summaryrefslogtreecommitdiffstats
path: root/lib/lz4opt.h
blob: d51d491591e6af1bf1248fd866babfb2f3b84320 (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
/*
    lz4opt.h - Optimal Mode of LZ4
    Copyright (C) 2015-2017, Przemyslaw Skibinski <inikep@gmail.com>
    Note : this file is intended to be included within lz4hc.c

    BSD 2-Clause License (http://www.opensource.org/licenses/bsd-license.php)

    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions are
    met:

    * Redistributions of source code must retain the above copyright
    notice, this list of conditions and the following disclaimer.
    * Redistributions in binary form must reproduce the above
    copyright notice, this list of conditions and the following disclaimer
    in the documentation and/or other materials provided with the
    distribution.

    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
    A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
    OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
    SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
    LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
    DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
    THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
    (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
    OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

    You can contact the author at :
       - LZ4 source repository : https://github.com/lz4/lz4
       - LZ4 public forum : https://groups.google.com/forum/#!forum/lz4c
*/

#define LZ4_OPT_NUM   (1<<12)


typedef struct {
    int off;
    int len;
} LZ4HC_match_t;

typedef struct {
    int price;
    int off;
    int mlen;
    int litlen;
} LZ4HC_optimal_t;


/* price in bits */
FORCE_INLINE size_t LZ4HC_literalsPrice(size_t litlen)
{
    size_t price = litlen;
    if (litlen >= (size_t)RUN_MASK) price += 1 + (litlen-RUN_MASK)/255;
    return price;
}


/* requires mlen >= MINMATCH */
FORCE_INLINE size_t LZ4HC_sequencePrice(size_t litlen, size_t mlen)
{
    size_t price = 2 + 1; /* 16-bit offset + token */

    price += LZ4HC_literalsPrice(litlen);

    if (mlen >= (size_t)(ML_MASK+MINMATCH))
        price+= 1+(mlen-(ML_MASK+MINMATCH))/255;

    return price;
}


/*-*************************************
*  Binary Tree search
***************************************/
FORCE_INLINE int LZ4HC_BinTree_InsertAndGetAllMatches (
    LZ4HC_CCtx_internal* ctx,
    const BYTE* const ip,
    const BYTE* const iHighLimit,
    size_t best_mlen,
    LZ4HC_match_t* matches,
    int* matchNum)
{
    U16* const chainTable = ctx->chainTable;
    U32* const HashTable = ctx->hashTable;
    const BYTE* const base = ctx->base;
    const U32 dictLimit = ctx->dictLimit;
    const U32 current = (U32)(ip - base);
    const U32 lowLimit = (ctx->lowLimit + MAX_DISTANCE > current) ? ctx->lowLimit : current - (MAX_DISTANCE - 1);
    const BYTE* const dictBase = ctx->dictBase;
    const BYTE* match;
    int nbAttempts = ctx->searchNum;
    int mnum = 0;
    U16 *ptr0, *ptr1, delta0, delta1;
    U32 matchIndex;
    size_t matchLength = 0;
    U32* HashPos;

    if (ip + MINMATCH > iHighLimit) return 1;

    /* HC4 match finder */
    HashPos = &HashTable[LZ4HC_hashPtr(ip)];
    matchIndex = *HashPos;
    *HashPos = current;

    ptr0 = &DELTANEXTMAXD(current*2+1);
    ptr1 = &DELTANEXTMAXD(current*2);
    delta0 = delta1 = (U16)(current - matchIndex);

    while ((matchIndex < current) && (matchIndex>=lowLimit) && (nbAttempts)) {
        nbAttempts--;
        if (matchIndex >= dictLimit) {
            match = base + matchIndex;
            matchLength = LZ4_count(ip, match, iHighLimit);
        } else {
            const BYTE* vLimit = ip + (dictLimit - matchIndex);
            match = dictBase + matchIndex;
            if (vLimit > iHighLimit) vLimit = iHighLimit;
            matchLength = LZ4_count(ip, match, vLimit);
            if ((ip+matchLength == vLimit) && (vLimit < iHighLimit))
                matchLength += LZ4_count(ip+matchLength, base+dictLimit, iHighLimit);
        }

        if (matchLength > best_mlen) {
            best_mlen = matchLength;
            if (matches) {
                if (matchIndex >= dictLimit)
                    matches[mnum].off = (int)(ip - match);
                else
                    matches[mnum].off = (int)(ip - (base + matchIndex)); /* virtual matchpos */
                matches[mnum].len = (int)matchLength;
                mnum++;
            }
            if (best_mlen > LZ4_OPT_NUM) break;
        }

        if (ip+matchLength >= iHighLimit)   /* equal : no way to know if inf or sup */
            break;   /* drop , to guarantee consistency ; miss a bit of compression, but other solutions can corrupt the tree */

        if (*(ip+matchLength) < *(match+matchLength)) {
            *ptr0 = delta0;
            ptr0 = &DELTANEXTMAXD(matchIndex*2);
            if (*ptr0 == (U16)-1) break;
            delta0 = *ptr0;
            delta1 += delta0;
            matchIndex -= delta0;
        } else {
            *ptr1 = delta1;
            ptr1 = &DELTANEXTMAXD(matchIndex*2+1);
            if (*ptr1 == (U16)-1) break;
            delta1 = *ptr1;
            delta0 += delta1;
            matchIndex -= delta1;
        }
    }

    *ptr0 = (U16)-1;
    *ptr1 = (U16)-1;
    if (matchNum) *matchNum = mnum;
  /*  if (best_mlen > 8) return best_mlen-8; */
    if (!matchNum) return 1;
    return 1;
}


FORCE_INLINE void LZ4HC_updateBinTree(LZ4HC_CCtx_internal* ctx, const BYTE* const ip, const BYTE* const iHighLimit)
{
    const BYTE* const base = ctx->base;
    const U32 target = (U32)(ip - base);
    U32 idx = ctx->nextToUpdate;
    while(idx < target)
        idx += LZ4HC_BinTree_InsertAndGetAllMatches(ctx, base+idx, iHighLimit, 8, NULL, NULL);
}


/** Tree updater, providing best match */
FORCE_INLINE int LZ4HC_BinTree_GetAllMatches (
                        LZ4HC_CCtx_internal* ctx,
                        const BYTE* const ip, const BYTE* const iHighLimit,
                        size_t best_mlen, LZ4HC_match_t* matches, const int fullUpdate)
{
    int mnum = 0;
    if (ip < ctx->base + ctx->nextToUpdate) return 0;   /* skipped area */
    if (fullUpdate) LZ4HC_updateBinTree(ctx, ip, iHighLimit);
    best_mlen = LZ4HC_BinTree_InsertAndGetAllMatches(ctx, ip, iHighLimit, best_mlen, matches, &mnum);
    ctx->nextToUpdate = (U32)(ip - ctx->base + best_mlen);
    return mnum;
}


#define SET_PRICE(pos, ml, offset, ll, cost)           \
{                                                      \
    while (last_pos < pos)  { opt[last_pos+1].price = 1<<30; last_pos++; } \
    opt[pos].mlen = (int)ml;                           \
    opt[pos].off = (int)offset;                        \
    opt[pos].litlen = (int)ll;                         \
    opt[pos].price = (int)cost;                        \
}


static int LZ4HC_compress_optimal (
    LZ4HC_CCtx_internal* ctx,
    const char* const source,
    char* dest,
    int inputSize,
    int maxOutputSize,
    limitedOutput_directive limit,
    size_t sufficient_len,
    const int fullUpdate
    )
{
    LZ4HC_optimal_t opt[LZ4_OPT_NUM + 1];   /* this uses a bit too much stack memory to my taste ... */
    LZ4HC_match_t matches[LZ4_OPT_NUM + 1];

    const BYTE* ip = (const BYTE*) source;
    const BYTE* anchor = ip;
    const BYTE* const iend = ip + inputSize;
    const BYTE* const mflimit = iend - MFLIMIT;
    const BYTE* const matchlimit = (iend - LASTLITERALS);
    BYTE* op = (BYTE*) dest;
    BYTE* const oend = op + maxOutputSize;

    /* init */
    if (sufficient_len >= LZ4_OPT_NUM) sufficient_len = LZ4_OPT_NUM-1;
    ctx->end += inputSize;
    ip++;

    /* Main Loop */
    while (ip < mflimit) {
        size_t const llen = ip - anchor;
        size_t last_pos = 0;
        size_t match_num, cur, best_mlen, best_off;
        memset(opt, 0, sizeof(LZ4HC_optimal_t));

        match_num = LZ4HC_BinTree_GetAllMatches(ctx, ip, matchlimit, MINMATCH-1, matches, fullUpdate);
        if (!match_num) { ip++; continue; }

        if ((size_t)matches[match_num-1].len > sufficient_len) {
            /* good enough solution : immediate encoding */
            best_mlen = matches[match_num-1].len;
            best_off = matches[match_num-1].off;
            cur = 0;
            last_pos = 1;
            goto encode;
        }

        /* set prices using matches at position = 0 */
        {   size_t matchNb;
            for (matchNb = 0; matchNb < match_num; matchNb++) {
                size_t mlen = (matchNb>0) ? (size_t)matches[matchNb-1].len+1 : MINMATCH;
                best_mlen = matches[matchNb].len;   /* necessarily < sufficient_len < LZ4_OPT_NUM */
                for ( ; mlen <= best_mlen ; mlen++) {
                    size_t const cost = LZ4HC_sequencePrice(llen, mlen) - LZ4HC_literalsPrice(llen);
                    SET_PRICE(mlen, mlen, matches[matchNb].off, 0, cost);   /* updates last_pos and opt[pos] */
        }   }   }

        if (last_pos < MINMATCH) { ip++; continue; }  /* note : on clang at least, this test improves performance */

        /* check further positions */
        opt[0].mlen = opt[1].mlen = 1;
        for (cur = 1; cur <= last_pos; cur++) {
            const BYTE* const curPtr = ip + cur;

            /* establish baseline price if cur is literal */
            {   size_t price, litlen;
                if (opt[cur-1].mlen == 1) {
                    /* no match at previous position */
                    litlen = opt[cur-1].litlen + 1;
                    if (cur > litlen) {
                        price = opt[cur - litlen].price + LZ4HC_literalsPrice(litlen);
                    } else {
                        price = LZ4HC_literalsPrice(llen + litlen) - LZ4HC_literalsPrice(llen);
                    }
                } else {
                    litlen = 1;
                    price = opt[cur - 1].price + LZ4HC_literalsPrice(1);
                }

                best_mlen = 0;
                if (price < (size_t)opt[cur].price)
                    SET_PRICE(cur, 1, 0, litlen, price);   /* note : increases last_pos */
            }

            if (cur == last_pos || curPtr >= mflimit) break;

            match_num = LZ4HC_BinTree_GetAllMatches(ctx, curPtr, matchlimit, MINMATCH-1, matches, fullUpdate);
            if ((match_num > 0) && (size_t)matches[match_num-1].len > sufficient_len) {
                /* immediate encoding */
                best_mlen = matches[match_num-1].len;
                best_off = matches[match_num-1].off;
                last_pos = cur + 1;
                goto encode;
            }

            /* set prices using matches at position = cur */
            {   size_t matchNb;
                for (matchNb = 0; matchNb < match_num; matchNb++) {
                    size_t ml = (matchNb>0) ? (size_t)matches[matchNb-1].len+1 : MINMATCH;
                    best_mlen = (cur + matches[matchNb].len < LZ4_OPT_NUM) ?
                                (size_t)matches[matchNb].len : LZ4_OPT_NUM - cur;

                    for ( ; ml <= best_mlen ; ml++) {
                        size_t ll, price;
                        if (opt[cur].mlen == 1) {
                            ll = opt[cur].litlen;
                            if (cur > ll)
                                price = opt[cur - ll].price + LZ4HC_sequencePrice(ll, ml);
                            else
                                price = LZ4HC_sequencePrice(llen + ll, ml) - LZ4HC_literalsPrice(llen);
                        } else {
                            ll = 0;
                            price = opt[cur].price + LZ4HC_sequencePrice(0, ml);
                        }

                        if (cur + ml > last_pos || price < (size_t)opt[cur + ml].price) {
                            SET_PRICE(cur + ml, ml, matches[matchNb].off, ll, price);
            }   }   }   }
        } /* for (cur = 1; cur <= last_pos; cur++) */

        best_mlen = opt[last_pos].mlen;
        best_off = opt[last_pos].off;
        cur = last_pos - best_mlen;

encode: /* cur, last_pos, best_mlen, best_off must be set */
        opt[0].mlen = 1;
        while (1) {  /* from end to beginning */
            size_t const ml = opt[cur].mlen;
            int const offset = opt[cur].off;
            opt[cur].mlen = (int)best_mlen;
            opt[cur].off = (int)best_off;
            best_mlen = ml;
            best_off = offset;
            if (ml > cur) break;
            cur -= ml;
        }

        /* encode all recorded sequences */
        cur = 0;
        while (cur < last_pos) {
            int const ml = opt[cur].mlen;
            int const offset = opt[cur].off;
            if (ml == 1) { ip++; cur++; continue; }
            cur += ml;
            if ( LZ4HC_encodeSequence(&ip, &op, &anchor, ml, ip - offset, limit, oend) ) return 0;
        }
    }  /* while (ip < mflimit) */

    /* Encode Last Literals */
    {   int lastRun = (int)(iend - anchor);
        if ((limit) && (((char*)op - dest) + lastRun + 1 + ((lastRun+255-RUN_MASK)/255) > (U32)maxOutputSize)) return 0;  /* Check output limit */
        if (lastRun>=(int)RUN_MASK) { *op++=(RUN_MASK<<ML_BITS); lastRun-=RUN_MASK; for(; lastRun > 254 ; lastRun-=255) *op++ = 255; *op++ = (BYTE) lastRun; }
        else *op++ = (BYTE)(lastRun<<ML_BITS);
        memcpy(op, anchor, iend - anchor);
        op += iend-anchor;
    }

    /* End */
    return (int) ((char*)op-dest);
}