U32 const mlBase = matchLength - MINMATCH;
U32 const mlCode = ZSTD_MLcode(mlBase);
optPtr->matchLengthFreq[mlCode]++;
optPtr->matchLengthSum++;
}
}
/* ZSTD_readMINMATCH() :
* function safe only for comparisons
* assumption : memPtr must be at least 4 bytes before end of buffer */
MEM_STATIC U32 ZSTD_readMINMATCH(const void* memPtr, U32 length)
{
switch (length)
{
default :
case 4 : return MEM_read32(memPtr);
case 3 : if (MEM_isLittleEndian())
return MEM_read32(memPtr)<<8;
else
return MEM_read32(memPtr)>>8;
}
}
/* Update hashTable3 up to ip (excluded)
Assumption : always within prefix (i.e. not within extDict) */
static U32 ZSTD_insertAndFindFirstIndexHash3 (const ZSTD_matchState_t* ms,
U32* nextToUpdate3,
const BYTE* const ip)
{
U32* const hashTable3 = ms->hashTable3;
U32 const hashLog3 = ms->hashLog3;
const BYTE* const base = ms->window.base;
U32 idx = *nextToUpdate3;
U32 const target = (U32)(ip - base);
size_t const hash3 = ZSTD_hash3Ptr(ip, hashLog3);
assert(hashLog3 > 0);
while(idx < target) {
hashTable3[ZSTD_hash3Ptr(base+idx, hashLog3)] = idx;
idx++;
}
*nextToUpdate3 = target;
return hashTable3[hash3];
}
/*-*************************************
* Binary Tree search
***************************************/
/** ZSTD_insertBt1() : add one or multiple positions to tree.
* @param ip assumed <= iend-8 .
* @param target The target of ZSTD_updateTree_internal() - we are filling to this position
* @return : nb of positions added */
static U32 ZSTD_insertBt1(
const ZSTD_matchState_t* ms,
const BYTE* const ip, const BYTE* const iend,
U32 const target,
U32 const mls, const int extDict)
{
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* const bt = ms->chainTable;
U32 const btLog = cParams->chainLog - 1;
U32 const btMask = (1 << btLog) - 1;
U32 matchIndex = hashTable[h];
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 dictEnd = dictBase + dictLimit;
const BYTE* const prefixStart = base + dictLimit;
const BYTE* match;
const U32 curr = (U32)(ip-base);
const U32 btLow = btMask >= curr ? 0 : curr - btMask;
U32* smallerPtr = bt + 2*(curr&btMask);
U32* largerPtr = smallerPtr + 1;
U32 dummy32; /* to be nullified at the end */
/* windowLow is based on target because
* we only need positions that will be in the window at the end of the tree update.
*/
U32 const windowLow = ZSTD_getLowestMatchIndex(ms, target, cParams->windowLog);
U32 matchEndIdx = curr+8+1;
size_t bestLength = 8;
U32 nbCompares = 1U << cParams->searchLog;
#ifdef ZSTD_C_PREDICT
U32 predictedSmall = *(bt + 2*((curr-1)&btMask) + 0);
U32 predictedLarge = *(bt + 2*((curr-1)&btMask) + 1);
predictedSmall += (predictedSmall>0);
predictedLarge += (predictedLarge>0);
#endif /* ZSTD_C_PREDICT */
DEBUGLOG(8, "ZSTD_insertBt1 (%u)", curr);
assert(curr <= target);
assert(ip <= iend-8); /* required for h calculation */
hashTable[h] = curr; /* Update Hash Table */
assert(windowLow > 0);
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);
#ifdef ZSTD_C_PREDICT /* note : can create issues when hlog small <= 11 */
const U32* predictPtr = bt + 2*((matchIndex-1) & btMask); /* written this way, as bt is a roll buffer */
if (matchIndex == predictedSmall) {
/* no need to check length, result known */
*smallerPtr = matchIndex;
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) */
predictedSmall = predictPtr[1] + (predictPtr[1]>0);
continue;
}
if (matchIndex == predictedLarge) {
*largerPtr = matchIndex;
if (matchIndex <= btLow) { largerPtr=&dummy32; break; } /* beyond tree size, stop the search */
largerPtr = nextPtr;
matchIndex = nextPtr[0];
predictedLarge = predictPtr[0] + (predictPtr[0]>0);
continue;
}
#endif
if (!extDict || (matchIndex+matchLength >= dictLimit)) {
assert(matchIndex+matchLength >= dictLimit); /* might be wrong if actually extDict */
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) {
bestLength = matchLength;
if (matchLength > matchEndIdx - matchIndex)
matchEndIdx = 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 */
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 */
largerPtr = nextPtr;
matchIndex = nextPtr[0];
} }
*smallerPtr = *largerPtr = 0;
{ U32 positions = 0;
if (bestLength > 384) positions = MIN(192, (U32)(bestLength - 384)); /* speed optimization */
assert(matchEndIdx > curr + 8);
return MAX(positions, matchEndIdx - (curr + 8));
}
}
FORCE_INLINE_TEMPLATE
void ZSTD_updateTree_internal(
ZSTD_matchState_t* ms,
const BYTE* const ip, const BYTE* const iend,
const U32 mls, const ZSTD_dictMode_e dictMode)
{
const BYTE* const base = ms->window.base;
U32 const target = (U32)(ip - base);
U32 idx = ms->nextToUpdate;
DEBUGLOG(6, "ZSTD_updateTree_internal, from %u to %u (dictMode:%u)",
idx, target, dictMode);
while(idx < target) {
U32 const forward = ZSTD_insertBt1(ms, base+idx, iend, target, mls, dictMode == ZSTD_extDict);
assert(idx < (U32)(idx + forward));
idx += forward;
}
assert((size_t)(ip - base) <= (size_t)(U32)(-1));
assert((size_t)(iend - base) <= (size_t)(U32)(-1));
ms->nextToUpdate = target;
}
void ZSTD_updateTree(ZSTD_matchState_t* ms, const BYTE* ip, const BYTE* iend) {
ZSTD_updateTree_internal(ms, ip, iend, ms->cParams.minMatch, ZSTD_noDict);
}
FORCE_INLINE_TEMPLATE U32
ZSTD_insertBtAndGetAllMatches (
ZSTD_match_t* matches, /* store result (found matches) in this table (presumed large enough) */
ZSTD_matchState_t* ms,
U32* nextToUpdate3,
const BYTE* const ip, const BYTE* const iLimit,
const ZSTD_dictMode_e dictMode,
const U32 rep[ZSTD_REP_NUM],
const U32 ll0, /* tells if associated literal length is 0 or not. This value must be 0 or 1 */
const U32 lengthToBeat,
const U32 mls /* template */)
{
const ZSTD_compressionParameters* const cParams = &ms->cParams;
U32 const sufficient_len = MIN(cParams->targetLength, ZSTD_OPT_NUM -1);
const BYTE* const base = ms->window.base;
U32 const curr = (U32)(ip-base);
U32 const hashLog = cParams->hashLog;
U32 const minMatch = (mls==3) ? 3 : 4;
U32* const hashTable = ms->hashTable;
size_t const h = ZSTD_hashPtr(ip, hashLog, mls);
U32 matchIndex = hashTable[h];
U32* const bt = ms->chainTable;
U32 const btLog = cParams->chainLog - 1;
U32 const btMask= (1U << btLog) - 1;
size_t commonLengthSmaller=0, commonLengthLarger=0;
const BYTE* const dictBase = ms->window.dictBase;
U32 const dictLimit = ms->window.dictLimit;
const BYTE* const dictEnd = dictBase + dictLimit;
const BYTE* const prefixStart = base + dictLimit;
U32 const btLow = (btMask >= curr) ? 0 : curr - btMask;
U32 const windowLow = ZSTD_getLowestMatchIndex(ms, curr, cParams->windowLog);
U32 const matchLow = windowLow ? windowLow : 1;
U32* smallerPtr = bt + 2*(curr&btMask);
U32* largerPtr = bt + 2*(curr&btMask) + 1;
U32 matchEndIdx = curr+8+1; /* farthest referenced position of any match => detects repetitive patterns */
U32 dummy32; /* to be nullified at the end */
U32 mnum = 0;
U32 nbCompares = 1U << cParams->searchLog;
const ZSTD_matchState_t* dms = dictMode == ZSTD_dictMatchState ? ms->dictMatchState : NULL;
const ZSTD_compressionParameters* const dmsCParams =
dictMode == ZSTD_dictMatchState ? &dms->cParams : NULL;
const BYTE* const dmsBase = dictMode == ZSTD_dictMatchState ? dms->window.base : NULL;
const BYTE* const dmsEnd = dictMode == ZSTD_dictMatchState ? dms->window.nextSrc : NULL;
U32 const dmsHighLimit = dictMode == ZSTD_dictMatchState ? (U32)(dmsEnd - dmsBase) : 0;
U32 const dmsLowLimit = dictMode == ZSTD_dictMatchState ? dms->window.lowLimit : 0;
U32 const dmsIndexDelta = dictMode == ZSTD_dictMatchState ? windowLow - dmsHighLimit : 0;
U32 const dmsHashLog = dictMode == ZSTD_dictMatchState ? dmsCParams->hashLog : hashLog;
U32 const dmsBtLog = dictMode == ZSTD_dictMatchState ? dmsCParams->chainLog - 1 : btLog;
U32 const dmsBtMask = dictMode == ZSTD_dictMatchState ? (1U << dmsBtLog) - 1 : 0;
U32 const dmsBtLow = dictMode == ZSTD_dictMatchState && dmsBtMask < dmsHighLimit - dmsLowLimit ? dmsHighLimit - dmsBtMask : dmsLowLimit;
size_t bestLength = lengthToBeat-1;
DEBUGLOG(8, "ZSTD_insertBtAndGetAllMatches: current=%u", curr);
/* check repCode */
assert(ll0 <= 1); /* necessarily 1 or 0 */
{ U32 const lastR = ZSTD_REP_NUM + ll0;
U32 repCode;
for (repCode = ll0; repCode < lastR; repCode++) {
U32 const repOffset = (repCode==ZSTD_REP_NUM) ? (rep[0] - 1) : rep[repCode];
U32 const repIndex = curr - repOffset;
U32 repLen = 0;
assert(curr >= dictLimit);
if (repOffset-1 /* intentional overflow, discards 0 and -1 */ < curr-dictLimit) { /* equivalent to `curr > repIndex >= dictLimit` */
/* We must validate the repcode offset because when we're using a dictionary the
* valid offset range shrinks when the dictionary goes out of bounds.
*/
if ((repIndex >= windowLow) & (ZSTD_readMINMATCH(ip, minMatch) == ZSTD_readMINMATCH(ip - repOffset, minMatch))) {
repLen = (U32)ZSTD_count(ip+minMatch, ip+minMatch-repOffset, iLimit) + minMatch;
}
} else { /* repIndex < dictLimit || repIndex >= curr */
const BYTE* const repMatch = dictMode == ZSTD_dictMatchState ?
dmsBase + repIndex - dmsIndexDelta :
dictBase + repIndex;
assert(curr >= windowLow);
if ( dictMode == ZSTD_extDict
&& ( ((repOffset-1) /*intentional overflow*/ < curr - windowLow) /* equivalent to `curr > repIndex >= windowLow` */
& (((U32)((dictLimit-1) - repIndex) >= 3) ) /* intentional overflow : do not test positions overlapping 2 memory segments */)
&& (ZSTD_readMINMATCH(ip, minMatch) == ZSTD_readMINMATCH(repMatch, minMatch)) ) {
repLen = (U32)ZSTD_count_2segments(ip+minMatch, repMatch+minMatch, iLimit, dictEnd, prefixStart) + minMatch;
}
if (dictMode == ZSTD_dictMatchState
&& ( ((repOffset-1) /*intentional overflow*/ < curr - (dmsLowLimit + dmsIndexDelta)) /* equivalent to `curr > repIndex >= dmsLowLimit` */
& ((U32)((dictLimit-1) - repIndex) >= 3) ) /* intentional overflow : do not test positions overlapping 2 memory segments */
&& (ZSTD_readMINMATCH(ip, minMatch) == ZSTD_readMINMATCH(repMatch, minMatch)) ) {
repLen = (U32)ZSTD_count_2segments(ip+minMatch, repMatch+minMatch, iLimit, dmsEnd, prefixStart) + minMatch;
} }
/* save longer solution */
if (repLen > bestLength) {
DEBUGLOG(8, "found repCode %u (ll0:%u, offset:%u) of length %u",
repCode, ll0, repOffset, repLen);
bestLength = repLen;
matches[mnum].off = REPCODE_TO_OFFBASE(repCode - ll0 + 1); /* expect value between 1 and 3 */
matches[mnum].len = (U32)repLen;
mnum++;
if ( (repLen > sufficient_len)
| (ip+repLen == iLimit) ) { /* best possible */
return mnum;
} } } }
/* HC3 match finder */
if ((mls == 3) /*static*/ && (bestLength < mls)) {
U32 const matchIndex3 = ZSTD_insertAndFindFirstIndexHash3(ms, nextToUpdate3, ip);
if ((matchIndex3 >= matchLow)
& (curr - matchIndex3 < (1<<18)) /*heuristic : longer distance likely too expensive*/ ) {
size_t mlen;
if ((dictMode == ZSTD_noDict) /*static*/ || (dictMode == ZSTD_dictMatchState) /*static*/ || (matchIndex3 >= dictLimit)) {
const BYTE* const match = base + matchIndex3;
mlen = ZSTD_count(ip, match, iLimit);
} else {
const BYTE* const match = dictBase + matchIndex3;
mlen = ZSTD_count_2segments(ip, match, iLimit, dictEnd, prefixStart);
}
/* save best solution */
if (mlen >= mls /* == 3 > bestLength */) {
DEBUGLOG(8, "found small match with hlog3, of length %u",
(U32)mlen);
bestLength = mlen;
assert(curr > matchIndex3);
assert(mnum==0); /* no prior solution */
matches[0].off = OFFSET_TO_OFFBASE(curr - matchIndex3);
matches[0].len = (U32)mlen;
mnum = 1;
if ( (mlen > sufficient_len) |
(ip+mlen == iLimit) ) { /* best possible length */
ms->nextToUpdate = curr+1; /* skip insertion */
return 1;
} } }
/* no dictMatchState lookup: dicts don't have a populated HC3 table */
} /* if (mls == 3) */
hashTable[h] = curr; /* Update Hash Table */
for (; nbCompares && (matchIndex >= matchLow); --nbCompares) {
U32* const nextPtr = bt + 2*(matchIndex & btMask);
const BYTE* match;
size_t matchLength = MIN(commonLengthSmaller, commonLengthLarger); /* guaranteed minimum nb of common bytes */
assert(curr > matchIndex);
if ((dictMode == ZSTD_noDict) || (dictMode == ZSTD_dictMatchState) || (matchIndex+matchLength >= dictLimit)) {
assert(matchIndex+matchLength >= dictLimit); /* ensure the condition is correct when !extDict */
match = base + matchIndex;
if (matchIndex >= dictLimit) assert(memcmp(match, ip, matchLength) == 0); /* ensure early section of match is equal as expected */
matchLength += ZSTD_count(ip+matchLength, match+matchLength, iLimit);
} else {
match = dictBase + matchIndex;
assert(memcmp(match, ip, matchLength) == 0); /* ensure early section of match is equal as expected */
matchLength += ZSTD_count_2segments(ip+matchLength, match+matchLength, iLimit, dictEnd, prefixStart);
if (matchIndex+matchLength >= dictLimit)
match = base + matchIndex; /* prepare for match[matchLength] read */
}
if (matchLength > bestLength) {
DEBUGLOG(8, "found match of length %u at distance %u (offBase=%u)",
(U32)matchLength, curr - matchIndex, OFFSET_TO_OFFBASE(curr - matchIndex));
assert(matchEndIdx > matchIndex);
if (matchLength > matchEndIdx - matchIndex)
matchEndIdx = matchIndex + (U32)matchLength;
bestLength = matchLength;
matches[mnum].off = OFFSET_TO_OFFBASE(curr - matchIndex);
matches[mnum].len = (U32)matchLength;
mnum++;
if ( (matchLength > ZSTD_OPT_NUM)
| (ip+matchLength == iLimit) /* equal : no way to know if inf or sup */) {
if (dictMode == ZSTD_dictMatchState) nbCompares = 0; /* break should also skip searching dms */
break; /* drop, to preserve bt consistency (miss a little bit of compression) */
} }
if (match[matchLength] < ip[matchLength]) {
/* match 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 candidate => larger than match, which was smaller than current */
matchIndex = nextPtr[1]; /* new matchIndex, larger than previous, closer to current */
} else {
*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) {
size_t const dmsH = ZSTD_hashPtr(ip, dmsHashLog, mls);
U32 dictMatchIndex = dms->hashTable[dmsH];
const U32* const dmsBt = dms->chainTable;
commonLengthSmaller = commonLengthLarger = 0;
for (; nbCompares && (dictMatchIndex > dmsLowLimit); --nbCompares) {
const U32* const nextPtr = dmsBt + 2*(dictMatchIndex & dmsBtMask);
size_t matchLength = MIN(commonLengthSmaller, commonLengthLarger); /* guaranteed minimum nb of common bytes */
const BYTE* match = dmsBase + dictMatchIndex;
matchLength += ZSTD_count_2segments(ip+matchLength, match+matchLength, iLimit, dmsEnd, prefixStart);
if (dictMatchIndex+matchLength >= dmsHighLimit)
match = base + dictMatchIndex + dmsIndexDelta; /* to prepare for next usage of match[matchLength] */
if (matchLength > bestLength) {
matchIndex = dictMatchIndex + dmsIndexDelta;
DEBUGLOG(8, "found dms match of length %u at distance %u (offBase=%u)",
(U32)matchLength, curr - matchIndex, OFFSET_TO_OFFBASE(curr - matchIndex));
if (matchLength > matchEndIdx - matchIndex)
matchEndIdx = matchIndex + (U32)matchLength;
bestLength = matchLength;
matches[mnum].off = OFFSET_TO_OFFBASE(curr - matchIndex);
matches[mnum].len = (U32)matchLength;
mnum++;
if ( (matchLength > ZSTD_OPT_NUM)
| (ip+matchLength == iLimit) /* equal : no way to know if inf or sup */) {
break; /* drop, to guarantee consistency (miss a little bit of compression) */
} }
if (dictMatchIndex <= dmsBtLow) { break; } /* beyond tree size, stop the search */
if (match[matchLength] < ip[matchLength]) {
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 */
commonLengthLarger = matchLength;
dictMatchIndex = nextPtr[0];
} } } /* if (dictMode == ZSTD_dictMatchState) */
assert(matchEndIdx > curr+8);
ms->nextToUpdate = matchEndIdx - 8; /* skip repetitive patterns */
return mnum;
}
typedef U32 (*ZSTD_getAllMatchesFn)(
ZSTD_match_t*,
ZSTD_matchState_t*,
U32*,
const BYTE*,
const BYTE*,
const U32 rep[ZSTD_REP_NUM],
U32 const ll0,
U32 const lengthToBeat);
FORCE_INLINE_TEMPLATE U32 ZSTD_btGetAllMatches_internal(
ZSTD_match_t* matches,
ZSTD_matchState_t* ms,
U32* nextToUpdate3,
const BYTE* ip,
const BYTE* const iHighLimit,
const U32 rep[ZSTD_REP_NUM],
U32 const ll0,
U32 const lengthToBeat,
const ZSTD_dictMode_e dictMode,
const U32 mls)
{
assert(BOUNDED(3, ms->cParams.minMatch, 6) == mls);
DEBUGLOG(8, "ZSTD_BtGetAllMatches(dictMode=%d, mls=%u)", (int)dictMode, mls);
if (ip < ms->window.base + ms->nextToUpdate)
return 0; /* skipped area */
ZSTD_updateTree_internal(ms, ip, iHighLimit, mls, dictMode);
return ZSTD_insertBtAndGetAllMatches(matches, ms, nextToUpdate3, ip, iHighLimit, dictMode, rep, ll0, lengthToBeat, mls);
}
#define ZSTD_BT_GET_ALL_MATCHES_FN(dictMode, mls) ZSTD_btGetAllMatches_##dictMode##_##mls
#define GEN_ZSTD_BT_GET_ALL_MATCHES_(dictMode, mls) \
static U32 ZSTD_BT_GET_ALL_MATCHES_FN(dictMode, mls)( \
ZSTD_match_t* matches, \
ZSTD_matchState_t* ms, \
U32* nextToUpdate3, \
const BYTE* ip, \
const BYTE* const iHighLimit, \
const U32 rep[ZSTD_REP_NUM], \
U32 const ll0, \
U32 const lengthToBeat) \
{ \
return ZSTD_btGetAllMatches_internal( \
matches, ms, nextToUpdate3, ip, iHighLimit, \
rep, ll0, lengthToBeat, ZSTD_##dictMode, mls); \
}
#define GEN_ZSTD_BT_GET_ALL_MATCHES(dictMode) \
GEN_ZSTD_BT_GET_ALL_MATCHES_(dictMode, 3) \
GEN_ZSTD_BT_GET_ALL_MATCHES_(dictMode, 4) \
GEN_ZSTD_BT_GET_ALL_MATCHES_(dictMode, 5) \
GEN_ZSTD_BT_GET_ALL_MATCHES_(dictMode, 6)
GEN_ZSTD_BT_GET_ALL_MATCHES(noDict)
GEN_ZSTD_BT_GET_ALL_MATCHES(extDict)
GEN_ZSTD_BT_GET_ALL_MATCHES(dictMatchState)
#define ZSTD_BT_GET_ALL_MATCHES_ARRAY(dictMode) \
{ \
ZSTD_BT_GET_ALL_MATCHES_FN(dictMode, 3), \
ZSTD_BT_GET_ALL_MATCHES_FN(dictMode, 4), \
ZSTD_BT_GET_ALL_MATCHES_FN(dictMode, 5), \
ZSTD_BT_GET_ALL_MATCHES_FN(dictMode, 6) \
}
static ZSTD_getAllMatchesFn
ZSTD_selectBtGetAllMatches(ZSTD_matchState_t const* ms, ZSTD_dictMode_e const dictMode)
{
ZSTD_getAllMatchesFn const getAllMatchesFns[3][4] = {
ZSTD_BT_GET_ALL_MATCHES_ARRAY(noDict),
ZSTD_BT_GET_ALL_MATCHES_ARRAY(extDict),
ZSTD_BT_GET_ALL_MATCHES_ARRAY(dictMatchState)
};
U32 const mls = BOUNDED(3, ms->cParams.minMatch, 6);
assert((U32)dictMode < 3);
assert(mls - 3 < 4);
return getAllMatchesFns[(int)dictMode][mls - 3];
}
/*************************
* LDM helper functions *
*************************/
/* Struct containing info needed to make decision about ldm inclusion */
typedef struct {
rawSeqStore_t seqStore; /* External match candidates store for this block */
U32 startPosInBlock; /* Start position of the current match candidate */
U32 endPosInBlock; /* End position of the current match candidate */
U32 offset; /* Offset of the match candidate */
} ZSTD_optLdm_t;
/* ZSTD_optLdm_skipRawSeqStoreBytes():
* Moves forward in @rawSeqStore by @nbBytes,
* which will update the fields 'pos' and 'posInSequence'.
*/
static void ZSTD_optLdm_skipRawSeqStoreBytes(rawSeqStore_t* rawSeqStore, size_t nbBytes)
{
U32 currPos = (U32)(rawSeqStore->posInSequence + nbBytes);
while (currPos && rawSeqStore->pos < rawSeqStore->size) {
rawSeq currSeq = rawSeqStore->seq[rawSeqStore->pos];
if (currPos >= currSeq.litLength + currSeq.matchLength) {
currPos -= currSeq.litLength + currSeq.matchLength;
rawSeqStore->pos++;
} else {
rawSeqStore->posInSequence = currPos;
break;
}
}
if (currPos == 0 || rawSeqStore->pos == rawSeqStore->size) {
rawSeqStore->posInSequence = 0;
}
}
/* ZSTD_opt_getNextMatchAndUpdateSeqStore():
* Calculates the beginning and end of the next match in the current block.
* Updates 'pos' and 'posInSequence' of the ldmSeqStore.
*/
static void
ZSTD_opt_getNextMatchAndUpdateSeqStore(ZSTD_optLdm_t* optLdm, U32 currPosInBlock,
U32 blockBytesRemaining)
{
rawSeq currSeq;
U32 currBlockEndPos;
U32 literalsBytesRemaining;
U32 matchBytesRemaining;
/* Setting match end position to MAX to ensure we never use an LDM during this block */
if (optLdm->seqStore.size == 0 || optLdm->seqStore.pos >= optLdm->seqStore.size) {
optLdm->startPosInBlock = UINT_MAX;
optLdm->endPosInBlock = UINT_MAX;
return;
}
/* Calculate appropriate bytes left in matchLength and litLength
* after adjusting based on ldmSeqStore->posInSequence */
currSeq = optLdm->seqStore.seq[optLdm->seqStore.pos];
assert(optLdm->seqStore.posInSequence <= currSeq.litLength + currSeq.matchLength);
currBlockEndPos = currPosInBlock + blockBytesRemaining;
literalsBytesRemaining = (optLdm->seqStore.posInSequence < currSeq.litLength) ?
currSeq.litLength - (U32)optLdm->seqStore.posInSequence :
0;
matchBytesRemaining = (literalsBytesRemaining == 0) ?
currSeq.matchLength - ((U32)optLdm->seqStore.posInSequence - currSeq.litLength) :
currSeq.matchLength;
/* If there are more literal bytes than bytes remaining in block, no ldm is possible */
if (literalsBytesRemaining >= blockBytesRemaining) {
optLdm->startPosInBlock = UINT_MAX;
optLdm->endPosInBlock = UINT_MAX;
ZSTD_optLdm_skipRawSeqStoreBytes(&optLdm->seqStore, blockBytesRemaining);
return;
}
/* Matches may be < MINMATCH by this process. In that case, we will reject them
when we are deciding whether or not to add the ldm */
optLdm->startPosInBlock = currPosInBlock + literalsBytesRemaining;
optLdm->endPosInBlock = optLdm->startPosInBlock + matchBytesRemaining;
optLdm->offset = currSeq.offset;
if (optLdm->endPosInBlock > currBlockEndPos) {
/* Match ends after the block ends, we can't use the whole match */
optLdm->endPosInBlock = currBlockEndPos;
ZSTD_optLdm_skipRawSeqStoreBytes(&optLdm->seqStore, currBlockEndPos - currPosInBlock);
} else {
/* Consume nb of bytes equal to size of sequence left */
ZSTD_optLdm_skipRawSeqStoreBytes(&optLdm->seqStore, literalsBytesRemaining + matchBytesRemaining);
}
}
/* ZSTD_optLdm_maybeAddMatch():
* Adds a match if it's long enough,
* based on it's 'matchStartPosInBlock' and 'matchEndPosInBlock',
* into 'matches'. Maintains the correct ordering of 'matches'.
*/
static void ZSTD_optLdm_maybeAddMatch(ZSTD_match_t* matches, U32* nbMatches,
const ZSTD_optLdm_t* optLdm, U32 currPosInBlock)
{
U32 const posDiff = currPosInBlock - optLdm->startPosInBlock;
/* Note: ZSTD_match_t actually contains offBase and matchLength (before subtracting MINMATCH) */
U32 const candidateMatchLength = optLdm->endPosInBlock - optLdm->startPosInBlock - posDiff;
/* Ensure that current block position is not outside of the match */
if (currPosInBlock < optLdm->startPosInBlock
|| currPosInBlock >= optLdm->endPosInBlock
|| candidateMatchLength < MINMATCH) {
return;
}
if (*nbMatches == 0 || ((candidateMatchLength > matches[*nbMatches-1].len) && *nbMatches < ZSTD_OPT_NUM)) {
U32 const candidateOffBase = OFFSET_TO_OFFBASE(optLdm->offset);
DEBUGLOG(6, "ZSTD_optLdm_maybeAddMatch(): Adding ldm candidate match (offBase: %u matchLength %u) at block position=%u",