EDU.oswego.cs.dl.util.concurrent

Class SemaphoreControlledChannel

Implemented Interfaces:
BoundedChannel, Channel, Puttable, Takable
Known Direct Subclasses:
BoundedPriorityQueue, PipedChannel, 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, 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 Object
extract()
Internal mechanics of take.
protected abstract void
insert(Object x)
Internal mechanics of put.
boolean
offer(Object x, long msecs)
Place item in channel only if it can be accepted within msecs milliseconds.
Object
poll(long msecs)
Return and remove an item from channel only if one is available within msecs milliseconds.
void
put(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.
Object
take()
Return and remove an item from channel, possibly waiting indefinitely until such an item exists.

Field Details

capacity_

protected int capacity_

putGuard_

protected final Semaphore putGuard_

takeGuard_

protected final Semaphore takeGuard_

Constructor Details

SemaphoreControlledChannel

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

SemaphoreControlledChannel

public SemaphoreControlledChannel(int capacity,
                                  Class semaphoreClass)
            throws IllegalArgumentException,
                   NoSuchMethodException,
                   SecurityException,
                   InstantiationException,
                   IllegalAccessException,
                   InvocationTargetException
Create a channel with the given capacity and semaphore implementations instantiated from the supplied class

Method Details

capacity

public int capacity()
Return the maximum number of elements that can be held.
Specified by:
capacity in interface BoundedChannel
Returns:
the capacity of this channel.

extract

protected abstract Object extract()
Internal mechanics of take.

insert

protected abstract void insert(Object x)
Internal mechanics of put.

offer

public boolean offer(Object x,
                     long msecs)
            throws InterruptedException
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
offer in interface Puttable
Parameters:
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

poll

public Object poll(long msecs)
            throws InterruptedException
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
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.

put

public void put(Object x)
            throws InterruptedException
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
put in interface Puttable
Parameters:

size

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

take

public Object take()
            throws InterruptedException
Return and remove an item from channel, possibly waiting indefinitely until such an item exists.
Specified by:
take in interface Channel
take in interface Takable
Returns:
some item from the channel. Different implementations may guarantee various properties (such as FIFO) about that item