Contiki 2.6

clock.c

00001 /*
00002  * Copyright (c) 2007, Swedish Institute of Computer Science.
00003  * All rights reserved. 
00004  *
00005  * Redistribution and use in source and binary forms, with or without 
00006  * modification, are permitted provided that the following conditions 
00007  * are met: 
00008  * 1. Redistributions of source code must retain the above copyright 
00009  *    notice, this list of conditions and the following disclaimer. 
00010  * 2. Redistributions in binary form must reproduce the above copyright 
00011  *    notice, this list of conditions and the following disclaimer in the 
00012  *    documentation and/or other materials provided with the distribution. 
00013  * 3. Neither the name of the Institute nor the names of its contributors 
00014  *    may be used to endorse or promote products derived from this software 
00015  *    without specific prior written permission. 
00016  *
00017  * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND 
00018  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
00019  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 
00020  * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE 
00021  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 
00022  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 
00023  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 
00024  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 
00025  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 
00026  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 
00027  * SUCH DAMAGE. 
00028  *
00029  * This file is part of the Contiki operating system.
00030  * 
00031  * Author: Oliver Schmidt <ol.sc@web.de>
00032  *
00033  * $Id: clock.c,v 1.2 2008/07/12 14:44:37 oliverschmidt Exp $
00034  */
00035 
00036 #include <time.h>
00037 
00038 #include "contiki.h"
00039 
00040 /*---------------------------------------------------------------------------*/
00041 clock_time_t
00042 clock_time(void)
00043 {
00044   /* Contiki contains quite some calculations based on clock_time_t so we want
00045    * to avoid defining clock_time_t to be 32 bit because that would mean a lot
00046    * of overhead for cc65 targets.
00047    * On the other hand we want to avoid wrapping around frequently so the idea
00048    * is to reduce the clock resolution to the bare minimum. This is defined by
00049    * the TCP/IP stack using a 1/2 second periodic timer. So CLOCK_CONF_SECOND
00050    * needs to be defined at least as 2.
00051    * The value 2 works out especially nicely as it allows us to implement the
00052    * clock frequency devider below purely in (32 bit) integer arithmetic based
00053    * on the educated guess of CLK_TCK being an even value. */
00054   return clock() / (CLK_TCK / CLOCK_CONF_SECOND);
00055 }
00056 /*---------------------------------------------------------------------------*/
00057 unsigned long
00058 clock_seconds(void)
00059 {
00060   return clock() / CLK_TCK;
00061 }
00062 /*---------------------------------------------------------------------------*/