Package it.unimi.di.law.bubing.util

Class ObjectDiskQueue<T>

java.lang.Object

it.unimi.di.law.bubing.util.ObjectDiskQueue<T>

All Implemented Interfaces:

Size64, java.io.Closeable, java.lang.AutoCloseable

public class ObjectDiskQueue<T>
extends java.lang.Object
implements java.io.Closeable, Size64

A queue of objects partially stored on disk.

This class is a wrapper around a ByteDiskQueue that provides methods to enqueue and dequeue() objects. Like a ByteDiskQueue, and instance of this class has a suspend() method that releases the file handle without deleting the dump file. The file handle is reinitialized lazily (which implies that a certain number of enqueue(Object)/dequeue() calls can be performed on a suspended class without actually reopening the dump file).

Similarly to a ByteDiskQueue, you can freeze() and then reopen a ObjectDiskQueue.

See Also:

ByteDiskQueue

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	ObjectDiskQueue(ByteDiskQueue byteDiskQueue)

Method Summary

Modifier and Type	Method	Description
void	clear()	Clears this queue.
void	close()	Closes this queue.
static <T> ObjectDiskQueue<T>	createFromFile(long size, java.io.File file, int bufferSize, boolean direct)	Creates a new disk-based queue of objects using an existing file.
static <T> ObjectDiskQueue<T>	createNew(java.io.File file, int bufferSize, boolean direct)	Creates a new disk-based queue of objects.
T	dequeue()	Dequeues an object from the queue in FIFO fashion.
void	enlargeBuffer(int newBufferSize)	Enlarge the buffer of this queue to a given size.
void	enqueue(T o)	Enqueues an object to this queue.
void	freeze()	Freezes this queue.
boolean	isEmpty()
int	size()	Deprecated.
long	size64()
void	suspend()	Suspends this queue.
void	trim()	Trims this queue.

Methods inherited from class java.lang.Object

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

Constructor Detail

ObjectDiskQueue

protected ObjectDiskQueue(ByteDiskQueue byteDiskQueue)

Method Detail

createNew

public static <T> ObjectDiskQueue<T> createNew(java.io.File file,
                                               int bufferSize,
                                               boolean direct)
                                        throws java.io.IOException

Creates a new disk-based queue of objects.

Parameters:

file - the file that will be used to dump the queue on disk.

bufferSize - the number of items in the circular buffer (will be possibly decreased so to be a power of two).

direct - whether the ByteBuffer used by this queue should be allocated directly.

Throws:

java.io.IOException

See Also:

ByteDiskQueue.createNew(File, int, boolean)

createFromFile

public static <T> ObjectDiskQueue<T> createFromFile(long size,
                                                    java.io.File file,
                                                    int bufferSize,
                                                    boolean direct)
                                             throws java.io.IOException

Creates a new disk-based queue of objects using an existing file.

Note that you have to supply the correct number of objects contained in the dump file of the underlying ByteDiskQueue. Failure to do so will cause unpredictable behaviour.

Parameters:

size - the number of objects contained in file.

file - the file that will be used to dump the queue on disk.

bufferSize - the number of items in the circular buffer (will be possibly decreased so to be a power of two).

direct - whether the ByteBuffer used by this queue should be allocated directly.

Throws:

java.io.IOException

See Also:

ByteDiskQueue.createFromFile(File, int, boolean)

enqueue

public void enqueue(T o)
             throws java.io.IOException

Enqueues an object to this queue.

Parameters:

o - the object to be enqueued.

Throws:

java.io.IOException

dequeue

public T dequeue()
          throws java.io.IOException

Dequeues an object from the queue in FIFO fashion.

Throws:

java.io.IOException

size

@Deprecated
public int size()

Deprecated.

Specified by:

size in interface Size64

size64

public long size64()

Specified by:

size64 in interface Size64

isEmpty

public boolean isEmpty()

close

public void close()
           throws java.io.IOException

Closes this queue.

Specified by:

close in interface java.lang.AutoCloseable

Specified by:

close in interface java.io.Closeable

Throws:

java.io.IOException

See Also:

ByteDiskQueue.close()

freeze

public void freeze()
            throws java.io.IOException

Freezes this queue.

Throws:

java.io.IOException

See Also:

ByteDiskQueue.freeze()

clear

public void clear()

Clears this queue.

See Also:

ByteDiskQueue.clear()

trim

public void trim()
          throws java.io.IOException

Trims this queue.

Throws:

java.io.IOException

See Also:

ByteDiskQueue.trim()

suspend

public void suspend()
             throws java.io.IOException

Suspends this queue.

Throws:

java.io.IOException

See Also:

ByteDiskQueue.suspend()

enlargeBuffer

public void enlargeBuffer(int newBufferSize)

Enlarge the buffer of this queue to a given size.

Parameters:

newBufferSize - the required buffer size.

See Also:

ByteDiskQueue.enlargeBuffer(int)