ddidderr/zstd-rs
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fix one UB pointer arithmetic in encoder

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Instead of calculating distance between 2 memory objects, which is UB,
we extract the offset from object 1, and transfer it into object 2.
This commit is contained in:
Yann Collet
2017-11-17 13:24:51 -08:00
parent cdade555ee
commit 23767e950a
3 changed files with 16 additions and 18 deletions
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lib/compress/zstd_compress.c
+9 -9
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@@ -1819,17 +1819,21 @@ static size_t ZSTD_compressContinue_internal (ZSTD_CCtx* cctx,
cctx->stage = ZSTDcs_ongoing;
}
if (!srcSize) return fhSize; /* do not generate an empty block if no input */
/* Check if blocks follow each other */
if (src != cctx->nextSrc) {
/* not contiguous */
ptrdiff_t const delta = cctx->nextSrc - ip;
size_t const distanceFromBase = (size_t)(cctx->nextSrc - cctx->base);
cctx->lowLimit = cctx->dictLimit;
cctx->dictLimit = (U32)(cctx->nextSrc - cctx->base);
assert(distanceFromBase == (size_t)(U32)distanceFromBase); /* should never overflow */
cctx->dictLimit = (U32)distanceFromBase;
cctx->dictBase = cctx->base;
cctx->base -= delta;
cctx->base = ip - distanceFromBase;
cctx->nextToUpdate = cctx->dictLimit;
if (cctx->dictLimit - cctx->lowLimit < HASH_READ_SIZE) cctx->lowLimit = cctx->dictLimit; /* too small extDict */
}
cctx->nextSrc = ip + srcSize;
/* if input and dictionary overlap : reduce dictionary (area presumed modified by input) */
if ((ip+srcSize > cctx->dictBase + cctx->lowLimit) & (ip < cctx->dictBase + cctx->dictLimit)) {
@@ -1838,17 +1842,13 @@ static size_t ZSTD_compressContinue_internal (ZSTD_CCtx* cctx,
cctx->lowLimit = lowLimitMax;
}
cctx->nextSrc = ip + srcSize;
if (srcSize) {
size_t const cSize = frame ?
{ size_t const cSize = frame ?
ZSTD_compress_frameChunk (cctx, dst, dstCapacity, src, srcSize, lastFrameChunk) :
ZSTD_compressBlock_internal (cctx, dst, dstCapacity, src, srcSize);
if (ZSTD_isError(cSize)) return cSize;
cctx->consumedSrcSize += srcSize;
return cSize + fhSize;
} else
return fhSize;
}
}
size_t ZSTD_compressContinue (ZSTD_CCtx* cctx,