Package org.jcsp.util.ints

Class OverWritingBufferInt

java.lang.Object

org.jcsp.util.ints.OverWritingBufferInt

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable, ChannelDataStoreInt

public class OverWritingBufferInt
extends java.lang.Object
implements ChannelDataStoreInt, java.io.Serializable

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

Description

OverWritingBufferInt is an implementation of ChannelDataStoreInt 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 construction methods of Channel (Channel.one2oneInt(org.jcsp.util.ints.ChannelDataStoreInt) etc.).

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

See Also:

ZeroBufferInt, BufferInt, OverWriteOldestBufferInt, OverFlowingBufferInt, InfiniteBufferInt, ChannelInt, Serialized Form

Field Summary

Fields

Modifier and Type	Field	Description
private int[]	buffer	The storage for the buffered ints
private int	counter	The number of ints stored in the Buffer
private int	firstIndex	The index of the oldest element (when counter > 0)
private int	lastIndex	The index of the next free element (when counter < buffer.length)
private boolean	valueWrittenWhileFull

Fields inherited from interface org.jcsp.util.ints.ChannelDataStoreInt

EMPTY, FULL, NONEMPTYFULL

Constructor Summary

Constructors

Constructor	Description
OverWritingBufferInt(int size)	Construct a new OverWritingBufferInt with the specified size.

Method Summary

Modifier and Type	Method	Description
java.lang.Object	clone()	Returns a new (and EMPTY) OverWritingBufferInt with the same creation parameters as this one.
void	endGet()	See startGet() for a description of the semantics of this method.
int	get()	Returns the oldest int from the OverWritingBufferInt and removes it.
int	getState()	Returns the current state of the OverWritingBufferInt.
void	put(int value)	Puts a new int into the OverWritingBufferInt.
void	removeAll()
int	startGet()	Begins an extended rendezvous by the reader.

Methods inherited from class java.lang.Object

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

Field Detail

buffer

private final int[] buffer

The storage for the buffered ints

counter

private int counter

The number of ints stored in the Buffer

firstIndex

private int firstIndex

The index of the oldest element (when counter > 0)

lastIndex

private int lastIndex

The index of the next free element (when counter < buffer.length)

valueWrittenWhileFull

private boolean valueWrittenWhileFull

Constructor Detail

OverWritingBufferInt

public OverWritingBufferInt(int size)

Construct a new OverWritingBufferInt with the specified size.

Parameters:

size - the number of ints the OverWritingBufferInt can store.

Throws:

BufferIntSizeError - 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 int get()

Returns the oldest int from the OverWritingBufferInt and removes it.

Pre-condition: getState must not currently return EMPTY.

Specified by:

get in interface ChannelDataStoreInt

Returns:

the oldest int from the OverWritingBufferInt

startGet

public int startGet()

Begins an extended rendezvous by the reader. The semantics of an extended rendezvous on an overwrite-newest buffer are slightly complicated, but hopefully intuitive. If the buffer is of size 2 or larger, the semantics are as follows. Beginning an extended rendezvous will return the oldest value in the buffer, but not remove it. If the writer writes to the buffer during the rendezvous, it will grow the buffer and end up overwriting the newest value as normal. At the end of the extended rendezvous, the oldest value is removed. If the buffer is of size 1, the semantics are identical to those of an OverWriteOldestBuffer. For a complete description, refer to the documentation for the OverWriteOldestBuffer.startGet() method.

Specified by:

startGet in interface ChannelDataStoreInt

Returns:

The oldest value in the buffer at this time

See Also:

ChannelDataStoreInt.endGet()

endGet

public void endGet()

See startGet() for a description of the semantics of this method.

Specified by:

endGet in interface ChannelDataStoreInt

See Also:

ChannelDataStoreInt.startGet()

put

public void put(int value)

Puts a new int into the OverWritingBufferInt.

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

Specified by:

put in interface ChannelDataStoreInt

Parameters:

value - the int to put into the OverWritingBufferInt

getState

public int getState()

Returns the current state of the OverWritingBufferInt.

Specified by:

getState in interface ChannelDataStoreInt

Returns:

the current state of the OverWritingBufferInt (EMPTY or NONEMPTYFULL)

clone

public java.lang.Object clone()

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

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

Specified by:

clone in interface ChannelDataStoreInt

Overrides:

clone in class java.lang.Object

Returns:

the cloned instance of this OverWritingBufferInt.

removeAll

public void removeAll()

Specified by:

removeAll in interface ChannelDataStoreInt