mac-timers.cc

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/* -*-  Mode:C++; c-basic-offset:8; tab-width:8; indent-tabs-mode:t -*- */
/*
 * Copyright (c) 1997 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the Computer Systems
 *      Engineering Group at Lawrence Berkeley Laboratory.
 * 4. Neither the name of the University nor of the Laboratory may be used
 *    to endorse or promote products derived from this software without
 *    specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */
/* Ported from CMU/Monarch's code, nov'98 -Padma.*/


#include <delay.h>
#include <connector.h>
#include <packet.h>
#include <random.h>
 
// #define DEBUG
//#include <debug.h>
#include <arp.h>
#include <ll.h>
#include <mac.h>
#include <mac-timers.h>
#include <mac-802_11.h> 

/*
 * Force timers to expire on slottime boundries.
 */
// #define USE_SLOT_TIME

#define ROUND_TIME()    \
        {                                                               \
                assert(slottime);                                       \
                double rmd = remainder(s.clock() + rtime, slottime);    \
                if(rmd > 0.0)                                           \
                        rtime += (slottime - rmd);                      \
                else                                                    \
                        rtime += (-rmd);                                \
        }


/* ======================================================================
   Timers
   ====================================================================== */

void
MacTimer::start(double time)
{
        Scheduler &s = Scheduler::instance();
        assert(busy_ == 0);

        busy_ = 1;
        paused_ = 0;
        stime = s.clock();
        rtime = time;
        assert(rtime >= 0.0);


        s.schedule(this, &intr, rtime);
}

void
MacTimer::stop(void)
{
        Scheduler &s = Scheduler::instance();

        assert(busy_);

        if(paused_ == 0)
                s.cancel(&intr);

        busy_ = 0;
        paused_ = 0;
        stime = 0.0;
        rtime = 0.0;
}

/* ======================================================================
   Defer Timer
   ====================================================================== */
void
DeferTimer::start(double time)
{
        Scheduler &s = Scheduler::instance();

        assert(busy_ == 0);

        busy_ = 1;
        paused_ = 0;
        stime = s.clock();
        rtime = time;
#ifdef USE_SLOT_TIME
        ROUND_TIME();
#endif
        assert(rtime >= 0.0);

        s.schedule(this, &intr, rtime);
}


void    
DeferTimer::handle(Event *)
{       
        busy_ = 0;
        paused_ = 0;
        stime = 0.0;
        rtime = 0.0;



        mac->deferHandler();
}

/* ======================================================================
   NAV Timer
   ====================================================================== */
void    
NavTimer::handle(Event *)
{       
        busy_ = 0;
        paused_ = 0;
        stime = 0.0;
        rtime = 0.0;

        mac->navHandler();
}


/* ======================================================================
   Receive Timer
   ====================================================================== */
void    
RxTimer::handle(Event *)
{       
        busy_ = 0;
        paused_ = 0;
        stime = 0.0;
        rtime = 0.0;

        mac->recvHandler();
}


/* ======================================================================
   Send Timer
   ====================================================================== */
void    
TxTimer::handle(Event *)
{       
        busy_ = 0;
        paused_ = 0;
        stime = 0.0;
        rtime = 0.0;



        mac->sendHandler();
}


/* ======================================================================
   Interface Timer
   ====================================================================== */
void
IFTimer::handle(Event *)
{
        busy_ = 0;
        paused_ = 0;
        stime = 0.0;
        rtime = 0.0;

        mac->txHandler();
}


/* ======================================================================
   Backoff Timer
   ====================================================================== */
void
BackoffTimer::handle(Event *)
{
        busy_ = 0;
        paused_ = 0;
        stime = 0.0;
        rtime = 0.0;
        difs_wait = 0.0;

        mac->backoffHandler();
}

void
BackoffTimer::start(int cw, int idle)
{
        Scheduler &s = Scheduler::instance();

        assert(busy_ == 0);

        busy_ = 1;
        paused_ = 0;
        stime = s.clock();
        

        rtime = (Random::random() % cw) * mac->phymib_->SlotTime;


#ifdef USE_SLOT_TIME
        ROUND_TIME();
#endif
        difs_wait = 0.0;

        if(idle == 0)
                paused_ = 1;
        else {
                assert(rtime >= 0.0);
                s.schedule(this, &intr, rtime);
        }
}


void
BackoffTimer::pause()
{
        Scheduler &s = Scheduler::instance();

        //the caculation below make validation pass for linux though it
        // looks dummy

        double st = s.clock();
        double rt = stime + difs_wait;
        double sr = st - rt;
        double mst = (mac->phymib_->SlotTime);

        int slots = int (sr/mst);

    //int slots = (int) ((s.clock() - (stime + difs_wait)) / mac->phymib_->SlotTime);
        if(slots < 0)
                slots = 0;
        assert(busy_ && ! paused_);

        paused_ = 1;
        rtime -= (slots * mac->phymib_->SlotTime);
        assert(rtime >= 0.0);

        difs_wait = 0.0;

        s.cancel(&intr);
}


void
BackoffTimer::resume(double difs)
{
        Scheduler &s = Scheduler::instance();

        assert(busy_ && paused_);

        paused_ = 0;
        stime = s.clock();

        /*
         * The media should be idle for DIFS time before we start
         * decrementing the counter, so I add difs time in here.
         */
        difs_wait = difs;
        /*
#ifdef USE_SLOT_TIME
        ROUND_TIME();
#endif
        */
        assert(rtime + difs_wait >= 0.0);
        s.schedule(this, &intr, rtime + difs_wait);
}

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