ddidderr/zstd-rs
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long matches support overflow

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This commit is contained in:
Yann Collet
2016-11-29 13:12:24 -08:00
parent 52e136ed3d
commit 4f5350f610
3 changed files with 12 additions and 10 deletions
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lib/decompress/zstd_decompress.c
+8 -6
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@@ -793,8 +793,8 @@ typedef struct {
FSE_DState_t stateOffb;
FSE_DState_t stateML;
size_t prevOffset[ZSTD_REP_NUM];
const BYTE* ptr;
const BYTE* base;
size_t pos;
iPtrDiff gotoDict;
} seqState_t;
@@ -864,15 +864,17 @@ static seq_t ZSTD_decodeSequenceLong(seqState_t* seqState)
if (MEM_32bits() ||
(totalBits > 64 - 7 - (LLFSELog+MLFSELog+OffFSELog)) ) BIT_reloadDStream(&seqState->DStream);
seq.match = seqState->ptr + seq.litLength - seq.offset; /* single memory segment ! */
if (seq.match < seqState->base) seq.match += seqState->gotoDict; /* what if seq.match underflows ? prefetch is a non issue, but match has now a wrong address */
{ size_t const pos = seqState->pos + seq.litLength;
seq.match = seqState->base + pos - seq.offset; /* single memory segment */
if (seq.offset > pos) seq.match += seqState->gotoDict; /* separate memory segment */
seqState->pos = pos + seq.matchLength;
}
/* ANS state update */
FSE_updateState(&seqState->stateLL, &seqState->DStream); /* <= 9 bits */
FSE_updateState(&seqState->stateML, &seqState->DStream); /* <= 9 bits */
if (MEM_32bits()) BIT_reloadDStream(&seqState->DStream); /* <= 18 bits */
FSE_updateState(&seqState->stateOffb, &seqState->DStream); /* <= 8 bits */
seqState->ptr += seq.matchLength + seq.litLength;
return seq;
}
@@ -1042,8 +1044,8 @@ static size_t ZSTD_decompressSequencesLong(
int seqNb;
dctx->fseEntropy = 1;
{ U32 i; for (i=0; i<ZSTD_REP_NUM; i++) seqState.prevOffset[i] = dctx->rep[i]; }
seqState.ptr = op;
seqState.base = base;
seqState.pos = (size_t)(op-base);
seqState.gotoDict = (iPtrDiff)(dictEnd - base);
CHECK_E(BIT_initDStream(&seqState.DStream, ip, iend-ip), corruption_detected);
FSE_initDState(&seqState.stateLL, &seqState.DStream, dctx->LLTptr);
@@ -1194,7 +1196,7 @@ size_t ZSTD_execSequence(BYTE* op,
if (sequence.offset > (size_t)(oLitEnd - base)) {
/* offset beyond prefix */
if (sequence.offset > (size_t)(oLitEnd - vBase)) return ERROR(corruption_detected);
match = dictEnd - (base-match);
match += (dictEnd-base);
if (match + sequence.matchLength <= dictEnd) {
memmove(oLitEnd, match, sequence.matchLength);
return sequenceLength;