QueueFlowControlHandler.java

/**
 * OnionCoffee - Anonymous Communication through TOR Network
 * Copyright (C) 2005-2007 RWTH Aachen University, Informatik IV
 * 
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * version 2 as published by the Free Software Foundation.
 * 
 * This program 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 this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
 */
package TorJava;

import java.io.IOException;

import TorJava.Common.QueueHandler;
import TorJava.Common.TorException;

/** convenient way to handle flow-control
 *
 * @author Lexi
 */
class QueueFlowControlHandler implements QueueHandler {
  int counter;
  int currLevel;
  int startLevel;
  int incLevel;
  Circuit circ;
  TCPStream stream;
  boolean circuitLevel;

  QueueFlowControlHandler(Circuit circ,int startLevel,int incLevel) {
    this.circ = circ;
    this.counter = 0;
    this.startLevel = startLevel;
    this.currLevel = startLevel;
    this.incLevel = incLevel;
  }

  QueueFlowControlHandler(TCPStream stream,int startLevel,int incLevel) {
    this.stream = stream;
    this.counter = 0;
    this.startLevel = startLevel;
    this.currLevel = startLevel;
    this.incLevel = incLevel;
  }

  private synchronized void count() {
    --currLevel;
    ++counter;
  }

  private synchronized void increase() {
    currLevel += incLevel;
  }

  /** return TRUE, if cell was handled */
  public boolean handleCell(Cell cell) 
    throws TorException 
  {
    count();
    // dropped below threshold - oh no!
    // better start sending SENDMEs...
    if (currLevel<=startLevel-incLevel) {
      try {
        if (circ != null) {
          // send to all routers in the circuit
          Logger.logCircuit(Logger.VERBOSE,"QueueFlowControlHandler.mainAction(): ("+counter+") "+currLevel+"<"+startLevel+" sending SENDME for circuit "+circ.print());
          for(int i=0;i<circ.route_established;++i) 
            circ.send_cell(new CellRelaySendme(circ,i));
        };
        if (stream != null) {
          // send to end-point
          Logger.logStream(Logger.VERBOSE,"QueueFlowControlHandler.mainAction(): ("+counter+") "+currLevel+"<"+startLevel+" sending SENDME for stream "+stream.print());
          stream.send_cell(new CellRelaySendme(stream));
        };
        increase();
      }
      catch(IOException e) {
        if (circ != null) 
          Logger.logCircuit(Logger.WARNING,"QueueFlowControlHandler.mainAction(): error sending SENDME "+e.getMessage());
        if (stream != null) 
          Logger.logStream(Logger.WARNING,"QueueFlowControlHandler.mainAction(): error sending SENDME "+e.getMessage());
      }
    };
    // always return FALSE to avoid swallowing cells
    return false;
  }

  /** close these things */
  public void close() {
  }
}