725 lines
28 KiB
C
725 lines
28 KiB
C
/*
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* Copyright (c) Meta Platforms, Inc. and affiliates.
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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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* You may select, at your option, one of the above-listed licenses.
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*/
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#include "zstd_ldm.h"
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#include "../common/debug.h"
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#include "../common/xxhash.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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#include "zstd_ldm_geartab.h"
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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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typedef struct {
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U64 rolling;
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U64 stopMask;
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} ldmRollingHashState_t;
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/** ZSTD_ldm_gear_init():
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*
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* Initializes the rolling hash state such that it will honor the
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* settings in params. */
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static void ZSTD_ldm_gear_init(ldmRollingHashState_t* state, ldmParams_t const* params)
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{
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unsigned maxBitsInMask = MIN(params->minMatchLength, 64);
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unsigned hashRateLog = params->hashRateLog;
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state->rolling = ~(U32)0;
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/* The choice of the splitting criterion is subject to two conditions:
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* 1. it has to trigger on average every 2^(hashRateLog) bytes;
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* 2. ideally, it has to depend on a window of minMatchLength bytes.
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*
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* In the gear hash algorithm, bit n depends on the last n bytes;
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* so in order to obtain a good quality splitting criterion it is
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* preferable to use bits with high weight.
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*
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* To match condition 1 we use a mask with hashRateLog bits set
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* and, because of the previous remark, we make sure these bits
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* have the highest possible weight while still respecting
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* condition 2.
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*/
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if (hashRateLog > 0 && hashRateLog <= maxBitsInMask) {
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state->stopMask = (((U64)1 << hashRateLog) - 1) << (maxBitsInMask - hashRateLog);
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} else {
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/* In this degenerate case we simply honor the hash rate. */
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state->stopMask = ((U64)1 << hashRateLog) - 1;
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}
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}
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/** ZSTD_ldm_gear_reset()
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* Feeds [data, data + minMatchLength) into the hash without registering any
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* splits. This effectively resets the hash state. This is used when skipping
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* over data, either at the beginning of a block, or skipping sections.
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*/
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static void ZSTD_ldm_gear_reset(ldmRollingHashState_t* state,
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BYTE const* data, size_t minMatchLength)
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{
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U64 hash = state->rolling;
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size_t n = 0;
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#define GEAR_ITER_ONCE() do { \
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hash = (hash << 1) + ZSTD_ldm_gearTab[data[n] & 0xff]; \
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n += 1; \
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} while (0)
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while (n + 3 < minMatchLength) {
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GEAR_ITER_ONCE();
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GEAR_ITER_ONCE();
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GEAR_ITER_ONCE();
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GEAR_ITER_ONCE();
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}
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while (n < minMatchLength) {
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GEAR_ITER_ONCE();
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}
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#undef GEAR_ITER_ONCE
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}
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/** ZSTD_ldm_gear_feed():
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*
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* Registers in the splits array all the split points found in the first
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* size bytes following the data pointer. This function terminates when
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* either all the data has been processed or LDM_BATCH_SIZE splits are
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* present in the splits array.
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*
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* Precondition: The splits array must not be full.
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* Returns: The number of bytes processed. */
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static size_t ZSTD_ldm_gear_feed(ldmRollingHashState_t* state,
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BYTE const* data, size_t size,
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size_t* splits, unsigned* numSplits)
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{
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size_t n;
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U64 hash, mask;
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hash = state->rolling;
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mask = state->stopMask;
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n = 0;
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#define GEAR_ITER_ONCE() do { \
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hash = (hash << 1) + ZSTD_ldm_gearTab[data[n] & 0xff]; \
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n += 1; \
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if (UNLIKELY((hash & mask) == 0)) { \
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splits[*numSplits] = n; \
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*numSplits += 1; \
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if (*numSplits == LDM_BATCH_SIZE) \
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goto done; \
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} \
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} while (0)
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while (n + 3 < size) {
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GEAR_ITER_ONCE();
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GEAR_ITER_ONCE();
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GEAR_ITER_ONCE();
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GEAR_ITER_ONCE();
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}
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while (n < size) {
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GEAR_ITER_ONCE();
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}
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#undef GEAR_ITER_ONCE
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done:
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state->rolling = hash;
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return n;
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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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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 (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 = ((size_t)1) << (params.hashLog - ldmBucketSizeLog);
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size_t const totalSize = ZSTD_cwksp_alloc_size(ldmBucketSize)
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+ ZSTD_cwksp_alloc_size(ldmHSize * sizeof(ldmEntry_t));
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return params.enableLdm == ZSTD_ps_enable ? 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 == ZSTD_ps_enable ? (maxChunkSize / params.minMatchLength) : 0;
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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 pOffset = ldmState->bucketOffsets + hash;
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unsigned const offset = *pOffset;
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*(ZSTD_ldm_getBucket(ldmState, hash, ldmParams) + offset) = entry;
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*pOffset = (BYTE)((offset + 1) & ((1u << ldmParams.bucketSizeLog) - 1));
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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* pMatchBase)
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{
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size_t matchLength = 0;
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while (pIn > pAnchor && pMatch > pMatchBase && 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_countBackwardsMatch_2segments() :
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* Returns the number of bytes that match backwards from pMatch,
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* even with the backwards match spanning 2 different segments.
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*
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* On reaching `pMatchBase`, start counting from mEnd */
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static size_t ZSTD_ldm_countBackwardsMatch_2segments(
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const BYTE* pIn, const BYTE* pAnchor,
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const BYTE* pMatch, const BYTE* pMatchBase,
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const BYTE* pExtDictStart, const BYTE* pExtDictEnd)
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{
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size_t matchLength = ZSTD_ldm_countBackwardsMatch(pIn, pAnchor, pMatch, pMatchBase);
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if (pMatch - matchLength != pMatchBase || pMatchBase == pExtDictStart) {
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/* If backwards match is entirely in the extDict or prefix, immediately return */
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return matchLength;
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}
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DEBUGLOG(7, "ZSTD_ldm_countBackwardsMatch_2segments: found 2-parts backwards match (length in prefix==%zu)", matchLength);
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matchLength += ZSTD_ldm_countBackwardsMatch(pIn - matchLength, pAnchor, pExtDictEnd, pExtDictStart);
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DEBUGLOG(7, "final backwards match length = %zu", matchLength);
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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, ZSTD_tfp_forCCtx);
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break;
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case ZSTD_dfast:
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ZSTD_fillDoubleHashTable(ms, iend, ZSTD_dtlm_fast, ZSTD_tfp_forCCtx);
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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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void ZSTD_ldm_fillHashTable(
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ldmState_t* ldmState, const BYTE* ip,
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const BYTE* iend, ldmParams_t const* params)
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{
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U32 const minMatchLength = params->minMatchLength;
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U32 const hBits = params->hashLog - params->bucketSizeLog;
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BYTE const* const base = ldmState->window.base;
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BYTE const* const istart = ip;
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ldmRollingHashState_t hashState;
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size_t* const splits = ldmState->splitIndices;
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unsigned numSplits;
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DEBUGLOG(5, "ZSTD_ldm_fillHashTable");
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ZSTD_ldm_gear_init(&hashState, params);
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while (ip < iend) {
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size_t hashed;
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unsigned n;
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numSplits = 0;
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hashed = ZSTD_ldm_gear_feed(&hashState, ip, iend - ip, splits, &numSplits);
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for (n = 0; n < numSplits; n++) {
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if (ip + splits[n] >= istart + minMatchLength) {
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BYTE const* const split = ip + splits[n] - minMatchLength;
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U64 const xxhash = XXH64(split, minMatchLength, 0);
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U32 const hash = (U32)(xxhash & (((U32)1 << hBits) - 1));
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ldmEntry_t entry;
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entry.offset = (U32)(split - base);
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entry.checksum = (U32)(xxhash >> 32);
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ZSTD_ldm_insertEntry(ldmState, hash, entry, *params);
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}
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}
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ip += hashed;
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}
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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 curr = (U32)(anchor - ms->window.base);
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if (curr > ms->nextToUpdate + 1024) {
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ms->nextToUpdate =
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curr - MIN(512, curr - 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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U32 const entsPerBucket = 1U << params->bucketSizeLog;
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U32 const hBits = params->hashLog - params->bucketSizeLog;
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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 - 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 state */
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ldmRollingHashState_t hashState;
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/* Arrays for staged-processing */
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size_t* const splits = ldmState->splitIndices;
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ldmMatchCandidate_t* const candidates = ldmState->matchCandidates;
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unsigned numSplits;
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if (srcSize < minMatchLength)
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return iend - anchor;
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/* Initialize the rolling hash state with the first minMatchLength bytes */
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ZSTD_ldm_gear_init(&hashState, params);
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ZSTD_ldm_gear_reset(&hashState, ip, minMatchLength);
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ip += minMatchLength;
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while (ip < ilimit) {
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size_t hashed;
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unsigned n;
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numSplits = 0;
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hashed = ZSTD_ldm_gear_feed(&hashState, ip, ilimit - ip,
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splits, &numSplits);
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for (n = 0; n < numSplits; n++) {
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BYTE const* const split = ip + splits[n] - minMatchLength;
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U64 const xxhash = XXH64(split, minMatchLength, 0);
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U32 const hash = (U32)(xxhash & (((U32)1 << hBits) - 1));
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candidates[n].split = split;
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candidates[n].hash = hash;
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candidates[n].checksum = (U32)(xxhash >> 32);
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candidates[n].bucket = ZSTD_ldm_getBucket(ldmState, hash, *params);
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PREFETCH_L1(candidates[n].bucket);
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}
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for (n = 0; n < numSplits; n++) {
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size_t forwardMatchLength = 0, backwardMatchLength = 0,
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bestMatchLength = 0, mLength;
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U32 offset;
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BYTE const* const split = candidates[n].split;
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U32 const checksum = candidates[n].checksum;
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U32 const hash = candidates[n].hash;
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ldmEntry_t* const bucket = candidates[n].bucket;
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ldmEntry_t const* cur;
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ldmEntry_t const* bestEntry = NULL;
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ldmEntry_t newEntry;
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newEntry.offset = (U32)(split - base);
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newEntry.checksum = checksum;
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/* If a split point would generate a sequence overlapping with
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* the previous one, we merely register it in the hash table and
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* move on */
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if (split < anchor) {
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ZSTD_ldm_insertEntry(ldmState, hash, newEntry, *params);
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continue;
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}
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for (cur = bucket; cur < bucket + entsPerBucket; 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 =
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ZSTD_count_2segments(split, pMatch, iend, matchEnd, lowPrefixPtr);
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if (curForwardMatchLength < minMatchLength) {
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continue;
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}
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curBackwardMatchLength = ZSTD_ldm_countBackwardsMatch_2segments(
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split, anchor, pMatch, lowMatchPtr, dictStart, dictEnd);
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} else { /* !extDict */
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BYTE const* const pMatch = base + cur->offset;
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curForwardMatchLength = ZSTD_count(split, 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(split, anchor, pMatch, lowPrefixPtr);
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}
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curTotalMatchLength = curForwardMatchLength + curBackwardMatchLength;
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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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/* No match found -- insert an entry into the hash table
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* and process the next candidate match */
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if (bestEntry == NULL) {
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ZSTD_ldm_insertEntry(ldmState, hash, newEntry, *params);
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continue;
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}
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/* Match found */
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offset = (U32)(split - base) - bestEntry->offset;
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mLength = forwardMatchLength + backwardMatchLength;
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{
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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)(split - backwardMatchLength - 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 --- it must be
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* done after the previous block to avoid clobbering bestEntry */
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ZSTD_ldm_insertEntry(ldmState, hash, newEntry, *params);
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|
|
anchor = split + forwardMatchLength;
|
|
|
|
/* If we find a match that ends after the data that we've hashed
|
|
* then we have a repeating, overlapping, pattern. E.g. all zeros.
|
|
* If one repetition of the pattern matches our `stopMask` then all
|
|
* repetitions will. We don't need to insert them all into out table,
|
|
* only the first one. So skip over overlapping matches.
|
|
* This is a major speed boost (20x) for compressing a single byte
|
|
* repeated, when that byte ends up in the table.
|
|
*/
|
|
if (anchor > ip + hashed) {
|
|
ZSTD_ldm_gear_reset(&hashState, anchor - minMatchLength, minMatchLength);
|
|
/* Continue the outer loop at anchor (ip + hashed == anchor). */
|
|
ip = anchor - hashed;
|
|
break;
|
|
}
|
|
}
|
|
|
|
ip += hashed;
|
|
}
|
|
|
|
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 maximum 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, 0, maxDist, ldmState->loadedDictEnd, chunkStart, chunkEnd)) {
|
|
U32 const ldmHSize = 1U << params->hashLog;
|
|
U32 const correction = ZSTD_window_correctOverflow(
|
|
&ldmState->window, /* cycleLog */ 0, maxDist, chunkStart);
|
|
ZSTD_ldm_reduceTable(ldmState->hashTable, ldmHSize, correction);
|
|
/* invalidate dictionaries on overflow correction */
|
|
ldmState->loadedDictEnd = 0;
|
|
}
|
|
/* 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
|
|
* offset against maxDist directly.
|
|
*
|
|
* NOTE: Because of dictionaries + sequence splitting we MUST make sure
|
|
* that any offset used is valid at the END of the sequence, since it may
|
|
* be split into two sequences. This condition holds when using
|
|
* ZSTD_window_enforceMaxDist(), but if we move to checking offsets
|
|
* against maxDist directly, we'll have to carefully handle that case.
|
|
*/
|
|
ZSTD_window_enforceMaxDist(&ldmState->window, chunkEnd, maxDist, &ldmState->loadedDictEnd, 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;
|
|
}
|
|
|
|
void ZSTD_ldm_skipRawSeqStoreBytes(rawSeqStore_t* rawSeqStore, size_t nbBytes) {
|
|
U32 currPos = (U32)(rawSeqStore->posInSequence + nbBytes);
|
|
while (currPos && rawSeqStore->pos < rawSeqStore->size) {
|
|
rawSeq currSeq = rawSeqStore->seq[rawSeqStore->pos];
|
|
if (currPos >= currSeq.litLength + currSeq.matchLength) {
|
|
currPos -= currSeq.litLength + currSeq.matchLength;
|
|
rawSeqStore->pos++;
|
|
} else {
|
|
rawSeqStore->posInSequence = currPos;
|
|
break;
|
|
}
|
|
}
|
|
if (currPos == 0 || rawSeqStore->pos == rawSeqStore->size) {
|
|
rawSeqStore->posInSequence = 0;
|
|
}
|
|
}
|
|
|
|
size_t ZSTD_ldm_blockCompress(rawSeqStore_t* rawSeqStore,
|
|
ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
|
|
ZSTD_paramSwitch_e useRowMatchFinder,
|
|
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, useRowMatchFinder, 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);
|
|
/* If using opt parser, use LDMs only as candidates rather than always accepting them */
|
|
if (cParams->strategy >= ZSTD_btopt) {
|
|
size_t lastLLSize;
|
|
ms->ldmSeqStore = rawSeqStore;
|
|
lastLLSize = blockCompressor(ms, seqStore, rep, src, srcSize);
|
|
ZSTD_ldm_skipRawSeqStoreBytes(rawSeqStore, srcSize);
|
|
return lastLLSize;
|
|
}
|
|
|
|
assert(rawSeqStore->pos <= rawSeqStore->size);
|
|
assert(rawSeqStore->size <= rawSeqStore->capacity);
|
|
/* Loop through each sequence and apply the block compressor to the literals */
|
|
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(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, "pos %u : calling block compressor on segment of size %u", (unsigned)(ip-istart), 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, iend,
|
|
OFFSET_TO_OFFBASE(sequence.offset),
|
|
sequence.matchLength);
|
|
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);
|
|
}
|