time_ring.c

/* Copyright 2008 Michael Marsh, University of Maryland.
 *
 * This file is part of pydtn.
 *
 * pydtn 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 of the License, or
 * (at your option) any later version.
 *
 * pydtn 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 pydtn.  If not, see <http://www.gnu.org/licenses/>.
 *
 * The views and conclusions contained in the software and documentation
 * are those of the authors and should not be interpreted as representing
 * official policies, either expressed or implied, of the University
 * of Maryland.
 *
 * pydtn extends and embeds the Python interpreter, which is
 * Copyright 2001-2006 Python Software Foundation, All Rights Reserved,
 * and is released under the PSF License Agreement.
 *
 * RANLUX random number generation uses the Boost library,
 * Copyright 1994-2006 by various authors (details in individual files),
 * which is released under the Boost Software License, Version 1.0.
 */

#include "aodv.h"

void
aodv_initialize_time_ring( aodv_time_ring_t* ring, unsigned int size )
{
   unsigned int i;

   ring->size = size;
   ring->offset = 0;
   ring->ring = (struct timeval*) calloc( size, sizeof(struct timeval) );
   for ( i = 0 ; i < size ; ++i )
   {
      ring->ring[i].tv_sec = -1;
      ring->ring[i].tv_usec = 0;
   }
}

/***********************************************************
 *  Update a time ring buffer with the current time.
 *
 *  The current time is inserted only if the corresponding
 *  action is consistent with the rate cap.
 *
 *  Returns:
 *    1  if the current time was successfully inserted
 *    0  otherwise
 *
 */
int
aodv_insert_time( aodv_time_ring_t* ring )
{
   struct timeval curr;
   struct timeval diff;

   if ( NULL == ring )
   {
      return 0;
   }
   if ( NULL == ring->ring )
   {
      return 0;
   }

   aodv_gettime( &curr );

   diff.tv_sec  = curr.tv_sec  - ring->ring[ring->offset].tv_sec;
   diff.tv_usec = curr.tv_usec - ring->ring[ring->offset].tv_usec;

   if ( diff.tv_usec < 0 )
   {
      diff.tv_usec += 1000000;
      diff.tv_sec -= 1;
   }

   if ( diff.tv_sec >= 1 )
   {
      ring->ring[ring->offset].tv_sec = curr.tv_sec;
      ring->ring[ring->offset].tv_usec = curr.tv_usec;
      ring->offset = ( ring->offset + 1 ) % ring->size;
      return 1;
   }
   return 0;
}

void
free_aodv_time_ring( aodv_time_ring_t* ring )
{
   if ( NULL == ring ) return;
   if ( NULL != ring->ring )
   {
      free( ring->ring );
   }
   free( ring );
}

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