FreeBSD/Linux Kernel Cross Reference
sys/x86/include/endian.h

     /*-
      * Copyright (c) 1987, 1991 Regents of the University of California.
      * All rights reserved.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
      * 1. Redistributions of source code must retain the above copyright
      *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 4. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     *      @(#)endian.h    7.8 (Berkeley) 4/3/91
     * $FreeBSD: releng/10.2/sys/x86/include/endian.h 233684 2012-03-29 23:31:48Z dim $
     */
    
    #ifndef _MACHINE_ENDIAN_H_
    #define _MACHINE_ENDIAN_H_
    
    #include <sys/cdefs.h>
    #include <sys/_types.h>
    
    /*
     * Define the order of 32-bit words in 64-bit words.
     */
    #define _QUAD_HIGHWORD 1
    #define _QUAD_LOWWORD 0
    
    /*
     * Definitions for byte order, according to byte significance from low
     * address to high.
     */
    #define _LITTLE_ENDIAN  1234    /* LSB first: i386, vax */
    #define _BIG_ENDIAN     4321    /* MSB first: 68000, ibm, net */
    #define _PDP_ENDIAN     3412    /* LSB first in word, MSW first in long */
    
    #define _BYTE_ORDER     _LITTLE_ENDIAN
    
    /*
     * Deprecated variants that don't have enough underscores to be useful in more
     * strict namespaces.
     */
    #if __BSD_VISIBLE
    #define LITTLE_ENDIAN   _LITTLE_ENDIAN
    #define BIG_ENDIAN      _BIG_ENDIAN
    #define PDP_ENDIAN      _PDP_ENDIAN
    #define BYTE_ORDER      _BYTE_ORDER
    #endif
    
    #define __bswap16_gen(x)        (__uint16_t)((x) << 8 | (x) >> 8)
    #define __bswap32_gen(x)                \
            (((__uint32_t)__bswap16((x) & 0xffff) << 16) | __bswap16((x) >> 16))
    #define __bswap64_gen(x)                \
            (((__uint64_t)__bswap32((x) & 0xffffffff) << 32) | __bswap32((x) >> 32))
    
    #ifdef __GNUCLIKE_BUILTIN_CONSTANT_P
    #define __bswap16(x)                            \
            ((__uint16_t)(__builtin_constant_p(x) ? \
                __bswap16_gen((__uint16_t)(x)) : __bswap16_var(x)))
    #define __bswap32(x)                    \
            (__builtin_constant_p(x) ?      \
                __bswap32_gen((__uint32_t)(x)) : __bswap32_var(x))
    #define __bswap64(x)                    \
            (__builtin_constant_p(x) ?      \
                __bswap64_gen((__uint64_t)(x)) : __bswap64_var(x))
    #else
    /* XXX these are broken for use in static initializers. */
    #define __bswap16(x)    __bswap16_var(x)
    #define __bswap32(x)    __bswap32_var(x)
    #define __bswap64(x)    __bswap64_var(x)
    #endif
    
    /* These are defined as functions to avoid multiple evaluation of x. */
    
    static __inline __uint16_t
    __bswap16_var(__uint16_t _x)
    {
    
            return (__bswap16_gen(_x));
    }
    
    static __inline __uint32_t
    __bswap32_var(__uint32_t _x)
   {
   
   #ifdef __GNUCLIKE_ASM
           __asm("bswap %0" : "+r" (_x));
           return (_x);
   #else
           return (__bswap32_gen(_x));
   #endif
   }
   
   static __inline __uint64_t
   __bswap64_var(__uint64_t _x)
   {
   
   #if defined(__amd64__) && defined(__GNUCLIKE_ASM)
           __asm("bswap %0" : "+r" (_x));
           return (_x);
   #else
           /*
            * It is important for the optimizations that the following is not
            * really generic, but expands to 2 __bswap32_var()'s.
            */
           return (__bswap64_gen(_x));
   #endif
   }
   
   #define __htonl(x)      __bswap32(x)
   #define __htons(x)      __bswap16(x)
   #define __ntohl(x)      __bswap32(x)
   #define __ntohs(x)      __bswap16(x)
   
   #endif /* !_MACHINE_ENDIAN_H_ */

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