This is an automated email from the ASF dual-hosted git repository.
sunlan pushed a commit to branch danielsun/tweak-ManagedIdentityConcurrentMap
in repository https://gitbox.apache.org/repos/asf/groovy.git
commit e113c6f412c2454ef99285d81a6e6b32e756bb8f
Author: Daniel Sun <sun...@apache.org>
AuthorDate: Fri Jul 31 07:29:45 2020 +0800
Add `ConcurrentIdentityHashMap`
---
.../groovy/util/ConcurrentReferenceHashMap.java | 2046 ++++++++++++++++++++
1 file changed, 2046 insertions(+)
diff --git
a/src/main/java/org/codehaus/groovy/util/ConcurrentReferenceHashMap.java
b/src/main/java/org/codehaus/groovy/util/ConcurrentReferenceHashMap.java
new file mode 100644
index 0000000..171e4f1
--- /dev/null
+++ b/src/main/java/org/codehaus/groovy/util/ConcurrentReferenceHashMap.java
@@ -0,0 +1,2046 @@
+/*
+ * Copyright (c) 2008-2020, Hazelcast, Inc. All Rights Reserved.
+ *
+ * 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.codehaus.groovy.util;
+
+/*
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/licenses/publicdomain
+ */
+
+import com.hazelcast.internal.serialization.SerializableByConvention;
+import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
+
+import java.io.IOException;
+import java.io.Serializable;
+import java.lang.ref.Reference;
+import java.lang.ref.ReferenceQueue;
+import java.lang.ref.SoftReference;
+import java.lang.ref.WeakReference;
+import java.util.AbstractCollection;
+import java.util.AbstractMap;
+import java.util.AbstractSet;
+import java.util.Collection;
+import java.util.ConcurrentModificationException;
+import java.util.EnumSet;
+import java.util.Enumeration;
+import java.util.HashMap;
+import java.util.Hashtable;
+import java.util.IdentityHashMap;
+import java.util.Iterator;
+import java.util.Map;
+import java.util.NoSuchElementException;
+import java.util.Set;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.BiFunction;
+import java.util.function.Function;
+
+import static com.hazelcast.internal.util.Preconditions.checkNotNull;
+
+/**
+ * An advanced hash table supporting configurable garbage collection semantics
+ * of keys and values, optional referential-equality, full concurrency of
+ * retrievals, and adjustable expected concurrency for updates.
+ * <p>
+ * This table is designed around specific advanced use-cases. If there is any
+ * doubt whether this table is for you, you most likely should be using
+ * {@link java.util.concurrent.ConcurrentHashMap} instead.
+ * <p>
+ * This table supports strong, weak, and soft keys and values. By default keys
+ * are weak, and values are strong. Such a configuration offers similar
behavior
+ * to {@link java.util.WeakHashMap}, entries of this table are periodically
+ * removed once their corresponding keys are no longer referenced outside of
+ * this table. In other words, this table will not prevent a key from being
+ * discarded by the garbage collector. Once a key has been discarded by the
+ * collector, the corresponding entry is no longer visible to this table;
+ * however, the entry may occupy space until a future table operation decides
to
+ * reclaim it. For this reason, summary functions such as <tt>size</tt> and
+ * <tt>isEmpty</tt> might return a value greater than the observed number of
+ * entries. In order to support a high level of concurrency, stale entries are
+ * only reclaimed during blocking (usually mutating) operations.
+ * <p>
+ * Enabling soft keys allows entries in this table to remain until their space
+ * is absolutely needed by the garbage collector. This is unlike weak keys
which
+ * can be reclaimed as soon as they are no longer referenced by a normal strong
+ * reference. The primary use case for soft keys is a cache, which ideally
+ * occupies memory that is not in use for as long as possible.
+ * <p>
+ * By default, values are held using a normal strong reference. This provides
+ * the commonly desired guarantee that a value will always have at least the
+ * same life-span as it's key. For this reason, care should be taken to ensure
+ * that a value never refers, either directly or indirectly, to its key,
thereby
+ * preventing reclamation. If this is unavoidable, then it is recommended to
use
+ * the same reference type in use for the key. However, it should be noted that
+ * non-strong values may disappear before their corresponding key.
+ * <p>
+ * While this table does allow the use of both strong keys and values, it is
+ * recommended you use {@link java.util.concurrent.ConcurrentHashMap} for such
a
+ * configuration, since it is optimized for that case.
+ * <p>
+ * Just like {@link java.util.concurrent.ConcurrentHashMap}, this class obeys
+ * the same functional specification as {@link Hashtable}, and
+ * includes versions of methods corresponding to each method of
+ * <tt>Hashtable</tt>. However, even though all operations are thread-safe,
+ * retrieval operations do <em>not</em> entail locking, and there is
+ * <em>not</em> any support for locking the entire table in a way that
+ * prevents all access. This class is fully interoperable with
+ * <tt>Hashtable</tt> in programs that rely on its thread safety but not on
+ * its synchronization details.
+ * <p>
+ * <p>
+ * Retrieval operations (including <tt>get</tt>) generally do not block, so
they
+ * may overlap with update operations (including <tt>put</tt> and
+ * <tt>remove</tt>). Retrievals reflect the results of the most recently
+ * <em>completed</em> update operations holding upon their onset. For
+ * aggregate operations such as <tt>putAll</tt> and <tt>clear</tt>,
+ * concurrent retrievals may reflect insertion or removal of only some entries.
+ * Similarly, Iterators and Enumerations return elements reflecting the state
of
+ * the hash table at some point at or since the creation of the
+ * iterator/enumeration. They do <em>not</em> throw
+ * {@link ConcurrentModificationException}. However, iterators are designed to
+ * be used by only one thread at a time.
+ * <p>
+ * <p>
+ * The allowed concurrency among update operations is guided by the optional
+ * <tt>concurrencyLevel</tt> constructor argument (default <tt>16</tt>),
+ * which is used as a hint for internal sizing. The table is internally
+ * partitioned to try to permit the indicated number of concurrent updates
+ * without contention. Because placement in hash tables is essentially random,
+ * the actual concurrency will vary. Ideally, you should choose a value to
+ * accommodate as many threads as will ever concurrently modify the table.
Using
+ * a significantly higher value than you need can waste space and time, and a
+ * significantly lower value can lead to thread contention. But overestimates
+ * and underestimates within an order of magnitude do not usually have much
+ * noticeable impact. A value of one is appropriate when it is known that only
+ * one thread will modify and all others will only read. Also, resizing this or
+ * any other kind of hash table is a relatively slow operation, so, when
+ * possible, it is a good idea that you provide estimates of expected table
sizes in
+ * constructors.
+ * <p>
+ * <p>
+ * This class and its views and iterators implement all of the
<em>optional</em>
+ * methods of the {@link Map} and {@link Iterator} interfaces.
+ * <p>
+ * <p>
+ * Like {@link Hashtable} but unlike {@link HashMap}, this class does
+ * <em>not</em> allow <tt>null</tt> to be used as a key or value.
+ * <p>
+ * <p>
+ * This class is a member of the <a
href="{@docRoot}/../technotes/guides/collections/index.html">
+ * Java Collections Framework</a>.
+ *
+ * @param <K> the type of keys maintained by this map
+ * @param <V> the type of mapped values
+ * @author Doug Lea
+ * @author Jason T. Greene
+ */
+@SuppressWarnings("all")
+@SerializableByConvention
+public class ConcurrentReferenceHashMap<K, V> extends AbstractMap<K, V>
+ implements com.hazelcast.internal.util.IConcurrentMap<K, V>,
Serializable {
+
+ /*
+ * The basic strategy is to subdivide the table among Segments,
+ * each of which itself is a concurrently readable hash table.
+ */
+
+ /**
+ * An option specifying which Java reference type should be used to refer
+ * to a key and/or value.
+ */
+ public static enum ReferenceType {
+ /**
+ * Indicates a normal Java strong reference should be used
+ */
+ STRONG,
+ /**
+ * Indicates a {@link WeakReference} should be used
+ */
+ WEAK,
+ /**
+ * Indicates a {@link SoftReference} should be used
+ */
+ SOFT
+ }
+
+ ;
+
+ /**
+ * Behavior-changing configuration options for the map
+ */
+ public static enum Option {
+ /**
+ * Indicates that referential-equality (== instead of .equals()) should
+ * be used when locating keys. This offers similar behavior to {@link
IdentityHashMap}
+ */
+ IDENTITY_COMPARISONS
+ }
+
+ ;
+
+ /* ---------------- Constants -------------- */
+
+ static final ReferenceType DEFAULT_KEY_TYPE = ReferenceType.WEAK;
+
+ static final ReferenceType DEFAULT_VALUE_TYPE = ReferenceType.STRONG;
+
+
+ /**
+ * The default initial capacity for this table,
+ * used when not otherwise specified in a constructor.
+ */
+ static final int DEFAULT_INITIAL_CAPACITY = 16;
+
+ /**
+ * The default load factor for this table, used when not
+ * otherwise specified in a constructor.
+ */
+ static final float DEFAULT_LOAD_FACTOR = 0.75f;
+
+ /**
+ * The default concurrency level for this table, used when not
+ * otherwise specified in a constructor.
+ */
+ static final int DEFAULT_CONCURRENCY_LEVEL = 16;
+
+ /**
+ * The maximum capacity, used if a higher value is implicitly
+ * specified by either of the constructors with arguments. MUST
+ * be a power of two <= 1<<30 to ensure that entries are indexable
+ * using ints.
+ */
+ static final int MAXIMUM_CAPACITY = 1 << 30;
+
+ /**
+ * The maximum number of segments to allow; used to bound
+ * constructor arguments.
+ */
+ static final int MAX_SEGMENTS = 1 << 16;
+
+ /**
+ * Number of unsynchronized retries in size and containsValue
+ * methods before resorting to locking. This is used to avoid
+ * unbounded retries if tables undergo continuous modification
+ * which would make it impossible to obtain an accurate result.
+ */
+ static final int RETRIES_BEFORE_LOCK = 2;
+
+ private static final long serialVersionUID = 7249069246763182397L;
+
+ /* ---------------- Fields -------------- */
+
+ /**
+ * Mask value for indexing into segments. The upper bits of a
+ * key's hash code are used to choose the segment.
+ */
+ final int segmentMask;
+
+ /**
+ * Shift value for indexing within segments.
+ */
+ final int segmentShift;
+
+ /**
+ * The segments, each of which is a specialized hash table
+ */
+ final Segment<K, V>[] segments;
+
+ boolean identityComparisons;
+
+ transient Set<K> keySet;
+ transient Set<Entry<K, V>> entrySet;
+ transient Collection<V> values;
+
+ /* ---------------- Small Utilities -------------- */
+
+ /**
+ * Applies a supplemental hash function to a given hashCode, which
+ * defends against poor quality hash functions. This is critical
+ * because ConcurrentReferenceHashMap uses power-of-two length hash tables,
+ * that otherwise encounter collisions for hashCodes that do not
+ * differ in lower or upper bits.
+ */
+ private static int hash(int h) {
+ // Spread bits to regularize both segment and index locations,
+ // using variant of single-word Wang/Jenkins hash.
+ h += (h << 15) ^ 0xffffcd7d;
+ h ^= (h >>> 10);
+ h += (h << 3);
+ h ^= (h >>> 6);
+ h += (h << 2) + (h << 14);
+ return h ^ (h >>> 16);
+ }
+
+ /**
+ * Returns the segment that should be used for key with given hash
+ *
+ * @param hash the hash code for the key
+ * @return the segment
+ */
+ final Segment<K, V> segmentFor(int hash) {
+ return segments[(hash >>> segmentShift) & segmentMask];
+ }
+
+ protected int hashOf(Object key) {
+ return hash(identityComparisons ? System.identityHashCode(key) :
key.hashCode());
+ }
+
+ /* ---------------- Inner Classes -------------- */
+
+ interface KeyReference {
+ int keyHash();
+
+ Object keyRef();
+ }
+
+ /**
+ * A weak-key reference which stores the key hash needed for reclamation.
+ */
+ static final class WeakKeyReference<K> extends WeakReference<K> implements
KeyReference {
+ final int hash;
+
+ WeakKeyReference(K key, int hash, ReferenceQueue<Object> refQueue) {
+ super(key, refQueue);
+ this.hash = hash;
+ }
+
+ public final int keyHash() {
+ return hash;
+ }
+
+ public final Object keyRef() {
+ return this;
+ }
+ }
+
+ /**
+ * A soft-key reference which stores the key hash needed for reclamation.
+ */
+ static final class SoftKeyReference<K> extends SoftReference<K> implements
KeyReference {
+ final int hash;
+
+ SoftKeyReference(K key, int hash, ReferenceQueue<Object> refQueue) {
+ super(key, refQueue);
+ this.hash = hash;
+ }
+
+ public final int keyHash() {
+ return hash;
+ }
+
+ public final Object keyRef() {
+ return this;
+ }
+ }
+
+ static final class WeakValueReference<V> extends WeakReference<V>
implements KeyReference {
+ final Object keyRef;
+ final int hash;
+
+ WeakValueReference(V value, Object keyRef, int hash,
ReferenceQueue<Object> refQueue) {
+ super(value, refQueue);
+ this.keyRef = keyRef;
+ this.hash = hash;
+ }
+
+ public final int keyHash() {
+ return hash;
+ }
+
+ public final Object keyRef() {
+ return keyRef;
+ }
+ }
+
+ static final class SoftValueReference<V> extends SoftReference<V>
implements KeyReference {
+ final Object keyRef;
+ final int hash;
+
+ SoftValueReference(V value, Object keyRef, int hash,
ReferenceQueue<Object> refQueue) {
+ super(value, refQueue);
+ this.keyRef = keyRef;
+ this.hash = hash;
+ }
+
+ public final int keyHash() {
+ return hash;
+ }
+
+ public final Object keyRef() {
+ return keyRef;
+ }
+ }
+
+ /**
+ * ConcurrentReferenceHashMap list entry. Note that this is never exported
+ * out as a user-visible Map.Entry.
+ * <p>
+ * Because the value field is volatile, not final, it is legal wrt
+ * the Java Memory Model for an unsynchronized reader to see null
+ * instead of initial value when read via a data race. Although a
+ * reordering leading to this is not likely to ever actually
+ * occur, the Segment.readValueUnderLock method is used as a
+ * backup in case a null (pre-initialized) value is ever seen in
+ * an unsynchronized access method.
+ */
+ static final class HashEntry<K, V> {
+ final Object keyRef;
+ final int hash;
+ volatile Object valueRef;
+ final HashEntry<K, V> next;
+
+ HashEntry(K key, int hash, HashEntry<K, V> next, V value,
+ ReferenceType keyType, ReferenceType valueType,
+ ReferenceQueue<Object> refQueue) {
+ this.hash = hash;
+ this.next = next;
+ this.keyRef = newKeyReference(key, keyType, refQueue);
+ this.valueRef = newValueReference(value, valueType, refQueue);
+ }
+
+ final Object newKeyReference(K key, ReferenceType keyType,
+ ReferenceQueue<Object> refQueue) {
+ if (keyType == ReferenceType.WEAK) {
+ return new WeakKeyReference<K>(key, hash, refQueue);
+ }
+ if (keyType == ReferenceType.SOFT) {
+ return new SoftKeyReference<K>(key, hash, refQueue);
+ }
+
+ return key;
+ }
+
+ final Object newValueReference(V value, ReferenceType valueType,
+ ReferenceQueue<Object> refQueue) {
+ if (valueType == ReferenceType.WEAK) {
+ return new WeakValueReference<V>(value, keyRef, hash,
refQueue);
+ }
+ if (valueType == ReferenceType.SOFT) {
+ return new SoftValueReference<V>(value, keyRef, hash,
refQueue);
+ }
+
+ return value;
+ }
+
+ @SuppressWarnings("unchecked")
+ final K key() {
+ if (keyRef instanceof KeyReference) {
+ return ((Reference<K>) keyRef).get();
+ }
+ return (K) keyRef;
+ }
+
+ final V value() {
+ return dereferenceValue(valueRef);
+ }
+
+ @SuppressWarnings("unchecked")
+ final V dereferenceValue(Object value) {
+ if (value instanceof KeyReference) {
+ return ((Reference<V>) value).get();
+ }
+ return (V) value;
+ }
+
+ final void setValue(V value, ReferenceType valueType,
ReferenceQueue<Object> refQueue) {
+ this.valueRef = newValueReference(value, valueType, refQueue);
+ }
+
+ @SuppressWarnings("unchecked")
+ static final <K, V> HashEntry<K, V>[] newArray(int i) {
+ return new HashEntry[i];
+ }
+ }
+
+ /**
+ * Segments are specialized versions of hash tables. This
+ * subclasses from ReentrantLock opportunistically, just to
+ * simplify some locking and avoid separate construction.
+ */
+ @SerializableByConvention
+ static final class Segment<K, V> extends ReentrantLock implements
Serializable {
+ /*
+ * Segments maintain a table of entry lists that are ALWAYS
+ * kept in a consistent state, so they can be read without locking.
+ * Next fields of nodes are immutable (final). All list
+ * additions are performed at the front of each bin. This
+ * makes it easy to check changes, and also fast to traverse.
+ * When nodes would otherwise be changed, new nodes are
+ * created to replace them. This works well for hash tables
+ * since the bin lists tend to be short. (The average length
+ * is less than two for the default load factor threshold.)
+ *
+ * Read operations can thus proceed without locking, but rely
+ * on selected uses of volatiles to ensure that completed
+ * write operations performed by other threads are
+ * noticed. For most purposes, the "count" field, tracking the
+ * number of elements, serves as that volatile variable
+ * ensuring visibility. This is convenient because this field
+ * needs to be read in many read operations anyway:
+ *
+ * - All (unsynchronized) read operations must first read the
+ * "count" field, and should not look at table entries if
+ * it is 0.
+ *
+ * - All (synchronized) write operations should write to
+ * the "count" field after structurally changing any bin.
+ * The operations must not take any action that could even
+ * momentarily cause a concurrent read operation to see
+ * inconsistent data. This is made easier by the nature of
+ * the read operations in Map. For example, no operation
+ * can reveal that the table has grown but the threshold
+ * has not yet been updated, so there are no atomicity
+ * requirements for this with respect to reads.
+ *
+ * As a guide, all critical volatile reads and writes to the
+ * count field are marked in code comments.
+ */
+
+ private static final long serialVersionUID = 2249069246763182397L;
+
+ /**
+ * The number of elements in this segment's region.
+ */
+ @SuppressFBWarnings(value = "SE_TRANSIENT_FIELD_NOT_RESTORED",
justification =
+ "I trust Doug Lea's technical decision")
+ transient volatile int count;
+
+ /**
+ * Number of updates that alter the size of the table. This is
+ * used during bulk-read methods to make sure they see a
+ * consistent snapshot: If modCounts change during a traversal
+ * of segments computing size or checking containsValue, then
+ * we might have an inconsistent view of state so (usually) we
+ * must retry.
+ */
+ @SuppressFBWarnings(value = "SE_TRANSIENT_FIELD_NOT_RESTORED",
justification =
+ "I trust Doug Lea's technical decision")
+ transient int modCount;
+
+ /**
+ * The table is rehashed when its size exceeds this threshold.
+ * (The value of this field is always <tt>(int)(capacity *
+ * loadFactor)</tt>.)
+ */
+ transient int threshold;
+
+ /**
+ * The per-segment table.
+ */
+ transient volatile HashEntry<K, V>[] table;
+
+ /**
+ * The load factor for the hash table. Even though this value
+ * is same for all segments, it is replicated to avoid needing
+ * links to outer object.
+ *
+ * @serial
+ */
+ final float loadFactor;
+
+ /**
+ * The collected weak-key reference queue for this segment.
+ * This should be (re)initialized whenever table is assigned,
+ */
+ transient volatile ReferenceQueue<Object> refQueue;
+
+ final ReferenceType keyType;
+
+ final ReferenceType valueType;
+
+ final boolean identityComparisons;
+
+ Segment(int initialCapacity, float lf, ReferenceType keyType,
+ ReferenceType valueType, boolean identityComparisons) {
+ loadFactor = lf;
+ this.keyType = keyType;
+ this.valueType = valueType;
+ this.identityComparisons = identityComparisons;
+ setTable(HashEntry.<K, V>newArray(initialCapacity));
+ }
+
+ @SuppressWarnings("unchecked")
+ static final <K, V> Segment<K, V>[] newArray(int i) {
+ return new Segment[i];
+ }
+
+ private boolean keyEq(Object src, Object dest) {
+ return identityComparisons ? src == dest : src.equals(dest);
+ }
+
+ /**
+ * Sets table to new HashEntry array.
+ * Call only while holding lock or in constructor.
+ */
+ void setTable(HashEntry<K, V>[] newTable) {
+ threshold = (int) (newTable.length * loadFactor);
+ table = newTable;
+ refQueue = new ReferenceQueue<Object>();
+ }
+
+ /**
+ * Returns properly casted first entry of bin for given hash.
+ */
+ HashEntry<K, V> getFirst(int hash) {
+ HashEntry<K, V>[] tab = table;
+ return tab[hash & (tab.length - 1)];
+ }
+
+ HashEntry<K, V> newHashEntry(K key, int hash, HashEntry<K, V> next, V
value) {
+ return new HashEntry<K, V>(key, hash, next, value, keyType,
valueType, refQueue);
+ }
+
+ /**
+ * Reads value field of an entry under lock. Called if value
+ * field ever appears to be null. This is possible only if a
+ * compiler happens to reorder a HashEntry initialization with
+ * its table assignment, which is legal under memory model
+ * but is not known to ever occur.
+ */
+ V readValueUnderLock(HashEntry<K, V> e) {
+ lock();
+ try {
+ removeStale();
+ return e.value();
+ } finally {
+ unlock();
+ }
+ }
+
+ /* Specialized implementations of map methods */
+
+ V get(Object key, int hash) {
+ // read-volatile
+ if (count != 0) {
+ HashEntry<K, V> e = getFirst(hash);
+ while (e != null) {
+ if (e.hash == hash && keyEq(key, e.key())) {
+ Object opaque = e.valueRef;
+ if (opaque != null) {
+ return e.dereferenceValue(opaque);
+ }
+ // recheck
+ return readValueUnderLock(e);
+ }
+ e = e.next;
+ }
+ }
+ return null;
+ }
+
+ boolean containsKey(Object key, int hash) {
+ // read-volatile
+ if (count != 0) {
+ HashEntry<K, V> e = getFirst(hash);
+ while (e != null) {
+ if (e.hash == hash && keyEq(key, e.key())) {
+ return true;
+ }
+ e = e.next;
+ }
+ }
+ return false;
+ }
+
+ boolean containsValue(Object value) {
+ // read-volatile
+ if (count != 0) {
+ HashEntry<K, V>[] tab = table;
+ int len = tab.length;
+ for (int i = 0; i < len; i++) {
+ for (HashEntry<K, V> e = tab[i]; e != null; e = e.next) {
+ Object opaque = e.valueRef;
+ V v;
+ if (opaque == null) {
+ // recheck
+ v = readValueUnderLock(e);
+ } else {
+ v = e.dereferenceValue(opaque);
+ }
+ if (value.equals(v)) {
+ return true;
+ }
+ }
+ }
+ }
+ return false;
+ }
+
+ boolean replace(K key, int hash, V oldValue, V newValue) {
+ lock();
+ try {
+ return replaceInternal2(key, hash, oldValue, newValue);
+ } finally {
+ unlock();
+ }
+ }
+
+ private boolean replaceInternal2(K key, int hash, V oldValue, V
newValue) {
+ removeStale();
+ HashEntry<K, V> e = getFirst(hash);
+ while (e != null && (e.hash != hash || !keyEq(key, e.key()))) {
+ e = e.next;
+ }
+ boolean replaced = false;
+ if (e != null && oldValue.equals(e.value())) {
+ replaced = true;
+ e.setValue(newValue, valueType, refQueue);
+ }
+ return replaced;
+ }
+
+ V replace(K key, int hash, V newValue) {
+ lock();
+ try {
+ return replaceInternal(key, hash, newValue);
+ } finally {
+ unlock();
+ }
+ }
+
+ private V replaceInternal(K key, int hash, V newValue) {
+ removeStale();
+ HashEntry<K, V> e = getFirst(hash);
+ while (e != null && (e.hash != hash || !keyEq(key, e.key()))) {
+ e = e.next;
+ }
+ V oldValue = null;
+ if (e != null) {
+ oldValue = e.value();
+ e.setValue(newValue, valueType, refQueue);
+ }
+ return oldValue;
+ }
+
+ V applyIfPresent(K key, int hash, BiFunction<? super K, ? super V, ?
extends V> remappingFunction) {
+ lock();
+ try {
+ V oldValue = get(key, hash);
+ if (oldValue == null) {
+ return null;
+ }
+
+ V newValue = remappingFunction.apply(key, oldValue);
+
+ if (newValue == null) {
+ removeInternal(key, hash, oldValue, false);
+ return null;
+ } else {
+ putInternal(key, hash, newValue, null, false);
+ return newValue;
+ }
+ } finally {
+ unlock();
+ }
+ }
+
+ V apply(K key, int hash, BiFunction<? super K, ? super V, ? extends V>
remappingFunction) {
+ lock();
+ try {
+ V oldValue = get(key, hash);
+ V newValue = remappingFunction.apply(key, oldValue);
+
+ if (newValue == null) {
+ // delete mapping
+ if (oldValue != null) {
+ // something to remove
+ removeInternal(key, hash, oldValue, false);
+ return null;
+ } else {
+ // nothing to do. Leave things as they were.
+ return null;
+ }
+ } else {
+ // add or replace old mapping
+ putInternal(key, hash, newValue, null, false);
+ return newValue;
+ }
+ } finally {
+ unlock();
+ }
+ }
+
+
+ V merge(K key, V value, int hash, BiFunction<? super V, ? super V, ?
extends V> remappingFunction) {
+ lock();
+ try {
+ V oldValue = get(key, hash);
+ V newValue = (oldValue == null) ? value :
remappingFunction.apply(oldValue, value);
+
+ if (newValue == null) {
+ removeInternal(key, hash, oldValue, false);
+ return null;
+ } else {
+ putInternal(key, hash, newValue, null, false);
+ return newValue;
+ }
+ } finally {
+ unlock();
+ }
+ }
+
+ /**
+ * This method must be called with exactly one of <code>value</code>
and
+ * <code>function</code> non-null.
+ **/
+ V put(K key, int hash, V value, Function<? super K, ? extends V>
function, boolean onlyIfAbsent) {
+ lock();
+ try {
+ return putInternal(key, hash, value, function, onlyIfAbsent);
+ } finally {
+ unlock();
+ }
+ }
+
+ private V putInternal(K key, int hash, V value, Function<? super K, ?
extends V> function, boolean onlyIfAbsent) {
+ removeStale();
+ int c = count;
+ // ensure capacity
+ if (c++ > threshold) {
+ int reduced = rehash();
+ // adjust from possible weak cleanups
+ if (reduced > 0) {
+ // write-volatile
+ count = (c -= reduced) - 1;
+ }
+ }
+ HashEntry<K, V>[] tab = table;
+ int index = hash & (tab.length - 1);
+ HashEntry<K, V> first = tab[index];
+ HashEntry<K, V> e = first;
+ while (e != null && (e.hash != hash || !keyEq(key, e.key()))) {
+ e = e.next;
+ }
+ V resultValue;
+ if (e != null) {
+ resultValue = e.value();
+ if (!onlyIfAbsent) {
+ e.setValue(getValue(key, value, function), valueType,
refQueue);
+ }
+ } else {
+ V v = getValue(key, value, function);
+ resultValue = function != null ? v : null;
+
+ if (v != null) {
+ ++modCount;
+ tab[index] = newHashEntry(key, hash, first, v);
+ // write-volatile
+ count = c;
+ }
+ }
+ return resultValue;
+ }
+
+ V getValue(K key, V value, Function<? super K, ? extends V> function) {
+ return value != null ? value : function.apply(key);
+ }
+
+ int rehash() {
+ HashEntry<K, V>[] oldTable = table;
+ int oldCapacity = oldTable.length;
+ if (oldCapacity >= MAXIMUM_CAPACITY) {
+ return 0;
+ }
+
+ /*
+ * Reclassify nodes in each list to new Map. Because we are
+ * using power-of-two expansion, the elements from each bin
+ * must either stay at the same index, or move with a power of two
+ * offset. We eliminate unnecessary node creation by catching
+ * cases where old nodes can be reused because their next
+ * fields won't change. Statistically, at the default
+ * threshold, only about one-sixth of them need cloning when
+ * a table doubles. The nodes they replace will be garbage
+ * collectable as soon as they are no longer referenced by any
+ * reader thread that may be in the midst of traversing table
+ * right now.
+ */
+
+ HashEntry<K, V>[] newTable = HashEntry.newArray(oldCapacity << 1);
+ threshold = (int) (newTable.length * loadFactor);
+ int sizeMask = newTable.length - 1;
+ int reduce = 0;
+ for (int i = 0; i < oldCapacity; i++) {
+ // We need to guarantee that any existing reads of old Map can
+ // proceed. So we cannot yet null out each bin.
+ HashEntry<K, V> e = oldTable[i];
+ if (e != null) {
+ HashEntry<K, V> next = e.next;
+ int idx = e.hash & sizeMask;
+ // Single node on list
+ if (next == null) {
+ newTable[idx] = e;
+ } else {
+ // Reuse trailing consecutive sequence at same slot
+ HashEntry<K, V> lastRun = e;
+ int lastIdx = idx;
+ for (HashEntry<K, V> last = next;
+ last != null;
+ last = last.next) {
+ int k = last.hash & sizeMask;
+ if (k != lastIdx) {
+ lastIdx = k;
+ lastRun = last;
+ }
+ }
+ newTable[lastIdx] = lastRun;
+ // Clone all remaining nodes
+ for (HashEntry<K, V> p = e; p != lastRun; p = p.next) {
+ // Skip GC'd weak refs
+ K key = p.key();
+ if (key == null) {
+ reduce++;
+ continue;
+ }
+ int k = p.hash & sizeMask;
+ HashEntry<K, V> n = newTable[k];
+ newTable[k] = newHashEntry(key, p.hash, n,
p.value());
+ }
+ }
+ }
+ }
+ table = newTable;
+ return reduce;
+ }
+
+ /**
+ * Remove: match on key only if value is null, else match both.
+ */
+ V remove(Object key, int hash, Object value, boolean refRemove) {
+ lock();
+ try {
+ return removeInternal(key, hash, value, refRemove);
+ } finally {
+ unlock();
+ }
+ }
+
+ private V removeInternal(Object key, int hash, Object value, boolean
refRemove) {
+ if (!refRemove) {
+ removeStale();
+ }
+ int c = count - 1;
+ HashEntry<K, V>[] tab = table;
+ int index = hash & (tab.length - 1);
+ HashEntry<K, V> first = tab[index];
+ HashEntry<K, V> e = first;
+ // a ref remove operation compares the Reference instance
+ while (e != null && key != e.keyRef && (refRemove || hash !=
e.hash || !keyEq(key, e.key()))) {
+ e = e.next;
+ }
+
+ V oldValue = null;
+ if (e != null) {
+ V v = e.value();
+ if (value == null || value.equals(v)) {
+ oldValue = v;
+ // All entries following removed node can stay
+ // in list, but all preceding ones need to be
+ // cloned.
+ ++modCount;
+ HashEntry<K, V> newFirst = e.next;
+ for (HashEntry<K, V> p = first; p != e; p = p.next) {
+ K pKey = p.key();
+ // Skip GC'd keys
+ if (pKey == null) {
+ c--;
+ continue;
+ }
+ newFirst = newHashEntry(pKey, p.hash, newFirst,
p.value());
+ }
+ tab[index] = newFirst;
+ // write-volatile
+ count = c;
+ }
+ }
+ return oldValue;
+ }
+
+ final void removeStale() {
+ KeyReference ref;
+ while ((ref = (KeyReference) refQueue.poll()) != null) {
+ remove(ref.keyRef(), ref.keyHash(), null, true);
+ }
+ }
+
+ void clear() {
+ if (count != 0) {
+ lock();
+ try {
+ HashEntry<K, V>[] tab = table;
+ for (int i = 0; i < tab.length; i++) {
+ tab[i] = null;
+ }
+ ++modCount;
+ // replace the reference queue to avoid unnecessary stale
cleanups
+ refQueue = new ReferenceQueue<Object>();
+ // write-volatile
+ count = 0;
+ } finally {
+ unlock();
+ }
+ }
+ }
+ }
+
+ /* ---------------- Public operations -------------- */
+
+ /**
+ * Creates a new, empty map with the specified initial
+ * capacity, reference types, load factor, and concurrency level.
+ * <p>
+ * Behavioral changing options such as {@link Option#IDENTITY_COMPARISONS}
+ * can also be specified.
+ *
+ * @param initialCapacity the initial capacity. The implementation
+ * performs internal sizing to accommodate this
many elements.
+ * @param loadFactor the load factor threshold, used to control
resizing.
+ * Resizing may be performed when the average
number of elements per
+ * bin exceeds this threshold.
+ * @param concurrencyLevel the estimated number of concurrently
+ * updating threads. The implementation performs
internal sizing
+ * to try to accommodate this many threads.
+ * @param keyType the reference type to use for keys
+ * @param valueType the reference type to use for values
+ * @param options the behavioral options
+ * @throws IllegalArgumentException if the initial capacity is
+ * negative or the load factor or
concurrencyLevel are
+ * nonpositive.
+ */
+ public ConcurrentReferenceHashMap(int initialCapacity,
+ float loadFactor, int concurrencyLevel,
+ ReferenceType keyType, ReferenceType
valueType,
+ EnumSet<Option> options) {
+ if (!(loadFactor > 0) || initialCapacity < 0 || concurrencyLevel <= 0)
{
+ throw new IllegalArgumentException();
+ }
+ if (concurrencyLevel > MAX_SEGMENTS) {
+ concurrencyLevel = MAX_SEGMENTS;
+ }
+ // Find power-of-two sizes best matching arguments
+ int sshift = 0;
+ int ssize = 1;
+ while (ssize < concurrencyLevel) {
+ ++sshift;
+ ssize <<= 1;
+ }
+ segmentShift = 32 - sshift;
+ segmentMask = ssize - 1;
+ this.segments = Segment.newArray(ssize);
+ if (initialCapacity > MAXIMUM_CAPACITY) {
+ initialCapacity = MAXIMUM_CAPACITY;
+ }
+ int c = initialCapacity / ssize;
+ if (c * ssize < initialCapacity) {
+ ++c;
+ }
+ int cap = 1;
+ while (cap < c) {
+ cap <<= 1;
+ }
+ identityComparisons = options != null &&
options.contains(Option.IDENTITY_COMPARISONS);
+ for (int i = 0; i < this.segments.length; ++i) {
+ this.segments[i] = new Segment<K, V>(cap, loadFactor, keyType,
valueType, identityComparisons);
+ }
+ }
+
+ /**
+ * Creates a new, empty map with the specified initial
+ * capacity, load factor, and concurrency level.
+ *
+ * @param initialCapacity the initial capacity. The implementation
+ * performs internal sizing to accommodate this
number of elements.
+ * @param loadFactor the load factor threshold, used to control
resizing.
+ * Resizing may be performed when the average
number of elements per
+ * bin exceeds this threshold.
+ * @param concurrencyLevel the estimated number of concurrently
+ * updating threads. The implementation performs
internal sizing
+ * to try to accommodate this many threads.
+ * @throws IllegalArgumentException if the initial capacity is
+ * negative or the load factor or
concurrencyLevel are
+ * nonpositive.
+ */
+ public ConcurrentReferenceHashMap(int initialCapacity, float loadFactor,
int concurrencyLevel) {
+ this(initialCapacity, loadFactor, concurrencyLevel, DEFAULT_KEY_TYPE,
DEFAULT_VALUE_TYPE, null);
+ }
+
+ /**
+ * Creates a new, empty map with the specified initial capacity
+ * and load factor and with the default reference types (weak keys,
+ * strong values), and concurrencyLevel (16).
+ *
+ * @param initialCapacity The implementation performs internal
+ * sizing to accommodate this number of elements.
+ * @param loadFactor the load factor threshold, used to control
resizing.
+ * Resizing may be performed when the average
number of elements per
+ * bin exceeds this threshold.
+ * @throws IllegalArgumentException if the initial capacity of
+ * elements is negative or the load
factor is nonpositive
+ * @since 1.6
+ */
+ public ConcurrentReferenceHashMap(int initialCapacity, float loadFactor) {
+ this(initialCapacity, loadFactor, DEFAULT_CONCURRENCY_LEVEL);
+ }
+
+
+ /**
+ * Creates a new, empty map with the specified initial capacity,
+ * reference types, and with a default load factor (0.75) and
concurrencyLevel (16).
+ *
+ * @param initialCapacity the initial capacity. The implementation
+ * performs internal sizing to accommodate this
many elements.
+ * @param keyType the reference type to use for keys
+ * @param valueType the reference type to use for values
+ * @throws IllegalArgumentException if the initial capacity of
+ * elements is negative.
+ */
+ public ConcurrentReferenceHashMap(int initialCapacity,
+ ReferenceType keyType, ReferenceType
valueType) {
+ this(initialCapacity, DEFAULT_LOAD_FACTOR, DEFAULT_CONCURRENCY_LEVEL,
+ keyType, valueType, null);
+ }
+
+ /**
+ * Creates a new, empty reference map with the specified key
+ * and value reference types.
+ *
+ * @param keyType the reference type to use for keys
+ * @param valueType the reference type to use for values
+ * @throws IllegalArgumentException if the initial capacity of
+ * elements is negative.
+ */
+ public ConcurrentReferenceHashMap(ReferenceType keyType, ReferenceType
valueType) {
+ this(DEFAULT_INITIAL_CAPACITY, DEFAULT_LOAD_FACTOR,
DEFAULT_CONCURRENCY_LEVEL,
+ keyType, valueType, null);
+ }
+
+ /**
+ * Creates a new, empty reference map with the specified reference types
+ * and behavioral options.
+ *
+ * @param keyType the reference type to use for keys
+ * @param valueType the reference type to use for values
+ * @throws IllegalArgumentException if the initial capacity of
+ * elements is negative.
+ */
+ public ConcurrentReferenceHashMap(ReferenceType keyType, ReferenceType
valueType, EnumSet<Option> options) {
+ this(DEFAULT_INITIAL_CAPACITY, DEFAULT_LOAD_FACTOR,
DEFAULT_CONCURRENCY_LEVEL,
+ keyType, valueType, options);
+ }
+
+
+ /**
+ * Creates a new, empty map with the specified initial capacity,
+ * and with default reference types (weak keys, strong values),
+ * load factor (0.75) and concurrencyLevel (16).
+ *
+ * @param initialCapacity the initial capacity. The implementation
+ * performs internal sizing to accommodate this
many elements.
+ * @throws IllegalArgumentException if the initial capacity of
+ * elements is negative.
+ */
+ public ConcurrentReferenceHashMap(int initialCapacity) {
+ this(initialCapacity, DEFAULT_LOAD_FACTOR, DEFAULT_CONCURRENCY_LEVEL);
+ }
+
+ /**
+ * Creates a new, empty map with a default initial capacity (16),
+ * reference types (weak keys, strong values), default
+ * load factor (0.75) and concurrencyLevel (16).
+ */
+ public ConcurrentReferenceHashMap() {
+ this(DEFAULT_INITIAL_CAPACITY, DEFAULT_LOAD_FACTOR,
DEFAULT_CONCURRENCY_LEVEL);
+ }
+
+ /**
+ * Creates a new map with the same mappings as the given map.
+ * The map is created with a capacity of 1.5 times the number
+ * of mappings in the given map or 16 (whichever is greater),
+ * and a default load factor (0.75) and concurrencyLevel (16).
+ *
+ * @param m the map
+ */
+ public ConcurrentReferenceHashMap(Map<? extends K, ? extends V> m) {
+ this(Math.max((int) (m.size() / DEFAULT_LOAD_FACTOR) + 1,
+ DEFAULT_INITIAL_CAPACITY),
+ DEFAULT_LOAD_FACTOR, DEFAULT_CONCURRENCY_LEVEL
+ );
+ putAll(m);
+ }
+
+ /**
+ * Returns <tt>true</tt> if this map contains no key-value mappings.
+ *
+ * @return <tt>true</tt> if this map contains no key-value mappings
+ */
+ public boolean isEmpty() {
+ final Segment<K, V>[] segments = this.segments;
+ /*
+ * We keep track of per-segment modCounts to avoid ABA
+ * problems in which an element in one segment was added and
+ * in another removed during traversal, in which case the
+ * table was never actually empty at any point. Note the
+ * similar use of modCounts in the size() and containsValue()
+ * methods, which are the only other methods also susceptible
+ * to ABA problems.
+ */
+ int[] mc = new int[segments.length];
+ int mcsum = 0;
+ for (int i = 0; i < segments.length; ++i) {
+ if (segments[i].count != 0) {
+ return false;
+ } else {
+ mcsum += mc[i] = segments[i].modCount;
+ }
+ }
+ // If mcsum happens to be zero, then we know we got a snapshot
+ // before any modifications at all were made. This is
+ // probably common enough to bother tracking.
+ if (mcsum != 0) {
+ for (int i = 0; i < segments.length; ++i) {
+ if (segments[i].count != 0 || mc[i] != segments[i].modCount) {
+ return false;
+ }
+ }
+ }
+ return true;
+ }
+
+ /**
+ * Returns the number of key-value mappings in this map. If the
+ * map contains more than <tt>Integer.MAX_VALUE</tt> elements, returns
+ * <tt>Integer.MAX_VALUE</tt>.
+ *
+ * @return the number of key-value mappings in this map
+ */
+ public int size() {
+ final Segment<K, V>[] segments = this.segments;
+ long sum = 0;
+ long check = 0;
+ int[] mc = new int[segments.length];
+ // Try a few times to get accurate count. On failure due to
+ // continuous async changes in table, resort to locking.
+ for (int k = 0; k < RETRIES_BEFORE_LOCK; ++k) {
+ check = 0;
+ sum = 0;
+ int mcsum = 0;
+ for (int i = 0; i < segments.length; ++i) {
+ sum += segments[i].count;
+ mcsum += mc[i] = segments[i].modCount;
+ }
+ if (mcsum != 0) {
+ for (int i = 0; i < segments.length; ++i) {
+ check += segments[i].count;
+ if (mc[i] != segments[i].modCount) {
+ // force retry
+ check = -1;
+ break;
+ }
+ }
+ }
+ if (check == sum) {
+ break;
+ }
+ }
+ if (check != sum) {
+ // Resort to locking all segments
+ sum = 0;
+ for (int i = 0; i < segments.length; ++i) {
+ segments[i].lock();
+ }
+ for (int i = 0; i < segments.length; ++i) {
+ sum += segments[i].count;
+ }
+ for (int i = 0; i < segments.length; ++i) {
+ segments[i].unlock();
+ }
+ }
+ return sum > Integer.MAX_VALUE ? Integer.MAX_VALUE : (int) sum;
+ }
+
+ /**
+ * Returns the value to which the specified key is mapped,
+ * or {@code null} if this map contains no mapping for the key.
+ * <p>
+ * <p>If this map contains a mapping from a key
+ * {@code k} to a value {@code v} such that {@code key.equals(k)},
+ * then this method returns {@code v}; otherwise it returns
+ * {@code null}. (There can be at most one such mapping.)
+ *
+ * @throws NullPointerException if the specified key is null
+ */
+ public V get(Object key) {
+ int hash = hashOf(key);
+ return segmentFor(hash).get(key, hash);
+ }
+
+ /**
+ * Tests if the specified object is a key in this table.
+ *
+ * @param key possible key
+ * @return <tt>true</tt> if and only if the specified object
+ * is a key in this table, as determined by the
+ * <tt>equals</tt> method; <tt>false</tt> otherwise.
+ * @throws NullPointerException if the specified key is null
+ */
+ public boolean containsKey(Object key) {
+ int hash = hashOf(key);
+ return segmentFor(hash).containsKey(key, hash);
+ }
+
+ /**
+ * Returns <tt>true</tt> if this map maps one or more keys to the
+ * specified value. Note: This method requires a full internal
+ * traversal of the hash table, therefore it is much slower than the
+ * method <tt>containsKey</tt>.
+ *
+ * @param value value whose presence in this map is to be tested
+ * @return <tt>true</tt> if this map maps one or more keys to the
+ * specified value
+ * @throws NullPointerException if the specified value is null
+ */
+ public boolean containsValue(Object value) {
+ if (value == null) {
+ throw new NullPointerException();
+ }
+ // See explanation of modCount use above
+ final Segment<K, V>[] segments = this.segments;
+ int[] mc = new int[segments.length];
+ // Try a few times without locking
+ for (int k = 0; k < RETRIES_BEFORE_LOCK; ++k) {
+ int sum = 0;
+ int mcsum = 0;
+ for (int i = 0; i < segments.length; ++i) {
+ int c = segments[i].count;
+ mcsum += mc[i] = segments[i].modCount;
+ if (segments[i].containsValue(value)) {
+ return true;
+ }
+ }
+ boolean cleanSweep = true;
+ if (mcsum != 0) {
+ for (int i = 0; i < segments.length; ++i) {
+ int c = segments[i].count;
+ if (mc[i] != segments[i].modCount) {
+ cleanSweep = false;
+ break;
+ }
+ }
+ }
+ if (cleanSweep) {
+ return false;
+ }
+ }
+ // Resort to locking all segments
+ for (int i = 0; i < segments.length; ++i) {
+ segments[i].lock();
+ }
+ boolean found = false;
+ try {
+ for (int i = 0; i < segments.length; ++i) {
+ if (segments[i].containsValue(value)) {
+ found = true;
+ break;
+ }
+ }
+ } finally {
+ for (int i = 0; i < segments.length; ++i) {
+ segments[i].unlock();
+ }
+ }
+ return found;
+ }
+
+ /**
+ * Legacy method testing if some key maps into the specified value
+ * in this table. This method is identical in functionality to
+ * {@link #containsValue}, and exists solely to ensure
+ * full compatibility with class {@link Hashtable},
+ * which supported this method prior to introduction of the
+ * Java Collections framework.
+ *
+ * @param value a value to search for
+ * @return <tt>true</tt> if and only if some key maps to the
+ * <tt>value</tt> argument in this table as
+ * determined by the <tt>equals</tt> method;
+ * <tt>false</tt> otherwise
+ * @throws NullPointerException if the specified value is null
+ */
+ public boolean contains(Object value) {
+ return containsValue(value);
+ }
+
+ /**
+ * Maps the specified key to the specified value in this table.
+ * Neither the key nor the value can be null.
+ * <p>
+ * <p> The value can be retrieved by calling the <tt>get</tt> method
+ * with a key that is equal to the original key.
+ *
+ * @param key key with which the specified value is to be associated
+ * @param value value to be associated with the specified key
+ * @return the previous value associated with <tt>key</tt>, or
+ * <tt>null</tt> if there was no mapping for <tt>key</tt>
+ * @throws NullPointerException if the specified key or value is null
+ */
+ public V put(K key, V value) {
+ if (value == null) {
+ throw new NullPointerException();
+ }
+ int hash = hashOf(key);
+ return segmentFor(hash).put(key, hash, value, null, false);
+ }
+
+ /**
+ * {@inheritDoc}
+ *
+ * @return the previous value associated with the specified key,
+ * or <tt>null</tt> if there was no mapping for the key
+ * @throws NullPointerException if the specified key or value is null
+ */
+ public V putIfAbsent(K key, V value) {
+ if (value == null) {
+ throw new NullPointerException();
+ }
+ int hash = hashOf(key);
+ return segmentFor(hash).put(key, hash, value, null, true);
+ }
+
+ /***
+ * {@inheritDoc}
+ *
+ * @throws UnsupportedOperationException {@inheritDoc}
+ * @throws ClassCastException {@inheritDoc}
+ * @throws NullPointerException {@inheritDoc}
+ * @implSpec The default implementation is equivalent to the following
steps for this
+ * {@code map}, then returning the current value or {@code null} if now
+ * absent:
+ * <p>
+ * <pre> {@code
+ * if (map.get(key) == null) {
+ * V newValue = mappingFunction.apply(key);
+ * if (newValue != null)
+ * return map.putIfAbsent(key, newValue);
+ * }
+ * }</pre>
+ * <p>
+ * The default implementation may retry these steps when multiple
+ * threads attempt updates including potentially calling the mapping
+ * function multiple times.
+ * <p>
+ * <p>This implementation assumes that the ConcurrentMap cannot contain
null
+ * values and {@code get()} returning null unambiguously means the key is
+ * absent. Implementations which support null values <strong>must</strong>
+ * override this default implementation.
+ */
+ @Override
+ public V applyIfAbsent(K key, Function<? super K, ? extends V>
mappingFunction) {
+ checkNotNull(key);
+ checkNotNull(mappingFunction);
+
+ int hash = hashOf(key);
+ Segment<K, V> segment = segmentFor(hash);
+ V v = segment.get(key, hash);
+ return v == null ? segment.put(key, hash, null, mappingFunction, true)
: v;
+ }
+
+ @Override
+ public V applyIfPresent(K key, BiFunction<? super K, ? super V, ? extends
V> remappingFunction) {
+ checkNotNull(key);
+ checkNotNull(remappingFunction);
+
+ int hash = hashOf(key);
+ Segment<K, V> segment = segmentFor(hash);
+ V v = segment.get(key, hash);
+ if (v == null) {
+ return null;
+ }
+
+ return segmentFor(hash).applyIfPresent(key, hash, remappingFunction);
+ }
+
+ @Override
+ public V apply(K key, BiFunction<? super K, ? super V, ? extends V>
remappingFunction) {
+ checkNotNull(key);
+ checkNotNull(remappingFunction);
+
+ int hash = hashOf(key);
+ Segment<K, V> segment = segmentFor(hash);
+ return segment.apply(key, hash, remappingFunction);
+ }
+
+ /**
+ * Copies all of the mappings from the specified map to this one.
+ * These mappings replace any mappings that this map had for any of the
+ * keys currently in the specified map.
+ *
+ * @param m mappings to be stored in this map
+ */
+ public void putAll(Map<? extends K, ? extends V> m) {
+ for (Entry<? extends K, ? extends V> e : m.entrySet()) {
+ put(e.getKey(), e.getValue());
+ }
+ }
+
+ /**
+ * Removes the key (and its corresponding value) from this map.
+ * This method does nothing if the key is not in the map.
+ *
+ * @param key the key that needs to be removed
+ * @return the previous value associated with <tt>key</tt>, or
+ * <tt>null</tt> if there was no mapping for <tt>key</tt>
+ * @throws NullPointerException if the specified key is null
+ */
+ public V remove(Object key) {
+ int hash = hashOf(key);
+ return segmentFor(hash).remove(key, hash, null, false);
+ }
+
+ /**
+ * {@inheritDoc}
+ *
+ * @throws NullPointerException if the specified key is null
+ */
+ public boolean remove(Object key, Object value) {
+ int hash = hashOf(key);
+ if (value == null) {
+ return false;
+ }
+ return segmentFor(hash).remove(key, hash, value, false) != null;
+ }
+
+ /**
+ * {@inheritDoc}
+ *
+ * @throws NullPointerException if any of the arguments are null
+ */
+ public boolean replace(K key, V oldValue, V newValue) {
+ if (oldValue == null || newValue == null) {
+ throw new NullPointerException();
+ }
+ int hash = hashOf(key);
+ return segmentFor(hash).replace(key, hash, oldValue, newValue);
+ }
+
+ /**
+ * {@inheritDoc}
+ *
+ * @return the previous value associated with the specified key,
+ * or <tt>null</tt> if there was no mapping for the key
+ * @throws NullPointerException if the specified key or value is null
+ */
+ public V replace(K key, V value) {
+ if (value == null) {
+ throw new NullPointerException();
+ }
+ int hash = hashOf(key);
+ return segmentFor(hash).replace(key, hash, value);
+ }
+
+ /**
+ * Removes all of the mappings from this map.
+ */
+ public void clear() {
+ for (int i = 0; i < segments.length; ++i) {
+ segments[i].clear();
+ }
+ }
+
+ /**
+ * Removes any stale entries whose keys have been finalized. Use of this
+ * method is normally not necessary since stale entries are automatically
+ * removed lazily, when blocking operations are required. However, there
+ * are some cases where this operation should be performed eagerly, such
+ * as cleaning up old references to a ClassLoader in a multi-classloader
+ * environment.
+ * <p>
+ * Note: this method will acquire locks one at a time across all segments
+ * of this table, so this method should be used sparingly.
+ */
+ public void purgeStaleEntries() {
+ for (int i = 0; i < segments.length; ++i) {
+ segments[i].removeStale();
+ }
+ }
+
+
+ /**
+ * Returns a {@link Set} view of the keys contained in this map.
+ * The set is backed by the map, so changes to the map are
+ * reflected in the set, and vice-versa. The set supports element
+ * removal, which removes the corresponding mapping from this map,
+ * via the <tt>Iterator.remove</tt>, <tt>Set.remove</tt>,
+ * <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt>
+ * operations. It does not support the <tt>add</tt> or
+ * <tt>addAll</tt> operations.
+ * <p>
+ * <p>The view's <tt>iterator</tt> is a "weakly consistent" iterator
+ * that will never throw {@link ConcurrentModificationException},
+ * and guarantees to traverse elements as they existed upon
+ * construction of the iterator, and may (but is not guaranteed to)
+ * reflect any modifications subsequent to construction.
+ */
+ public Set<K> keySet() {
+ Set<K> ks = keySet;
+ return (ks != null) ? ks : (keySet = new KeySet());
+ }
+
+ /**
+ * Returns a {@link Collection} view of the values contained in this map.
+ * The collection is backed by the map, so changes to the map are
+ * reflected in the collection, and vice-versa. The collection
+ * supports element removal, which removes the corresponding
+ * mapping from this map, via the <tt>Iterator.remove</tt>,
+ * <tt>Collection.remove</tt>, <tt>removeAll</tt>,
+ * <tt>retainAll</tt>, and <tt>clear</tt> operations. It does not
+ * support the <tt>add</tt> or <tt>addAll</tt> operations.
+ * <p>
+ * <p>The view's <tt>iterator</tt> is a "weakly consistent" iterator
+ * that will never throw {@link ConcurrentModificationException},
+ * and guarantees to traverse elements as they existed upon
+ * construction of the iterator, and may (but is not guaranteed to)
+ * reflect any modifications subsequent to construction.
+ */
+ public Collection<V> values() {
+ Collection<V> vs = values;
+ return (vs != null) ? vs : (values = new Values());
+ }
+
+ /**
+ * Returns a {@link Set} view of the mappings contained in this map.
+ * The set is backed by the map, so changes to the map are
+ * reflected in the set, and vice-versa. The set supports element
+ * removal, which removes the corresponding mapping from the map,
+ * via the <tt>Iterator.remove</tt>, <tt>Set.remove</tt>,
+ * <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt>
+ * operations. It does not support the <tt>add</tt> or
+ * <tt>addAll</tt> operations.
+ * <p>
+ * <p>The view's <tt>iterator</tt> is a "weakly consistent" iterator
+ * that will never throw {@link ConcurrentModificationException},
+ * and is guaranteed to traverse elements as they existed upon
+ * construction of the iterator, and may (but is not guaranteed to)
+ * reflect any modifications subsequent to construction.
+ */
+ public Set<Entry<K, V>> entrySet() {
+ Set<Entry<K, V>> es = entrySet;
+ return (es != null) ? es : (entrySet = new EntrySet(false));
+ }
+
+ public Set<Entry<K, V>> cachedEntrySet() {
+ Set<Entry<K, V>> es = entrySet;
+ return (es != null) ? es : (entrySet = new EntrySet(true));
+ }
+
+ /**
+ * Returns an enumeration of the keys in this table.
+ *
+ * @return an enumeration of the keys in this table
+ * @see #keySet()
+ */
+ public Enumeration<K> keys() {
+ return new KeyIterator();
+ }
+
+ /**
+ * Returns an enumeration of the values in this table.
+ *
+ * @return an enumeration of the values in this table
+ * @see #values()
+ */
+ public Enumeration<V> elements() {
+ return new ValueIterator();
+ }
+
+ /* ---------------- Iterator Support -------------- */
+
+ protected abstract class HashIterator {
+ int nextSegmentIndex;
+ int nextTableIndex;
+ HashEntry<K, V>[] currentTable;
+ HashEntry<K, V> nextEntry;
+ HashEntry<K, V> lastReturned;
+ // Strong reference to weak key (prevents gc)
+ K currentKey;
+
+ HashIterator() {
+ nextSegmentIndex = segments.length - 1;
+ nextTableIndex = -1;
+ advance();
+ }
+
+ public boolean hasMoreElements() {
+ return hasNext();
+ }
+
+ final void advance() {
+ if (nextEntry != null && (nextEntry = nextEntry.next) != null) {
+ return;
+ }
+ while (nextTableIndex >= 0) {
+ if ((nextEntry = currentTable[nextTableIndex--]) != null) {
+ return;
+ }
+ }
+ while (nextSegmentIndex >= 0) {
+ Segment<K, V> seg = segments[nextSegmentIndex--];
+ if (seg.count != 0) {
+ currentTable = seg.table;
+ for (int j = currentTable.length - 1; j >= 0; --j) {
+ if ((nextEntry = currentTable[j]) != null) {
+ nextTableIndex = j - 1;
+ return;
+ }
+ }
+ }
+ }
+ }
+
+ public boolean hasNext() {
+ while (nextEntry != null) {
+ if (nextEntry.key() != null) {
+ return true;
+ }
+ advance();
+ }
+ return false;
+ }
+
+ HashEntry<K, V> nextEntry() {
+ do {
+ if (nextEntry == null) {
+ throw new NoSuchElementException();
+ }
+ lastReturned = nextEntry;
+ currentKey = lastReturned.key();
+ advance();
+ } while /* Skip GC'd keys */ (currentKey == null);
+ return lastReturned;
+ }
+
+ public void remove() {
+ if (lastReturned == null) {
+ throw new IllegalStateException();
+ }
+ ConcurrentReferenceHashMap.this.remove(currentKey);
+ lastReturned = null;
+ }
+ }
+
+ final class KeyIterator extends HashIterator implements Iterator<K>,
Enumeration<K> {
+ public K next() {
+ return super.nextEntry().key();
+ }
+
+ public K nextElement() {
+ return super.nextEntry().key();
+ }
+ }
+
+ final class ValueIterator extends HashIterator implements Iterator<V>,
Enumeration<V> {
+ public V next() {
+ return super.nextEntry().value();
+ }
+
+ public V nextElement() {
+ return super.nextEntry().value();
+ }
+ }
+
+ /*
+ * This class is needed for JDK5 compatibility.
+ */
+ @SerializableByConvention
+ protected static class SimpleEntry<K, V> implements Entry<K, V>,
Serializable {
+ private static final long serialVersionUID = -8499721149061103585L;
+
+ protected final K key;
+ protected V value;
+
+ public SimpleEntry(K key, V value) {
+ this.key = key;
+ this.value = value;
+ }
+
+ public SimpleEntry(Entry<? extends K, ? extends V> entry) {
+ this.key = entry.getKey();
+ this.value = entry.getValue();
+ }
+
+ public K getKey() {
+ return key;
+ }
+
+ public V getValue() {
+ return value;
+ }
+
+ public V setValue(V value) {
+ V oldValue = this.value;
+ this.value = value;
+ return oldValue;
+ }
+
+ public boolean equals(Object o) {
+ if (!(o instanceof Map.Entry)) {
+ return false;
+ }
+ @SuppressWarnings("unchecked")
+ Entry e = (Entry) o;
+ return eq(key, e.getKey()) && eq(value, e.getValue());
+ }
+
+ public int hashCode() {
+ return (key == null ? 0 : key.hashCode()) ^ (value == null ? 0 :
value.hashCode());
+ }
+
+ public String toString() {
+ return key + "=" + value;
+ }
+
+ private static boolean eq(Object o1, Object o2) {
+ return o1 == null ? o2 == null : o1.equals(o2);
+ }
+ }
+
+
+ /**
+ * Custom Entry class used by EntryIterator.next(), that relays setValue
+ * changes to the underlying map.
+ */
+ @SerializableByConvention
+ protected class WriteThroughEntry extends SimpleEntry<K, V> {
+ private static final long serialVersionUID = -7900634345345313646L;
+
+ protected WriteThroughEntry(K k, V v) {
+ super(k, v);
+ }
+
+ /**
+ * Set our entry's value and writes it through to the map. The
+ * value to return is somewhat arbitrary: since a
+ * WriteThroughEntry does not necessarily track asynchronous
+ * changes, the most recent "previous" value could be
+ * different from what we return (or could even have been
+ * removed in which case the put will re-establish). We do not
+ * and cannot guarantee more.
+ */
+ public V setValue(V value) {
+ if (value == null) {
+ throw new NullPointerException();
+ }
+ V v = super.setValue(value);
+ ConcurrentReferenceHashMap.this.put(getKey(), value);
+ return v;
+ }
+ }
+
+ final class EntryIterator extends HashIterator implements
Iterator<Entry<K, V>> {
+ public Entry<K, V> next() {
+ HashEntry<K, V> e = super.nextEntry();
+ return new WriteThroughEntry(e.key(), e.value());
+ }
+ }
+
+ final class CachedEntryIterator extends HashIterator implements
Iterator<Entry<K, V>> {
+ private InitializableEntry entry = new InitializableEntry();
+
+ public Entry<K, V> next() {
+ HashEntry<K, V> e = super.nextEntry();
+ return entry.init(e.key(), e.value());
+ }
+ }
+
+ protected static class InitializableEntry<K, V> implements Entry<K, V> {
+ private K key;
+ private V value;
+
+ @Override
+ public K getKey() {
+ return key;
+ }
+
+ @Override
+ public V getValue() {
+ return value;
+ }
+
+ public Entry<K, V> init(K key, V value) {
+ this.key = key;
+ this.value = value;
+ return this;
+ }
+
+ @Override
+ public V setValue(V value) {
+ throw new UnsupportedOperationException();
+ }
+ }
+
+ final class KeySet extends AbstractSet<K> {
+ public Iterator<K> iterator() {
+ return new KeyIterator();
+ }
+
+ public int size() {
+ return ConcurrentReferenceHashMap.this.size();
+ }
+
+ public boolean isEmpty() {
+ return ConcurrentReferenceHashMap.this.isEmpty();
+ }
+
+ public boolean contains(Object o) {
+ return ConcurrentReferenceHashMap.this.containsKey(o);
+ }
+
+ public boolean remove(Object o) {
+ return ConcurrentReferenceHashMap.this.remove(o) != null;
+ }
+
+ public void clear() {
+ ConcurrentReferenceHashMap.this.clear();
+ }
+ }
+
+ final class Values extends AbstractCollection<V> {
+ public Iterator<V> iterator() {
+ return new ValueIterator();
+ }
+
+ public int size() {
+ return ConcurrentReferenceHashMap.this.size();
+ }
+
+ public boolean isEmpty() {
+ return ConcurrentReferenceHashMap.this.isEmpty();
+ }
+
+ public boolean contains(Object o) {
+ return ConcurrentReferenceHashMap.this.containsValue(o);
+ }
+
+ public void clear() {
+ ConcurrentReferenceHashMap.this.clear();
+ }
+ }
+
+ final class EntrySet extends AbstractSet<Entry<K, V>> {
+ private final boolean cached;
+
+ public EntrySet(boolean cached) {
+ this.cached = cached;
+ }
+
+ public Iterator<Entry<K, V>> iterator() {
+ return cached ? new CachedEntryIterator() : new EntryIterator();
+ }
+
+ public boolean contains(Object o) {
+ if (!(o instanceof Map.Entry)) {
+ return false;
+ }
+ Entry<?, ?> e = (Entry<?, ?>) o;
+ V v = ConcurrentReferenceHashMap.this.get(e.getKey());
+ return v != null && v.equals(e.getValue());
+ }
+
+ public boolean remove(Object o) {
+ if (!(o instanceof Map.Entry)) {
+ return false;
+ }
+ Entry<?, ?> e = (Entry<?, ?>) o;
+ return ConcurrentReferenceHashMap.this.remove(e.getKey(),
e.getValue());
+ }
+
+ public int size() {
+ return ConcurrentReferenceHashMap.this.size();
+ }
+
+ public boolean isEmpty() {
+ return ConcurrentReferenceHashMap.this.isEmpty();
+ }
+
+ public void clear() {
+ ConcurrentReferenceHashMap.this.clear();
+ }
+ }
+
+ /* ---------------- Serialization Support -------------- */
+
+ /**
+ * Save the state of the <tt>ConcurrentReferenceHashMap</tt> instance to a
+ * stream (i.e., serialize it).
+ *
+ * @param s the stream
+ * @serialData the key (Object) and value (Object)
+ * for each key-value mapping, followed by a null pair.
+ * The key-value mappings are emitted in no particular order.
+ */
+ private void writeObject(java.io.ObjectOutputStream s) throws IOException {
+ s.defaultWriteObject();
+
+ for (int k = 0; k < segments.length; ++k) {
+ Segment<K, V> seg = segments[k];
+ seg.lock();
+ try {
+ HashEntry<K, V>[] tab = seg.table;
+ for (int i = 0; i < tab.length; ++i) {
+ for (HashEntry<K, V> e = tab[i]; e != null; e = e.next) {
+ K key = e.key();
+ // Skip GC'd keys
+ if (key == null) {
+ continue;
+ }
+ s.writeObject(key);
+ s.writeObject(e.value());
+ }
+ }
+ } finally {
+ seg.unlock();
+ }
+ }
+ s.writeObject(null);
+ s.writeObject(null);
+ }
+
+ /**
+ * Reconstitute the <tt>ConcurrentReferenceHashMap</tt> instance from a
+ * stream (i.e., deserialize it).
+ *
+ * @param s the stream
+ */
+ @SuppressWarnings("unchecked")
+ private void readObject(java.io.ObjectInputStream s) throws IOException,
ClassNotFoundException {
+ s.defaultReadObject();
+
+ // Initialize each segment to be minimally sized, and let grow.
+ for (int i = 0; i < segments.length; ++i) {
+ segments[i].setTable(new HashEntry[1]);
+ }
+
+ // Read the keys and values, and put the mappings in the table
+ while (true) {
+ K key = (K) s.readObject();
+ V value = (V) s.readObject();
+ if (key == null) {
+ break;
+ }
+ put(key, value);
+ }
+ }
+}
