/*

 * Copyright (c) 2016-present, 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_fast.h"

void ZSTD_fillHashTable(ZSTD_matchState_t* ms,

                        ZSTD_compressionParameters const* cParams,

                        void const* end)

{

    U32* const hashTable = ms->hashTable;

    U32  const hBits = cParams->hashLog;

    U32  const mls = cParams->searchLength;

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

    const BYTE* ip = base + ms->nextToUpdate;

    const BYTE* const iend = ((const BYTE*)end) - HASH_READ_SIZE;

    const U32 fastHashFillStep = 3;

    /* Always insert every fastHashFillStep position into the hash table.

     * Insert the other positions if their hash entry is empty.

     */

    for (; ip + fastHashFillStep - 1 <= iend; ip += fastHashFillStep) {

        U32 const current = (U32)(ip - base);

        U32 i;

        for (i = 0; i < fastHashFillStep; ++i) {

            size_t const hash = ZSTD_hashPtr(ip + i, hBits, mls);

            if (i == 0 || hashTable[hash] == 0)

                hashTable[hash] = current + i;

        }

    }

}

FORCE_INLINE_TEMPLATE

size_t ZSTD_compressBlock_fast_generic(

        ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],

        void const* src, size_t srcSize,

        U32 const hlog, U32 const stepSize, U32 const mls)

{

    U32* const hashTable = ms->hashTable;

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

    const BYTE* const istart = (const BYTE*)src;

    const BYTE* ip = istart;

    const BYTE* anchor = istart;

    const U32   lowestIndex = ms->window.dictLimit;

    const BYTE* const lowest = base + lowestIndex;

    const BYTE* const iend = istart + srcSize;

    const BYTE* const ilimit = iend - HASH_READ_SIZE;

    U32 offset_1=rep[0], offset_2=rep[1];

    U32 offsetSaved = 0;

    /* init */

    ip += (ip==lowest);

    {   U32 const maxRep = (U32)(ip-lowest);

        if (offset_2 > maxRep) offsetSaved = offset_2, offset_2 = 0;

        if (offset_1 > maxRep) offsetSaved = offset_1, offset_1 = 0;

    }

    /* Main Search Loop */

    while (ip < ilimit) {   /* < instead of <=, because repcode check at (ip+1) */

        size_t mLength;

        size_t const h = ZSTD_hashPtr(ip, hlog, mls);

        U32 const current = (U32)(ip-base);

        U32 const matchIndex = hashTable[h];

        const BYTE* match = base + matchIndex;

        hashTable[h] = current;   /* update hash table */

        if ((offset_1 > 0) & (MEM_read32(ip+1-offset_1) == MEM_read32(ip+1))) {

            mLength = ZSTD_count(ip+1+4, ip+1+4-offset_1, iend) + 4;

            ip++;

            ZSTD_storeSeq(seqStore, ip-anchor, anchor, 0, mLength-MINMATCH);

        } else {

            if ( (matchIndex <= lowestIndex)

              || (MEM_read32(match) != MEM_read32(ip)) ) {

                assert(stepSize >= 1);

                ip += ((ip-anchor) >> kSearchStrength) + stepSize;

                continue;

            }

            mLength = ZSTD_count(ip+4, match+4, iend) + 4;

            {   U32 const offset = (U32)(ip-match);

                while (((ip>anchor) & (match>lowest)) && (ip[-1] == match[-1])) { ip--; match--; mLength++; } /* catch up */

                offset_2 = offset_1;

                offset_1 = offset;

                ZSTD_storeSeq(seqStore, ip-anchor, anchor, offset + ZSTD_REP_MOVE, mLength-MINMATCH);

        }   }

        /* match found */

        ip += mLength;

        anchor = ip;

        if (ip <= ilimit) {

            /* Fill Table */

            hashTable[ZSTD_hashPtr(base+current+2, hlog, mls)] = current+2;  /* here because current+2 could be > iend-8 */

            hashTable[ZSTD_hashPtr(ip-2, hlog, mls)] = (U32)(ip-2-base);

            /* check immediate repcode */

            while ( (ip <= ilimit)

                 && ( (offset_2>0)

                 & (MEM_read32(ip) == MEM_read32(ip - offset_2)) )) {

                /* store sequence */

                size_t const rLength = ZSTD_count(ip+4, ip+4-offset_2, iend) + 4;

                { U32 const tmpOff = offset_2; offset_2 = offset_1; offset_1 = tmpOff; }  /* swap offset_2 <=> offset_1 */

                hashTable[ZSTD_hashPtr(ip, hlog, mls)] = (U32)(ip-base);

                ZSTD_storeSeq(seqStore, 0, anchor, 0, rLength-MINMATCH);

                ip += rLength;

                anchor = ip;

                continue;   /* faster when present ... (?) */

    }   }   }

    /* save reps for next block */

    rep[0] = offset_1 ? offset_1 : offsetSaved;

    rep[1] = offset_2 ? offset_2 : offsetSaved;

    /* Return the last literals size */

    return iend - anchor;

}

size_t ZSTD_compressBlock_fast(

        ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],

        ZSTD_compressionParameters const* cParams, void const* src, size_t srcSize)

{

    U32 const hlog = cParams->hashLog;

    U32 const mls = cParams->searchLength;

    U32 const stepSize = cParams->targetLength;

    switch(mls)

    {

    default: /* includes case 3 */

    case 4 :

        return ZSTD_compressBlock_fast_generic(ms, seqStore, rep, src, srcSize, hlog, stepSize, 4);

    case 5 :

        return ZSTD_compressBlock_fast_generic(ms, seqStore, rep, src, srcSize, hlog, stepSize, 5);

    case 6 :

        return ZSTD_compressBlock_fast_generic(ms, seqStore, rep, src, srcSize, hlog, stepSize, 6);

    case 7 :

        return ZSTD_compressBlock_fast_generic(ms, seqStore, rep, src, srcSize, hlog, stepSize, 7);

    }

}

static size_t ZSTD_compressBlock_fast_extDict_generic(

        ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],

        void const* src, size_t srcSize,

        U32 const hlog, U32 const stepSize, U32 const mls)

{

    U32* hashTable = ms->hashTable;

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

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

    const BYTE* const istart = (const BYTE*)src;

    const BYTE* ip = istart;

    const BYTE* anchor = istart;

    const U32   lowestIndex = ms->window.lowLimit;

    const BYTE* const dictStart = dictBase + lowestIndex;

    const U32   dictLimit = ms->window.dictLimit;

    const BYTE* const lowPrefixPtr = base + dictLimit;

    const BYTE* const dictEnd = dictBase + dictLimit;

    const BYTE* const iend = istart + srcSize;

    const BYTE* const ilimit = iend - 8;

    U32 offset_1=rep[0], offset_2=rep[1];

    /* Search Loop */

    while (ip < ilimit) {  /* < instead of <=, because (ip+1) */

        const size_t h = ZSTD_hashPtr(ip, hlog, mls);

        const U32 matchIndex = hashTable[h];

        const BYTE* matchBase = matchIndex < dictLimit ? dictBase : base;

        const BYTE* match = matchBase + matchIndex;

        const U32 current = (U32)(ip-base);

        const U32 repIndex = current + 1 - offset_1;   /* offset_1 expected <= current +1 */

        const BYTE* repBase = repIndex < dictLimit ? dictBase : base;

        const BYTE* repMatch = repBase + repIndex;

        size_t mLength;

        hashTable[h] = current;   /* update hash table */

        if ( (((U32)((dictLimit-1) - repIndex) >= 3) /* intentional underflow */ & (repIndex > lowestIndex))

           && (MEM_read32(repMatch) == MEM_read32(ip+1)) ) {

            const BYTE* repMatchEnd = repIndex < dictLimit ? dictEnd : iend;

            mLength = ZSTD_count_2segments(ip+1+4, repMatch+4, iend, repMatchEnd, lowPrefixPtr) + 4;

            ip++;

            ZSTD_storeSeq(seqStore, ip-anchor, anchor, 0, mLength-MINMATCH);

        } else {

            if ( (matchIndex < lowestIndex) ||

                 (MEM_read32(match) != MEM_read32(ip)) ) {

                assert(stepSize >= 1);

                ip += ((ip-anchor) >> kSearchStrength) + stepSize;

                continue;

            }

            {   const BYTE* matchEnd = matchIndex < dictLimit ? dictEnd : iend;

                const BYTE* lowMatchPtr = matchIndex < dictLimit ? dictStart : lowPrefixPtr;

                U32 offset;

                mLength = ZSTD_count_2segments(ip+4, match+4, iend, matchEnd, lowPrefixPtr) + 4;

                while (((ip>anchor) & (match>lowMatchPtr)) && (ip[-1] == match[-1])) { ip--; match--; mLength++; }   /* catch up */

                offset = current - matchIndex;

                offset_2 = offset_1;

                offset_1 = offset;

                ZSTD_storeSeq(seqStore, ip-anchor, anchor, offset + ZSTD_REP_MOVE, mLength-MINMATCH);

        }   }

        /* found a match : store it */

        ip += mLength;

        anchor = ip;

        if (ip <= ilimit) {

            /* Fill Table */

            hashTable[ZSTD_hashPtr(base+current+2, hlog, mls)] = current+2;

            hashTable[ZSTD_hashPtr(ip-2, hlog, mls)] = (U32)(ip-2-base);

            /* check immediate repcode */

            while (ip <= ilimit) {

                U32 const current2 = (U32)(ip-base);

                U32 const repIndex2 = current2 - offset_2;

                const BYTE* repMatch2 = repIndex2 < dictLimit ? dictBase + repIndex2 : base + repIndex2;

                if ( (((U32)((dictLimit-1) - repIndex2) >= 3) & (repIndex2 > lowestIndex))  /* intentional overflow */

                   && (MEM_read32(repMatch2) == MEM_read32(ip)) ) {

                    const BYTE* const repEnd2 = repIndex2 < dictLimit ? dictEnd : iend;

                    size_t const repLength2 = ZSTD_count_2segments(ip+4, repMatch2+4, iend, repEnd2, lowPrefixPtr) + 4;

                    U32 tmpOffset = offset_2; offset_2 = offset_1; offset_1 = tmpOffset;   /* swap offset_2 <=> offset_1 */

                    ZSTD_storeSeq(seqStore, 0, anchor, 0, repLength2-MINMATCH);

                    hashTable[ZSTD_hashPtr(ip, hlog, mls)] = current2;

                    ip += repLength2;

                    anchor = ip;

                    continue;

                }

                break;

    }   }   }

    /* save reps for next block */

    rep[0] = offset_1;

    rep[1] = offset_2;

    /* Return the last literals size */

    return iend - anchor;

}

size_t ZSTD_compressBlock_fast_extDict(

        ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],

        ZSTD_compressionParameters const* cParams, void const* src, size_t srcSize)

{

    U32 const hlog = cParams->hashLog;

    U32 const mls = cParams->searchLength;

    U32 const stepSize = cParams->targetLength;

    switch(mls)

    {

    default: /* includes case 3 */

    case 4 :

        return ZSTD_compressBlock_fast_extDict_generic(ms, seqStore, rep, src, srcSize, hlog, stepSize, 4);

    case 5 :

        return ZSTD_compressBlock_fast_extDict_generic(ms, seqStore, rep, src, srcSize, hlog, stepSize, 5);

    case 6 :

        return ZSTD_compressBlock_fast_extDict_generic(ms, seqStore, rep, src, srcSize, hlog, stepSize, 6);

    case 7 :

        return ZSTD_compressBlock_fast_extDict_generic(ms, seqStore, rep, src, srcSize, hlog, stepSize, 7);

    }

}