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Split block compresser out of long range matcher

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* `ZSTD_ldm_generateSequences()` generates the LDM sequences and
  stores them in a table. It should work with any chunk size, but
  is currently only called one block at a time.
* `ZSTD_ldm_blockCompress()` emits the pre-defined sequences, and
  instead of encoding the literals directly, it passes them to a
  secondary block compressor. The code to handle chunk sizes greater
  than the block size is currently commented out, since it is unused.
  The next PR will uncomment exercise this code.
* During optimal parsing, ensure LDM `minMatchLength` is at least
  `targetLength`. Also don't emit repcode matches in the LDM block
  compressor. Enabling the LDM with the optimal parser now actually improves
  the compression ratio.
* The compression ratio is very similar to before. It is very slightly
  different, because the repcode handling is slightly different. If I remove
  immediate repcode checking in both branches the compressed size is exactly
  the same.
* The speed looks to be the same or better than before.

Up Next (in a separate PR)
--------------------------

Allow sequence generation to happen prior to compression, and produce more
than a block worth of sequences. Expose some API for zstdmt to consume.
This will test out some currently untested code in
`ZSTD_ldm_blockCompress()`.
This commit is contained in:
Nick Terrell 2018-02-20 19:34:43 -08:00
parent 4d6632c8f3
commit af866b3a58
5 changed files with 343 additions and 321 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
lib/common/zstd_internal.h
View File

@ -213,6 +213,12 @@ MEM_STATIC void ZSTD_wildcopy_e(void* dst, const void* src, void* dstEnd) /* s
/*-*******************************************
* Private declarations
*********************************************/
typedef struct rawSeq_s {
U32 offset;
U32 litLength;
U32 matchLength;
} rawSeq;
typedef struct seqDef_s {
U32 offset;
U16 litLength;

51
lib/compress/zstd_compress.c
View File

@ -718,12 +718,11 @@ size_t ZSTD_estimateCCtxSize_usingCCtxParams(const ZSTD_CCtx_params* params)
size_t const blockStateSpace = 2 * sizeof(ZSTD_compressedBlockState_t);
size_t const matchStateSize = ZSTD_sizeof_matchState(&params->cParams, /* forCCtx */ 1);
size_t const ldmSpace = params->ldmParams.enableLdm ?
ZSTD_ldm_getTableSize(params->ldmParams.hashLog,
params->ldmParams.bucketSizeLog) : 0;
size_t const ldmSpace = ZSTD_ldm_getTableSize(params->ldmParams);
size_t const ldmSeqSpace = ZSTD_ldm_getMaxNbSeq(params->ldmParams, blockSize) * sizeof(rawSeq);
size_t const neededSpace = entropySpace + blockStateSpace + tokenSpace +
matchStateSize + ldmSpace;
matchStateSize + ldmSpace + ldmSeqSpace;
DEBUGLOG(5, "sizeof(ZSTD_CCtx) : %u", (U32)sizeof(ZSTD_CCtx));
DEBUGLOG(5, "estimate workSpace : %u", (U32)neededSpace);
@ -990,7 +989,7 @@ static size_t ZSTD_resetCCtx_internal(ZSTD_CCtx* zc,
if (params.ldmParams.enableLdm) {
/* Adjust long distance matching parameters */
ZSTD_ldm_adjustParameters(&params.ldmParams, params.cParams.windowLog);
ZSTD_ldm_adjustParameters(&params.ldmParams, &params.cParams);
assert(params.ldmParams.hashLog >= params.ldmParams.bucketSizeLog);
assert(params.ldmParams.hashEveryLog < 32);
zc->ldmState.hashPower =
@ -1005,17 +1004,19 @@ static size_t ZSTD_resetCCtx_internal(ZSTD_CCtx* zc,
size_t const buffOutSize = (zbuff==ZSTDb_buffered) ? ZSTD_compressBound(blockSize)+1 : 0;
size_t const buffInSize = (zbuff==ZSTDb_buffered) ? windowSize + blockSize : 0;
size_t const matchStateSize = ZSTD_sizeof_matchState(&params.cParams, /* forCCtx */ 1);
size_t const maxNbLdmSeq = ZSTD_ldm_getMaxNbSeq(params.ldmParams, blockSize);
void* ptr;
/* Check if workSpace is large enough, alloc a new one if needed */
{ size_t const entropySpace = HUF_WORKSPACE_SIZE;
size_t const blockStateSpace = 2 * sizeof(ZSTD_compressedBlockState_t);
size_t const bufferSpace = buffInSize + buffOutSize;
size_t const ldmSpace = params.ldmParams.enableLdm
? ZSTD_ldm_getTableSize(params.ldmParams.hashLog, params.ldmParams.bucketSizeLog)
: 0;
size_t const ldmSpace = ZSTD_ldm_getTableSize(params.ldmParams);
size_t const ldmSeqSpace = maxNbLdmSeq * sizeof(rawSeq);
size_t const neededSpace = entropySpace + blockStateSpace + ldmSpace +
matchStateSize + tokenSpace + bufferSpace;
ldmSeqSpace + matchStateSize + tokenSpace +
bufferSpace;
DEBUGLOG(4, "Need %uKB workspace, including %uKB for match state, and %uKB for buffers",
(U32)(neededSpace>>10), (U32)(matchStateSize>>10), (U32)(bufferSpace>>10));
DEBUGLOG(4, "windowSize: %u - blockSize: %u", (U32)windowSize, (U32)blockSize);
@ -1070,7 +1071,10 @@ static size_t ZSTD_resetCCtx_internal(ZSTD_CCtx* zc,
assert(((size_t)ptr & 3) == 0); /* ensure ptr is properly aligned */
zc->ldmState.hashTable = (ldmEntry_t*)ptr;
ptr = zc->ldmState.hashTable + ldmHSize;
zc->ldmSequences = (rawSeq*)ptr;
ptr = zc->ldmSequences + maxNbLdmSeq;
}
assert(((size_t)ptr & 3) == 0); /* ensure ptr is properly aligned */
ptr = ZSTD_reset_matchState(&zc->blockState.matchState, ptr, &params.cParams, crp, /* forCCtx */ 1);
@ -1820,34 +1824,39 @@ static size_t ZSTD_compressBlock_internal(ZSTD_CCtx* zc,
void* dst, size_t dstCapacity,
const void* src, size_t srcSize)
{
ZSTD_matchState_t* const ms = &zc->blockState.matchState;
DEBUGLOG(5, "ZSTD_compressBlock_internal (dstCapacity=%u, dictLimit=%u, nextToUpdate=%u)",
(U32)dstCapacity, zc->blockState.matchState.dictLimit, zc->blockState.matchState.nextToUpdate);
(U32)dstCapacity, ms->dictLimit, ms->nextToUpdate);
if (srcSize < MIN_CBLOCK_SIZE+ZSTD_blockHeaderSize+1)
return 0; /* don't even attempt compression below a certain srcSize */
ZSTD_resetSeqStore(&(zc->seqStore));
/* limited update after a very long match */
{ const BYTE* const base = zc->blockState.matchState.base;
{ const BYTE* const base = ms->base;
const BYTE* const istart = (const BYTE*)src;
const U32 current = (U32)(istart-base);
if (current > zc->blockState.matchState.nextToUpdate + 384)
zc->blockState.matchState.nextToUpdate = current - MIN(192, (U32)(current - zc->blockState.matchState.nextToUpdate - 384));
if (current > ms->nextToUpdate + 384)
ms->nextToUpdate = current - MIN(192, (U32)(current - ms->nextToUpdate - 384));
}
/* select and store sequences */
{ U32 const extDict = zc->blockState.matchState.lowLimit < zc->blockState.matchState.dictLimit;
{ U32 const extDict = ms->lowLimit < ms->dictLimit;
size_t lastLLSize;
{ int i; for (i = 0; i < ZSTD_REP_NUM; ++i) zc->blockState.nextCBlock->rep[i] = zc->blockState.prevCBlock->rep[i]; }
if (zc->appliedParams.ldmParams.enableLdm) {
typedef size_t (*ZSTD_ldmBlockCompressor)(
ldmState_t* ldms, ZSTD_matchState_t* ms, seqStore_t* seqStore,
U32 rep[ZSTD_REP_NUM], ZSTD_CCtx_params const* params,
void const* src, size_t srcSize);
ZSTD_ldmBlockCompressor const ldmBlockCompressor = extDict ? ZSTD_compressBlock_ldm_extDict : ZSTD_compressBlock_ldm;
lastLLSize = ldmBlockCompressor(&zc->ldmState, &zc->blockState.matchState, &zc->seqStore, zc->blockState.nextCBlock->rep, &zc->appliedParams, src, srcSize);
size_t const nbSeq =
ZSTD_ldm_generateSequences(&zc->ldmState, zc->ldmSequences,
ms, &zc->appliedParams.ldmParams,
src, srcSize, extDict);
lastLLSize =
ZSTD_ldm_blockCompress(zc->ldmSequences, nbSeq,
ms, &zc->seqStore,
zc->blockState.nextCBlock->rep,
&zc->appliedParams.cParams,
src, srcSize, extDict);
} else { /* not long range mode */
ZSTD_blockCompressor const blockCompressor = ZSTD_selectBlockCompressor(zc->appliedParams.cParams.strategy, extDict);
lastLLSize = blockCompressor(&zc->blockState.matchState, &zc->seqStore, zc->blockState.nextCBlock->rep, &zc->appliedParams.cParams, src, srcSize);
lastLLSize = blockCompressor(ms, &zc->seqStore, zc->blockState.nextCBlock->rep, &zc->appliedParams.cParams, src, srcSize);
}
{ const BYTE* const lastLiterals = (const BYTE*)src + srcSize - lastLLSize;
ZSTD_storeLastLiterals(&zc->seqStore, lastLiterals, lastLLSize);

1
lib/compress/zstd_compress_internal.h
View File

@ -186,6 +186,7 @@ struct ZSTD_CCtx_s {
seqStore_t seqStore; /* sequences storage ptrs */
ldmState_t ldmState; /* long distance matching state */
rawSeq* ldmSequences; /* Storage for the ldm output sequences */
ZSTD_blockState_t blockState;
U32* entropyWorkspace; /* entropy workspace of HUF_WORKSPACE_SIZE bytes */

537
lib/compress/zstd_ldm.c
View File

@ -28,8 +28,17 @@ size_t ZSTD_ldm_initializeParameters(ldmParams_t* params, U32 enableLdm)
return 0;
}
void ZSTD_ldm_adjustParameters(ldmParams_t* params, U32 windowLog)
void ZSTD_ldm_adjustParameters(ldmParams_t* params,
ZSTD_compressionParameters const* cParams)
{
U32 const windowLog = cParams->windowLog;
if (cParams->strategy >= ZSTD_btopt) {
/* Get out of the way of the optimal parser */
U32 const minMatch = MAX(cParams->targetLength, params->minMatchLength);
assert(minMatch >= ZSTD_LDM_MINMATCH_MIN);
assert(minMatch <= ZSTD_LDM_MINMATCH_MAX);
params->minMatchLength = minMatch;
}
if (params->hashLog == 0) {
params->hashLog = MAX(ZSTD_HASHLOG_MIN, windowLog - LDM_HASH_RLOG);
assert(params->hashLog <= ZSTD_HASHLOG_MAX);
@ -41,12 +50,19 @@ void ZSTD_ldm_adjustParameters(ldmParams_t* params, U32 windowLog)
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 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) << (hashLog - ldmBucketSizeLog);
return ldmBucketSize + (ldmHSize * (sizeof(ldmEntry_t)));
((size_t)1) << (params.hashLog - ldmBucketSizeLog);
size_t const totalSize = ldmBucketSize + ldmHSize * sizeof(ldmEntry_t);
return params.enableLdm ? totalSize : 0;
}
size_t ZSTD_ldm_getMaxNbSeq(ldmParams_t params, size_t maxChunkSize)
{
return params.enableLdm ? (maxChunkSize / params.minMatchLength) : 0;
}
/** ZSTD_ldm_getSmallHash() :
@ -278,50 +294,54 @@ static void ZSTD_ldm_limitTableUpdate(ZSTD_matchState_t* ms, const BYTE* anchor)
}
}
size_t ZSTD_compressBlock_ldm(
ldmState_t* ldmState, ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
ZSTD_CCtx_params const* params, void const* src, size_t srcSize)
size_t ZSTD_ldm_generateSequences(
ldmState_t* ldmState, rawSeq* sequences, ZSTD_matchState_t const* ms,
ldmParams_t const* params, void const* src, size_t srcSize,
int const extDict)
{
ZSTD_compressionParameters const* cParams = &params->cParams;
const ldmParams_t ldmParams = params->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;
const BYTE* const base = ms->base;
const BYTE* const istart = (const BYTE*)src;
const BYTE* ip = istart;
const BYTE* anchor = istart;
const U32 lowestIndex = ms->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(cParams->strategy, 0);
rawSeq const* const sequencesStart = sequences;
/* LDM parameters */
U32 const minMatchLength = params->minMatchLength;
U64 const hashPower = ldmState->hashPower;
U32 const hBits = params->hashLog - params->bucketSizeLog;
U32 const ldmBucketSize = 1U << params->bucketSizeLog;
U32 const hashEveryLog = params->hashEveryLog;
U32 const ldmTagMask = (1U << params->hashEveryLog) - 1;
/* Prefix and extDict parameters */
U32 const dictLimit = ms->dictLimit;
U32 const lowestIndex = extDict ? ms->lowLimit : dictLimit;
BYTE const* const base = ms->base;
BYTE const* const dictBase = extDict ? ms->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 - MAX(minMatchLength, HASH_READ_SIZE);
/* Input positions */
BYTE const* anchor = istart;
BYTE const* ip = istart;
/* Rolling hash */
BYTE const* lastHashed = NULL;
U64 rollingHash = 0;
const BYTE* lastHashed = NULL;
size_t i, lastLiterals;
/* Main Search Loop */
while (ip < ilimit) { /* < instead of <=, because repcode check at (ip+1) */
while (ip <= ilimit) {
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],
lastHashed[minMatchLength],
hashPower);
} else {
rollingHash = ZSTD_ldm_getRollingHash(ip, ldmParams.minMatchLength);
rollingHash = ZSTD_ldm_getRollingHash(ip, minMatchLength);
}
lastHashed = ip;
/* Do not insert and do not look for a match */
if (ZSTD_ldm_getTag(rollingHash, hBits, ldmParams.hashEveryLog) !=
ldmTagMask) {
if (ZSTD_ldm_getTag(rollingHash, hBits, hashEveryLog) != ldmTagMask) {
ip++;
continue;
}
@ -331,27 +351,49 @@ size_t ZSTD_compressBlock_ldm(
ldmEntry_t* const bucket =
ZSTD_ldm_getBucket(ldmState,
ZSTD_ldm_getSmallHash(rollingHash, hBits),
ldmParams);
*params);
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;
}
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(ip, pMatch, iend);
if (curForwardMatchLength < ldmParams.minMatchLength) {
continue;
curForwardMatchLength = ZSTD_count_2segments(
ip, pMatch, iend,
matchEnd, lowPrefixPtr);
if (curForwardMatchLength < minMatchLength) {
continue;
}
curBackwardMatchLength =
ZSTD_ldm_countBackwardsMatch(ip, anchor, pMatch,
lowMatchPtr);
curTotalMatchLength = curForwardMatchLength +
curBackwardMatchLength;
} else { /* !extDict */
BYTE const* const pMatch = base + cur->offset;
curForwardMatchLength = ZSTD_count(ip, pMatch, iend);
if (curForwardMatchLength < minMatchLength) {
continue;
}
curBackwardMatchLength =
ZSTD_ldm_countBackwardsMatch(ip, anchor, pMatch,
lowPrefixPtr);
curTotalMatchLength = curForwardMatchLength +
curBackwardMatchLength;
}
curBackwardMatchLength = ZSTD_ldm_countBackwardsMatch(
ip, anchor, pMatch, lowest);
curTotalMatchLength = curForwardMatchLength +
curBackwardMatchLength;
if (curTotalMatchLength > bestMatchLength) {
bestMatchLength = curTotalMatchLength;
@ -366,7 +408,7 @@ size_t ZSTD_compressBlock_ldm(
if (bestEntry == NULL) {
ZSTD_ldm_makeEntryAndInsertByTag(ldmState, rollingHash,
hBits, current,
ldmParams);
*params);
ip++;
continue;
}
@ -375,280 +417,217 @@ size_t ZSTD_compressBlock_ldm(
mLength = forwardMatchLength + backwardMatchLength;
ip -= backwardMatchLength;
/* Call the block compressor on the remaining literals */
{
/* Store the sequence:
* ip = current - backwardMatchLength
* The match is at (bestEntry->offset - backwardMatchLength)
*/
U32 const matchIndex = bestEntry->offset;
const BYTE* const match = base + matchIndex - backwardMatchLength;
U32 const offset = (U32)(ip - match);
U32 const offset = current - matchIndex;
/* Fill tables for block compressor */
ZSTD_ldm_limitTableUpdate(ms, anchor);
ZSTD_ldm_fillFastTables(ms, cParams, anchor);
/* Call block compressor and get remaining literals */
lastLiterals = blockCompressor(ms, seqStore, rep, cParams, anchor, ip - anchor);
ms->nextToUpdate = (U32)(ip - base);
/* Update repToConfirm with the new offset */
for (i = ZSTD_REP_NUM - 1; i > 0; i--)
rep[i] = rep[i-1];
rep[0] = offset;
/* Store the sequence with the leftover literals */
ZSTD_storeSeq(seqStore, lastLiterals, ip - lastLiterals,
offset + ZSTD_REP_MOVE, mLength - MINMATCH);
sequences->litLength = (U32)(ip - anchor);
sequences->matchLength = (U32)mLength;
sequences->offset = offset;
++sequences;
}
/* Insert the current entry into the hash table */
ZSTD_ldm_makeEntryAndInsertByTag(ldmState, rollingHash, hBits,
(U32)(lastHashed - base),
ldmParams);
*params);
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) {
if (ip + mLength <= ilimit) {
rollingHash = ZSTD_ldm_fillLdmHashTable(
ldmState, rollingHash, lastHashed,
ip + mLength, base, hBits, ldmParams);
ip + mLength, base, hBits, *params);
lastHashed = ip + mLength - 1;
}
ip += mLength;
anchor = ip;
/* Check immediate repcode */
while ( (ip < ilimit)
&& ( (rep[1] > 0) && (rep[1] <= (U32)(ip-lowest))
&& (MEM_read32(ip) == MEM_read32(ip - rep[1])) )) {
size_t const rLength = ZSTD_count(ip+4, ip+4-rep[1],
iend) + 4;
/* Swap repToConfirm[1] <=> repToConfirm[0] */
{
U32 const tmpOff = rep[1];
rep[1] = rep[0];
rep[0] = tmpOff;
}
ZSTD_storeSeq(seqStore, 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;
}
}
ZSTD_ldm_limitTableUpdate(ms, anchor);
ZSTD_ldm_fillFastTables(ms, cParams, anchor);
lastLiterals = blockCompressor(ms, seqStore, rep, cParams, anchor, iend - anchor);
ms->nextToUpdate = (U32)(iend - base);
/* Return the last literals size */
return lastLiterals;
/* Return the number of sequences generated */
return sequences - sequencesStart;
}
size_t ZSTD_compressBlock_ldm_extDict(
ldmState_t* ldmState, ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
ZSTD_CCtx_params const* params, void const* src, size_t srcSize)
#if 0
/**
* If the sequence length is longer than remaining then the sequence is split
* between this block and the next.
*
* Returns the current sequence to handle, or if the rest of the block should
* be literals, it returns a sequence with offset == 0.
*/
static rawSeq maybeSplitSequence(rawSeq* sequences, size_t* nbSeq,
size_t const seq, size_t const remaining,
U32 const minMatch)
{
const ldmParams_t ldmParams = params->ldmParams;
ZSTD_compressionParameters const* cParams = &params->cParams;
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;
const BYTE* const base = ms->base;
const BYTE* const dictBase = ms->dictBase;
const BYTE* const istart = (const BYTE*)src;
const BYTE* ip = istart;
const BYTE* anchor = istart;
const U32 lowestIndex = ms->lowLimit;
const BYTE* const dictStart = dictBase + lowestIndex;
const U32 dictLimit = ms->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);
rawSeq sequence = sequences[seq];
assert(sequence.offset > 0);
/* Handle partial sequences */
if (remaining <= sequence.litLength) {
/* Split the literals that we have out of the sequence.
* They will become the last literals of this block.
* The next block starts off with the remaining literals.
*/
sequences[seq].litLength -= remaining;
*nbSeq = seq;
sequence.offset = 0;
} else if (remaining < sequence.litLength + sequence.matchLength) {
/* Split the match up into two sequences. One in this block, and one
* in the next with no literals. If either match would be shorter
* than searchLength we omit it.
*/
U32 const matchPrefix = remaining - sequence.litLength;
U32 const matchSuffix = sequence.matchLength - matchPrefix;
const ZSTD_blockCompressor blockCompressor =
ZSTD_selectBlockCompressor(cParams->strategy, 1);
U64 rollingHash = 0;
const BYTE* lastHashed = NULL;
size_t i, lastLiterals;
/* 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);
assert(remaining > sequence.litLength);
assert(matchPrefix < sequence.matchLength);
assert(matchPrefix + matchSuffix == sequence.matchLength);
/* Update the current sequence */
sequence.matchLength = matchPrefix;
/* Update the next sequence when long enough, otherwise omit it. */
if (matchSuffix >= minMatch) {
sequences[seq].litLength = 0;
sequences[seq].matchLength = matchSuffix;
*nbSeq = seq;
} else {
rollingHash = ZSTD_ldm_getRollingHash(ip, ldmParams.minMatchLength);
sequences[seq + 1].litLength += matchSuffix;
*nbSeq = seq + 1;
}
lastHashed = ip;
if (ZSTD_ldm_getTag(rollingHash, hBits, ldmParams.hashEveryLog) !=
ldmTagMask) {
/* Don't insert and don't look for a match */
ip++;
continue;
if (sequence.matchLength < minMatch) {
/* Skip the current sequence if it is too short */
sequence.offset = 0;
}
}
return sequence;
}
#endif
/* Get the best entry and compute the match lengths */
size_t ZSTD_ldm_blockCompress(rawSeq const* sequences, size_t nbSeq,
ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
ZSTD_compressionParameters const* cParams, void const* src, size_t srcSize,
int const extDict)
{
ZSTD_blockCompressor const blockCompressor =
ZSTD_selectBlockCompressor(cParams->strategy, extDict);
int const doImmediateRepCheck = cParams->strategy < ZSTD_btopt;
/* Prefix and extDict parameters */
U32 const dictLimit = ms->dictLimit;
U32 const lowestIndex = extDict ? ms->lowLimit : dictLimit;
BYTE const* const base = ms->base;
BYTE const* const dictBase = extDict ? ms->dictBase : 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;
/* Input positions */
BYTE const* ip = istart;
size_t seq;
/* Loop through each sequence and apply the block compressor to the lits */
for (seq = 0; seq < nbSeq; ++seq) {
rawSeq const sequence = sequences[seq];
int i;
if (sequence.offset == 0)
break;
assert(ip + sequence.litLength + sequence.matchLength <= iend);
/* Fill tables for block compressor */
ZSTD_ldm_limitTableUpdate(ms, ip);
ZSTD_ldm_fillFastTables(ms, cParams, ip);
/* Run the block compressor */
{
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;
/* Fill the hash table for the block compressor */
ZSTD_ldm_limitTableUpdate(ms, anchor);
ZSTD_ldm_fillFastTables(ms, cParams, anchor);
/* Call block compressor and get remaining literals */
lastLiterals = blockCompressor(ms, seqStore, rep, cParams, anchor, ip - anchor);
size_t const newLitLength =
blockCompressor(ms, seqStore, rep, cParams, ip,
sequence.litLength);
ip += sequence.litLength;
ms->nextToUpdate = (U32)(ip - base);
/* Update repToConfirm with the new offset */
/* Update the repcodes */
for (i = ZSTD_REP_NUM - 1; i > 0; i--)
rep[i] = rep[i-1];
rep[0] = offset;
/* Store the sequence with the leftover literals */
ZSTD_storeSeq(seqStore, lastLiterals, ip - lastLiterals,
offset + ZSTD_REP_MOVE, mLength - MINMATCH);
rep[0] = sequence.offset;
/* Store the sequence */
ZSTD_storeSeq(seqStore, newLitLength, ip - newLitLength,
sequence.offset + ZSTD_REP_MOVE,
sequence.matchLength - MINMATCH);
ip += sequence.matchLength;
}
/* Check immediate repcode */
if (doImmediateRepCheck) {
rawSeq* nextSeq = (seq + 1 < *nbSeq) ? &sequences[seq + 1] : NULL;
/* Allow repcodes up to the next predefined sequence */
BYTE const* const repCheckEnd = nextSeq
? ip + nextSeq->litLength
: iend;
BYTE const* const repCheckLimit = repCheckEnd - HASH_READ_SIZE;
/* Insert the current entry into the hash table */
ZSTD_ldm_makeEntryAndInsertByTag(ldmState, rollingHash, hBits,
(U32)(lastHashed - base),
ldmParams);
assert(repCheckEnd <= iend);
/* 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;
if (extDict) {
while (ip < repCheckLimit) {
U32 const current = (U32)(ip-base);
U32 const repIndex = current - rep[1];
const BYTE* repMatch = repIndex < dictLimit ?
dictBase + repIndex : base + repIndex;
if ( (((U32)((dictLimit-1) - repIndex) >= 3) &
(repIndex > lowestIndex)) /* intentional overflow */
&& (MEM_read32(repMatch) == MEM_read32(ip)) ) {
const BYTE* const repEnd = repIndex < dictLimit ?
dictEnd : repCheckEnd;
size_t const rLength = ZSTD_count_2segments(
ip+4, repMatch+4, repCheckEnd, repEnd,
lowPrefixPtr) + 4;
/* Swap rep[1] <=> rep[0] */
U32 const tmpOffset = rep[1];
rep[1] = rep[0];
rep[0] = tmpOffset;
/* check immediate repcode */
while (ip < ilimit) {
U32 const current2 = (U32)(ip-base);
U32 const repIndex2 = current2 - rep[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;
ZSTD_storeSeq(seqStore, 0, ip, 0, rLength-MINMATCH);
ip += rLength;
if (nextSeq) {
assert(nextSeq->litLength >= rLength);
nextSeq->litLength -= rLength;
}
continue;
}
break;
}
} else {
while ( (ip < repCheckLimit)
&& ( (rep[1] > 0) && (rep[1] <= (U32)(ip - lowPrefixPtr))
&& (MEM_read32(ip) == MEM_read32(ip - rep[1])) )) {
U32 tmpOffset = rep[1];
rep[1] = rep[0];
rep[0] = tmpOffset;
size_t const rLength = ZSTD_count(ip+4, ip+4-rep[1],
repCheckEnd) + 4;
/* Swap rep[1] <=> rep[0] */
{
U32 const tmpOff = rep[1];
rep[1] = rep[0];
rep[0] = tmpOff;
}
ZSTD_storeSeq(seqStore, 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;
ZSTD_storeSeq(seqStore, 0, ip, 0, rLength-MINMATCH);
ip += rLength;
if (nextSeq) {
assert(nextSeq->litLength >= rLength);
nextSeq->litLength -= rLength;
}
}
ip += repLength2;
anchor = ip;
continue;
}
break;
}
}
ZSTD_ldm_limitTableUpdate(ms, anchor);
ZSTD_ldm_fillFastTables(ms, cParams, anchor);
/* Call the block compressor one last time on the last literals */
lastLiterals = blockCompressor(ms, seqStore, rep, cParams, anchor, iend - anchor);
ms->nextToUpdate = (U32)(iend - base);
/* Return the last literals size */
return lastLiterals;
ZSTD_ldm_limitTableUpdate(ms, ip);
ZSTD_ldm_fillFastTables(ms, cParams, ip);
{
size_t const lastLiterals = blockCompressor(ms, seqStore, rep, cParams,
ip, iend - ip);
ms->nextToUpdate = (U32)(iend - base);
return lastLiterals;
}
}

69
lib/compress/zstd_ldm.h
View File

@ -24,34 +24,57 @@ extern "C" {
#define ZSTD_LDM_DEFAULT_WINDOW_LOG ZSTD_WINDOWLOG_DEFAULTMAX
#define ZSTD_LDM_HASHEVERYLOG_NOTSET 9999
/** ZSTD_compressBlock_ldm_generic() :
/**
* ZSTD_ldm_generateSequences():
*
* This is a block compressor intended for long distance matching.
* Generates the sequences using the long distance match finder.
* The sequences completely parse a prefix of the source, but leave off the last
* literals. Returns the number of sequences generated into `sequences`.
*
* The function searches for matches of length at least
* ldmParams.minMatchLength using a hash table in cctx->ldmState.
* Matches can be at a distance of up to cParams.windowLog.
*
* Upon finding a match, the unmatched literals are compressed using a
* ZSTD_blockCompressor (depending on the strategy in the compression
* parameters), which stores the matched sequences. The "long distance"
* match is then stored with the remaining literals from the
* ZSTD_blockCompressor. */
size_t ZSTD_compressBlock_ldm(
ldmState_t* ldms, ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
ZSTD_CCtx_params const* params, void const* src, size_t srcSize);
* NOTE: The source may be any size, assuming it doesn't overflow the hash table
* indices, and the output sequences table is large enough..
*/
size_t ZSTD_ldm_generateSequences(
ldmState_t* ldms, rawSeq* sequences, ZSTD_matchState_t const* ms,
ldmParams_t const* params, void const* src, size_t srcSize,
int const extDict);
/**
* ZSTD_ldm_blockCompress():
*
* Compresses a block using the predefined sequences, along with a secondary
* block compressor. The literals section of every sequence is passed to the
* secondary block compressor, and those sequences are interspersed with the
* predefined sequences. Returns the length of the last literals.
* `nbSeq` is the number of sequences available in `sequences`.
*
* NOTE: The source must be at most the maximum block size, but the predefined
* sequences can be any size, and may be longer than the block. In the case that
* they are longer than the block, the last sequences may need to be split into
* two. We handle that case correctly, and update `sequences` and `nbSeq`
* appropriately.
*/
size_t ZSTD_ldm_blockCompress(rawSeq const* sequences, size_t nbSeq,
ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
ZSTD_compressionParameters const* cParams, void const* src, size_t srcSize,
int const extDict);
size_t ZSTD_compressBlock_ldm_extDict(
ldmState_t* ldms, ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
ZSTD_CCtx_params const* params, void const* src, size_t srcSize);
/** ZSTD_ldm_initializeParameters() :
* Initialize the long distance matching parameters to their default values. */
size_t ZSTD_ldm_initializeParameters(ldmParams_t* params, U32 enableLdm);
/** ZSTD_ldm_getTableSize() :
* Estimate the space needed for long distance matching tables. */
size_t ZSTD_ldm_getTableSize(U32 hashLog, U32 bucketSizeLog);
* Estimate the space needed for long distance matching tables or 0 if LDM is
* disabled.
*/
size_t ZSTD_ldm_getTableSize(ldmParams_t params);
/** ZSTD_ldm_getSeqSpace() :
* Return an upper bound on the number of sequences that can be produced by
* the long distance matcher, or 0 if LDM is disabled.
*/
size_t ZSTD_ldm_getMaxNbSeq(ldmParams_t params, size_t maxChunkSize);
/** ZSTD_ldm_getTableSize() :
* Return prime8bytes^(minMatchLength-1) */
@ -62,8 +85,12 @@ U64 ZSTD_ldm_getHashPower(U32 minMatchLength);
* windowLog and params->hashLog.
*
* Ensures that params->bucketSizeLog is <= params->hashLog (setting it to
* params->hashLog if it is not). */
void ZSTD_ldm_adjustParameters(ldmParams_t* params, U32 windowLog);
* params->hashLog if it is not).
*
* Ensures that the minMatchLength >= targetLength during optimal parsing.
*/
void ZSTD_ldm_adjustParameters(ldmParams_t* params,
ZSTD_compressionParameters const* cParams);
#if defined (__cplusplus)
}