bandwidth_time_filter.cc

这是一个著名的应用层组播中间件的源码

//Copyright (c) 2004, Charles Killian, Adolfo Rodriguez, Dejan Kostic, Sooraj Bhat, and Amin Vahdat
//All rights reserved.
//
//Redistribution and use in source and binary forms, with or without
//modification, are permitted provided that the following conditions are met:
//
//   * Redistributions of source code must retain the above copyright
//     notice, this list of conditions and the following disclaimer.
//   * 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.
//   * Neither the names of Duke University nor The University of
//     California, San Diego, nor the names of its contributors
//     may be used to endorse or promote products derived from
//     this software without specific prior written permission.
//
//THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 COPYRIGHT OWNER 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.

#include "bandwidth_time_filter.h"
#include <stdio.h>
#include "scheduler.h"
#include "macedon.h"

bandwidth_time_filter::bandwidth_time_filter( )
{
  value = 0.0;
}

bandwidth_time_filter::~bandwidth_time_filter()
{
}

// ---------------------------------------------- 
// get_value
// ---------------------------------------------- 

double  bandwidth_time_filter::get_value ()
{
  check();
  return  value;
}


// ---------------------------------------------- 
// clear
// ---------------------------------------------- 

void  bandwidth_time_filter::clear ()
{
  history.clear ();
  value = 0.0;
}


// ---------------------------------------------- 
// start_update
// ---------------------------------------------- 

void  bandwidth_time_filter::start_update ()
{
  // techinically we could start two updates without finishing one,
  // so be careful and don't do this
  double now =  Scheduler::instance().clock();

  // just add an entry with the start time
  if(!history.empty() && history.back().stop != 0 && history.back().size != 0) { 
    // This is a hack to add a "finish" block if we happen to start a segment
    // without finishing one.  This can happen if we add source as a neighbor
    // later on when we were recording bandwidth to him without having
    // requested anything.
    history.push_back(bandwidth_triplet(0, history.back().stop, 0));
  }
  history.push_back (bandwidth_triplet (now, 0, 0));
}

// ---------------------------------------------- 
// update
// ---------------------------------------------- 

void bandwidth_time_filter::update(int size1) {
  double now =  Scheduler::instance().clock();

  history.push_back(bandwidth_triplet(0, now, size1));
}

// ---------------------------------------------- 
// finish_update
// ---------------------------------------------- 

void bandwidth_time_filter::finish_update ()
{
  double now =  Scheduler::instance().clock();

  history.push_back(bandwidth_triplet(0, now, 0));
}


// ---------------------------------------------- 
// check
// ---------------------------------------------- 

void bandwidth_time_filter::check ()
{
  double elapsed_time = 0;
  double stop_time = -1;
  double end = 0;
  int total_bytes = 0;
  double seg_start, seg_stop;

  if(history.size() <= 1) {
    value = 0;
//    printf("Returning because not enough bw filter entries\n");
    return;
  }

  for(list<bandwidth_triplet>::reverse_iterator it = history.rbegin();
      it != history.rend(); ++it) {
    //printf("Entry is (%f %f %d)\n", it->start, it->stop, it->size);
    if(it->stop > 0 && end == 0) {
      /*if(Scheduler::instance().clock() - it->stop >= BANDWIDTH_WINDOW) {
	//printf("First entry is outside bandwidth window\n");
	value = 0;
	return;
      }*/
      end = it->stop;
      seg_stop = end;
      //printf("End time is %f\n", end);
    }
    if(it->stop > 0) {
      total_bytes += it->size;
      if(it->size == 0)
	seg_stop = it->stop;
      if(end - it->stop >= BANDWIDTH_WINDOW) {
	stop_time = it->stop;
	elapsed_time += (seg_stop - it->stop);
	break;
      }
      
    }
    else if(end != 0) {
      ASSERT(it->start != 0);
      seg_start = it->start;
      //printf("A segment from %f to %f has been added\n", seg_start, seg_stop);
      elapsed_time += (seg_stop - seg_start);
      if(elapsed_time >= BANDWIDTH_WINDOW) {
	stop_time = it->start;
	break;
      }
    }
  }
  //  if(stop_time == -1)
  //  stop_time = (history.front().stop > 0 ? history.front().stop : history.front().start);
  if(stop_time != -1) {
    //printf("Stop time is %f\n", stop_time);
    while((history.front().start > 0 && history.front().start != stop_time)
	  || (history.front().stop > 0 && history.front().stop != stop_time)) {
      history.pop_front();
    }
    if(history.front().start == 0) {
      history.front().start = history.front().stop;
      history.front().stop = 0;
      history.front().size = 0;
    }
  }
  if(history.front().start == 0) {
    history.front().start = history.front().stop;
    history.front().stop = 0;
    history.front().size = 0;
  }
  value = total_bytes*8/elapsed_time;
  //printf("Counted %d bytes over %f time. BW = %f\n", total_bytes, elapsed_time, value);
  
}