diff options
Diffstat (limited to 'compat/bswap.h')
| -rw-r--r-- | compat/bswap.h | 175 |
1 files changed, 175 insertions, 0 deletions
diff --git a/compat/bswap.h b/compat/bswap.h new file mode 100644 index 0000000000..28635ebc69 --- /dev/null +++ b/compat/bswap.h @@ -0,0 +1,175 @@ +#ifndef COMPAT_BSWAP_H +#define COMPAT_BSWAP_H + +/* + * 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)); +} + +/* + * __has_builtin is available since Clang 10 and GCC 10. + * Below is a fallback for older compilers. + */ +#ifndef __has_builtin +# define __has_builtin(x) 0 +#endif + +#undef bswap32 +#undef bswap64 + +#if defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_X64) || defined(_M_ARM64)) + +#include <stdlib.h> + +#define bswap32(x) _byteswap_ulong(x) +#define bswap64(x) _byteswap_uint64(x) + +#define GIT_LITTLE_ENDIAN 1234 +#define GIT_BIG_ENDIAN 4321 +#define GIT_BYTE_ORDER GIT_LITTLE_ENDIAN + +#elif __has_builtin(__builtin_bswap32) && __has_builtin(__builtin_bswap64) + +#define bswap32(x) __builtin_bswap32((x)) +#define bswap64(x) __builtin_bswap64((x)) + +#endif + +#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 + +#elif defined(__BYTE_ORDER__) && defined(__ORDER_LITTLE_ENDIAN__) && defined(__ORDER_BIG_ENDIAN__) + +# define GIT_BYTE_ORDER __BYTE_ORDER__ +# define GIT_LITTLE_ENDIAN __ORDER_LITTLE_ENDIAN__ +# define GIT_BIG_ENDIAN __ORDER_BIG_ENDIAN__ + +#elif !defined(GIT_BYTE_ORDER) + +# 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 + +#undef ntohl +#undef htonl +#undef ntohll +#undef htonll + +#if GIT_BYTE_ORDER == GIT_BIG_ENDIAN +# define ntohl(x) (x) +# define htonl(x) (x) +# define ntohll(x) (x) +# define htonll(x) (x) +#else + +# if defined(bswap32) +# define ntohl(x) bswap32(x) +# define htonl(x) bswap32(x) +# else +# define ntohl(x) default_swab32(x) +# define htonl(x) default_swab32(x) +# endif + +# if defined(bswap64) +# define ntohll(x) bswap64(x) +# define htonll(x) bswap64(x) +# else +# define ntohll(x) default_bswap64(x) +# define htonll(x) default_bswap64(x) +# endif +#endif + +static inline uint16_t get_be16(const void *ptr) +{ + const unsigned char *p = ptr; + return (uint16_t)p[0] << 8 | + (uint16_t)p[1] << 0; +} + +static inline uint32_t get_be32(const void *ptr) +{ + const unsigned char *p = ptr; + return (uint32_t)p[0] << 24 | + (uint32_t)p[1] << 16 | + (uint32_t)p[2] << 8 | + (uint32_t)p[3] << 0; +} + +static inline uint64_t get_be64(const void *ptr) +{ + const unsigned char *p = ptr; + return (uint64_t)get_be32(&p[0]) << 32 | + (uint64_t)get_be32(&p[4]) << 0; +} + +static inline void put_be32(void *ptr, uint32_t value) +{ + unsigned char *p = ptr; + p[0] = (value >> 24) & 0xff; + p[1] = (value >> 16) & 0xff; + p[2] = (value >> 8) & 0xff; + p[3] = (value >> 0) & 0xff; +} + +static inline void put_be64(void *ptr, uint64_t value) +{ + unsigned char *p = ptr; + p[0] = (value >> 56) & 0xff; + p[1] = (value >> 48) & 0xff; + p[2] = (value >> 40) & 0xff; + p[3] = (value >> 32) & 0xff; + p[4] = (value >> 24) & 0xff; + p[5] = (value >> 16) & 0xff; + p[6] = (value >> 8) & 0xff; + p[7] = (value >> 0) & 0xff; +} + +#endif /* COMPAT_BSWAP_H */ |