jcsp.util
Class OverWriteOldestBuffer

java.lang.Object
  |
  +--jcsp.util.OverWriteOldestBuffer

All Implemented Interfaces:

ChannelDataStore, Cloneable, Serializable

public class OverWriteOldestBuffer

extends Object

implements ChannelDataStore, Serializable

This is used to create a buffered object channel that always accepts input, overwriting its oldest data if full.

Description

OverWriteOldestBuffer is an implementation of ChannelDataStore that yields a FIFO buffered semantics for a channel. When empty, the channel blocks readers. When full, a writer will overwrite the oldest item left unread in the channel. See the static create methods of One2OneChannel etc.

The getState method returns EMPTY or NONEMPTYFULL, but never FULL.

Author:

P.D.Austin

See Also:

ZeroBuffer, Buffer, OverWritingBuffer, OverFlowingBuffer, InfiniteBuffer, One2OneChannel, Any2OneChannel, One2AnyChannel, Any2AnyChannel, Serialized Form

Fields inherited from interface jcsp.util.ChannelDataStore

EMPTY, FULL, NONEMPTYFULL

Constructor Summary

OverWriteOldestBuffer(int size)
Construct a new OverWriteOldestBuffer with the specified size.

Method Summary

Object	clone() Returns a new (and EMPTY) OverWriteOldestBuffer with the same creation parameters as this one.
Object	get() Returns the oldest Object from the OverWriteOldestBuffer and removes it.
int	getState() Returns the current state of the OverWriteOldestBuffer.
void	put(Object value) Puts a new Object into the OverWriteOldestBuffer.

Methods inherited from class java.lang.Object

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

Constructor Detail

OverWriteOldestBuffer

public OverWriteOldestBuffer(int size)

Construct a new OverWriteOldestBuffer with the specified size.

Parameters:

size - the number of Objects the OverWriteOldestBuffer can store.

Throws:

BufferSizeError - if size is zero or negative. Note: no action should be taken to try/catch this exception - application code generating it is in error and needs correcting.

Method Detail

get

public Object get()

Returns the oldest Object from the OverWriteOldestBuffer and removes it.

Pre-condition: getState must not currently return EMPTY.

Specified by:

get in interface ChannelDataStore

Returns:

the oldest Object from the OverWriteOldestBuffer

put

public void put(Object value)

Puts a new Object into the OverWriteOldestBuffer.

If OverWriteOldestBuffer is full, the oldest item left unread in the buffer will be overwritten.

Specified by:

put in interface ChannelDataStore

Parameters:

value - the Object to put into the OverWriteOldestBuffer

getState

public int getState()

Returns the current state of the OverWriteOldestBuffer.

Specified by:

getState in interface ChannelDataStore

Returns:

the current state of the OverWriteOldestBuffer (EMPTY or NONEMPTYFULL)

clone

public Object clone()

Returns a new (and EMPTY) OverWriteOldestBuffer with the same creation parameters as this one.

Note: Only the size and structure of the OverWriteOldestBuffer is cloned, not any stored data.

Specified by:

clone in interface ChannelDataStore

Overrides:

clone in class Object

Returns:

the cloned instance of this OverWriteOldestBuffer.