src/edu/berkeley/fleet/InstructionPort.java

   1 package edu.berkeley.fleet;
   2
   3 import java.util.*;
   4
   5 /** common superclass for any port which can take an instruction: inbox/outbox/tokenoutbox */
   6 public abstract class InstructionPort extends Port {
   7
   8     public InstructionPort(Ship ship, String name) {
   9         super(ship, name);
  10     }
  11
  12     /** add an instruction to the box */
  13     public void addInstruction(Instruction instr) {
  14         if (currentlyExecuting != null && currentlyExecuting.count == Integer.MAX_VALUE) {
  15             currentlyExecuting = null;
  16             currentlyExecutingCount = 0;
  17         }
  18         if (currentlyExecuting == null) {
  19             currentlyExecuting = instr;
  20             currentlyExecutingCount = currentlyExecuting.count;
  21         } else {
  22             instructions.add(instr);
  23         }
  24     }
  25
  26     // inherited from Port
  27     public abstract void addData(int data);
  28
  29     private Instruction currentlyExecuting = null;
  30     private Queue<Instruction> instructions = new LinkedList<Instruction>();
  31     private int currentlyExecutingCount;
  32
  33     // interface to subclass ///////////////////////////////////////////////////////////////////////
  34
  35     /** this will be invoked periodically; should return true to "consume" an instruction */
  36     protected abstract boolean service(Instruction instr);
  37
  38     public void service() {
  39         if (currentlyExecutingCount <= 0)
  40             currentlyExecuting = null;
  41         if (currentlyExecuting == null && instructions.size() > 0) {
  42             currentlyExecuting = instructions.remove();
  43             currentlyExecutingCount = currentlyExecuting.count;
  44         }
  45         boolean ret = service(currentlyExecuting);
  46         if (ret && currentlyExecuting != null && currentlyExecutingCount != Integer.MAX_VALUE)
  47             currentlyExecutingCount--;
  48     }
  49
  50
  51 }