mirror of
https://github.com/facebook/zstd.git
synced 2025-11-04 00:02:59 -05:00
620 lines
23 KiB
C
620 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 "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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size_t ZSTD_ldm_initializeParameters(ldmParams_t* params, U32 enableLdm)
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{
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ZSTD_STATIC_ASSERT(LDM_BUCKET_SIZE_LOG <= ZSTD_LDM_BUCKETSIZELOG_MAX);
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params->enableLdm = enableLdm>0;
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params->hashLog = 0;
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params->bucketSizeLog = LDM_BUCKET_SIZE_LOG;
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params->minMatchLength = LDM_MIN_MATCH_LENGTH;
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params->hashEveryLog = ZSTD_LDM_HASHEVERYLOG_NOTSET;
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return 0;
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}
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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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U32 const windowLog = cParams->windowLog;
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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, windowLog - LDM_HASH_RLOG);
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assert(params->hashLog <= ZSTD_HASHLOG_MAX);
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}
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if (params->hashEveryLog == ZSTD_LDM_HASHEVERYLOG_NOTSET) {
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params->hashEveryLog =
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windowLog < params->hashLog ? 0 : 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.hashEveryLog)-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.hashEveryLog 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.hashEveryLog);
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U32 const tagMask = ((U32)1 << ldmParams.hashEveryLog) - 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_getRollingHash() :
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* Get a 64-bit hash using the first len bytes from buf.
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*
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* Giving bytes s = s_1, s_2, ... s_k, the hash is defined to be
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* H(s) = s_1*(a^(k-1)) + s_2*(a^(k-2)) + ... + s_k*(a^0)
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*
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* where the constant a is defined to be prime8bytes.
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*
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* The implementation adds an offset to each byte, so
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* H(s) = (s_1 + HASH_CHAR_OFFSET)*(a^(k-1)) + ... */
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static U64 ZSTD_ldm_getRollingHash(const BYTE* buf, U32 len)
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{
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U64 ret = 0;
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U32 i;
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for (i = 0; i < len; i++) {
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ret *= prime8bytes;
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ret += buf[i] + LDM_HASH_CHAR_OFFSET;
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}
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return ret;
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}
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/** ZSTD_ldm_ipow() :
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* Return base^exp. */
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static U64 ZSTD_ldm_ipow(U64 base, U64 exp)
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{
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U64 ret = 1;
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while (exp) {
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if (exp & 1) { ret *= base; }
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exp >>= 1;
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base *= base;
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}
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return ret;
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}
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U64 ZSTD_ldm_getHashPower(U32 minMatchLength) {
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assert(minMatchLength >= ZSTD_LDM_MINMATCH_MIN);
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return ZSTD_ldm_ipow(prime8bytes, minMatchLength - 1);
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}
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/** ZSTD_ldm_updateHash() :
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* Updates hash by removing toRemove and adding toAdd. */
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static U64 ZSTD_ldm_updateHash(U64 hash, BYTE toRemove, BYTE toAdd, U64 hashPower)
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{
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hash -= ((toRemove + LDM_HASH_CHAR_OFFSET) * hashPower);
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hash *= prime8bytes;
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hash += toAdd + LDM_HASH_CHAR_OFFSET;
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return hash;
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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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ZSTD_compressionParameters const* cParams,
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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(cParams->strategy)
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{
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case ZSTD_fast:
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ZSTD_fillHashTable(ms, cParams, iend);
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ms->nextToUpdate = (U32)(iend - ms->window.base);
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break;
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case ZSTD_dfast:
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ZSTD_fillDoubleHashTable(ms, cParams, iend);
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ms->nextToUpdate = (U32)(iend - ms->window.base);
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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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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_ldm_updateHash(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, rawSeq* sequences,
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ldmParams_t const* params, void const* src, size_t srcSize,
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int const extDict)
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{
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rawSeq const* const sequencesStart = sequences;
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/* LDM parameters */
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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 hashEveryLog = params->hashEveryLog;
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U32 const ldmTagMask = (1U << params->hashEveryLog) - 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_ldm_updateHash(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_ldm_getRollingHash(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, hashEveryLog) != 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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sequences->litLength = (U32)(ip - anchor);
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sequences->matchLength = (U32)mLength;
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sequences->offset = offset;
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++sequences;
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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 the number of sequences generated */
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return sequences - sequencesStart;
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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, rawSeq* sequences,
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ldmParams_t const* params, void const* src, size_t srcSize,
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int const extDict)
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{
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U32 const maxDist = 1U << params->windowLog;
|
|
BYTE const* const istart = (BYTE const*)src;
|
|
size_t const kMaxChunkSize = 1 << 20;
|
|
size_t const nbChunks = (srcSize / kMaxChunkSize) + ((srcSize % kMaxChunkSize) != 0);
|
|
size_t nbSeq = 0;
|
|
size_t chunk;
|
|
|
|
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);
|
|
for (chunk = 0; chunk < nbChunks; ++chunk) {
|
|
size_t const chunkStart = chunk * kMaxChunkSize;
|
|
size_t const chunkEnd = MIN(chunkStart + kMaxChunkSize, srcSize);
|
|
size_t const chunkSize = chunkEnd - chunkStart;
|
|
|
|
assert(chunkStart < srcSize);
|
|
if (ZSTD_window_needOverflowCorrection(ldmState->window)) {
|
|
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);
|
|
}
|
|
/* 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, istart + chunkEnd,
|
|
maxDist);
|
|
nbSeq += ZSTD_ldm_generateSequences_internal(
|
|
ldmState, sequences + nbSeq, params, istart + chunkStart, chunkSize,
|
|
extDict);
|
|
}
|
|
return nbSeq;
|
|
}
|
|
|
|
#if 0
|
|
/**
|
|
* 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(rawSeq* sequences, size_t* nbSeq,
|
|
size_t const seq, size_t const remaining,
|
|
U32 const minMatch)
|
|
{
|
|
rawSeq sequence = sequences[seq];
|
|
assert(sequence.offset > 0);
|
|
/* Handle partial sequences */
|
|
if (remaining <= sequence.litLength) {
|
|
/* Split the literals that we have out of the sequence.
|
|
* They will become the last literals of this block.
|
|
* The next block starts off with the remaining literals.
|
|
*/
|
|
sequences[seq].litLength -= remaining;
|
|
*nbSeq = seq;
|
|
sequence.offset = 0;
|
|
} else if (remaining < sequence.litLength + sequence.matchLength) {
|
|
/* Split the match up into two sequences. One in this block, and one
|
|
* in the next with no literals. If either match would be shorter
|
|
* than searchLength we omit it.
|
|
*/
|
|
U32 const matchPrefix = remaining - sequence.litLength;
|
|
U32 const matchSuffix = sequence.matchLength - matchPrefix;
|
|
|
|
assert(remaining > sequence.litLength);
|
|
assert(matchPrefix < sequence.matchLength);
|
|
assert(matchPrefix + matchSuffix == sequence.matchLength);
|
|
/* Update the current sequence */
|
|
sequence.matchLength = matchPrefix;
|
|
/* Update the next sequence when long enough, otherwise omit it. */
|
|
if (matchSuffix >= minMatch) {
|
|
sequences[seq].litLength = 0;
|
|
sequences[seq].matchLength = matchSuffix;
|
|
*nbSeq = seq;
|
|
} else {
|
|
sequences[seq + 1].litLength += matchSuffix;
|
|
*nbSeq = seq + 1;
|
|
}
|
|
if (sequence.matchLength < minMatch) {
|
|
/* Skip the current sequence if it is too short */
|
|
sequence.offset = 0;
|
|
}
|
|
}
|
|
return sequence;
|
|
}
|
|
#endif
|
|
|
|
size_t ZSTD_ldm_blockCompress(rawSeq const* sequences, size_t nbSeq,
|
|
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)
|
|
{
|
|
ZSTD_blockCompressor const blockCompressor =
|
|
ZSTD_selectBlockCompressor(cParams->strategy, extDict);
|
|
BYTE const* const base = ms->window.base;
|
|
/* Input bounds */
|
|
BYTE const* const istart = (BYTE const*)src;
|
|
BYTE const* const iend = istart + srcSize;
|
|
/* Input positions */
|
|
BYTE const* ip = istart;
|
|
size_t seq;
|
|
/* Loop through each sequence and apply the block compressor to the lits */
|
|
for (seq = 0; seq < nbSeq; ++seq) {
|
|
rawSeq const sequence = sequences[seq];
|
|
int i;
|
|
|
|
if (sequence.offset == 0)
|
|
break;
|
|
|
|
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 */
|
|
{
|
|
size_t const newLitLength =
|
|
blockCompressor(ms, seqStore, rep, cParams, ip,
|
|
sequence.litLength);
|
|
ip += sequence.litLength;
|
|
ms->nextToUpdate = (U32)(ip - base);
|
|
/* 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;
|
|
}
|
|
}
|
|
ZSTD_ldm_limitTableUpdate(ms, ip);
|
|
ZSTD_ldm_fillFastTables(ms, cParams, ip);
|
|
{
|
|
size_t const lastLiterals = blockCompressor(ms, seqStore, rep, cParams,
|
|
ip, iend - ip);
|
|
ms->nextToUpdate = (U32)(iend - base);
|
|
return lastLiterals;
|
|
}
|
|
}
|