example-buffer.c

Embedded Thread Library

/*
 * Copyright (c) 2004-2005, Swedish Institute of Computer Science.
 * All rights reserved. 
 *
 * Redistribution and use in source and binary forms, with or without 
 * modification, are permitted provided that the following conditions 
 * are met: 
 * 1. Redistributions of source code must retain the above copyright 
 *    notice, this list of conditions and the following disclaimer. 
 * 2. Redistributions in binary form must reproduce the above copyright 
 *    notice, this list of conditions and the following disclaimer in the 
 *    documentation and/or other materials provided with the distribution. 
 * 3. Neither the name of the Institute nor the names of its contributors 
 *    may be used to endorse or promote products derived from this software 
 *    without specific prior written permission. 
 *
 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND 
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE 
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 
 * SUCH DAMAGE. 
 *
 * This file is part of the protothreads library.
 *
 * Author: Adam Dunkels <[e-mail]>
 *
 * $Id: example-buffer.c,v 1.5 2005/10/07 05:21:33 adam Exp $
 */

#ifdef _WIN32
#include <windows.h>
#else
#include <unistd.h>
#endif
#include <stdio.h>

#include "pt-sem.h"
 
#define NUM_ITEMS 32
#define BUFSIZE 8

static int buffer[BUFSIZE];
static int bufptr;

static void
add_to_buffer(int item)
{
  printf("Item %d added to buffer at place %d\n", item, bufptr);  
  buffer[bufptr] = item;
  bufptr = (bufptr + 1) % BUFSIZE;
}
static int
get_from_buffer(void)
{
  int item;
  item = buffer[bufptr];
  printf("Item %d retrieved from buffer at place %d\n",
	 item, bufptr);
  bufptr = (bufptr + 1) % BUFSIZE;
  return item;
}

static int
produce_item(void)
{
  static int item = 0;
  printf("Item %d produced\n", item);
  return item++;
}

static void
consume_item(int item)
{
  printf("Item %d consumed\n", item);
}

static struct pt_sem full, empty;
 
static 
PT_THREAD(producer(struct pt *pt))
{
  static int produced;
  
  PT_BEGIN(pt);
  
  for(produced = 0; produced < NUM_ITEMS; ++produced) {
  
    PT_SEM_WAIT(pt, &full);
    
    add_to_buffer(produce_item());
    
    PT_SEM_SIGNAL(pt, &empty);
  }

  PT_END(pt);
}
 
static 
PT_THREAD(consumer(struct pt *pt))
{
  static int consumed;
  
  PT_BEGIN(pt);
 
  for(consumed = 0; consumed < NUM_ITEMS; ++consumed) {
    
    PT_SEM_WAIT(pt, &empty);
    
    consume_item(get_from_buffer());    
    
    PT_SEM_SIGNAL(pt, &full);
  }
 
  PT_END(pt);
}
 
static 
PT_THREAD(driver_thread(struct pt *pt))
{
  static struct pt pt_producer, pt_consumer;
 
  PT_BEGIN(pt);
  
  PT_SEM_INIT(&empty, 0);
  PT_SEM_INIT(&full, BUFSIZE);
 
  PT_INIT(&pt_producer);
  PT_INIT(&pt_consumer);
 
  PT_WAIT_THREAD(pt, producer(&pt_producer) &
		     consumer(&pt_consumer));
 
  PT_END(pt);
}


int
main(void)
{
  struct pt driver_pt;

  PT_INIT(&driver_pt);

  while(PT_SCHEDULE(driver_thread(&driver_pt))) {

    /*
     * When running this example on a multitasking system, we must
     * give other processes a chance to run too and therefore we call
     * usleep() resp. Sleep() here. On a dedicated embedded system,
     * we usually do not need to do this.
     */
#ifdef _WIN32
    Sleep(0);
#else
    usleep(10);
#endif
  }
  return 0;
}