diff options
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/xxhash.c | 60 |
1 files changed, 41 insertions, 19 deletions
diff --git a/lib/xxhash.c b/lib/xxhash.c index e6fb8f1..a18b978 100644 --- a/lib/xxhash.c +++ b/lib/xxhash.c @@ -35,13 +35,15 @@ You can contact the author at : /************************************** * Tuning parameters **************************************/ -/* Unaligned memory access is automatically enabled for "common" CPU, such as x86. - * For others CPU, the compiler will be more cautious, and insert extra code to ensure aligned access is respected. - * If you know your target CPU supports unaligned memory access, you want to force this option manually to improve performance. - * You can also enable this parameter if you know your input data will always be aligned (boundaries of 4, for U32). +/* XXH_FORCE_DIRECT_UNALIGNED_MEMORY_ACCESS + * Unaligned memory access is automatically enabled for "common" CPU, such as x86/x64. + * For others CPU, the compiler will be more cautious, and insert extra code to ensure proper working with unaligned memory accesses. + * If you know your target CPU efficiently supports unaligned memory accesses, you can force this option manually. + * If your CPU efficiently supports unaligned memory accesses and the compiler did not automatically detected it, you will witness large performance improvement. + * You can also enable this switch from compilation command line / Makefile. */ -#if defined(__ARM_FEATURE_UNALIGNED) || defined(__i386) || defined(_M_IX86) || defined(__x86_64__) || defined(_M_X64) -# define XXH_USE_UNALIGNED_ACCESS 1 +#if !defined(XXH_FORCE_DIRECT_MEMORY_ACCESS) && ( defined(__ARM_FEATURE_UNALIGNED) ) +# define XXH_FORCE_DIRECT_MEMORY_ACCESS 1 #endif /* XXH_ACCEPT_NULL_INPUT_POINTER : @@ -61,6 +63,15 @@ You can contact the author at : */ #define XXH_FORCE_NATIVE_FORMAT 0 +/* XXH_USELESS_ALIGN_BRANCH : + * This is a minor performance trick, only useful with lots of very small keys. + * It means : don't make a test between aligned/unaligned, because performance will be the same. + * It avoids one initial branch per hash. + */ +#if defined(__i386) || defined(_M_IX86) || defined(__x86_64__) || defined(_M_X64) || defined(XXH_FORCE_DIRECT_MEMORY_ACCESS) +# define XXH_USELESS_ALIGN_BRANCH 1 +#endif + /************************************** * Compiler Specific Options @@ -113,20 +124,29 @@ static void* XXH_memcpy(void* dest, const void* src, size_t size) { return memcp typedef unsigned long long U64; #endif + +#if defined(XXH_FORCE_DIRECT_MEMORY_ACCESS) + +static U32 XXH_read32(const void* memPtr) { return *(const U32*) memPtr; } +static U64 XXH_read64(const void* memPtr) { return *(const U64*) memPtr; } + +#else + static U32 XXH_read32(const void* memPtr) { - U32 val32; - memcpy(&val32, memPtr, 4); - return val32; + U32 val; + memcpy(&val, memPtr, sizeof(val)); + return val; } static U64 XXH_read64(const void* memPtr) { - U64 val64; - memcpy(&val64, memPtr, 8); - return val64; + U64 val; + memcpy(&val, memPtr, sizeof(val)); + return val; } +#endif // defined /****************************************** @@ -175,8 +195,10 @@ static U64 XXH_swap64 (U64 x) * Architecture Macros ***************************************/ typedef enum { XXH_bigEndian=0, XXH_littleEndian=1 } XXH_endianess; -#ifndef XXH_CPU_LITTLE_ENDIAN /* XXH_CPU_LITTLE_ENDIAN can be defined externally, for example using a compiler switch */ -static const int one = 1; + +/* XXH_CPU_LITTLE_ENDIAN can be defined externally, for example one the compiler command line */ +#ifndef XXH_CPU_LITTLE_ENDIAN + static const int one = 1; # define XXH_CPU_LITTLE_ENDIAN (*(const char*)(&one)) #endif @@ -315,7 +337,7 @@ FORCE_INLINE U32 XXH32_endian_align(const void* input, size_t len, U32 seed, XXH } -unsigned XXH32 (const void* input, size_t len, unsigned seed) +unsigned int XXH32 (const void* input, size_t len, unsigned int seed) { #if 0 /* Simple version, good for code maintenance, but unfortunately slow for small inputs */ @@ -326,7 +348,7 @@ unsigned XXH32 (const void* input, size_t len, unsigned seed) #else XXH_endianess endian_detected = (XXH_endianess)XXH_CPU_LITTLE_ENDIAN; -# if !defined(XXH_USE_UNALIGNED_ACCESS) +# if !defined(XXH_USELESS_ALIGN_BRANCH) if ((((size_t)input) & 3) == 0) /* Input is 4-bytes aligned, leverage the speed benefit */ { if ((endian_detected==XXH_littleEndian) || XXH_FORCE_NATIVE_FORMAT) @@ -466,7 +488,7 @@ unsigned long long XXH64 (const void* input, size_t len, unsigned long long seed #else XXH_endianess endian_detected = (XXH_endianess)XXH_CPU_LITTLE_ENDIAN; -# if !defined(XXH_USE_UNALIGNED_ACCESS) +# if !defined(XXH_USELESS_ALIGN_BRANCH) if ((((size_t)input) & 7)==0) /* Input is aligned, let's leverage the speed advantage */ { if ((endian_detected==XXH_littleEndian) || XXH_FORCE_NATIVE_FORMAT) @@ -538,7 +560,7 @@ XXH_errorcode XXH64_freeState(XXH64_state_t* statePtr) /*** Hash feed ***/ -XXH_errorcode XXH32_reset(XXH32_state_t* state_in, U32 seed) +XXH_errorcode XXH32_reset(XXH32_state_t* state_in, unsigned int seed) { XXH_istate32_t* state = (XXH_istate32_t*) state_in; state->seed = seed; @@ -708,7 +730,7 @@ FORCE_INLINE U32 XXH32_digest_endian (const XXH32_state_t* state_in, XXH_endiane } -U32 XXH32_digest (const XXH32_state_t* state_in) +unsigned int XXH32_digest (const XXH32_state_t* state_in) { XXH_endianess endian_detected = (XXH_endianess)XXH_CPU_LITTLE_ENDIAN; |