endianness.h

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/* 
 * $Id: endianness.h,v 1.2 2008/07/01 21:56:06 andrei Exp $
 * 
 * Copyright (C) 2008 iptelorg GmbH
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */
/*
 *  endianness compile and runtime  tests
 * 
 * History:
 * --------
 *  2008-06-13  created by andrei
 */

/*
 * Defines:
 *    __IS_LITTLE_ENDIAN if the system is little endian and
 *    __IS_BIG_ENDIAN    if it's big endian
 * Function/macros:
 *     is_big_endian()  - runtime test for big endian
 *     is_little_endian() - runtime test for little endian
 *     endianness_sanity_check() - returns 0 if the compile time
 *                                  detected endianness corresponds to
 *                                  the runtime detected one and -1 on 
 *                                  error (recommended action: bail out)
 */
/*
 * Implementation notes:
 * Endian macro names/tests for different OSes:
 * linux:  __BYTE_ORDER == __LITTLE_ENDIAN | __BIG_ENDIAN
 *           BYTE_ORDER == LITTLE_ENDIAN | BIG_ENDIAN
 * bsd:     _BYTE_ORDER == _LITTLE_ENDIAN | _BIG_ENDIAN
 *           BYTE_ORDER == LITTLE_ENDIAN | BIG_ENDIAN
 * solaris: _LITTLE_ENDIAN | _BIG_ENDIAN
 *
 * Include file for the endian macros:
 * linux: <endian.h> (glibc), <sys/param.h>
 * bsd:   <sys/param.h>, <sys/endian.h>
 * solaris: <sys/param.h>
 *
 * Note: BIG_ENDIAN, LITTLE_ENDIAN, _BIG_ENDIAN, _LITTLE_ENDIAN cannot be 
 *       used always,  some OSes define both of them for BYTE_ORDER use
 *       (e.g. linux defines both BIG_ENDIAN & LITTLE_ENDIAN, bsds define
 *          _BIG_ENDIAN, _LITTLE_ENDIAN, BIG_ENDIAN, LITTLE_ENDIAN)
 *
 */


#ifndef _endianness_h
#define _endianness_h

/* use bsd includes: they work everywhere */
#include <sys/types.h>
#include <sys/param.h>



extern int _endian_test_int;

/* returns 1 for little endian, 0 for big endian */
#define endian_test()           (*(char*)&_endian_test_int==1)
#define is_big_endian()         (!endian_test())
#define is_little_endian()      endian_test()


extern int endianness_sanity_check();

/* detect compile time endianess */
#if defined __BYTE_ORDER && defined __LITTLE_ENDIAN && defined __BIG_ENDIAN
/* linux */
#if __BYTE_ORDER == __LITTLE_ENDIAN && ! defined __IS_LITTLE_ENDIAN
        #define __IS_LITTLE_ENDIAN 0x01020304
#endif
#if __BYTE_ORDER == __BIG_ENDIAN && ! defined __IS_BIG_ENDIAN
        #define __IS_BIG_ENDIAN 0x01020304
#endif
#elif defined _BYTE_ORDER && defined _LITTLE_ENDIAN && defined _BIG_ENDIAN
/* bsd */
#if _BYTE_ORDER == _LITTLE_ENDIAN && ! defined __IS_LITTLE_ENDIAN
        #define __IS_LITTLE_ENDIAN 0x01020304
#endif
#if _BYTE_ORDER == _BIG_ENDIAN && ! defined __IS_BIG_ENDIAN
        #define __IS_BIG_ENDIAN 0x01020304
#endif
#elif defined BYTE_ORDER && defined LITTLE_ENDIAN && defined BIG_ENDIAN
/* bsd old/deprecated */
#if BYTE_ORDER == LITTLE_ENDIAN && ! defined __IS_LITTLE_ENDIAN
        #define __IS_LITTLE_ENDIAN 0x01020304
#endif
#if BYTE_ORDER == BIG_ENDIAN && ! defined __IS_BIG_ENDIAN
        #define __IS_BIG_ENDIAN 0x01020304
#endif
#elif !(defined _LITTLE_ENDIAN && defined _BIG_ENDIAN) && \
                (defined _LITTLE_ENDIAN || defined _BIG_ENDIAN)
/* OSes that don't define BYTE_ORDER (sanity check above makes sure
 *   little & big endian are not defined in the same time )*/
/* solaris */
#if defined _LITTLE_ENDIAN && !defined __IS_LITTLE_ENDIAN
        #define __IS_LITTLE_ENDIAN 0x01020304
#endif
#if defined _BIG_ENDIAN && !defined __IS_BIG_ENDIAN
        #define __IS_BIG_ENDIAN 0x04030201
#endif
#elif !(defined LITTLE_ENDIAN && defined BIG_ENDIAN) && \
                (defined LITTLE_ENDIAN || defined BIG_ENDIAN)
/* OSes that don't define BYTE_ORDER (sanity check above makes sure
 *   little & big endian are not defined in the same time )*/
#if defined LITTLE_ENDIAN && !defined __IS_LITTLE_ENDIAN
        #define __IS_LITTLE_ENDIAN 0x01020304
#endif
#if defined BIG_ENDIAN && !defined __IS_BIG_ENDIAN
        #define __IS_BIG_ENDIAN 0x04030201
#endif

#else
#error could not detect endianess
#endif

#if !defined __IS_LITTLE_ENDIAN && !defined __IS_BIG_ENDIAN
#error BUG: could not detect endianess
#endif

#if defined __IS_LITTLE_ENDIAN && defined __IS_BIG_ENDIAN
#error BUG: both little & big endian detected in the same time
#endif


#endif /* _endianness_h */

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