/* -*- c++ -*- */
/*
 * Copyright 2006,2007,2008 Free Software Foundation, Inc.
 * 
 * This file is part of GNU Radio
 * 
 * GNU Radio 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 3, or (at your option)
 * any later version.
 * 
 * GNU Radio 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 GNU Radio; see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street,
 * Boston, MA 02110-1301, USA.
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <gruel/realtime.h>

#ifdef HAVE_SCHED_H
#include <sched.h>
#endif

#include <algorithm>
#include <math.h>
#include <string.h>
#include <errno.h>
#include <stdio.h>

#if defined(HAVE_PTHREAD_SETSCHEDPARAM) || defined(HAVE_SCHED_SETSCHEDULER)
#include <pthread.h>

namespace gruel {

  /*!
   * Rescale our virtual priority so that it maps to the middle 1/2 of
   * the priorities given by min_real_pri and max_real_pri.
   */
  static int
  rescale_virtual_pri(int virtual_pri, int min_real_pri, int max_real_pri)
  {
    float rmin = min_real_pri + (0.25 * (max_real_pri - min_real_pri));
    float rmax = min_real_pri + (0.75 * (max_real_pri - min_real_pri));
    float m = (rmax - rmin) / (rt_priority_max() - rt_priority_min());
    float y = m * (virtual_pri - rt_priority_min()) + rmin;
    int   y_int = static_cast<int>(rint(y));
    return std::max(min_real_pri, std::min(max_real_pri, y_int));
  }

}  // namespace gruel

#endif


#if defined(HAVE_PTHREAD_SETSCHEDPARAM)

namespace gruel {

  rt_status_t
  enable_realtime_scheduling(rt_sched_param p)
  {
    int policy = p.policy == RT_SCHED_FIFO ? SCHED_FIFO : SCHED_RR;
    int min_real_pri = sched_get_priority_min(policy);
    int max_real_pri = sched_get_priority_max(policy);
    int pri = rescale_virtual_pri(p.priority, min_real_pri, max_real_pri);

    // FIXME check hard and soft limits with getrlimit, and limit the value we ask for.
    // fprintf(stderr, "pthread_setschedparam: policy = %d, pri = %d\n", policy, pri);

    struct sched_param param;
    memset (&param, 0, sizeof (param));
    param.sched_priority = pri;
    int result = pthread_setschedparam (pthread_self(), policy, &param);
    if (result != 0) {
      if (result == EPERM)	// N.B., return value, not errno
        return RT_NO_PRIVS;
      else {
	fprintf(stderr,
		"pthread_setschedparam: failed to set real time priority: %s\n",
		strerror(result));
        return RT_OTHER_ERROR;
      }
    }
  
    //printf("SCHED_FIFO enabled with priority = %d\n", pri);
    return RT_OK;
  }
} // namespace gruel


#elif defined(HAVE_SCHED_SETSCHEDULER)

namespace gruel {

  rt_status_t
  enable_realtime_scheduling(rt_sched_param p)
  {
    int policy = p.policy == RT_SCHED_FIFO ? SCHED_FIFO : SCHED_RR;
    int min_real_pri = sched_get_priority_min(policy);
    int max_real_pri = sched_get_priority_max(policy);
    int pri = rescale_virtual_pri(p.priority, min_real_pri, max_real_pri);

    // FIXME check hard and soft limits with getrlimit, and limit the value we ask for.
    // fprintf(stderr, "sched_setscheduler: policy = %d, pri = %d\n", policy, pri);

    int pid = 0;  // this process
    struct sched_param param;
    memset(&param, 0, sizeof(param));
    param.sched_priority = pri;
    int result = sched_setscheduler(pid, policy, &param);
    if (result != 0){
      if (errno == EPERM)
        return RT_NO_PRIVS;
      else {
        perror ("sched_setscheduler: failed to set real time priority");
        return RT_OTHER_ERROR;
      }
    }
    
    //printf("SCHED_FIFO enabled with priority = %d\n", pri);
    return RT_OK;
  }

} // namespace gruel

#else

namespace gruel {

  rt_status_t
  enable_realtime_scheduling(rt_sched_param p)
  {
    return RT_NOT_IMPLEMENTED;
  }
} // namespace gruel

#endif