FreeBSD/Linux Kernel Cross Reference
sys/osfmk/ppc/endian.h

     /*
      * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
      *
      * @APPLE_LICENSE_HEADER_START@
      * 
      * The contents of this file constitute Original Code as defined in and
      * are subject to the Apple Public Source License Version 1.1 (the
      * "License").  You may not use this file except in compliance with the
      * License.  Please obtain a copy of the License at
     * http://www.apple.com/publicsource and read it before using this file.
     * 
     * This Original Code and all software distributed under the License are
     * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
     * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
     * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
     * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
     * License for the specific language governing rights and limitations
     * under the License.
     * 
     * @APPLE_LICENSE_HEADER_END@
     */
    /*
     * @OSF_COPYRIGHT@
     * 
     */
    
    #ifndef _MACHINE_ENDIAN_H_
    #define _MACHINE_ENDIAN_H_
    
    /*
     * Definitions for byte order,
     * according to byte significance from low address to high.
     */
    #define LITTLE_ENDIAN   1234    /* least-significant byte first (vax) */
    #define BIG_ENDIAN      4321    /* most-significant byte first (IBM, net) */
    #define PDP_ENDIAN      3412    /* LSB first in word, MSW first in long (pdp) */
    
    #ifdef __BIG_ENDIAN__                   /* Predefined by compiler */
    #define BYTE_ORDER      BIG_ENDIAN      /* byte order we use on ppc */
    #define ENDIAN          BIG
    #else
    #error code has not been ported to little endian targets yet
    #endif
    
    /*
     * Macros for network/external number representation conversion.
     */
    #if BYTE_ORDER == BIG_ENDIAN && !defined(lint)
    #define ntohl(x)        (x)
    #define ntohs(x)        (x)
    #define htonl(x)        (x)
    #define htons(x)        (x)
    
    static __inline__ unsigned int byte_reverse_word(unsigned int word);
    static __inline__ unsigned int byte_reverse_word(unsigned int word) {
            unsigned int result;
            __asm__ volatile("lwbrx %0, 0, %1" : "=r" (result) : "r" (&word));
            return result;
    }
    
    /* The above function is commutative, so we can use it for
     * translations in both directions (to/from little endianness)
     * Note that htolx and ltohx are probably identical, they are
     * included for completeness.
     */
    #define htoll(x)  byte_reverse_word(x)
    #define htols(x)  (byte_reverse_word(x) >> 16)
    #define ltohl(x)  htoll(x)
    #define ltohs(x)  htols(x)
    
    #define htobl(x) (x)
    #define htobs(x) (x)
    #define btohl(x) (x)
    #define btohs(x) (x)
    
    #else
    unsigned short  ntohs(), htons();
    unsigned long   ntohl(), htonl();
    #endif
    
    /* This defines the order of elements in a bitfield,
     * it is principally used by the SCSI subsystem in
     * the definitions of mapped registers
     */
    #define BYTE_MSF 1
    
    #endif /* _MACHINE_ENDIAN_H_ */

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