/*

 * 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"

#if !defined(ZSTD_EXCLUDE_BTLAZY2_BLOCK_COMPRESSOR) \

 || !defined(ZSTD_EXCLUDE_BTOPT_BLOCK_COMPRESSOR) \

 || !defined(ZSTD_EXCLUDE_BTULTRA_BLOCK_COMPRESSOR)

#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)

{

    DEBUGLOG(8, "ZSTD_rawLiteralsCost (%u literals)", litLength);

    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

ZSTD_ALLOW_POINTER_OVERFLOW_ATTR

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

ZSTD_ALLOW_POINTER_OVERFLOW_ATTR

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

ZSTD_ALLOW_POINTER_OVERFLOW_ATTR

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(7, "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

ZSTD_ALLOW_POINTER_OVERFLOW_ATTR

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` */

                     & (ZSTD_index_overlap_check(dictLimit, repIndex)) )

                  && (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` */

                     & (ZSTD_index_overlap_check(dictLimit, repIndex)) )

                  && (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

ZSTD_ALLOW_POINTER_OVERFLOW_ATTR

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); \

    }

zstd_opt.c:ZSTD_btGetAllMatches_noDict_3

Line

Count

Source

864

122M

    {                                                          \

865

122M

        return ZSTD_btGetAllMatches_internal(                  \

866

122M

                matches, ms, nextToUpdate3, ip, iHighLimit,    \

867

122M

                rep, ll0, lengthToBeat, ZSTD_##dictMode, mls); \

868

122M

    }

zstd_opt.c:ZSTD_btGetAllMatches_noDict_4

Line

Count

Source

864

21.6M

    {                                                          \

865

21.6M

        return ZSTD_btGetAllMatches_internal(                  \

866

21.6M

                matches, ms, nextToUpdate3, ip, iHighLimit,    \

867

21.6M

                rep, ll0, lengthToBeat, ZSTD_##dictMode, mls); \

868

21.6M

    }

zstd_opt.c:ZSTD_btGetAllMatches_noDict_5

Line

Count

Source

864

20.5M

    {                                                          \

865

20.5M

        return ZSTD_btGetAllMatches_internal(                  \

866

20.5M

                matches, ms, nextToUpdate3, ip, iHighLimit,    \

867

20.5M

                rep, ll0, lengthToBeat, ZSTD_##dictMode, mls); \

868

20.5M

    }

Unexecuted instantiation: zstd_opt.c:ZSTD_btGetAllMatches_noDict_6

Unexecuted instantiation: zstd_opt.c:ZSTD_btGetAllMatches_extDict_3

Unexecuted instantiation: zstd_opt.c:ZSTD_btGetAllMatches_extDict_4

Unexecuted instantiation: zstd_opt.c:ZSTD_btGetAllMatches_extDict_5

Unexecuted instantiation: zstd_opt.c:ZSTD_btGetAllMatches_extDict_6

Unexecuted instantiation: zstd_opt.c:ZSTD_btGetAllMatches_dictMatchState_3

Unexecuted instantiation: zstd_opt.c:ZSTD_btGetAllMatches_dictMatchState_4

Unexecuted instantiation: zstd_opt.c:ZSTD_btGetAllMatches_dictMatchState_5

Unexecuted instantiation: zstd_opt.c:ZSTD_btGetAllMatches_dictMatchState_6

#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 */