delayunqueue.cc

COPE the first practical network coding scheme which is developped on click

/*
 * delayunqueue.{cc,hh} -- element pulls packets from input, delays pushing
 * the packet to output port.
 *
 * Copyright (c) 1999-2001 Massachusetts Institute of Technology
 * Copyright (c) 2002 International Computer Science Institute
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, subject to the conditions
 * listed in the Click LICENSE file. These conditions include: you must
 * preserve this copyright notice, and you cannot mention the copyright
 * holders in advertising related to the Software without their permission.
 * The Software is provided WITHOUT ANY WARRANTY, EXPRESS OR IMPLIED. This
 * notice is a summary of the Click LICENSE file; the license in that file is
 * legally binding.
 */

#include <click/config.h>
#include <click/error.hh>
#include <click/confparse.hh>
#include <click/glue.hh>
#include "delayunqueue.hh"
#include <click/standard/scheduleinfo.hh>
CLICK_DECLS

DelayUnqueue::DelayUnqueue()
    : Element(1, 1), _p(0), _task(this), _timer(&_task)
{
}

DelayUnqueue::~DelayUnqueue()
{
}

int
DelayUnqueue::configure(Vector<String> &conf, ErrorHandler *errh)
{
    return cp_va_parse(conf, this, errh,
		       cpInterval, "delay", &_delay, cpEnd);
}

int
DelayUnqueue::initialize(ErrorHandler *errh)
{
    ScheduleInfo::initialize_task(this, &_task, errh);
    _timer.initialize(this);
    _signal = Notifier::upstream_empty_signal(this, 0, &_task);
    return 0;
}

void
DelayUnqueue::cleanup(CleanupStage)
{
    if (_p)
	_p->kill();
}

bool
DelayUnqueue::run_task()
{
    bool worked = false;
  
  retry:
    // read a packet
    if (!_p && (_p = input(0).pull())) {
	if (!_p->timestamp_anno()._sec) // get timestamp if not set
	    _p->timestamp_anno().set_now();
	_p->timestamp_anno() += _delay;
    }
  
    if (_p) {
	Timestamp now = Timestamp::now();
	Timestamp diff = _p->timestamp_anno() - now;

	if (diff._sec < 0 || (diff._sec == 0 && diff._subsec == 0)) {
	    // packet ready for output
	    _p->timestamp_anno() = now;
	    output(0).push(_p);
	    _p = 0;
	    worked = true;
	    goto retry;
	} else if (diff._sec == 0 && diff._subsec < Timestamp::usec_to_subsec(100000))
	    // small delta, reschedule Task
	    /* Task rescheduled below */;
	else {
	    // large delta, schedule Timer
	    _timer.schedule_at(_p->timestamp_anno());
	    return false;		// without rescheduling
	}
    } else {
	// no Packet available
	if (!_signal)
	    return false;		// without rescheduling
    }

    _task.fast_reschedule();
    return worked;
}

String
DelayUnqueue::read_param(Element *e, void *)
{
    DelayUnqueue *u = (DelayUnqueue *)e;
    return cp_unparse_interval(u->_delay) + "\n";
}

void
DelayUnqueue::add_handlers()
{
    add_read_handler("delay", read_param, (void *)0);
    add_task_handlers(&_task);
}

CLICK_ENDDECLS
EXPORT_ELEMENT(DelayUnqueue)