org.cache2k.impl

Class ClosableConcurrentHashEntryIterator<E extends Entry>

java.lang.Object

org.cache2k.impl.ClosableConcurrentHashEntryIterator<E>

All Implemented Interfaces:

Closeable, AutoCloseable, Iterator<E>, ClosableIterator<E>

public class ClosableConcurrentHashEntryIterator<E extends Entry>
extends Object
implements ClosableIterator<E>

Iterator over all hash table entries of two hashes.

The hash has a usage/reference counter for iterations to suspend expand until the iteration finished. This is needed for correctness of the iteration, if an expand is done during the iteration process, the iterations returns duplicate entries or not all entries.

Failing to operate the increment/decrement in balance will mean that the hash table expands are blocked forever, which is a serious error condition. Typical problems arise by thrown exceptions during an iteration. Since there is a measure for the hash quality, a problem like this may be detected.

Rationale: We need to keep track of the entries/keys iterated. The cache may remove and insert entries from hash to refreshHash, also the application may do a remove and insert. A removed entry has always e.another kept intact, so traversal of the collision list will always work. If a iteration is going on, this means a removed entry needs to be cloned to reassign the e.another pointer.

Rationale: The iteration just works on the hash data structure. However, it needs to be checked, whether the cache is closed meanwhile. To signal this, the hash is closed also. This is a little complex, but safes the dependency on the cache here.

Author:

Jens Wilke; created: 2013-12-21

Constructor Summary

Constructors

Constructor and Description
ClosableConcurrentHashEntryIterator(Hash<E> _hashCtl, E[] _hash, Hash<E> _hashCtl2, E[] _hash2)

Method Summary

Methods

Modifier and Type	Method and Description
protected boolean	checkForClearAndAbort() Check if hash was cleared and we need to abort.
protected E	checkIteratedOrNext(E e)
void	close()
protected void	finalize()
boolean	hasNext()
E	next()
void	remove()
void	setKeepIterated(boolean keepIterated) Keep hash of iterated items, needed for storage iteration.
void	setStopOnClear(boolean stopOnClear) Iterations stops when storage is cleared, default is true.
protected boolean	switchAndCheckAbort()

Methods inherited from class java.lang.Object

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

Constructor Detail

ClosableConcurrentHashEntryIterator

public ClosableConcurrentHashEntryIterator(Hash<E> _hashCtl,
                                   E[] _hash,
                                   Hash<E> _hashCtl2,
                                   E[] _hash2)

Method Detail

checkIteratedOrNext

protected E checkIteratedOrNext(E e)

switchAndCheckAbort

protected boolean switchAndCheckAbort()

checkForClearAndAbort

protected boolean checkForClearAndAbort()

Check if hash was cleared and we need to abort. Returns true if we should abort.

hasNext

public boolean hasNext()

Specified by:

hasNext in interface Iterator<E extends Entry>

next

public E next()

Specified by:

next in interface Iterator<E extends Entry>

remove

public void remove()

Specified by:

remove in interface Iterator<E extends Entry>

close

public void close()

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Specified by:

close in interface ClosableIterator<E extends Entry>

finalize

protected void finalize()
                 throws Throwable

Overrides:

finalize in class Object

Throws:

Throwable

setKeepIterated

public void setKeepIterated(boolean keepIterated)

Keep hash of iterated items, needed for storage iteration.

setStopOnClear

public void setStopOnClear(boolean stopOnClear)

Iterations stops when storage is cleared, default is true.