Bounded Buffer

Description

A classical bounded buffer composed of cells. The buffer is shared by a producer and a consumer. The producer can only write in an empty cell, and the consumer can only read a full cell. This version is deadlock free.

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Scripts

Screenshot of the interface

Design

Active Objects

• public String put(String str) - Put a string in the next free cell
• public String get() - Get the content of the first free cell

• public void toggle() - Starts/Stops the producer
• public void done() - Signals the producer to kill himself

• public void toggle() - Starts/Stops the consumer
• public void done() - Signals the consumer to kill himself

• public void start() - Initializes the Active objects
• public voiddone() - Stops every active object
• public void update(int pos,String str) - Sets the text of the cell pos to the value of str
• public void toggleCons() - Changes the states of the consumer
• public void toggleProd() - Changes the state of the produder
• public voidsetOut(int pos) - Sets the next cell to be written.
• public void setIn(int pos) - Sets the next cell to be read.

Object Graph

Class Interface Inheritance

Source Code

Main Parts

Bounded Buffer

This class is responsible for the whole synchronization of the application. Here is the synchronization code:

  /**
   * The only synchronization method
   */
  public void live(org.objectweb.proactive.Body body) {
    org.objectweb.proactive.Service service = new org.objectweb.proactive.Service(body);
    while (body.isActive()) {
      if (count == 0) {
        // if the buffer is empty
        service.blockingServeOldest("put"); // Serve the first buffer.put call
      } else if (count == size) {
        // if the buffer is full
        service.blockingServeOldest("get"); // Serve the first buffer.get call
      } else {
        // if the buffer is neither empty nor full
        service.blockingServeOldest(); // Serve the first buffer.xxx call
      }
    }
  }

Producer

The role of the producer is to fill the buffer's cells with data [String] in a synchronous way. The producer will fill one cell after another then pause for some time. The role of the consumer is to empty the buffer's cells in a synchronous way. The producer will read one cell after another then pause for some time.

  /**
   * The only synchronization method
   */
  public void live(org.objectweb.proactive.Body body) {
    org.objectweb.proactive.Service service = new org.objectweb.proactive.Service(body);
    while (isActive) {
      // Allow the display to toggle or kill the consumer
      service.serveOldest();
      boolean wasSuspended = isSuspended;
      if (requestChange) {
        isSuspended = !isSuspended;
        requestChange = false;
      }
      // Try to get some datas
      doStuff(wasSuspended);
      long l = 500 + (long)(Math.random() * 1000);
      //listener.displayMessage(name+" now sleeping for "+l+" ms");
      try {
        Thread.sleep(l);
      } catch (InterruptedException e) {}
    }
  }

Full Sources

Source code index