db_byteorder.c

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1996-2005
 *      Sleepycat Software.  All rights reserved.
 *
 * $Id: db_byteorder.c,v 12.1 2005/06/16 20:20:52 bostic Exp $
 */

#include "db_config.h"

#ifndef NO_SYSTEM_INCLUDES
#include <sys/types.h>
#endif

#include "db_int.h"

/*
 * __db_isbigendian --
 *      Return 1 if big-endian (Motorola and Sparc), not little-endian
 *      (Intel and Vax).  We do this work at run-time, rather than at
 *      configuration time so cross-compilation and general embedded
 *      system support is simpler.
 *
 * PUBLIC: int __db_isbigendian __P((void));
 */
int
__db_isbigendian()
{
        union {                                 /* From Harbison & Steele.  */
                long l;
                char c[sizeof(long)];
        } u;

        u.l = 1;
        return (u.c[sizeof(long) - 1] == 1);
}

/*
 * __db_byteorder --
 *      Return if we need to do byte swapping, checking for illegal
 *      values.
 *
 * PUBLIC: int __db_byteorder __P((DB_ENV *, int));
 */
int
__db_byteorder(dbenv, lorder)
        DB_ENV *dbenv;
        int lorder;
{
        int is_bigendian;

        is_bigendian = __db_isbigendian();

        switch (lorder) {
        case 0:
                break;
        case 1234:
                if (is_bigendian)
                        return (DB_SWAPBYTES);
                break;
        case 4321:
                if (!is_bigendian)
                        return (DB_SWAPBYTES);
                break;
        default:
                __db_err(dbenv,
            "unsupported byte order, only big and little-endian supported");
                return (EINVAL);
        }
        return (0);
}

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