diff options
Diffstat (limited to 'src/include/port/pg_bswap.h')
| -rw-r--r-- | src/include/port/pg_bswap.h | 161 |
1 files changed, 161 insertions, 0 deletions
diff --git a/src/include/port/pg_bswap.h b/src/include/port/pg_bswap.h new file mode 100644 index 0000000..9fd14d1 --- /dev/null +++ b/src/include/port/pg_bswap.h @@ -0,0 +1,161 @@ +/*------------------------------------------------------------------------- + * + * pg_bswap.h + * Byte swapping. + * + * Macros for reversing the byte order of 16, 32 and 64-bit unsigned integers. + * For example, 0xAABBCCDD becomes 0xDDCCBBAA. These are just wrappers for + * built-in functions provided by the compiler where support exists. + * + * Note that all of these functions accept unsigned integers as arguments and + * return the same. Use caution when using these wrapper macros with signed + * integers. + * + * Copyright (c) 2015-2020, PostgreSQL Global Development Group + * + * src/include/port/pg_bswap.h + * + *------------------------------------------------------------------------- + */ +#ifndef PG_BSWAP_H +#define PG_BSWAP_H + + +/* + * In all supported versions msvc provides _byteswap_* functions in stdlib.h, + * already included by c.h. + */ + + +/* implementation of uint16 pg_bswap16(uint16) */ +#if defined(HAVE__BUILTIN_BSWAP16) + +#define pg_bswap16(x) __builtin_bswap16(x) + +#elif defined(_MSC_VER) + +#define pg_bswap16(x) _byteswap_ushort(x) + +#else + +static inline uint16 +pg_bswap16(uint16 x) +{ + return + ((x << 8) & 0xff00) | + ((x >> 8) & 0x00ff); +} + +#endif /* HAVE__BUILTIN_BSWAP16 */ + + +/* implementation of uint32 pg_bswap32(uint32) */ +#if defined(HAVE__BUILTIN_BSWAP32) + +#define pg_bswap32(x) __builtin_bswap32(x) + +#elif defined(_MSC_VER) + +#define pg_bswap32(x) _byteswap_ulong(x) + +#else + +static inline uint32 +pg_bswap32(uint32 x) +{ + return + ((x << 24) & 0xff000000) | + ((x << 8) & 0x00ff0000) | + ((x >> 8) & 0x0000ff00) | + ((x >> 24) & 0x000000ff); +} + +#endif /* HAVE__BUILTIN_BSWAP32 */ + + +/* implementation of uint64 pg_bswap64(uint64) */ +#if defined(HAVE__BUILTIN_BSWAP64) + +#define pg_bswap64(x) __builtin_bswap64(x) + + +#elif defined(_MSC_VER) + +#define pg_bswap64(x) _byteswap_uint64(x) + +#else + +static inline uint64 +pg_bswap64(uint64 x) +{ + return + ((x << 56) & UINT64CONST(0xff00000000000000)) | + ((x << 40) & UINT64CONST(0x00ff000000000000)) | + ((x << 24) & UINT64CONST(0x0000ff0000000000)) | + ((x << 8) & UINT64CONST(0x000000ff00000000)) | + ((x >> 8) & UINT64CONST(0x00000000ff000000)) | + ((x >> 24) & UINT64CONST(0x0000000000ff0000)) | + ((x >> 40) & UINT64CONST(0x000000000000ff00)) | + ((x >> 56) & UINT64CONST(0x00000000000000ff)); +} +#endif /* HAVE__BUILTIN_BSWAP64 */ + + +/* + * Portable and fast equivalents for ntohs, ntohl, htons, htonl, + * additionally extended to 64 bits. + */ +#ifdef WORDS_BIGENDIAN + +#define pg_hton16(x) (x) +#define pg_hton32(x) (x) +#define pg_hton64(x) (x) + +#define pg_ntoh16(x) (x) +#define pg_ntoh32(x) (x) +#define pg_ntoh64(x) (x) + +#else + +#define pg_hton16(x) pg_bswap16(x) +#define pg_hton32(x) pg_bswap32(x) +#define pg_hton64(x) pg_bswap64(x) + +#define pg_ntoh16(x) pg_bswap16(x) +#define pg_ntoh32(x) pg_bswap32(x) +#define pg_ntoh64(x) pg_bswap64(x) + +#endif /* WORDS_BIGENDIAN */ + + +/* + * Rearrange the bytes of a Datum from big-endian order into the native byte + * order. On big-endian machines, this does nothing at all. Note that the C + * type Datum is an unsigned integer type on all platforms. + * + * One possible application of the DatumBigEndianToNative() macro is to make + * bitwise comparisons cheaper. A simple 3-way comparison of Datums + * transformed by the macro (based on native, unsigned comparisons) will return + * the same result as a memcmp() of the corresponding original Datums, but can + * be much cheaper. It's generally safe to do this on big-endian systems + * without any special transformation occurring first. + * + * If SIZEOF_DATUM is not defined, then postgres.h wasn't included and these + * macros probably shouldn't be used, so we define nothing. Note that + * SIZEOF_DATUM == 8 would evaluate as 0 == 8 in that case, potentially + * leading to the wrong implementation being selected and confusing errors, so + * defining nothing is safest. + */ +#ifdef SIZEOF_DATUM +#ifdef WORDS_BIGENDIAN +#define DatumBigEndianToNative(x) (x) +#else /* !WORDS_BIGENDIAN */ +#if SIZEOF_DATUM == 8 +#define DatumBigEndianToNative(x) pg_bswap64(x) +#else /* SIZEOF_DATUM != 8 */ +#define DatumBigEndianToNative(x) pg_bswap32(x) +#endif /* SIZEOF_DATUM == 8 */ +#endif /* WORDS_BIGENDIAN */ +#endif /* SIZEOF_DATUM */ + +#endif /* PG_BSWAP_H */ |