timer.c

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/* timer.c --- 
 * 
 * Filename: timer.c
 * Description: 
 * Author: Bryce Himebaugh
 * Maintainer: 
 * Created: Tue Oct  3 08:32:40 2006
 * Version: 
 * Last-Updated: 
 *           By: 
 *     Update #: 0
 * Keywords: 
 * Compatibility: 
 * 
 */

/* Commentary: 
 * 
 * 
 * 
 */

/* Change log:
 * 
 * 
 */

/* This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 * 
 * This program 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 for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; see the file COPYING.  If not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

/* Code: */
#include <stdio.h>
#include <sys/types.h> 
#include <sys/socket.h>
#include <netinet/in.h>
#include <strings.h>
#include <string.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include <unistd.h>
#include <signal.h>
#include <errno.h>
#include <pthread.h>
#include <time.h>
#include <sys/time.h>
#include "timer.h"

#define JITTER_MAX 1000

long jitter(long period);

int delay_uS(int uS) {
  struct timeval to;
  long time_error;
  to.tv_sec = 0;
  to.tv_usec = uS;    
  select(0,NULL,NULL,NULL,&to);
  time_error=jitter((long)uS);
  if ((time_error>JITTER_MAX)||(time_error<-JITTER_MAX)) {
    printf("%ld\n",time_error);
  }
  return (0);
}

void *periodic_thread(void *arg) {
  int status;
  timer_struct_t *tp = (timer_struct_t *) arg;

  while (1) {
    delay_uS(tp->timer_period);
    tp->timeout=1;
  }
  status = pthread_detach(pthread_self());
  return NULL;
}

long jitter(long period) {
  static struct timeval tv_last;
  static int init=1;
  struct timeval tv;
  long delta;
  long error;
  gettimeofday(&tv,NULL);
  if (!init) {
    if (tv.tv_usec<tv_last.tv_usec) {
      delta=(1000000-tv_last.tv_usec)+tv.tv_usec;
    }
    else {
      delta=tv.tv_usec-tv_last.tv_usec;
    }
    tv_last.tv_usec=tv.tv_usec;
    error=delta-period;
  }
  else {
    tv_last.tv_usec=tv.tv_usec;
    error=0;
    init=0;
  }
  return(error);
}

/* timer.c ends here */

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