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Fix undefined behavior when srcSize==1

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This commit is contained in:
Stella Lau 2017-08-22 11:55:42 -07:00
parent 78c3d16bf4
commit e50ed1fa3a
3 changed files with 37 additions and 30 deletions
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33
lib/common/bitstream.h
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@ -169,25 +169,28 @@ MEM_STATIC size_t BIT_readBitsFast(BIT_DStream_t* bitD, unsigned nbBits);
****************************************************************/
MEM_STATIC unsigned BIT_highbit32 (register U32 val)
{
assert(val != 0);
{
# if defined(_MSC_VER) /* Visual */
unsigned long r=0;
_BitScanReverse ( &r, val );
return (unsigned) r;
unsigned long r=0;
_BitScanReverse ( &r, val );
return (unsigned) r;
# elif defined(__GNUC__) && (__GNUC__ >= 3) /* Use GCC Intrinsic */
return 31 - __builtin_clz (val);
return 31 - __builtin_clz (val);
# else /* Software version */
static const unsigned DeBruijnClz[32] = { 0, 9, 1, 10, 13, 21, 2, 29,
11, 14, 16, 18, 22, 25, 3, 30,
8, 12, 20, 28, 15, 17, 24, 7,
19, 27, 23, 6, 26, 5, 4, 31 };
U32 v = val;
v |= v >> 1;
v |= v >> 2;
v |= v >> 4;
v |= v >> 8;
v |= v >> 16;
return DeBruijnClz[ (U32) (v * 0x07C4ACDDU) >> 27];
static const unsigned DeBruijnClz[32] = { 0, 9, 1, 10, 13, 21, 2, 29,
11, 14, 16, 18, 22, 25, 3, 30,
8, 12, 20, 28, 15, 17, 24, 7,
19, 27, 23, 6, 26, 5, 4, 31 };
U32 v = val;
v |= v >> 1;
v |= v >> 2;
v |= v >> 4;
v |= v >> 8;
v |= v >> 16;
return DeBruijnClz[ (U32) (v * 0x07C4ACDDU) >> 27];
# endif
}
}
/*===== Local Constants =====*/

31
lib/common/zstd_internal.h
View File

@ -268,24 +268,27 @@ void ZSTD_free(void* ptr, ZSTD_customMem customMem);
MEM_STATIC U32 ZSTD_highbit32(U32 val)
{
assert(val != 0);
{
# if defined(_MSC_VER) /* Visual */
unsigned long r=0;
_BitScanReverse(&r, val);
return (unsigned)r;
unsigned long r=0;
_BitScanReverse(&r, val);
return (unsigned)r;
# elif defined(__GNUC__) && (__GNUC__ >= 3) /* GCC Intrinsic */
return 31 - __builtin_clz(val);
return 31 - __builtin_clz(val);
# else /* Software version */
static const int DeBruijnClz[32] = { 0, 9, 1, 10, 13, 21, 2, 29, 11, 14, 16, 18, 22, 25, 3, 30, 8, 12, 20, 28, 15, 17, 24, 7, 19, 27, 23, 6, 26, 5, 4, 31 };
U32 v = val;
int r;
v |= v >> 1;
v |= v >> 2;
v |= v >> 4;
v |= v >> 8;
v |= v >> 16;
r = DeBruijnClz[(U32)(v * 0x07C4ACDDU) >> 27];
return r;
static const int DeBruijnClz[32] = { 0, 9, 1, 10, 13, 21, 2, 29, 11, 14, 16, 18, 22, 25, 3, 30, 8, 12, 20, 28, 15, 17, 24, 7, 19, 27, 23, 6, 26, 5, 4, 31 };
U32 v = val;
int r;
v |= v >> 1;
v |= v >> 2;
v |= v >> 4;
v |= v >> 8;
v |= v >> 16;
r = DeBruijnClz[(U32)(v * 0x07C4ACDDU) >> 27];
return r;
# endif
}
}

3
lib/compress/zstd_compress.c
View File

@ -497,7 +497,8 @@ ZSTD_compressionParameters ZSTD_adjustCParams_internal(ZSTD_compressionParameter
{ U32 const minSrcSize = (srcSize==0) ? 500 : 0;
U64 const rSize = srcSize + dictSize + minSrcSize;
if (rSize < ((U64)1<<ZSTD_WINDOWLOG_MAX)) {
U32 const srcLog = MAX(ZSTD_HASHLOG_MIN, ZSTD_highbit32((U32)(rSize)-1) + 1);
U32 const srcLog =
MAX(ZSTD_HASHLOG_MIN, (rSize==1) ? 1 : ZSTD_highbit32((U32)(rSize)-1) + 1);
if (cPar.windowLog > srcLog) cPar.windowLog = srcLog;
} }
if (cPar.hashLog > cPar.windowLog) cPar.hashLog = cPar.windowLog;