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Fix ZSTD_countTrailingZeros() bug

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`>> 3` is wrong.
This commit is contained in:
Ma Lin 2021-09-28 09:14:19 +08:00
parent ae986fcdb8
commit 894f05e88d
1 changed files with 7 additions and 7 deletions
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14
lib/common/zstd_internal.h
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@ -385,10 +385,10 @@ MEM_STATIC U32 ZSTD_highbit32(U32 val) /* compress, dictBuilder, decodeCorpus
}
/**
* Computes CTZ on a U64.
* This will be slow on 32-bit mode, and on unsupported compilers.
* If you need this function to be fast (because it is hot) expand
* support.
* Counts the number of trailing zeros of a `size_t`.
* Most compilers should support CTZ as a builtin. A backup
* implementation is provided if the builtin isn't supported, but
* it may not be terribly efficient.
*/
MEM_STATIC unsigned ZSTD_countTrailingZeros(size_t val)
{
@ -400,7 +400,7 @@ MEM_STATIC unsigned ZSTD_countTrailingZeros(size_t val)
if (val != 0) {
unsigned long r;
_BitScanForward64(&r, (U64)val);
return (unsigned)(r >> 3);
return (unsigned)r;
} else {
/* Should not reach this code path */
__assume(0);
@ -424,13 +424,13 @@ MEM_STATIC unsigned ZSTD_countTrailingZeros(size_t val)
if (val != 0) {
unsigned long r;
_BitScanForward(&r, (U32)val);
return (unsigned)(r >> 3);
return (unsigned)r;
} else {
/* Should not reach this code path */
__assume(0);
}
# elif defined(__GNUC__) && (__GNUC__ >= 3)
return (__builtin_ctz((U32)val) >> 3);
return __builtin_ctz((U32)val);
# else
static const int DeBruijnBytePos[32] = { 0, 1, 28, 2, 29, 14, 24, 3,
30, 22, 20, 15, 25, 17, 4, 8,