Package EDU.oswego.cs.dl.util.concurrent

Class BoundedBuffer

java.lang.Object

EDU.oswego.cs.dl.util.concurrent.BoundedBuffer

All Implemented Interfaces:

BoundedChannel, Channel, Puttable, Takable

public class BoundedBuffer
extends Object
implements BoundedChannel

Efficient array-based bounded buffer class. Adapted from CPJ, chapter 8, which describes design.

[ Introduction to this package. ]

Field Summary

Fields

Modifier and Type	Field	Description
protected Object[]	array_
protected int	emptySlots_
protected Object	putMonitor_	Helper monitor to handle puts.
protected int	putPtr_
protected int	takePtr_
protected int	usedSlots_

Constructor Summary

Constructors

Constructor	Description
BoundedBuffer()	Create a buffer with the current default capacity
BoundedBuffer(int capacity)	Create a BoundedBuffer with the given capacity.

Method Summary

Modifier and Type	Method	Description
int	capacity()	Return the maximum number of elements that can be held.
protected Object	extract()
protected void	incEmptySlots()
protected void	incUsedSlots()
protected void	insert(Object x)
boolean	offer(Object x, long msecs)	Place item in channel only if it can be accepted within msecs milliseconds.
Object	peek()	Return, but do not remove object at head of Channel, or null if it is empty.
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.

Methods inherited from class java.lang.Object

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

Field Detail

array_

protected final Object[] array_

takePtr_

protected int takePtr_

putPtr_

protected int putPtr_

usedSlots_

protected int usedSlots_

emptySlots_

protected int emptySlots_

putMonitor_

protected final Object putMonitor_

Helper monitor to handle puts.

Constructor Detail

BoundedBuffer

public BoundedBuffer(int capacity)
              throws IllegalArgumentException

Create a BoundedBuffer with the given capacity.

Throws:

IllegalArgumentException - if capacity less or equal to zero

BoundedBuffer

public BoundedBuffer()

Create a buffer with the current default capacity

Method Detail

size

public int size()

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

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.

incEmptySlots

protected void incEmptySlots()

incUsedSlots

protected void incUsedSlots()

insert

protected final void insert(Object x)

extract

protected final Object extract()

peek

public Object peek()

Description copied from interface: Channel

Return, but do not remove object at head of Channel, or null if it is empty.

Specified by:

peek in interface Channel

put

public void put(Object x)
         throws 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:

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(Object x,
                     long msecs)
              throws 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:

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 Object take()
            throws 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:

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 Object poll(long msecs)
            throws 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:

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).