FreeBSD/Linux Kernel Cross Reference
sys/contrib/zstd/lib/compress/zstd_fast.c

     /*
      * Copyright (c) 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"  /* ZSTD_hashPtr, ZSTD_count, ZSTD_storeSeq */
    #include "zstd_fast.h"
    
    
    void ZSTD_fillHashTable(ZSTD_matchState_t* ms,
                            const void* const end,
                            ZSTD_dictTableLoadMethod_e dtlm)
    {
        const ZSTD_compressionParameters* const cParams = &ms->cParams;
        U32* const hashTable = ms->hashTable;
        U32  const hBits = cParams->hashLog;
        U32  const mls = cParams->minMatch;
        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 < iend + 2; ip += fastHashFillStep) {
            U32 const curr = (U32)(ip - base);
            size_t const hash0 = ZSTD_hashPtr(ip, hBits, mls);
            hashTable[hash0] = curr;
            if (dtlm == ZSTD_dtlm_fast) continue;
            /* Only load extra positions for ZSTD_dtlm_full */
            {   U32 p;
                for (p = 1; p < fastHashFillStep; ++p) {
                    size_t const hash = ZSTD_hashPtr(ip + p, hBits, mls);
                    if (hashTable[hash] == 0) {  /* not yet filled */
                        hashTable[hash] = curr + p;
        }   }   }   }
    }
    
    
    /**
     * If you squint hard enough (and ignore repcodes), the search operation at any
     * given position is broken into 4 stages:
     *
     * 1. Hash   (map position to hash value via input read)
     * 2. Lookup (map hash val to index via hashtable read)
     * 3. Load   (map index to value at that position via input read)
     * 4. Compare
     *
     * Each of these steps involves a memory read at an address which is computed
     * from the previous step. This means these steps must be sequenced and their
     * latencies are cumulative.
     *
     * Rather than do 1->2->3->4 sequentially for a single position before moving
     * onto the next, this implementation interleaves these operations across the
     * next few positions:
     *
     * R = Repcode Read & Compare
     * H = Hash
     * T = Table Lookup
     * M = Match Read & Compare
     *
     * Pos | Time -->
     * ----+-------------------
     * N   | ... M
     * N+1 | ...   TM
     * N+2 |    R H   T M
     * N+3 |         H    TM
     * N+4 |           R H   T M
     * N+5 |                H   ...
     * N+6 |                  R ...
     *
     * This is very much analogous to the pipelining of execution in a CPU. And just
     * like a CPU, we have to dump the pipeline when we find a match (i.e., take a
     * branch).
     *
     * When this happens, we throw away our current state, and do the following prep
     * to re-enter the loop:
     *
     * Pos | Time -->
     * ----+-------------------
     * N   | H T
     * N+1 |  H
     *
     * This is also the work we do at the beginning to enter the loop initially.
     */
    FORCE_INLINE_TEMPLATE size_t
    ZSTD_compressBlock_fast_noDict_generic(
            ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
            void const* src, size_t srcSize,
            U32 const mls, U32 const hasStep)
    {
        const ZSTD_compressionParameters* const cParams = &ms->cParams;
        U32* const hashTable = ms->hashTable;
       U32 const hlog = cParams->hashLog;
       /* support stepSize of 0 */
       size_t const stepSize = hasStep ? (cParams->targetLength + !(cParams->targetLength) + 1) : 2;
       const BYTE* const base = ms->window.base;
       const BYTE* const istart = (const BYTE*)src;
       const U32   endIndex = (U32)((size_t)(istart - base) + srcSize);
       const U32   prefixStartIndex = ZSTD_getLowestPrefixIndex(ms, endIndex, cParams->windowLog);
       const BYTE* const prefixStart = base + prefixStartIndex;
       const BYTE* const iend = istart + srcSize;
       const BYTE* const ilimit = iend - HASH_READ_SIZE;
   
       const BYTE* anchor = istart;
       const BYTE* ip0 = istart;
       const BYTE* ip1;
       const BYTE* ip2;
       const BYTE* ip3;
       U32 current0;
   
       U32 rep_offset1 = rep[0];
       U32 rep_offset2 = rep[1];
       U32 offsetSaved = 0;
   
       size_t hash0; /* hash for ip0 */
       size_t hash1; /* hash for ip1 */
       U32 idx; /* match idx for ip0 */
       U32 mval; /* src value at match idx */
   
       U32 offcode;
       const BYTE* match0;
       size_t mLength;
   
       /* ip0 and ip1 are always adjacent. The targetLength skipping and
        * uncompressibility acceleration is applied to every other position,
        * matching the behavior of #1562. step therefore represents the gap
        * between pairs of positions, from ip0 to ip2 or ip1 to ip3. */
       size_t step;
       const BYTE* nextStep;
       const size_t kStepIncr = (1 << (kSearchStrength - 1));
   
       DEBUGLOG(5, "ZSTD_compressBlock_fast_generic");
       ip0 += (ip0 == prefixStart);
       {   U32 const curr = (U32)(ip0 - base);
           U32 const windowLow = ZSTD_getLowestPrefixIndex(ms, curr, cParams->windowLog);
           U32 const maxRep = curr - windowLow;
           if (rep_offset2 > maxRep) offsetSaved = rep_offset2, rep_offset2 = 0;
           if (rep_offset1 > maxRep) offsetSaved = rep_offset1, rep_offset1 = 0;
       }
   
       /* start each op */
   _start: /* Requires: ip0 */
   
       step = stepSize;
       nextStep = ip0 + kStepIncr;
   
       /* calculate positions, ip0 - anchor == 0, so we skip step calc */
       ip1 = ip0 + 1;
       ip2 = ip0 + step;
       ip3 = ip2 + 1;
   
       if (ip3 >= ilimit) {
           goto _cleanup;
       }
   
       hash0 = ZSTD_hashPtr(ip0, hlog, mls);
       hash1 = ZSTD_hashPtr(ip1, hlog, mls);
   
       idx = hashTable[hash0];
   
       do {
           /* load repcode match for ip[2]*/
           const U32 rval = MEM_read32(ip2 - rep_offset1);
   
           /* write back hash table entry */
           current0 = (U32)(ip0 - base);
           hashTable[hash0] = current0;
   
           /* check repcode at ip[2] */
           if ((MEM_read32(ip2) == rval) & (rep_offset1 > 0)) {
               ip0 = ip2;
               match0 = ip0 - rep_offset1;
               mLength = ip0[-1] == match0[-1];
               ip0 -= mLength;
               match0 -= mLength;
               offcode = STORE_REPCODE_1;
               mLength += 4;
               goto _match;
           }
   
           /* load match for ip[0] */
           if (idx >= prefixStartIndex) {
               mval = MEM_read32(base + idx);
           } else {
               mval = MEM_read32(ip0) ^ 1; /* guaranteed to not match. */
           }
   
           /* check match at ip[0] */
           if (MEM_read32(ip0) == mval) {
               /* found a match! */
               goto _offset;
           }
   
           /* lookup ip[1] */
           idx = hashTable[hash1];
   
           /* hash ip[2] */
           hash0 = hash1;
           hash1 = ZSTD_hashPtr(ip2, hlog, mls);
   
           /* advance to next positions */
           ip0 = ip1;
           ip1 = ip2;
           ip2 = ip3;
   
           /* write back hash table entry */
           current0 = (U32)(ip0 - base);
           hashTable[hash0] = current0;
   
           /* load match for ip[0] */
           if (idx >= prefixStartIndex) {
               mval = MEM_read32(base + idx);
           } else {
               mval = MEM_read32(ip0) ^ 1; /* guaranteed to not match. */
           }
   
           /* check match at ip[0] */
           if (MEM_read32(ip0) == mval) {
               /* found a match! */
               goto _offset;
           }
   
           /* lookup ip[1] */
           idx = hashTable[hash1];
   
           /* hash ip[2] */
           hash0 = hash1;
           hash1 = ZSTD_hashPtr(ip2, hlog, mls);
   
           /* advance to next positions */
           ip0 = ip1;
           ip1 = ip2;
           ip2 = ip0 + step;
           ip3 = ip1 + step;
   
           /* calculate step */
           if (ip2 >= nextStep) {
               step++;
               PREFETCH_L1(ip1 + 64);
               PREFETCH_L1(ip1 + 128);
               nextStep += kStepIncr;
           }
       } while (ip3 < ilimit);
   
   _cleanup:
       /* Note that there are probably still a couple positions we could search.
        * However, it seems to be a meaningful performance hit to try to search
        * them. So let's not. */
   
       /* save reps for next block */
       rep[0] = rep_offset1 ? rep_offset1 : offsetSaved;
       rep[1] = rep_offset2 ? rep_offset2 : offsetSaved;
   
       /* Return the last literals size */
       return (size_t)(iend - anchor);
   
   _offset: /* Requires: ip0, idx */
   
       /* Compute the offset code. */
       match0 = base + idx;
       rep_offset2 = rep_offset1;
       rep_offset1 = (U32)(ip0-match0);
       offcode = STORE_OFFSET(rep_offset1);
       mLength = 4;
   
       /* Count the backwards match length. */
       while (((ip0>anchor) & (match0>prefixStart)) && (ip0[-1] == match0[-1])) {
           ip0--;
           match0--;
           mLength++;
       }
   
   _match: /* Requires: ip0, match0, offcode */
   
       /* Count the forward length. */
       mLength += ZSTD_count(ip0 + mLength, match0 + mLength, iend);
   
       ZSTD_storeSeq(seqStore, (size_t)(ip0 - anchor), anchor, iend, offcode, mLength);
   
       ip0 += mLength;
       anchor = ip0;
   
       /* write next hash table entry */
       if (ip1 < ip0) {
           hashTable[hash1] = (U32)(ip1 - base);
       }
   
       /* Fill table and check for immediate repcode. */
       if (ip0 <= ilimit) {
           /* Fill Table */
           assert(base+current0+2 > istart);  /* check base overflow */
           hashTable[ZSTD_hashPtr(base+current0+2, hlog, mls)] = current0+2;  /* here because current+2 could be > iend-8 */
           hashTable[ZSTD_hashPtr(ip0-2, hlog, mls)] = (U32)(ip0-2-base);
   
           if (rep_offset2 > 0) { /* rep_offset2==0 means rep_offset2 is invalidated */
               while ( (ip0 <= ilimit) && (MEM_read32(ip0) == MEM_read32(ip0 - rep_offset2)) ) {
                   /* store sequence */
                   size_t const rLength = ZSTD_count(ip0+4, ip0+4-rep_offset2, iend) + 4;
                   { U32 const tmpOff = rep_offset2; rep_offset2 = rep_offset1; rep_offset1 = tmpOff; } /* swap rep_offset2 <=> rep_offset1 */
                   hashTable[ZSTD_hashPtr(ip0, hlog, mls)] = (U32)(ip0-base);
                   ip0 += rLength;
                   ZSTD_storeSeq(seqStore, 0 /*litLen*/, anchor, iend, STORE_REPCODE_1, rLength);
                   anchor = ip0;
                   continue;   /* faster when present (confirmed on gcc-8) ... (?) */
       }   }   }
   
       goto _start;
   }
   
   #define ZSTD_GEN_FAST_FN(dictMode, mls, step)                                                            \
       static size_t ZSTD_compressBlock_fast_##dictMode##_##mls##_##step(                                      \
               ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],                    \
               void const* src, size_t srcSize)                                                       \
       {                                                                                              \
           return ZSTD_compressBlock_fast_##dictMode##_generic(ms, seqStore, rep, src, srcSize, mls, step); \
       }
   
   ZSTD_GEN_FAST_FN(noDict, 4, 1)
   ZSTD_GEN_FAST_FN(noDict, 5, 1)
   ZSTD_GEN_FAST_FN(noDict, 6, 1)
   ZSTD_GEN_FAST_FN(noDict, 7, 1)
   
   ZSTD_GEN_FAST_FN(noDict, 4, 0)
   ZSTD_GEN_FAST_FN(noDict, 5, 0)
   ZSTD_GEN_FAST_FN(noDict, 6, 0)
   ZSTD_GEN_FAST_FN(noDict, 7, 0)
   
   size_t ZSTD_compressBlock_fast(
           ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
           void const* src, size_t srcSize)
   {
       U32 const mls = ms->cParams.minMatch;
       assert(ms->dictMatchState == NULL);
       if (ms->cParams.targetLength > 1) {
           switch(mls)
           {
           default: /* includes case 3 */
           case 4 :
               return ZSTD_compressBlock_fast_noDict_4_1(ms, seqStore, rep, src, srcSize);
           case 5 :
               return ZSTD_compressBlock_fast_noDict_5_1(ms, seqStore, rep, src, srcSize);
           case 6 :
               return ZSTD_compressBlock_fast_noDict_6_1(ms, seqStore, rep, src, srcSize);
           case 7 :
               return ZSTD_compressBlock_fast_noDict_7_1(ms, seqStore, rep, src, srcSize);
           }
       } else {
           switch(mls)
           {
           default: /* includes case 3 */
           case 4 :
               return ZSTD_compressBlock_fast_noDict_4_0(ms, seqStore, rep, src, srcSize);
           case 5 :
               return ZSTD_compressBlock_fast_noDict_5_0(ms, seqStore, rep, src, srcSize);
           case 6 :
               return ZSTD_compressBlock_fast_noDict_6_0(ms, seqStore, rep, src, srcSize);
           case 7 :
               return ZSTD_compressBlock_fast_noDict_7_0(ms, seqStore, rep, src, srcSize);
           }
   
       }
   }
   
   FORCE_INLINE_TEMPLATE
   size_t ZSTD_compressBlock_fast_dictMatchState_generic(
           ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
           void const* src, size_t srcSize, U32 const mls, U32 const hasStep)
   {
       const ZSTD_compressionParameters* const cParams = &ms->cParams;
       U32* const hashTable = ms->hashTable;
       U32 const hlog = cParams->hashLog;
       /* support stepSize of 0 */
       U32 const stepSize = cParams->targetLength + !(cParams->targetLength);
       const BYTE* const base = ms->window.base;
       const BYTE* const istart = (const BYTE*)src;
       const BYTE* ip = istart;
       const BYTE* anchor = istart;
       const U32   prefixStartIndex = ms->window.dictLimit;
       const BYTE* const prefixStart = base + prefixStartIndex;
       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;
   
       const ZSTD_matchState_t* const dms = ms->dictMatchState;
       const ZSTD_compressionParameters* const dictCParams = &dms->cParams ;
       const U32* const dictHashTable = dms->hashTable;
       const U32 dictStartIndex       = dms->window.dictLimit;
       const BYTE* const dictBase     = dms->window.base;
       const BYTE* const dictStart    = dictBase + dictStartIndex;
       const BYTE* const dictEnd      = dms->window.nextSrc;
       const U32 dictIndexDelta       = prefixStartIndex - (U32)(dictEnd - dictBase);
       const U32 dictAndPrefixLength  = (U32)(ip - prefixStart + dictEnd - dictStart);
       const U32 dictHLog             = dictCParams->hashLog;
   
       /* if a dictionary is still attached, it necessarily means that
        * it is within window size. So we just check it. */
       const U32 maxDistance = 1U << cParams->windowLog;
       const U32 endIndex = (U32)((size_t)(ip - base) + srcSize);
       assert(endIndex - prefixStartIndex <= maxDistance);
       (void)maxDistance; (void)endIndex;   /* these variables are not used when assert() is disabled */
   
       (void)hasStep; /* not currently specialized on whether it's accelerated */
   
       /* ensure there will be no underflow
        * when translating a dict index into a local index */
       assert(prefixStartIndex >= (U32)(dictEnd - dictBase));
   
       /* init */
       DEBUGLOG(5, "ZSTD_compressBlock_fast_dictMatchState_generic");
       ip += (dictAndPrefixLength == 0);
       /* dictMatchState repCode checks don't currently handle repCode == 0
        * disabling. */
       assert(offset_1 <= dictAndPrefixLength);
       assert(offset_2 <= dictAndPrefixLength);
   
       /* 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 curr = (U32)(ip-base);
           U32 const matchIndex = hashTable[h];
           const BYTE* match = base + matchIndex;
           const U32 repIndex = curr + 1 - offset_1;
           const BYTE* repMatch = (repIndex < prefixStartIndex) ?
                                  dictBase + (repIndex - dictIndexDelta) :
                                  base + repIndex;
           hashTable[h] = curr;   /* update hash table */
   
           if ( ((U32)((prefixStartIndex-1) - repIndex) >= 3) /* intentional underflow : ensure repIndex isn't overlapping dict + prefix */
             && (MEM_read32(repMatch) == MEM_read32(ip+1)) ) {
               const BYTE* const repMatchEnd = repIndex < prefixStartIndex ? dictEnd : iend;
               mLength = ZSTD_count_2segments(ip+1+4, repMatch+4, iend, repMatchEnd, prefixStart) + 4;
               ip++;
               ZSTD_storeSeq(seqStore, (size_t)(ip-anchor), anchor, iend, STORE_REPCODE_1, mLength);
           } else if ( (matchIndex <= prefixStartIndex) ) {
               size_t const dictHash = ZSTD_hashPtr(ip, dictHLog, mls);
               U32 const dictMatchIndex = dictHashTable[dictHash];
               const BYTE* dictMatch = dictBase + dictMatchIndex;
               if (dictMatchIndex <= dictStartIndex ||
                   MEM_read32(dictMatch) != MEM_read32(ip)) {
                   assert(stepSize >= 1);
                   ip += ((ip-anchor) >> kSearchStrength) + stepSize;
                   continue;
               } else {
                   /* found a dict match */
                   U32 const offset = (U32)(curr-dictMatchIndex-dictIndexDelta);
                   mLength = ZSTD_count_2segments(ip+4, dictMatch+4, iend, dictEnd, prefixStart) + 4;
                   while (((ip>anchor) & (dictMatch>dictStart))
                        && (ip[-1] == dictMatch[-1])) {
                       ip--; dictMatch--; mLength++;
                   } /* catch up */
                   offset_2 = offset_1;
                   offset_1 = offset;
                   ZSTD_storeSeq(seqStore, (size_t)(ip-anchor), anchor, iend, STORE_OFFSET(offset), mLength);
               }
           } else if (MEM_read32(match) != MEM_read32(ip)) {
               /* it's not a match, and we're not going to check the dictionary */
               assert(stepSize >= 1);
               ip += ((ip-anchor) >> kSearchStrength) + stepSize;
               continue;
           } else {
               /* found a regular match */
               U32 const offset = (U32)(ip-match);
               mLength = ZSTD_count(ip+4, match+4, iend) + 4;
               while (((ip>anchor) & (match>prefixStart))
                    && (ip[-1] == match[-1])) { ip--; match--; mLength++; } /* catch up */
               offset_2 = offset_1;
               offset_1 = offset;
               ZSTD_storeSeq(seqStore, (size_t)(ip-anchor), anchor, iend, STORE_OFFSET(offset), mLength);
           }
   
           /* match found */
           ip += mLength;
           anchor = ip;
   
           if (ip <= ilimit) {
               /* Fill Table */
               assert(base+curr+2 > istart);  /* check base overflow */
               hashTable[ZSTD_hashPtr(base+curr+2, hlog, mls)] = curr+2;  /* here because curr+2 could be > iend-8 */
               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 < prefixStartIndex ?
                           dictBase - dictIndexDelta + repIndex2 :
                           base + repIndex2;
                   if ( ((U32)((prefixStartIndex-1) - (U32)repIndex2) >= 3 /* intentional overflow */)
                      && (MEM_read32(repMatch2) == MEM_read32(ip)) ) {
                       const BYTE* const repEnd2 = repIndex2 < prefixStartIndex ? dictEnd : iend;
                       size_t const repLength2 = ZSTD_count_2segments(ip+4, repMatch2+4, iend, repEnd2, prefixStart) + 4;
                       U32 tmpOffset = offset_2; offset_2 = offset_1; offset_1 = tmpOffset;   /* swap offset_2 <=> offset_1 */
                       ZSTD_storeSeq(seqStore, 0, anchor, iend, STORE_REPCODE_1, repLength2);
                       hashTable[ZSTD_hashPtr(ip, hlog, mls)] = current2;
                       ip += repLength2;
                       anchor = ip;
                       continue;
                   }
                   break;
               }
           }
       }
   
       /* 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 (size_t)(iend - anchor);
   }
   
   
   ZSTD_GEN_FAST_FN(dictMatchState, 4, 0)
   ZSTD_GEN_FAST_FN(dictMatchState, 5, 0)
   ZSTD_GEN_FAST_FN(dictMatchState, 6, 0)
   ZSTD_GEN_FAST_FN(dictMatchState, 7, 0)
   
   size_t ZSTD_compressBlock_fast_dictMatchState(
           ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
           void const* src, size_t srcSize)
   {
       U32 const mls = ms->cParams.minMatch;
       assert(ms->dictMatchState != NULL);
       switch(mls)
       {
       default: /* includes case 3 */
       case 4 :
           return ZSTD_compressBlock_fast_dictMatchState_4_0(ms, seqStore, rep, src, srcSize);
       case 5 :
           return ZSTD_compressBlock_fast_dictMatchState_5_0(ms, seqStore, rep, src, srcSize);
       case 6 :
           return ZSTD_compressBlock_fast_dictMatchState_6_0(ms, seqStore, rep, src, srcSize);
       case 7 :
           return ZSTD_compressBlock_fast_dictMatchState_7_0(ms, seqStore, rep, src, srcSize);
       }
   }
   
   
   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 mls, U32 const hasStep)
   {
       const ZSTD_compressionParameters* const cParams = &ms->cParams;
       U32* const hashTable = ms->hashTable;
       U32 const hlog = cParams->hashLog;
       /* support stepSize of 0 */
       U32 const stepSize = cParams->targetLength + !(cParams->targetLength);
       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   endIndex = (U32)((size_t)(istart - base) + srcSize);
       const U32   lowLimit = ZSTD_getLowestMatchIndex(ms, endIndex, cParams->windowLog);
       const U32   dictStartIndex = lowLimit;
       const BYTE* const dictStart = dictBase + dictStartIndex;
       const U32   dictLimit = ms->window.dictLimit;
       const U32   prefixStartIndex = dictLimit < lowLimit ? lowLimit : dictLimit;
       const BYTE* const prefixStart = base + prefixStartIndex;
       const BYTE* const dictEnd = dictBase + prefixStartIndex;
       const BYTE* const iend = istart + srcSize;
       const BYTE* const ilimit = iend - 8;
       U32 offset_1=rep[0], offset_2=rep[1];
   
       (void)hasStep; /* not currently specialized on whether it's accelerated */
   
       DEBUGLOG(5, "ZSTD_compressBlock_fast_extDict_generic (offset_1=%u)", offset_1);
   
       /* switch to "regular" variant if extDict is invalidated due to maxDistance */
       if (prefixStartIndex == dictStartIndex)
           return ZSTD_compressBlock_fast(ms, seqStore, rep, src, srcSize);
   
       /* 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* const matchBase = matchIndex < prefixStartIndex ? dictBase : base;
           const BYTE*  match = matchBase + matchIndex;
           const U32    curr = (U32)(ip-base);
           const U32    repIndex = curr + 1 - offset_1;
           const BYTE* const repBase = repIndex < prefixStartIndex ? dictBase : base;
           const BYTE* const repMatch = repBase + repIndex;
           hashTable[h] = curr;   /* update hash table */
           DEBUGLOG(7, "offset_1 = %u , curr = %u", offset_1, curr);
   
           if ( ( ((U32)((prefixStartIndex-1) - repIndex) >= 3) /* intentional underflow */
                & (offset_1 <= curr+1 - dictStartIndex) ) /* note: we are searching at curr+1 */
              && (MEM_read32(repMatch) == MEM_read32(ip+1)) ) {
               const BYTE* const repMatchEnd = repIndex < prefixStartIndex ? dictEnd : iend;
               size_t const rLength = ZSTD_count_2segments(ip+1 +4, repMatch +4, iend, repMatchEnd, prefixStart) + 4;
               ip++;
               ZSTD_storeSeq(seqStore, (size_t)(ip-anchor), anchor, iend, STORE_REPCODE_1, rLength);
               ip += rLength;
               anchor = ip;
           } else {
               if ( (matchIndex < dictStartIndex) ||
                    (MEM_read32(match) != MEM_read32(ip)) ) {
                   assert(stepSize >= 1);
                   ip += ((ip-anchor) >> kSearchStrength) + stepSize;
                   continue;
               }
               {   const BYTE* const matchEnd = matchIndex < prefixStartIndex ? dictEnd : iend;
                   const BYTE* const lowMatchPtr = matchIndex < prefixStartIndex ? dictStart : prefixStart;
                   U32 const offset = curr - matchIndex;
                   size_t mLength = ZSTD_count_2segments(ip+4, match+4, iend, matchEnd, prefixStart) + 4;
                   while (((ip>anchor) & (match>lowMatchPtr)) && (ip[-1] == match[-1])) { ip--; match--; mLength++; }   /* catch up */
                   offset_2 = offset_1; offset_1 = offset;  /* update offset history */
                   ZSTD_storeSeq(seqStore, (size_t)(ip-anchor), anchor, iend, STORE_OFFSET(offset), mLength);
                   ip += mLength;
                   anchor = ip;
           }   }
   
           if (ip <= ilimit) {
               /* Fill Table */
               hashTable[ZSTD_hashPtr(base+curr+2, hlog, mls)] = curr+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* const repMatch2 = repIndex2 < prefixStartIndex ? dictBase + repIndex2 : base + repIndex2;
                   if ( (((U32)((prefixStartIndex-1) - repIndex2) >= 3) & (offset_2 <= curr - dictStartIndex))  /* intentional overflow */
                      && (MEM_read32(repMatch2) == MEM_read32(ip)) ) {
                       const BYTE* const repEnd2 = repIndex2 < prefixStartIndex ? dictEnd : iend;
                       size_t const repLength2 = ZSTD_count_2segments(ip+4, repMatch2+4, iend, repEnd2, prefixStart) + 4;
                       { U32 const tmpOffset = offset_2; offset_2 = offset_1; offset_1 = tmpOffset; }  /* swap offset_2 <=> offset_1 */
                       ZSTD_storeSeq(seqStore, 0 /*litlen*/, anchor, iend, STORE_REPCODE_1, repLength2);
                       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 (size_t)(iend - anchor);
   }
   
   ZSTD_GEN_FAST_FN(extDict, 4, 0)
   ZSTD_GEN_FAST_FN(extDict, 5, 0)
   ZSTD_GEN_FAST_FN(extDict, 6, 0)
   ZSTD_GEN_FAST_FN(extDict, 7, 0)
   
   size_t ZSTD_compressBlock_fast_extDict(
           ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
           void const* src, size_t srcSize)
   {
       U32 const mls = ms->cParams.minMatch;
       switch(mls)
       {
       default: /* includes case 3 */
       case 4 :
           return ZSTD_compressBlock_fast_extDict_4_0(ms, seqStore, rep, src, srcSize);
       case 5 :
           return ZSTD_compressBlock_fast_extDict_5_0(ms, seqStore, rep, src, srcSize);
       case 6 :
           return ZSTD_compressBlock_fast_extDict_6_0(ms, seqStore, rep, src, srcSize);
       case 7 :
           return ZSTD_compressBlock_fast_extDict_7_0(ms, seqStore, rep, src, srcSize);
       }
   }

Cache object: c3668c6be4f821d12e6dd333908390e8