/*

 * Copyright (c) 2016-present, Przemyslaw Skibinski, Yann Collet, Facebook, Inc.

 * 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_opt.h"

#define ZSTD_LITFREQ_ADD    2   /* scaling factor for litFreq, so that frequencies adapt faster to new stats. Also used for matchSum (?) */

#define ZSTD_FREQ_DIV       4   /* log factor when using previous stats to init next stats */

#define ZSTD_MAX_PRICE     (1<<30)

/*-*************************************

*  Price functions for optimal parser

***************************************/

static void ZSTD_setLog2Prices(optState_t* optPtr)

{

    optPtr->log2litSum = ZSTD_highbit32(optPtr->litSum+1);

    optPtr->log2litLengthSum = ZSTD_highbit32(optPtr->litLengthSum+1);

    optPtr->log2matchLengthSum = ZSTD_highbit32(optPtr->matchLengthSum+1);

    optPtr->log2offCodeSum = ZSTD_highbit32(optPtr->offCodeSum+1);

}

static void ZSTD_rescaleFreqs(optState_t* const optPtr,

                              const BYTE* const src, size_t const srcSize)

{

    optPtr->staticPrices = 0;

    if (optPtr->litLengthSum == 0) {  /* first init */

        unsigned u;

        if (srcSize <= 1024) optPtr->staticPrices = 1;

        assert(optPtr->litFreq!=NULL);

        for (u=0; u<=MaxLit; u++)

            optPtr->litFreq[u] = 0;

        for (u=0; u<srcSize; u++)

            optPtr->litFreq[src[u]]++;

        optPtr->litSum = 0;

        for (u=0; u<=MaxLit; u++) {

            optPtr->litFreq[u] = 1 + (optPtr->litFreq[u] >> ZSTD_FREQ_DIV);

            optPtr->litSum += optPtr->litFreq[u];

        }

        for (u=0; u<=MaxLL; u++)

            optPtr->litLengthFreq[u] = 1;

        optPtr->litLengthSum = MaxLL+1;

        for (u=0; u<=MaxML; u++)

            optPtr->matchLengthFreq[u] = 1;

        optPtr->matchLengthSum = MaxML+1;

        for (u=0; u<=MaxOff; u++)

            optPtr->offCodeFreq[u] = 1;

        optPtr->offCodeSum = (MaxOff+1);

    } else {

        unsigned u;

        optPtr->litSum = 0;

        for (u=0; u<=MaxLit; u++) {

            optPtr->litFreq[u] = 1 + (optPtr->litFreq[u] >> (ZSTD_FREQ_DIV+1));

            optPtr->litSum += optPtr->litFreq[u];

        }

        optPtr->litLengthSum = 0;

        for (u=0; u<=MaxLL; u++) {

            optPtr->litLengthFreq[u] = 1 + (optPtr->litLengthFreq[u]>>(ZSTD_FREQ_DIV+1));

            optPtr->litLengthSum += optPtr->litLengthFreq[u];

        }

        optPtr->matchLengthSum = 0;

        for (u=0; u<=MaxML; u++) {

            optPtr->matchLengthFreq[u] = 1 + (optPtr->matchLengthFreq[u]>>ZSTD_FREQ_DIV);

            optPtr->matchLengthSum += optPtr->matchLengthFreq[u];

        }

        optPtr->offCodeSum = 0;

        for (u=0; u<=MaxOff; u++) {

            optPtr->offCodeFreq[u] = 1 + (optPtr->offCodeFreq[u]>>ZSTD_FREQ_DIV);

            optPtr->offCodeSum += optPtr->offCodeFreq[u];

        }

    }

    ZSTD_setLog2Prices(optPtr);

}

/* ZSTD_rawLiteralsCost() :

 * cost of literals (only) in given segment (which length can be null)

 * does not include cost of literalLength symbol */

static U32 ZSTD_rawLiteralsCost(const BYTE* const literals, U32 const litLength,

                                const optState_t* const optPtr)

{

    if (optPtr->staticPrices) return (litLength*6);  /* 6 bit per literal - no statistic used */

    if (litLength == 0) return 0;

    /* literals */

    {   U32 u;

        U32 cost = litLength * optPtr->log2litSum;

        for (u=0; u < litLength; u++)

            cost -= ZSTD_highbit32(optPtr->litFreq[literals[u]]+1);

        return cost;

    }

}

/* ZSTD_litLengthPrice() :

 * cost of literalLength symbol */

static U32 ZSTD_litLengthPrice(U32 const litLength, const optState_t* const optPtr)

{

    if (optPtr->staticPrices) return ZSTD_highbit32((U32)litLength+1);

    /* literal Length */

    {   U32 const llCode = ZSTD_LLcode(litLength);

        U32 const price = LL_bits[llCode] + optPtr->log2litLengthSum - ZSTD_highbit32(optPtr->litLengthFreq[llCode]+1);

        return price;

    }

}

/* ZSTD_litLengthPrice() :

 * cost of the literal part of a sequence,

 * including literals themselves, and literalLength symbol */

static U32 ZSTD_fullLiteralsCost(const BYTE* const literals, U32 const litLength,

                                 const optState_t* const optPtr)

{

    return ZSTD_rawLiteralsCost(literals, litLength, optPtr)

         + ZSTD_litLengthPrice(litLength, optPtr);

}

/* ZSTD_litLengthContribution() :

 * @return ( cost(litlength) - cost(0) )

 * this value can then be added to rawLiteralsCost()

 * to provide a cost which is directly comparable to a match ending at same position */

static int ZSTD_litLengthContribution(U32 const litLength, const optState_t* const optPtr)

{

    if (optPtr->staticPrices) return ZSTD_highbit32(litLength+1);

    /* literal Length */

    {   U32 const llCode = ZSTD_LLcode(litLength);

        int const contribution = LL_bits[llCode]

                        + ZSTD_highbit32(optPtr->litLengthFreq[0]+1)

                        - ZSTD_highbit32(optPtr->litLengthFreq[llCode]+1);

#if 1

        return contribution;

#else

        return MAX(0, contribution); /* sometimes better, sometimes not ... */

#endif

    }

}

/* ZSTD_literalsContribution() :

 * creates a fake cost for the literals part of a sequence

 * which can be compared to the ending cost of a match

 * should a new match start at this position */

static int ZSTD_literalsContribution(const BYTE* const literals, U32 const litLength,

                                     const optState_t* const optPtr)

{

    int const contribution = ZSTD_rawLiteralsCost(literals, litLength, optPtr)

                           + ZSTD_litLengthContribution(litLength, optPtr);

    return contribution;

}

/* 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.

 * optLevel: when <2, favors small offset for decompression speed (improved cache efficiency) */

FORCE_INLINE_TEMPLATE U32 ZSTD_getMatchPrice(

                                    U32 const offset, U32 const matchLength,

                                    const optState_t* const optPtr,

                                    int const optLevel)

{

    U32 price;

    U32 const offCode = ZSTD_highbit32(offset+1);

    U32 const mlBase = matchLength - MINMATCH;

    assert(matchLength >= MINMATCH);

    if (optPtr->staticPrices)  /* fixed scheme, do not use statistics */

        return ZSTD_highbit32((U32)mlBase+1) + 16 + offCode;

    price = offCode + optPtr->log2offCodeSum - ZSTD_highbit32(optPtr->offCodeFreq[offCode]+1);

    if ((optLevel<2) /*static*/ && offCode >= 20) price += (offCode-19)*2; /* handicap for long distance offsets, favor decompression speed */

    /* match Length */

    {   U32 const mlCode = ZSTD_MLcode(mlBase);

        price += ML_bits[mlCode] + optPtr->log2matchLengthSum - ZSTD_highbit32(optPtr->matchLengthFreq[mlCode]+1);

    }

    DEBUGLOG(8, "ZSTD_getMatchPrice(ml:%u) = %u", matchLength, price);

    return price;

}

static void ZSTD_updateStats(optState_t* const optPtr,

                             U32 litLength, const BYTE* literals,

                             U32 offsetCode, U32 matchLength)

{

    /* literals */

    {   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++;

    }

    /* match offset code (0-2=>repCode; 3+=>offset+2) */

    {   U32 const offCode = ZSTD_highbit32(offsetCode+1);

        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 (ZSTD_matchState_t* ms, const BYTE* const ip)

{

    U32* const hashTable3 = ms->hashTable3;

    U32 const hashLog3 = ms->hashLog3;

    const BYTE* const base = ms->window.base;

    U32 idx = ms->nextToUpdate3;

    U32 const target = ms->nextToUpdate3 = (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++;

    }

    return hashTable3[hash3];

}

/*-*************************************

*  Binary Tree search

***************************************/

/** ZSTD_insertBt1() : add one or multiple positions to tree.

 *  ip : assumed <= iend-8 .

 * @return : nb of positions added */

static U32 ZSTD_insertBt1(

                ZSTD_matchState_t* ms, ZSTD_compressionParameters const* cParams,

                const BYTE* const ip, const BYTE* const iend,

                U32 const mls, U32 const extDict)

{

    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 current = (U32)(ip-base);

    const U32 btLow = btMask >= current ? 0 : current - btMask;

    U32* smallerPtr = bt + 2*(current&btMask);

    U32* largerPtr  = smallerPtr + 1;

    U32 dummy32;   /* to be nullified at the end */

    U32 const windowLow = ms->window.lowLimit;

    U32 matchEndIdx = current+8+1;

    size_t bestLength = 8;

    U32 nbCompares = 1U << cParams->searchLog;

#ifdef ZSTD_C_PREDICT

    U32 predictedSmall = *(bt + 2*((current-1)&btMask) + 0);

    U32 predictedLarge = *(bt + 2*((current-1)&btMask) + 1);

    predictedSmall += (predictedSmall>0);

    predictedLarge += (predictedLarge>0);

#endif /* ZSTD_C_PREDICT */

    DEBUGLOG(8, "ZSTD_insertBt1 (%u)", current);

    assert(ip <= iend-8);   /* required for h calculation */

    hashTable[h] = current;   /* Update Hash Table */

    while (nbCompares-- && (matchIndex > windowLow)) {

        U32* const nextPtr = bt + 2*(matchIndex & btMask);

        size_t matchLength = MIN(commonLengthSmaller, commonLengthLarger);   /* guaranteed minimum nb of common bytes */

        assert(matchIndex < current);

#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 extDict is incorrectly set to 0 */

            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;

    if (bestLength > 384) return MIN(192, (U32)(bestLength - 384));   /* speed optimization */

    assert(matchEndIdx > current + 8);

    return matchEndIdx - (current + 8);

}

FORCE_INLINE_TEMPLATE

void ZSTD_updateTree_internal(

                ZSTD_matchState_t* ms, ZSTD_compressionParameters const* cParams,

                const BYTE* const ip, const BYTE* const iend,

                const U32 mls, const U32 extDict)

{

    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  (extDict:%u)",

                idx, target, extDict);

    while(idx < target)

        idx += ZSTD_insertBt1(ms, cParams, base+idx, iend, mls, extDict);

    ms->nextToUpdate = target;

}

void ZSTD_updateTree(

                ZSTD_matchState_t* ms, ZSTD_compressionParameters const* cParams,

                const BYTE* ip, const BYTE* iend)

{

    ZSTD_updateTree_internal(ms, cParams, ip, iend, cParams->searchLength, 0 /*extDict*/);

}

FORCE_INLINE_TEMPLATE

U32 ZSTD_insertBtAndGetAllMatches (

                    ZSTD_matchState_t* ms, ZSTD_compressionParameters const* cParams,

                    const BYTE* const ip, const BYTE* const iLimit, int const extDict,

                    U32 rep[ZSTD_REP_NUM], U32 const ll0,

                    ZSTD_match_t* matches, const U32 lengthToBeat, U32 const mls /* template */)

{

    U32 const sufficient_len = MIN(cParams->targetLength, ZSTD_OPT_NUM -1);

    const BYTE* const base = ms->window.base;

    U32 const current = (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 >= current ? 0 : current - btMask;

    U32 const windowLow = ms->window.lowLimit;

    U32* smallerPtr = bt + 2*(current&btMask);

    U32* largerPtr  = bt + 2*(current&btMask) + 1;

    U32 matchEndIdx = current+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;

    size_t bestLength = lengthToBeat-1;

    DEBUGLOG(7, "ZSTD_insertBtAndGetAllMatches");

    /* check repCode */

    {   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 = current - repOffset;

            U32 repLen = 0;

            assert(current >= dictLimit);

            if (repOffset-1 /* intentional overflow, discards 0 and -1 */ < current-dictLimit) {  /* equivalent to `current > repIndex >= dictLimit` */

                if (ZSTD_readMINMATCH(ip, minMatch) == ZSTD_readMINMATCH(ip - repOffset, minMatch)) {

                    repLen = (U32)ZSTD_count(ip+minMatch, ip+minMatch-repOffset, iLimit) + minMatch;

                }

            } else {  /* repIndex < dictLimit || repIndex >= current */

                const BYTE* const repMatch = dictBase + repIndex;

                assert(current >= windowLow);

                if ( extDict /* this case only valid in extDict mode */

                  && ( ((repOffset-1) /*intentional overflow*/ < current - windowLow)  /* equivalent to `current > 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;

            }   }

            /* save longer solution */

            if (repLen > bestLength) {

                DEBUGLOG(8, "found rep-match %u of length %u",

                            repCode - ll0, (U32)repLen);

                bestLength = repLen;

                matches[mnum].off = repCode - ll0;

                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, ip);

        if ((matchIndex3 > windowLow)

          & (current - matchIndex3 < (1<<18)) /*heuristic : longer distance likely too expensive*/ ) {

            size_t mlen;

            if ((!extDict) /*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(current > matchIndex3);

                assert(mnum==0);  /* no prior solution */

                matches[0].off = (current - matchIndex3) + ZSTD_REP_MOVE;

                matches[0].len = (U32)mlen;

                mnum = 1;

                if ( (mlen > sufficient_len) |

                     (ip+mlen == iLimit) ) {  /* best possible length */

                    ms->nextToUpdate = current+1;  /* skip insertion */

                    return 1;

    }   }   }   }

    hashTable[h] = current;   /* Update Hash Table */

    while (nbCompares-- && (matchIndex > windowLow)) {

        U32* const nextPtr = bt + 2*(matchIndex & btMask);

        size_t matchLength = MIN(commonLengthSmaller, commonLengthLarger);   /* guaranteed minimum nb of common bytes */

        const BYTE* match;

        assert(current > matchIndex);

        if ((!extDict) || (matchIndex+matchLength >= dictLimit)) {

            assert(matchIndex+matchLength >= dictLimit);  /* ensure the condition is correct when !extDict */

            match = base + matchIndex;

            matchLength += ZSTD_count(ip+matchLength, match+matchLength, iLimit);

        } else {

            match = dictBase + matchIndex;

            matchLength += ZSTD_count_2segments(ip+matchLength, match+matchLength, iLimit, dictEnd, prefixStart);

            if (matchIndex+matchLength >= dictLimit)

                match = base + matchIndex;   /* prepare for match[matchLength] */

        }

        if (matchLength > bestLength) {

            DEBUGLOG(8, "found match of length %u at distance %u",

                    (U32)matchLength, current - matchIndex);

            assert(matchEndIdx > matchIndex);

            if (matchLength > matchEndIdx - matchIndex)

                matchEndIdx = matchIndex + (U32)matchLength;

            bestLength = matchLength;

            matches[mnum].off = (current - matchIndex) + ZSTD_REP_MOVE;