jcsp.util
Class OverWritingBuffer

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

All Implemented Interfaces:

ChannelDataStore, Cloneable, Serializable

public class OverWritingBuffer

extends Object

implements ChannelDataStore, Serializable

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

Description

It 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 latest item written to 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, OverWriteOldestBuffer, OverFlowingBuffer, InfiniteBuffer, One2OneChannel, Any2OneChannel, One2AnyChannel, Any2AnyChannel, Serialized Form

Fields inherited from interface jcsp.util.ChannelDataStore

EMPTY, FULL, NONEMPTYFULL

Constructor Summary

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

Method Summary

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

Methods inherited from class java.lang.Object

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

Constructor Detail

OverWritingBuffer

public OverWritingBuffer(int size)

Construct a new OverWritingBuffer with the specified size.

Parameters:

size - the number of Objects the OverWritingBuffer 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 OverWritingBuffer and removes it.

Pre-condition: getState must not currently return EMPTY.

Specified by:

get in interface ChannelDataStore

Returns:

the oldest Object from the OverWritingBuffer

put

public void put(Object value)

Puts a new Object into the OverWritingBuffer.

If OverWritingBuffer is full, the last item previously put into the buffer will be overwritten.

Specified by:

put in interface ChannelDataStore

Parameters:

value - the Object to put into the OverWritingBuffer

getState

public int getState()

Returns the current state of the OverWritingBuffer.

Specified by:

getState in interface ChannelDataStore

Returns:

the current state of the OverWritingBuffer (EMPTY or NONEMPTYFULL)

clone

public Object clone()

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

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

Specified by:

clone in interface ChannelDataStore

Overrides:

clone in class Object

Returns:

the cloned instance of this OverWritingBuffer.