incr_seq.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"

uint32_t
aodv_incr_seq_base( uint32_t* seq )
{
   uint32_t temp;
   if ( NULL == seq )
   {
      return 0;
   }
   temp = ~(*seq);
   if ( 0 == temp )
   {
      *seq = 1;
   }
   else
   {
      ++(*seq);
   }
   return *seq;
}

uint32_t
aodv_incr_seq( aodv_state_t* state )
{
   return aodv_incr_seq_base( &(state->sequence_number) );
}

uint32_t
aodv_incr_rreq_id( aodv_state_t* state )
{
   uint32_t temp;
   temp = ~(state->rreq_id);
   if ( 0 == temp )
   {
      state->rreq_id = 0;
   }
   else
   {
      ++(state->rreq_id);
   }
   return state->rreq_id;
}

/*
 * This does what the draft _says_ should be done, but without assuming
 * a particular underflow/overflow behavior.
 *
 */
char
aodv_cmp_seq( uint32_t a, uint32_t b )
{
   static const uint32_t sign_bit = 1 << 31;
   uint32_t diff;

   if ( a == b ) return 0;
   if ( 0 == a ) return -1;
   if ( 0 == b ) return 1;
   if ( a > b )
   {
      diff = a - b;
      return ( diff & sign_bit ) ? -1 : 1;
   }
   else
   {
      diff = b - a;
      return ( diff & sign_bit ) ? 1 : -1;
   }
}

---