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Overhaul repcode handling logic

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This commit is contained in:
senhuang42 2020-11-12 10:59:35 -05:00
parent 69b8361b0c
commit 4d4fd2c55f
1 changed files with 46 additions and 14 deletions
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60
lib/compress/zstd_compress.c
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@ -2498,14 +2498,20 @@ static void ZSTD_copyBlockSequences(ZSTD_CCtx* zc)
ZSTD_Sequence* outSeqs = &zc->seqCollector.seqStart[zc->seqCollector.seqIndex];
size_t i;
int repIdx;
U32 rep[ZSTD_REP_NUM];
U32 shouldUpdateRep;
assert(zc->seqCollector.seqIndex + 1 < zc->seqCollector.maxSequences);
/* Ensure we have enough space for last literals "sequence" */
assert(zc->seqCollector.maxSequences >= seqStoreSeqSize + 1);
ZSTD_memcpy(rep, repStartValue, ZSTD_REP_NUM * sizeof(U32));
for (i = 0; i < seqStoreSeqSize; ++i) {
U32 rawOffset = seqStoreSeqs[i].offset - ZSTD_REP_NUM;
outSeqs[i].litLength = seqStoreSeqs[i].litLength;
outSeqs[i].matchLength = seqStoreSeqs[i].matchLength + MINMATCH;
outSeqs[i].rep = 0;
shouldUpdateRep = 1;
if (i == seqStore->longLengthPos) {
if (seqStore->longLengthID == 1) {
@ -2515,24 +2521,50 @@ static void ZSTD_copyBlockSequences(ZSTD_CCtx* zc)
}
}
/* Derive the correct offset from the repcode in seqStore_t */
if (seqStoreSeqs[i].offset <= ZSTD_REP_NUM) {
outSeqs[i].rep = seqStoreSeqs[i].offset;
repIdx = (unsigned int)i - seqStoreSeqs[i].offset;
if (seqStoreSeqs[i].litLength == 0) {
if (seqStoreSeqs[i].offset < 3) {
--repIdx;
} else {
repIdx = (unsigned int)i - 1;
if (seqStoreSeqs[i].litLength != 0) {
if (seqStoreSeqs[i].offset == 1) {
shouldUpdateRep = 0;
rawOffset = rep[0];
} else if (seqStoreSeqs[i].offset == 2) {
U32 tmp;
rawOffset = rep[1];
/* Swap ranks of rep[0] and rep[1] */
tmp = rep[0];
rep[0] = rep[1];
rep[1] = tmp;
shouldUpdateRep = 0;
} else if (seqStoreSeqs[i].offset == 3) {
rawOffset = rep[2];
}
outSeqs[i].rep = seqStoreSeqs[i].offset;
} else {
/* Litlength == 0 is a special case for repcode handling */
if (seqStoreSeqs[i].offset == 1) {
U32 tmp;
outSeqs[i].rep = 1;
rawOffset = rep[1];
/* Swap ranks of rep[0] and rep[1] */
tmp = rep[0];
rep[0] = rep[1];
rep[1] = tmp;
shouldUpdateRep = 0;
} else if (seqStoreSeqs[i].offset == 2) {
outSeqs[i].rep = 2;
rawOffset = rep[2];
} else if (seqStoreSeqs[i].offset == 3) {
outSeqs[i].rep = 1;
rawOffset = rep[0] - 1;
}
}
assert(repIdx >= -3);
outSeqs[i].offset = repIdx >= 0 ? outSeqs[repIdx].offset : repStartValue[-repIdx - 1];
if (outSeqs[i].rep == 3 && outSeqs[i].litLength == 0) {
--outSeqs[i].offset;
}
outSeqs[i].offset = rawOffset;
if (shouldUpdateRep) {
for (int i = ZSTD_REP_NUM - 1; i > 0; i--) {
rep[i] = rep[i - 1];
}
} else {
outSeqs[i].offset = seqStoreSeqs[i].offset - ZSTD_REP_NUM;
rep[0] = outSeqs[i].offset;
}
literalsRead += outSeqs[i].litLength;
}