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Extract AbstractReferenceMap from ReferenceMap 

git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/collections/trunk@131650 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Stephen Colebourne 2004-04-09 22:18:18 +00:00
parent 4c37a65e92
commit 4433733ff1
3 changed files with 981 additions and 807 deletions
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892
src/java/org/apache/commons/collections/map/AbstractReferenceMap.java Normal file
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@ -0,0 +1,892 @@
/*
* Copyright 2002-2004 The Apache Software Foundation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.collections.map;
import java.lang.ref.Reference;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.SoftReference;
import java.lang.ref.WeakReference;
import java.util.ArrayList;
import java.util.Collection;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Set;
import org.apache.commons.collections.MapIterator;
import org.apache.commons.collections.keyvalue.DefaultMapEntry;
/**
* An abstract implementation of a hash-based map that allows the entries to
* be removed by the garbage collector.
* <p>
* This class implements all the features necessary for a subclass reference
* hash-based map. Key-value entries are stored in instances of the
* <code>ReferenceEntry</code> class which can be overridden and replaced.
* The iterators can similarly be replaced, without the need to replace the KeySet,
* EntrySet and Values view classes.
* <p>
* Overridable methods are provided to change the default hashing behaviour, and
* to change how entries are added to and removed from the map. Hopefully, all you
* need for unusual subclasses is here.
* <p>
* When you construct an <code>AbstractReferenceMap</code>, you can specify what
* kind of references are used to store the map's keys and values.
* If non-hard references are used, then the garbage collector can remove
* mappings if a key or value becomes unreachable, or if the JVM's memory is
* running low. For information on how the different reference types behave,
* see {@link Reference}.
* <p>
* Different types of references can be specified for keys and values.
* The keys can be configured to be weak but the values hard,
* in which case this class will behave like a
* <a href="http://java.sun.com/j2se/1.4/docs/api/java/util/WeakHashMap.html">
* <code>WeakHashMap</code></a>. However, you can also specify hard keys and
* weak values, or any other combination. The default constructor uses
* hard keys and soft values, providing a memory-sensitive cache.
* <p>
* This {@link Map} implementation does <i>not</i> allow null elements.
* Attempting to add a null key or value to the map will raise a
* <code>NullPointerException</code>.
* <p>
* All the available iterators can be reset back to the start by casting to
* <code>ResettableIterator</code> and calling <code>reset()</code>.
* <p>
* This implementation is not synchronized.
* You can use {@link java.util.Collections#synchronizedMap} to
* provide synchronized access to a <code>ReferenceMap</code>.
*
* @see java.lang.ref.Reference
* @since Commons Collections 3.1 (from ReferenceMap in 3.0)
* @version $Revision: 1.1 $ $Date: 2004/04/09 22:18:18 $
*
* @author Paul Jack
* @author Stephen Colebourne
*/
public abstract class AbstractReferenceMap extends AbstractHashedMap {
/** Constant indicating that hard references should be used */
public static final int HARD = 0;
/** Constant indicating that soft references should be used */
public static final int SOFT = 1;
/** Constant indicating that weak references should be used */
public static final int WEAK = 2;
/**
* The reference type for keys. Must be HARD, SOFT, WEAK.
* @serial
*/
private int keyType;
/**
* The reference type for values. Must be HARD, SOFT, WEAK.
* @serial
*/
private int valueType;
/**
* Should the value be automatically purged when the associated key has been collected?
*/
private boolean purgeValues;
/**
* ReferenceQueue used to eliminate stale mappings.
* See purge.
*/
private transient ReferenceQueue queue = new ReferenceQueue();
//-----------------------------------------------------------------------
/**
* Constructor used during deserialization.
*/
protected AbstractReferenceMap() {
super();
}
/**
* Constructs a new empty map with the specified reference types,
* load factor and initial capacity.
*
* @param keyType the type of reference to use for keys;
* must be {@link #HARD}, {@link #SOFT}, {@link #WEAK}
* @param valueType the type of reference to use for values;
* must be {@link #HARD}, {@link #SOFT}, {@link #WEAK}
* @param capacity the initial capacity for the map
* @param loadFactor the load factor for the map
* @param purgeValues should the value be automatically purged when the
* key is garbage collected
*/
protected AbstractReferenceMap(
int keyType, int valueType, int capacity,
float loadFactor, boolean purgeValues) {
super(capacity, loadFactor);
verify("keyType", keyType);
verify("valueType", valueType);
this.keyType = keyType;
this.valueType = valueType;
this.purgeValues = purgeValues;
}
//-----------------------------------------------------------------------
/**
* Checks the type int is a valid value.
*
* @param name the name for error messages
* @param type the type value to check
* @throws IllegalArgumentException if the value if invalid
*/
private static void verify(String name, int type) {
if ((type < HARD) || (type > WEAK)) {
throw new IllegalArgumentException(name + " must be HARD, SOFT, WEAK.");
}
}
//-----------------------------------------------------------------------
// /**
// * Writes this object to the given output stream.
// *
// * @param out the output stream to write to
// * @throws IOException if the stream raises it
// */
// private void writeObject(ObjectOutputStream out) throws IOException {
// out.defaultWriteObject();
// out.writeInt(data.length);
//
// // Have to use null-terminated list because size might shrink
// // during iteration
//
// for (Iterator iter = entrySet().iterator(); iter.hasNext();) {
// Map.Entry entry = (Map.Entry)iter.next();
// out.writeObject(entry.getKey());
// out.writeObject(entry.getValue());
// }
// out.writeObject(null);
// }
//
//
// /**
// * Reads the contents of this object from the given input stream.
// *
// * @param in the input stream to read from
// * @throws IOException if the stream raises it
// * @throws ClassNotFoundException if the stream raises it
// */
// private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
// in.defaultReadObject();
// data = new HashEntry[in.readInt()];
// threshold = calculateThreshold(data.length, loadFactor);
// queue = new ReferenceQueue();
// Object key = in.readObject();
// while (key != null) {
// Object value = in.readObject();
// put(key, value);
// key = in.readObject();
// }
// }
//-----------------------------------------------------------------------
/**
* Gets the size of the map.
*
* @return the size
*/
public int size() {
purgeBeforeRead();
return super.size();
}
/**
* Checks whether the map is currently empty.
*
* @return true if the map is currently size zero
*/
public boolean isEmpty() {
purgeBeforeRead();
return super.isEmpty();
}
/**
* Checks whether the map contains the specified key.
*
* @param key the key to search for
* @return true if the map contains the key
*/
public boolean containsKey(Object key) {
purgeBeforeRead();
Entry entry = getEntry(key);
if (entry == null) {
return false;
}
return (entry.getValue() != null);
}
/**
* Checks whether the map contains the specified value.
*
* @param value the value to search for
* @return true if the map contains the value
*/
public boolean containsValue(Object value) {
purgeBeforeRead();
if (value == null) {
return false;
}
return super.containsValue(value);
}
/**
* Gets the value mapped to the key specified.
*
* @param key the key
* @return the mapped value, null if no match
*/
public Object get(Object key) {
purgeBeforeRead();
Entry entry = getEntry(key);
if (entry == null) {
return null;
}
return entry.getValue();
}
/**
* Puts a key-value mapping into this map.
* Neither the key nor the value may be null.
*
* @param key the key to add, must not be null
* @param value the value to add, must not be null
* @return the value previously mapped to this key, null if none
* @throws NullPointerException if either the key or value is null
*/
public Object put(Object key, Object value) {
if (key == null) {
throw new NullPointerException("null keys not allowed");
}
if (value == null) {
throw new NullPointerException("null values not allowed");
}
purgeBeforeWrite();
return super.put(key, value);
}
/**
* Removes the specified mapping from this map.
*
* @param key the mapping to remove
* @return the value mapped to the removed key, null if key not in map
*/
public Object remove(Object key) {
if (key == null) {
return null;
}
purgeBeforeWrite();
return super.remove(key);
}
/**
* Clears this map.
*/
public void clear() {
super.clear();
while (queue.poll() != null) {} // drain the queue
}
//-----------------------------------------------------------------------
/**
* Gets a MapIterator over the reference map.
* The iterator only returns valid key/value pairs.
*
* @return a map iterator
*/
public MapIterator mapIterator() {
return new ReferenceMapIterator(this);
}
/**
* Returns a set view of this map's entries.
* An iterator returned entry is valid until <code>next()</code> is called again.
* The <code>setValue()</code> method on the <code>toArray</code> entries has no effect.
*
* @return a set view of this map's entries
*/
public Set entrySet() {
if (entrySet == null) {
entrySet = new ReferenceEntrySet(this);
}
return entrySet;
}
/**
* Returns a set view of this map's keys.
*
* @return a set view of this map's keys
*/
public Set keySet() {
if (keySet == null) {
keySet = new ReferenceKeySet(this);
}
return keySet;
}
/**
* Returns a collection view of this map's values.
*
* @return a set view of this map's values
*/
public Collection values() {
if (values == null) {
values = new ReferenceValues(this);
}
return values;
}
//-----------------------------------------------------------------------
/**
* Purges stale mappings from this map before read operations.
* <p>
* This implementation calls {@link #purge()} to maintain a consistent state.
*/
protected void purgeBeforeRead() {
purge();
}
/**
* Purges stale mappings from this map before write operations.
* <p>
* This implementation calls {@link #purge()} to maintain a consistent state.
*/
protected void purgeBeforeWrite() {
purge();
}
/**
* Purges stale mappings from this map.
* <p>
* Note that this method is not synchronized! Special
* care must be taken if, for instance, you want stale
* mappings to be removed on a periodic basis by some
* background thread.
*/
protected void purge() {
Reference ref = queue.poll();
while (ref != null) {
purge(ref);
ref = queue.poll();
}
}
/**
* Purges the specified reference.
*
* @param ref the reference to purge
*/
protected void purge(Reference ref) {
// The hashCode of the reference is the hashCode of the
// mapping key, even if the reference refers to the
// mapping value...
int hash = ref.hashCode();
int index = hashIndex(hash, data.length);
HashEntry previous = null;
HashEntry entry = data[index];
while (entry != null) {
if (((ReferenceEntry) entry).purge(ref)) {
if (previous == null) {
data[index] = entry.next;
} else {
previous.next = entry.next;
}
this.size--;
return;
}
previous = entry;
entry = entry.next;
}
}
//-----------------------------------------------------------------------
/**
* Gets the entry mapped to the key specified.
*
* @param key the key
* @return the entry, null if no match
*/
protected HashEntry getEntry(Object key) {
if (key == null) {
return null;
} else {
return super.getEntry(key);
}
}
/**
* Compares two keys, in internal converted form, to see if they are equal.
* <p>
* This implementation converts the key from the entry to a real reference
* before comparison.
*
* @param key1 the first key to compare passed in from outside
* @param key2 the second key extracted from the entry via <code>entry.key</code>
* @return true if equal
* @since Commons Collections 3.1
*/
protected boolean isEqualKey(Object key1, Object key2) {
key2 = (keyType > HARD ? ((Reference) key2).get() : key2);
return (key1 == key2 || key1.equals(key2));
}
/**
* Creates a ReferenceEntry instead of a HashEntry.
*
* @param next the next entry in sequence
* @param hashCode the hash code to use
* @param key the key to store
* @param value the value to store
* @return the newly created entry
* @since Commons Collections 3.1
*/
protected HashEntry createEntry(HashEntry next, int hashCode, Object key, Object value) {
return new ReferenceEntry(this, next, hashCode, key, value);
}
/**
* Creates an entry set iterator.
*
* @return the entrySet iterator
* @since Commons Collections 3.1
*/
protected Iterator createEntrySetIterator() {
return new ReferenceEntrySetIterator(this);
}
/**
* Creates an key set iterator.
*
* @return the keySet iterator
* @since Commons Collections 3.1
*/
protected Iterator createKeySetIterator() {
return new ReferenceKeySetIterator(this);
}
/**
* Creates an values iterator.
*
* @return the values iterator
* @since Commons Collections 3.1
*/
protected Iterator createValuesIterator() {
return new ReferenceValuesIterator(this);
}
//-----------------------------------------------------------------------
/**
* EntrySet implementation.
*/
static class ReferenceEntrySet extends EntrySet {
protected ReferenceEntrySet(AbstractHashedMap parent) {
super(parent);
}
public Object[] toArray() {
return toArray(new Object[0]);
}
public Object[] toArray(Object[] arr) {
// special implementation to handle disappearing entries
ArrayList list = new ArrayList();
Iterator iterator = iterator();
while (iterator.hasNext()) {
Entry e = (Entry) iterator.next();
list.add(new DefaultMapEntry(e.getKey(), e.getValue()));
}
return list.toArray(arr);
}
}
//-----------------------------------------------------------------------
/**
* KeySet implementation.
*/
static class ReferenceKeySet extends KeySet {
protected ReferenceKeySet(AbstractHashedMap parent) {
super(parent);
}
public Object[] toArray() {
return toArray(new Object[0]);
}
public Object[] toArray(Object[] arr) {
// special implementation to handle disappearing keys
List list = new ArrayList(parent.size());
for (Iterator it = iterator(); it.hasNext(); ) {
list.add(it.next());
}
return list.toArray(arr);
}
}
//-----------------------------------------------------------------------
/**
* Values implementation.
*/
static class ReferenceValues extends Values {
protected ReferenceValues(AbstractHashedMap parent) {
super(parent);
}
public Object[] toArray() {
return toArray(new Object[0]);
}
public Object[] toArray(Object[] arr) {
// special implementation to handle disappearing values
List list = new ArrayList(parent.size());
for (Iterator it = iterator(); it.hasNext(); ) {
list.add(it.next());
}
return list.toArray(arr);
}
}
//-----------------------------------------------------------------------
/**
* A MapEntry implementation for the map.
* <p>
* If getKey() or getValue() returns null, it means
* the mapping is stale and should be removed.
*/
protected static class ReferenceEntry extends HashEntry {
/** The parent map */
protected final AbstractReferenceMap parent;
/**
* Creates a new entry object for the ReferenceMap.
*
* @param parent the parent map
* @param next the next entry in the hash bucket
* @param hashCode the hash code of the key
* @param key the key
* @param value the value
*/
public ReferenceEntry(AbstractReferenceMap parent, HashEntry next, int hashCode, Object key, Object value) {
super(next, hashCode, null, null);
this.parent = parent;
this.key = toReference(parent.keyType, key, hashCode);
this.value = toReference(parent.valueType, value, hashCode);
}
public Object getKey() {
return (parent.keyType > HARD) ? ((Reference) key).get() : key;
}
public Object getValue() {
return (parent.valueType > HARD) ? ((Reference) value).get() : value;
}
public Object setValue(Object obj) {
Object old = getValue();
if (parent.valueType > HARD) {
((Reference)value).clear();
}
value = toReference(parent.valueType, obj, hashCode);
return old;
}
public boolean equals(Object obj) {
if (obj == this) {
return true;
}
if (obj instanceof Map.Entry == false) {
return false;
}
Map.Entry entry = (Map.Entry)obj;
Object key = entry.getKey();
Object value = entry.getValue();
if ((key == null) || (value == null)) {
return false;
}
return key.equals(getKey()) && value.equals(getValue());
}
/**
* Constructs a reference of the given type to the given referent.
* The reference is registered with the queue for later purging.
*
* @param type HARD, SOFT or WEAK
* @param referent the object to refer to
* @param hash the hash code of the <i>key</i> of the mapping;
* this number might be different from referent.hashCode() if
* the referent represents a value and not a key
* @since Commons Collections 3.1
*/
protected Object toReference(int type, Object referent, int hash) {
switch (type) {
case HARD: return referent;
case SOFT: return new SoftRef(hash, referent, parent.queue);
case WEAK: return new WeakRef(hash, referent, parent.queue);
default: throw new Error();
}
}
/**
* Purges the specified reference
* @param ref the reference to purge
* @return true or false
*/
boolean purge(Reference ref) {
boolean r = (parent.keyType > HARD) && (key == ref);
r = r || ((parent.valueType > HARD) && (value == ref));
if (r) {
if (parent.keyType > HARD) {
((Reference)key).clear();
}
if (parent.valueType > HARD) {
((Reference)value).clear();
} else if (parent.purgeValues) {
value = null;
}
}
return r;
}
/**
* Gets the next entry in the bucket.
*
* @return the next entry in the bucket
*/
protected ReferenceEntry next() {
return (ReferenceEntry) next;
}
}
//-----------------------------------------------------------------------
/**
* The EntrySet iterator.
*/
static class ReferenceEntrySetIterator implements Iterator {
/** The parent map */
final AbstractReferenceMap parent;
// These fields keep track of where we are in the table.
int index;
ReferenceEntry entry;
ReferenceEntry previous;
// These Object fields provide hard references to the
// current and next entry; this assures that if hasNext()
// returns true, next() will actually return a valid element.
Object nextKey, nextValue;
Object currentKey, currentValue;
int expectedModCount;
public ReferenceEntrySetIterator(AbstractReferenceMap parent) {
super();
this.parent = parent;
index = (parent.size() != 0 ? parent.data.length : 0);
// have to do this here! size() invocation above
// may have altered the modCount.
expectedModCount = parent.modCount;
}
public boolean hasNext() {
checkMod();
while (nextNull()) {
ReferenceEntry e = entry;
int i = index;
while ((e == null) && (i > 0)) {
i--;
e = (ReferenceEntry) parent.data[i];
}
entry = e;
index = i;
if (e == null) {
currentKey = null;
currentValue = null;
return false;
}
nextKey = e.getKey();
nextValue = e.getValue();
if (nextNull()) {
entry = entry.next();
}
}
return true;
}
private void checkMod() {
if (parent.modCount != expectedModCount) {
throw new ConcurrentModificationException();
}
}
private boolean nextNull() {
return (nextKey == null) || (nextValue == null);
}
protected ReferenceEntry nextEntry() {
checkMod();
if (nextNull() && !hasNext()) {
throw new NoSuchElementException();
}
previous = entry;
entry = entry.next();
currentKey = nextKey;
currentValue = nextValue;
nextKey = null;
nextValue = null;
return previous;
}
protected ReferenceEntry currentEntry() {
checkMod();
return previous;
}
public Object next() {
return nextEntry();
}
public void remove() {
checkMod();
if (previous == null) {
throw new IllegalStateException();
}
parent.remove(currentKey);
previous = null;
currentKey = null;
currentValue = null;
expectedModCount = parent.modCount;
}
}
/**
* The keySet iterator.
*/
static class ReferenceKeySetIterator extends ReferenceEntrySetIterator {
ReferenceKeySetIterator(AbstractReferenceMap parent) {
super(parent);
}
public Object next() {
return nextEntry().getKey();
}
}
/**
* The values iterator.
*/
static class ReferenceValuesIterator extends ReferenceEntrySetIterator {
ReferenceValuesIterator(AbstractReferenceMap parent) {
super(parent);
}
public Object next() {
return nextEntry().getValue();
}
}
/**
* The MapIterator implementation.
*/
static class ReferenceMapIterator extends ReferenceEntrySetIterator implements MapIterator {
protected ReferenceMapIterator(AbstractReferenceMap parent) {
super(parent);
}
public Object next() {
return nextEntry().getKey();
}
public Object getKey() {
HashEntry current = currentEntry();
if (current == null) {
throw new IllegalStateException(AbstractHashedMap.GETKEY_INVALID);
}
return current.getKey();
}
public Object getValue() {
HashEntry current = currentEntry();
if (current == null) {
throw new IllegalStateException(AbstractHashedMap.GETVALUE_INVALID);
}
return current.getValue();
}
public Object setValue(Object value) {
HashEntry current = currentEntry();
if (current == null) {
throw new IllegalStateException(AbstractHashedMap.SETVALUE_INVALID);
}
return current.setValue(value);
}
}
//-----------------------------------------------------------------------
// These two classes store the hashCode of the key of
// of the mapping, so that after they're dequeued a quick
// lookup of the bucket in the table can occur.
/**
* A soft reference holder.
*/
static class SoftRef extends SoftReference {
private int hash;
public SoftRef(int hash, Object r, ReferenceQueue q) {
super(r, q);
this.hash = hash;
}
public int hashCode() {
return hash;
}
}
/**
* A weak reference holder.
*/
static class WeakRef extends WeakReference {
private int hash;
public WeakRef(int hash, Object r, ReferenceQueue q) {
super(r, q);
this.hash = hash;
}
public int hashCode() {
return hash;
}
}
}

848
src/java/org/apache/commons/collections/map/ReferenceMap.java
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@ -15,23 +15,6 @@
*/
package org.apache.commons.collections.map;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.lang.ref.Reference;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.SoftReference;
import java.lang.ref.WeakReference;
import java.util.ArrayList;
import java.util.Collection;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Set;
import org.apache.commons.collections.keyvalue.DefaultMapEntry;
/**
* A <code>Map</code> implementation that allows mappings to be
@ -55,10 +38,13 @@ import org.apache.commons.collections.keyvalue.DefaultMapEntry;
* This {@link Map} implementation does <i>not</i> allow null elements.
* Attempting to add a null key or value to the map will raise a <code>NullPointerException</code>.
* <p>
* As usual, this implementation is not synchronized.
* This implementation is not synchronized.
* You can use {@link java.util.Collections#synchronizedMap} to
* provide synchronized access to a <code>ReferenceMap</code>.
* <p>
* All the available iterators can be reset back to the start by casting to
* <code>ResettableIterator</code> and calling <code>reset()</code>.
* <p>
* NOTE: As from Commons Collections 3.1 this map extends <code>AbstractHashedMap</code>
* (previously it extended AbstractMap). As a result, the implementation is now
* extensible and provides a <code>MapIterator</code>.
@ -66,830 +52,82 @@ import org.apache.commons.collections.keyvalue.DefaultMapEntry;
* @see java.lang.ref.Reference
*
* @since Commons Collections 3.0 (previously in main package v2.1)
* @version $Revision: 1.11 $ $Date: 2004/04/01 00:07:48 $
* @version $Revision: 1.12 $ $Date: 2004/04/09 22:18:18 $
*
* @author Paul Jack
* @author Stephen Colebourne
*/
public class ReferenceMap extends AbstractHashedMap {
public class ReferenceMap extends AbstractReferenceMap {
/**
* For serialization.
*/
private static final long serialVersionUID = -3370601314380922368L;
/**
* Constant indicating that hard references should be used.
*/
public static final int HARD = 0;
/**
* Constant indicating that soft references should be used.
*/
public static final int SOFT = 1;
/**
* Constant indicating that weak references should be used.
*/
public static final int WEAK = 2;
// --- serialized instance variables:
/**
* The reference type for keys. Must be HARD, SOFT, WEAK.
* Note: I originally marked this field as final, but then this class
* didn't compile under JDK1.2.2.
* @serial
*/
private int keyType;
/**
* The reference type for values. Must be HARD, SOFT, WEAK.
* Note: I originally marked this field as final, but then this class
* didn't compile under JDK1.2.2.
* @serial
*/
private int valueType;
/**
* The threshold variable is calculated by multiplying
* table.length and loadFactor.
* Note: I originally marked this field as final, but then this class
* didn't compile under JDK1.2.2.
* @serial
*/
private float loadFactor;
/**
* Should the value be automatically purged when the associated key has been collected?
*/
private boolean purgeValues = false;
// -- Non-serialized instance variables
/**
* ReferenceQueue used to eliminate stale mappings.
* See purge.
*/
private transient ReferenceQueue queue = new ReferenceQueue();
/**
* Constructs a new <code>ReferenceMap</code> that will
* use hard references to keys and soft references to values.
* Constructs a new <code>ReferenceMap</code> that will
* use hard references to keys and soft references to values.
*/
public ReferenceMap() {
this(HARD, SOFT);
super(HARD, SOFT, DEFAULT_CAPACITY, DEFAULT_LOAD_FACTOR, false);
}
/**
* Constructs a new <code>ReferenceMap</code> that will
* use the specified types of references.
* Constructs a new <code>ReferenceMap</code> that will
* use the specified types of references.
*
* @param keyType the type of reference to use for keys;
* @param keyType the type of reference to use for keys;
* must be {@link #HARD}, {@link #SOFT}, {@link #WEAK}
* @param valueType the type of reference to use for values;
* must be {@link #HARD}, {@link #SOFT}, {@link #WEAK}
* @param purgeValues should the value be automatically purged when the
* key is garbage collected
*/
public ReferenceMap(int keyType, int valueType, boolean purgeValues) {
this(keyType, valueType);
this.purgeValues = purgeValues;
}
/**
* Constructs a new <code>ReferenceMap</code> that will
* use the specified types of references.
*
* @param keyType the type of reference to use for keys;
* must be {@link #HARD}, {@link #SOFT}, {@link #WEAK}
* @param valueType the type of reference to use for values;
* @param valueType the type of reference to use for values;
* must be {@link #HARD}, {@link #SOFT}, {@link #WEAK}
*/
public ReferenceMap(int keyType, int valueType) {
this(keyType, valueType, 16, 0.75f);
super(keyType, valueType, DEFAULT_CAPACITY, DEFAULT_LOAD_FACTOR, false);
}
/**
* Constructs a new <code>ReferenceMap</code> with the
* specified reference types, load factor and initial
* capacity.
* Constructs a new <code>ReferenceMap</code> that will
* use the specified types of references.
*
* @param keyType the type of reference to use for keys;
* @param keyType the type of reference to use for keys;
* must be {@link #HARD}, {@link #SOFT}, {@link #WEAK}
* @param valueType the type of reference to use for values;
* @param valueType the type of reference to use for values;
* must be {@link #HARD}, {@link #SOFT}, {@link #WEAK}
* @param capacity the initial capacity for the map
* @param loadFactor the load factor for the map
* @param purgeValues should the value be automatically purged when the
* @param purgeValues should the value be automatically purged when the
* key is garbage collected
*/
public ReferenceMap(int keyType, int valueType, int capacity,
float loadFactor, boolean purgeValues) {
this(keyType, valueType, capacity, loadFactor);
this.purgeValues = purgeValues;
public ReferenceMap(int keyType, int valueType, boolean purgeValues) {
super(keyType, valueType, DEFAULT_CAPACITY, DEFAULT_LOAD_FACTOR, purgeValues);
}
/**
* Constructs a new <code>ReferenceMap</code> with the
* specified reference types, load factor and initial
* capacity.
* Constructs a new <code>ReferenceMap</code> with the
* specified reference types, load factor and initial
* capacity.
*
* @param keyType the type of reference to use for keys;
* @param keyType the type of reference to use for keys;
* must be {@link #HARD}, {@link #SOFT}, {@link #WEAK}
* @param valueType the type of reference to use for values;
* @param valueType the type of reference to use for values;
* must be {@link #HARD}, {@link #SOFT}, {@link #WEAK}
* @param capacity the initial capacity for the map
* @param loadFactor the load factor for the map
* @param capacity the initial capacity for the map
* @param loadFactor the load factor for the map
*/
public ReferenceMap(int keyType, int valueType, int capacity, float loadFactor) {
super(capacity, loadFactor);
verify("keyType", keyType);
verify("valueType", valueType);
this.keyType = keyType;
this.valueType = valueType;
super(keyType, valueType, capacity, loadFactor, false);
}
/**
* Checks the type int is a valid value.
*
* @param name the name for error messages
* @param type the type value to check
* @throws IllegalArgumentException if the value if invalid
*/
private static void verify(String name, int type) {
if ((type < HARD) || (type > WEAK)) {
throw new IllegalArgumentException(name + " must be HARD, SOFT, WEAK.");
}
}
/**
* Writes this object to the given output stream.
* Constructs a new <code>ReferenceMap</code> with the
* specified reference types, load factor and initial
* capacity.
*
* @param out the output stream to write to
* @throws IOException if the stream raises it
* @param keyType the type of reference to use for keys;
* must be {@link #HARD}, {@link #SOFT}, {@link #WEAK}
* @param valueType the type of reference to use for values;
* must be {@link #HARD}, {@link #SOFT}, {@link #WEAK}
* @param capacity the initial capacity for the map
* @param loadFactor the load factor for the map
* @param purgeValues should the value be automatically purged when the
* key is garbage collected
*/
private void writeObject(ObjectOutputStream out) throws IOException {
out.defaultWriteObject();
out.writeInt(data.length);
// Have to use null-terminated list because size might shrink
// during iteration
for (Iterator iter = entrySet().iterator(); iter.hasNext();) {
Map.Entry entry = (Map.Entry)iter.next();
out.writeObject(entry.getKey());
out.writeObject(entry.getValue());
}
out.writeObject(null);
public ReferenceMap(int keyType, int valueType, int capacity,
float loadFactor, boolean purgeValues) {
super(keyType, valueType, capacity, loadFactor, purgeValues);
}
/**
* Reads the contents of this object from the given input stream.
*
* @param in the input stream to read from
* @throws IOException if the stream raises it
* @throws ClassNotFoundException if the stream raises it
*/
private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
in.defaultReadObject();
data = new HashEntry[in.readInt()];
threshold = calculateThreshold(data.length, loadFactor);
queue = new ReferenceQueue();
Object key = in.readObject();
while (key != null) {
Object value = in.readObject();
put(key, value);
key = in.readObject();
}
}
/**
* Gets the entry mapped to the key specified.
*
* @param key the key
* @return the entry, null if no match
* @since Commons Collections 3.1
*/
protected HashEntry getEntry(Object key) {
if (key == null) {
return null;
} else {
return super.getEntry(key);
}
}
//-----------------------------------------------------------------------
/**
* Purges stale mappings from this map before read operations.
* <p>
* This implementation calls {@link #purge()} to maintain a consistent state.
*
* @since Commons Collections 3.1
*/
protected void purgeBeforeRead() {
purge();
}
/**
* Purges stale mappings from this map before write operations.
* <p>
* This implementation calls {@link #purge()} to maintain a consistent state.
*
* @since Commons Collections 3.1
*/
protected void purgeBeforeWrite() {
purge();
}
/**
* Purges stale mappings from this map.
* <p>
* Note that this method is not synchronized! Special
* care must be taken if, for instance, you want stale
* mappings to be removed on a periodic basis by some
* background thread.
*
* @since Commons Collections 3.1
*/
protected void purge() {
Reference ref = queue.poll();
while (ref != null) {
purge(ref);
ref = queue.poll();
}
}
private void purge(Reference ref) {
// The hashCode of the reference is the hashCode of the
// mapping key, even if the reference refers to the
// mapping value...
int hash = ref.hashCode();
int index = hashIndex(hash, data.length);
HashEntry previous = null;
HashEntry entry = data[index];
while (entry != null) {
if (((ReferenceEntry) entry).purge(ref)) {
if (previous == null) {
data[index] = entry.next;
} else {
previous.next = entry.next;
}
this.size--;
return;
}
previous = entry;
entry = entry.next;
}
}
//-----------------------------------------------------------------------
/**
* Gets the size of the map.
*
* @return the size
*/
public int size() {
purgeBeforeRead();
return super.size();
}
/**
* Checks whether the map is currently empty.
*
* @return true if the map is currently size zero
*/
public boolean isEmpty() {
purgeBeforeRead();
return super.isEmpty();
}
/**
* Checks whether the map contains the specified key.
*
* @param key the key to search for
* @return true if the map contains the key
*/
public boolean containsKey(Object key) {
purgeBeforeRead();
Entry entry = getEntry(key);
if (entry == null) {
return false;
}
return (entry.getValue() != null);
}
/**
* Checks whether the map contains the specified value.
*
* @param value the value to search for
* @return true if the map contains the value
*/
public boolean containsValue(Object value) {
purgeBeforeRead();
if (value == null) {
return false;
}
return super.containsValue(value);
}
/**
* Gets the value mapped to the key specified.
*
* @param key the key
* @return the mapped value, null if no match
*/
public Object get(Object key) {
purgeBeforeRead();
Entry entry = getEntry(key);
if (entry == null) {
return null;
}
return entry.getValue();
}
/**
* Puts a key-value mapping into this map.
* Neither the key nor the value may be null.
*
* @param key the key to add, must not be null
* @param value the value to add, must not be null
* @return the value previously mapped to this key, null if none
* @throws NullPointerException if either the key or value is null
*/
public Object put(Object key, Object value) {
if (key == null) {
throw new NullPointerException("null keys not allowed");
}
if (value == null) {
throw new NullPointerException("null values not allowed");
}
purgeBeforeWrite();
return super.put(key, value);
}
/**
* Removes the specified mapping from this map.
*
* @param key the mapping to remove
* @return the value mapped to the removed key, null if key not in map
*/
public Object remove(Object key) {
if (key == null) {
return null;
}
purgeBeforeWrite();
return super.remove(key);
}
/**
* Clears this map.
*/
public void clear() {
super.clear();
while (queue.poll() != null) {} // drain the queue
}
//-----------------------------------------------------------------------
/**
* Compares two keys, in internal converted form, to see if they are equal.
* <p>
* This implementation converts the key from the entry to a real reference
* before comparison.
*
* @param key1 the first key to compare passed in from outside
* @param key2 the second key extracted from the entry via <code>entry.key</code>
* @return true if equal
* @since Commons Collections 3.1
*/
protected boolean isEqualKey(Object key1, Object key2) {
key2 = (keyType > HARD ? ((Reference) key2).get() : key2);
return (key1 == key2 || key1.equals(key2));
}
//-----------------------------------------------------------------------
/**
* Creates a ReferenceEntry instead of a HashEntry.
*
* @param next the next entry in sequence
* @param hashCode the hash code to use
* @param key the key to store
* @param value the value to store
* @return the newly created entry
* @since Commons Collections 3.1
*/
protected HashEntry createEntry(HashEntry next, int hashCode, Object key, Object value) {
return new ReferenceEntry(this, next, hashCode, key, value);
}
/**
* Creates an entry set iterator.
*
* @return the entrySet iterator
* @since Commons Collections 3.1
*/
protected Iterator createEntrySetIterator() {
return new ReferenceEntrySetIterator(this);
}
/**
* Creates an key set iterator.
*
* @return the keySet iterator
* @since Commons Collections 3.1
*/
protected Iterator createKeySetIterator() {
return new ReferenceKeySetIterator(this);
}
/**
* Creates an values iterator.
*
* @return the values iterator
* @since Commons Collections 3.1
*/
protected Iterator createValuesIterator() {
return new ReferenceValuesIterator(this);
}
//-----------------------------------------------------------------------
/**
* Returns a set view of this map's entries.
* The <code>setValue()</code> method on the entries has no effect.
*
* @return a set view of this map's entries
*/
public Set entrySet() {
if (entrySet == null) {
entrySet = new ReferenceEntrySet(this);
}
return entrySet;
}
/**
* EntrySet implementation.
*/
static class ReferenceEntrySet extends EntrySet {
protected ReferenceEntrySet(AbstractHashedMap parent) {
super(parent);
}
public Object[] toArray() {
return toArray(new Object[0]);
}
public Object[] toArray(Object[] arr) {
// special implementation to handle disappearing entries
ArrayList list = new ArrayList();
Iterator iterator = iterator();
while (iterator.hasNext()) {
Entry e = (Entry) iterator.next();
list.add(new DefaultMapEntry(e.getKey(), e.getValue()));
}
return list.toArray(arr);
}
}
//-----------------------------------------------------------------------
/**
* Returns a set view of this map's keys.
*
* @return a set view of this map's keys
*/
public Set keySet() {
if (keySet == null) {
keySet = new ReferenceKeySet(this);
}
return keySet;
}
/**
* KeySet implementation.
*/
static class ReferenceKeySet extends KeySet {
protected ReferenceKeySet(AbstractHashedMap parent) {
super(parent);
}
public Object[] toArray() {
return toArray(new Object[0]);
}
public Object[] toArray(Object[] arr) {
// special implementation to handle disappearing keys
List list = new ArrayList(parent.size());
for (Iterator it = iterator(); it.hasNext(); ) {
list.add(it.next());
}
return list.toArray(arr);
}
}
//-----------------------------------------------------------------------
/**
* Returns a collection view of this map's values.
*
* @return a set view of this map's values
*/
public Collection values() {
if (values == null) {
values = new ReferenceValues(this);
}
return values;
}
/**
* Values implementation.
*/
static class ReferenceValues extends Values {
protected ReferenceValues(AbstractHashedMap parent) {
super(parent);
}
public Object[] toArray() {
return toArray(new Object[0]);
}
public Object[] toArray(Object[] arr) {
// special implementation to handle disappearing values
List list = new ArrayList(parent.size());
for (Iterator it = iterator(); it.hasNext(); ) {
list.add(it.next());
}
return list.toArray(arr);
}
}
//-----------------------------------------------------------------------
/**
* A MapEntry implementation for the map.
* <p>
* If getKey() or getValue() returns null, it means
* the mapping is stale and should be removed.
*/
protected static class ReferenceEntry extends HashEntry {
/** The parent map */
protected final ReferenceMap parent;
/**
* Creates a new entry object for the ReferenceMap.
*
* @param parent the parent map
* @param next the next entry in the hash bucket
* @param hashCode the hash code of the key
* @param key the key
* @param value the value
*/
public ReferenceEntry(ReferenceMap parent, HashEntry next, int hashCode, Object key, Object value) {
super(next, hashCode, null, null);
this.parent = parent;
this.key = toReference(parent.keyType, key, hashCode);
this.value = toReference(parent.valueType, value, hashCode);
}
public Object getKey() {
return (parent.keyType > HARD) ? ((Reference) key).get() : key;
}
public Object getValue() {
return (parent.valueType > HARD) ? ((Reference) value).get() : value;
}
public Object setValue(Object obj) {
Object old = getValue();
if (parent.valueType > HARD) {
((Reference)value).clear();
}
value = toReference(parent.valueType, obj, hashCode);
return old;
}
public boolean equals(Object obj) {
if (obj == this) {
return true;
}
if (obj instanceof Map.Entry == false) {
return false;
}
Map.Entry entry = (Map.Entry)obj;
Object key = entry.getKey();
Object value = entry.getValue();
if ((key == null) || (value == null)) {
return false;
}
return key.equals(getKey()) && value.equals(getValue());
}
/**
* Constructs a reference of the given type to the given referent.
* The reference is registered with the queue for later purging.
*
* @param type HARD, SOFT or WEAK
* @param referent the object to refer to
* @param hash the hash code of the <i>key</i> of the mapping;
* this number might be different from referent.hashCode() if
* the referent represents a value and not a key
* @since Commons Collections 3.1
*/
protected Object toReference(int type, Object referent, int hash) {
switch (type) {
case HARD: return referent;
case SOFT: return new SoftRef(hash, referent, parent.queue);
case WEAK: return new WeakRef(hash, referent, parent.queue);
default: throw new Error();
}
}
boolean purge(Reference ref) {
boolean r = (parent.keyType > HARD) && (key == ref);
r = r || ((parent.valueType > HARD) && (value == ref));
if (r) {
if (parent.keyType > HARD) {
((Reference)key).clear();
}
if (parent.valueType > HARD) {
((Reference)value).clear();
} else if (parent.purgeValues) {
value = null;
}
}
return r;
}
ReferenceEntry next() {
return (ReferenceEntry) next;
}
}
//-----------------------------------------------------------------------
/**
* The EntrySet iterator.
*/
static class ReferenceEntrySetIterator implements Iterator {
/** The parent map */
final ReferenceMap parent;
// These fields keep track of where we are in the table.
int index;
ReferenceEntry entry;
ReferenceEntry previous;
// These Object fields provide hard references to the
// current and next entry; this assures that if hasNext()
// returns true, next() will actually return a valid element.
Object nextKey, nextValue;
Object currentKey, currentValue;
int expectedModCount;
public ReferenceEntrySetIterator(ReferenceMap parent) {
super();
this.parent = parent;
index = (parent.size() != 0 ? parent.data.length : 0);
// have to do this here! size() invocation above
// may have altered the modCount.
expectedModCount = parent.modCount;
}
public boolean hasNext() {
checkMod();
while (nextNull()) {
ReferenceEntry e = entry;
int i = index;
while ((e == null) && (i > 0)) {
i--;
e = (ReferenceEntry) parent.data[i];
}
entry = e;
index = i;
if (e == null) {
currentKey = null;
currentValue = null;
return false;
}
nextKey = e.getKey();
nextValue = e.getValue();
if (nextNull()) {
entry = entry.next();
}
}
return true;
}
private void checkMod() {
if (parent.modCount != expectedModCount) {
throw new ConcurrentModificationException();
}
}
private boolean nextNull() {
return (nextKey == null) || (nextValue == null);
}
protected Entry nextEntry() {
checkMod();
if (nextNull() && !hasNext()) {
throw new NoSuchElementException();
}
previous = entry;
entry = entry.next();
currentKey = nextKey;
currentValue = nextValue;
nextKey = null;
nextValue = null;
return previous;
}
public Object next() {
return nextEntry();
}
public void remove() {
checkMod();
if (previous == null) {
throw new IllegalStateException();
}
parent.remove(currentKey);
previous = null;
currentKey = null;
currentValue = null;
expectedModCount = parent.modCount;
}
}
/**
* The keySet iterator.
*/
static class ReferenceKeySetIterator extends ReferenceEntrySetIterator {
ReferenceKeySetIterator(ReferenceMap parent) {
super(parent);
}
public Object next() {
return nextEntry().getKey();
}
}
/**
* The values iterator.
*/
static class ReferenceValuesIterator extends ReferenceEntrySetIterator {
ReferenceValuesIterator(ReferenceMap parent) {
super(parent);
}
public Object next() {
return nextEntry().getValue();
}
}
//-----------------------------------------------------------------------
// These two classes store the hashCode of the key of
// of the mapping, so that after they're dequeued a quick
// lookup of the bucket in the table can occur.
/**
* A soft reference holder.
*/
static class SoftRef extends SoftReference {
private int hash;
public SoftRef(int hash, Object r, ReferenceQueue q) {
super(r, q);
this.hash = hash;
}
public int hashCode() {
return hash;
}
}
/**
* A weak reference holder.
*/
static class WeakRef extends WeakReference {
private int hash;
public WeakRef(int hash, Object r, ReferenceQueue q) {
super(r, q);
this.hash = hash;
}
public int hashCode() {
return hash;
}
}
}

48
src/test/org/apache/commons/collections/map/TestReferenceMap.java
View File

@ -25,7 +25,7 @@ import org.apache.commons.collections.BulkTest;
/**
* Tests for ReferenceMap.
*
* @version $Revision: 1.4 $ $Date: 2004/04/01 00:07:48 $
* @version $Revision: 1.5 $ $Date: 2004/04/09 22:18:17 $
*
* @author Paul Jack
*/
@ -125,8 +125,52 @@ public class TestReferenceMap extends AbstractTestIterableMap {
}
}
*/
public void testMapIteratorAfterGC() {
ReferenceMap map = new ReferenceMap(ReferenceMap.WEAK, ReferenceMap.WEAK);
Object[] hard = new Object[10];
for (int i = 0; i < 10; i++) {
hard[i] = new Integer(10 + i);
map.put(new Integer(i), new Integer(i));
map.put(hard[i], hard[i]);
}
System.gc();
MapIterator iterator = map.mapIterator();
while (iterator.hasNext()) {
Object key1 = iterator.next();
Integer key = (Integer) iterator.getKey();
Integer value = (Integer) iterator.getValue();
assertTrue("iterator keys should match", key == key1);
assertTrue("iterator should skip GC'd keys", key.intValue() >= 10);
assertTrue("iterator should skip GC'd values", value.intValue() >= 10);
}
}
public void testMapIteratorAfterGC2() {
ReferenceMap map = new ReferenceMap(ReferenceMap.WEAK, ReferenceMap.WEAK);
Object[] hard = new Object[10];
for (int i = 0; i < 10; i++) {
hard[i] = new Integer(10 + i);
map.put(new Integer(i), new Integer(i));
map.put(hard[i], hard[i]);
}
MapIterator iterator = map.mapIterator();
while (iterator.hasNext()) {
Object key1 = iterator.next();
System.gc();
Integer key = (Integer) iterator.getKey();
Integer value = (Integer) iterator.getValue();
assertTrue("iterator keys should match", key == key1);
assertTrue("iterator should skip GC'd keys", key.intValue() >= 10);
assertTrue("iterator should skip GC'd values", value.intValue() >= 10);
}
}
*/
/*
// Uncomment to create test files in /data/test