timer.c

来自「RTEMS (Real-Time Executive for Multiproc」· C语言 代码 · 共 71 行

/*  timer.c
 *
 *  This file manages the interval timer on the PA-RISC.
 *
 *  NOTE: It is important that the timer start/stop overhead be
 *        determined when porting or modifying this code.
 *
 *  COPYRIGHT (c) 1989-1999.
 *  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: timer.c,v 1.9.8.1 2003/09/04 18:45:40 joel Exp $
 */

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

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

rtems_boolean   Timer_driver_Find_average_overhead;

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

rtems_status_code Empty_function( void )
{
  return RTEMS_SUCCESSFUL;
}

void Set_find_average_overhead(
  rtems_boolean find_flag
)
{
  Timer_driver_Find_average_overhead = find_flag;
}