EDU.oswego.cs.dl.util.concurrent
Class SemaphoreControlledChannel

java.lang.Object
  EDU.oswego.cs.dl.util.concurrent.SemaphoreControlledChannel

All Implemented Interfaces:

BoundedChannel, Channel, Puttable, Takable

Direct Known Subclasses:

BoundedPriorityQueue, Slot

public abstract class SemaphoreControlledChannel
extends java.lang.Object
implements BoundedChannel

Abstract class for channels that use Semaphores to control puts and takes.

[ Introduction to this package. ]

Field Summary

protected int	capacity_
protected Semaphore	putGuard_
protected Semaphore	takeGuard_

Constructor Summary

SemaphoreControlledChannel(int capacity)
Create a channel with the given capacity and default semaphore implementation

SemaphoreControlledChannel(int capacity, java.lang.Class semaphoreClass)
Create a channel with the given capacity and semaphore implementations instantiated from the supplied class

Method Summary

int	capacity() Return the maximum number of elements that can be held.
protected abstract java.lang.Object	extract() Internal mechanics of take.
protected abstract void	insert(java.lang.Object x) Internal mechanics of put.
boolean	offer(java.lang.Object x, long msecs) Place item in channel only if it can be accepted within msecs milliseconds.
java.lang.Object	poll(long msecs) Return and remove an item from channel only if one is available within msecs milliseconds.
void	put(java.lang.Object x) Place item in the channel, possibly waiting indefinitely until it can be accepted.
int	size() Return the number of elements in the buffer.
java.lang.Object	take() Return and remove an item from channel, possibly waiting indefinitely until such an item exists.

Methods inherited from class java.lang.Object

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

Methods inherited from interface EDU.oswego.cs.dl.util.concurrent.Channel

peek

Field Detail

putGuard_

protected final Semaphore putGuard_

takeGuard_

protected final Semaphore takeGuard_

capacity_

protected int capacity_

Constructor Detail

SemaphoreControlledChannel

public SemaphoreControlledChannel(int capacity)
                           throws java.lang.IllegalArgumentException

Create a channel with the given capacity and default semaphore implementation

Throws:

java.lang.IllegalArgumentException - if capacity less or equal to zero

SemaphoreControlledChannel

public SemaphoreControlledChannel(int capacity,
                                  java.lang.Class semaphoreClass)
                           throws java.lang.IllegalArgumentException,
                                  java.lang.NoSuchMethodException,
                                  java.lang.SecurityException,
                                  java.lang.InstantiationException,
                                  java.lang.IllegalAccessException,
                                  java.lang.reflect.InvocationTargetException

Create a channel with the given capacity and semaphore implementations instantiated from the supplied class

Throws:

java.lang.IllegalArgumentException - if capacity less or equal to zero.

java.lang.NoSuchMethodException - If class does not have constructor that intializes permits

java.lang.SecurityException - if constructor information not accessible

java.lang.InstantiationException - if semaphore class is abstract

java.lang.IllegalAccessException - if constructor cannot be called

java.lang.reflect.InvocationTargetException - if semaphore constructor throws an exception

Method Detail

capacity

public int capacity()

Description copied from interface: BoundedChannel

Return the maximum number of elements that can be held.

Specified by:

capacity in interface BoundedChannel

Returns:

the capacity of this channel.

size

public int size()

Return the number of elements in the buffer. This is only a snapshot value, that may change immediately after returning.

insert

protected abstract void insert(java.lang.Object x)

Internal mechanics of put.

extract

protected abstract java.lang.Object extract()

Internal mechanics of take.

put

public void put(java.lang.Object x)
         throws java.lang.InterruptedException

Description copied from interface: Channel

Place item in the channel, possibly waiting indefinitely until it can be accepted. Channels implementing the BoundedChannel subinterface are generally guaranteed to block on puts upon reaching capacity, but other implementations may or may not block.

Specified by:

put in interface Channel

Specified by:

put in interface Puttable

Parameters:

x - the element to be inserted. Should be non-null.

Throws:

java.lang.InterruptedException - if the current thread has been interrupted at a point at which interruption is detected, in which case the element is guaranteed not to be inserted. Otherwise, on normal return, the element is guaranteed to have been inserted.

offer

public boolean offer(java.lang.Object x,
                     long msecs)
              throws java.lang.InterruptedException

Description copied from interface: Channel

Place item in channel only if it can be accepted within msecs milliseconds. The time bound is interpreted in a coarse-grained, best-effort fashion.

Specified by:

offer in interface Channel

Specified by:

offer in interface Puttable

Parameters:

x - the element to be inserted. Should be non-null.

msecs - the number of milliseconds to wait. If less than or equal to zero, the method does not perform any timed waits, but might still require access to a synchronization lock, which can impose unbounded delay if there is a lot of contention for the channel.

Returns:

true if accepted, else false

Throws:

java.lang.InterruptedException - if the current thread has been interrupted at a point at which interruption is detected, in which case the element is guaranteed not to be inserted (i.e., is equivalent to a false return).

take

public java.lang.Object take()
                      throws java.lang.InterruptedException

Description copied from interface: Channel

Return and remove an item from channel, possibly waiting indefinitely until such an item exists.

Specified by:

take in interface Channel

Specified by:

take in interface Takable

Returns:

some item from the channel. Different implementations may guarantee various properties (such as FIFO) about that item

Throws:

java.lang.InterruptedException - if the current thread has been interrupted at a point at which interruption is detected, in which case state of the channel is unchanged.

poll

public java.lang.Object poll(long msecs)
                      throws java.lang.InterruptedException

Description copied from interface: Channel

Return and remove an item from channel only if one is available within msecs milliseconds. The time bound is interpreted in a coarse grained, best-effort fashion.

Specified by:

poll in interface Channel

Specified by:

poll in interface Takable

Parameters:

msecs - the number of milliseconds to wait. If less than or equal to zero, the operation does not perform any timed waits, but might still require access to a synchronization lock, which can impose unbounded delay if there is a lot of contention for the channel.

Returns:

some item, or null if the channel is empty.

Throws:

java.lang.InterruptedException - if the current thread has been interrupted at a point at which interruption is detected, in which case state of the channel is unchanged (i.e., equivalent to a null return).