endian.c

/*
 * endian - determine the byte order of a long on your machine
 *
 * Copyright (C) 1999-2013,2021  Landon Curt Noll
 *
 * Calc is open software; you can redistribute it and/or modify it under
 * the terms of the version 2.1 of the GNU Lesser General Public License
 * as published by the Free Software Foundation.
 *
 * Calc is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General
 * Public License for more details.
 *
 * A copy of version 2.1 of the GNU Lesser General Public License is
 * distributed with calc under the filename COPYING-LGPL.  You should have
 * received a copy with calc; if not, write to Free Software Foundation, Inc.
 * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 *
 * Under source code control:   1993/11/15 04:32:58
 * File existed as early as:    1993
 *
 * chongo <was here> /\oo/\     http://www.isthe.com/chongo/
 * Share and enjoy!  :-)        http://www.isthe.com/chongo/tech/comp/calc/
 */

/*
 * Big Endian:      Amdahl, 68k, Pyramid, MIPS, Sparc, ...
 * Little Endian:   Vax, 32k, Spim (Dec Mips), i386, i486, ...
 */


#include <stdio.h>

#include "have_stdlib.h"
#if defined(HAVE_STDLIB_H)
#include <stdlib.h>
#endif

#include "have_unistd.h"
#if defined(HAVE_UNISTD_H)
#include <unistd.h>
#endif


#include "banned.h"     /* include after system header <> includes */


/* byte order array */
char byte[8] = { (char)0x12, (char)0x36, (char)0x48, (char)0x59,
                 (char)0x01, (char)0x23, (char)0x45, (char)0x67 };

int
main(void)
{
        /* pointers into the byte order array */
#if defined(DEBUG) || (!defined(BIG_ENDIAN) && !defined(BIG_ENDIAN))
        int *intp = (int *)byte;
#endif
#if defined(DEBUG)
        short *shortp = (short *)byte;
        long *longp = (long *)byte;

        printf("byte: %02x %02x %02x %02x %02x %02x %02x %02x\n",
            byte[0], byte[1], byte[2], byte[3],
            byte[4], byte[5], byte[6], byte[7]);
        printf("short: %04x %04x %04x %04x\n",
            shortp[0], shortp[1], shortp[2], shortp[3]);
        printf("int: %08x %08x\n",
            intp[0], intp[1]);
        printf("long: %08x %08x\n",
            longp[0], longp[1]);
#endif

        /* Print the standard <machine/endian.h> defines */
        printf("#undef BIG_ENDIAN\n");
        printf("#define BIG_ENDIAN\t4321\n");
        printf("#undef LITTLE_ENDIAN\n");
        printf("#define LITTLE_ENDIAN\t1234\n");
        printf("#undef CALC_BYTE_ORDER\n");

#if defined(BIG_ENDIAN)
        printf("#define CALC_BYTE_ORDER\tBIG_ENDIAN\n");
#elif defined(LITTLE_ENDIAN)
        printf("#define CALC_BYTE_ORDER\tLITTLW_ENDIAN\n");
#else
        /* Determine byte order */
        if (intp[0] == 0x12364859) {
            /* Most Significant Byte first */
            printf("#define CALC_BYTE_ORDER\tBIG_ENDIAN\n");
        } else if (intp[0] == 0x59483612) {
            /* Least Significant Byte first */
            printf("#define CALC_BYTE_ORDER\tLITTLE_ENDIAN\n");
        } else {
            fprintf(stderr, "@=-=@ Fatal build error - cannot @=-=@\n");
            fprintf(stderr, "@=-=@ determine byte order.  Set @=-=@\n");
            fprintf(stderr, "@=-=@ ${CALC_BYTE_ORDER} in the Makefile @=-=@\n");
            fprintf(stderr, "@=-=@ to be either -DBIG_ENDIAN or @=-=@\n");
            fprintf(stderr, "@=-=@ to be -DLITTLE_ENDIAN @=-=@\n");
            exit(1);
        }
#endif
        /* exit(0); */
        return 0;
}