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Make function descriptions more accurate

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This commit is contained in:
senhuang42 2020-10-01 11:47:35 -04:00
parent 1a687b3fcb
commit 10647924f1
4 changed files with 29 additions and 27 deletions
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2
lib/compress/zstd_compress_internal.h
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@ -82,7 +82,7 @@ typedef struct {
} ZSTD_entropyCTables_t; } ZSTD_entropyCTables_t;
typedef struct { typedef struct {
U32 off; /* Offset code for the match */ U32 off; /* Offset code (offset + ZSTD_REP_MOVE) for the match */
U32 len; /* Raw length of match */ U32 len; /* Raw length of match */
} ZSTD_match_t; } ZSTD_match_t;

3
lib/compress/zstd_ldm.c
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@ -579,8 +579,7 @@ size_t ZSTD_ldm_blockCompress(rawSeqStore_t* rawSeqStore,
size_t lastLLSize; size_t lastLLSize;
ms->ldmSeqStore = *rawSeqStore; ms->ldmSeqStore = *rawSeqStore;
lastLLSize = blockCompressor(ms, seqStore, rep, src, srcSize); lastLLSize = blockCompressor(ms, seqStore, rep, src, srcSize);
/* ldm seqstore will have changed during blockCompressor() call, make sure we copy those changes */ *rawSeqStore = ms->ldmSeqStore; /* Persist changes to ldmSeqStore during blockCompressor() */
*rawSeqStore = ms->ldmSeqStore;
return lastLLSize; return lastLLSize;
} }

49
lib/compress/zstd_opt.c
View File

@ -768,14 +768,13 @@ FORCE_INLINE_TEMPLATE U32 ZSTD_BtGetAllMatches (
* LDM helper functions * LDM helper functions
*********************************/ *********************************/
/* Moves forward in rawSeqStore by nbBytes, which will update the fields /* ldm_moveForwardBytesInSeqStore():
* 'pos' and 'posInSequence' accordingly. * Moves forward in rawSeqStore by nbBytes, which will update the fields 'pos' and 'posInSequence'.
*/ */
static void ldm_moveForwardBytesInSeqStore(rawSeqStore_t* ldmSeqStore, size_t nbBytes) { static void ldm_moveForwardBytesInSeqStore(rawSeqStore_t* ldmSeqStore, size_t nbBytes) {
while (nbBytes && ldmSeqStore->pos < ldmSeqStore->size) { while (nbBytes && ldmSeqStore->pos < ldmSeqStore->size) {
rawSeq currSeq; rawSeq currSeq;
currSeq = ldmSeqStore->seq[ldmSeqStore->pos]; currSeq = ldmSeqStore->seq[ldmSeqStore->pos];
if (nbBytes <= currSeq.litLength) { if (nbBytes <= currSeq.litLength) {
ldmSeqStore->posInSequence += nbBytes; ldmSeqStore->posInSequence += nbBytes;
return; return;
@ -783,7 +782,6 @@ static void ldm_moveForwardBytesInSeqStore(rawSeqStore_t* ldmSeqStore, size_t nb
ldmSeqStore->posInSequence += currSeq.litLength; ldmSeqStore->posInSequence += currSeq.litLength;
nbBytes -= currSeq.litLength; nbBytes -= currSeq.litLength;
} }
if (nbBytes < currSeq.matchLength) { if (nbBytes < currSeq.matchLength) {
ldmSeqStore->posInSequence += nbBytes; ldmSeqStore->posInSequence += nbBytes;
return; return;
@ -797,13 +795,14 @@ static void ldm_moveForwardBytesInSeqStore(rawSeqStore_t* ldmSeqStore, size_t nb
} }
} }
/* Calculates the beginning and end of a match, and updates 'pos' and 'posInSequence' /* ldm_getNextMatchAndUpdateSeqStore():
* of the ldmSeqStore. * Calculates the beginning and end of the next match in the current block.
* Updates 'pos' and 'posInSequence' of the ldmSeqStore.
*/ */
static void ldm_calculateNextMatch(rawSeqStore_t* ldmSeqStore, static void ldm_getNextMatchAndUpdateSeqStore(rawSeqStore_t* ldmSeqStore,
U32* matchStartPosInBlock, U32* matchEndPosInBlock, U32* matchStartPosInBlock, U32* matchEndPosInBlock,
U32* matchOffset, U32 currPosInBlock, U32* matchOffset, U32 currPosInBlock,
U32 blockBytesRemaining) { U32 blockBytesRemaining) {
rawSeq currSeq; rawSeq currSeq;
U32 currBlockEndPos; U32 currBlockEndPos;
U32 literalsBytesRemaining; U32 literalsBytesRemaining;
@ -827,7 +826,7 @@ static void ldm_calculateNextMatch(rawSeqStore_t* ldmSeqStore,
currSeq.matchLength - (ldmSeqStore->posInSequence - currSeq.litLength) : currSeq.matchLength - (ldmSeqStore->posInSequence - currSeq.litLength) :
currSeq.matchLength; currSeq.matchLength;
/* If there are more literal bytes than bytes remaining in block, no ldm */ /* If there are more literal bytes than bytes remaining in block, no ldm is possible */
if (literalsBytesRemaining >= blockBytesRemaining) { if (literalsBytesRemaining >= blockBytesRemaining) {
*matchStartPosInBlock = UINT_MAX; *matchStartPosInBlock = UINT_MAX;
*matchEndPosInBlock = UINT_MAX; *matchEndPosInBlock = UINT_MAX;
@ -852,7 +851,10 @@ static void ldm_calculateNextMatch(rawSeqStore_t* ldmSeqStore,
} }
} }
/* Adds an LDM if it's long enough */ /* ldm_maybeAddLdm():
* Adds a match if it's long enough, based on it's 'matchStartPosInBlock'
* and 'matchEndPosInBlock', into 'matches'. Maintains the correct ordering of 'matches'
*/
static void ldm_maybeAddLdm(ZSTD_match_t* matches, U32* nbMatches, static void ldm_maybeAddLdm(ZSTD_match_t* matches, U32* nbMatches,
U32 matchStartPosInBlock, U32 matchEndPosInBlock, U32 matchStartPosInBlock, U32 matchEndPosInBlock,
U32 matchOffset, U32 currPosInBlock) { U32 matchOffset, U32 currPosInBlock) {
@ -865,7 +867,7 @@ static void ldm_maybeAddLdm(ZSTD_match_t* matches, U32* nbMatches,
if (currPosInBlock < matchStartPosInBlock || if (currPosInBlock < matchStartPosInBlock ||
currPosInBlock >= matchEndPosInBlock || currPosInBlock >= matchEndPosInBlock ||
posDiff > 0 || /* As a next evolution we can enable adding LDMs in the middle of a match */ posDiff > 0 || /* As a next evolution we can enable adding LDMs in the middle of a match */
candidateMatchLength < ZSTD_LDM_MINMATCH_MIN) candidateMatchLength < MINMATCH)
return; return;
if (*nbMatches == 0) { if (*nbMatches == 0) {
@ -879,17 +881,18 @@ static void ldm_maybeAddLdm(ZSTD_match_t* matches, U32* nbMatches,
* the ldm match down as necessary. * the ldm match down as necessary.
*/ */
if (candidateMatchLength == matches[*nbMatches-1].len) { if (candidateMatchLength == matches[*nbMatches-1].len) {
U32 candidateMatchIdx;
if (candidateOffCode == matches[*nbMatches-1].off) { if (candidateOffCode == matches[*nbMatches-1].off) {
/* No need to insert the match if it's the exact same */ /* No need to insert the match if it's the exact same */
return; return;
} }
U32 candidateMatchIdx = *nbMatches; candidateMatchIdx = *nbMatches;
matches[*nbMatches].len = candidateMatchLength; matches[*nbMatches].len = candidateMatchLength;
matches[*nbMatches].off = candidateOffCode; matches[*nbMatches].off = candidateOffCode;
if (candidateOffCode != matches[*nbMatches-1].off) { if (candidateOffCode != matches[*nbMatches-1].off) {
while (candidateMatchIdx > 0 && while (candidateMatchIdx > 0 &&
matches[candidateMatchIdx].off > matches[candidateMatchIdx - 1].off && matches[candidateMatchIdx].off > matches[candidateMatchIdx - 1].off &&
matches[candidateMatchIdx].len == matches[candidateMatchIdx - 1].len) { matches[candidateMatchIdx].len == matches[candidateMatchIdx - 1].len) {
ZSTD_match_t tmp = matches[candidateMatchIdx - 1]; ZSTD_match_t tmp = matches[candidateMatchIdx - 1];
matches[candidateMatchIdx - 1] = matches[candidateMatchIdx]; matches[candidateMatchIdx - 1] = matches[candidateMatchIdx];
matches[candidateMatchIdx] = tmp; matches[candidateMatchIdx] = tmp;
@ -918,9 +921,9 @@ static void ldm_handleLdm(rawSeqStore_t* ldmSeqStore, ZSTD_match_t* matches, U32
U32 posOvershoot = currPosInBlock - *matchEndPosInBlock; U32 posOvershoot = currPosInBlock - *matchEndPosInBlock;
ldm_moveForwardBytesInSeqStore(ldmSeqStore, posOvershoot); ldm_moveForwardBytesInSeqStore(ldmSeqStore, posOvershoot);
} }
ldm_calculateNextMatch(ldmSeqStore, matchStartPosInBlock, ldm_getNextMatchAndUpdateSeqStore(ldmSeqStore, matchStartPosInBlock,
matchEndPosInBlock, matchOffset, matchEndPosInBlock, matchOffset,
currPosInBlock, remainingBytes); currPosInBlock, remainingBytes);
} }
ldm_maybeAddLdm(matches, nbMatches, *matchStartPosInBlock, *matchEndPosInBlock, *matchOffset, currPosInBlock); ldm_maybeAddLdm(matches, nbMatches, *matchStartPosInBlock, *matchEndPosInBlock, *matchOffset, currPosInBlock);
} }
@ -985,9 +988,9 @@ ZSTD_compressBlock_opt_generic(ZSTD_matchState_t* ms,
/* Get first match from ldm seq store if long mode is enabled */ /* Get first match from ldm seq store if long mode is enabled */
if (ms->ldmSeqStore.size > 0 && ms->ldmSeqStore.pos < ms->ldmSeqStore.size) { if (ms->ldmSeqStore.size > 0 && ms->ldmSeqStore.pos < ms->ldmSeqStore.size) {
ldm_calculateNextMatch(&ms->ldmSeqStore, &ldmStartPosInBlock, ldm_getNextMatchAndUpdateSeqStore(&ms->ldmSeqStore, &ldmStartPosInBlock,
&ldmEndPosInBlock, &ldmOffset, &ldmEndPosInBlock, &ldmOffset,
(U32)(ip-istart), (U32)(iend-ip)); (U32)(ip-istart), (U32)(iend-ip));
} }
/* init */ /* init */
@ -1249,7 +1252,7 @@ _shortestPath: /* cur, last_pos, best_mlen, best_off have to be set */
if (ldmEndPosInBlock < srcSize) { if (ldmEndPosInBlock < srcSize) {
/* This can occur if after adding the final match in an ldm seq store within this block, /* This can occur if after adding the final match in an ldm seq store within this block,
ip goes to the end of the block without activating a check for ldm_calculateNextMatch */ ip reaches end of the block without calling ldm_getNextMatchAndUpdateSeqStore() */
ldm_moveForwardBytesInSeqStore(&ms->ldmSeqStore, srcSize - ldmEndPosInBlock); ldm_moveForwardBytesInSeqStore(&ms->ldmSeqStore, srcSize - ldmEndPosInBlock);
} }
/* Return the last literals size */ /* Return the last literals size */