Overview  Package   Class  Use  Deprecated  Index
Home >> All >> org >> ematgine >> utils >> [ concurrent overview ]	PREV CLASS  NEXT CLASS
SUMMARY:  JAVADOC |  SOURCE |  DOWNLOAD | NESTED | FIELD | CONSTR | METHOD	DETAIL: FIELD | CONSTR | METHOD

---

org.ematgine.utils.concurrent
Class CondVar  

java.lang.Object
  org.ematgine.utils.concurrent.CondVar

---

public class CondVar

extends java.lang.Object

This class is designed for fans of POSIX pthreads programming. If you restrict yourself to Mutexes and CondVars, you can use most of your favorite constructions. Don't randomly mix them with synchronized methods or blocks though.

Method names and behavior are as close as is reasonable to those in POSIX.

Sample Usage. Here is a full version of a bounded buffer that implements the BoundedChannel interface, written in a style reminscent of that in POSIX programming books.

 class CVBuffer implements BoundedChannel {
   private final Mutex mutex;
   private final CondVar notFull;
   private final CondVar notEmpty;
   private int count = 0;
   private int takePtr = 0;     
   private int putPtr = 0;
   private final Object[] array;
 
   public CVBuffer(int capacity) { 
     array = new Object[capacity];
     mutex = new Mutex();
     notFull = new CondVar(mutex);
     notEmpty = new CondVar(mutex);
   }
 
   public int capacity() { return array.length; }
 
   public void put(Object x) throws InterruptedException {
     mutex.acquire();
     try {
       while (count == array.length) {
         notFull.await();
       }
       array[putPtr] = x;
       putPtr = (putPtr + 1) % array.length;
       ++count;
       notEmpty.signal();
     }
     finally {
       mutex.release();
     }
   }
 
   public Object take() throws InterruptedException {
     Object x = null;
     mutex.acquire();
     try {
       while (count == 0) {
         notEmpty.await();
       }
       x = array[takePtr];
       array[takePtr] = null;
       takePtr = (takePtr + 1) % array.length;
       --count;
       notFull.signal();
     }
     finally {
       mutex.release();
     }
     return x;
   }
 
   public boolean offer(Object x, long msecs) throws InterruptedException {
     mutex.acquire();
     try {
       if (count == array.length) {
         notFull.timedwait(msecs);
         if (count == array.length)
           return false;
       }
       array[putPtr] = x;
       putPtr = (putPtr + 1) % array.length;
       ++count;
       notEmpty.signal();
       return true;
     }
     finally {
       mutex.release();
     }
   }
   
   public Object poll(long msecs) throws InterruptedException {
     Object x = null;
     mutex.acquire();
     try {
       if (count == 0) {
         notEmpty.timedwait(msecs);
         if (count == 0)
           return null;
       }
       x = array[takePtr];
       array[takePtr] = null;
       takePtr = (takePtr + 1) % array.length;
       --count;
       notFull.signal();
     }
     finally {
       mutex.release();
     }
     return x;
   }
 }

 

---

Field Summary
protected  Sync	mutex_           The mutex

 

Constructor Summary

CondVar(Sync mutex)           Create a new CondVar that relies on the given mutual exclusion lock.

 

Method Summary
void	await()           Wait for notification.
void	broadcast()           Notify all waiting threads
void	signal()           Notify a waiting thread.
boolean	timedwait(long msecs)           Wait for at most msecs for notification.

 

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

 

Field Detail

mutex_

protected final Sync mutex_

The mutex

Constructor Detail

CondVar

public CondVar(Sync mutex)

Create a new CondVar that relies on the given mutual exclusion lock.

Method Detail

await

public void await()
           throws java.lang.InterruptedException

Wait for notification. This operation at least momentarily releases the mutex. The mutex is always held upon return, even if interrupted.

---

timedwait

public boolean timedwait(long msecs)
                  throws java.lang.InterruptedException

Wait for at most msecs for notification. This operation at least momentarily releases the mutex. The mutex is always held upon return, even if interrupted.

---

signal

public void signal()

Notify a waiting thread. If one exists, a non-interrupted thread will return normally (i.e., not via InterruptedException) from await or timedwait.

---

broadcast

public void broadcast()

Notify all waiting threads

---

Overview  Package   Class  Use  Deprecated  Index
Home >> All >> org >> ematgine >> utils >> [ concurrent overview ]	PREV CLASS  NEXT CLASS
SUMMARY:  JAVADOC |  SOURCE |  DOWNLOAD | NESTED | FIELD | CONSTR | METHOD	DETAIL: FIELD | CONSTR | METHOD

---