/*
* 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_RLOG 7
#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 = 0;
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->hashLog == 0) {
params->hashLog = MAX(ZSTD_HASHLOG_MIN, windowLog - LDM_HASH_RLOG);
assert(params->hashLog <= ZSTD_HASHLOG_MAX);
}
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)
{
assert(numTagBits < 32 && hbits <= 32);
if (32 - hbits < numTagBits) {
return hash & (((U32)1 << numTagBits) - 1);
} else {
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]++;
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);
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;
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 - MAX(ldmParams.minMatchLength, HASH_READ_SIZE);
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;
}
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 - MAX(ldmParams.minMatchLength, HASH_READ_SIZE);
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);
}