gbn.java

本程序用java编写的模拟的go-to-back网络传送

   repaint(); 
   nextseq++; 
   if (nextseq == base+window_len) 
    send.setEnabled(false); 
   start(); 
   } 
  
  else if (cmd == "fast")    // Faster button pressed 
   { 
   fps+=2; 
   statusMsg = "Simulation speed increased by 2 fps."; 
   } 
  
  else if (cmd == "slow" && fps>2) 
   { 
   fps-=2; 
   statusMsg = "Simulation speed decreased by 2 fps."; 
   } 
  
  else if (cmd == "stopanim") 
   { 
   gbnThread = null; 
   if (timerThread != null) 
    { 
    timerFlag = true; 
    timerThread = null;   // added later 
    } 
   stop.setLabel("Resume"); 
   stop.setActionCommand("startanim"); 
  
   // disableing all the buttons 
   send.setEnabled(false); 
   slow.setEnabled(false); 
   fast.setEnabled(false); 
   kill.setEnabled(false); 
  
   statusMsg = "Simulation paused."; 
   repaint(); 
   } 
  
  else if (cmd == "startanim") 
   { 
   statusMsg = "Simulation resumed."; 
   stop.setLabel("Stop Animation"); 
   stop.setActionCommand("stopanim"); 
   if (timerFlag) 
    { 
    statusMsg += " Timer running."; 
    timerThread = new Thread(this); 
    timerSleep = true; 
    timerThread.start(); 
    } 
  
   // enabling the buttons 
   send.setEnabled(true); 
   slow.setEnabled(true); 
   fast.setEnabled(true); 
   kill.setEnabled(true); 
   repaint();    // repainted to show new messages 
  
   start(); 
   } 
  
  else if (cmd == "kl") 
   { 
   if (sender[selected].packet_ack) 
    statusMsg = "Packet "+ selected +" destroyed. Timer running for packet "+base+"."; 
   else 
    statusMsg = "Acknowledgement of packet "+ selected +" destroyed. Timer running for packet "+base+"."; 
  
   sender[selected].on_way = false; 
   kill.setEnabled(false); 
   selected = -1; 
   repaint(); 
   } 
  
  else if (cmd == "rst") 
   reset_app(); 
  } 

  
 public boolean mouseDown(Event e, int x, int y) 
  { 
  int i, xpos, ypos; 
  i = (x-h_offset)/(pack_width+7); 
  if (sender[i]!= null) 
   { 
   xpos = h_offset+(pack_width+7)*i; 
   ypos = sender[i].packet_pos; 
  
   if (x>=xpos && x<= xpos+pack_width && sender[i].on_way) 
    { 
    if ((sender[i].packet_ack && y>=v_offset+ypos && y<=v_offset+ypos+pack_height) || ((!sender[i].packet_ack) && y>=v_offset+v_clearance-ypos && y<=v_offset+v_clearance-ypos+pack_height)) 
     { 
     statusMsg = "Packet "+ i +" selected."; 
     sender[i].selected = true; 
     selected = i; 
     kill.setEnabled(true); 
     } 
    else 
     statusMsg = "Click on a moving packet to select."; 
    } 
   else 
    statusMsg = "Click on a moving packet to select."; 
   } 
  return true; 
  } 
  

 public void paint(Graphics g)    // To eliminate flushing, update is overriden 
  { 
  update(g); 
  } 
  
  
 public void update(Graphics g) 
  { 
  Dimension d = size(); 
  
  //Create the offscreen graphics context, if no good one exists. 
        if ((offGraphics == null) || (d.width != offDimension.width) || (d.height != offDimension.height)) 
   { 
            offDimension = d; 
            offImage = createImage(d.width, d.height); 
            offGraphics = offImage.getGraphics(); 
   } 
  
  //Erase the previous image. 
        offGraphics.setColor(Color.white); 
        offGraphics.fillRect(0, 0, d.width, d.height); 
  
  //drawing window 
  
  
  offGraphics.setColor(Color.black); 
  offGraphics.draw3DRect(h_offset+base*(pack_width+7)-4, v_offset-3, (window_len)*(pack_width+7)+1, pack_height+6,true); 
  
  
  for (int i=0; i<total_packet; i++) 
   { 
   // drawing the sending row 
  
   if (sender[i]==null) 
    { 
    offGraphics.setColor(Color.black); 
    offGraphics.draw3DRect(h_offset+(pack_width+7)*i, v_offset, pack_width,pack_height,true); 
    offGraphics.draw3DRect(h_offset+(pack_width+7)*i, v_offset+v_clearance, pack_width,pack_height,true); 
    } 
   else 
    { 
    if (sender[i].acknowledged) 
     offGraphics.setColor(ack_color); 
    else 
     offGraphics.setColor(unack_color); 
    offGraphics.fill3DRect (h_offset+(pack_width+7)*i, v_offset,pack_width,pack_height,true); 
  
  
    // drawing the destination packets 
  
    offGraphics.setColor (dest_color); 
    if (sender[i].reached_dest) 
     offGraphics.fill3DRect (h_offset+(pack_width+7)*i, v_offset+v_clearance,pack_width,pack_height,true); 
    else 
     offGraphics.draw3DRect (h_offset+(pack_width+7)*i, v_offset+v_clearance,pack_width,pack_height,true); 
  
    // drawing the moving packets 
  
    if (sender[i].on_way) 
     { 
     if (i==selected) 
      offGraphics.setColor (sel_color); 
     else if (sender[i].packet_ack) 
      offGraphics.setColor (roam_pack_color); 
     else 
      offGraphics.setColor (roam_ack_color); 
  
     if (sender[i].packet_ack) 
      offGraphics.fill3DRect (h_offset+(pack_width+7)*i, v_offset+sender[i].packet_pos,pack_width,pack_height,true); 
     else 
      offGraphics.fill3DRect (h_offset+(pack_width+7)*i, v_offset+v_clearance-sender[i].packet_pos,pack_width,pack_height,true); 
     } 
    } 
   }   // for loop ends 
  
   // drawing message boxes 
  
   offGraphics.setColor(Color.black); 
   int newvOffset = v_offset+v_clearance+pack_height; 
   int newHOffset = h_offset; 
  
   offGraphics.drawString(statusMsg,newHOffset,newvOffset+25); 
   //offGraphics.drawString(strCurrentValues,newHOffset,newvOffset+40); 
  
   offGraphics.drawString("Packet",newHOffset+15,newvOffset+60); 
   offGraphics.drawString("Acknowledge",newHOffset+85,newvOffset+60); 
   offGraphics.drawString("Received Pack",newHOffset+185,newvOffset+60); 
   offGraphics.drawString("Selected",newHOffset+295,newvOffset+60); 
  
   offGraphics.drawString("Base = "+base,h_offset+(pack_width+7)*total_packet+10,v_offset+v_clearance/2); 
   offGraphics.drawString("NextSeq = "+nextseq,h_offset+(pack_width+7)*total_packet+10,v_offset+v_clearance/2+20); 
  
   offGraphics.setColor(Color.blue); 
   offGraphics.drawString("Sender",h_offset+(pack_width+7)*total_packet+10,v_offset+12); 
   offGraphics.drawString("Receiver",h_offset+(pack_width+7)*total_packet+10,v_offset+v_clearance+12); 
  
   offGraphics.setColor(Color.gray); 
   offGraphics.draw3DRect(newHOffset-10,newvOffset+42,360,25,true); 
  
   offGraphics.setColor(Color.red); 
   offGraphics.draw3DRect(h_offset+(pack_width+7)*total_packet+5,v_offset+v_clearance/2-15,80,40,true); 
  
   offGraphics.setColor(roam_pack_color); 
   offGraphics.fill3DRect(newHOffset, newvOffset+50,10,10,true); 
  
   offGraphics.setColor(roam_ack_color); 
   offGraphics.fill3DRect(newHOffset+70, newvOffset+50,10,10,true); 
  
   offGraphics.setColor(dest_color); 
   offGraphics.fill3DRect(newHOffset+170, newvOffset+50,10,10,true); 
  
   offGraphics.setColor(sel_color); 
   offGraphics.fill3DRect(newHOffset+280, newvOffset+50,10,10,true); 
  
  
  g.drawImage(offImage, 0, 0, this); 
  }    // method paint ends 
  
  
 // checks out if an array is on the way to source or destination 
  
 public boolean onTheWay(packet pac[]) 
  { 
  for (int i=0; i<pac.length; i++) 
   if (pac[i] == null) 
    return false; 
   else if (pac[i].on_way) return true; 
  return false; 
  } 
  
 // checkes all the packets before packno. Returns false if any packet has 
 // not reached destination and true if all the packets have reached destination. 
  
 public boolean check_upto_n(int packno) 
  { 
  for (int i=0; i<packno; i++) 
   if (!sender[i].reached_dest) 
    return false; 
  return true; 
  } 
  
 public void reset_app() 
  { 
  for (int i=0; i<total_packet; i++) 
   if (sender[i] != null) 
    sender[i] = null; 
  base = 0; 
  nextseq = 0; 
  selected = -1; 
  fps = 5; 
  timerFlag = false; 
  timerSleep = false; 
  gbnThread = null; 
  timerThread = null; 
  if(stop.getActionCommand()=="startanim")  // in case of pause mode, enable all buttons 
   { 
   slow.setEnabled(true); 
   fast.setEnabled(true); 
   } 
  
  send.setEnabled(true); 
  kill.setEnabled(false); 
  
  stop.setLabel("Stop Animation"); 
  stop.setActionCommand("stopanim"); 
  statusMsg = "Simulation restarted. Press 'Send New' to start."; 
  repaint(); 
  } 

  
 }