ddidderr/zstd-rs
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minor speed improvement

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This commit is contained in:
Yann Collet
2015-10-19 03:12:23 +01:00
parent c7ae9ffde3
commit 4d1a0ef515
1 changed files with 12 additions and 16 deletions
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lib/zstd.c
+12 -16
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@@ -1313,25 +1313,21 @@ static size_t ZSTD_execSequence(BYTE* op,
static const int dec32table[] = {0, 1, 2, 1, 4, 4, 4, 4}; /* added */
static const int dec64table[] = {8, 8, 8, 7, 8, 9,10,11}; /* substracted */
const BYTE* const ostart = op;
const size_t litLength = sequence.litLength; /* for some reason, doing the same with matchLength decreases speed ... */
BYTE* const oMatchEnd = op + litLength + sequence.matchLength; /* risk : address space overflow (32-bits) */
const BYTE* const litEnd = *litPtr + litLength;
BYTE* const oLitEnd = op + sequence.litLength;
BYTE* const oMatchEnd = op + sequence.litLength + sequence.matchLength; /* risk : address space overflow (32-bits) */
BYTE* const oend_8 = oend-8;
const BYTE* const litEnd = *litPtr + sequence.litLength;
/* check */
if (oLitEnd > oend_8) return ERROR(dstSize_tooSmall); /* last match must start at a minimum distance of 8 from oend */
if (oMatchEnd > oend) return ERROR(dstSize_tooSmall); /* overwrite beyond dst buffer */
if (litEnd > litLimit) return ERROR(corruption_detected);
if (litEnd > litLimit) return ERROR(corruption_detected); /* overRead beyond lit buffer */
/* copy Literals */
if (op+litLength > oend-8) /* ZSTD_wildcopy() risks overwrite */
memmove(op, *litPtr, litLength);
else
ZSTD_wildcopy(op, *litPtr, litLength);
op += litLength;
ZSTD_wildcopy(op, *litPtr, sequence.litLength); /* note : oLitEnd <= oend-8 : no risk of overwrite beyond oend */
op = oLitEnd;
*litPtr = litEnd; /* update for next sequence */
/* check : last match must be at a minimum distance of 8 from end of dst buffer */
if (oend-op < 8) return ERROR(dstSize_tooSmall);
/* copy Match */
{
const BYTE* match = op - sequence.offset;
@@ -1356,11 +1352,11 @@ static size_t ZSTD_execSequence(BYTE* op,
if (oMatchEnd > oend-12)
{
if (op < oend-8)
if (op < oend_8)
{
ZSTD_wildcopy(op, match, (oend-8) - op);
match += (oend-8) - op;
op = oend-8;
ZSTD_wildcopy(op, match, oend_8 - op);
match += oend_8 - op;
op = oend_8;
}
while (op < oMatchEnd) *op++ = *match++;
}