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

Class ByteArrayDiskQueue

java.lang.Object

it.unimi.di.law.bubing.util.ByteArrayDiskQueue

All Implemented Interfaces:

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

public class ByteArrayDiskQueue
extends java.lang.Object
implements java.io.Closeable, Size64

A queue of byte arrays partially stored on disk.

This class is a wrapper around a ByteDiskQueue that provides methods to enqueue and dequeue() byte arrays. 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(byte[])/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 ByteArrayDiskQueue.

See Also:

ByteDiskQueue

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	ByteArrayDiskQueue(ByteDiskQueue byteDiskQueue)

Method Summary

Modifier and Type	Method	Description
ByteArrayList	buffer()	Returns the current buffer of this byte-array disk queue.
void	clear()	Clears this queue.
void	close()	Closes this queue.
static ByteArrayDiskQueue	createFromFile(long size, java.io.File file, int bufferSize, boolean direct)	Creates a new disk-based queue of byte arrays using an existing file.
static ByteArrayDiskQueue	createNew(java.io.File file, int bufferSize, boolean direct)	Creates a new disk-based queue of byte arrays.
void	dequeue()	Dequeues a byte array from the queue in FIFO fashion.
void	enlargeBuffer(int newBufferSize)	Enlarge the buffer of this queue to a given size.
void	enqueue(byte[] array)	Enqueues a byte array to this queue.
void	enqueue(byte[] array, int offset, int length)	Enqueues a byte-array fragment 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

ByteArrayDiskQueue

protected ByteArrayDiskQueue(ByteDiskQueue byteDiskQueue)

Method Detail

createNew

public static ByteArrayDiskQueue createNew(java.io.File file,
                                           int bufferSize,
                                           boolean direct)
                                    throws java.io.IOException

Creates a new disk-based queue of byte arrays.

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 ByteArrayDiskQueue createFromFile(long size,
                                                java.io.File file,
                                                int bufferSize,
                                                boolean direct)
                                         throws java.io.IOException

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

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

Parameters:

size - the number of byte arrays 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(byte[] array)
             throws java.io.IOException

Enqueues a byte array to this queue.

Parameters:

array - the array to be enqueued.

Throws:

java.io.IOException

enqueue

public void enqueue(byte[] array,
                    int offset,
                    int length)
             throws java.io.IOException

Enqueues a byte-array fragment to this queue.

Parameters:

array - a byte array.

offset - the first valid byte in array.

length - the number of valid elements in array.

Throws:

java.io.IOException

dequeue

public void dequeue()
             throws java.io.IOException

Dequeues a byte array from the queue in FIFO fashion. The actual byte array will be stored in the queue buffer.

Throws:

java.io.IOException

buffer

public ByteArrayList buffer()

Returns the current buffer of this byte-array disk queue. The last dequeue() has filled this buffer with the result of the dequeue operation. Only the first k bytes, where k is the number returned by dequeue(), are valid.

Returns:

the current buffer of this byte-array disk queue.

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)