summaryrefslogtreecommitdiffstats
path: root/src/zstd/lib/compress/zstd_fast.c
blob: 85a3a7a91e49d2dcb45e7be82887f555e5ab4928 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
/*
 * Copyright (c) 2016-2020, 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 current = (U32)(ip - base);
        size_t const hash0 = ZSTD_hashPtr(ip, hBits, mls);
        hashTable[hash0] = current;
        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] = current + p;
    }   }   }   }
}


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 mls)
{
    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 = cParams->targetLength + !(cParams->targetLength) + 1;
    const BYTE* const base = ms->window.base;
    const BYTE* const istart = (const BYTE*)src;
    /* We check ip0 (ip + 0) and ip1 (ip + 1) each loop */
    const BYTE* ip0 = istart;
    const BYTE* ip1;
    const BYTE* anchor = istart;
    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;
    U32 offset_1=rep[0], offset_2=rep[1];
    U32 offsetSaved = 0;

    /* init */
    DEBUGLOG(5, "ZSTD_compressBlock_fast_generic");
    ip0 += (ip0 == prefixStart);
    ip1 = ip0 + 1;
    {   U32 const current = (U32)(ip0 - base);
        U32 const windowLow = ZSTD_getLowestPrefixIndex(ms, current, cParams->windowLog);
        U32 const maxRep = current - windowLow;
        if (offset_2 > maxRep) offsetSaved = offset_2, offset_2 = 0;
        if (offset_1 > maxRep) offsetSaved = offset_1, offset_1 = 0;
    }

    /* Main Search Loop */
#ifdef __INTEL_COMPILER
    /* From intel 'The vector pragma indicates that the loop should be
     * vectorized if it is legal to do so'. Can be used together with
     * #pragma ivdep (but have opted to exclude that because intel
     * warns against using it).*/
    #pragma vector always
#endif
    while (ip1 < ilimit) {   /* < instead of <=, because check at ip0+2 */
        size_t mLength;
        BYTE const* ip2 = ip0 + 2;
        size_t const h0 = ZSTD_hashPtr(ip0, hlog, mls);
        U32 const val0 = MEM_read32(ip0);
        size_t const h1 = ZSTD_hashPtr(ip1, hlog, mls);
        U32 const val1 = MEM_read32(ip1);
        U32 const current0 = (U32)(ip0-base);
        U32 const current1 = (U32)(ip1-base);
        U32 const matchIndex0 = hashTable[h0];
        U32 const matchIndex1 = hashTable[h1];
        BYTE const* repMatch = ip2 - offset_1;
        const BYTE* match0 = base + matchIndex0;
        const BYTE* match1 = base + matchIndex1;
        U32 offcode;

#if defined(__aarch64__)
        PREFETCH_L1(ip0+256);
#endif

        hashTable[h0] = current0;   /* update hash table */
        hashTable[h1] = current1;   /* update hash table */

        assert(ip0 + 1 == ip1);

        if ((offset_1 > 0) & (MEM_read32(repMatch) == MEM_read32(ip2))) {
            mLength = (ip2[-1] == repMatch[-1]) ? 1 : 0;
            ip0 = ip2 - mLength;
            match0 = repMatch - mLength;
            mLength += 4;
            offcode = 0;
            goto _match;
        }
        if ((matchIndex0 > prefixStartIndex) && MEM_read32(match0) == val0) {
            /* found a regular match */
            goto _offset;
        }
        if ((matchIndex1 > prefixStartIndex) && MEM_read32(match1) == val1) {
            /* found a regular match after one literal */
            ip0 = ip1;
            match0 = match1;
            goto _offset;
        }
        {   size_t const step = ((size_t)(ip0-anchor) >> (kSearchStrength - 1)) + stepSize;
            assert(step >= 2);
            ip0 += step;
            ip1 += step;
            continue;
        }
_offset: /* Requires: ip0, match0 */
        /* Compute the offset code */
        offset_2 = offset_1;
        offset_1 = (U32)(ip0-match0);
        offcode = offset_1 + ZSTD_REP_MOVE;
        mLength = 4;
        /* Count the backwards match length */
        while (((ip0>anchor) & (match0>prefixStart))
             && (ip0[-1] == match0[-1])) { ip0--; match0--; mLength++; } /* catch up */

_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-MINMATCH);
        /* match found */
        ip0 += mLength;
        anchor = ip0;

        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 (offset_2 > 0) { /* offset_2==0 means offset_2 is invalidated */
                while ( (ip0 <= ilimit) && (MEM_read32(ip0) == MEM_read32(ip0 - offset_2)) ) {
                    /* store sequence */
                    size_t const rLength = ZSTD_count(ip0+4, ip0+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(ip0, hlog, mls)] = (U32)(ip0-base);
                    ip0 += rLength;
                    ZSTD_storeSeq(seqStore, 0 /*litLen*/, anchor, iend, 0 /*offCode*/, rLength-MINMATCH);
                    anchor = ip0;
                    continue;   /* faster when present (confirmed on gcc-8) ... (?) */
        }   }   }
        ip1 = ip0 + 1;
    }

    /* 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);
}


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);
    switch(mls)
    {
    default: /* includes case 3 */
    case 4 :
        return ZSTD_compressBlock_fast_generic(ms, seqStore, rep, src, srcSize, 4);
    case 5 :
        return ZSTD_compressBlock_fast_generic(ms, seqStore, rep, src, srcSize, 5);
    case 6 :
        return ZSTD_compressBlock_fast_generic(ms, seqStore, rep, src, srcSize, 6);
    case 7 :
        return ZSTD_compressBlock_fast_generic(ms, seqStore, rep, src, srcSize, 7);
    }
}

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)
{
    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 */

    /* ensure there will be no 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 current = (U32)(ip-base);
        U32 const matchIndex = hashTable[h];
        const BYTE* match = base + matchIndex;
        const U32 repIndex = current + 1 - offset_1;
        const BYTE* repMatch = (repIndex < prefixStartIndex) ?
                               dictBase + (repIndex - dictIndexDelta) :
                               base + repIndex;
        hashTable[h] = current;   /* 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, 0, mLength-MINMATCH);
        } 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)(current-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, offset + ZSTD_REP_MOVE, mLength-MINMATCH);
            }
        } 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, offset + ZSTD_REP_MOVE, mLength-MINMATCH);
        }

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

        if (ip <= ilimit) {
            /* Fill Table */
            assert(base+current+2 > istart);  /* check base overflow */
            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) {
                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, 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 ? offset_1 : offsetSaved;
    rep[1] = offset_2 ? offset_2 : offsetSaved;

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

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_generic(ms, seqStore, rep, src, srcSize, 4);
    case 5 :
        return ZSTD_compressBlock_fast_dictMatchState_generic(ms, seqStore, rep, src, srcSize, 5);
    case 6 :
        return ZSTD_compressBlock_fast_dictMatchState_generic(ms, seqStore, rep, src, srcSize, 6);
    case 7 :
        return ZSTD_compressBlock_fast_dictMatchState_generic(ms, seqStore, rep, src, srcSize, 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 mls)
{
    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];

    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_generic(ms, seqStore, rep, src, srcSize, mls);

    /* 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    current = (U32)(ip-base);
        const U32    repIndex = current + 1 - offset_1;
        const BYTE* const repBase = repIndex < prefixStartIndex ? dictBase : base;
        const BYTE* const repMatch = repBase + repIndex;
        hashTable[h] = current;   /* update hash table */
        DEBUGLOG(7, "offset_1 = %u , current = %u", offset_1, current);
        assert(offset_1 <= current +1);   /* check repIndex */

        if ( (((U32)((prefixStartIndex-1) - repIndex) >= 3) /* intentional underflow */ & (repIndex > dictStartIndex))
           && (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, 0, rLength-MINMATCH);
            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 = current - 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, offset + ZSTD_REP_MOVE, mLength-MINMATCH);
                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* const repMatch2 = repIndex2 < prefixStartIndex ? dictBase + repIndex2 : base + repIndex2;
                if ( (((U32)((prefixStartIndex-1) - repIndex2) >= 3) & (repIndex2 > 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, 0 /*offcode*/, 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 (size_t)(iend - anchor);
}


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_generic(ms, seqStore, rep, src, srcSize, 4);
    case 5 :
        return ZSTD_compressBlock_fast_extDict_generic(ms, seqStore, rep, src, srcSize, 5);
    case 6 :
        return ZSTD_compressBlock_fast_extDict_generic(ms, seqStore, rep, src, srcSize, 6);
    case 7 :
        return ZSTD_compressBlock_fast_extDict_generic(ms, seqStore, rep, src, srcSize, 7);
    }
}