2015-10-08 19:01:36 +02:00
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/*-------------------------------------------------------------------------
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*
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* pg_bswap.h
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* Byte swapping.
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*
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* Macros for reversing the byte order of 32-bit and 64-bit unsigned integers.
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* For example, 0xAABBCCDD becomes 0xDDCCBBAA. These are just wrappers for
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* built-in functions provided by the compiler where support exists.
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2017-02-24 21:21:39 +01:00
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* Elsewhere, beware of multiple evaluations of the arguments!
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2015-10-08 19:01:36 +02:00
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*
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* Note that the GCC built-in functions __builtin_bswap32() and
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* __builtin_bswap64() are documented as accepting single arguments of type
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* uint32_t and uint64_t respectively (these are also the respective return
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* types). Use caution when using these wrapper macros with signed integers.
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*
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2017-01-03 19:48:53 +01:00
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* Copyright (c) 2015-2017, PostgreSQL Global Development Group
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2015-10-08 19:01:36 +02:00
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*
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* src/include/port/pg_bswap.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef PG_BSWAP_H
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#define PG_BSWAP_H
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#ifdef HAVE__BUILTIN_BSWAP32
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#define BSWAP32(x) __builtin_bswap32(x)
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#else
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2017-02-24 21:21:39 +01:00
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#define BSWAP32(x) ((((x) << 24) & 0xff000000) | \
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(((x) << 8) & 0x00ff0000) | \
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(((x) >> 8) & 0x0000ff00) | \
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(((x) >> 24) & 0x000000ff))
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2015-10-09 21:06:06 +02:00
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#endif /* HAVE__BUILTIN_BSWAP32 */
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2015-10-08 19:01:36 +02:00
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#ifdef HAVE__BUILTIN_BSWAP64
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#define BSWAP64(x) __builtin_bswap64(x)
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#else
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2017-02-24 21:21:39 +01:00
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#define BSWAP64(x) ((((x) << 56) & UINT64CONST(0xff00000000000000)) | \
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(((x) << 40) & UINT64CONST(0x00ff000000000000)) | \
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(((x) << 24) & UINT64CONST(0x0000ff0000000000)) | \
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(((x) << 8) & UINT64CONST(0x000000ff00000000)) | \
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(((x) >> 8) & UINT64CONST(0x00000000ff000000)) | \
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(((x) >> 24) & UINT64CONST(0x0000000000ff0000)) | \
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(((x) >> 40) & UINT64CONST(0x000000000000ff00)) | \
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(((x) >> 56) & UINT64CONST(0x00000000000000ff)))
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2015-10-09 21:06:06 +02:00
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#endif /* HAVE__BUILTIN_BSWAP64 */
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/*
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* Rearrange the bytes of a Datum from big-endian order into the native byte
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* order. On big-endian machines, this does nothing at all. Note that the C
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* type Datum is an unsigned integer type on all platforms.
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*
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* One possible application of the DatumBigEndianToNative() macro is to make
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* bitwise comparisons cheaper. A simple 3-way comparison of Datums
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* transformed by the macro (based on native, unsigned comparisons) will return
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* the same result as a memcmp() of the corresponding original Datums, but can
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* be much cheaper. It's generally safe to do this on big-endian systems
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* without any special transformation occurring first.
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*/
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#ifdef WORDS_BIGENDIAN
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#define DatumBigEndianToNative(x) (x)
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#else /* !WORDS_BIGENDIAN */
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#if SIZEOF_DATUM == 8
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#define DatumBigEndianToNative(x) BSWAP64(x)
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#else /* SIZEOF_DATUM != 8 */
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#define DatumBigEndianToNative(x) BSWAP32(x)
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#endif /* SIZEOF_DATUM == 8 */
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#endif /* WORDS_BIGENDIAN */
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2015-10-08 19:01:36 +02:00
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#endif /* PG_BSWAP_H */
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