csma.java

cdma－cd的java源代码cdma－cd的java源代码

/* 
Simulation of CSMA done by B.Anuradha ,C.Manoj Kumar,T.Chitti Babu
done as a part of the course Distributed Systems offered by Dr. Sridhar Iyer,IIT BOMBAY.
*/

import java.applet.*;
import java.awt.*;
import java.awt.image.*;
import java.lang.Math;
import java.util.Random;



class Timer extends Thread {
  
  public  int myTime = 0;
  public static int myTime1 = 0;
  Network myNetwork;
  Component myComponent;
  int myInterval;

  void setTime(int value)
  {
  	myTime = value;
  }
    
  void sleep(int time) 
  {
    try { 
      Thread.sleep(time); 
       } 
    catch (InterruptedException e)
     {
      
     }
   }

  public Timer(Network network, Component component, int interval) {
    myNetwork = network;
    myComponent = component;
    myInterval = interval;
   
  }

  public void run() 
  {
    while (true) 
    {	
      myNetwork.update();
      myComponent.repaint();
      sleep(myInterval);
	   myTime++;
    }
  } 
}



class Counter {

  int myCount;
  
  public Counter( int start ) 
  {
    myCount = start;
  }

  public void decrement() 
  {
    myCount--;
    return;
  }

  public void increment() 
  {
    myCount++;
    return;
  }

  public int getCount() 
  {
    return myCount;
  }

  public void setCount(int count) 
  {
    myCount = count;
  }

}

/* the left and right parts of a signal are simualated */

class Part {

  Medium myMedium;

  int myMaxFrameSize;
  int myLength;

  int myOffset;
  int myStart;
  int myEnd;

  public boolean myDoneFlag;

  boolean myCollisionFlag;

  public Part( int start, int end, int offset, int frameSize, Medium medium ) 
  {
    myStart = start;
    myEnd = end;
    myOffset = offset;
    myCollisionFlag = false;
    myMaxFrameSize = frameSize;
    myMedium = medium;
    myLength = 0;
    myDoneFlag = false;
  }

  void setCollisionFlag( boolean flag ) 
  {
    myCollisionFlag = flag;
  }

  boolean getCollisionFlag() 
  {
    return myCollisionFlag;
  }

  boolean getDoneFlag() 
  {
    return myDoneFlag;
  }

  int getStart() 
  {
    return myStart;
  }

  int getEnd() 
  {
    return myEnd;
  }

  boolean isSent() 
  {
    return (myLength > myMaxFrameSize);
  }

  public void update() 
  {

    if (myLength>0 && myStart==myEnd) 
    {
      myDoneFlag=true;
      return;
    }
    myLength = myLength + Math.abs(myOffset);
    myStart = myStart + myOffset;
    if ( myLength > myMaxFrameSize )
       myEnd = myEnd + myOffset;

    if (myStart<0) 
      myStart = 0;

    if (myStart>myMedium.getBusLength() )//ACTULLY buslength=100
      myStart = myMedium.getBusLength();

    if (myEnd<0) 
      myEnd = 0;

    if (myEnd>myMedium.getBusLength() )
      myEnd = myMedium.getBusLength();

  }

}

/* the various kinds of (messages for transmission) signals are simulated here */
class Signal 
{
  
  Part myLeftPart;
  Part myRightPart;
  
  int myStationId;

  int getStationId() 
  {
    return myStationId;
  }
	public void setIdle()
	{
		myLeftPart.myDoneFlag=true;
		myRightPart.myDoneFlag=true;
	}
  Part getLeftPart() 
  {
    return myLeftPart;
  }

  Part getRightPart() 
  {
    return myRightPart;
  }

  public Signal(int stationId, int position, int frameSize, Medium medium) 
  {
    myStationId = stationId;
    myLeftPart = new Part(position,position,-1,frameSize,medium);
    myRightPart = new Part(position,position, 1,frameSize,medium);
  }

  public void update() 
  {
    myLeftPart.update();
    myRightPart.update();    
  }

  public boolean isDone() 
  {
    return myLeftPart.getDoneFlag() && myRightPart.getDoneFlag();
  }

  public boolean isCollision() 
  {
    return myLeftPart.getCollisionFlag() || myRightPart.getCollisionFlag();
  }

  boolean isSent() 
  {
    return myLeftPart.isSent() && myRightPart.isSent();
  }


}

/* the medium class which simulates the medium(-bus) */
class Medium {
  
 
  int myBusLength        = 100;	        // in meters
  
  public static final int MAX_SIGNALS = 10;


  Signal[] mySignals;

  boolean isInInterval(int value, int start, int end) 
  {
    if ( (value>=Math.min(start,end))&&(value<=Math.max(start,end)) )
      return true;
    else
      return false;
  }
	
  public void setMediumIdle()
  {
 		for(int j=0;j<10;j++)
		 if(mySignals[j]!=null)
		 	mySignals[j].setIdle();
			  
  }	
  public Medium() 
  {    
    mySignals = new Signal[MAX_SIGNALS];    
  }

  public int getBusLength() 
  {
    return myBusLength;
  }

  Signal[] getSignals() 
  {
    return mySignals;
  }
  

  public boolean isCollision(int station, int position) 
  {
    int index;
    for ( index=0; index<MAX_SIGNALS; index++ ) 
    {
      if ( (mySignals[index] != null) && (mySignals[index].getStationId()!=station) ) 
      {
        if ( isInInterval( position, mySignals[index].getLeftPart().getStart(), 
			   mySignals[index].getLeftPart().getEnd() ) ) 
			   {
          if ( mySignals[index].getLeftPart().getCollisionFlag() == true ) 
          {
            return true;
          }
        }
        if ( isInInterval( position, mySignals[index].getRightPart().getStart(),
			    mySignals[index].getRightPart().getEnd() ) ) {
          if ( mySignals[index].getRightPart().getCollisionFlag() == true ) {
            return true;
          }
        }        
      }
    }

    return false;
  }

  public boolean isFree(int position) {

    int index;

    for ( index=0; index<MAX_SIGNALS; index++ ) {
      if ( mySignals[index] != null ) {
        if ( isInInterval( position, mySignals[index].getLeftPart().getStart(), 
			   mySignals[index].getLeftPart().getEnd() ) ) {
          return false;
        }
        if ( isInInterval( position, mySignals[index].getRightPart().getStart(), 
			   mySignals[index].getRightPart().getEnd() ) ) {
          return false;
        }
        
        return true;
      }
    }

    return true;
  }

  void sleep(int time) {
    try { 
      Thread.sleep(time); 
    } 
    catch (InterruptedException e) {
      
    }
  }

  public boolean send( int station, int position, int frameSize) {

    int index;

    for ( index=0; index<MAX_SIGNALS; index++ ) {
      if ( mySignals[index] == null ) {
        
        mySignals[index] = new Signal( station, position, frameSize, this);

        while(true) {
          if ( mySignals[index].isSent() ) {
            return true;
          }          
          if ( isCollision(station, position) ) {
            return false;
          }          
          sleep(50);
        }
      }
    }

    return false;
  }

  public void update() {

    int i,j; 
    int start,end, id;

    
    // update signals
    for ( i=0; i<MAX_SIGNALS; i++ ) {
      if ( mySignals[i] != null ) {        
        mySignals[i].update();
          if ( mySignals[i].isDone() ) {
            mySignals[i] = null;
          }
      }
    }

    // find collisions
    for ( i=0; i<MAX_SIGNALS; i++ ) {
      if ( mySignals[i] != null ) {        
        id    = mySignals[i].getStationId();

        start = mySignals[i].getLeftPart().getStart();
        end   = mySignals[i].getLeftPart().getEnd();

        for ( j=0; j<MAX_SIGNALS; j++ ) {
          if ( (mySignals[j] != null) && (mySignals[j].getStationId() != id)) {

            if ( isInInterval( mySignals[j].getLeftPart().getStart(), start, end ) ) {
              mySignals[i].getLeftPart().setCollisionFlag(true);
              if (!mySignals[i].getRightPart().isSent())
                {
                mySignals[i].getRightPart().setCollisionFlag(true);
                mySignals[j].getLeftPart().setCollisionFlag(true);
						}
              break;
            }
            if ( isInInterval( mySignals[j].getLeftPart().getEnd(), start, end ) ) {
              mySignals[i].getLeftPart().setCollisionFlag(true);
              if (!mySignals[i].getRightPart().isSent())
               {
                mySignals[i].getRightPart().setCollisionFlag(true);
                 mySignals[j].getLeftPart().setCollisionFlag(true);
					}
              break;
            }
            if ( isInInterval( mySignals[j].getRightPart().getStart(), start, end ) ) {
              mySignals[i].getLeftPart().setCollisionFlag(true);
              if (!mySignals[i].getRightPart().isSent())
                {
                mySignals[i].getRightPart().setCollisionFlag(true);
               mySignals[j].getLeftPart().setCollisionFlag(true);
					}
              break;
            }
            if ( isInInterval( mySignals[j].getRightPart().getEnd(), start, end ) ) {
              mySignals[i].getLeftPart().setCollisionFlag(true);
              if (!mySignals[i].getRightPart().isSent())
               {
                mySignals[i].getRightPart().setCollisionFlag(true);
               mySignals[j].getLeftPart().setCollisionFlag(true);
					}
					break;
            }
          }
        }

        start = mySignals[i].getRightPart().getStart();
        end   = mySignals[i].getRightPart().getEnd();

        for ( j=0; j<MAX_SIGNALS; j++ ) {
          if ( (mySignals[j] != null) && (mySignals[j].getStationId() != id)) {

            if ( isInInterval( mySignals[j].getLeftPart().getStart(), start, end ) ) {
              mySignals[i].getRightPart().setCollisionFlag(true);
              if (!mySignals[i].getLeftPart().isSent())
               {
                mySignals[i].getLeftPart().setCollisionFlag(true);

               mySignals[j].getRightPart().setCollisionFlag(true);
					}
              	break;
            }
            if ( isInInterval( mySignals[j].getLeftPart().getEnd(), start, end ) ) {
              mySignals[i].getRightPart().setCollisionFlag(true);
              if (!mySignals[i].getLeftPart().isSent())
                {
                mySignals[i].getLeftPart().setCollisionFlag(true);
                             mySignals[j].getRightPart().setCollisionFlag(true);
}					break;
            }
            if ( isInInterval( mySignals[j].getRightPart().getStart(), start, end ) ) {
              mySignals[i].getRightPart().setCollisionFlag(true);
              if (!mySignals[i].getLeftPart().isSent())
               {
                mySignals[i].getLeftPart().setCollisionFlag(true);
                             mySignals[j].getRightPart().setCollisionFlag(true);
              }
              break;
            }
            if ( isInInterval( mySignals[j].getRightPart().getEnd(), start, end ) ) {
              mySignals[i].getRightPart().setCollisionFlag(true);
              if (!mySignals[i].getLeftPart().isSent())
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            {
                mySignals[i].getLeftPart().setCollisionFlag(true);
                            mySignals[j].getRightPart().setCollisionFlag(true);
		} break;
            }
          }
        }

      }
    }
  

  }

}

/*
 *
 */
class Station extends Thread {

	public static final int IDLE = 0;
	public static final int CARRIER_SENSE = 1;
	public static final int TRANSMIT = 2;
	public static final int BACKOFF = 3;


  Counter myCounter;

  Medium myMedium;
  Network myNetwork;

  int myBackoffCount;

  int myPosition;
  int myState;
  int myId;

  Random myRandom;


  boolean mySendRequest;

  public Station(int id, int position, Network network, Medium medium) {
    myPosition = position;
    myMedium = medium;
    myNetwork = network;
    myId = id;
    myState = IDLE;
    mySendRequest = false;
    myRandom = new Random(this.hashCode());
    this.start();
  }

  public void setSendRequest( boolean flag ) {
    mySendRequest = flag;
  }

  public int getState() {
    return myState;
  }

  public void setState(int x)
  {
  		myState=x;
  }
  
  public int getBackoffCount() {
    return myBackoffCount;
  }

  public int getBackoffRemain() {
    return myCounter.getCount();
  }

  public int getPosition() {
    return myPosition;
  }

  void sleep(int time) {
    try { 
      Thread.sleep(time); 
    } 
    catch (InterruptedException e) {