--- /dev/null
- assert(numTagBits <= 32 && hbits <= 32);
+/*
+ * Copyright (c) 2016-present, Yann Collet, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under both the BSD-style license (found in the
+ * LICENSE file in the root directory of this source tree) and the GPLv2 (found
+ * in the COPYING file in the root directory of this source tree).
+ */
+
+#include "zstd_ldm.h"
+
+#include "zstd_fast.h" /* ZSTD_fillHashTable() */
+#include "zstd_double_fast.h" /* ZSTD_fillDoubleHashTable() */
+
+#define LDM_BUCKET_SIZE_LOG 3
+#define LDM_MIN_MATCH_LENGTH 64
+#define LDM_HASH_LOG 20
+#define LDM_HASH_CHAR_OFFSET 10
+
+size_t ZSTD_ldm_initializeParameters(ldmParams_t* params, U32 enableLdm)
+{
+ ZSTD_STATIC_ASSERT(LDM_BUCKET_SIZE_LOG <= ZSTD_LDM_BUCKETSIZELOG_MAX);
+ params->enableLdm = enableLdm>0;
+ params->hashLog = LDM_HASH_LOG;
+ params->bucketSizeLog = LDM_BUCKET_SIZE_LOG;
+ params->minMatchLength = LDM_MIN_MATCH_LENGTH;
+ params->hashEveryLog = ZSTD_LDM_HASHEVERYLOG_NOTSET;
+ return 0;
+}
+
+void ZSTD_ldm_adjustParameters(ldmParams_t* params, U32 windowLog)
+{
+ if (params->hashEveryLog == ZSTD_LDM_HASHEVERYLOG_NOTSET) {
+ params->hashEveryLog =
+ windowLog < params->hashLog ? 0 : windowLog - params->hashLog;
+ }
+ params->bucketSizeLog = MIN(params->bucketSizeLog, params->hashLog);
+}
+
+size_t ZSTD_ldm_getTableSize(U32 hashLog, U32 bucketSizeLog) {
+ size_t const ldmHSize = ((size_t)1) << hashLog;
+ size_t const ldmBucketSizeLog = MIN(bucketSizeLog, hashLog);
+ size_t const ldmBucketSize =
+ ((size_t)1) << (hashLog - ldmBucketSizeLog);
+ return ldmBucketSize + (ldmHSize * (sizeof(ldmEntry_t)));
+}
+
+/** ZSTD_ldm_getSmallHash() :
+ * numBits should be <= 32
+ * If numBits==0, returns 0.
+ * @return : the most significant numBits of value. */
+static U32 ZSTD_ldm_getSmallHash(U64 value, U32 numBits)
+{
+ assert(numBits <= 32);
+ return numBits == 0 ? 0 : (U32)(value >> (64 - numBits));
+}
+
+/** ZSTD_ldm_getChecksum() :
+ * numBitsToDiscard should be <= 32
+ * @return : the next most significant 32 bits after numBitsToDiscard */
+static U32 ZSTD_ldm_getChecksum(U64 hash, U32 numBitsToDiscard)
+{
+ assert(numBitsToDiscard <= 32);
+ return (hash >> (64 - 32 - numBitsToDiscard)) & 0xFFFFFFFF;
+}
+
+/** ZSTD_ldm_getTag() ;
+ * Given the hash, returns the most significant numTagBits bits
+ * after (32 + hbits) bits.
+ *
+ * If there are not enough bits remaining, return the last
+ * numTagBits bits. */
+static U32 ZSTD_ldm_getTag(U64 hash, U32 hbits, U32 numTagBits)
+{
- return hash & ((1 << numTagBits) - 1);
++ assert(numTagBits < 32 && hbits <= 32);
+ if (32 - hbits < numTagBits) {
- return (hash >> (32 - hbits - numTagBits)) & ((1 << numTagBits) - 1);
++ return hash & (((U32)1 << numTagBits) - 1);
+ } else {
- bucketOffsets[hash] &= (1 << ldmParams.bucketSizeLog) - 1;
++ return (hash >> (32 - hbits - numTagBits)) & (((U32)1 << numTagBits) - 1);
+ }
+}
+
+/** ZSTD_ldm_getBucket() :
+ * Returns a pointer to the start of the bucket associated with hash. */
+static ldmEntry_t* ZSTD_ldm_getBucket(
+ ldmState_t* ldmState, size_t hash, ldmParams_t const ldmParams)
+{
+ return ldmState->hashTable + (hash << ldmParams.bucketSizeLog);
+}
+
+/** ZSTD_ldm_insertEntry() :
+ * Insert the entry with corresponding hash into the hash table */
+static void ZSTD_ldm_insertEntry(ldmState_t* ldmState,
+ size_t const hash, const ldmEntry_t entry,
+ ldmParams_t const ldmParams)
+{
+ BYTE* const bucketOffsets = ldmState->bucketOffsets;
+ *(ZSTD_ldm_getBucket(ldmState, hash, ldmParams) + bucketOffsets[hash]) = entry;
+ bucketOffsets[hash]++;
- U32 const tagMask = (1 << ldmParams.hashEveryLog) - 1;
++ bucketOffsets[hash] &= ((U32)1 << ldmParams.bucketSizeLog) - 1;
+}
+
+/** ZSTD_ldm_makeEntryAndInsertByTag() :
+ *
+ * Gets the small hash, checksum, and tag from the rollingHash.
+ *
+ * If the tag matches (1 << ldmParams.hashEveryLog)-1, then
+ * creates an ldmEntry from the offset, and inserts it into the hash table.
+ *
+ * hBits is the length of the small hash, which is the most significant hBits
+ * of rollingHash. The checksum is the next 32 most significant bits, followed
+ * by ldmParams.hashEveryLog bits that make up the tag. */
+static void ZSTD_ldm_makeEntryAndInsertByTag(ldmState_t* ldmState,
+ U64 const rollingHash,
+ U32 const hBits,
+ U32 const offset,
+ ldmParams_t const ldmParams)
+{
+ U32 const tag = ZSTD_ldm_getTag(rollingHash, hBits, ldmParams.hashEveryLog);
- const U32 ldmBucketSize = (1 << ldmParams.bucketSizeLog);
- const U32 ldmTagMask = (1 << ldmParams.hashEveryLog) - 1;
++ U32 const tagMask = ((U32)1 << ldmParams.hashEveryLog) - 1;
+ if (tag == tagMask) {
+ U32 const hash = ZSTD_ldm_getSmallHash(rollingHash, hBits);
+ U32 const checksum = ZSTD_ldm_getChecksum(rollingHash, hBits);
+ ldmEntry_t entry;
+ entry.offset = offset;
+ entry.checksum = checksum;
+ ZSTD_ldm_insertEntry(ldmState, hash, entry, ldmParams);
+ }
+}
+
+/** ZSTD_ldm_getRollingHash() :
+ * Get a 64-bit hash using the first len bytes from buf.
+ *
+ * Giving bytes s = s_1, s_2, ... s_k, the hash is defined to be
+ * H(s) = s_1*(a^(k-1)) + s_2*(a^(k-2)) + ... + s_k*(a^0)
+ *
+ * where the constant a is defined to be prime8bytes.
+ *
+ * The implementation adds an offset to each byte, so
+ * H(s) = (s_1 + HASH_CHAR_OFFSET)*(a^(k-1)) + ... */
+static U64 ZSTD_ldm_getRollingHash(const BYTE* buf, U32 len)
+{
+ U64 ret = 0;
+ U32 i;
+ for (i = 0; i < len; i++) {
+ ret *= prime8bytes;
+ ret += buf[i] + LDM_HASH_CHAR_OFFSET;
+ }
+ return ret;
+}
+
+/** ZSTD_ldm_ipow() :
+ * Return base^exp. */
+static U64 ZSTD_ldm_ipow(U64 base, U64 exp)
+{
+ U64 ret = 1;
+ while (exp) {
+ if (exp & 1) { ret *= base; }
+ exp >>= 1;
+ base *= base;
+ }
+ return ret;
+}
+
+U64 ZSTD_ldm_getHashPower(U32 minMatchLength) {
+ assert(minMatchLength >= ZSTD_LDM_MINMATCH_MIN);
+ return ZSTD_ldm_ipow(prime8bytes, minMatchLength - 1);
+}
+
+/** ZSTD_ldm_updateHash() :
+ * Updates hash by removing toRemove and adding toAdd. */
+static U64 ZSTD_ldm_updateHash(U64 hash, BYTE toRemove, BYTE toAdd, U64 hashPower)
+{
+ hash -= ((toRemove + LDM_HASH_CHAR_OFFSET) * hashPower);
+ hash *= prime8bytes;
+ hash += toAdd + LDM_HASH_CHAR_OFFSET;
+ return hash;
+}
+
+/** ZSTD_ldm_countBackwardsMatch() :
+ * Returns the number of bytes that match backwards before pIn and pMatch.
+ *
+ * We count only bytes where pMatch >= pBase and pIn >= pAnchor. */
+static size_t ZSTD_ldm_countBackwardsMatch(
+ const BYTE* pIn, const BYTE* pAnchor,
+ const BYTE* pMatch, const BYTE* pBase)
+{
+ size_t matchLength = 0;
+ while (pIn > pAnchor && pMatch > pBase && pIn[-1] == pMatch[-1]) {
+ pIn--;
+ pMatch--;
+ matchLength++;
+ }
+ return matchLength;
+}
+
+/** ZSTD_ldm_fillFastTables() :
+ *
+ * Fills the relevant tables for the ZSTD_fast and ZSTD_dfast strategies.
+ * This is similar to ZSTD_loadDictionaryContent.
+ *
+ * The tables for the other strategies are filled within their
+ * block compressors. */
+static size_t ZSTD_ldm_fillFastTables(ZSTD_CCtx* zc, const void* end)
+{
+ const BYTE* const iend = (const BYTE*)end;
+ const U32 mls = zc->appliedParams.cParams.searchLength;
+
+ switch(zc->appliedParams.cParams.strategy)
+ {
+ case ZSTD_fast:
+ ZSTD_fillHashTable(zc, iend, mls);
+ zc->nextToUpdate = (U32)(iend - zc->base);
+ break;
+
+ case ZSTD_dfast:
+ ZSTD_fillDoubleHashTable(zc, iend, mls);
+ zc->nextToUpdate = (U32)(iend - zc->base);
+ break;
+
+ case ZSTD_greedy:
+ case ZSTD_lazy:
+ case ZSTD_lazy2:
+ case ZSTD_btlazy2:
+ case ZSTD_btopt:
+ case ZSTD_btultra:
+ break;
+ default:
+ assert(0); /* not possible : not a valid strategy id */
+ }
+
+ return 0;
+}
+
+/** ZSTD_ldm_fillLdmHashTable() :
+ *
+ * Fills hashTable from (lastHashed + 1) to iend (non-inclusive).
+ * lastHash is the rolling hash that corresponds to lastHashed.
+ *
+ * Returns the rolling hash corresponding to position iend-1. */
+static U64 ZSTD_ldm_fillLdmHashTable(ldmState_t* state,
+ U64 lastHash, const BYTE* lastHashed,
+ const BYTE* iend, const BYTE* base,
+ U32 hBits, ldmParams_t const ldmParams)
+{
+ U64 rollingHash = lastHash;
+ const BYTE* cur = lastHashed + 1;
+
+ while (cur < iend) {
+ rollingHash = ZSTD_ldm_updateHash(rollingHash, cur[-1],
+ cur[ldmParams.minMatchLength-1],
+ state->hashPower);
+ ZSTD_ldm_makeEntryAndInsertByTag(state,
+ rollingHash, hBits,
+ (U32)(cur - base), ldmParams);
+ ++cur;
+ }
+ return rollingHash;
+}
+
+
+/** ZSTD_ldm_limitTableUpdate() :
+ *
+ * Sets cctx->nextToUpdate to a position corresponding closer to anchor
+ * if it is far way
+ * (after a long match, only update tables a limited amount). */
+static void ZSTD_ldm_limitTableUpdate(ZSTD_CCtx* cctx, const BYTE* anchor)
+{
+ U32 const current = (U32)(anchor - cctx->base);
+ if (current > cctx->nextToUpdate + 1024) {
+ cctx->nextToUpdate =
+ current - MIN(512, current - cctx->nextToUpdate - 1024);
+ }
+}
+
+typedef size_t (*ZSTD_blockCompressor) (ZSTD_CCtx* ctx, const void* src, size_t srcSize);
+/* defined in zstd_compress.c */
+ZSTD_blockCompressor ZSTD_selectBlockCompressor(ZSTD_strategy strat, int extDict);
+
+FORCE_INLINE_TEMPLATE
+size_t ZSTD_compressBlock_ldm_generic(ZSTD_CCtx* cctx,
+ const void* src, size_t srcSize)
+{
+ ldmState_t* const ldmState = &(cctx->ldmState);
+ const ldmParams_t ldmParams = cctx->appliedParams.ldmParams;
+ const U64 hashPower = ldmState->hashPower;
+ const U32 hBits = ldmParams.hashLog - ldmParams.bucketSizeLog;
- size_t ZSTD_compressBlock_ldm(ZSTD_CCtx* ctx, const void* src, size_t srcSize)
++ const U32 ldmBucketSize = ((U32)1 << ldmParams.bucketSizeLog);
++ const U32 ldmTagMask = ((U32)1 << ldmParams.hashEveryLog) - 1;
+ seqStore_t* const seqStorePtr = &(cctx->seqStore);
+ const BYTE* const base = cctx->base;
+ const BYTE* const istart = (const BYTE*)src;
+ const BYTE* ip = istart;
+ const BYTE* anchor = istart;
+ const U32 lowestIndex = cctx->dictLimit;
+ const BYTE* const lowest = base + lowestIndex;
+ const BYTE* const iend = istart + srcSize;
+ const BYTE* const ilimit = iend - ldmParams.minMatchLength;
+
+ const ZSTD_blockCompressor blockCompressor =
+ ZSTD_selectBlockCompressor(cctx->appliedParams.cParams.strategy, 0);
+ U32* const repToConfirm = seqStorePtr->repToConfirm;
+ U32 savedRep[ZSTD_REP_NUM];
+ U64 rollingHash = 0;
+ const BYTE* lastHashed = NULL;
+ size_t i, lastLiterals;
+
+ /* Save seqStorePtr->rep and copy repToConfirm */
+ for (i = 0; i < ZSTD_REP_NUM; i++)
+ savedRep[i] = repToConfirm[i] = seqStorePtr->rep[i];
+
+ /* Main Search Loop */
+ while (ip < ilimit) { /* < instead of <=, because repcode check at (ip+1) */
+ size_t mLength;
+ U32 const current = (U32)(ip - base);
+ size_t forwardMatchLength = 0, backwardMatchLength = 0;
+ ldmEntry_t* bestEntry = NULL;
+ if (ip != istart) {
+ rollingHash = ZSTD_ldm_updateHash(rollingHash, lastHashed[0],
+ lastHashed[ldmParams.minMatchLength],
+ hashPower);
+ } else {
+ rollingHash = ZSTD_ldm_getRollingHash(ip, ldmParams.minMatchLength);
+ }
+ lastHashed = ip;
+
+ /* Do not insert and do not look for a match */
+ if (ZSTD_ldm_getTag(rollingHash, hBits, ldmParams.hashEveryLog) !=
+ ldmTagMask) {
+ ip++;
+ continue;
+ }
+
+ /* Get the best entry and compute the match lengths */
+ {
+ ldmEntry_t* const bucket =
+ ZSTD_ldm_getBucket(ldmState,
+ ZSTD_ldm_getSmallHash(rollingHash, hBits),
+ ldmParams);
+ ldmEntry_t* cur;
+ size_t bestMatchLength = 0;
+ U32 const checksum = ZSTD_ldm_getChecksum(rollingHash, hBits);
+
+ for (cur = bucket; cur < bucket + ldmBucketSize; ++cur) {
+ const BYTE* const pMatch = cur->offset + base;
+ size_t curForwardMatchLength, curBackwardMatchLength,
+ curTotalMatchLength;
+ if (cur->checksum != checksum || cur->offset <= lowestIndex) {
+ continue;
+ }
+
+ curForwardMatchLength = ZSTD_count(ip, pMatch, iend);
+ if (curForwardMatchLength < ldmParams.minMatchLength) {
+ continue;
+ }
+ curBackwardMatchLength = ZSTD_ldm_countBackwardsMatch(
+ ip, anchor, pMatch, lowest);
+ curTotalMatchLength = curForwardMatchLength +
+ curBackwardMatchLength;
+
+ if (curTotalMatchLength > bestMatchLength) {
+ bestMatchLength = curTotalMatchLength;
+ forwardMatchLength = curForwardMatchLength;
+ backwardMatchLength = curBackwardMatchLength;
+ bestEntry = cur;
+ }
+ }
+ }
+
+ /* No match found -- continue searching */
+ if (bestEntry == NULL) {
+ ZSTD_ldm_makeEntryAndInsertByTag(ldmState, rollingHash,
+ hBits, current,
+ ldmParams);
+ ip++;
+ continue;
+ }
+
+ /* Match found */
+ mLength = forwardMatchLength + backwardMatchLength;
+ ip -= backwardMatchLength;
+
+ /* Call the block compressor on the remaining literals */
+ {
+ U32 const matchIndex = bestEntry->offset;
+ const BYTE* const match = base + matchIndex - backwardMatchLength;
+ U32 const offset = (U32)(ip - match);
+
+ /* Overwrite rep codes */
+ for (i = 0; i < ZSTD_REP_NUM; i++)
+ seqStorePtr->rep[i] = repToConfirm[i];
+
+ /* Fill tables for block compressor */
+ ZSTD_ldm_limitTableUpdate(cctx, anchor);
+ ZSTD_ldm_fillFastTables(cctx, anchor);
+
+ /* Call block compressor and get remaining literals */
+ lastLiterals = blockCompressor(cctx, anchor, ip - anchor);
+ cctx->nextToUpdate = (U32)(ip - base);
+
+ /* Update repToConfirm with the new offset */
+ for (i = ZSTD_REP_NUM - 1; i > 0; i--)
+ repToConfirm[i] = repToConfirm[i-1];
+ repToConfirm[0] = offset;
+
+ /* Store the sequence with the leftover literals */
+ ZSTD_storeSeq(seqStorePtr, lastLiterals, ip - lastLiterals,
+ offset + ZSTD_REP_MOVE, mLength - MINMATCH);
+ }
+
+ /* Insert the current entry into the hash table */
+ ZSTD_ldm_makeEntryAndInsertByTag(ldmState, rollingHash, hBits,
+ (U32)(lastHashed - base),
+ ldmParams);
+
+ assert(ip + backwardMatchLength == lastHashed);
+
+ /* Fill the hash table from lastHashed+1 to ip+mLength*/
+ /* Heuristic: don't need to fill the entire table at end of block */
+ if (ip + mLength < ilimit) {
+ rollingHash = ZSTD_ldm_fillLdmHashTable(
+ ldmState, rollingHash, lastHashed,
+ ip + mLength, base, hBits, ldmParams);
+ lastHashed = ip + mLength - 1;
+ }
+ ip += mLength;
+ anchor = ip;
+ /* Check immediate repcode */
+ while ( (ip < ilimit)
+ && ( (repToConfirm[1] > 0) && (repToConfirm[1] <= (U32)(ip-lowest))
+ && (MEM_read32(ip) == MEM_read32(ip - repToConfirm[1])) )) {
+
+ size_t const rLength = ZSTD_count(ip+4, ip+4-repToConfirm[1],
+ iend) + 4;
+ /* Swap repToConfirm[1] <=> repToConfirm[0] */
+ {
+ U32 const tmpOff = repToConfirm[1];
+ repToConfirm[1] = repToConfirm[0];
+ repToConfirm[0] = tmpOff;
+ }
+
+ ZSTD_storeSeq(seqStorePtr, 0, anchor, 0, rLength-MINMATCH);
+
+ /* Fill the hash table from lastHashed+1 to ip+rLength*/
+ if (ip + rLength < ilimit) {
+ rollingHash = ZSTD_ldm_fillLdmHashTable(
+ ldmState, rollingHash, lastHashed,
+ ip + rLength, base, hBits, ldmParams);
+ lastHashed = ip + rLength - 1;
+ }
+ ip += rLength;
+ anchor = ip;
+ }
+ }
+
+ /* Overwrite rep */
+ for (i = 0; i < ZSTD_REP_NUM; i++)
+ seqStorePtr->rep[i] = repToConfirm[i];
+
+ ZSTD_ldm_limitTableUpdate(cctx, anchor);
+ ZSTD_ldm_fillFastTables(cctx, anchor);
+
+ lastLiterals = blockCompressor(cctx, anchor, iend - anchor);
+ cctx->nextToUpdate = (U32)(iend - base);
+
+ /* Restore seqStorePtr->rep */
+ for (i = 0; i < ZSTD_REP_NUM; i++)
+ seqStorePtr->rep[i] = savedRep[i];
+
+ /* Return the last literals size */
+ return lastLiterals;
+}
+
- const U32 ldmBucketSize = (1 << ldmParams.bucketSizeLog);
- const U32 ldmTagMask = (1 << ldmParams.hashEveryLog) - 1;
++size_t ZSTD_compressBlock_ldm(ZSTD_CCtx* ctx,
++ const void* src, size_t srcSize)
+{
+ return ZSTD_compressBlock_ldm_generic(ctx, src, srcSize);
+}
+
+static size_t ZSTD_compressBlock_ldm_extDict_generic(
+ ZSTD_CCtx* ctx,
+ const void* src, size_t srcSize)
+{
+ ldmState_t* const ldmState = &(ctx->ldmState);
+ const ldmParams_t ldmParams = ctx->appliedParams.ldmParams;
+ const U64 hashPower = ldmState->hashPower;
+ const U32 hBits = ldmParams.hashLog - ldmParams.bucketSizeLog;
++ const U32 ldmBucketSize = ((U32)1 << ldmParams.bucketSizeLog);
++ const U32 ldmTagMask = ((U32)1 << ldmParams.hashEveryLog) - 1;
+ seqStore_t* const seqStorePtr = &(ctx->seqStore);
+ const BYTE* const base = ctx->base;
+ const BYTE* const dictBase = ctx->dictBase;
+ const BYTE* const istart = (const BYTE*)src;
+ const BYTE* ip = istart;
+ const BYTE* anchor = istart;
+ const U32 lowestIndex = ctx->lowLimit;
+ const BYTE* const dictStart = dictBase + lowestIndex;
+ const U32 dictLimit = ctx->dictLimit;
+ const BYTE* const lowPrefixPtr = base + dictLimit;
+ const BYTE* const dictEnd = dictBase + dictLimit;
+ const BYTE* const iend = istart + srcSize;
+ const BYTE* const ilimit = iend - ldmParams.minMatchLength;
+
+ const ZSTD_blockCompressor blockCompressor =
+ ZSTD_selectBlockCompressor(ctx->appliedParams.cParams.strategy, 1);
+ U32* const repToConfirm = seqStorePtr->repToConfirm;
+ U32 savedRep[ZSTD_REP_NUM];
+ U64 rollingHash = 0;
+ const BYTE* lastHashed = NULL;
+ size_t i, lastLiterals;
+
+ /* Save seqStorePtr->rep and copy repToConfirm */
+ for (i = 0; i < ZSTD_REP_NUM; i++) {
+ savedRep[i] = repToConfirm[i] = seqStorePtr->rep[i];
+ }
+
+ /* Search Loop */
+ while (ip < ilimit) { /* < instead of <=, because (ip+1) */
+ size_t mLength;
+ const U32 current = (U32)(ip-base);
+ size_t forwardMatchLength = 0, backwardMatchLength = 0;
+ ldmEntry_t* bestEntry = NULL;
+ if (ip != istart) {
+ rollingHash = ZSTD_ldm_updateHash(rollingHash, lastHashed[0],
+ lastHashed[ldmParams.minMatchLength],
+ hashPower);
+ } else {
+ rollingHash = ZSTD_ldm_getRollingHash(ip, ldmParams.minMatchLength);
+ }
+ lastHashed = ip;
+
+ if (ZSTD_ldm_getTag(rollingHash, hBits, ldmParams.hashEveryLog) !=
+ ldmTagMask) {
+ /* Don't insert and don't look for a match */
+ ip++;
+ continue;
+ }
+
+ /* Get the best entry and compute the match lengths */
+ {
+ ldmEntry_t* const bucket =
+ ZSTD_ldm_getBucket(ldmState,
+ ZSTD_ldm_getSmallHash(rollingHash, hBits),
+ ldmParams);
+ ldmEntry_t* cur;
+ size_t bestMatchLength = 0;
+ U32 const checksum = ZSTD_ldm_getChecksum(rollingHash, hBits);
+
+ for (cur = bucket; cur < bucket + ldmBucketSize; ++cur) {
+ const BYTE* const curMatchBase =
+ cur->offset < dictLimit ? dictBase : base;
+ const BYTE* const pMatch = curMatchBase + cur->offset;
+ const BYTE* const matchEnd =
+ cur->offset < dictLimit ? dictEnd : iend;
+ const BYTE* const lowMatchPtr =
+ cur->offset < dictLimit ? dictStart : lowPrefixPtr;
+ size_t curForwardMatchLength, curBackwardMatchLength,
+ curTotalMatchLength;
+
+ if (cur->checksum != checksum || cur->offset <= lowestIndex) {
+ continue;
+ }
+
+ curForwardMatchLength = ZSTD_count_2segments(
+ ip, pMatch, iend,
+ matchEnd, lowPrefixPtr);
+ if (curForwardMatchLength < ldmParams.minMatchLength) {
+ continue;
+ }
+ curBackwardMatchLength = ZSTD_ldm_countBackwardsMatch(
+ ip, anchor, pMatch, lowMatchPtr);
+ curTotalMatchLength = curForwardMatchLength +
+ curBackwardMatchLength;
+
+ if (curTotalMatchLength > bestMatchLength) {
+ bestMatchLength = curTotalMatchLength;
+ forwardMatchLength = curForwardMatchLength;
+ backwardMatchLength = curBackwardMatchLength;
+ bestEntry = cur;
+ }
+ }
+ }
+
+ /* No match found -- continue searching */
+ if (bestEntry == NULL) {
+ ZSTD_ldm_makeEntryAndInsertByTag(ldmState, rollingHash, hBits,
+ (U32)(lastHashed - base),
+ ldmParams);
+ ip++;
+ continue;
+ }
+
+ /* Match found */
+ mLength = forwardMatchLength + backwardMatchLength;
+ ip -= backwardMatchLength;
+
+ /* Call the block compressor on the remaining literals */
+ {
+ /* ip = current - backwardMatchLength
+ * The match is at (bestEntry->offset - backwardMatchLength) */
+ U32 const matchIndex = bestEntry->offset;
+ U32 const offset = current - matchIndex;
+
+ /* Overwrite rep codes */
+ for (i = 0; i < ZSTD_REP_NUM; i++)
+ seqStorePtr->rep[i] = repToConfirm[i];
+
+ /* Fill the hash table for the block compressor */
+ ZSTD_ldm_limitTableUpdate(ctx, anchor);
+ ZSTD_ldm_fillFastTables(ctx, anchor);
+
+ /* Call block compressor and get remaining literals */
+ lastLiterals = blockCompressor(ctx, anchor, ip - anchor);
+ ctx->nextToUpdate = (U32)(ip - base);
+
+ /* Update repToConfirm with the new offset */
+ for (i = ZSTD_REP_NUM - 1; i > 0; i--)
+ repToConfirm[i] = repToConfirm[i-1];
+ repToConfirm[0] = offset;
+
+ /* Store the sequence with the leftover literals */
+ ZSTD_storeSeq(seqStorePtr, lastLiterals, ip - lastLiterals,
+ offset + ZSTD_REP_MOVE, mLength - MINMATCH);
+ }
+
+ /* Insert the current entry into the hash table */
+ ZSTD_ldm_makeEntryAndInsertByTag(ldmState, rollingHash, hBits,
+ (U32)(lastHashed - base),
+ ldmParams);
+
+ /* Fill the hash table from lastHashed+1 to ip+mLength */
+ assert(ip + backwardMatchLength == lastHashed);
+ if (ip + mLength < ilimit) {
+ rollingHash = ZSTD_ldm_fillLdmHashTable(
+ ldmState, rollingHash, lastHashed,
+ ip + mLength, base, hBits,
+ ldmParams);
+ lastHashed = ip + mLength - 1;
+ }
+ ip += mLength;
+ anchor = ip;
+
+ /* check immediate repcode */
+ while (ip < ilimit) {
+ U32 const current2 = (U32)(ip-base);
+ U32 const repIndex2 = current2 - repToConfirm[1];
+ const BYTE* repMatch2 = repIndex2 < dictLimit ?
+ dictBase + repIndex2 : base + repIndex2;
+ if ( (((U32)((dictLimit-1) - repIndex2) >= 3) &
+ (repIndex2 > lowestIndex)) /* intentional overflow */
+ && (MEM_read32(repMatch2) == MEM_read32(ip)) ) {
+ const BYTE* const repEnd2 = repIndex2 < dictLimit ?
+ dictEnd : iend;
+ size_t const repLength2 =
+ ZSTD_count_2segments(ip+4, repMatch2+4, iend,
+ repEnd2, lowPrefixPtr) + 4;
+
+ U32 tmpOffset = repToConfirm[1];
+ repToConfirm[1] = repToConfirm[0];
+ repToConfirm[0] = tmpOffset;
+
+ ZSTD_storeSeq(seqStorePtr, 0, anchor, 0, repLength2-MINMATCH);
+
+ /* Fill the hash table from lastHashed+1 to ip+repLength2*/
+ if (ip + repLength2 < ilimit) {
+ rollingHash = ZSTD_ldm_fillLdmHashTable(
+ ldmState, rollingHash, lastHashed,
+ ip + repLength2, base, hBits,
+ ldmParams);
+ lastHashed = ip + repLength2 - 1;
+ }
+ ip += repLength2;
+ anchor = ip;
+ continue;
+ }
+ break;
+ }
+ }
+
+ /* Overwrite rep */
+ for (i = 0; i < ZSTD_REP_NUM; i++)
+ seqStorePtr->rep[i] = repToConfirm[i];
+
+ ZSTD_ldm_limitTableUpdate(ctx, anchor);
+ ZSTD_ldm_fillFastTables(ctx, anchor);
+
+ /* Call the block compressor one last time on the last literals */
+ lastLiterals = blockCompressor(ctx, anchor, iend - anchor);
+ ctx->nextToUpdate = (U32)(iend - base);
+
+ /* Restore seqStorePtr->rep */
+ for (i = 0; i < ZSTD_REP_NUM; i++)
+ seqStorePtr->rep[i] = savedRep[i];
+
+ /* Return the last literals size */
+ return lastLiterals;
+}
+
+size_t ZSTD_compressBlock_ldm_extDict(ZSTD_CCtx* ctx,
+ const void* src, size_t srcSize)
+{
+ return ZSTD_compressBlock_ldm_extDict_generic(ctx, src, srcSize);
+}
projects / thirdparty / zstd.git / commitdiff
