FreeBSD/Linux Kernel Cross Reference
sys/i386/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.
     * 3. All advertising materials mentioning features or use of this software
     *    must display the following acknowledgement:
     *      This product includes software developed by the University of
     *      California, Berkeley and its contributors.
     * 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.
     *
     *      from: @(#)endian.h      7.8 (Berkeley) 4/3/91
     * $FreeBSD: src/sys/i386/include/endian.h,v 1.7.2.3 1999/09/05 08:11:47 peter Exp $
     */
    
    #ifndef _MACHINE_ENDIAN_H_
    #define _MACHINE_ENDIAN_H_
    
    /*
     * Define the order of 32-bit words in 64-bit words.
     */
    #define _QUAD_HIGHWORD 1
    #define _QUAD_LOWWORD 0
    
    #ifndef _POSIX_SOURCE
    
    /*
     * 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
    
    #ifndef KERNEL
    #include <sys/cdefs.h>
    
    __BEGIN_DECLS
    unsigned long   htonl __P((unsigned long));
    unsigned short  htons __P((unsigned short));
    unsigned long   ntohl __P((unsigned long));
    unsigned short  ntohs __P((unsigned short));
    __END_DECLS
    
    #endif /* !KERNEL */
    
    #define __word_swap_long(x) \
    ({ register u_long __X = (x); \
       __asm ("rorl $16, %1" \
            : "=r" (__X) \
            : "" (__X)); \
       __X; })
    #if __GNUC__ >= 2
    #define __byte_swap_long(x) \
    __extension__ ({ register u_long __X = (x); \
       __asm ("xchgb %h1, %b1\n\trorl $16, %1\n\txchgb %h1, %b1" \
            : "=q" (__X) \
            : "" (__X)); \
       __X; })
    #define __byte_swap_word(x) \
    __extension__ ({ register u_short __X = (x); \
       __asm ("xchgb %h1, %b1" \
            : "=q" (__X) \
            : "" (__X)); \
       __X; })
    #else /* __GNUC__ >= 2 */
    #define __byte_swap_long(x) \
    ({ register u_long __X = (x); \
       __asm ("rorw $8, %w1\n\trorl $16, %1\n\trorw $8, %w1" \
            : "=r" (__X) \
            : "" (__X)); \
       __X; })
    #define __byte_swap_word(x) \
    ({ register u_short __X = (x); \
       __asm ("rorw $8, %w1" \
            : "=r" (__X) \
           : "" (__X)); \
      __X; })
   #endif /* __GNUC__ >= 2 */
   
   /*
    * Macros for network/external number representation conversion.
    */
   #ifdef __GNUC__
   #define ntohl   __byte_swap_long
   #define ntohs   __byte_swap_word
   #define htonl   __byte_swap_long
   #define htons   __byte_swap_word
   #endif
   
   #define NTOHL(x)        ((x) = ntohl((u_long)(x)))
   #define NTOHS(x)        ((x) = ntohs((u_short)(x)))
   #define HTONL(x)        ((x) = htonl((u_long)(x)))
   #define HTONS(x)        ((x) = htons((u_short)(x)))
   
   #endif /* ! _POSIX_SOURCE */
   
   #endif /* !_MACHINE_ENDIAN_H_ */

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