116 lines
3.2 KiB
C
116 lines
3.2 KiB
C
/* byteswap.h - Byte swapping
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Copyright (C) 2005, 2007, 2009-2024 Free Software Foundation, Inc.
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Written by Oskar Liljeblad <oskar@osk.mine.nu>, 2005.
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This file is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as
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published by the Free Software Foundation; either version 2.1 of the
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License, or (at your option) any later version.
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This file is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>. */
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#ifndef _GL_BYTESWAP_H
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#define _GL_BYTESWAP_H 1
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/* This file uses _GL_INLINE. */
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#if !_GL_CONFIG_H_INCLUDED
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#error "Please include config.h first."
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#endif
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#include <stdint.h>
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_GL_INLINE_HEADER_BEGIN
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#ifndef _GL_BYTESWAP_INLINE
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# define _GL_BYTESWAP_INLINE _GL_INLINE
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#endif
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#ifdef __cplusplus
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extern "C" {
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#endif
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#if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 8)
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# define _GL_BYTESWAP_HAS_BUILTIN_BSWAP16 true
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#elif defined __has_builtin
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# if __has_builtin (__builtin_bswap16)
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# define _GL_BYTESWAP_HAS_BUILTIN_BSWAP16 true
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# endif
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#endif
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#if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
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# define _GL_BYTESWAP_HAS_BUILTIN_BSWAP32 true
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# define _GL_BYTESWAP_HAS_BUILTIN_BSWAP64 true
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#elif defined __has_builtin
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# if __has_builtin (__builtin_bswap32)
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# define _GL_BYTESWAP_HAS_BUILTIN_BSWAP32 true
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# endif
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# if __has_builtin (__builtin_bswap64)
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# define _GL_BYTESWAP_HAS_BUILTIN_BSWAP64 true
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# endif
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#endif
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/* Given an unsigned 16-bit argument X, return the value corresponding to
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X with reversed byte order. */
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_GL_BYTESWAP_INLINE uint_least16_t
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bswap_16 (uint_least16_t x)
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{
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#ifdef _GL_BYTESWAP_HAS_BUILTIN_BSWAP16
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return __builtin_bswap16 (x);
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#else
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uint_fast16_t mask = 0xff;
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return ( (x & mask << 8 * 1) >> 8 * 1
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| (x & mask << 8 * 0) << 8 * 1);
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#endif
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}
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/* Given an unsigned 32-bit argument X, return the value corresponding to
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X with reversed byte order. */
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_GL_BYTESWAP_INLINE uint_least32_t
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bswap_32 (uint_least32_t x)
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{
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#ifdef _GL_BYTESWAP_HAS_BUILTIN_BSWAP32
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return __builtin_bswap32 (x);
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#else
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uint_fast32_t mask = 0xff;
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return ( (x & mask << 8 * 3) >> 8 * 3
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| (x & mask << 8 * 2) >> 8 * 1
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| (x & mask << 8 * 1) << 8 * 1
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| (x & mask << 8 * 0) << 8 * 3);
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#endif
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}
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#ifdef UINT_LEAST64_MAX
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/* Given an unsigned 64-bit argument X, return the value corresponding to
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X with reversed byte order. */
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_GL_BYTESWAP_INLINE uint_least64_t
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bswap_64 (uint_least64_t x)
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{
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# ifdef _GL_BYTESWAP_HAS_BUILTIN_BSWAP64
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return __builtin_bswap64 (x);
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# else
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uint_fast64_t mask = 0xff;
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return ( (x & mask << 8 * 7) >> 8 * 7
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| (x & mask << 8 * 6) >> 8 * 5
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| (x & mask << 8 * 5) >> 8 * 3
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| (x & mask << 8 * 4) >> 8 * 1
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| (x & mask << 8 * 3) << 8 * 1
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| (x & mask << 8 * 2) << 8 * 3
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| (x & mask << 8 * 1) << 8 * 5
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| (x & mask << 8 * 0) << 8 * 7);
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# endif
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}
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#endif
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#ifdef __cplusplus
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}
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#endif
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_GL_INLINE_HEADER_END
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#endif /* _GL_BYTESWAP_H */
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