zstd/lib/compress/zstd_double_fast.c

/*
 * 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_double_fast.h"


void ZSTD_fillDoubleHashTable(ZSTD_CCtx* cctx, const void* end, const U32 mls)
{
    U32* const hashLarge = cctx->hashTable;
    U32  const hBitsL = cctx->appliedParams.cParams.hashLog;
    U32* const hashSmall = cctx->chainTable;
    U32  const hBitsS = cctx->appliedParams.cParams.chainLog;
    const BYTE* const base = cctx->base;
    const BYTE* ip = base + cctx->nextToUpdate;
    const BYTE* const iend = ((const BYTE*)end) - HASH_READ_SIZE;
    const size_t fastHashFillStep = 3;

    while(ip <= iend) {
        hashSmall[ZSTD_hashPtr(ip, hBitsS, mls)] = (U32)(ip - base);
        hashLarge[ZSTD_hashPtr(ip, hBitsL, 8)] = (U32)(ip - base);
        ip += fastHashFillStep;
    }
}


FORCE_INLINE_TEMPLATE
size_t ZSTD_compressBlock_doubleFast_generic(ZSTD_CCtx* cctx,
                                 const void* src, size_t srcSize,
                                 const U32 mls)
{
    U32* const hashLong = cctx->hashTable;
    const U32 hBitsL = cctx->appliedParams.cParams.hashLog;
    U32* const hashSmall = cctx->chainTable;
    const U32 hBitsS = cctx->appliedParams.cParams.chainLog;
    seqStore_t* seqStorePtr = &(cctx->seqStore);
    const BYTE* const base = cctx->base;
    const BYTE* const istart = (const BYTE*)src;
    const BYTE* ip = istart;
    const BYTE* anchor = istart;
    const U32 lowestIndex = cctx->dictLimit;
    const BYTE* const lowest = base + lowestIndex;
    const BYTE* const iend = istart + srcSize;
    const BYTE* const ilimit = iend - HASH_READ_SIZE;
    U32 offset_1=seqStorePtr->rep[0], offset_2=seqStorePtr->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 h2 = ZSTD_hashPtr(ip, hBitsL, 8);
        size_t const h = ZSTD_hashPtr(ip, hBitsS, mls);
        U32 const current = (U32)(ip-base);
        U32 const matchIndexL = hashLong[h2];
        U32 const matchIndexS = hashSmall[h];
        const BYTE* matchLong = base + matchIndexL;
        const BYTE* match = base + matchIndexS;
        hashLong[h2] = hashSmall[h] = current;   /* update hash tables */

        assert(offset_1 <= current);   /* supposed guaranteed by construction */
        if ((offset_1 > 0) & (MEM_read32(ip+1-offset_1) == MEM_read32(ip+1))) {
            /* favor repcode */
            mLength = ZSTD_count(ip+1+4, ip+1+4-offset_1, iend) + 4;
            ip++;
            ZSTD_storeSeq(seqStorePtr, ip-anchor, anchor, 0, mLength-MINMATCH);
        } else {
            U32 offset;
            if ( (matchIndexL > lowestIndex) && (MEM_read64(matchLong) == MEM_read64(ip)) ) {
                mLength = ZSTD_count(ip+8, matchLong+8, iend) + 8;
                offset = (U32)(ip-matchLong);
                while (((ip>anchor) & (matchLong>lowest)) && (ip[-1] == matchLong[-1])) { ip--; matchLong--; mLength++; } /* catch up */
            } else if ( (matchIndexS > lowestIndex) && (MEM_read32(match) == MEM_read32(ip)) ) {
                size_t const hl3 = ZSTD_hashPtr(ip+1, hBitsL, 8);
                U32 const matchIndexL3 = hashLong[hl3];
                const BYTE* matchL3 = base + matchIndexL3;
                hashLong[hl3] = current + 1;
                if ( (matchIndexL3 > lowestIndex) && (MEM_read64(matchL3) == MEM_read64(ip+1)) ) {
                    mLength = ZSTD_count(ip+9, matchL3+8, iend) + 8;
                    ip++;
                    offset = (U32)(ip-matchL3);
                    while (((ip>anchor) & (matchL3>lowest)) && (ip[-1] == matchL3[-1])) { ip--; matchL3--; mLength++; } /* catch up */
                } else {
                    mLength = ZSTD_count(ip+4, match+4, iend) + 4;
                    offset = (U32)(ip-match);
                    while (((ip>anchor) & (match>lowest)) && (ip[-1] == match[-1])) { ip--; match--; mLength++; } /* catch up */
                }
            } else {
                ip += ((ip-anchor) >> g_searchStrength) + 1;
                continue;
            }

            offset_2 = offset_1;
            offset_1 = offset;

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

        /* match found */
        ip += mLength;
        anchor = ip;

        if (ip <= ilimit) {
            /* Fill Table */
            hashLong[ZSTD_hashPtr(base+current+2, hBitsL, 8)] =
                hashSmall[ZSTD_hashPtr(base+current+2, hBitsS, mls)] = current+2;  /* here because current+2 could be > iend-8 */
            hashLong[ZSTD_hashPtr(ip-2, hBitsL, 8)] =
                hashSmall[ZSTD_hashPtr(ip-2, hBitsS, 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 */
                hashSmall[ZSTD_hashPtr(ip, hBitsS, mls)] = (U32)(ip-base);
                hashLong[ZSTD_hashPtr(ip, hBitsL, 8)] = (U32)(ip-base);
                ZSTD_storeSeq(seqStorePtr, 0, anchor, 0, rLength-MINMATCH);
                ip += rLength;
                anchor = ip;
                continue;   /* faster when present ... (?) */
    }   }   }

    /* save reps for next block */
    seqStorePtr->repToConfirm[0] = offset_1 ? offset_1 : offsetSaved;
    seqStorePtr->repToConfirm[1] = offset_2 ? offset_2 : offsetSaved;

    /* Return the last literals size */
    return iend - anchor;
}


size_t ZSTD_compressBlock_doubleFast(ZSTD_CCtx* ctx, const void* src, size_t srcSize)
{
    const U32 mls = ctx->appliedParams.cParams.searchLength;
    switch(mls)
    {
    default: /* includes case 3 */
    case 4 :
        return ZSTD_compressBlock_doubleFast_generic(ctx, src, srcSize, 4);
    case 5 :
        return ZSTD_compressBlock_doubleFast_generic(ctx, src, srcSize, 5);
    case 6 :
        return ZSTD_compressBlock_doubleFast_generic(ctx, src, srcSize, 6);
    case 7 :
        return ZSTD_compressBlock_doubleFast_generic(ctx, src, srcSize, 7);
    }
}


static size_t ZSTD_compressBlock_doubleFast_extDict_generic(ZSTD_CCtx* ctx,
                                 const void* src, size_t srcSize,
                                 const U32 mls)
{
    U32* const hashLong = ctx->hashTable;
    U32  const hBitsL = ctx->appliedParams.cParams.hashLog;
    U32* const hashSmall = ctx->chainTable;
    U32  const hBitsS = ctx->appliedParams.cParams.chainLog;
    seqStore_t* seqStorePtr = &(ctx->seqStore);
    const BYTE* const base = ctx->base;
    const BYTE* const dictBase = ctx->dictBase;
    const BYTE* const istart = (const BYTE*)src;
    const BYTE* ip = istart;
    const BYTE* anchor = istart;
    const U32   lowestIndex = ctx->lowLimit;
    const BYTE* const dictStart = dictBase + lowestIndex;
    const U32   dictLimit = ctx->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=seqStorePtr->rep[0], offset_2=seqStorePtr->rep[1];

    /* Search Loop */
    while (ip < ilimit) {  /* < instead of <=, because (ip+1) */
        const size_t hSmall = ZSTD_hashPtr(ip, hBitsS, mls);
        const U32 matchIndex = hashSmall[hSmall];
        const BYTE* matchBase = matchIndex < dictLimit ? dictBase : base;
        const BYTE* match = matchBase + matchIndex;

        const size_t hLong = ZSTD_hashPtr(ip, hBitsL, 8);
        const U32 matchLongIndex = hashLong[hLong];
        const BYTE* matchLongBase = matchLongIndex < dictLimit ? dictBase : base;
        const BYTE* matchLong = matchLongBase + matchLongIndex;

        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;
        hashSmall[hSmall] = hashLong[hLong] = 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(seqStorePtr, ip-anchor, anchor, 0, mLength-MINMATCH);
        } else {
            if ((matchLongIndex > lowestIndex) && (MEM_read64(matchLong) == MEM_read64(ip))) {
                const BYTE* matchEnd = matchLongIndex < dictLimit ? dictEnd : iend;
                const BYTE* lowMatchPtr = matchLongIndex < dictLimit ? dictStart : lowPrefixPtr;
                U32 offset;
                mLength = ZSTD_count_2segments(ip+8, matchLong+8, iend, matchEnd, lowPrefixPtr) + 8;
                offset = current - matchLongIndex;
                while (((ip>anchor) & (matchLong>lowMatchPtr)) && (ip[-1] == matchLong[-1])) { ip--; matchLong--; mLength++; }   /* catch up */
                offset_2 = offset_1;
                offset_1 = offset;
                ZSTD_storeSeq(seqStorePtr, ip-anchor, anchor, offset + ZSTD_REP_MOVE, mLength-MINMATCH);

            } else if ((matchIndex > lowestIndex) && (MEM_read32(match) == MEM_read32(ip))) {
                size_t const h3 = ZSTD_hashPtr(ip+1, hBitsL, 8);
                U32 const matchIndex3 = hashLong[h3];
                const BYTE* const match3Base = matchIndex3 < dictLimit ? dictBase : base;
                const BYTE* match3 = match3Base + matchIndex3;
                U32 offset;
                hashLong[h3] = current + 1;
                if ( (matchIndex3 > lowestIndex) && (MEM_read64(match3) == MEM_read64(ip+1)) ) {
                    const BYTE* matchEnd = matchIndex3 < dictLimit ? dictEnd : iend;
                    const BYTE* lowMatchPtr = matchIndex3 < dictLimit ? dictStart : lowPrefixPtr;
                    mLength = ZSTD_count_2segments(ip+9, match3+8, iend, matchEnd, lowPrefixPtr) + 8;
                    ip++;
                    offset = current+1 - matchIndex3;
                    while (((ip>anchor) & (match3>lowMatchPtr)) && (ip[-1] == match3[-1])) { ip--; match3--; mLength++; } /* catch up */
                } else {
                    const BYTE* matchEnd = matchIndex < dictLimit ? dictEnd : iend;
                    const BYTE* lowMatchPtr = matchIndex < dictLimit ? dictStart : lowPrefixPtr;
                    mLength = ZSTD_count_2segments(ip+4, match+4, iend, matchEnd, lowPrefixPtr) + 4;
                    offset = current - matchIndex;
                    while (((ip>anchor) & (match>lowMatchPtr)) && (ip[-1] == match[-1])) { ip--; match--; mLength++; }   /* catch up */
                }
                offset_2 = offset_1;
                offset_1 = offset;
                ZSTD_storeSeq(seqStorePtr, ip-anchor, anchor, offset + ZSTD_REP_MOVE, mLength-MINMATCH);

            } else {
                ip += ((ip-anchor) >> g_searchStrength) + 1;
                continue;
        }   }

        /* found a match : store it */
        ip += mLength;
        anchor = ip;

        if (ip <= ilimit) {
            /* Fill Table */
            hashSmall[ZSTD_hashPtr(base+current+2, hBitsS, mls)] = current+2;
            hashLong[ZSTD_hashPtr(base+current+2, hBitsL, 8)] = current+2;
            hashSmall[ZSTD_hashPtr(ip-2, hBitsS, mls)] = (U32)(ip-2-base);
            hashLong[ZSTD_hashPtr(ip-2, hBitsL, 8)] = (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(seqStorePtr, 0, anchor, 0, repLength2-MINMATCH);
                    hashSmall[ZSTD_hashPtr(ip, hBitsS, mls)] = current2;
                    hashLong[ZSTD_hashPtr(ip, hBitsL, 8)] = current2;
                    ip += repLength2;
                    anchor = ip;
                    continue;
                }
                break;
    }   }   }

    /* save reps for next block */
    seqStorePtr->repToConfirm[0] = offset_1; seqStorePtr->repToConfirm[1] = offset_2;

    /* Return the last literals size */
    return iend - anchor;
}


size_t ZSTD_compressBlock_doubleFast_extDict(ZSTD_CCtx* ctx,
                         const void* src, size_t srcSize)
{
    U32 const mls = ctx->appliedParams.cParams.searchLength;
    switch(mls)
    {
    default: /* includes case 3 */
    case 4 :
        return ZSTD_compressBlock_doubleFast_extDict_generic(ctx, src, srcSize, 4);
    case 5 :
        return ZSTD_compressBlock_doubleFast_extDict_generic(ctx, src, srcSize, 5);
    case 6 :
        return ZSTD_compressBlock_doubleFast_extDict_generic(ctx, src, srcSize, 6);
    case 7 :
        return ZSTD_compressBlock_doubleFast_extDict_generic(ctx, src, srcSize, 7);
    }
}