org.archive.queue
Class TieredQueue

java.lang.Object
  org.archive.queue.TieredQueue

All Implemented Interfaces:

Queue

public class TieredQueue
extends java.lang.Object
implements Queue

A queue with multiple internal queues, numbered 0 to n. Dequeues come from lower-numbered queues before higher-numbered queues. The standard enqueue() places an item at the back of the highest-numbered queue. Other variants of enqueue place items on specific queues. A peek() guarantees that the item returned by peek() will be returned by the next dequeue(), even if other items are enqueued to lower-numbered internal queues in the meantime. (The unpeek() may be used to release the TieredQueue from this guarantee; the next peek()/dequeue() will then return the item available from the lowest-numbered queue.)

Author:

gojomo

Field Summary

(package private) java.lang.Object	headObject
(package private) int	headSource
(package private) Queue[]	innerQueues
(package private) int	lastQueue
(package private) long	length

Constructor Summary

TieredQueue(int tiers)
Create a TieredQueue with the given number of internal queue slots.

Method Summary

long	deleteMatchedItems(org.apache.commons.collections.Predicate matcher) All objects in the queue where matcher.match(object) returns true will be deleted from the queue.
java.lang.Object	dequeue() remove an entry from the start of the queue
void	enqueue(java.lang.Object obj) Add an entry to the end of queue
void	enqueue(java.lang.Object obj, int tier) Enqueue the object to the given tier.
java.util.Iterator	getIterator(boolean inCacheOnly) Returns an iterator for the queue.
void	initializeDiskBackedQueues(java.io.File scratchDir, java.lang.String tmpName, int inMemCap) Initialize all innerQueues to be DiskBackedQueues in the given scratch directory, using the tmpName prefix.
boolean	isEmpty() is the queue empty?
long	length() get the number of elements in the queue
java.lang.Object	peek() Give the top object in the queue, leaving it in place to be returned by future peek() or dequeue() invocations.
void	release() release any OS/IO resources associated with Queue
void	setMemoryResidentQueueCap(int inMemCap) Set the total number of in-memory items, assuming the underlying subqueues are DiskBackedQueue instances.
void	setQueue(int tier, Queue q) Set the internal queue tier to be the supplied Queue instance.
void	unpeek() Releases queue from the obligation to return in the next peek()/dequeue() the same object as returned by any previous peek().

Methods inherited from class java.lang.Object

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

Field Detail

headObject

java.lang.Object headObject

headSource

int headSource

innerQueues

Queue[] innerQueues

lastQueue

int lastQueue

length

long length

Constructor Detail

TieredQueue

public TieredQueue(int tiers)

Create a TieredQueue with the given number of internal queue slots.

Method Detail

enqueue

public void enqueue(java.lang.Object obj)

Description copied from interface: Queue

Add an entry to the end of queue

Specified by:

enqueue in interface Queue

Parameters:

obj - the entry to queue

enqueue

public void enqueue(java.lang.Object obj,
                    int tier)

Enqueue the object to the given tier.

isEmpty

public boolean isEmpty()

Description copied from interface: Queue

is the queue empty?

Specified by:

isEmpty in interface Queue

Returns:

true if the queue has no elements

dequeue

public java.lang.Object dequeue()
                         throws java.util.NoSuchElementException

Description copied from interface: Queue

remove an entry from the start of the queue

Specified by:

dequeue in interface Queue

Returns:

the object

Throws:

java.util.NoSuchElementException

length

public long length()

Description copied from interface: Queue

get the number of elements in the queue

Specified by:

length in interface Queue

Returns:

the number of elements in the queue

release

public void release()

Description copied from interface: Queue

release any OS/IO resources associated with Queue

Specified by:

release in interface Queue

peek

public java.lang.Object peek()

Description copied from interface: Queue

Give the top object in the queue, leaving it in place to be returned by future peek() or dequeue() invocations.

Specified by:

peek in interface Queue

Returns:

top object, without removing it

unpeek

public void unpeek()

Description copied from interface: Queue

Releases queue from the obligation to return in the next peek()/dequeue() the same object as returned by any previous peek().

Specified by:

unpeek in interface Queue

setQueue

public void setQueue(int tier,
                     Queue q)

Set the internal queue tier to be the supplied Queue instance.

Parameters:

tier - Tier level to set.

q - Queue to use.

getIterator

public java.util.Iterator getIterator(boolean inCacheOnly)

Description copied from interface: Queue

Returns an iterator for the queue.

The returned iterator's remove method is considered unsafe.

Editing the queue while using the iterator is not safe.

Specified by:

getIterator in interface Queue

Returns:

an iterator for the queue

deleteMatchedItems

public long deleteMatchedItems(org.apache.commons.collections.Predicate matcher)

Description copied from interface: Queue

All objects in the queue where matcher.match(object) returns true will be deleted from the queue.

Making other changes to the queue while this method is being processed is not safe.

Specified by:

deleteMatchedItems in interface Queue

Parameters:

matcher - a predicate

Returns:

the number of deleted items

initializeDiskBackedQueues

public void initializeDiskBackedQueues(java.io.File scratchDir,
                                       java.lang.String tmpName,
                                       int inMemCap)
                                throws java.io.IOException

Initialize all innerQueues to be DiskBackedQueues in the given scratch directory, using the tmpName prefix.

Parameters:

scratchDir - Directory to put tmp files in.

tmpName - Prefix to use in tmpnames.

Throws:

java.io.IOException

setMemoryResidentQueueCap

public void setMemoryResidentQueueCap(int inMemCap)

Set the total number of in-memory items, assuming the underlying subqueues are DiskBackedQueue instances.

Parameters:

inMemCap - Memory cap.