/* * Copyright (c) 2016-present, Yann Collet, Facebook, Inc. * All rights reserved. * * This source code is licensed under both the BSD-style license (found in the * LICENSE file in the root directory of this source tree) and the GPLv2 (found * in the COPYING file in the root directory of this source tree). */ #include "zstd_ldm.h" #include "zstd_fast.h" /* ZSTD_fillHashTable() */ #include "zstd_double_fast.h" /* ZSTD_fillDoubleHashTable() */ #define LDM_BUCKET_SIZE_LOG 3 #define LDM_MIN_MATCH_LENGTH 64 #define LDM_HASH_RLOG 7 #define LDM_HASH_CHAR_OFFSET 10 void ZSTD_ldm_adjustParameters(ldmParams_t* params, ZSTD_compressionParameters const* cParams) { U32 const windowLog = cParams->windowLog; ZSTD_STATIC_ASSERT(LDM_BUCKET_SIZE_LOG <= ZSTD_LDM_BUCKETSIZELOG_MAX); DEBUGLOG(4, "ZSTD_ldm_adjustParameters"); if (!params->bucketSizeLog) params->bucketSizeLog = LDM_BUCKET_SIZE_LOG; if (!params->minMatchLength) params->minMatchLength = LDM_MIN_MATCH_LENGTH; if (cParams->strategy >= ZSTD_btopt) { /* Get out of the way of the optimal parser */ U32 const minMatch = MAX(cParams->targetLength, params->minMatchLength); assert(minMatch >= ZSTD_LDM_MINMATCH_MIN); assert(minMatch <= ZSTD_LDM_MINMATCH_MAX); params->minMatchLength = minMatch; } if (params->hashLog == 0) { params->hashLog = MAX(ZSTD_HASHLOG_MIN, windowLog - LDM_HASH_RLOG); assert(params->hashLog <= ZSTD_HASHLOG_MAX); } if (params->hashEveryLog == 0) { params->hashEveryLog = windowLog < params->hashLog ? 0 : windowLog - params->hashLog; } params->bucketSizeLog = MIN(params->bucketSizeLog, params->hashLog); } size_t ZSTD_ldm_getTableSize(ldmParams_t params) { size_t const ldmHSize = ((size_t)1) << params.hashLog; size_t const ldmBucketSizeLog = MIN(params.bucketSizeLog, params.hashLog); size_t const ldmBucketSize = ((size_t)1) << (params.hashLog - ldmBucketSizeLog); size_t const totalSize = ldmBucketSize + ldmHSize * sizeof(ldmEntry_t); return params.enableLdm ? totalSize : 0; } size_t ZSTD_ldm_getMaxNbSeq(ldmParams_t params, size_t maxChunkSize) { return params.enableLdm ? (maxChunkSize / params.minMatchLength) : 0; } /** ZSTD_ldm_getSmallHash() : * numBits should be <= 32 * If numBits==0, returns 0. * @return : the most significant numBits of value. */ static U32 ZSTD_ldm_getSmallHash(U64 value, U32 numBits) { assert(numBits <= 32); return numBits == 0 ? 0 : (U32)(value >> (64 - numBits)); } /** ZSTD_ldm_getChecksum() : * numBitsToDiscard should be <= 32 * @return : the next most significant 32 bits after numBitsToDiscard */ static U32 ZSTD_ldm_getChecksum(U64 hash, U32 numBitsToDiscard) { assert(numBitsToDiscard <= 32); return (hash >> (64 - 32 - numBitsToDiscard)) & 0xFFFFFFFF; } /** ZSTD_ldm_getTag() ; * Given the hash, returns the most significant numTagBits bits * after (32 + hbits) bits. * * If there are not enough bits remaining, return the last * numTagBits bits. */ static U32 ZSTD_ldm_getTag(U64 hash, U32 hbits, U32 numTagBits) { assert(numTagBits < 32 && hbits <= 32); if (32 - hbits < numTagBits) { return hash & (((U32)1 << numTagBits) - 1); } else { return (hash >> (32 - hbits - numTagBits)) & (((U32)1 << numTagBits) - 1); } } /** ZSTD_ldm_getBucket() : * Returns a pointer to the start of the bucket associated with hash. */ static ldmEntry_t* ZSTD_ldm_getBucket( ldmState_t* ldmState, size_t hash, ldmParams_t const ldmParams) { return ldmState->hashTable + (hash << ldmParams.bucketSizeLog); } /** ZSTD_ldm_insertEntry() : * Insert the entry with corresponding hash into the hash table */ static void ZSTD_ldm_insertEntry(ldmState_t* ldmState, size_t const hash, const ldmEntry_t entry, ldmParams_t const ldmParams) { BYTE* const bucketOffsets = ldmState->bucketOffsets; *(ZSTD_ldm_getBucket(ldmState, hash, ldmParams) + bucketOffsets[hash]) = entry; bucketOffsets[hash]++; bucketOffsets[hash] &= ((U32)1 << ldmParams.bucketSizeLog) - 1; } /** ZSTD_ldm_makeEntryAndInsertByTag() : * * Gets the small hash, checksum, and tag from the rollingHash. * * If the tag matches (1 << ldmParams.hashEveryLog)-1, then * creates an ldmEntry from the offset, and inserts it into the hash table. * * hBits is the length of the small hash, which is the most significant hBits * of rollingHash. The checksum is the next 32 most significant bits, followed * by ldmParams.hashEveryLog bits that make up the tag. */ static void ZSTD_ldm_makeEntryAndInsertByTag(ldmState_t* ldmState, U64 const rollingHash, U32 const hBits, U32 const offset, ldmParams_t const ldmParams) { U32 const tag = ZSTD_ldm_getTag(rollingHash, hBits, ldmParams.hashEveryLog); U32 const tagMask = ((U32)1 << ldmParams.hashEveryLog) - 1; if (tag == tagMask) { U32 const hash = ZSTD_ldm_getSmallHash(rollingHash, hBits); U32 const checksum = ZSTD_ldm_getChecksum(rollingHash, hBits); ldmEntry_t entry; entry.offset = offset; entry.checksum = checksum; ZSTD_ldm_insertEntry(ldmState, hash, entry, ldmParams); } } /** ZSTD_ldm_getRollingHash() : * Get a 64-bit hash using the first len bytes from buf. * * Giving bytes s = s_1, s_2, ... s_k, the hash is defined to be * H(s) = s_1*(a^(k-1)) + s_2*(a^(k-2)) + ... + s_k*(a^0) * * where the constant a is defined to be prime8bytes. * * The implementation adds an offset to each byte, so * H(s) = (s_1 + HASH_CHAR_OFFSET)*(a^(k-1)) + ... */ static U64 ZSTD_ldm_getRollingHash(const BYTE* buf, U32 len) { U64 ret = 0; U32 i; for (i = 0; i < len; i++) { ret *= prime8bytes; ret += buf[i] + LDM_HASH_CHAR_OFFSET; } return ret; } /** ZSTD_ldm_ipow() : * Return base^exp. */ static U64 ZSTD_ldm_ipow(U64 base, U64 exp) { U64 ret = 1; while (exp) { if (exp & 1) { ret *= base; } exp >>= 1; base *= base; } return ret; } U64 ZSTD_ldm_getHashPower(U32 minMatchLength) { DEBUGLOG(4, "ZSTD_ldm_getHashPower: mml=%u", minMatchLength); assert(minMatchLength >= ZSTD_LDM_MINMATCH_MIN); return ZSTD_ldm_ipow(prime8bytes, minMatchLength - 1); } /** ZSTD_ldm_updateHash() : * Updates hash by removing toRemove and adding toAdd. */ static U64 ZSTD_ldm_updateHash(U64 hash, BYTE toRemove, BYTE toAdd, U64 hashPower) { hash -= ((toRemove + LDM_HASH_CHAR_OFFSET) * hashPower); hash *= prime8bytes; hash += toAdd + LDM_HASH_CHAR_OFFSET; return hash; } /** ZSTD_ldm_countBackwardsMatch() : * Returns the number of bytes that match backwards before pIn and pMatch. * * We count only bytes where pMatch >= pBase and pIn >= pAnchor. */ static size_t ZSTD_ldm_countBackwardsMatch( const BYTE* pIn, const BYTE* pAnchor, const BYTE* pMatch, const BYTE* pBase) { size_t matchLength = 0; while (pIn > pAnchor && pMatch > pBase && pIn[-1] == pMatch[-1]) { pIn--; pMatch--; matchLength++; } return matchLength; } /** ZSTD_ldm_fillFastTables() : * * Fills the relevant tables for the ZSTD_fast and ZSTD_dfast strategies. * This is similar to ZSTD_loadDictionaryContent. * * The tables for the other strategies are filled within their * block compressors. */ static size_t ZSTD_ldm_fillFastTables(ZSTD_matchState_t* ms, ZSTD_compressionParameters const* cParams, void const* end) { const BYTE* const iend = (const BYTE*)end; switch(cParams->strategy) { case ZSTD_fast: ZSTD_fillHashTable(ms, cParams, iend, ZSTD_dtlm_fast); break; case ZSTD_dfast: ZSTD_fillDoubleHashTable(ms, cParams, iend, ZSTD_dtlm_fast); break; case ZSTD_greedy: case ZSTD_lazy: case ZSTD_lazy2: case ZSTD_btlazy2: case ZSTD_btopt: case ZSTD_btultra: break; default: assert(0); /* not possible : not a valid strategy id */ } return 0; } /** ZSTD_ldm_fillLdmHashTable() : * * Fills hashTable from (lastHashed + 1) to iend (non-inclusive). * lastHash is the rolling hash that corresponds to lastHashed. * * Returns the rolling hash corresponding to position iend-1. */ static U64 ZSTD_ldm_fillLdmHashTable(ldmState_t* state, U64 lastHash, const BYTE* lastHashed, const BYTE* iend, const BYTE* base, U32 hBits, ldmParams_t const ldmParams) { U64 rollingHash = lastHash; const BYTE* cur = lastHashed + 1; while (cur < iend) { rollingHash = ZSTD_ldm_updateHash(rollingHash, cur[-1], cur[ldmParams.minMatchLength-1], state->hashPower); ZSTD_ldm_makeEntryAndInsertByTag(state, rollingHash, hBits, (U32)(cur - base), ldmParams); ++cur; } return rollingHash; } /** ZSTD_ldm_limitTableUpdate() : * * Sets cctx->nextToUpdate to a position corresponding closer to anchor * if it is far way * (after a long match, only update tables a limited amount). */ static void ZSTD_ldm_limitTableUpdate(ZSTD_matchState_t* ms, const BYTE* anchor) { U32 const current = (U32)(anchor - ms->window.base); if (current > ms->nextToUpdate + 1024) { ms->nextToUpdate = current - MIN(512, current - ms->nextToUpdate - 1024); } } static size_t ZSTD_ldm_generateSequences_internal( ldmState_t* ldmState, rawSeqStore_t* rawSeqStore, ldmParams_t const* params, void const* src, size_t srcSize) { /* LDM parameters */ int const extDict = ZSTD_window_hasExtDict(ldmState->window); U32 const minMatchLength = params->minMatchLength; U64 const hashPower = ldmState->hashPower; U32 const hBits = params->hashLog - params->bucketSizeLog; U32 const ldmBucketSize = 1U << params->bucketSizeLog; U32 const hashEveryLog = params->hashEveryLog; U32 const ldmTagMask = (1U << params->hashEveryLog) - 1; /* Prefix and extDict parameters */ U32 const dictLimit = ldmState->window.dictLimit; U32 const lowestIndex = extDict ? ldmState->window.lowLimit : dictLimit; BYTE const* const base = ldmState->window.base; BYTE const* const dictBase = extDict ? ldmState->window.dictBase : NULL; BYTE const* const dictStart = extDict ? dictBase + lowestIndex : NULL; BYTE const* const dictEnd = extDict ? dictBase + dictLimit : NULL; BYTE const* const lowPrefixPtr = base + dictLimit; /* Input bounds */ BYTE const* const istart = (BYTE const*)src; BYTE const* const iend = istart + srcSize; BYTE const* const ilimit = iend - MAX(minMatchLength, HASH_READ_SIZE); /* Input positions */ BYTE const* anchor = istart; BYTE const* ip = istart; /* Rolling hash */ BYTE const* lastHashed = NULL; U64 rollingHash = 0; while (ip <= ilimit) { size_t mLength; U32 const current = (U32)(ip - base); size_t forwardMatchLength = 0, backwardMatchLength = 0; ldmEntry_t* bestEntry = NULL; if (ip != istart) { rollingHash = ZSTD_ldm_updateHash(rollingHash, lastHashed[0], lastHashed[minMatchLength], hashPower); } else { rollingHash = ZSTD_ldm_getRollingHash(ip, minMatchLength); } lastHashed = ip; /* Do not insert and do not look for a match */ if (ZSTD_ldm_getTag(rollingHash, hBits, hashEveryLog) != ldmTagMask) { ip++; continue; } /* Get the best entry and compute the match lengths */ { ldmEntry_t* const bucket = ZSTD_ldm_getBucket(ldmState, ZSTD_ldm_getSmallHash(rollingHash, hBits), *params); ldmEntry_t* cur; size_t bestMatchLength = 0; U32 const checksum = ZSTD_ldm_getChecksum(rollingHash, hBits); for (cur = bucket; cur < bucket + ldmBucketSize; ++cur) { size_t curForwardMatchLength, curBackwardMatchLength, curTotalMatchLength; if (cur->checksum != checksum || cur->offset <= lowestIndex) { continue; } if (extDict) { BYTE const* const curMatchBase = cur->offset < dictLimit ? dictBase : base; BYTE const* const pMatch = curMatchBase + cur->offset; BYTE const* const matchEnd = cur->offset < dictLimit ? dictEnd : iend; BYTE const* const lowMatchPtr = cur->offset < dictLimit ? dictStart : lowPrefixPtr; curForwardMatchLength = ZSTD_count_2segments( ip, pMatch, iend, matchEnd, lowPrefixPtr); if (curForwardMatchLength < minMatchLength) { continue; } curBackwardMatchLength = ZSTD_ldm_countBackwardsMatch(ip, anchor, pMatch, lowMatchPtr); curTotalMatchLength = curForwardMatchLength + curBackwardMatchLength; } else { /* !extDict */ BYTE const* const pMatch = base + cur->offset; curForwardMatchLength = ZSTD_count(ip, pMatch, iend); if (curForwardMatchLength < minMatchLength) { continue; } curBackwardMatchLength = ZSTD_ldm_countBackwardsMatch(ip, anchor, pMatch, lowPrefixPtr); curTotalMatchLength = curForwardMatchLength + curBackwardMatchLength; } if (curTotalMatchLength > bestMatchLength) { bestMatchLength = curTotalMatchLength; forwardMatchLength = curForwardMatchLength; backwardMatchLength = curBackwardMatchLength; bestEntry = cur; } } } /* No match found -- continue searching */ if (bestEntry == NULL) { ZSTD_ldm_makeEntryAndInsertByTag(ldmState, rollingHash, hBits, current, *params); ip++; continue; } /* Match found */ mLength = forwardMatchLength + backwardMatchLength; ip -= backwardMatchLength; { /* Store the sequence: * ip = current - backwardMatchLength * The match is at (bestEntry->offset - backwardMatchLength) */ U32 const matchIndex = bestEntry->offset; U32 const offset = current - matchIndex; rawSeq* const seq = rawSeqStore->seq + rawSeqStore->size; /* Out of sequence storage */ if (rawSeqStore->size == rawSeqStore->capacity) return ERROR(dstSize_tooSmall); seq->litLength = (U32)(ip - anchor); seq->matchLength = (U32)mLength; seq->offset = offset; rawSeqStore->size++; } /* Insert the current entry into the hash table */ ZSTD_ldm_makeEntryAndInsertByTag(ldmState, rollingHash, hBits, (U32)(lastHashed - base), *params); assert(ip + backwardMatchLength == lastHashed); /* Fill the hash table from lastHashed+1 to ip+mLength*/ /* Heuristic: don't need to fill the entire table at end of block */ if (ip + mLength <= ilimit) { rollingHash = ZSTD_ldm_fillLdmHashTable( ldmState, rollingHash, lastHashed, ip + mLength, base, hBits, *params); lastHashed = ip + mLength - 1; } ip += mLength; anchor = ip; } return iend - anchor; } /*! ZSTD_ldm_reduceTable() : * reduce table indexes by `reducerValue` */ static void ZSTD_ldm_reduceTable(ldmEntry_t* const table, U32 const size, U32 const reducerValue) { U32 u; for (u = 0; u < size; u++) { if (table[u].offset < reducerValue) table[u].offset = 0; else table[u].offset -= reducerValue; } } size_t ZSTD_ldm_generateSequences( ldmState_t* ldmState, rawSeqStore_t* sequences, ldmParams_t const* params, void const* src, size_t srcSize) { U32 const maxDist = 1U << params->windowLog; BYTE const* const istart = (BYTE const*)src; BYTE const* const iend = istart + srcSize; size_t const kMaxChunkSize = 1 << 20; size_t const nbChunks = (srcSize / kMaxChunkSize) + ((srcSize % kMaxChunkSize) != 0); size_t chunk; size_t leftoverSize = 0; assert(ZSTD_CHUNKSIZE_MAX >= kMaxChunkSize); /* Check that ZSTD_window_update() has been called for this chunk prior * to passing it to this function. */ assert(ldmState->window.nextSrc >= (BYTE const*)src + srcSize); /* The input could be very large (in zstdmt), so it must be broken up into * chunks to enforce the maximmum distance and handle overflow correction. */ assert(sequences->pos <= sequences->size); assert(sequences->size <= sequences->capacity); for (chunk = 0; chunk < nbChunks && sequences->size < sequences->capacity; ++chunk) { BYTE const* const chunkStart = istart + chunk * kMaxChunkSize; size_t const remaining = (size_t)(iend - chunkStart); BYTE const *const chunkEnd = (remaining < kMaxChunkSize) ? iend : chunkStart + kMaxChunkSize; size_t const chunkSize = chunkEnd - chunkStart; size_t newLeftoverSize; size_t const prevSize = sequences->size; assert(chunkStart < iend); /* 1. Perform overflow correction if necessary. */ if (ZSTD_window_needOverflowCorrection(ldmState->window, chunkEnd)) { U32 const ldmHSize = 1U << params->hashLog; U32 const correction = ZSTD_window_correctOverflow( &ldmState->window, /* cycleLog */ 0, maxDist, src); ZSTD_ldm_reduceTable(ldmState->hashTable, ldmHSize, correction); } /* 2. We enforce the maximum offset allowed. * * kMaxChunkSize should be small enough that we don't lose too much of * the window through early invalidation. * TODO: * Test the chunk size. * * Try invalidation after the sequence generation and test the * the offset against maxDist directly. */ ZSTD_window_enforceMaxDist(&ldmState->window, chunkEnd, maxDist, NULL); /* 3. Generate the sequences for the chunk, and get newLeftoverSize. */ newLeftoverSize = ZSTD_ldm_generateSequences_internal( ldmState, sequences, params, chunkStart, chunkSize); if (ZSTD_isError(newLeftoverSize)) return newLeftoverSize; /* 4. We add the leftover literals from previous iterations to the first * newly generated sequence, or add the `newLeftoverSize` if none are * generated. */ /* Prepend the leftover literals from the last call */ if (prevSize < sequences->size) { sequences->seq[prevSize].litLength += (U32)leftoverSize; leftoverSize = newLeftoverSize; } else { assert(newLeftoverSize == chunkSize); leftoverSize += chunkSize; } } return 0; } void ZSTD_ldm_skipSequences(rawSeqStore_t* rawSeqStore, size_t srcSize, U32 const minMatch) { while (srcSize > 0 && rawSeqStore->pos < rawSeqStore->size) { rawSeq* seq = rawSeqStore->seq + rawSeqStore->pos; if (srcSize <= seq->litLength) { /* Skip past srcSize literals */ seq->litLength -= (U32)srcSize; return; } srcSize -= seq->litLength; seq->litLength = 0; if (srcSize < seq->matchLength) { /* Skip past the first srcSize of the match */ seq->matchLength -= (U32)srcSize; if (seq->matchLength < minMatch) { /* The match is too short, omit it */ if (rawSeqStore->pos + 1 < rawSeqStore->size) { seq[1].litLength += seq[0].matchLength; } rawSeqStore->pos++; } return; } srcSize -= seq->matchLength; seq->matchLength = 0; rawSeqStore->pos++; } } /** * If the sequence length is longer than remaining then the sequence is split * between this block and the next. * * Returns the current sequence to handle, or if the rest of the block should * be literals, it returns a sequence with offset == 0. */ static rawSeq maybeSplitSequence(rawSeqStore_t* rawSeqStore, U32 const remaining, U32 const minMatch) { rawSeq sequence = rawSeqStore->seq[rawSeqStore->pos]; assert(sequence.offset > 0); /* Likely: No partial sequence */ if (remaining >= sequence.litLength + sequence.matchLength) { rawSeqStore->pos++; return sequence; } /* Cut the sequence short (offset == 0 ==> rest is literals). */ if (remaining <= sequence.litLength) { sequence.offset = 0; } else if (remaining < sequence.litLength + sequence.matchLength) { sequence.matchLength = remaining - sequence.litLength; if (sequence.matchLength < minMatch) { sequence.offset = 0; } } /* Skip past `remaining` bytes for the future sequences. */ ZSTD_ldm_skipSequences(rawSeqStore, remaining, minMatch); return sequence; } size_t ZSTD_ldm_blockCompress(rawSeqStore_t* rawSeqStore, ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM], ZSTD_compressionParameters const* cParams, void const* src, size_t srcSize, int const extDict) { unsigned const minMatch = cParams->searchLength; ZSTD_blockCompressor const blockCompressor = ZSTD_selectBlockCompressor(cParams->strategy, extDict); /* Input bounds */ BYTE const* const istart = (BYTE const*)src; BYTE const* const iend = istart + srcSize; /* Input positions */ BYTE const* ip = istart; DEBUGLOG(5, "ZSTD_ldm_blockCompress: srcSize=%zu", srcSize); assert(rawSeqStore->pos <= rawSeqStore->size); assert(rawSeqStore->size <= rawSeqStore->capacity); /* Loop through each sequence and apply the block compressor to the lits */ while (rawSeqStore->pos < rawSeqStore->size && ip < iend) { /* maybeSplitSequence updates rawSeqStore->pos */ rawSeq const sequence = maybeSplitSequence(rawSeqStore, (U32)(iend - ip), minMatch); int i; /* End signal */ if (sequence.offset == 0) break; assert(sequence.offset <= (1U << cParams->windowLog)); assert(ip + sequence.litLength + sequence.matchLength <= iend); /* Fill tables for block compressor */ ZSTD_ldm_limitTableUpdate(ms, ip); ZSTD_ldm_fillFastTables(ms, cParams, ip); /* Run the block compressor */ DEBUGLOG(5, "calling block compressor on segment of size %u", sequence.litLength); { size_t const newLitLength = blockCompressor(ms, seqStore, rep, cParams, ip, sequence.litLength); ip += sequence.litLength; /* Update the repcodes */ for (i = ZSTD_REP_NUM - 1; i > 0; i--) rep[i] = rep[i-1]; rep[0] = sequence.offset; /* Store the sequence */ ZSTD_storeSeq(seqStore, newLitLength, ip - newLitLength, sequence.offset + ZSTD_REP_MOVE, sequence.matchLength - MINMATCH); ip += sequence.matchLength; } } /* Fill the tables for the block compressor */ ZSTD_ldm_limitTableUpdate(ms, ip); ZSTD_ldm_fillFastTables(ms, cParams, ip); /* Compress the last literals */ return blockCompressor(ms, seqStore, rep, cParams, ip, iend - ip); }