org.cache2k.core

Class Hash2<K,V>

java.lang.Object

org.cache2k.core.Hash2<K,V>

public class Hash2<K,V>
extends Object

Simple concurrent hash table implementation using optimistic locking for the segments locks.

Author:

Jens Wilke

See Also:

OptimisticLock

Constructor Summary

Constructors

Constructor and Description
Hash2(org.cache2k.Cache _cache)

Method Summary

Modifier and Type	Method and Description
long	calcEntryCount() Count the entries in the hash table, by scanning through the hash table.
void	calcHashCollisionInfo(CollisionInfo inf)
void	checkExpand(int _hash) Checks whether expansion is needed and expand when insertWithinLock(Entry, int, int) is used.
void	clearWhenLocked()
void	close() Close the cache by discarding the entry table.
int	getClearOrCloseCount()
Entry<K,V>[]	getEntries() Entry table for used by the iterator.
long	getEntryCapacity()
OptimisticLock	getSegmentLock(int _hash)
long	getSegmentMaxFill() For testing
long	getSize()
Entry<K,V>	insertWithinLock(Entry<K,V> e, int _hash, int _keyValue) Insert an entry.
protected boolean	keyObjIsEqual(K key, Entry e)
Entry<K,V>	lookup(K key, int _hash, int _keyValue) Lookup the entry in the hash table and return it.
protected int	modifiedHashCode(int hc)
boolean	remove(Entry<K,V> e) Remove existing entry from the hash.
boolean	removeWithinLock(Entry<K,V> e, int _hash)
<T> T	runTotalLocked(Job<T> j) Lock all segments and run the job.

Methods inherited from class java.lang.Object

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

Constructor Detail

Hash2

public Hash2(org.cache2k.Cache _cache)

Parameters:

_cache - Cache reference only needed for the cache name in case of an exception

Method Detail

getEntryCapacity

public long getEntryCapacity()

getSegmentMaxFill

public long getSegmentMaxFill()

For testing

lookup

public Entry<K,V> lookup(K key,
                         int _hash,
                         int _keyValue)

Lookup the entry in the hash table and return it. First tries an optimistic read.

keyObjIsEqual

protected boolean keyObjIsEqual(K key,
                                Entry e)

insertWithinLock

public Entry<K,V> insertWithinLock(Entry<K,V> e,
                                   int _hash,
                                   int _keyValue)

Insert an entry. Checks if an entry already exists.

checkExpand

public void checkExpand(int _hash)

Checks whether expansion is needed and expand when insertWithinLock(Entry, int, int) is used. No lock may be hold when calling this method, since the table must be locked completely using the proper lock order.

Need for expansion is only checked by comparing whether the associated segment is full. Should be called after insert after giving up the lock.

getSegmentLock

public OptimisticLock getSegmentLock(int _hash)

remove

public boolean remove(Entry<K,V> e)

Remove existing entry from the hash.

Returns:

true, if entry was found and removed.

removeWithinLock

public boolean removeWithinLock(Entry<K,V> e,
                                int _hash)

modifiedHashCode

protected int modifiedHashCode(int hc)

getSize

public long getSize()

runTotalLocked

public <T> T runTotalLocked(Job<T> j)

Lock all segments and run the job.

clearWhenLocked

public void clearWhenLocked()

getClearOrCloseCount

public int getClearOrCloseCount()

close

public void close()

Close the cache by discarding the entry table. Assumes total lock.

Closing will be visible to other threads, because of the guarantees of the locking. Using the entry table for closing has the advantage that the close check collapses with the implicit null check and has no additional overhead.

calcHashCollisionInfo

public void calcHashCollisionInfo(CollisionInfo inf)

calcEntryCount

public long calcEntryCount()

Count the entries in the hash table, by scanning through the hash table. This is used for integrity checks.

getEntries

public Entry<K,V>[] getEntries()

Entry table for used by the iterator.