path: root/c/src/lib/libbsp/unix/posix/timer/timer.c

/*  timer.c
 *
 *  This file manages the interval timer on a UNIX BSP.
 *
 *  NOTE: It is important that the timer start/stop overhead be
 *        determined when porting or modifying this code.
 *
 *  COPYRIGHT (c) 1989-2003.
 *  On-Line Applications Research Corporation (OAR).
 *
 *  The license and distribution terms for this file may be
 *  found in the file LICENSE in this distribution or at
 *  http://www.rtems.com/license/LICENSE.
 *
 *  $Id$
 */

#include <bsp.h>
#include <time.h>
#include <sys/time.h>

struct timeval  Timer_start;
struct timeval  Timer_stop;
struct timezone Time_zone;

rtems_boolean   benchmark_timer_find_average_overhead;

void benchmark_timer_initialize()
{
   gettimeofday( &Timer_start, &Time_zone );
}

#define AVG_OVERHEAD      0  /* It typically takes xxx microseconds */
                             /* (XX countdowns) to start/stop the timer. */
#define LEAST_VALID       10 /* Don't trust a value lower than this */

int benchmark_timer_read()
{
  int total;

  gettimeofday( &Timer_stop, &Time_zone );

  if ( Timer_stop.tv_sec == Timer_start.tv_sec )
    total = Timer_stop.tv_usec - Timer_start.tv_usec;
  else {
    total  = 1000000 - Timer_start.tv_usec;
    total += (Timer_stop.tv_sec - Timer_start.tv_sec - 1) * 1000000;
    total += Timer_stop.tv_usec;
  }

  if ( benchmark_timer_find_average_overhead == 1 )
      return total;          /* in countdown units */
  else {
    if ( total < LEAST_VALID )
        return 0;            /* below timer resolution */
    return total - AVG_OVERHEAD;
  }
}

void benchmark_timer_disable_subtracting_average_overhead(
  rtems_boolean find_flag
)
{
  benchmark_timer_find_average_overhead = find_flag;
}