ptimer1.c

RTEMS (Real-Time Executive for Multiprocessor Systems) is a free open source real-time operating sys

   if ( timer_pos == BAD_TIMER_C ) {
      /* The timer identifier is erroneus */
      rtems_set_errno_and_return_minus_one( EINVAL );
   }

   /* The timer is deleted */

   status = rtems_timer_delete ( timerid );

   if ( status == RTEMS_INVALID_ID ) {
     /* The timer identifier is erroneus */
     rtems_set_errno_and_return_minus_one( EINVAL );
   }

   /* Initializes the data of the timer */

   TIMER_INITIALIZE_S ( timer_pos );
   return 0;
}

/*
 *  14.2.4 Per-Process Timers, P1003.1b-1993, p. 267
 */

/* **************
 * timer_settime
 * **************/


int timer_settime(
  timer_t                  timerid,
  int                      flags,
  const struct itimerspec *value,
  struct itimerspec       *ovalue
)
{

   rtems_status_code return_v;   /* Return of the calls to RTEMS        */
   int               timer_pos;  /* Position of the timer in the table  */
   rtems_time_of_day rtems_time; /* Time in RTEMS                       */
   

   /* First the position in the table of timers is obtained */

   timer_pos = TIMER_POSITION_F ( timerid );

   if ( timer_pos == BAD_TIMER_C ) {
     /* The timer identifier is erroneus */
     rtems_set_errno_and_return_minus_one( EINVAL );
   }

   if ( value == NULL ) {
     /* The stucture of times of the timer is free, and then returns an
	error but the variable errno is not actualized */

     rtems_set_errno_and_return_minus_one( EINVAL );
   }

   /* If the function reaches this point, then it will be necessary to do
    * something with the structure of times of the timer: to stop, start 
    * or start it again */

   /* First, it verifies if the timer must be stopped */

   if ( value->it_value.tv_sec == 0 && value->it_value.tv_nsec == 0 ) {
      /* The timer is stopped */

      return_v = rtems_timer_cancel ( timerid );

      /* The old data of the timer are returned */

      if ( ovalue )
        *ovalue = timer_struct[timer_pos].timer_data;

      /* The new data are set */

      timer_struct[timer_pos].timer_data = *value;

      /* Indicates that the timer is created and stopped */
 
      timer_struct[timer_pos].state = STATE_CREATE_STOP_C;

      /* Returns with success */

      return 0;
   }

   /* 
    * If the function reaches this point, then the timer will have to be
    * initialized with new values: to start it or start it again 
    */
  
   /* First, it verifies if the structure "value" is correct */

    if ( ( value->it_value.tv_nsec > MAX_NSEC_C ) ||
         ( value->it_value.tv_nsec < MIN_NSEC_C ) ) {
       /* The number of nanoseconds is not correct */

       rtems_set_errno_and_return_minus_one( EINVAL );
    }

   /* Then, "value" must be converted from seconds and nanoseconds to clock
    * ticks, to use it in the calls to RTEMS */

   /* It is also necessary to take in account if the time is absolute 
    * or relative */

   switch (flags) {
      case TIMER_ABSTIME:

        /* The fire time is absolute:
         * It has to use "rtems_time_fire_when" */

        /* First, it converts from struct itimerspec to rtems_time_of_day */

        ITIMERSPEC_TO_RTEMS_TIME_OF_DAY_S ( value, &rtems_time );

        return_v = rtems_timer_fire_when ( timerid, &rtems_time, FIRE_TIMER_S, NULL);

        switch ( return_v ) {
           case RTEMS_SUCCESSFUL:

              /* The timer has been started and is running */

              /* Actualizes the data of the structure and 
               * returns the old ones in "ovalue" */

              if ( ovalue )
                *ovalue = timer_struct[timer_pos].timer_data;

              timer_struct[timer_pos].timer_data = *value;
 
              /* It indicates that the time is running */

              timer_struct[timer_pos].state = STATE_CREATE_RUN_C;

              /* Stores the time in which the timer was started again */

              timer_struct[timer_pos].time = _TOD_Current;
              return 0;

              break;

           case RTEMS_INVALID_ID:

              /* XXX error handling */
              break;

           case RTEMS_NOT_DEFINED:

              /* XXX error handling */
              break;

           case RTEMS_INVALID_CLOCK:

              /* XXX error handling */
              break;

           default: break;

        
        }
     
        break;

      case TIMER_RELATIVE_C:

        /* The fire time is relative:
         * It has to use "rtems_time_fire_after" */

        /* First, it converts from seconds and nanoseconds to ticks */

        /* The form in which this operation is done can produce a lost 
         * of precision of 1 second */
 
/*      This is the process to convert from nanoseconds to ticks
 *
 *      There is a tick every 10 miliseconds, then the nanoseconds are 
 *      divided between 10**7. The result of this operation will be the
 *      number of ticks 
 */

        timer_struct[timer_pos].ticks = 
             ( SEC_TO_TICKS_C * value->it_value.tv_sec ) +
             ( value->it_value.tv_nsec / (NSEC_PER_SEC_C / SEC_TO_TICKS_C));

        return_v = rtems_timer_fire_after ( timerid, 
                                           timer_struct[timer_pos].ticks, 
                                           FIRE_TIMER_S, 
                                           NULL );

        switch (return_v) {
           case RTEMS_SUCCESSFUL:

              /* The timer has been started and is running */

              /* Actualizes the data of the structure and 
               * returns the old ones in "ovalue" */

              if ( ovalue )
                *ovalue = timer_struct[timer_pos].timer_data;

              timer_struct[timer_pos].timer_data = *value;
 
              /* It indicates that the time is running */

              timer_struct[timer_pos].state = STATE_CREATE_RUN_C;

              /* Stores the time in which the timer was started again */

              timer_struct[timer_pos].time = _TOD_Current;
 
              return 0;

              break;

           case RTEMS_INVALID_ID:

              /* The timer identifier is not correct. In theory, this 
               * situation can not occur, but the solution is easy */ 

              rtems_set_errno_and_return_minus_one( EINVAL );

              break;

           case RTEMS_INVALID_NUMBER:

              /* In this case, RTEMS fails because the values of timing
               * are incorrect */

              /*
               * I do not know if errno must be actualized 
               *
               * errno = EINVAL;
               */

              rtems_set_errno_and_return_minus_one( EINVAL );
              break;
           
           default: break;
        }

        break;

      default: break;

        /* It does nothing, although it will be probably necessary to 
         * return an error */
   }

   /* To avoid problems */
   return 0;
}


/*
 *  14.2.4 Per-Process Timers, P1003.1b-1993, p. 267
 */

/* **************
 * timer_gettime
 * **************/

int timer_gettime(
  timer_t            timerid,
  struct itimerspec *value
)
{

 /* 
  * IDEA:  This function does not use functions of RTEMS to the handle
  *        of timers. It uses some functions for managing the time.
  *
  *        A possible form to do this is the following:
  *
  *          - When a timer is initialized, the value of the time in 
  *            that moment is stored.
  *          - When this function is called, it returns the difference
  *            between the current time and the initialization time.
  */
 
  rtems_time_of_day current_time;
  int               timer_pos;
  unsigned32        hours;
  unsigned32        minutes;
  unsigned32        seconds;
  unsigned32        ticks;
  unsigned32        nanosec;
 

  /* Reads the current time */

  current_time = _TOD_Current;

  timer_pos = TIMER_POSITION_F ( timerid );

  if ( timer_pos == BAD_TIMER_C ) {
    /* The timer identifier is erroneus */  
    rtems_set_errno_and_return_minus_one( EINVAL );
  }

  /* Calculates the difference between the start time of the timer and
   * the current one */

  hours    = current_time.hour - timer_struct[timer_pos].time.hour;

  if ( current_time.minute < timer_struct[timer_pos].time.minute ) {
     minutes = 60 - timer_struct[timer_pos].time.minute + current_time.minute;
     hours--;
  } else {
     minutes = current_time.minute - timer_struct[timer_pos].time.minute;
  }
    
  if ( current_time.second < timer_struct[timer_pos].time.second ) {
     seconds = 60 - timer_struct[timer_pos].time.second + current_time.second;
     minutes--;
  } else {
     seconds = current_time.second - timer_struct[timer_pos].time.second; 
  }

  if ( current_time.ticks < timer_struct[timer_pos].time.ticks ) {
     ticks = 100 - timer_struct[timer_pos].time.ticks + current_time.ticks;
     seconds--;
  } else {
     ticks = current_time.ticks - timer_struct[timer_pos].time.ticks; 
  }

  /* The time that the timer is running is calculated */
  seconds = hours   * 60 * 60 +
            minutes * 60      +
            seconds; 

  nanosec  = ticks * 10 *  /* msec     */
             1000  *       /* microsec */
             1000;         /* nanosec  */

  
  /* Calculates the time left before the timer finishes */
  
  value->it_value.tv_sec = 
    timer_struct[timer_pos].timer_data.it_value.tv_sec - seconds;
  
  value->it_value.tv_nsec = 
    timer_struct[timer_pos].timer_data.it_value.tv_nsec - nanosec;


  value->it_interval.tv_sec  = 
    timer_struct[timer_pos].timer_data.it_interval.tv_sec;
  value->it_interval.tv_nsec = 
    timer_struct[timer_pos].timer_data.it_interval.tv_nsec;
 

  return 0;

}

/*
 *  14.2.4 Per-Process Timers, P1003.1b-1993, p. 267
 */

/* *****************
 * timer_getoverrun
 * *****************/

int timer_getoverrun(
  timer_t   timerid
)
{

 /*
  * IDEA: This function must count the times the timer expires.
  *   
  *       The expiration of a timer must increase by one a counter.
  *       After the signal handler associated to the timer finishs 
  *       its execution, FIRE_TIMER_S will have to set this counter to 0.
  */

  int timer_pos; /* Position of the timer in the structure     */
  int overrun;   /* Overflow count                             */


  timer_pos = TIMER_POSITION_F ( timerid );

  if ( timer_pos == BAD_TIMER_C ) {
    /* The timer identifier is erroneus */
    rtems_set_errno_and_return_minus_one( EINVAL );
  }

  /* The overflow count of the timer is stored in "overrun" */

  overrun = timer_struct[timer_pos].overrun;

  /* It is set to 0 */

  timer_struct[timer_pos].overrun = 0;

  return overrun;

}