--- /dev/null
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ * All rights reserved.
+ *
+ * This source code is licensed under both the BSD-style license (found in the
+ * LICENSE file in the root directory of this source tree) and the GPLv2 (found
+ * in the COPYING file in the root directory of this source tree).
+ * You may select, at your option, one of the above-listed licenses.
+ */
+
+#include "zstd_ldm.h"
+
+#include "../common/debug.h"
+#include "../common/xxhash.h"
+#include "zstd_fast.h" /* ZSTD_fillHashTable() */
+#include "zstd_double_fast.h" /* ZSTD_fillDoubleHashTable() */
+#include "zstd_ldm_geartab.h"
+
+#define LDM_BUCKET_SIZE_LOG 3
+#define LDM_MIN_MATCH_LENGTH 64
+#define LDM_HASH_RLOG 7
+
+typedef struct {
+ U64 rolling;
+ U64 stopMask;
+} ldmRollingHashState_t;
+
+/** ZSTD_ldm_gear_init():
+ *
+ * Initializes the rolling hash state such that it will honor the
+ * settings in params. */
+static void ZSTD_ldm_gear_init(ldmRollingHashState_t* state, ldmParams_t const* params)
+{
+ unsigned maxBitsInMask = MIN(params->minMatchLength, 64);
+ unsigned hashRateLog = params->hashRateLog;
+
+ state->rolling = ~(U32)0;
+
+ /* The choice of the splitting criterion is subject to two conditions:
+ * 1. it has to trigger on average every 2^(hashRateLog) bytes;
+ * 2. ideally, it has to depend on a window of minMatchLength bytes.
+ *
+ * In the gear hash algorithm, bit n depends on the last n bytes;
+ * so in order to obtain a good quality splitting criterion it is
+ * preferable to use bits with high weight.
+ *
+ * To match condition 1 we use a mask with hashRateLog bits set
+ * and, because of the previous remark, we make sure these bits
+ * have the highest possible weight while still respecting
+ * condition 2.
+ */
+ if (hashRateLog > 0 && hashRateLog <= maxBitsInMask) {
+ state->stopMask = (((U64)1 << hashRateLog) - 1) << (maxBitsInMask - hashRateLog);
+ } else {
+ /* In this degenerate case we simply honor the hash rate. */
+ state->stopMask = ((U64)1 << hashRateLog) - 1;
+ }
+}
+
+/** ZSTD_ldm_gear_reset()
+ * Feeds [data, data + minMatchLength) into the hash without registering any
+ * splits. This effectively resets the hash state. This is used when skipping
+ * over data, either at the beginning of a block, or skipping sections.
+ */
+static void ZSTD_ldm_gear_reset(ldmRollingHashState_t* state,
+ BYTE const* data, size_t minMatchLength)
+{
+ U64 hash = state->rolling;
+ size_t n = 0;
+
+#define GEAR_ITER_ONCE() do { \
+ hash = (hash << 1) + ZSTD_ldm_gearTab[data[n] & 0xff]; \
+ n += 1; \
+ } while (0)
+ while (n + 3 < minMatchLength) {
+ GEAR_ITER_ONCE();
+ GEAR_ITER_ONCE();
+ GEAR_ITER_ONCE();
+ GEAR_ITER_ONCE();
+ }
+ while (n < minMatchLength) {
+ GEAR_ITER_ONCE();
+ }
+#undef GEAR_ITER_ONCE
+}
+
+/** ZSTD_ldm_gear_feed():
+ *
+ * Registers in the splits array all the split points found in the first
+ * size bytes following the data pointer. This function terminates when
+ * either all the data has been processed or LDM_BATCH_SIZE splits are
+ * present in the splits array.
+ *
+ * Precondition: The splits array must not be full.
+ * Returns: The number of bytes processed. */
+static size_t ZSTD_ldm_gear_feed(ldmRollingHashState_t* state,
+ BYTE const* data, size_t size,
+ size_t* splits, unsigned* numSplits)
+{
+ size_t n;
+ U64 hash, mask;
+
+ hash = state->rolling;
+ mask = state->stopMask;
+ n = 0;
+
+#define GEAR_ITER_ONCE() do { \
+ hash = (hash << 1) + ZSTD_ldm_gearTab[data[n] & 0xff]; \
+ n += 1; \
+ if (UNLIKELY((hash & mask) == 0)) { \
+ splits[*numSplits] = n; \
+ *numSplits += 1; \
+ if (*numSplits == LDM_BATCH_SIZE) \
+ goto done; \
+ } \
+ } while (0)
+
+ while (n + 3 < size) {
+ GEAR_ITER_ONCE();
+ GEAR_ITER_ONCE();
+ GEAR_ITER_ONCE();
+ GEAR_ITER_ONCE();
+ }
+ while (n < size) {
+ GEAR_ITER_ONCE();
+ }
+
+#undef GEAR_ITER_ONCE
+
+done:
+ state->rolling = hash;
+ return n;
+}
+
+void ZSTD_ldm_adjustParameters(ldmParams_t* params,
+ ZSTD_compressionParameters const* cParams)
+{
+ params->windowLog = cParams->windowLog;
+ ZSTD_STATIC_ASSERT(LDM_BUCKET_SIZE_LOG <= ZSTD_LDM_BUCKETSIZELOG_MAX);
+ DEBUGLOG(4, "ZSTD_ldm_adjustParameters");
+ if (!params->bucketSizeLog) params->bucketSizeLog = LDM_BUCKET_SIZE_LOG;
+ if (!params->minMatchLength) params->minMatchLength = LDM_MIN_MATCH_LENGTH;
+ if (params->hashLog == 0) {
+ params->hashLog = MAX(ZSTD_HASHLOG_MIN, params->windowLog - LDM_HASH_RLOG);
+ assert(params->hashLog <= ZSTD_HASHLOG_MAX);
+ }
+ if (params->hashRateLog == 0) {
+ params->hashRateLog = params->windowLog < params->hashLog
+ ? 0
+ : params->windowLog - params->hashLog;
+ }
+ params->bucketSizeLog = MIN(params->bucketSizeLog, params->hashLog);
+}
+
+size_t ZSTD_ldm_getTableSize(ldmParams_t params)
+{
+ size_t const ldmHSize = ((size_t)1) << params.hashLog;
+ size_t const ldmBucketSizeLog = MIN(params.bucketSizeLog, params.hashLog);
+ size_t const ldmBucketSize = ((size_t)1) << (params.hashLog - ldmBucketSizeLog);
+ size_t const totalSize = ZSTD_cwksp_alloc_size(ldmBucketSize)
+ + ZSTD_cwksp_alloc_size(ldmHSize * sizeof(ldmEntry_t));
+ return params.enableLdm == ZSTD_ps_enable ? totalSize : 0;
+}
+
+size_t ZSTD_ldm_getMaxNbSeq(ldmParams_t params, size_t maxChunkSize)
+{
+ return params.enableLdm == ZSTD_ps_enable ? (maxChunkSize / params.minMatchLength) : 0;
+}
+
+/** ZSTD_ldm_getBucket() :
+ * Returns a pointer to the start of the bucket associated with hash. */
+static ldmEntry_t* ZSTD_ldm_getBucket(
+ ldmState_t* ldmState, size_t hash, ldmParams_t const ldmParams)
+{
+ return ldmState->hashTable + (hash << ldmParams.bucketSizeLog);
+}
+
+/** ZSTD_ldm_insertEntry() :
+ * Insert the entry with corresponding hash into the hash table */
+static void ZSTD_ldm_insertEntry(ldmState_t* ldmState,
+ size_t const hash, const ldmEntry_t entry,
+ ldmParams_t const ldmParams)
+{
+ BYTE* const pOffset = ldmState->bucketOffsets + hash;
+ unsigned const offset = *pOffset;
+
+ *(ZSTD_ldm_getBucket(ldmState, hash, ldmParams) + offset) = entry;
+ *pOffset = (BYTE)((offset + 1) & ((1u << ldmParams.bucketSizeLog) - 1));
+
+}
+
+/** ZSTD_ldm_countBackwardsMatch() :
+ * Returns the number of bytes that match backwards before pIn and pMatch.
+ *
+ * We count only bytes where pMatch >= pBase and pIn >= pAnchor. */
+static size_t ZSTD_ldm_countBackwardsMatch(
+ const BYTE* pIn, const BYTE* pAnchor,
+ const BYTE* pMatch, const BYTE* pMatchBase)
+{
+ size_t matchLength = 0;
+ while (pIn > pAnchor && pMatch > pMatchBase && pIn[-1] == pMatch[-1]) {
+ pIn--;
+ pMatch--;
+ matchLength++;
+ }
+ return matchLength;
+}
+
+/** ZSTD_ldm_countBackwardsMatch_2segments() :
+ * Returns the number of bytes that match backwards from pMatch,
+ * even with the backwards match spanning 2 different segments.
+ *
+ * On reaching `pMatchBase`, start counting from mEnd */
+static size_t ZSTD_ldm_countBackwardsMatch_2segments(
+ const BYTE* pIn, const BYTE* pAnchor,
+ const BYTE* pMatch, const BYTE* pMatchBase,
+ const BYTE* pExtDictStart, const BYTE* pExtDictEnd)
+{
+ size_t matchLength = ZSTD_ldm_countBackwardsMatch(pIn, pAnchor, pMatch, pMatchBase);
+ if (pMatch - matchLength != pMatchBase || pMatchBase == pExtDictStart) {
+ /* If backwards match is entirely in the extDict or prefix, immediately return */
+ return matchLength;
+ }
+ DEBUGLOG(7, "ZSTD_ldm_countBackwardsMatch_2segments: found 2-parts backwards match (length in prefix==%zu)", matchLength);
+ matchLength += ZSTD_ldm_countBackwardsMatch(pIn - matchLength, pAnchor, pExtDictEnd, pExtDictStart);
+ DEBUGLOG(7, "final backwards match length = %zu", matchLength);
+ return matchLength;
+}
+
+/** ZSTD_ldm_fillFastTables() :
+ *
+ * Fills the relevant tables for the ZSTD_fast and ZSTD_dfast strategies.
+ * This is similar to ZSTD_loadDictionaryContent.
+ *
+ * The tables for the other strategies are filled within their
+ * block compressors. */
+static size_t ZSTD_ldm_fillFastTables(ZSTD_matchState_t* ms,
+ void const* end)
+{
+ const BYTE* const iend = (const BYTE*)end;
+
+ switch(ms->cParams.strategy)
+ {
+ case ZSTD_fast:
+ ZSTD_fillHashTable(ms, iend, ZSTD_dtlm_fast, ZSTD_tfp_forCCtx);
+ break;
+
+ case ZSTD_dfast:
+ ZSTD_fillDoubleHashTable(ms, iend, ZSTD_dtlm_fast, ZSTD_tfp_forCCtx);
+ break;
+
+ case ZSTD_greedy:
+ case ZSTD_lazy:
+ case ZSTD_lazy2:
+ case ZSTD_btlazy2:
+ case ZSTD_btopt:
+ case ZSTD_btultra:
+ case ZSTD_btultra2:
+ break;
+ default:
+ assert(0); /* not possible : not a valid strategy id */
+ }
+
+ return 0;
+}
+
+void ZSTD_ldm_fillHashTable(
+ ldmState_t* ldmState, const BYTE* ip,
+ const BYTE* iend, ldmParams_t const* params)
+{
+ U32 const minMatchLength = params->minMatchLength;
+ U32 const hBits = params->hashLog - params->bucketSizeLog;
+ BYTE const* const base = ldmState->window.base;
+ BYTE const* const istart = ip;
+ ldmRollingHashState_t hashState;
+ size_t* const splits = ldmState->splitIndices;
+ unsigned numSplits;
+
+ DEBUGLOG(5, "ZSTD_ldm_fillHashTable");
+
+ ZSTD_ldm_gear_init(&hashState, params);
+ while (ip < iend) {
+ size_t hashed;
+ unsigned n;
+
+ numSplits = 0;
+ hashed = ZSTD_ldm_gear_feed(&hashState, ip, iend - ip, splits, &numSplits);
+
+ for (n = 0; n < numSplits; n++) {
+ if (ip + splits[n] >= istart + minMatchLength) {
+ BYTE const* const split = ip + splits[n] - minMatchLength;
+ U64 const xxhash = XXH64(split, minMatchLength, 0);
+ U32 const hash = (U32)(xxhash & (((U32)1 << hBits) - 1));
+ ldmEntry_t entry;
+
+ entry.offset = (U32)(split - base);
+ entry.checksum = (U32)(xxhash >> 32);
+ ZSTD_ldm_insertEntry(ldmState, hash, entry, *params);
+ }
+ }
+
+ ip += hashed;
+ }
+}
+
+
+/** ZSTD_ldm_limitTableUpdate() :
+ *
+ * Sets cctx->nextToUpdate to a position corresponding closer to anchor
+ * if it is far way
+ * (after a long match, only update tables a limited amount). */
+static void ZSTD_ldm_limitTableUpdate(ZSTD_matchState_t* ms, const BYTE* anchor)
+{
+ U32 const curr = (U32)(anchor - ms->window.base);
+ if (curr > ms->nextToUpdate + 1024) {
+ ms->nextToUpdate =
+ curr - MIN(512, curr - ms->nextToUpdate - 1024);
+ }
+}
+
+static size_t ZSTD_ldm_generateSequences_internal(
+ ldmState_t* ldmState, rawSeqStore_t* rawSeqStore,
+ ldmParams_t const* params, void const* src, size_t srcSize)
+{
+ /* LDM parameters */
+ int const extDict = ZSTD_window_hasExtDict(ldmState->window);
+ U32 const minMatchLength = params->minMatchLength;
+ U32 const entsPerBucket = 1U << params->bucketSizeLog;
+ U32 const hBits = params->hashLog - params->bucketSizeLog;
+ /* Prefix and extDict parameters */
+ U32 const dictLimit = ldmState->window.dictLimit;
+ U32 const lowestIndex = extDict ? ldmState->window.lowLimit : dictLimit;
+ BYTE const* const base = ldmState->window.base;
+ BYTE const* const dictBase = extDict ? ldmState->window.dictBase : NULL;
+ BYTE const* const dictStart = extDict ? dictBase + lowestIndex : NULL;
+ BYTE const* const dictEnd = extDict ? dictBase + dictLimit : NULL;
+ BYTE const* const lowPrefixPtr = base + dictLimit;
+ /* Input bounds */
+ BYTE const* const istart = (BYTE const*)src;
+ BYTE const* const iend = istart + srcSize;
+ BYTE const* const ilimit = iend - HASH_READ_SIZE;
+ /* Input positions */
+ BYTE const* anchor = istart;
+ BYTE const* ip = istart;
+ /* Rolling hash state */
+ ldmRollingHashState_t hashState;
+ /* Arrays for staged-processing */
+ size_t* const splits = ldmState->splitIndices;
+ ldmMatchCandidate_t* const candidates = ldmState->matchCandidates;
+ unsigned numSplits;
+
+ if (srcSize < minMatchLength)
+ return iend - anchor;
+
+ /* Initialize the rolling hash state with the first minMatchLength bytes */
+ ZSTD_ldm_gear_init(&hashState, params);
+ ZSTD_ldm_gear_reset(&hashState, ip, minMatchLength);
+ ip += minMatchLength;
+
+ while (ip < ilimit) {
+ size_t hashed;
+ unsigned n;
+
+ numSplits = 0;
+ hashed = ZSTD_ldm_gear_feed(&hashState, ip, ilimit - ip,
+ splits, &numSplits);
+
+ for (n = 0; n < numSplits; n++) {
+ BYTE const* const split = ip + splits[n] - minMatchLength;
+ U64 const xxhash = XXH64(split, minMatchLength, 0);
+ U32 const hash = (U32)(xxhash & (((U32)1 << hBits) - 1));
+
+ candidates[n].split = split;
+ candidates[n].hash = hash;
+ candidates[n].checksum = (U32)(xxhash >> 32);
+ candidates[n].bucket = ZSTD_ldm_getBucket(ldmState, hash, *params);
+ PREFETCH_L1(candidates[n].bucket);
+ }
+
+ for (n = 0; n < numSplits; n++) {
+ size_t forwardMatchLength = 0, backwardMatchLength = 0,
+ bestMatchLength = 0, mLength;
+ U32 offset;
+ BYTE const* const split = candidates[n].split;
+ U32 const checksum = candidates[n].checksum;
+ U32 const hash = candidates[n].hash;
+ ldmEntry_t* const bucket = candidates[n].bucket;
+ ldmEntry_t const* cur;
+ ldmEntry_t const* bestEntry = NULL;
+ ldmEntry_t newEntry;
+
+ newEntry.offset = (U32)(split - base);
+ newEntry.checksum = checksum;
+
+ /* If a split point would generate a sequence overlapping with
+ * the previous one, we merely register it in the hash table and
+ * move on */
+ if (split < anchor) {
+ ZSTD_ldm_insertEntry(ldmState, hash, newEntry, *params);
+ continue;
+ }
+
+ for (cur = bucket; cur < bucket + entsPerBucket; cur++) {
+ size_t curForwardMatchLength, curBackwardMatchLength,
+ curTotalMatchLength;
+ if (cur->checksum != checksum || cur->offset <= lowestIndex) {
+ continue;
+ }
+ if (extDict) {
+ BYTE const* const curMatchBase =
+ cur->offset < dictLimit ? dictBase : base;
+ BYTE const* const pMatch = curMatchBase + cur->offset;
+ BYTE const* const matchEnd =
+ cur->offset < dictLimit ? dictEnd : iend;
+ BYTE const* const lowMatchPtr =
+ cur->offset < dictLimit ? dictStart : lowPrefixPtr;
+ curForwardMatchLength =
+ ZSTD_count_2segments(split, pMatch, iend, matchEnd, lowPrefixPtr);
+ if (curForwardMatchLength < minMatchLength) {
+ continue;
+ }
+ curBackwardMatchLength = ZSTD_ldm_countBackwardsMatch_2segments(
+ split, anchor, pMatch, lowMatchPtr, dictStart, dictEnd);
+ } else { /* !extDict */
+ BYTE const* const pMatch = base + cur->offset;
+ curForwardMatchLength = ZSTD_count(split, pMatch, iend);
+ if (curForwardMatchLength < minMatchLength) {
+ continue;
+ }
+ curBackwardMatchLength =
+ ZSTD_ldm_countBackwardsMatch(split, anchor, pMatch, lowPrefixPtr);
+ }
+ curTotalMatchLength = curForwardMatchLength + curBackwardMatchLength;
+
+ if (curTotalMatchLength > bestMatchLength) {
+ bestMatchLength = curTotalMatchLength;
+ forwardMatchLength = curForwardMatchLength;
+ backwardMatchLength = curBackwardMatchLength;
+ bestEntry = cur;
+ }
+ }
+
+ /* No match found -- insert an entry into the hash table
+ * and process the next candidate match */
+ if (bestEntry == NULL) {
+ ZSTD_ldm_insertEntry(ldmState, hash, newEntry, *params);
+ continue;
+ }
+
+ /* Match found */
+ offset = (U32)(split - base) - bestEntry->offset;
+ mLength = forwardMatchLength + backwardMatchLength;
+ {
+ rawSeq* const seq = rawSeqStore->seq + rawSeqStore->size;
+
+ /* Out of sequence storage */
+ if (rawSeqStore->size == rawSeqStore->capacity)
+ return ERROR(dstSize_tooSmall);
+ seq->litLength = (U32)(split - backwardMatchLength - anchor);
+ seq->matchLength = (U32)mLength;
+ seq->offset = offset;
+ rawSeqStore->size++;
+ }
+
+ /* Insert the current entry into the hash table --- it must be
+ * done after the previous block to avoid clobbering bestEntry */
+ ZSTD_ldm_insertEntry(ldmState, hash, newEntry, *params);
+
+ 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);
+}
notaz.gp2x.de / pcsx_rearmed.git / blobdiff