cern.entwined

Class Snapshot<T extends Snapshot<T>>

java.lang.Object

cern.entwined.SemiPersistent<T>

cern.entwined.Snapshot<T>

Type Parameters:

T - The implementation class type.

All Implemented Interfaces:

Comparable<T>

public abstract class Snapshot<T extends Snapshot<T>>
extends SemiPersistent<T>
implements Comparable<T>

A common abstract class for client specific implementations of transactional shared memory. Snapshot mainly serves as a root node in the tree of shared memory. It may also be described as a single access point to transactional shared memory.

Author:

Ivan Koblik

Field Summary

Fields

Modifier and Type	Field and Description
protected long	timestamp Timestamp is incrementally generated from it previous value.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	Snapshot(long timestamp) Creates a new Snapshot initializing its timestamp with the give value.

Method Summary

Methods

Modifier and Type	Method and Description
T	commit(T globalState) Performs conflict checks and if no conflicts detected returns new instance with all the pending changes applied.
int	compareTo(T otherSnapshot) Compares snapshot timestamps only.

Methods inherited from class cern.entwined.SemiPersistent

cleanCopy, dirtyCopy, update

Methods inherited from class java.lang.Object

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

Field Detail

timestamp

protected final long timestamp

Timestamp is incrementally generated from it previous value. It is supposed to be incremented only at commit.

Constructor Detail

Snapshot

protected Snapshot(long timestamp)

Creates a new Snapshot initializing its timestamp with the give value.

Note: Pass following values

• Zero when creating a new snapshot,
• Previous timestamp when copying a snapshot, and
• Previous timestamp + 1 when committing a snapshot.

Parameters:

timestamp - The timestamp of the created snapshot.

Method Detail

compareTo

public int compareTo(T otherSnapshot)

Compares snapshot timestamps only. Do not rely on this method when comparing snapshot states, use Transactional.commit(Object) instead.

Specified by:

compareTo in interface Comparable<T extends Snapshot<T>>

commit

public T commit(T globalState)

Performs conflict checks and if no conflicts detected returns new instance with all the pending changes applied.

Parameters:

globalState - The current system's global state.

Returns:

New instance with all the pending changes applied.

Throws:

ConflictException - When conflicting changes detected.