597 lines
23 KiB
C
597 lines
23 KiB
C
/*
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* Copyright (c) 2016-present, Yann Collet, Facebook, Inc.
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* All rights reserved.
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*
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* This source code is licensed under both the BSD-style license (found in the
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* LICENSE file in the root directory of this source tree) and the GPLv2 (found
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* in the COPYING file in the root directory of this source tree).
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*/
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#include "zstd_ldm.h"
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#include "debug.h"
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#include "zstd_fast.h" /* ZSTD_fillHashTable() */
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#include "zstd_double_fast.h" /* ZSTD_fillDoubleHashTable() */
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#define LDM_BUCKET_SIZE_LOG 3
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#define LDM_MIN_MATCH_LENGTH 64
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#define LDM_HASH_RLOG 7
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#define LDM_HASH_CHAR_OFFSET 10
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void ZSTD_ldm_adjustParameters(ldmParams_t* params,
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ZSTD_compressionParameters const* cParams)
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{
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params->windowLog = cParams->windowLog;
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ZSTD_STATIC_ASSERT(LDM_BUCKET_SIZE_LOG <= ZSTD_LDM_BUCKETSIZELOG_MAX);
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DEBUGLOG(4, "ZSTD_ldm_adjustParameters");
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if (!params->bucketSizeLog) params->bucketSizeLog = LDM_BUCKET_SIZE_LOG;
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if (!params->minMatchLength) params->minMatchLength = LDM_MIN_MATCH_LENGTH;
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if (cParams->strategy >= ZSTD_btopt) {
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/* Get out of the way of the optimal parser */
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U32 const minMatch = MAX(cParams->targetLength, params->minMatchLength);
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assert(minMatch >= ZSTD_LDM_MINMATCH_MIN);
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assert(minMatch <= ZSTD_LDM_MINMATCH_MAX);
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params->minMatchLength = minMatch;
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}
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if (params->hashLog == 0) {
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params->hashLog = MAX(ZSTD_HASHLOG_MIN, params->windowLog - LDM_HASH_RLOG);
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assert(params->hashLog <= ZSTD_HASHLOG_MAX);
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}
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if (params->hashRateLog == 0) {
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params->hashRateLog = params->windowLog < params->hashLog
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? 0
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: params->windowLog - params->hashLog;
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}
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params->bucketSizeLog = MIN(params->bucketSizeLog, params->hashLog);
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}
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size_t ZSTD_ldm_getTableSize(ldmParams_t params)
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{
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size_t const ldmHSize = ((size_t)1) << params.hashLog;
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size_t const ldmBucketSizeLog = MIN(params.bucketSizeLog, params.hashLog);
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size_t const ldmBucketSize =
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((size_t)1) << (params.hashLog - ldmBucketSizeLog);
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size_t const totalSize = ldmBucketSize + ldmHSize * sizeof(ldmEntry_t);
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return params.enableLdm ? totalSize : 0;
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}
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size_t ZSTD_ldm_getMaxNbSeq(ldmParams_t params, size_t maxChunkSize)
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{
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return params.enableLdm ? (maxChunkSize / params.minMatchLength) : 0;
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}
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/** ZSTD_ldm_getSmallHash() :
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* numBits should be <= 32
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* If numBits==0, returns 0.
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* @return : the most significant numBits of value. */
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static U32 ZSTD_ldm_getSmallHash(U64 value, U32 numBits)
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{
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assert(numBits <= 32);
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return numBits == 0 ? 0 : (U32)(value >> (64 - numBits));
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}
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/** ZSTD_ldm_getChecksum() :
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* numBitsToDiscard should be <= 32
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* @return : the next most significant 32 bits after numBitsToDiscard */
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static U32 ZSTD_ldm_getChecksum(U64 hash, U32 numBitsToDiscard)
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{
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assert(numBitsToDiscard <= 32);
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return (hash >> (64 - 32 - numBitsToDiscard)) & 0xFFFFFFFF;
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}
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/** ZSTD_ldm_getTag() ;
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* Given the hash, returns the most significant numTagBits bits
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* after (32 + hbits) bits.
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*
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* If there are not enough bits remaining, return the last
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* numTagBits bits. */
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static U32 ZSTD_ldm_getTag(U64 hash, U32 hbits, U32 numTagBits)
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{
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assert(numTagBits < 32 && hbits <= 32);
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if (32 - hbits < numTagBits) {
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return hash & (((U32)1 << numTagBits) - 1);
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} else {
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return (hash >> (32 - hbits - numTagBits)) & (((U32)1 << numTagBits) - 1);
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}
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}
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/** ZSTD_ldm_getBucket() :
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* Returns a pointer to the start of the bucket associated with hash. */
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static ldmEntry_t* ZSTD_ldm_getBucket(
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ldmState_t* ldmState, size_t hash, ldmParams_t const ldmParams)
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{
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return ldmState->hashTable + (hash << ldmParams.bucketSizeLog);
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}
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/** ZSTD_ldm_insertEntry() :
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* Insert the entry with corresponding hash into the hash table */
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static void ZSTD_ldm_insertEntry(ldmState_t* ldmState,
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size_t const hash, const ldmEntry_t entry,
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ldmParams_t const ldmParams)
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{
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BYTE* const bucketOffsets = ldmState->bucketOffsets;
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*(ZSTD_ldm_getBucket(ldmState, hash, ldmParams) + bucketOffsets[hash]) = entry;
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bucketOffsets[hash]++;
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bucketOffsets[hash] &= ((U32)1 << ldmParams.bucketSizeLog) - 1;
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}
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/** ZSTD_ldm_makeEntryAndInsertByTag() :
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*
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* Gets the small hash, checksum, and tag from the rollingHash.
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*
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* If the tag matches (1 << ldmParams.hashRateLog)-1, then
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* creates an ldmEntry from the offset, and inserts it into the hash table.
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*
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* hBits is the length of the small hash, which is the most significant hBits
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* of rollingHash. The checksum is the next 32 most significant bits, followed
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* by ldmParams.hashRateLog bits that make up the tag. */
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static void ZSTD_ldm_makeEntryAndInsertByTag(ldmState_t* ldmState,
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U64 const rollingHash,
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U32 const hBits,
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U32 const offset,
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ldmParams_t const ldmParams)
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{
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U32 const tag = ZSTD_ldm_getTag(rollingHash, hBits, ldmParams.hashRateLog);
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U32 const tagMask = ((U32)1 << ldmParams.hashRateLog) - 1;
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if (tag == tagMask) {
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U32 const hash = ZSTD_ldm_getSmallHash(rollingHash, hBits);
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U32 const checksum = ZSTD_ldm_getChecksum(rollingHash, hBits);
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ldmEntry_t entry;
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entry.offset = offset;
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entry.checksum = checksum;
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ZSTD_ldm_insertEntry(ldmState, hash, entry, ldmParams);
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}
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}
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/** ZSTD_ldm_countBackwardsMatch() :
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* Returns the number of bytes that match backwards before pIn and pMatch.
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*
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* We count only bytes where pMatch >= pBase and pIn >= pAnchor. */
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static size_t ZSTD_ldm_countBackwardsMatch(
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const BYTE* pIn, const BYTE* pAnchor,
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const BYTE* pMatch, const BYTE* pBase)
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{
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size_t matchLength = 0;
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while (pIn > pAnchor && pMatch > pBase && pIn[-1] == pMatch[-1]) {
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pIn--;
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pMatch--;
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matchLength++;
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}
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return matchLength;
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}
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/** ZSTD_ldm_fillFastTables() :
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*
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* Fills the relevant tables for the ZSTD_fast and ZSTD_dfast strategies.
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* This is similar to ZSTD_loadDictionaryContent.
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*
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* The tables for the other strategies are filled within their
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* block compressors. */
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static size_t ZSTD_ldm_fillFastTables(ZSTD_matchState_t* ms,
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void const* end)
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{
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const BYTE* const iend = (const BYTE*)end;
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switch(ms->cParams.strategy)
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{
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case ZSTD_fast:
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ZSTD_fillHashTable(ms, iend, ZSTD_dtlm_fast);
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break;
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case ZSTD_dfast:
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ZSTD_fillDoubleHashTable(ms, iend, ZSTD_dtlm_fast);
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break;
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case ZSTD_greedy:
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case ZSTD_lazy:
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case ZSTD_lazy2:
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case ZSTD_btlazy2:
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case ZSTD_btopt:
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case ZSTD_btultra:
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case ZSTD_btultra2:
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break;
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default:
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assert(0); /* not possible : not a valid strategy id */
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}
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return 0;
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}
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/** ZSTD_ldm_fillLdmHashTable() :
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*
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* Fills hashTable from (lastHashed + 1) to iend (non-inclusive).
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* lastHash is the rolling hash that corresponds to lastHashed.
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*
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* Returns the rolling hash corresponding to position iend-1. */
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static U64 ZSTD_ldm_fillLdmHashTable(ldmState_t* state,
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U64 lastHash, const BYTE* lastHashed,
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const BYTE* iend, const BYTE* base,
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U32 hBits, ldmParams_t const ldmParams)
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{
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U64 rollingHash = lastHash;
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const BYTE* cur = lastHashed + 1;
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while (cur < iend) {
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rollingHash = ZSTD_rollingHash_rotate(rollingHash, cur[-1],
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cur[ldmParams.minMatchLength-1],
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state->hashPower);
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ZSTD_ldm_makeEntryAndInsertByTag(state,
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rollingHash, hBits,
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(U32)(cur - base), ldmParams);
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++cur;
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}
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return rollingHash;
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}
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/** ZSTD_ldm_limitTableUpdate() :
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*
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* Sets cctx->nextToUpdate to a position corresponding closer to anchor
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* if it is far way
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* (after a long match, only update tables a limited amount). */
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static void ZSTD_ldm_limitTableUpdate(ZSTD_matchState_t* ms, const BYTE* anchor)
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{
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U32 const current = (U32)(anchor - ms->window.base);
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if (current > ms->nextToUpdate + 1024) {
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ms->nextToUpdate =
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current - MIN(512, current - ms->nextToUpdate - 1024);
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}
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}
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static size_t ZSTD_ldm_generateSequences_internal(
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ldmState_t* ldmState, rawSeqStore_t* rawSeqStore,
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ldmParams_t const* params, void const* src, size_t srcSize)
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{
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/* LDM parameters */
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int const extDict = ZSTD_window_hasExtDict(ldmState->window);
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U32 const minMatchLength = params->minMatchLength;
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U64 const hashPower = ldmState->hashPower;
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U32 const hBits = params->hashLog - params->bucketSizeLog;
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U32 const ldmBucketSize = 1U << params->bucketSizeLog;
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U32 const hashRateLog = params->hashRateLog;
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U32 const ldmTagMask = (1U << params->hashRateLog) - 1;
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/* Prefix and extDict parameters */
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U32 const dictLimit = ldmState->window.dictLimit;
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U32 const lowestIndex = extDict ? ldmState->window.lowLimit : dictLimit;
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BYTE const* const base = ldmState->window.base;
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BYTE const* const dictBase = extDict ? ldmState->window.dictBase : NULL;
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BYTE const* const dictStart = extDict ? dictBase + lowestIndex : NULL;
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BYTE const* const dictEnd = extDict ? dictBase + dictLimit : NULL;
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BYTE const* const lowPrefixPtr = base + dictLimit;
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/* Input bounds */
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BYTE const* const istart = (BYTE const*)src;
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BYTE const* const iend = istart + srcSize;
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BYTE const* const ilimit = iend - MAX(minMatchLength, HASH_READ_SIZE);
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/* Input positions */
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BYTE const* anchor = istart;
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BYTE const* ip = istart;
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/* Rolling hash */
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BYTE const* lastHashed = NULL;
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U64 rollingHash = 0;
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while (ip <= ilimit) {
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size_t mLength;
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U32 const current = (U32)(ip - base);
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size_t forwardMatchLength = 0, backwardMatchLength = 0;
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ldmEntry_t* bestEntry = NULL;
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if (ip != istart) {
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rollingHash = ZSTD_rollingHash_rotate(rollingHash, lastHashed[0],
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lastHashed[minMatchLength],
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hashPower);
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} else {
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rollingHash = ZSTD_rollingHash_compute(ip, minMatchLength);
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}
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lastHashed = ip;
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/* Do not insert and do not look for a match */
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if (ZSTD_ldm_getTag(rollingHash, hBits, hashRateLog) != ldmTagMask) {
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ip++;
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continue;
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}
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/* Get the best entry and compute the match lengths */
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{
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ldmEntry_t* const bucket =
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ZSTD_ldm_getBucket(ldmState,
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ZSTD_ldm_getSmallHash(rollingHash, hBits),
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*params);
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ldmEntry_t* cur;
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size_t bestMatchLength = 0;
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U32 const checksum = ZSTD_ldm_getChecksum(rollingHash, hBits);
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for (cur = bucket; cur < bucket + ldmBucketSize; ++cur) {
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size_t curForwardMatchLength, curBackwardMatchLength,
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curTotalMatchLength;
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if (cur->checksum != checksum || cur->offset <= lowestIndex) {
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continue;
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}
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if (extDict) {
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BYTE const* const curMatchBase =
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cur->offset < dictLimit ? dictBase : base;
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BYTE const* const pMatch = curMatchBase + cur->offset;
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BYTE const* const matchEnd =
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cur->offset < dictLimit ? dictEnd : iend;
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BYTE const* const lowMatchPtr =
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cur->offset < dictLimit ? dictStart : lowPrefixPtr;
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curForwardMatchLength = ZSTD_count_2segments(
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ip, pMatch, iend,
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matchEnd, lowPrefixPtr);
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if (curForwardMatchLength < minMatchLength) {
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continue;
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}
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curBackwardMatchLength =
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ZSTD_ldm_countBackwardsMatch(ip, anchor, pMatch,
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lowMatchPtr);
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curTotalMatchLength = curForwardMatchLength +
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curBackwardMatchLength;
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} else { /* !extDict */
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BYTE const* const pMatch = base + cur->offset;
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curForwardMatchLength = ZSTD_count(ip, pMatch, iend);
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if (curForwardMatchLength < minMatchLength) {
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continue;
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}
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curBackwardMatchLength =
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ZSTD_ldm_countBackwardsMatch(ip, anchor, pMatch,
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lowPrefixPtr);
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curTotalMatchLength = curForwardMatchLength +
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curBackwardMatchLength;
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}
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if (curTotalMatchLength > bestMatchLength) {
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bestMatchLength = curTotalMatchLength;
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forwardMatchLength = curForwardMatchLength;
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backwardMatchLength = curBackwardMatchLength;
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bestEntry = cur;
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}
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}
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}
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/* No match found -- continue searching */
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if (bestEntry == NULL) {
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ZSTD_ldm_makeEntryAndInsertByTag(ldmState, rollingHash,
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hBits, current,
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*params);
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ip++;
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continue;
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}
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/* Match found */
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mLength = forwardMatchLength + backwardMatchLength;
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ip -= backwardMatchLength;
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{
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/* Store the sequence:
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* ip = current - backwardMatchLength
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* The match is at (bestEntry->offset - backwardMatchLength)
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*/
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U32 const matchIndex = bestEntry->offset;
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U32 const offset = current - matchIndex;
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rawSeq* const seq = rawSeqStore->seq + rawSeqStore->size;
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/* Out of sequence storage */
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if (rawSeqStore->size == rawSeqStore->capacity)
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return ERROR(dstSize_tooSmall);
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seq->litLength = (U32)(ip - anchor);
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seq->matchLength = (U32)mLength;
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seq->offset = offset;
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rawSeqStore->size++;
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}
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/* Insert the current entry into the hash table */
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ZSTD_ldm_makeEntryAndInsertByTag(ldmState, rollingHash, hBits,
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(U32)(lastHashed - base),
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*params);
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assert(ip + backwardMatchLength == lastHashed);
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/* Fill the hash table from lastHashed+1 to ip+mLength*/
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/* Heuristic: don't need to fill the entire table at end of block */
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if (ip + mLength <= ilimit) {
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rollingHash = ZSTD_ldm_fillLdmHashTable(
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ldmState, rollingHash, lastHashed,
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ip + mLength, base, hBits, *params);
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lastHashed = ip + mLength - 1;
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}
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ip += mLength;
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anchor = ip;
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}
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return iend - anchor;
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}
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/*! ZSTD_ldm_reduceTable() :
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* reduce table indexes by `reducerValue` */
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static void ZSTD_ldm_reduceTable(ldmEntry_t* const table, U32 const size,
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U32 const reducerValue)
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{
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U32 u;
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for (u = 0; u < size; u++) {
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if (table[u].offset < reducerValue) table[u].offset = 0;
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else table[u].offset -= reducerValue;
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}
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}
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size_t ZSTD_ldm_generateSequences(
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ldmState_t* ldmState, rawSeqStore_t* sequences,
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ldmParams_t const* params, void const* src, size_t srcSize)
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{
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U32 const maxDist = 1U << params->windowLog;
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BYTE const* const istart = (BYTE const*)src;
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BYTE const* const iend = istart + srcSize;
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size_t const kMaxChunkSize = 1 << 20;
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size_t const nbChunks = (srcSize / kMaxChunkSize) + ((srcSize % kMaxChunkSize) != 0);
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size_t chunk;
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size_t leftoverSize = 0;
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assert(ZSTD_CHUNKSIZE_MAX >= kMaxChunkSize);
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/* Check that ZSTD_window_update() has been called for this chunk prior
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* to passing it to this function.
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*/
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assert(ldmState->window.nextSrc >= (BYTE const*)src + srcSize);
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/* The input could be very large (in zstdmt), so it must be broken up into
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* chunks to enforce the maximum distance and handle overflow correction.
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*/
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assert(sequences->pos <= sequences->size);
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assert(sequences->size <= sequences->capacity);
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for (chunk = 0; chunk < nbChunks && sequences->size < sequences->capacity; ++chunk) {
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BYTE const* const chunkStart = istart + chunk * kMaxChunkSize;
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size_t const remaining = (size_t)(iend - chunkStart);
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BYTE const *const chunkEnd =
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(remaining < kMaxChunkSize) ? iend : chunkStart + kMaxChunkSize;
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size_t const chunkSize = chunkEnd - chunkStart;
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size_t newLeftoverSize;
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size_t const prevSize = sequences->size;
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assert(chunkStart < iend);
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/* 1. Perform overflow correction if necessary. */
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if (ZSTD_window_needOverflowCorrection(ldmState->window, chunkEnd)) {
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U32 const ldmHSize = 1U << params->hashLog;
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U32 const correction = ZSTD_window_correctOverflow(
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&ldmState->window, /* cycleLog */ 0, maxDist, chunkStart);
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ZSTD_ldm_reduceTable(ldmState->hashTable, ldmHSize, correction);
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}
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/* 2. We enforce the maximum offset allowed.
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*
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* kMaxChunkSize should be small enough that we don't lose too much of
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* the window through early invalidation.
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* TODO: * Test the chunk size.
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* * Try invalidation after the sequence generation and test the
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* the offset against maxDist directly.
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*/
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ZSTD_window_enforceMaxDist(&ldmState->window, chunkEnd, maxDist, NULL, NULL);
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/* 3. Generate the sequences for the chunk, and get newLeftoverSize. */
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newLeftoverSize = ZSTD_ldm_generateSequences_internal(
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ldmState, sequences, params, chunkStart, chunkSize);
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|
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],
|
|
void const* src, size_t srcSize)
|
|
{
|
|
const ZSTD_compressionParameters* const cParams = &ms->cParams;
|
|
unsigned const minMatch = cParams->minMatch;
|
|
ZSTD_blockCompressor const blockCompressor =
|
|
ZSTD_selectBlockCompressor(cParams->strategy, ZSTD_matchState_dictMode(ms));
|
|
/* 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, 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, 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, ip);
|
|
/* Compress the last literals */
|
|
return blockCompressor(ms, seqStore, rep, ip, iend - ip);
|
|
}
|