/* -*- c -*- */

/*

 * Copyright 2007 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 this program; if not, write to the Free Software Foundation, Inc.,

 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

 */

#include <gcell/gc_jd_queue.h>

#include <gcell/memory_barrier.h>

#include <mutex_init.h>

#include <mutex_lock.h>

#include <mutex_unlock.h>

void 

gc_jd_queue_init(gc_jd_queue_t *q)

{

  _mutex_init(ptr_to_ea(&q->mutex));

  q->head = 0;

  q->tail = 0;

  smp_wmb();

}

void

gc_jd_queue_enqueue(gc_jd_queue_t *q, gc_job_desc_t *item)

{

  item->sys.next = 0;

  _mutex_lock(ptr_to_ea(&q->mutex));

  smp_rmb();                // import barrier

  if (q->tail == 0){    // currently empty

    q->tail = q->head = jdp_to_ea(item);

  }

  else {                // not empty, append

    ea_to_jdp(q->tail)->sys.next = jdp_to_ea(item);

    q->tail = jdp_to_ea(item);

  }

  smp_wmb();                // orders stores above before clearing of mutex

  _mutex_unlock(ptr_to_ea(&q->mutex));

}

gc_job_desc_t *

gc_jd_queue_dequeue(gc_jd_queue_t *q)

{

  _mutex_lock(ptr_to_ea(&q->mutex));

  smp_rmb();                // import barrier

  gc_eaddr_t item_ea = q->head;

  if (item_ea == 0){        // empty

    _mutex_unlock(ptr_to_ea(&q->mutex));

    return 0;

  }

  q->head = ea_to_jdp(item_ea)->sys.next;

  if (q->head == 0)        // now emtpy

    q->tail = 0;

  gc_job_desc_t *item = ea_to_jdp(item_ea);

  item->sys.next = 0;

  smp_wmb();                // orders stores above before clearing of mutex

  _mutex_unlock(ptr_to_ea(&q->mutex));

  return item;

}