org.jcsp.util
Class OverFlowingBuffer

java.lang.Object
  org.jcsp.util.OverFlowingBuffer

All Implemented Interfaces:

Serializable, Cloneable, ChannelDataStore

public class OverFlowingBuffer
extends Object
implements ChannelDataStore, Serializable

This is used to create a buffered object channel that always accepts input, discarding 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 be accepted but the written value overflows the buffer and is lost to the channel. See the static construction methods of Channel (Channel.one2one(org.jcsp.util.ChannelDataStore) etc.).

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

Author:

P.D. Austin

See Also:

ZeroBuffer, Buffer, OverWriteOldestBuffer, OverWritingBuffer, InfiniteBuffer, Channel, Serialized Form

Field Summary

Fields inherited from interface org.jcsp.util.ChannelDataStore

EMPTY, FULL, NONEMPTYFULL

Constructor Summary

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

Method Summary

Object	clone() Returns a new (and EMPTY) OverFlowingBuffer with the same creation parameters as this one.
void	endGet() Removes the oldest object from the buffer.
Object	get() Returns the oldest Object from the OverFlowingBuffer and removes it.
int	getState() Returns the current state of the OverFlowingBuffer.
void	put(Object value) Puts a new Object into the OverFlowingBuffer.
void	removeAll() Deletes all items in the buffer, leaving it empty.
Object	startGet() Returns the oldest object from the buffer but does not remove it.

Methods inherited from class java.lang.Object

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

Constructor Detail

OverFlowingBuffer

public OverFlowingBuffer(int size)

Construct a new OverFlowingBuffer with the specified size.

Parameters:

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

Pre-condition: getState must not currently return EMPTY.

Specified by:

get in interface ChannelDataStore

Returns:

the oldest Object from the OverFlowingBuffer

startGet

public Object startGet()

Returns the oldest object from the buffer but does not remove it. Pre-condition: getState must not currently return EMPTY.

Specified by:

startGet in interface ChannelDataStore

Returns:

the oldest Object from the Buffer

See Also:

ChannelDataStore.endGet()

endGet

public void endGet()

Removes the oldest object from the buffer.

Specified by:

endGet in interface ChannelDataStore

See Also:

ChannelDataStore.startGet()

put

public void put(Object value)

Puts a new Object into the OverFlowingBuffer.

If OverFlowingBuffer is full, the item is discarded.

Specified by:

put in interface ChannelDataStore

Parameters:

value - the Object to put into the OverFlowingBuffer

getState

public int getState()

Returns the current state of the OverFlowingBuffer.

Specified by:

getState in interface ChannelDataStore

Returns:

the current state of the OverFlowingBuffer (EMPTY or NONEMPTYFULL)

clone

public Object clone()

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

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

Specified by:

clone in interface ChannelDataStore

Overrides:

clone in class Object

Returns:

the cloned instance of this OverFlowingBuffer.

removeAll

public void removeAll()

Description copied from interface: ChannelDataStore

Deletes all items in the buffer, leaving it empty.

Specified by:

removeAll in interface ChannelDataStore