freenet.support

Class LRUMap<K,V>

java.lang.Object

freenet.support.LRUMap<K,V>

Type Parameters:

K - The key type.

V - The value type.

public class LRUMap<K,V>
extends java.lang.Object

An LRU map from K to V. That is, when a mapping is added, it is pushed to the top of the queue, even if it was already present, and pop/peek operate from the bottom of the queue i.e. the least recently pushed. The caller must implement any size limit needed. FIXME most callers should be switched to LinkedHashMap. Does not support null keys.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	LRUMap.QItem<K,V>

Constructor Summary

Constructors

Constructor and Description
LRUMap()

Method Summary

Modifier and Type	Method and Description
void	clear()
boolean	containsKey(K key) Check if this queue contains obj
static <K extends java.lang.Comparable<K>,V> LRUMap<K,V>	createSafeMap() Create a LRUMap that is safe to use with keys that can be controlled by an attacker.
static <K,V> LRUMap<K,V>	createSafeMap(java.util.Comparator<K> comparator) Create a LRUMap that is safe to use with keys that can be controlled by an attacker.
V	get(K key) Note that this does not automatically promote the key.
boolean	isEmpty()
java.util.Enumeration<K>	keys()
K	peekKey()
V	peekValue()
K	popKey()
V	popValue()
V	push(K key, V value) push()ing an object that is already in the queue moves that object to the most recently used position, but doesn't add a duplicate entry in the queue.
boolean	removeKey(K key)
int	size()
java.util.Enumeration<V>	values()
void	valuesToArray(V[] entries) Note that unlike the java.util versions, this will not reallocate (hence it doesn't return), so pass in an appropriately big array, and make sure you hold the lock!

Methods inherited from class java.lang.Object

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

Constructor Detail

LRUMap

public LRUMap()

Method Detail

createSafeMap

public static <K extends java.lang.Comparable<K>,V> LRUMap<K,V> createSafeMap()

Create a LRUMap that is safe to use with keys that can be controlled by an attacker. Meaning one based on a TreeMap, not a HashMap (think hash collision DoS's).

createSafeMap

public static <K,V> LRUMap<K,V> createSafeMap(java.util.Comparator<K> comparator)

Create a LRUMap that is safe to use with keys that can be controlled by an attacker. Meaning one based on a TreeMap, not a HashMap (think hash collision DoS's).

push

public final V push(K key,
                    V value)

push()ing an object that is already in the queue moves that object to the most recently used position, but doesn't add a duplicate entry in the queue.

popKey

public final K popKey()

Returns:

Least recently pushed key.

popValue

public final V popValue()

Returns:

Least recently pushed value.

peekValue

public final V peekValue()

peekKey

public final K peekKey()

size

public final int size()

removeKey

public final boolean removeKey(K key)

containsKey

public final boolean containsKey(K key)

Check if this queue contains obj

Parameters:

obj - Object to match

Returns:

true if this queue contains obj.

get

public final V get(K key)

Note that this does not automatically promote the key. You have to do that by hand with push(key, value).

keys

public java.util.Enumeration<K> keys()

values

public java.util.Enumeration<V> values()

isEmpty

public boolean isEmpty()

valuesToArray

public void valuesToArray(V[] entries)

Note that unlike the java.util versions, this will not reallocate (hence it doesn't return), so pass in an appropriately big array, and make sure you hold the lock!

Parameters:

entries -

clear

public void clear()