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;
}
}