org.jcsp.util
Interface ChannelDataStore

All Superinterfaces:

Cloneable

All Known Implementing Classes:

Buffer, InfiniteBuffer, OverFlowingBuffer, OverWriteOldestBuffer, OverWritingBuffer, ZeroBuffer

public interface ChannelDataStore
extends Cloneable

This is the interface for object channel plug-ins that define their buffering characteristics.

Description

ChannelDataStore defines the interface to the logic used by channels defined in the org.jcsp.lang package to manage the data being communicated.

This enables that logic to be varied by creating channels specifying a particular implementation of this interface. This reduces the number of classes that would otherwise need to be defined. The default channel constructor (with no parameters) uses the ZeroBuffer implementation, which gives the standard CSP semantics -- no buffering and full synchronisation between reading and writing processes. See the static create methods of Channel etc.

Note: instances of ChannelDataStore implementations are used by the various channel classes within org.org.jcsp.lang in a thread-safe way. They are not intended for any other purpose. Developers of new ChannelDataStore implementations, therefore, do not need to worry about thread safety (e.g. by making its methods synchronized). Also, developers can assume that the documented pre-conditions for invoking the get and put methods will be met.

Author:

P.D.Austin

See Also:

ZeroBuffer, Buffer, OverWriteOldestBuffer, OverWritingBuffer, OverFlowingBuffer, InfiniteBuffer, Channel

Field Summary

static int	EMPTY Indicates that the ChannelDataStore is empty -- it can accept only a put.
static int	FULL Indicates that the ChannelDataStore is full -- it can accept only a get.
static int	NONEMPTYFULL Indicates that the ChannelDataStore is neither empty nor full -- it can accept either a put or a get call.

Method Summary

Object	clone() Returns a new (and EMPTY) ChannelDataStore with the same creation parameters as this one.
void	endGet() Ends an extended read on the buffer.
Object	get() Returns an Object from the ChannelDataStore.
int	getState() Returns the current state of the ChannelDataStore.
void	put(Object value) Puts a new Object into the ChannelDataStore.
void	removeAll() Deletes all items in the buffer, leaving it empty.
Object	startGet() Begins an extended read on the buffer, returning the data for the extended read Pre-condition: getState must not currently return EMPTY.

Field Detail

EMPTY

static final int EMPTY

Indicates that the ChannelDataStore is empty -- it can accept only a put.

See Also:

Constant Field Values

NONEMPTYFULL

static final int NONEMPTYFULL

Indicates that the ChannelDataStore is neither empty nor full -- it can accept either a put or a get call.

See Also:

Constant Field Values

FULL

static final int FULL

Indicates that the ChannelDataStore is full -- it can accept only a get.

See Also:

Constant Field Values

Method Detail

getState

int getState()

Returns the current state of the ChannelDataStore.

Returns:

the current state of the ChannelDataStore (EMPTY, NONEMPTYFULL or FULL)

put

void put(Object value)

Puts a new Object into the ChannelDataStore.

Pre-condition: getState must not currently return FULL.

Parameters:

value - the Object to put into the ChannelDataStore

get

Object get()

Returns an Object from the ChannelDataStore.

Pre-condition: getState must not currently return EMPTY.

Returns:

an Object from the ChannelDataStore

startGet

Object startGet()

Begins an extended read on the buffer, returning the data for the extended read Pre-condition: getState must not currently return EMPTY. The exact behaviour of this method depends on your buffer. When a process performs an extended rendezvous on a buffered channel, it will first call this method, then the endGet method. A FIFO buffer would implement this method as returning the value from the front of the buffer and the next call would remove the value. An overflowing buffer would do the same. However, for an overwriting buffer it is more complex. Refer to the documentation for OverWritingBuffer.startGet() and OverWriteOldestBuffer.startGet() for details

Returns:

The object to be read from the channel at the beginning of the extended rendezvous

endGet

void endGet()

Ends an extended read on the buffer. The channels guarantee that this method will be called exactly once after each beginExtRead call. During the period between startGet and endGet, it is possible that put will be called, but not get.

See Also:

endGet

clone

Object clone()

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

Note: Only the size and structure of the ChannelDataStore should be cloned, not any stored data.

Returns:

the cloned instance of this ChannelDataStore.

removeAll

void removeAll()

Deletes all items in the buffer, leaving it empty.