uk.org.ogsadai.common
Class CircularBuffer

java.lang.Object
  |
  +--uk.org.ogsadai.common.CircularBuffer

public class CircularBuffer

extends java.lang.Object

A thread-safe, fixed-sized, circular buffer that can be written to by a producer and read from by a consumer. The producer can close the buffer to indicate that no more blocks will be written.

Author:

The OGSA-DAI Project Team

Field Summary

private static java.lang.String	COPYRIGHT_NOTICE
private static int	DEFAULT_SIZE
private java.lang.Object[]	mBuffer
private boolean	mOpen
private int	mReadIndex
private int	mWriteIndex

Constructor Summary

CircularBuffer()
Construct a circular buffer with the default buffer size.

CircularBuffer(int size)
Construct a circular buffer with the specified buffer size.

Method Summary

private int	blocksAvailable() Return the number of blocks that are available to be read from the buffer.
void	close() Close the circular buffer indicating that no more blocks will be written to it.
private int	freeSpace() Return the number of free spaces in the buffer available for writing to.
java.lang.Object	read() Read an object from the buffer.
void	write(java.lang.Object block) Write an object to the buffer.

Methods inherited from class java.lang.Object

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

Field Detail

COPYRIGHT_NOTICE

private static final java.lang.String COPYRIGHT_NOTICE

See Also:

Constant Field Values

DEFAULT_SIZE

private static final int DEFAULT_SIZE

See Also:

Constant Field Values

mBuffer

private final java.lang.Object[] mBuffer

mReadIndex

private volatile int mReadIndex

mWriteIndex

private volatile int mWriteIndex

mOpen

private boolean mOpen

Constructor Detail

CircularBuffer

public CircularBuffer()

Construct a circular buffer with the default buffer size.

CircularBuffer

public CircularBuffer(int size)

Construct a circular buffer with the specified buffer size.

Parameters:

size - The number of blocks that the buffer can contain.

Method Detail

read

public java.lang.Object read()
                      throws java.lang.InterruptedException

Read an object from the buffer. If no blocks are available to read the method blocks until a block becomes available or the buffer is closed. If the buffer is closed then a null block is returned.

Returns:

The next block Object or null if the buffer is closed.

Throws:

java.lang.InterruptedException - if the thread is interrupted.

write

public void write(java.lang.Object block)
           throws java.lang.InterruptedException

Write an object to the buffer. If the buffer is full then the method blocks until space becomes available to write the block.

Parameters:

block - The block of data.

Throws:

java.lang.InterruptedException - if the thread is interrupted.

java.lang.IllegalStateException - if the buffer has been closed.

close

public void close()

Close the circular buffer indicating that no more blocks will be written to it.

freeSpace

private int freeSpace()

Return the number of free spaces in the buffer available for writing to.

Returns:

number of free spaces.

blocksAvailable

private int blocksAvailable()

Return the number of blocks that are available to be read from the buffer. Should always be called from within a synchronized block of another method.

Returns:

The number of characters remaining to be read.