diff options
Diffstat (limited to 'compat/bswap.h')
| -rw-r--r-- | compat/bswap.h | 179 |
1 files changed, 179 insertions, 0 deletions
diff --git a/compat/bswap.h b/compat/bswap.h new file mode 100644 index 0000000000..7fed637ed0 --- /dev/null +++ b/compat/bswap.h @@ -0,0 +1,179 @@ +/* + * Let's make sure we always have a sane definition for ntohl()/htonl(). + * Some libraries define those as a function call, just to perform byte + * shifting, bringing significant overhead to what should be a simple + * operation. + */ + +/* + * Default version that the compiler ought to optimize properly with + * constant values. + */ +static inline uint32_t default_swab32(uint32_t val) +{ + return (((val & 0xff000000) >> 24) | + ((val & 0x00ff0000) >> 8) | + ((val & 0x0000ff00) << 8) | + ((val & 0x000000ff) << 24)); +} + +static inline uint64_t default_bswap64(uint64_t val) +{ + return (((val & (uint64_t)0x00000000000000ffULL) << 56) | + ((val & (uint64_t)0x000000000000ff00ULL) << 40) | + ((val & (uint64_t)0x0000000000ff0000ULL) << 24) | + ((val & (uint64_t)0x00000000ff000000ULL) << 8) | + ((val & (uint64_t)0x000000ff00000000ULL) >> 8) | + ((val & (uint64_t)0x0000ff0000000000ULL) >> 24) | + ((val & (uint64_t)0x00ff000000000000ULL) >> 40) | + ((val & (uint64_t)0xff00000000000000ULL) >> 56)); +} + +#undef bswap32 +#undef bswap64 + +#if defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__)) + +#define bswap32 git_bswap32 +static inline uint32_t git_bswap32(uint32_t x) +{ + uint32_t result; + if (__builtin_constant_p(x)) + result = default_swab32(x); + else + __asm__("bswap %0" : "=r" (result) : "0" (x)); + return result; +} + +#define bswap64 git_bswap64 +#if defined(__x86_64__) +static inline uint64_t git_bswap64(uint64_t x) +{ + uint64_t result; + if (__builtin_constant_p(x)) + result = default_bswap64(x); + else + __asm__("bswap %q0" : "=r" (result) : "0" (x)); + return result; +} +#else +static inline uint64_t git_bswap64(uint64_t x) +{ + union { uint64_t i64; uint32_t i32[2]; } tmp, result; + if (__builtin_constant_p(x)) + result.i64 = default_bswap64(x); + else { + tmp.i64 = x; + result.i32[0] = git_bswap32(tmp.i32[1]); + result.i32[1] = git_bswap32(tmp.i32[0]); + } + return result.i64; +} +#endif + +#elif defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_X64)) + +#include <stdlib.h> + +#define bswap32(x) _byteswap_ulong(x) +#define bswap64(x) _byteswap_uint64(x) + +#endif + +#if defined(bswap32) + +#undef ntohl +#undef htonl +#define ntohl(x) bswap32(x) +#define htonl(x) bswap32(x) + +#endif + +#if defined(bswap64) + +#undef ntohll +#undef htonll +#define ntohll(x) bswap64(x) +#define htonll(x) bswap64(x) + +#else + +#undef ntohll +#undef htonll + +#if defined(__BYTE_ORDER) && defined(__LITTLE_ENDIAN) && defined(__BIG_ENDIAN) + +# define GIT_BYTE_ORDER __BYTE_ORDER +# define GIT_LITTLE_ENDIAN __LITTLE_ENDIAN +# define GIT_BIG_ENDIAN __BIG_ENDIAN + +#elif defined(BYTE_ORDER) && defined(LITTLE_ENDIAN) && defined(BIG_ENDIAN) + +# define GIT_BYTE_ORDER BYTE_ORDER +# define GIT_LITTLE_ENDIAN LITTLE_ENDIAN +# define GIT_BIG_ENDIAN BIG_ENDIAN + +#else + +# define GIT_BIG_ENDIAN 4321 +# define GIT_LITTLE_ENDIAN 1234 + +# if defined(_BIG_ENDIAN) && !defined(_LITTLE_ENDIAN) +# define GIT_BYTE_ORDER GIT_BIG_ENDIAN +# elif defined(_LITTLE_ENDIAN) && !defined(_BIG_ENDIAN) +# define GIT_BYTE_ORDER GIT_LITTLE_ENDIAN +# elif defined(__THW_BIG_ENDIAN__) && !defined(__THW_LITTLE_ENDIAN__) +# define GIT_BYTE_ORDER GIT_BIG_ENDIAN +# elif defined(__THW_LITTLE_ENDIAN__) && !defined(__THW_BIG_ENDIAN__) +# define GIT_BYTE_ORDER GIT_LITTLE_ENDIAN +# else +# error "Cannot determine endianness" +# endif + +#endif + +#if GIT_BYTE_ORDER == GIT_BIG_ENDIAN +# define ntohll(n) (n) +# define htonll(n) (n) +#else +# define ntohll(n) default_bswap64(n) +# define htonll(n) default_bswap64(n) +#endif + +#endif + +/* + * Performance might be improved if the CPU architecture is OK with + * unaligned 32-bit loads and a fast ntohl() is available. + * Otherwise fall back to byte loads and shifts which is portable, + * and is faster on architectures with memory alignment issues. + */ + +#if defined(__i386__) || defined(__x86_64__) || \ + defined(_M_IX86) || defined(_M_X64) || \ + defined(__ppc__) || defined(__ppc64__) || \ + defined(__powerpc__) || defined(__powerpc64__) || \ + defined(__s390__) || defined(__s390x__) + +#define get_be16(p) ntohs(*(unsigned short *)(p)) +#define get_be32(p) ntohl(*(unsigned int *)(p)) +#define put_be32(p, v) do { *(unsigned int *)(p) = htonl(v); } while (0) + +#else + +#define get_be16(p) ( \ + (*((unsigned char *)(p) + 0) << 8) | \ + (*((unsigned char *)(p) + 1) << 0) ) +#define get_be32(p) ( \ + (*((unsigned char *)(p) + 0) << 24) | \ + (*((unsigned char *)(p) + 1) << 16) | \ + (*((unsigned char *)(p) + 2) << 8) | \ + (*((unsigned char *)(p) + 3) << 0) ) +#define put_be32(p, v) do { \ + unsigned int __v = (v); \ + *((unsigned char *)(p) + 0) = __v >> 24; \ + *((unsigned char *)(p) + 1) = __v >> 16; \ + *((unsigned char *)(p) + 2) = __v >> 8; \ + *((unsigned char *)(p) + 3) = __v >> 0; } while (0) + +#endif |