/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 2001, 2012 Oracle and/or its affiliates.  All rights reserved.
 *
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code 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 General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 * $Id$
 */

#include "db_config.h"

#include "db_int.h"

/*
 * __os_unique_id --
 *	Return a unique 32-bit value.
 *
 * PUBLIC: void __os_unique_id __P((ENV *, u_int32_t *));
 */
void
__os_unique_id(env, idp)
	ENV *env;
	u_int32_t *idp;
{
	DB_ENV *dbenv;
	db_timespec v;
	pid_t pid;
	u_int32_t id;

	*idp = 0;

	dbenv = env == NULL ? NULL : env->dbenv;

	/*
	 * Our randomized value is comprised of our process ID, the current
	 * time of day and a stack address, all XOR'd together.
	 */
	__os_id(dbenv, &pid, NULL);
	__os_gettime(env, &v, 1);

	id = (u_int32_t)pid ^
	    (u_int32_t)v.tv_sec ^ (u_int32_t)v.tv_nsec ^ P_TO_UINT32(&pid);

	/*
	 * We could try and find a reasonable random-number generator, but
	 * that's not all that easy to do.  Seed and use srand()/rand(), if
	 * we can find them.
	 */
	if (DB_GLOBAL(uid_init) == 0) {
		DB_GLOBAL(uid_init) = 1;
		srand((u_int)id);
	}
	id ^= (u_int)rand();

	*idp = id;
}