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/*-------------------------------------------------------------------------
*
* 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 */
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