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1 | /* |
2 | * Copyright (c) Yann Collet, Facebook, Inc. | |
3 | * All rights reserved. | |
4 | * | |
5 | * This source code is licensed under both the BSD-style license (found in the | |
6 | * LICENSE file in the root directory of this source tree) and the GPLv2 (found | |
7 | * in the COPYING file in the root directory of this source tree). | |
8 | * You may select, at your option, one of the above-listed licenses. | |
9 | */ | |
10 | ||
11 | #include "zstd_ldm.h" | |
12 | ||
13 | #include "../common/debug.h" | |
14 | #include <linux/xxhash.h> | |
15 | #include "zstd_fast.h" /* ZSTD_fillHashTable() */ | |
16 | #include "zstd_double_fast.h" /* ZSTD_fillDoubleHashTable() */ | |
17 | #include "zstd_ldm_geartab.h" | |
18 | ||
19 | #define LDM_BUCKET_SIZE_LOG 3 | |
20 | #define LDM_MIN_MATCH_LENGTH 64 | |
21 | #define LDM_HASH_RLOG 7 | |
22 | ||
23 | typedef struct { | |
24 | U64 rolling; | |
25 | U64 stopMask; | |
26 | } ldmRollingHashState_t; | |
27 | ||
28 | /* ZSTD_ldm_gear_init(): | |
29 | * | |
30 | * Initializes the rolling hash state such that it will honor the | |
31 | * settings in params. */ | |
32 | static void ZSTD_ldm_gear_init(ldmRollingHashState_t* state, ldmParams_t const* params) | |
33 | { | |
34 | unsigned maxBitsInMask = MIN(params->minMatchLength, 64); | |
35 | unsigned hashRateLog = params->hashRateLog; | |
36 | ||
37 | state->rolling = ~(U32)0; | |
38 | ||
39 | /* The choice of the splitting criterion is subject to two conditions: | |
40 | * 1. it has to trigger on average every 2^(hashRateLog) bytes; | |
41 | * 2. ideally, it has to depend on a window of minMatchLength bytes. | |
42 | * | |
43 | * In the gear hash algorithm, bit n depends on the last n bytes; | |
44 | * so in order to obtain a good quality splitting criterion it is | |
45 | * preferable to use bits with high weight. | |
46 | * | |
47 | * To match condition 1 we use a mask with hashRateLog bits set | |
48 | * and, because of the previous remark, we make sure these bits | |
49 | * have the highest possible weight while still respecting | |
50 | * condition 2. | |
51 | */ | |
52 | if (hashRateLog > 0 && hashRateLog <= maxBitsInMask) { | |
53 | state->stopMask = (((U64)1 << hashRateLog) - 1) << (maxBitsInMask - hashRateLog); | |
54 | } else { | |
55 | /* In this degenerate case we simply honor the hash rate. */ | |
56 | state->stopMask = ((U64)1 << hashRateLog) - 1; | |
57 | } | |
58 | } | |
59 | ||
60 | /* ZSTD_ldm_gear_feed(): | |
61 | * | |
62 | * Registers in the splits array all the split points found in the first | |
63 | * size bytes following the data pointer. This function terminates when | |
64 | * either all the data has been processed or LDM_BATCH_SIZE splits are | |
65 | * present in the splits array. | |
66 | * | |
67 | * Precondition: The splits array must not be full. | |
68 | * Returns: The number of bytes processed. */ | |
69 | static size_t ZSTD_ldm_gear_feed(ldmRollingHashState_t* state, | |
70 | BYTE const* data, size_t size, | |
71 | size_t* splits, unsigned* numSplits) | |
72 | { | |
73 | size_t n; | |
74 | U64 hash, mask; | |
75 | ||
76 | hash = state->rolling; | |
77 | mask = state->stopMask; | |
78 | n = 0; | |
79 | ||
80 | #define GEAR_ITER_ONCE() do { \ | |
81 | hash = (hash << 1) + ZSTD_ldm_gearTab[data[n] & 0xff]; \ | |
82 | n += 1; \ | |
83 | if (UNLIKELY((hash & mask) == 0)) { \ | |
84 | splits[*numSplits] = n; \ | |
85 | *numSplits += 1; \ | |
86 | if (*numSplits == LDM_BATCH_SIZE) \ | |
87 | goto done; \ | |
88 | } \ | |
89 | } while (0) | |
90 | ||
91 | while (n + 3 < size) { | |
92 | GEAR_ITER_ONCE(); | |
93 | GEAR_ITER_ONCE(); | |
94 | GEAR_ITER_ONCE(); | |
95 | GEAR_ITER_ONCE(); | |
96 | } | |
97 | while (n < size) { | |
98 | GEAR_ITER_ONCE(); | |
99 | } | |
100 | ||
101 | #undef GEAR_ITER_ONCE | |
102 | ||
103 | done: | |
104 | state->rolling = hash; | |
105 | return n; | |
106 | } | |
107 | ||
108 | void ZSTD_ldm_adjustParameters(ldmParams_t* params, | |
109 | ZSTD_compressionParameters const* cParams) | |
110 | { | |
111 | params->windowLog = cParams->windowLog; | |
112 | ZSTD_STATIC_ASSERT(LDM_BUCKET_SIZE_LOG <= ZSTD_LDM_BUCKETSIZELOG_MAX); | |
113 | DEBUGLOG(4, "ZSTD_ldm_adjustParameters"); | |
114 | if (!params->bucketSizeLog) params->bucketSizeLog = LDM_BUCKET_SIZE_LOG; | |
115 | if (!params->minMatchLength) params->minMatchLength = LDM_MIN_MATCH_LENGTH; | |
116 | if (params->hashLog == 0) { | |
117 | params->hashLog = MAX(ZSTD_HASHLOG_MIN, params->windowLog - LDM_HASH_RLOG); | |
118 | assert(params->hashLog <= ZSTD_HASHLOG_MAX); | |
119 | } | |
120 | if (params->hashRateLog == 0) { | |
121 | params->hashRateLog = params->windowLog < params->hashLog | |
122 | ? 0 | |
123 | : params->windowLog - params->hashLog; | |
124 | } | |
125 | params->bucketSizeLog = MIN(params->bucketSizeLog, params->hashLog); | |
126 | } | |
127 | ||
128 | size_t ZSTD_ldm_getTableSize(ldmParams_t params) | |
129 | { | |
130 | size_t const ldmHSize = ((size_t)1) << params.hashLog; | |
131 | size_t const ldmBucketSizeLog = MIN(params.bucketSizeLog, params.hashLog); | |
132 | size_t const ldmBucketSize = ((size_t)1) << (params.hashLog - ldmBucketSizeLog); | |
133 | size_t const totalSize = ZSTD_cwksp_alloc_size(ldmBucketSize) | |
134 | + ZSTD_cwksp_alloc_size(ldmHSize * sizeof(ldmEntry_t)); | |
135 | return params.enableLdm ? totalSize : 0; | |
136 | } | |
137 | ||
138 | size_t ZSTD_ldm_getMaxNbSeq(ldmParams_t params, size_t maxChunkSize) | |
139 | { | |
140 | return params.enableLdm ? (maxChunkSize / params.minMatchLength) : 0; | |
141 | } | |
142 | ||
143 | /* ZSTD_ldm_getBucket() : | |
144 | * Returns a pointer to the start of the bucket associated with hash. */ | |
145 | static ldmEntry_t* ZSTD_ldm_getBucket( | |
146 | ldmState_t* ldmState, size_t hash, ldmParams_t const ldmParams) | |
147 | { | |
148 | return ldmState->hashTable + (hash << ldmParams.bucketSizeLog); | |
149 | } | |
150 | ||
151 | /* ZSTD_ldm_insertEntry() : | |
152 | * Insert the entry with corresponding hash into the hash table */ | |
153 | static void ZSTD_ldm_insertEntry(ldmState_t* ldmState, | |
154 | size_t const hash, const ldmEntry_t entry, | |
155 | ldmParams_t const ldmParams) | |
156 | { | |
157 | BYTE* const pOffset = ldmState->bucketOffsets + hash; | |
158 | unsigned const offset = *pOffset; | |
159 | ||
160 | *(ZSTD_ldm_getBucket(ldmState, hash, ldmParams) + offset) = entry; | |
161 | *pOffset = (BYTE)((offset + 1) & ((1u << ldmParams.bucketSizeLog) - 1)); | |
162 | ||
163 | } | |
164 | ||
165 | /* ZSTD_ldm_countBackwardsMatch() : | |
166 | * Returns the number of bytes that match backwards before pIn and pMatch. | |
167 | * | |
168 | * We count only bytes where pMatch >= pBase and pIn >= pAnchor. */ | |
169 | static size_t ZSTD_ldm_countBackwardsMatch( | |
170 | const BYTE* pIn, const BYTE* pAnchor, | |
171 | const BYTE* pMatch, const BYTE* pMatchBase) | |
172 | { | |
173 | size_t matchLength = 0; | |
174 | while (pIn > pAnchor && pMatch > pMatchBase && pIn[-1] == pMatch[-1]) { | |
175 | pIn--; | |
176 | pMatch--; | |
177 | matchLength++; | |
178 | } | |
179 | return matchLength; | |
180 | } | |
181 | ||
182 | /* ZSTD_ldm_countBackwardsMatch_2segments() : | |
183 | * Returns the number of bytes that match backwards from pMatch, | |
184 | * even with the backwards match spanning 2 different segments. | |
185 | * | |
186 | * On reaching `pMatchBase`, start counting from mEnd */ | |
187 | static size_t ZSTD_ldm_countBackwardsMatch_2segments( | |
188 | const BYTE* pIn, const BYTE* pAnchor, | |
189 | const BYTE* pMatch, const BYTE* pMatchBase, | |
190 | const BYTE* pExtDictStart, const BYTE* pExtDictEnd) | |
191 | { | |
192 | size_t matchLength = ZSTD_ldm_countBackwardsMatch(pIn, pAnchor, pMatch, pMatchBase); | |
193 | if (pMatch - matchLength != pMatchBase || pMatchBase == pExtDictStart) { | |
194 | /* If backwards match is entirely in the extDict or prefix, immediately return */ | |
195 | return matchLength; | |
196 | } | |
197 | DEBUGLOG(7, "ZSTD_ldm_countBackwardsMatch_2segments: found 2-parts backwards match (length in prefix==%zu)", matchLength); | |
198 | matchLength += ZSTD_ldm_countBackwardsMatch(pIn - matchLength, pAnchor, pExtDictEnd, pExtDictStart); | |
199 | DEBUGLOG(7, "final backwards match length = %zu", matchLength); | |
200 | return matchLength; | |
201 | } | |
202 | ||
203 | /* ZSTD_ldm_fillFastTables() : | |
204 | * | |
205 | * Fills the relevant tables for the ZSTD_fast and ZSTD_dfast strategies. | |
206 | * This is similar to ZSTD_loadDictionaryContent. | |
207 | * | |
208 | * The tables for the other strategies are filled within their | |
209 | * block compressors. */ | |
210 | static size_t ZSTD_ldm_fillFastTables(ZSTD_matchState_t* ms, | |
211 | void const* end) | |
212 | { | |
213 | const BYTE* const iend = (const BYTE*)end; | |
214 | ||
215 | switch(ms->cParams.strategy) | |
216 | { | |
217 | case ZSTD_fast: | |
218 | ZSTD_fillHashTable(ms, iend, ZSTD_dtlm_fast); | |
219 | break; | |
220 | ||
221 | case ZSTD_dfast: | |
222 | ZSTD_fillDoubleHashTable(ms, iend, ZSTD_dtlm_fast); | |
223 | break; | |
224 | ||
225 | case ZSTD_greedy: | |
226 | case ZSTD_lazy: | |
227 | case ZSTD_lazy2: | |
228 | case ZSTD_btlazy2: | |
229 | case ZSTD_btopt: | |
230 | case ZSTD_btultra: | |
231 | case ZSTD_btultra2: | |
232 | break; | |
233 | default: | |
234 | assert(0); /* not possible : not a valid strategy id */ | |
235 | } | |
236 | ||
237 | return 0; | |
238 | } | |
239 | ||
240 | void ZSTD_ldm_fillHashTable( | |
241 | ldmState_t* ldmState, const BYTE* ip, | |
242 | const BYTE* iend, ldmParams_t const* params) | |
243 | { | |
244 | U32 const minMatchLength = params->minMatchLength; | |
245 | U32 const hBits = params->hashLog - params->bucketSizeLog; | |
246 | BYTE const* const base = ldmState->window.base; | |
247 | BYTE const* const istart = ip; | |
248 | ldmRollingHashState_t hashState; | |
249 | size_t* const splits = ldmState->splitIndices; | |
250 | unsigned numSplits; | |
251 | ||
252 | DEBUGLOG(5, "ZSTD_ldm_fillHashTable"); | |
253 | ||
254 | ZSTD_ldm_gear_init(&hashState, params); | |
255 | while (ip < iend) { | |
256 | size_t hashed; | |
257 | unsigned n; | |
258 | ||
259 | numSplits = 0; | |
260 | hashed = ZSTD_ldm_gear_feed(&hashState, ip, iend - ip, splits, &numSplits); | |
261 | ||
262 | for (n = 0; n < numSplits; n++) { | |
263 | if (ip + splits[n] >= istart + minMatchLength) { | |
264 | BYTE const* const split = ip + splits[n] - minMatchLength; | |
265 | U64 const xxhash = xxh64(split, minMatchLength, 0); | |
266 | U32 const hash = (U32)(xxhash & (((U32)1 << hBits) - 1)); | |
267 | ldmEntry_t entry; | |
268 | ||
269 | entry.offset = (U32)(split - base); | |
270 | entry.checksum = (U32)(xxhash >> 32); | |
271 | ZSTD_ldm_insertEntry(ldmState, hash, entry, *params); | |
272 | } | |
273 | } | |
274 | ||
275 | ip += hashed; | |
276 | } | |
277 | } | |
278 | ||
279 | ||
280 | /* ZSTD_ldm_limitTableUpdate() : | |
281 | * | |
282 | * Sets cctx->nextToUpdate to a position corresponding closer to anchor | |
283 | * if it is far way | |
284 | * (after a long match, only update tables a limited amount). */ | |
285 | static void ZSTD_ldm_limitTableUpdate(ZSTD_matchState_t* ms, const BYTE* anchor) | |
286 | { | |
287 | U32 const curr = (U32)(anchor - ms->window.base); | |
288 | if (curr > ms->nextToUpdate + 1024) { | |
289 | ms->nextToUpdate = | |
290 | curr - MIN(512, curr - ms->nextToUpdate - 1024); | |
291 | } | |
292 | } | |
293 | ||
294 | static size_t ZSTD_ldm_generateSequences_internal( | |
295 | ldmState_t* ldmState, rawSeqStore_t* rawSeqStore, | |
296 | ldmParams_t const* params, void const* src, size_t srcSize) | |
297 | { | |
298 | /* LDM parameters */ | |
299 | int const extDict = ZSTD_window_hasExtDict(ldmState->window); | |
300 | U32 const minMatchLength = params->minMatchLength; | |
301 | U32 const entsPerBucket = 1U << params->bucketSizeLog; | |
302 | U32 const hBits = params->hashLog - params->bucketSizeLog; | |
303 | /* Prefix and extDict parameters */ | |
304 | U32 const dictLimit = ldmState->window.dictLimit; | |
305 | U32 const lowestIndex = extDict ? ldmState->window.lowLimit : dictLimit; | |
306 | BYTE const* const base = ldmState->window.base; | |
307 | BYTE const* const dictBase = extDict ? ldmState->window.dictBase : NULL; | |
308 | BYTE const* const dictStart = extDict ? dictBase + lowestIndex : NULL; | |
309 | BYTE const* const dictEnd = extDict ? dictBase + dictLimit : NULL; | |
310 | BYTE const* const lowPrefixPtr = base + dictLimit; | |
311 | /* Input bounds */ | |
312 | BYTE const* const istart = (BYTE const*)src; | |
313 | BYTE const* const iend = istart + srcSize; | |
314 | BYTE const* const ilimit = iend - HASH_READ_SIZE; | |
315 | /* Input positions */ | |
316 | BYTE const* anchor = istart; | |
317 | BYTE const* ip = istart; | |
318 | /* Rolling hash state */ | |
319 | ldmRollingHashState_t hashState; | |
320 | /* Arrays for staged-processing */ | |
321 | size_t* const splits = ldmState->splitIndices; | |
322 | ldmMatchCandidate_t* const candidates = ldmState->matchCandidates; | |
323 | unsigned numSplits; | |
324 | ||
325 | if (srcSize < minMatchLength) | |
326 | return iend - anchor; | |
327 | ||
328 | /* Initialize the rolling hash state with the first minMatchLength bytes */ | |
329 | ZSTD_ldm_gear_init(&hashState, params); | |
330 | { | |
331 | size_t n = 0; | |
332 | ||
333 | while (n < minMatchLength) { | |
334 | numSplits = 0; | |
335 | n += ZSTD_ldm_gear_feed(&hashState, ip + n, minMatchLength - n, | |
336 | splits, &numSplits); | |
337 | } | |
338 | ip += minMatchLength; | |
339 | } | |
340 | ||
341 | while (ip < ilimit) { | |
342 | size_t hashed; | |
343 | unsigned n; | |
344 | ||
345 | numSplits = 0; | |
346 | hashed = ZSTD_ldm_gear_feed(&hashState, ip, ilimit - ip, | |
347 | splits, &numSplits); | |
348 | ||
349 | for (n = 0; n < numSplits; n++) { | |
350 | BYTE const* const split = ip + splits[n] - minMatchLength; | |
351 | U64 const xxhash = xxh64(split, minMatchLength, 0); | |
352 | U32 const hash = (U32)(xxhash & (((U32)1 << hBits) - 1)); | |
353 | ||
354 | candidates[n].split = split; | |
355 | candidates[n].hash = hash; | |
356 | candidates[n].checksum = (U32)(xxhash >> 32); | |
357 | candidates[n].bucket = ZSTD_ldm_getBucket(ldmState, hash, *params); | |
358 | PREFETCH_L1(candidates[n].bucket); | |
359 | } | |
360 | ||
361 | for (n = 0; n < numSplits; n++) { | |
362 | size_t forwardMatchLength = 0, backwardMatchLength = 0, | |
363 | bestMatchLength = 0, mLength; | |
364 | BYTE const* const split = candidates[n].split; | |
365 | U32 const checksum = candidates[n].checksum; | |
366 | U32 const hash = candidates[n].hash; | |
367 | ldmEntry_t* const bucket = candidates[n].bucket; | |
368 | ldmEntry_t const* cur; | |
369 | ldmEntry_t const* bestEntry = NULL; | |
370 | ldmEntry_t newEntry; | |
371 | ||
372 | newEntry.offset = (U32)(split - base); | |
373 | newEntry.checksum = checksum; | |
374 | ||
375 | /* If a split point would generate a sequence overlapping with | |
376 | * the previous one, we merely register it in the hash table and | |
377 | * move on */ | |
378 | if (split < anchor) { | |
379 | ZSTD_ldm_insertEntry(ldmState, hash, newEntry, *params); | |
380 | continue; | |
381 | } | |
382 | ||
383 | for (cur = bucket; cur < bucket + entsPerBucket; cur++) { | |
384 | size_t curForwardMatchLength, curBackwardMatchLength, | |
385 | curTotalMatchLength; | |
386 | if (cur->checksum != checksum || cur->offset <= lowestIndex) { | |
387 | continue; | |
388 | } | |
389 | if (extDict) { | |
390 | BYTE const* const curMatchBase = | |
391 | cur->offset < dictLimit ? dictBase : base; | |
392 | BYTE const* const pMatch = curMatchBase + cur->offset; | |
393 | BYTE const* const matchEnd = | |
394 | cur->offset < dictLimit ? dictEnd : iend; | |
395 | BYTE const* const lowMatchPtr = | |
396 | cur->offset < dictLimit ? dictStart : lowPrefixPtr; | |
397 | curForwardMatchLength = | |
398 | ZSTD_count_2segments(split, pMatch, iend, matchEnd, lowPrefixPtr); | |
399 | if (curForwardMatchLength < minMatchLength) { | |
400 | continue; | |
401 | } | |
402 | curBackwardMatchLength = ZSTD_ldm_countBackwardsMatch_2segments( | |
403 | split, anchor, pMatch, lowMatchPtr, dictStart, dictEnd); | |
404 | } else { /* !extDict */ | |
405 | BYTE const* const pMatch = base + cur->offset; | |
406 | curForwardMatchLength = ZSTD_count(split, pMatch, iend); | |
407 | if (curForwardMatchLength < minMatchLength) { | |
408 | continue; | |
409 | } | |
410 | curBackwardMatchLength = | |
411 | ZSTD_ldm_countBackwardsMatch(split, anchor, pMatch, lowPrefixPtr); | |
412 | } | |
413 | curTotalMatchLength = curForwardMatchLength + curBackwardMatchLength; | |
414 | ||
415 | if (curTotalMatchLength > bestMatchLength) { | |
416 | bestMatchLength = curTotalMatchLength; | |
417 | forwardMatchLength = curForwardMatchLength; | |
418 | backwardMatchLength = curBackwardMatchLength; | |
419 | bestEntry = cur; | |
420 | } | |
421 | } | |
422 | ||
423 | /* No match found -- insert an entry into the hash table | |
424 | * and process the next candidate match */ | |
425 | if (bestEntry == NULL) { | |
426 | ZSTD_ldm_insertEntry(ldmState, hash, newEntry, *params); | |
427 | continue; | |
428 | } | |
429 | ||
430 | /* Match found */ | |
431 | mLength = forwardMatchLength + backwardMatchLength; | |
432 | { | |
433 | U32 const offset = (U32)(split - base) - bestEntry->offset; | |
434 | rawSeq* const seq = rawSeqStore->seq + rawSeqStore->size; | |
435 | ||
436 | /* Out of sequence storage */ | |
437 | if (rawSeqStore->size == rawSeqStore->capacity) | |
438 | return ERROR(dstSize_tooSmall); | |
439 | seq->litLength = (U32)(split - backwardMatchLength - anchor); | |
440 | seq->matchLength = (U32)mLength; | |
441 | seq->offset = offset; | |
442 | rawSeqStore->size++; | |
443 | } | |
444 | ||
445 | /* Insert the current entry into the hash table --- it must be | |
446 | * done after the previous block to avoid clobbering bestEntry */ | |
447 | ZSTD_ldm_insertEntry(ldmState, hash, newEntry, *params); | |
448 | ||
449 | anchor = split + forwardMatchLength; | |
450 | } | |
451 | ||
452 | ip += hashed; | |
453 | } | |
454 | ||
455 | return iend - anchor; | |
456 | } | |
457 | ||
458 | /*! ZSTD_ldm_reduceTable() : | |
459 | * reduce table indexes by `reducerValue` */ | |
460 | static void ZSTD_ldm_reduceTable(ldmEntry_t* const table, U32 const size, | |
461 | U32 const reducerValue) | |
462 | { | |
463 | U32 u; | |
464 | for (u = 0; u < size; u++) { | |
465 | if (table[u].offset < reducerValue) table[u].offset = 0; | |
466 | else table[u].offset -= reducerValue; | |
467 | } | |
468 | } | |
469 | ||
470 | size_t ZSTD_ldm_generateSequences( | |
471 | ldmState_t* ldmState, rawSeqStore_t* sequences, | |
472 | ldmParams_t const* params, void const* src, size_t srcSize) | |
473 | { | |
474 | U32 const maxDist = 1U << params->windowLog; | |
475 | BYTE const* const istart = (BYTE const*)src; | |
476 | BYTE const* const iend = istart + srcSize; | |
477 | size_t const kMaxChunkSize = 1 << 20; | |
478 | size_t const nbChunks = (srcSize / kMaxChunkSize) + ((srcSize % kMaxChunkSize) != 0); | |
479 | size_t chunk; | |
480 | size_t leftoverSize = 0; | |
481 | ||
482 | assert(ZSTD_CHUNKSIZE_MAX >= kMaxChunkSize); | |
483 | /* Check that ZSTD_window_update() has been called for this chunk prior | |
484 | * to passing it to this function. | |
485 | */ | |
486 | assert(ldmState->window.nextSrc >= (BYTE const*)src + srcSize); | |
487 | /* The input could be very large (in zstdmt), so it must be broken up into | |
488 | * chunks to enforce the maximum distance and handle overflow correction. | |
489 | */ | |
490 | assert(sequences->pos <= sequences->size); | |
491 | assert(sequences->size <= sequences->capacity); | |
492 | for (chunk = 0; chunk < nbChunks && sequences->size < sequences->capacity; ++chunk) { | |
493 | BYTE const* const chunkStart = istart + chunk * kMaxChunkSize; | |
494 | size_t const remaining = (size_t)(iend - chunkStart); | |
495 | BYTE const *const chunkEnd = | |
496 | (remaining < kMaxChunkSize) ? iend : chunkStart + kMaxChunkSize; | |
497 | size_t const chunkSize = chunkEnd - chunkStart; | |
498 | size_t newLeftoverSize; | |
499 | size_t const prevSize = sequences->size; | |
500 | ||
501 | assert(chunkStart < iend); | |
502 | /* 1. Perform overflow correction if necessary. */ | |
503 | if (ZSTD_window_needOverflowCorrection(ldmState->window, chunkEnd)) { | |
504 | U32 const ldmHSize = 1U << params->hashLog; | |
505 | U32 const correction = ZSTD_window_correctOverflow( | |
506 | &ldmState->window, /* cycleLog */ 0, maxDist, chunkStart); | |
507 | ZSTD_ldm_reduceTable(ldmState->hashTable, ldmHSize, correction); | |
508 | /* invalidate dictionaries on overflow correction */ | |
509 | ldmState->loadedDictEnd = 0; | |
510 | } | |
511 | /* 2. We enforce the maximum offset allowed. | |
512 | * | |
513 | * kMaxChunkSize should be small enough that we don't lose too much of | |
514 | * the window through early invalidation. | |
515 | * TODO: * Test the chunk size. | |
516 | * * Try invalidation after the sequence generation and test the | |
517 | * the offset against maxDist directly. | |
518 | * | |
519 | * NOTE: Because of dictionaries + sequence splitting we MUST make sure | |
520 | * that any offset used is valid at the END of the sequence, since it may | |
521 | * be split into two sequences. This condition holds when using | |
522 | * ZSTD_window_enforceMaxDist(), but if we move to checking offsets | |
523 | * against maxDist directly, we'll have to carefully handle that case. | |
524 | */ | |
525 | ZSTD_window_enforceMaxDist(&ldmState->window, chunkEnd, maxDist, &ldmState->loadedDictEnd, NULL); | |
526 | /* 3. Generate the sequences for the chunk, and get newLeftoverSize. */ | |
527 | newLeftoverSize = ZSTD_ldm_generateSequences_internal( | |
528 | ldmState, sequences, params, chunkStart, chunkSize); | |
529 | if (ZSTD_isError(newLeftoverSize)) | |
530 | return newLeftoverSize; | |
531 | /* 4. We add the leftover literals from previous iterations to the first | |
532 | * newly generated sequence, or add the `newLeftoverSize` if none are | |
533 | * generated. | |
534 | */ | |
535 | /* Prepend the leftover literals from the last call */ | |
536 | if (prevSize < sequences->size) { | |
537 | sequences->seq[prevSize].litLength += (U32)leftoverSize; | |
538 | leftoverSize = newLeftoverSize; | |
539 | } else { | |
540 | assert(newLeftoverSize == chunkSize); | |
541 | leftoverSize += chunkSize; | |
542 | } | |
543 | } | |
544 | return 0; | |
545 | } | |
546 | ||
547 | void ZSTD_ldm_skipSequences(rawSeqStore_t* rawSeqStore, size_t srcSize, U32 const minMatch) { | |
548 | while (srcSize > 0 && rawSeqStore->pos < rawSeqStore->size) { | |
549 | rawSeq* seq = rawSeqStore->seq + rawSeqStore->pos; | |
550 | if (srcSize <= seq->litLength) { | |
551 | /* Skip past srcSize literals */ | |
552 | seq->litLength -= (U32)srcSize; | |
553 | return; | |
554 | } | |
555 | srcSize -= seq->litLength; | |
556 | seq->litLength = 0; | |
557 | if (srcSize < seq->matchLength) { | |
558 | /* Skip past the first srcSize of the match */ | |
559 | seq->matchLength -= (U32)srcSize; | |
560 | if (seq->matchLength < minMatch) { | |
561 | /* The match is too short, omit it */ | |
562 | if (rawSeqStore->pos + 1 < rawSeqStore->size) { | |
563 | seq[1].litLength += seq[0].matchLength; | |
564 | } | |
565 | rawSeqStore->pos++; | |
566 | } | |
567 | return; | |
568 | } | |
569 | srcSize -= seq->matchLength; | |
570 | seq->matchLength = 0; | |
571 | rawSeqStore->pos++; | |
572 | } | |
573 | } | |
574 | ||
575 | /* | |
576 | * If the sequence length is longer than remaining then the sequence is split | |
577 | * between this block and the next. | |
578 | * | |
579 | * Returns the current sequence to handle, or if the rest of the block should | |
580 | * be literals, it returns a sequence with offset == 0. | |
581 | */ | |
582 | static rawSeq maybeSplitSequence(rawSeqStore_t* rawSeqStore, | |
583 | U32 const remaining, U32 const minMatch) | |
584 | { | |
585 | rawSeq sequence = rawSeqStore->seq[rawSeqStore->pos]; | |
586 | assert(sequence.offset > 0); | |
587 | /* Likely: No partial sequence */ | |
588 | if (remaining >= sequence.litLength + sequence.matchLength) { | |
589 | rawSeqStore->pos++; | |
590 | return sequence; | |
591 | } | |
592 | /* Cut the sequence short (offset == 0 ==> rest is literals). */ | |
593 | if (remaining <= sequence.litLength) { | |
594 | sequence.offset = 0; | |
595 | } else if (remaining < sequence.litLength + sequence.matchLength) { | |
596 | sequence.matchLength = remaining - sequence.litLength; | |
597 | if (sequence.matchLength < minMatch) { | |
598 | sequence.offset = 0; | |
599 | } | |
600 | } | |
601 | /* Skip past `remaining` bytes for the future sequences. */ | |
602 | ZSTD_ldm_skipSequences(rawSeqStore, remaining, minMatch); | |
603 | return sequence; | |
604 | } | |
605 | ||
606 | void ZSTD_ldm_skipRawSeqStoreBytes(rawSeqStore_t* rawSeqStore, size_t nbBytes) { | |
607 | U32 currPos = (U32)(rawSeqStore->posInSequence + nbBytes); | |
608 | while (currPos && rawSeqStore->pos < rawSeqStore->size) { | |
609 | rawSeq currSeq = rawSeqStore->seq[rawSeqStore->pos]; | |
610 | if (currPos >= currSeq.litLength + currSeq.matchLength) { | |
611 | currPos -= currSeq.litLength + currSeq.matchLength; | |
612 | rawSeqStore->pos++; | |
613 | } else { | |
614 | rawSeqStore->posInSequence = currPos; | |
615 | break; | |
616 | } | |
617 | } | |
618 | if (currPos == 0 || rawSeqStore->pos == rawSeqStore->size) { | |
619 | rawSeqStore->posInSequence = 0; | |
620 | } | |
621 | } | |
622 | ||
623 | size_t ZSTD_ldm_blockCompress(rawSeqStore_t* rawSeqStore, | |
624 | ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM], | |
625 | void const* src, size_t srcSize) | |
626 | { | |
627 | const ZSTD_compressionParameters* const cParams = &ms->cParams; | |
628 | unsigned const minMatch = cParams->minMatch; | |
629 | ZSTD_blockCompressor const blockCompressor = | |
630 | ZSTD_selectBlockCompressor(cParams->strategy, ZSTD_matchState_dictMode(ms)); | |
631 | /* Input bounds */ | |
632 | BYTE const* const istart = (BYTE const*)src; | |
633 | BYTE const* const iend = istart + srcSize; | |
634 | /* Input positions */ | |
635 | BYTE const* ip = istart; | |
636 | ||
637 | DEBUGLOG(5, "ZSTD_ldm_blockCompress: srcSize=%zu", srcSize); | |
638 | /* If using opt parser, use LDMs only as candidates rather than always accepting them */ | |
639 | if (cParams->strategy >= ZSTD_btopt) { | |
640 | size_t lastLLSize; | |
641 | ms->ldmSeqStore = rawSeqStore; | |
642 | lastLLSize = blockCompressor(ms, seqStore, rep, src, srcSize); | |
643 | ZSTD_ldm_skipRawSeqStoreBytes(rawSeqStore, srcSize); | |
644 | return lastLLSize; | |
645 | } | |
646 | ||
647 | assert(rawSeqStore->pos <= rawSeqStore->size); | |
648 | assert(rawSeqStore->size <= rawSeqStore->capacity); | |
649 | /* Loop through each sequence and apply the block compressor to the literals */ | |
650 | while (rawSeqStore->pos < rawSeqStore->size && ip < iend) { | |
651 | /* maybeSplitSequence updates rawSeqStore->pos */ | |
652 | rawSeq const sequence = maybeSplitSequence(rawSeqStore, | |
653 | (U32)(iend - ip), minMatch); | |
654 | int i; | |
655 | /* End signal */ | |
656 | if (sequence.offset == 0) | |
657 | break; | |
658 | ||
659 | assert(ip + sequence.litLength + sequence.matchLength <= iend); | |
660 | ||
661 | /* Fill tables for block compressor */ | |
662 | ZSTD_ldm_limitTableUpdate(ms, ip); | |
663 | ZSTD_ldm_fillFastTables(ms, ip); | |
664 | /* Run the block compressor */ | |
665 | DEBUGLOG(5, "pos %u : calling block compressor on segment of size %u", (unsigned)(ip-istart), sequence.litLength); | |
666 | { | |
667 | size_t const newLitLength = | |
668 | blockCompressor(ms, seqStore, rep, ip, sequence.litLength); | |
669 | ip += sequence.litLength; | |
670 | /* Update the repcodes */ | |
671 | for (i = ZSTD_REP_NUM - 1; i > 0; i--) | |
672 | rep[i] = rep[i-1]; | |
673 | rep[0] = sequence.offset; | |
674 | /* Store the sequence */ | |
675 | ZSTD_storeSeq(seqStore, newLitLength, ip - newLitLength, iend, | |
676 | sequence.offset + ZSTD_REP_MOVE, | |
677 | sequence.matchLength - MINMATCH); | |
678 | ip += sequence.matchLength; | |
679 | } | |
680 | } | |
681 | /* Fill the tables for the block compressor */ | |
682 | ZSTD_ldm_limitTableUpdate(ms, ip); | |
683 | ZSTD_ldm_fillFastTables(ms, ip); | |
684 | /* Compress the last literals */ | |
685 | return blockCompressor(ms, seqStore, rep, ip, iend - ip); | |
686 | } |