Author: tv
Date: Fri Dec 23 21:44:44 2016
New Revision: 1775910
URL: http://svn.apache.org/viewvc?rev=1775910&view=rev
Log:
Add Ben Manes' ConcurrentLinkedHashMap
Added:
commons/proper/jcs/branches/jcs-core-with-clhm/commons-jcs-core/src/main/java/org/apache/commons/jcs/utils/clhm/
commons/proper/jcs/branches/jcs-core-with-clhm/commons-jcs-core/src/main/java/org/apache/commons/jcs/utils/clhm/ConcurrentLinkedHashMap.java
(with props)
commons/proper/jcs/branches/jcs-core-with-clhm/commons-jcs-core/src/main/java/org/apache/commons/jcs/utils/clhm/EntryWeigher.java
(with props)
commons/proper/jcs/branches/jcs-core-with-clhm/commons-jcs-core/src/main/java/org/apache/commons/jcs/utils/clhm/EvictionListener.java
(with props)
commons/proper/jcs/branches/jcs-core-with-clhm/commons-jcs-core/src/main/java/org/apache/commons/jcs/utils/clhm/LinkedDeque.java
(with props)
commons/proper/jcs/branches/jcs-core-with-clhm/commons-jcs-core/src/main/java/org/apache/commons/jcs/utils/clhm/Weigher.java
(with props)
commons/proper/jcs/branches/jcs-core-with-clhm/commons-jcs-core/src/main/java/org/apache/commons/jcs/utils/clhm/Weighers.java
(with props)
commons/proper/jcs/branches/jcs-core-with-clhm/commons-jcs-core/src/main/java/org/apache/commons/jcs/utils/clhm/package-info.java
(with props)
commons/proper/jcs/branches/jcs-core-with-clhm/commons-jcs-core/src/main/java/org/apache/commons/jcs/utils/clhm/package.html
(with props)
Added:
commons/proper/jcs/branches/jcs-core-with-clhm/commons-jcs-core/src/main/java/org/apache/commons/jcs/utils/clhm/ConcurrentLinkedHashMap.java
URL:
http://svn.apache.org/viewvc/commons/proper/jcs/branches/jcs-core-with-clhm/commons-jcs-core/src/main/java/org/apache/commons/jcs/utils/clhm/ConcurrentLinkedHashMap.java?rev=1775910&view=auto
==============================================================================
---
commons/proper/jcs/branches/jcs-core-with-clhm/commons-jcs-core/src/main/java/org/apache/commons/jcs/utils/clhm/ConcurrentLinkedHashMap.java
(added)
+++
commons/proper/jcs/branches/jcs-core-with-clhm/commons-jcs-core/src/main/java/org/apache/commons/jcs/utils/clhm/ConcurrentLinkedHashMap.java
Fri Dec 23 21:44:44 2016
@@ -0,0 +1,1574 @@
+/*
+ * Copyright 2010 Google 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.apache.commons.jcs.utils.clhm;
+
+import static java.util.Collections.emptyList;
+import static java.util.Collections.unmodifiableMap;
+import static java.util.Collections.unmodifiableSet;
+import static
org.apache.commons.jcs.utils.clhm.ConcurrentLinkedHashMap.DrainStatus.IDLE;
+import static
org.apache.commons.jcs.utils.clhm.ConcurrentLinkedHashMap.DrainStatus.PROCESSING;
+import static
org.apache.commons.jcs.utils.clhm.ConcurrentLinkedHashMap.DrainStatus.REQUIRED;
+
+import java.io.InvalidObjectException;
+import java.io.ObjectInputStream;
+import java.io.Serializable;
+import java.util.AbstractCollection;
+import java.util.AbstractMap;
+import java.util.AbstractQueue;
+import java.util.AbstractSet;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.LinkedHashMap;
+import java.util.LinkedHashSet;
+import java.util.Map;
+import java.util.Queue;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentLinkedQueue;
+import java.util.concurrent.ConcurrentMap;
+import java.util.concurrent.atomic.AtomicLong;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
+
+/**
+ * A hash table supporting full concurrency of retrievals, adjustable expected
+ * concurrency for updates, and a maximum capacity to bound the map by. This
+ * implementation differs from {@link ConcurrentHashMap} in that it maintains a
+ * page replacement algorithm that is used to evict an entry when the map has
+ * exceeded its capacity. Unlike the <tt>Java Collections Framework</tt>, this
+ * map does not have a publicly visible constructor and instances are created
+ * through a {@link Builder}.
+ * <p>
+ * An entry is evicted from the map when the <tt>weighted capacity</tt> exceeds
+ * its <tt>maximum weighted capacity</tt> threshold. A {@link EntryWeigher}
+ * determines how many units of capacity that an entry consumes. The default
+ * weigher assigns each value a weight of <tt>1</tt> to bound the map by the
+ * total number of key-value pairs. A map that holds collections may choose to
+ * weigh values by the number of elements in the collection and bound the map
+ * by the total number of elements that it contains. A change to a value that
+ * modifies its weight requires that an update operation is performed on the
+ * map.
+ * <p>
+ * An {@link EvictionListener} may be supplied for notification when an entry
+ * is evicted from the map. This listener is invoked on a caller's thread and
+ * will not block other threads from operating on the map. An implementation
+ * should be aware that the caller's thread will not expect long execution
+ * times or failures as a side effect of the listener being notified. Execution
+ * safety and a fast turn around time can be achieved by performing the
+ * operation asynchronously, such as by submitting a task to an
+ * {@link java.util.concurrent.ExecutorService}.
+ * <p>
+ * The <tt>concurrency level</tt> determines the number of threads that can
+ * concurrently modify the table. Using a significantly higher or lower value
+ * than needed can waste space or lead to thread contention, but an estimate
+ * within an order of magnitude of the ideal value does not usually have a
+ * noticeable impact. Because placement in hash tables is essentially random,
+ * the actual concurrency will vary.
+ * <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>
+ * Like {@link java.util.Hashtable} but unlike {@link HashMap}, this class
+ * does <em>not</em> allow <tt>null</tt> to be used as a key or value. Unlike
+ * {@link java.util.LinkedHashMap}, this class does <em>not</em> provide
+ * predictable iteration order. A snapshot of the keys and entries may be
+ * obtained in ascending and descending order of retention.
+ *
+ * @author [email protected] (Ben Manes)
+ * @param <K> the type of keys maintained by this map
+ * @param <V> the type of mapped values
+ * @see <a href="http://code.google.com/p/concurrentlinkedhashmap/";>
+ * http://code.google.com/p/concurrentlinkedhashmap/</a>
+ */
+public final class ConcurrentLinkedHashMap<K, V> extends AbstractMap<K, V>
+ implements ConcurrentMap<K, V>, Serializable {
+
+ /*
+ * This class performs a best-effort bounding of a ConcurrentHashMap using a
+ * page-replacement algorithm to determine which entries to evict when the
+ * capacity is exceeded.
+ *
+ * The page replacement algorithm's data structures are kept eventually
+ * consistent with the map. An update to the map and recording of reads may
+ * not be immediately reflected on the algorithm's data structures. These
+ * structures are guarded by a lock and operations are applied in batches to
+ * avoid lock contention. The penalty of applying the batches is spread
across
+ * threads so that the amortized cost is slightly higher than performing just
+ * the ConcurrentHashMap operation.
+ *
+ * A memento of the reads and writes that were performed on the map are
+ * recorded in buffers. These buffers are drained at the first opportunity
+ * after a write or when the read buffer exceeds a threshold size. The reads
+ * are recorded in a lossy buffer, allowing the reordering operations to be
+ * discarded if the draining process cannot keep up. Due to the concurrent
+ * nature of the read and write operations a strict policy ordering is not
+ * possible, but is observably strict when single threaded.
+ *
+ * Due to a lack of a strict ordering guarantee, a task can be executed
+ * out-of-order, such as a removal followed by its addition. The state of the
+ * entry is encoded within the value's weight.
+ *
+ * Alive: The entry is in both the hash-table and the page replacement
policy.
+ * This is represented by a positive weight.
+ *
+ * Retired: The entry is not in the hash-table and is pending removal from
the
+ * page replacement policy. This is represented by a negative weight.
+ *
+ * Dead: The entry is not in the hash-table and is not in the page
replacement
+ * policy. This is represented by a weight of zero.
+ *
+ * The Least Recently Used page replacement algorithm was chosen due to its
+ * simplicity, high hit rate, and ability to be implemented with O(1) time
+ * complexity.
+ */
+
+ /** The number of CPUs */
+ static final int NCPU = Runtime.getRuntime().availableProcessors();
+
+ /** The maximum weighted capacity of the map. */
+ static final long MAXIMUM_CAPACITY = Long.MAX_VALUE - Integer.MAX_VALUE;
+
+ /** The number of read buffers to use. */
+ static final int NUMBER_OF_READ_BUFFERS = ceilingNextPowerOfTwo(NCPU);
+
+ /** Mask value for indexing into the read buffers. */
+ static final int READ_BUFFERS_MASK = NUMBER_OF_READ_BUFFERS - 1;
+
+ /** The number of pending read operations before attempting to drain. */
+ static final int READ_BUFFER_THRESHOLD = 32;
+
+ /** The maximum number of read operations to perform per amortized drain. */
+ static final int READ_BUFFER_DRAIN_THRESHOLD = 2 * READ_BUFFER_THRESHOLD;
+
+ /** The maximum number of pending reads per buffer. */
+ static final int READ_BUFFER_SIZE = 2 * READ_BUFFER_DRAIN_THRESHOLD;
+
+ /** Mask value for indexing into the read buffer. */
+ static final int READ_BUFFER_INDEX_MASK = READ_BUFFER_SIZE - 1;
+
+ /** The maximum number of write operations to perform per amortized drain. */
+ static final int WRITE_BUFFER_DRAIN_THRESHOLD = 16;
+
+ /** A queue that discards all entries. */
+ static final Queue<?> DISCARDING_QUEUE = new DiscardingQueue();
+
+ static int ceilingNextPowerOfTwo(int x) {
+ // From Hacker's Delight, Chapter 3, Harry S. Warren Jr.
+ return 1 << (Integer.SIZE - Integer.numberOfLeadingZeros(x - 1));
+ }
+
+ // The backing data store holding the key-value associations
+ final ConcurrentMap<K, Node<K, V>> data;
+ final int concurrencyLevel;
+
+ // These fields provide support to bound the map by a maximum capacity
+ final long[] readBufferReadCount;
+ final LinkedDeque<Node<K, V>> evictionDeque;
+
+ final AtomicLong weightedSize;
+ final AtomicLong capacity;
+
+ final Lock evictionLock;
+ final Queue<Runnable> writeBuffer;
+ final AtomicLong[] readBufferWriteCount;
+ final AtomicLong[] readBufferDrainAtWriteCount;
+ final AtomicReference<Node<K, V>>[][] readBuffers;
+
+ final AtomicReference<DrainStatus> drainStatus;
+ final EntryWeigher<? super K, ? super V> weigher;
+
+ // These fields provide support for notifying a listener.
+ final Queue<Node<K, V>> pendingNotifications;
+ final EvictionListener<K, V> listener;
+
+ transient Set<K> keySet;
+ transient Collection<V> values;
+ transient Set<Entry<K, V>> entrySet;
+
+ /**
+ * Creates an instance based on the builder's configuration.
+ */
+ @SuppressWarnings({"unchecked", "cast"})
+ private ConcurrentLinkedHashMap(Builder<K, V> builder) {
+ // The data store and its maximum capacity
+ concurrencyLevel = builder.concurrencyLevel;
+ capacity = new AtomicLong(Math.min(builder.capacity, MAXIMUM_CAPACITY));
+ data = new ConcurrentHashMap<K, Node<K, V>>(builder.initialCapacity,
0.75f, concurrencyLevel);
+
+ // The eviction support
+ weigher = builder.weigher;
+ evictionLock = new ReentrantLock();
+ weightedSize = new AtomicLong();
+ evictionDeque = new LinkedDeque<Node<K, V>>();
+ writeBuffer = new ConcurrentLinkedQueue<Runnable>();
+ drainStatus = new AtomicReference<DrainStatus>(IDLE);
+
+ readBufferReadCount = new long[NUMBER_OF_READ_BUFFERS];
+ readBufferWriteCount = new AtomicLong[NUMBER_OF_READ_BUFFERS];
+ readBufferDrainAtWriteCount = new AtomicLong[NUMBER_OF_READ_BUFFERS];
+ readBuffers = new
AtomicReference[NUMBER_OF_READ_BUFFERS][READ_BUFFER_SIZE];
+ for (int i = 0; i < NUMBER_OF_READ_BUFFERS; i++) {
+ readBufferWriteCount[i] = new AtomicLong();
+ readBufferDrainAtWriteCount[i] = new AtomicLong();
+ readBuffers[i] = new AtomicReference[READ_BUFFER_SIZE];
+ for (int j = 0; j < READ_BUFFER_SIZE; j++) {
+ readBuffers[i][j] = new AtomicReference<Node<K, V>>();
+ }
+ }
+
+ // The notification queue and listener
+ listener = builder.listener;
+ pendingNotifications = (listener == DiscardingListener.INSTANCE)
+ ? (Queue<Node<K, V>>) DISCARDING_QUEUE
+ : new ConcurrentLinkedQueue<Node<K, V>>();
+ }
+
+ /** Ensures that the object is not null. */
+ static void checkNotNull(Object o) {
+ if (o == null) {
+ throw new NullPointerException();
+ }
+ }
+
+ /** Ensures that the argument expression is true. */
+ static void checkArgument(boolean expression) {
+ if (!expression) {
+ throw new IllegalArgumentException();
+ }
+ }
+
+ /** Ensures that the state expression is true. */
+ static void checkState(boolean expression) {
+ if (!expression) {
+ throw new IllegalStateException();
+ }
+ }
+
+ /* ---------------- Eviction Support -------------- */
+
+ /**
+ * Retrieves the maximum weighted capacity of the map.
+ *
+ * @return the maximum weighted capacity
+ */
+ public long capacity() {
+ return capacity.get();
+ }
+
+ /**
+ * Sets the maximum weighted capacity of the map and eagerly evicts entries
+ * until it shrinks to the appropriate size.
+ *
+ * @param capacity the maximum weighted capacity of the map
+ * @throws IllegalArgumentException if the capacity is negative
+ */
+ public void setCapacity(long capacity) {
+ checkArgument(capacity >= 0);
+ evictionLock.lock();
+ try {
+ this.capacity.lazySet(Math.min(capacity, MAXIMUM_CAPACITY));
+ drainBuffers();
+ evict();
+ } finally {
+ evictionLock.unlock();
+ }
+ notifyListener();
+ }
+
+ /** Determines whether the map has exceeded its capacity. */
+ boolean hasOverflowed() {
+ return weightedSize.get() > capacity.get();
+ }
+
+ /**
+ * Evicts entries from the map while it exceeds the capacity and appends
+ * evicted entries to the notification queue for processing.
+ */
+ void evict() {
+ // Attempts to evict entries from the map if it exceeds the maximum
+ // capacity. If the eviction fails due to a concurrent removal of the
+ // victim, that removal may cancel out the addition that triggered this
+ // eviction. The victim is eagerly unlinked before the removal task so
+ // that if an eviction is still required then a new victim will be chosen
+ // for removal.
+ while (hasOverflowed()) {
+ final Node<K, V> node = evictionDeque.poll();
+
+ // If weighted values are used, then the pending operations will adjust
+ // the size to reflect the correct weight
+ if (node == null) {
+ return;
+ }
+
+ // Notify the listener only if the entry was evicted
+ if (data.remove(node.key, node)) {
+ pendingNotifications.add(node);
+ }
+
+ makeDead(node);
+ }
+ }
+
+ /**
+ * Performs the post-processing work required after a read.
+ *
+ * @param node the entry in the page replacement policy
+ */
+ void afterRead(Node<K, V> node) {
+ final int bufferIndex = readBufferIndex();
+ final long writeCount = recordRead(bufferIndex, node);
+ drainOnReadIfNeeded(bufferIndex, writeCount);
+ notifyListener();
+ }
+
+ /** Returns the index to the read buffer to record into. */
+ static int readBufferIndex() {
+ // A buffer is chosen by the thread's id so that tasks are distributed in a
+ // pseudo evenly manner. This helps avoid hot entries causing contention
+ // due to other threads trying to append to the same buffer.
+ return ((int) Thread.currentThread().getId()) & READ_BUFFERS_MASK;
+ }
+
+ /**
+ * Records a read in the buffer and return its write count.
+ *
+ * @param bufferIndex the index to the chosen read buffer
+ * @param node the entry in the page replacement policy
+ * @return the number of writes on the chosen read buffer
+ */
+ long recordRead(int bufferIndex, Node<K, V> node) {
+ // The location in the buffer is chosen in a racy fashion as the increment
+ // is not atomic with the insertion. This means that concurrent reads can
+ // overlap and overwrite one another, resulting in a lossy buffer.
+ final AtomicLong counter = readBufferWriteCount[bufferIndex];
+ final long writeCount = counter.get();
+ counter.lazySet(writeCount + 1);
+
+ final int index = (int) (writeCount & READ_BUFFER_INDEX_MASK);
+ readBuffers[bufferIndex][index].lazySet(node);
+
+ return writeCount;
+ }
+
+ /**
+ * Attempts to drain the buffers if it is determined to be needed when
+ * post-processing a read.
+ *
+ * @param bufferIndex the index to the chosen read buffer
+ * @param writeCount the number of writes on the chosen read buffer
+ */
+ void drainOnReadIfNeeded(int bufferIndex, long writeCount) {
+ final long pending = (writeCount -
readBufferDrainAtWriteCount[bufferIndex].get());
+ final boolean delayable = (pending < READ_BUFFER_THRESHOLD);
+ final DrainStatus status = drainStatus.get();
+ if (status.shouldDrainBuffers(delayable)) {
+ tryToDrainBuffers();
+ }
+ }
+
+ /**
+ * Performs the post-processing work required after a write.
+ *
+ * @param task the pending operation to be applied
+ */
+ void afterWrite(Runnable task) {
+ writeBuffer.add(task);
+ drainStatus.lazySet(REQUIRED);
+ tryToDrainBuffers();
+ notifyListener();
+ }
+
+ /**
+ * Attempts to acquire the eviction lock and apply the pending operations, up
+ * to the amortized threshold, to the page replacement policy.
+ */
+ void tryToDrainBuffers() {
+ if (evictionLock.tryLock()) {
+ try {
+ drainStatus.lazySet(PROCESSING);
+ drainBuffers();
+ } finally {
+ drainStatus.compareAndSet(PROCESSING, IDLE);
+ evictionLock.unlock();
+ }
+ }
+ }
+
+ /** Drains the read and write buffers up to an amortized threshold. */
+ void drainBuffers() {
+ drainReadBuffers();
+ drainWriteBuffer();
+ }
+
+ /** Drains the read buffers, each up to an amortized threshold. */
+ void drainReadBuffers() {
+ final int start = (int) Thread.currentThread().getId();
+ final int end = start + NUMBER_OF_READ_BUFFERS;
+ for (int i = start; i < end; i++) {
+ drainReadBuffer(i & READ_BUFFERS_MASK);
+ }
+ }
+
+ /** Drains the read buffer up to an amortized threshold. */
+ void drainReadBuffer(int bufferIndex) {
+ final long writeCount = readBufferWriteCount[bufferIndex].get();
+ for (int i = 0; i < READ_BUFFER_DRAIN_THRESHOLD; i++) {
+ final int index = (int) (readBufferReadCount[bufferIndex] &
READ_BUFFER_INDEX_MASK);
+ final AtomicReference<Node<K, V>> slot = readBuffers[bufferIndex][index];
+ final Node<K, V> node = slot.get();
+ if (node == null) {
+ break;
+ }
+
+ slot.lazySet(null);
+ applyRead(node);
+ readBufferReadCount[bufferIndex]++;
+ }
+ readBufferDrainAtWriteCount[bufferIndex].lazySet(writeCount);
+ }
+
+ /** Updates the node's location in the page replacement policy. */
+ void applyRead(Node<K, V> node) {
+ // An entry may be scheduled for reordering despite having been removed.
+ // This can occur when the entry was concurrently read while a writer was
+ // removing it. If the entry is no longer linked then it does not need to
+ // be processed.
+ if (evictionDeque.contains(node)) {
+ evictionDeque.moveToBack(node);
+ }
+ }
+
+ /** Drains the read buffer up to an amortized threshold. */
+ void drainWriteBuffer() {
+ for (int i = 0; i < WRITE_BUFFER_DRAIN_THRESHOLD; i++) {
+ final Runnable task = writeBuffer.poll();
+ if (task == null) {
+ break;
+ }
+ task.run();
+ }
+ }
+
+ /**
+ * Attempts to transition the node from the <tt>alive</tt> state to the
+ * <tt>retired</tt> state.
+ *
+ * @param node the entry in the page replacement policy
+ * @param expect the expected weighted value
+ * @return if successful
+ */
+ boolean tryToRetire(Node<K, V> node, WeightedValue<V> expect) {
+ if (expect.isAlive()) {
+ final WeightedValue<V> retired = new WeightedValue<V>(expect.value,
-expect.weight);
+ return node.compareAndSet(expect, retired);
+ }
+ return false;
+ }
+
+ /**
+ * Atomically transitions the node from the <tt>alive</tt> state to the
+ * <tt>retired</tt> state, if a valid transition.
+ *
+ * @param node the entry in the page replacement policy
+ */
+ void makeRetired(Node<K, V> node) {
+ for (;;) {
+ final WeightedValue<V> current = node.get();
+ if (!current.isAlive()) {
+ return;
+ }
+ final WeightedValue<V> retired = new WeightedValue<V>(current.value,
-current.weight);
+ if (node.compareAndSet(current, retired)) {
+ return;
+ }
+ }
+ }
+
+ /**
+ * Atomically transitions the node to the <tt>dead</tt> state and decrements
+ * the <tt>weightedSize</tt>.
+ *
+ * @param node the entry in the page replacement policy
+ */
+ void makeDead(Node<K, V> node) {
+ for (;;) {
+ WeightedValue<V> current = node.get();
+ WeightedValue<V> dead = new WeightedValue<V>(current.value, 0);
+ if (node.compareAndSet(current, dead)) {
+ weightedSize.lazySet(weightedSize.get() - Math.abs(current.weight));
+ return;
+ }
+ }
+ }
+
+ /** Notifies the listener of entries that were evicted. */
+ void notifyListener() {
+ Node<K, V> node;
+ while ((node = pendingNotifications.poll()) != null) {
+ listener.onEviction(node.key, node.getValue());
+ }
+ }
+
+ /** Adds the node to the page replacement policy. */
+ final class AddTask implements Runnable {
+ final Node<K, V> node;
+ final int weight;
+
+ AddTask(Node<K, V> node, int weight) {
+ this.weight = weight;
+ this.node = node;
+ }
+
+ @Override
+ public void run() {
+ weightedSize.lazySet(weightedSize.get() + weight);
+
+ // ignore out-of-order write operations
+ if (node.get().isAlive()) {
+ evictionDeque.add(node);
+ evict();
+ }
+ }
+ }
+
+ /** Removes a node from the page replacement policy. */
+ final class RemovalTask implements Runnable {
+ final Node<K, V> node;
+
+ RemovalTask(Node<K, V> node) {
+ this.node = node;
+ }
+
+ @Override
+ public void run() {
+ // add may not have been processed yet
+ evictionDeque.remove(node);
+ makeDead(node);
+ }
+ }
+
+ /** Updates the weighted size and evicts an entry on overflow. */
+ final class UpdateTask implements Runnable {
+ final int weightDifference;
+ final Node<K, V> node;
+
+ public UpdateTask(Node<K, V> node, int weightDifference) {
+ this.weightDifference = weightDifference;
+ this.node = node;
+ }
+
+ @Override
+ public void run() {
+ weightedSize.lazySet(weightedSize.get() + weightDifference);
+ applyRead(node);
+ evict();
+ }
+ }
+
+ /* ---------------- Concurrent Map Support -------------- */
+
+ @Override
+ public boolean isEmpty() {
+ return data.isEmpty();
+ }
+
+ @Override
+ public int size() {
+ return data.size();
+ }
+
+ /**
+ * Returns the weighted size of this map.
+ *
+ * @return the combined weight of the values in this map
+ */
+ public long weightedSize() {
+ return Math.max(0, weightedSize.get());
+ }
+
+ @Override
+ public void clear() {
+ evictionLock.lock();
+ try {
+ // Discard all entries
+ Node<K, V> node;
+ while ((node = evictionDeque.poll()) != null) {
+ data.remove(node.key, node);
+ makeDead(node);
+ }
+
+ // Discard all pending reads
+ for (AtomicReference<Node<K, V>>[] buffer : readBuffers) {
+ for (AtomicReference<Node<K, V>> slot : buffer) {
+ slot.lazySet(null);
+ }
+ }
+
+ // Apply all pending writes
+ Runnable task;
+ while ((task = writeBuffer.poll()) != null) {
+ task.run();
+ }
+ } finally {
+ evictionLock.unlock();
+ }
+ }
+
+ @Override
+ public boolean containsKey(Object key) {
+ return data.containsKey(key);
+ }
+
+ @Override
+ public boolean containsValue(Object value) {
+ checkNotNull(value);
+
+ for (Node<K, V> node : data.values()) {
+ if (node.getValue().equals(value)) {
+ return true;
+ }
+ }
+ return false;
+ }
+
+ @Override
+ public V get(Object key) {
+ final Node<K, V> node = data.get(key);
+ if (node == null) {
+ return null;
+ }
+ afterRead(node);
+ return node.getValue();
+ }
+
+ /**
+ * Returns the value to which the specified key is mapped, or {@code null}
+ * if this map contains no mapping for the key. This method differs from
+ * {@link #get(Object)} in that it does not record the operation with the
+ * page replacement policy.
+ *
+ * @param key the key whose associated value is to be returned
+ * @return the value to which the specified key is mapped, or
+ * {@code null} if this map contains no mapping for the key
+ * @throws NullPointerException if the specified key is null
+ */
+ public V getQuietly(Object key) {
+ final Node<K, V> node = data.get(key);
+ return (node == null) ? null : node.getValue();
+ }
+
+ @Override
+ public V put(K key, V value) {
+ return put(key, value, false);
+ }
+
+ @Override
+ public V putIfAbsent(K key, V value) {
+ return put(key, value, true);
+ }
+
+ /**
+ * Adds a node to the list and the data store. If an existing node is found,
+ * then its value is updated if allowed.
+ *
+ * @param key key with which the specified value is to be associated
+ * @param value value to be associated with the specified key
+ * @param onlyIfAbsent a write is performed only if the key is not already
+ * associated with a value
+ * @return the prior value in the data store or null if no mapping was found
+ */
+ V put(K key, V value, boolean onlyIfAbsent) {
+ checkNotNull(key);
+ checkNotNull(value);
+
+ final int weight = weigher.weightOf(key, value);
+ final WeightedValue<V> weightedValue = new WeightedValue<V>(value, weight);
+ final Node<K, V> node = new Node<K, V>(key, weightedValue);
+
+ for (;;) {
+ final Node<K, V> prior = data.putIfAbsent(node.key, node);
+ if (prior == null) {
+ afterWrite(new AddTask(node, weight));
+ return null;
+ } else if (onlyIfAbsent) {
+ afterRead(prior);
+ return prior.getValue();
+ }
+ for (;;) {
+ final WeightedValue<V> oldWeightedValue = prior.get();
+ if (!oldWeightedValue.isAlive()) {
+ break;
+ }
+
+ if (prior.compareAndSet(oldWeightedValue, weightedValue)) {
+ final int weightedDifference = weight - oldWeightedValue.weight;
+ if (weightedDifference == 0) {
+ afterRead(prior);
+ } else {
+ afterWrite(new UpdateTask(prior, weightedDifference));
+ }
+ return oldWeightedValue.value;
+ }
+ }
+ }
+ }
+
+ @Override
+ public V remove(Object key) {
+ final Node<K, V> node = data.remove(key);
+ if (node == null) {
+ return null;
+ }
+
+ makeRetired(node);
+ afterWrite(new RemovalTask(node));
+ return node.getValue();
+ }
+
+ @Override
+ public boolean remove(Object key, Object value) {
+ final Node<K, V> node = data.get(key);
+ if ((node == null) || (value == null)) {
+ return false;
+ }
+
+ WeightedValue<V> weightedValue = node.get();
+ for (;;) {
+ if (weightedValue.contains(value)) {
+ if (tryToRetire(node, weightedValue)) {
+ if (data.remove(key, node)) {
+ afterWrite(new RemovalTask(node));
+ return true;
+ }
+ } else {
+ weightedValue = node.get();
+ if (weightedValue.isAlive()) {
+ // retry as an intermediate update may have replaced the value with
+ // an equal instance that has a different reference identity
+ continue;
+ }
+ }
+ }
+ return false;
+ }
+ }
+
+ @Override
+ public V replace(K key, V value) {
+ checkNotNull(key);
+ checkNotNull(value);
+
+ final int weight = weigher.weightOf(key, value);
+ final WeightedValue<V> weightedValue = new WeightedValue<V>(value, weight);
+
+ final Node<K, V> node = data.get(key);
+ if (node == null) {
+ return null;
+ }
+ for (;;) {
+ final WeightedValue<V> oldWeightedValue = node.get();
+ if (!oldWeightedValue.isAlive()) {
+ return null;
+ }
+ if (node.compareAndSet(oldWeightedValue, weightedValue)) {
+ final int weightedDifference = weight - oldWeightedValue.weight;
+ if (weightedDifference == 0) {
+ afterRead(node);
+ } else {
+ afterWrite(new UpdateTask(node, weightedDifference));
+ }
+ return oldWeightedValue.value;
+ }
+ }
+ }
+
+ @Override
+ public boolean replace(K key, V oldValue, V newValue) {
+ checkNotNull(key);
+ checkNotNull(oldValue);
+ checkNotNull(newValue);
+
+ final int weight = weigher.weightOf(key, newValue);
+ final WeightedValue<V> newWeightedValue = new WeightedValue<V>(newValue,
weight);
+
+ final Node<K, V> node = data.get(key);
+ if (node == null) {
+ return false;
+ }
+ for (;;) {
+ final WeightedValue<V> weightedValue = node.get();
+ if (!weightedValue.isAlive() || !weightedValue.contains(oldValue)) {
+ return false;
+ }
+ if (node.compareAndSet(weightedValue, newWeightedValue)) {
+ final int weightedDifference = weight - weightedValue.weight;
+ if (weightedDifference == 0) {
+ afterRead(node);
+ } else {
+ afterWrite(new UpdateTask(node, weightedDifference));
+ }
+ return true;
+ }
+ }
+ }
+
+ @Override
+ public Set<K> keySet() {
+ final Set<K> ks = keySet;
+ return (ks == null) ? (keySet = new KeySet()) : ks;
+ }
+
+ /**
+ * Returns a unmodifiable snapshot {@link Set} view of the keys contained in
+ * this map. The set's iterator returns the keys whose order of iteration is
+ * the ascending order in which its entries are considered eligible for
+ * retention, from the least-likely to be retained to the most-likely.
+ * <p>
+ * Beware that, unlike in {@link #keySet()}, obtaining the set is
<em>NOT</em>
+ * a constant-time operation. Because of the asynchronous nature of the page
+ * replacement policy, determining the retention ordering requires a
traversal
+ * of the keys.
+ *
+ * @return an ascending snapshot view of the keys in this map
+ */
+ public Set<K> ascendingKeySet() {
+ return ascendingKeySetWithLimit(Integer.MAX_VALUE);
+ }
+
+ /**
+ * Returns an unmodifiable snapshot {@link Set} view of the keys contained in
+ * this map. The set's iterator returns the keys whose order of iteration is
+ * the ascending order in which its entries are considered eligible for
+ * retention, from the least-likely to be retained to the most-likely.
+ * <p>
+ * Beware that, unlike in {@link #keySet()}, obtaining the set is
<em>NOT</em>
+ * a constant-time operation. Because of the asynchronous nature of the page
+ * replacement policy, determining the retention ordering requires a
traversal
+ * of the keys.
+ *
+ * @param limit the maximum size of the returned set
+ * @return a ascending snapshot view of the keys in this map
+ * @throws IllegalArgumentException if the limit is negative
+ */
+ public Set<K> ascendingKeySetWithLimit(int limit) {
+ return orderedKeySet(true, limit);
+ }
+
+ /**
+ * Returns an unmodifiable snapshot {@link Set} view of the keys contained in
+ * this map. The set's iterator returns the keys whose order of iteration is
+ * the descending order in which its entries are considered eligible for
+ * retention, from the most-likely to be retained to the least-likely.
+ * <p>
+ * Beware that, unlike in {@link #keySet()}, obtaining the set is
<em>NOT</em>
+ * a constant-time operation. Because of the asynchronous nature of the page
+ * replacement policy, determining the retention ordering requires a
traversal
+ * of the keys.
+ *
+ * @return a descending snapshot view of the keys in this map
+ */
+ public Set<K> descendingKeySet() {
+ return descendingKeySetWithLimit(Integer.MAX_VALUE);
+ }
+
+ /**
+ * Returns an unmodifiable snapshot {@link Set} view of the keys contained in
+ * this map. The set's iterator returns the keys whose order of iteration is
+ * the descending order in which its entries are considered eligible for
+ * retention, from the most-likely to be retained to the least-likely.
+ * <p>
+ * Beware that, unlike in {@link #keySet()}, obtaining the set is
<em>NOT</em>
+ * a constant-time operation. Because of the asynchronous nature of the page
+ * replacement policy, determining the retention ordering requires a
traversal
+ * of the keys.
+ *
+ * @param limit the maximum size of the returned set
+ * @return a descending snapshot view of the keys in this map
+ * @throws IllegalArgumentException if the limit is negative
+ */
+ public Set<K> descendingKeySetWithLimit(int limit) {
+ return orderedKeySet(false, limit);
+ }
+
+ Set<K> orderedKeySet(boolean ascending, int limit) {
+ checkArgument(limit >= 0);
+ evictionLock.lock();
+ try {
+ drainBuffers();
+
+ final int initialCapacity = (weigher == Weighers.entrySingleton())
+ ? Math.min(limit, (int) weightedSize())
+ : 16;
+ final Set<K> keys = new LinkedHashSet<K>(initialCapacity);
+ final Iterator<Node<K, V>> iterator = ascending
+ ? evictionDeque.iterator()
+ : evictionDeque.descendingIterator();
+ while (iterator.hasNext() && (limit > keys.size())) {
+ keys.add(iterator.next().key);
+ }
+ return unmodifiableSet(keys);
+ } finally {
+ evictionLock.unlock();
+ }
+ }
+
+ @Override
+ public Collection<V> values() {
+ final Collection<V> vs = values;
+ return (vs == null) ? (values = new Values()) : vs;
+ }
+
+ @Override
+ public Set<Entry<K, V>> entrySet() {
+ final Set<Entry<K, V>> es = entrySet;
+ return (es == null) ? (entrySet = new EntrySet()) : es;
+ }
+
+ /**
+ * Returns an unmodifiable snapshot {@link Map} view of the mappings
contained
+ * in this map. The map's collections return the mappings whose order of
+ * iteration is the ascending order in which its entries are considered
+ * eligible for retention, from the least-likely to be retained to the
+ * most-likely.
+ * <p>
+ * Beware that obtaining the mappings is <em>NOT</em> a constant-time
+ * operation. Because of the asynchronous nature of the page replacement
+ * policy, determining the retention ordering requires a traversal of the
+ * entries.
+ *
+ * @return a ascending snapshot view of this map
+ */
+ public Map<K, V> ascendingMap() {
+ return ascendingMapWithLimit(Integer.MAX_VALUE);
+ }
+
+ /**
+ * Returns an unmodifiable snapshot {@link Map} view of the mappings
contained
+ * in this map. The map's collections return the mappings whose order of
+ * iteration is the ascending order in which its entries are considered
+ * eligible for retention, from the least-likely to be retained to the
+ * most-likely.
+ * <p>
+ * Beware that obtaining the mappings is <em>NOT</em> a constant-time
+ * operation. Because of the asynchronous nature of the page replacement
+ * policy, determining the retention ordering requires a traversal of the
+ * entries.
+ *
+ * @param limit the maximum size of the returned map
+ * @return a ascending snapshot view of this map
+ * @throws IllegalArgumentException if the limit is negative
+ */
+ public Map<K, V> ascendingMapWithLimit(int limit) {
+ return orderedMap(true, limit);
+ }
+
+ /**
+ * Returns an unmodifiable snapshot {@link Map} view of the mappings
contained
+ * in this map. The map's collections return the mappings whose order of
+ * iteration is the descending order in which its entries are considered
+ * eligible for retention, from the most-likely to be retained to the
+ * least-likely.
+ * <p>
+ * Beware that obtaining the mappings is <em>NOT</em> a constant-time
+ * operation. Because of the asynchronous nature of the page replacement
+ * policy, determining the retention ordering requires a traversal of the
+ * entries.
+ *
+ * @return a descending snapshot view of this map
+ */
+ public Map<K, V> descendingMap() {
+ return descendingMapWithLimit(Integer.MAX_VALUE);
+ }
+
+ /**
+ * Returns an unmodifiable snapshot {@link Map} view of the mappings
contained
+ * in this map. The map's collections return the mappings whose order of
+ * iteration is the descending order in which its entries are considered
+ * eligible for retention, from the most-likely to be retained to the
+ * least-likely.
+ * <p>
+ * Beware that obtaining the mappings is <em>NOT</em> a constant-time
+ * operation. Because of the asynchronous nature of the page replacement
+ * policy, determining the retention ordering requires a traversal of the
+ * entries.
+ *
+ * @param limit the maximum size of the returned map
+ * @return a descending snapshot view of this map
+ * @throws IllegalArgumentException if the limit is negative
+ */
+ public Map<K, V> descendingMapWithLimit(int limit) {
+ return orderedMap(false, limit);
+ }
+
+ Map<K, V> orderedMap(boolean ascending, int limit) {
+ checkArgument(limit >= 0);
+ evictionLock.lock();
+ try {
+ drainBuffers();
+
+ final int initialCapacity = (weigher == Weighers.entrySingleton())
+ ? Math.min(limit, (int) weightedSize())
+ : 16;
+ final Map<K, V> map = new LinkedHashMap<K, V>(initialCapacity);
+ final Iterator<Node<K, V>> iterator = ascending
+ ? evictionDeque.iterator()
+ : evictionDeque.descendingIterator();
+ while (iterator.hasNext() && (limit > map.size())) {
+ Node<K, V> node = iterator.next();
+ map.put(node.key, node.getValue());
+ }
+ return unmodifiableMap(map);
+ } finally {
+ evictionLock.unlock();
+ }
+ }
+
+ /** The draining status of the buffers. */
+ enum DrainStatus {
+
+ /** A drain is not taking place. */
+ IDLE {
+ @Override boolean shouldDrainBuffers(boolean delayable) {
+ return !delayable;
+ }
+ },
+
+ /** A drain is required due to a pending write modification. */
+ REQUIRED {
+ @Override boolean shouldDrainBuffers(boolean delayable) {
+ return true;
+ }
+ },
+
+ /** A drain is in progress. */
+ PROCESSING {
+ @Override boolean shouldDrainBuffers(boolean delayable) {
+ return false;
+ }
+ };
+
+ /**
+ * Determines whether the buffers should be drained.
+ *
+ * @param delayable if a drain should be delayed until required
+ * @return if a drain should be attempted
+ */
+ abstract boolean shouldDrainBuffers(boolean delayable);
+ }
+
+ /** A value, its weight, and the entry's status. */
+ static final class WeightedValue<V> {
+ final int weight;
+ final V value;
+
+ WeightedValue(V value, int weight) {
+ this.weight = weight;
+ this.value = value;
+ }
+
+ boolean contains(Object o) {
+ return (o == value) || value.equals(o);
+ }
+
+ /**
+ * If the entry is available in the hash-table and page replacement policy.
+ */
+ boolean isAlive() {
+ return weight > 0;
+ }
+
+ /**
+ * If the entry was removed from the hash-table and is awaiting removal
from
+ * the page replacement policy.
+ */
+ boolean isRetired() {
+ return weight < 0;
+ }
+
+ /**
+ * If the entry was removed from the hash-table and the page replacement
+ * policy.
+ */
+ boolean isDead() {
+ return weight == 0;
+ }
+ }
+
+ /**
+ * A node contains the key, the weighted value, and the linkage pointers on
+ * the page-replacement algorithm's data structures.
+ */
+ @SuppressWarnings("serial")
+ static final class Node<K, V> extends AtomicReference<WeightedValue<V>>
+ implements Linked<Node<K, V>> {
+ final K key;
+ Node<K, V> prev;
+ Node<K, V> next;
+
+ /** Creates a new, unlinked node. */
+ Node(K key, WeightedValue<V> weightedValue) {
+ super(weightedValue);
+ this.key = key;
+ }
+
+ @Override
+ public Node<K, V> getPrevious() {
+ return prev;
+ }
+
+ @Override
+ public void setPrevious(Node<K, V> prev) {
+ this.prev = prev;
+ }
+
+ @Override
+ public Node<K, V> getNext() {
+ return next;
+ }
+
+ @Override
+ public void setNext(Node<K, V> next) {
+ this.next = next;
+ }
+
+ /** Retrieves the value held by the current <tt>WeightedValue</tt>. */
+ V getValue() {
+ return get().value;
+ }
+ }
+
+ /** An adapter to safely externalize the keys. */
+ final class KeySet extends AbstractSet<K> {
+ final ConcurrentLinkedHashMap<K, V> map = ConcurrentLinkedHashMap.this;
+
+ @Override
+ public int size() {
+ return map.size();
+ }
+
+ @Override
+ public void clear() {
+ map.clear();
+ }
+
+ @Override
+ public Iterator<K> iterator() {
+ return new KeyIterator();
+ }
+
+ @Override
+ public boolean contains(Object obj) {
+ return containsKey(obj);
+ }
+
+ @Override
+ public boolean remove(Object obj) {
+ return (map.remove(obj) != null);
+ }
+
+ @Override
+ public Object[] toArray() {
+ return map.data.keySet().toArray();
+ }
+
+ @Override
+ public <T> T[] toArray(T[] array) {
+ return map.data.keySet().toArray(array);
+ }
+ }
+
+ /** An adapter to safely externalize the key iterator. */
+ final class KeyIterator implements Iterator<K> {
+ final Iterator<K> iterator = data.keySet().iterator();
+ K current;
+
+ @Override
+ public boolean hasNext() {
+ return iterator.hasNext();
+ }
+
+ @Override
+ public K next() {
+ current = iterator.next();
+ return current;
+ }
+
+ @Override
+ public void remove() {
+ checkState(current != null);
+ ConcurrentLinkedHashMap.this.remove(current);
+ current = null;
+ }
+ }
+
+ /** An adapter to safely externalize the values. */
+ final class Values extends AbstractCollection<V> {
+
+ @Override
+ public int size() {
+ return ConcurrentLinkedHashMap.this.size();
+ }
+
+ @Override
+ public void clear() {
+ ConcurrentLinkedHashMap.this.clear();
+ }
+
+ @Override
+ public Iterator<V> iterator() {
+ return new ValueIterator();
+ }
+
+ @Override
+ public boolean contains(Object o) {
+ return containsValue(o);
+ }
+ }
+
+ /** An adapter to safely externalize the value iterator. */
+ final class ValueIterator implements Iterator<V> {
+ final Iterator<Node<K, V>> iterator = data.values().iterator();
+ Node<K, V> current;
+
+ @Override
+ public boolean hasNext() {
+ return iterator.hasNext();
+ }
+
+ @Override
+ public V next() {
+ current = iterator.next();
+ return current.getValue();
+ }
+
+ @Override
+ public void remove() {
+ checkState(current != null);
+ ConcurrentLinkedHashMap.this.remove(current.key);
+ current = null;
+ }
+ }
+
+ /** An adapter to safely externalize the entries. */
+ final class EntrySet extends AbstractSet<Entry<K, V>> {
+ final ConcurrentLinkedHashMap<K, V> map = ConcurrentLinkedHashMap.this;
+
+ @Override
+ public int size() {
+ return map.size();
+ }
+
+ @Override
+ public void clear() {
+ map.clear();
+ }
+
+ @Override
+ public Iterator<Entry<K, V>> iterator() {
+ return new EntryIterator();
+ }
+
+ @Override
+ public boolean contains(Object obj) {
+ if (!(obj instanceof Entry<?, ?>)) {
+ return false;
+ }
+ Entry<?, ?> entry = (Entry<?, ?>) obj;
+ Node<K, V> node = map.data.get(entry.getKey());
+ return (node != null) && (node.getValue().equals(entry.getValue()));
+ }
+
+ @Override
+ public boolean add(Entry<K, V> entry) {
+ return (map.putIfAbsent(entry.getKey(), entry.getValue()) == null);
+ }
+
+ @Override
+ public boolean remove(Object obj) {
+ if (!(obj instanceof Entry<?, ?>)) {
+ return false;
+ }
+ Entry<?, ?> entry = (Entry<?, ?>) obj;
+ return map.remove(entry.getKey(), entry.getValue());
+ }
+ }
+
+ /** An adapter to safely externalize the entry iterator. */
+ final class EntryIterator implements Iterator<Entry<K, V>> {
+ final Iterator<Node<K, V>> iterator = data.values().iterator();
+ Node<K, V> current;
+
+ @Override
+ public boolean hasNext() {
+ return iterator.hasNext();
+ }
+
+ @Override
+ public Entry<K, V> next() {
+ current = iterator.next();
+ return new WriteThroughEntry(current);
+ }
+
+ @Override
+ public void remove() {
+ checkState(current != null);
+ ConcurrentLinkedHashMap.this.remove(current.key);
+ current = null;
+ }
+ }
+
+ /** An entry that allows updates to write through to the map. */
+ final class WriteThroughEntry extends SimpleEntry<K, V> {
+ static final long serialVersionUID = 1;
+
+ WriteThroughEntry(Node<K, V> node) {
+ super(node.key, node.getValue());
+ }
+
+ @Override
+ public V setValue(V value) {
+ put(getKey(), value);
+ return super.setValue(value);
+ }
+
+ Object writeReplace() {
+ return new SimpleEntry<K, V>(this);
+ }
+ }
+
+ /** A weigher that enforces that the weight falls within a valid range. */
+ static final class BoundedEntryWeigher<K, V> implements EntryWeigher<K, V>,
Serializable {
+ static final long serialVersionUID = 1;
+ final EntryWeigher<? super K, ? super V> weigher;
+
+ BoundedEntryWeigher(EntryWeigher<? super K, ? super V> weigher) {
+ checkNotNull(weigher);
+ this.weigher = weigher;
+ }
+
+ @Override
+ public int weightOf(K key, V value) {
+ int weight = weigher.weightOf(key, value);
+ checkArgument(weight >= 1);
+ return weight;
+ }
+
+ Object writeReplace() {
+ return weigher;
+ }
+ }
+
+ /** A queue that discards all additions and is always empty. */
+ static final class DiscardingQueue extends AbstractQueue<Object> {
+ @Override public boolean add(Object e) { return true; }
+ @Override public boolean offer(Object e) { return true; }
+ @Override public Object poll() { return null; }
+ @Override public Object peek() { return null; }
+ @Override public int size() { return 0; }
+ @Override public Iterator<Object> iterator() { return
emptyList().iterator(); }
+ }
+
+ /** A listener that ignores all notifications. */
+ enum DiscardingListener implements EvictionListener<Object, Object> {
+ INSTANCE;
+
+ @Override public void onEviction(Object key, Object value) {}
+ }
+
+ /* ---------------- Serialization Support -------------- */
+
+ static final long serialVersionUID = 1;
+
+ Object writeReplace() {
+ return new SerializationProxy<K, V>(this);
+ }
+
+ private void readObject(ObjectInputStream stream) throws
InvalidObjectException {
+ throw new InvalidObjectException("Proxy required");
+ }
+
+ /**
+ * A proxy that is serialized instead of the map. The page-replacement
+ * algorithm's data structures are not serialized so the deserialized
+ * instance contains only the entries. This is acceptable as caches hold
+ * transient data that is recomputable and serialization would tend to be
+ * used as a fast warm-up process.
+ */
+ static final class SerializationProxy<K, V> implements Serializable {
+ final EntryWeigher<? super K, ? super V> weigher;
+ final EvictionListener<K, V> listener;
+ final int concurrencyLevel;
+ final Map<K, V> data;
+ final long capacity;
+
+ SerializationProxy(ConcurrentLinkedHashMap<K, V> map) {
+ concurrencyLevel = map.concurrencyLevel;
+ data = new HashMap<K, V>(map);
+ capacity = map.capacity.get();
+ listener = map.listener;
+ weigher = map.weigher;
+ }
+
+ Object readResolve() {
+ ConcurrentLinkedHashMap<K, V> map = new Builder<K, V>()
+ .concurrencyLevel(concurrencyLevel)
+ .maximumWeightedCapacity(capacity)
+ .listener(listener)
+ .weigher(weigher)
+ .build();
+ map.putAll(data);
+ return map;
+ }
+
+ static final long serialVersionUID = 1;
+ }
+
+ /* ---------------- Builder -------------- */
+
+ /**
+ * A builder that creates {@link ConcurrentLinkedHashMap} instances. It
+ * provides a flexible approach for constructing customized instances with
+ * a named parameter syntax. It can be used in the following manner:
+ * <pre>{@code
+ * ConcurrentMap<Vertex, Set<Edge>> graph = new Builder<Vertex, Set<Edge>>()
+ * .maximumWeightedCapacity(5000)
+ * .weigher(Weighers.<Edge>set())
+ * .build();
+ * }</pre>
+ */
+ public static final class Builder<K, V> {
+ static final int DEFAULT_CONCURRENCY_LEVEL = 16;
+ static final int DEFAULT_INITIAL_CAPACITY = 16;
+
+ EvictionListener<K, V> listener;
+ EntryWeigher<? super K, ? super V> weigher;
+
+ int concurrencyLevel;
+ int initialCapacity;
+ long capacity;
+
+ @SuppressWarnings("unchecked")
+ public Builder() {
+ capacity = -1;
+ weigher = Weighers.entrySingleton();
+ initialCapacity = DEFAULT_INITIAL_CAPACITY;
+ concurrencyLevel = DEFAULT_CONCURRENCY_LEVEL;
+ listener = (EvictionListener<K, V>) DiscardingListener.INSTANCE;
+ }
+
+ /**
+ * Specifies the initial capacity of the hash table (default <tt>16</tt>).
+ * This is the number of key-value pairs that the hash table can hold
+ * before a resize operation is required.
+ *
+ * @param initialCapacity the initial capacity used to size the hash table
+ * to accommodate this many entries.
+ * @throws IllegalArgumentException if the initialCapacity is negative
+ */
+ public Builder<K, V> initialCapacity(int initialCapacity) {
+ checkArgument(initialCapacity >= 0);
+ this.initialCapacity = initialCapacity;
+ return this;
+ }
+
+ /**
+ * Specifies the maximum weighted capacity to coerce the map to and may
+ * exceed it temporarily.
+ *
+ * @param capacity the weighted threshold to bound the map by
+ * @throws IllegalArgumentException if the maximumWeightedCapacity is
+ * negative
+ */
+ public Builder<K, V> maximumWeightedCapacity(long capacity) {
+ checkArgument(capacity >= 0);
+ this.capacity = capacity;
+ return this;
+ }
+
+ /**
+ * Specifies the estimated number of concurrently updating threads. The
+ * implementation performs internal sizing to try to accommodate this many
+ * threads (default <tt>16</tt>).
+ *
+ * @param concurrencyLevel the estimated number of concurrently updating
+ * threads
+ * @throws IllegalArgumentException if the concurrencyLevel is less than or
+ * equal to zero
+ */
+ public Builder<K, V> concurrencyLevel(int concurrencyLevel) {
+ checkArgument(concurrencyLevel > 0);
+ this.concurrencyLevel = concurrencyLevel;
+ return this;
+ }
+
+ /**
+ * Specifies an optional listener that is registered for notification when
+ * an entry is evicted.
+ *
+ * @param listener the object to forward evicted entries to
+ * @throws NullPointerException if the listener is null
+ */
+ public Builder<K, V> listener(EvictionListener<K, V> listener) {
+ checkNotNull(listener);
+ this.listener = listener;
+ return this;
+ }
+
+ /**
+ * Specifies an algorithm to determine how many the units of capacity a
+ * value consumes. The default algorithm bounds the map by the number of
+ * key-value pairs by giving each entry a weight of <tt>1</tt>.
+ *
+ * @param weigher the algorithm to determine a value's weight
+ * @throws NullPointerException if the weigher is null
+ */
+ public Builder<K, V> weigher(Weigher<? super V> weigher) {
+ this.weigher = (weigher == Weighers.singleton())
+ ? Weighers.<K, V>entrySingleton()
+ : new BoundedEntryWeigher<K, V>(Weighers.asEntryWeigher(weigher));
+ return this;
+ }
+
+ /**
+ * Specifies an algorithm to determine how many the units of capacity an
+ * entry consumes. The default algorithm bounds the map by the number of
+ * key-value pairs by giving each entry a weight of <tt>1</tt>.
+ *
+ * @param weigher the algorithm to determine a entry's weight
+ * @throws NullPointerException if the weigher is null
+ */
+ public Builder<K, V> weigher(EntryWeigher<? super K, ? super V> weigher) {
+ this.weigher = (weigher == Weighers.entrySingleton())
+ ? Weighers.<K, V>entrySingleton()
+ : new BoundedEntryWeigher<K, V>(weigher);
+ return this;
+ }
+
+ /**
+ * Creates a new {@link ConcurrentLinkedHashMap} instance.
+ *
+ * @throws IllegalStateException if the maximum weighted capacity was
+ * not set
+ */
+ public ConcurrentLinkedHashMap<K, V> build() {
+ checkState(capacity >= 0);
+ return new ConcurrentLinkedHashMap<K, V>(this);
+ }
+ }
+}
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+/*
+ * Copyright 2012 Google 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.apache.commons.jcs.utils.clhm;
+
+/**
+ * A class that can determine the weight of an entry. The total weight
threshold
+ * is used to determine when an eviction is required.
+ *
+ * @author [email protected] (Ben Manes)
+ * @see <a href="http://code.google.com/p/concurrentlinkedhashmap/";>
+ * http://code.google.com/p/concurrentlinkedhashmap/</a>
+ */
+public interface EntryWeigher<K, V> {
+
+ /**
+ * Measures an entry's weight to determine how many units of capacity that
+ * the key and value consumes. An entry must consume a minimum of one unit.
+ *
+ * @param key the key to weigh
+ * @param value the value to weigh
+ * @return the entry's weight
+ */
+ int weightOf(K key, V value);
+}
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+/*
+ * Copyright 2010 Google 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.apache.commons.jcs.utils.clhm;
+
+/**
+ * A listener registered for notification when an entry is evicted. An instance
+ * may be called concurrently by multiple threads to process entries. An
+ * implementation should avoid performing blocking calls or synchronizing on
+ * shared resources.
+ * <p>
+ * The listener is invoked by {@link ConcurrentLinkedHashMap} on a caller's
+ * thread and will not block other threads from operating on the map. An
+ * implementation should be aware that the caller's thread will not expect
+ * long execution times or failures as a side effect of the listener being
+ * notified. Execution safety and a fast turn around time can be achieved by
+ * performing the operation asynchronously, such as by submitting a task to an
+ * {@link java.util.concurrent.ExecutorService}.
+ *
+ * @author [email protected] (Ben Manes)
+ * @see <a href="http://code.google.com/p/concurrentlinkedhashmap/";>
+ * http://code.google.com/p/concurrentlinkedhashmap/</a>
+ */
+public interface EvictionListener<K, V> {
+
+ /**
+ * A call-back notification that the entry was evicted.
+ *
+ * @param key the entry's key
+ * @param value the entry's value
+ */
+ void onEviction(K key, V value);
+}
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+/*
+ * Copyright 2011 Google 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.apache.commons.jcs.utils.clhm;
+
+import java.util.AbstractCollection;
+import java.util.Collection;
+import java.util.Deque;
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+
+/**
+ * Linked list implementation of the {@link Deque} interface where the link
+ * pointers are tightly integrated with the element. Linked deques have no
+ * capacity restrictions; they grow as necessary to support usage. They are not
+ * thread-safe; in the absence of external synchronization, they do not support
+ * concurrent access by multiple threads. Null elements are prohibited.
+ * <p>
+ * Most <tt>LinkedDeque</tt> operations run in constant time by assuming that
+ * the {@link Linked} parameter is associated with the deque instance. Any
usage
+ * that violates this assumption will result in non-deterministic behavior.
+ * <p>
+ * The iterators returned by this class are <em>not</em> <i>fail-fast</i>: If
+ * the deque is modified at any time after the iterator is created, the
iterator
+ * will be in an unknown state. Thus, in the face of concurrent modification,
+ * the iterator risks arbitrary, non-deterministic behavior at an undetermined
+ * time in the future.
+ *
+ * @author [email protected] (Ben Manes)
+ * @param <E> the type of elements held in this collection
+ * @see <a href="http://code.google.com/p/concurrentlinkedhashmap/";>
+ * http://code.google.com/p/concurrentlinkedhashmap/</a>
+ */
+final class LinkedDeque<E extends Linked<E>> extends AbstractCollection<E>
implements Deque<E> {
+
+ // This class provides a doubly-linked list that is optimized for the virtual
+ // machine. The first and last elements are manipulated instead of a slightly
+ // more convenient sentinel element to avoid the insertion of null checks
with
+ // NullPointerException throws in the byte code. The links to a removed
+ // element are cleared to help a generational garbage collector if the
+ // discarded elements inhabit more than one generation.
+
+ /**
+ * Pointer to first node.
+ * Invariant: (first == null && last == null) ||
+ * (first.prev == null)
+ */
+ E first;
+
+ /**
+ * Pointer to last node.
+ * Invariant: (first == null && last == null) ||
+ * (last.next == null)
+ */
+ E last;
+
+ /**
+ * Links the element to the front of the deque so that it becomes the first
+ * element.
+ *
+ * @param e the unlinked element
+ */
+ void linkFirst(final E e) {
+ final E f = first;
+ first = e;
+
+ if (f == null) {
+ last = e;
+ } else {
+ f.setPrevious(e);
+ e.setNext(f);
+ }
+ }
+
+ /**
+ * Links the element to the back of the deque so that it becomes the last
+ * element.
+ *
+ * @param e the unlinked element
+ */
+ void linkLast(final E e) {
+ final E l = last;
+ last = e;
+
+ if (l == null) {
+ first = e;
+ } else {
+ l.setNext(e);
+ e.setPrevious(l);
+ }
+ }
+
+ /** Unlinks the non-null first element. */
+ E unlinkFirst() {
+ final E f = first;
+ final E next = f.getNext();
+ f.setNext(null);
+
+ first = next;
+ if (next == null) {
+ last = null;
+ } else {
+ next.setPrevious(null);
+ }
+ return f;
+ }
+
+ /** Unlinks the non-null last element. */
+ E unlinkLast() {
+ final E l = last;
+ final E prev = l.getPrevious();
+ l.setPrevious(null);
+ last = prev;
+ if (prev == null) {
+ first = null;
+ } else {
+ prev.setNext(null);
+ }
+ return l;
+ }
+
+ /** Unlinks the non-null element. */
+ void unlink(E e) {
+ final E prev = e.getPrevious();
+ final E next = e.getNext();
+
+ if (prev == null) {
+ first = next;
+ } else {
+ prev.setNext(next);
+ e.setPrevious(null);
+ }
+
+ if (next == null) {
+ last = prev;
+ } else {
+ next.setPrevious(prev);
+ e.setNext(null);
+ }
+ }
+
+ @Override
+ public boolean isEmpty() {
+ return (first == null);
+ }
+
+ void checkNotEmpty() {
+ if (isEmpty()) {
+ throw new NoSuchElementException();
+ }
+ }
+
+ /**
+ * {@inheritDoc}
+ * <p>
+ * Beware that, unlike in most collections, this method is <em>NOT</em> a
+ * constant-time operation.
+ */
+ @Override
+ public int size() {
+ int size = 0;
+ for (E e = first; e != null; e = e.getNext()) {
+ size++;
+ }
+ return size;
+ }
+
+ @Override
+ public void clear() {
+ for (E e = first; e != null;) {
+ E next = e.getNext();
+ e.setPrevious(null);
+ e.setNext(null);
+ e = next;
+ }
+ first = last = null;
+ }
+
+ @Override
+ public boolean contains(Object o) {
+ return (o instanceof Linked<?>) && contains((Linked<?>) o);
+ }
+
+ // A fast-path containment check
+ boolean contains(Linked<?> e) {
+ return (e.getPrevious() != null)
+ || (e.getNext() != null)
+ || (e == first);
+ }
+
+ /**
+ * Moves the element to the front of the deque so that it becomes the first
+ * element.
+ *
+ * @param e the linked element
+ */
+ public void moveToFront(E e) {
+ if (e != first) {
+ unlink(e);
+ linkFirst(e);
+ }
+ }
+
+ /**
+ * Moves the element to the back of the deque so that it becomes the last
+ * element.
+ *
+ * @param e the linked element
+ */
+ public void moveToBack(E e) {
+ if (e != last) {
+ unlink(e);
+ linkLast(e);
+ }
+ }
+
+ @Override
+ public E peek() {
+ return peekFirst();
+ }
+
+ @Override
+ public E peekFirst() {
+ return first;
+ }
+
+ @Override
+ public E peekLast() {
+ return last;
+ }
+
+ @Override
+ public E getFirst() {
+ checkNotEmpty();
+ return peekFirst();
+ }
+
+ @Override
+ public E getLast() {
+ checkNotEmpty();
+ return peekLast();
+ }
+
+ @Override
+ public E element() {
+ return getFirst();
+ }
+
+ @Override
+ public boolean offer(E e) {
+ return offerLast(e);
+ }
+
+ @Override
+ public boolean offerFirst(E e) {
+ if (contains(e)) {
+ return false;
+ }
+ linkFirst(e);
+ return true;
+ }
+
+ @Override
+ public boolean offerLast(E e) {
+ if (contains(e)) {
+ return false;
+ }
+ linkLast(e);
+ return true;
+ }
+
+ @Override
+ public boolean add(E e) {
+ return offerLast(e);
+ }
+
+
+ @Override
+ public void addFirst(E e) {
+ if (!offerFirst(e)) {
+ throw new IllegalArgumentException();
+ }
+ }
+
+ @Override
+ public void addLast(E e) {
+ if (!offerLast(e)) {
+ throw new IllegalArgumentException();
+ }
+ }
+
+ @Override
+ public E poll() {
+ return pollFirst();
+ }
+
+ @Override
+ public E pollFirst() {
+ return isEmpty() ? null : unlinkFirst();
+ }
+
+ @Override
+ public E pollLast() {
+ return isEmpty() ? null : unlinkLast();
+ }
+
+ @Override
+ public E remove() {
+ return removeFirst();
+ }
+
+ @Override
+ @SuppressWarnings("unchecked")
+ public boolean remove(Object o) {
+ return (o instanceof Linked<?>) && remove((E) o);
+ }
+
+ // A fast-path removal
+ boolean remove(E e) {
+ if (contains(e)) {
+ unlink(e);
+ return true;
+ }
+ return false;
+ }
+
+ @Override
+ public E removeFirst() {
+ checkNotEmpty();
+ return pollFirst();
+ }
+
+ @Override
+ public boolean removeFirstOccurrence(Object o) {
+ return remove(o);
+ }
+
+ @Override
+ public E removeLast() {
+ checkNotEmpty();
+ return pollLast();
+ }
+
+ @Override
+ public boolean removeLastOccurrence(Object o) {
+ return remove(o);
+ }
+
+ @Override
+ public boolean removeAll(Collection<?> c) {
+ boolean modified = false;
+ for (Object o : c) {
+ modified |= remove(o);
+ }
+ return modified;
+ }
+
+ @Override
+ public void push(E e) {
+ addFirst(e);
+ }
+
+ @Override
+ public E pop() {
+ return removeFirst();
+ }
+
+ @Override
+ public Iterator<E> iterator() {
+ return new AbstractLinkedIterator(first) {
+ @Override E computeNext() {
+ return cursor.getNext();
+ }
+ };
+ }
+
+ @Override
+ public Iterator<E> descendingIterator() {
+ return new AbstractLinkedIterator(last) {
+ @Override E computeNext() {
+ return cursor.getPrevious();
+ }
+ };
+ }
+
+ abstract class AbstractLinkedIterator implements Iterator<E> {
+ E cursor;
+
+ /**
+ * Creates an iterator that can can traverse the deque.
+ *
+ * @param start the initial element to begin traversal from
+ */
+ AbstractLinkedIterator(E start) {
+ cursor = start;
+ }
+
+ @Override
+ public boolean hasNext() {
+ return (cursor != null);
+ }
+
+ @Override
+ public E next() {
+ if (!hasNext()) {
+ throw new NoSuchElementException();
+ }
+ E e = cursor;
+ cursor = computeNext();
+ return e;
+ }
+
+ @Override
+ public void remove() {
+ throw new UnsupportedOperationException();
+ }
+
+ /**
+ * Retrieves the next element to traverse to or <tt>null</tt> if there are
+ * no more elements.
+ */
+ abstract E computeNext();
+ }
+}
+
+/**
+ * An element that is linked on the {@link Deque}.
+ */
+interface Linked<T extends Linked<T>> {
+
+ /**
+ * Retrieves the previous element or <tt>null</tt> if either the element is
+ * unlinked or the first element on the deque.
+ */
+ T getPrevious();
+
+ /** Sets the previous element or <tt>null</tt> if there is no link. */
+ void setPrevious(T prev);
+
+ /**
+ * Retrieves the next element or <tt>null</tt> if either the element is
+ * unlinked or the last element on the deque.
+ */
+ T getNext();
+
+ /** Sets the next element or <tt>null</tt> if there is no link. */
+ void setNext(T next);
+}
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+/*
+ * Copyright 2010 Google 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.apache.commons.jcs.utils.clhm;
+
+/**
+ * A class that can determine the weight of a value. The total weight threshold
+ * is used to determine when an eviction is required.
+ *
+ * @author [email protected] (Ben Manes)
+ * @see <a href="http://code.google.com/p/concurrentlinkedhashmap/";>
+ * http://code.google.com/p/concurrentlinkedhashmap/</a>
+ */
+public interface Weigher<V> {
+
+ /**
+ * Measures an object's weight to determine how many units of capacity that
+ * the value consumes. A value must consume a minimum of one unit.
+ *
+ * @param value the object to weigh
+ * @return the object's weight
+ */
+ int weightOf(V value);
+}
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+/*
+ * Copyright 2010 Google 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.apache.commons.jcs.utils.clhm;
+
+import static
org.apache.commons.jcs.utils.clhm.ConcurrentLinkedHashMap.checkNotNull;
+
+import java.io.Serializable;
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+/**
+ * A common set of {@link Weigher} and {@link EntryWeigher} implementations.
+ *
+ * @author [email protected] (Ben Manes)
+ * @see <a href="http://code.google.com/p/concurrentlinkedhashmap/";>
+ * http://code.google.com/p/concurrentlinkedhashmap/</a>
+ */
+public final class Weighers {
+
+ private Weighers() {
+ throw new AssertionError();
+ }
+
+ /**
+ * A entry weigher backed by the specified weigher. The weight of the value
+ * determines the weight of the entry.
+ *
+ * @param weigher the weigher to be "wrapped" in a entry weigher.
+ * @return A entry weigher view of the specified weigher.
+ */
+ public static <K, V> EntryWeigher<K, V> asEntryWeigher(
+ final Weigher<? super V> weigher) {
+ return (weigher == singleton())
+ ? Weighers.<K, V>entrySingleton()
+ : new EntryWeigherView<K, V>(weigher);
+ }
+
+ /**
+ * A weigher where an entry has a weight of <tt>1</tt>. A map bounded with
+ * this weigher will evict when the number of key-value pairs exceeds the
+ * capacity.
+ *
+ * @return A weigher where a value takes one unit of capacity.
+ */
+ @SuppressWarnings({"cast", "unchecked"})
+ public static <K, V> EntryWeigher<K, V> entrySingleton() {
+ return (EntryWeigher<K, V>) SingletonEntryWeigher.INSTANCE;
+ }
+
+ /**
+ * A weigher where a value has a weight of <tt>1</tt>. A map bounded with
+ * this weigher will evict when the number of key-value pairs exceeds the
+ * capacity.
+ *
+ * @return A weigher where a value takes one unit of capacity.
+ */
+ @SuppressWarnings({"cast", "unchecked"})
+ public static <V> Weigher<V> singleton() {
+ return (Weigher<V>) SingletonWeigher.INSTANCE;
+ }
+
+ /**
+ * A weigher where the value is a byte array and its weight is the number of
+ * bytes. A map bounded with this weigher will evict when the number of bytes
+ * exceeds the capacity rather than the number of key-value pairs in the map.
+ * This allows for restricting the capacity based on the memory-consumption
+ * and is primarily for usage by dedicated caching servers that hold the
+ * serialized data.
+ * <p>
+ * A value with a weight of <tt>0</tt> will be rejected by the map. If a
value
+ * with this weight can occur then the caller should eagerly evaluate the
+ * value and treat it as a removal operation. Alternatively, a custom weigher
+ * may be specified on the map to assign an empty value a positive weight.
+ *
+ * @return A weigher where each byte takes one unit of capacity.
+ */
+ public static Weigher<byte[]> byteArray() {
+ return ByteArrayWeigher.INSTANCE;
+ }
+
+ /**
+ * A weigher where the value is a {@link Iterable} and its weight is the
+ * number of elements. This weigher only should be used when the alternative
+ * {@link #collection()} weigher cannot be, as evaluation takes O(n) time. A
+ * map bounded with this weigher will evict when the total number of elements
+ * exceeds the capacity rather than the number of key-value pairs in the map.
+ * <p>
+ * A value with a weight of <tt>0</tt> will be rejected by the map. If a
value
+ * with this weight can occur then the caller should eagerly evaluate the
+ * value and treat it as a removal operation. Alternatively, a custom weigher
+ * may be specified on the map to assign an empty value a positive weight.
+ *
+ * @return A weigher where each element takes one unit of capacity.
+ */
+ @SuppressWarnings({"cast", "unchecked"})
+ public static <E> Weigher<? super Iterable<E>> iterable() {
+ return (Weigher<Iterable<E>>) (Weigher<?>) IterableWeigher.INSTANCE;
+ }
+
+ /**
+ * A weigher where the value is a {@link Collection} and its weight is the
+ * number of elements. A map bounded with this weigher will evict when the
+ * total number of elements exceeds the capacity rather than the number of
+ * key-value pairs in the map.
+ * <p>
+ * A value with a weight of <tt>0</tt> will be rejected by the map. If a
value
+ * with this weight can occur then the caller should eagerly evaluate the
+ * value and treat it as a removal operation. Alternatively, a custom weigher
+ * may be specified on the map to assign an empty value a positive weight.
+ *
+ * @return A weigher where each element takes one unit of capacity.
+ */
+ @SuppressWarnings({"cast", "unchecked"})
+ public static <E> Weigher<? super Collection<E>> collection() {
+ return (Weigher<Collection<E>>) (Weigher<?>) CollectionWeigher.INSTANCE;
+ }
+
+ /**
+ * A weigher where the value is a {@link List} and its weight is the number
+ * of elements. A map bounded with this weigher will evict when the total
+ * number of elements exceeds the capacity rather than the number of
+ * key-value pairs in the map.
+ * <p>
+ * A value with a weight of <tt>0</tt> will be rejected by the map. If a
value
+ * with this weight can occur then the caller should eagerly evaluate the
+ * value and treat it as a removal operation. Alternatively, a custom weigher
+ * may be specified on the map to assign an empty value a positive weight.
+ *
+ * @return A weigher where each element takes one unit of capacity.
+ */
+ @SuppressWarnings({"cast", "unchecked"})
+ public static <E> Weigher<? super List<E>> list() {
+ return (Weigher<List<E>>) (Weigher<?>) ListWeigher.INSTANCE;
+ }
+
+ /**
+ * A weigher where the value is a {@link Set} and its weight is the number
+ * of elements. A map bounded with this weigher will evict when the total
+ * number of elements exceeds the capacity rather than the number of
+ * key-value pairs in the map.
+ * <p>
+ * A value with a weight of <tt>0</tt> will be rejected by the map. If a
value
+ * with this weight can occur then the caller should eagerly evaluate the
+ * value and treat it as a removal operation. Alternatively, a custom weigher
+ * may be specified on the map to assign an empty value a positive weight.
+ *
+ * @return A weigher where each element takes one unit of capacity.
+ */
+ @SuppressWarnings({"cast", "unchecked"})
+ public static <E> Weigher<? super Set<E>> set() {
+ return (Weigher<Set<E>>) (Weigher<?>) SetWeigher.INSTANCE;
+ }
+
+ /**
+ * A weigher where the value is a {@link Map} and its weight is the number of
+ * entries. A map bounded with this weigher will evict when the total number
of
+ * entries across all values exceeds the capacity rather than the number of
+ * key-value pairs in the map.
+ * <p>
+ * A value with a weight of <tt>0</tt> will be rejected by the map. If a
value
+ * with this weight can occur then the caller should eagerly evaluate the
+ * value and treat it as a removal operation. Alternatively, a custom weigher
+ * may be specified on the map to assign an empty value a positive weight.
+ *
+ * @return A weigher where each entry takes one unit of capacity.
+ */
+ @SuppressWarnings({"cast", "unchecked"})
+ public static <A, B> Weigher<? super Map<A, B>> map() {
+ return (Weigher<Map<A, B>>) (Weigher<?>) MapWeigher.INSTANCE;
+ }
+
+ static final class EntryWeigherView<K, V> implements EntryWeigher<K, V>,
Serializable {
+ static final long serialVersionUID = 1;
+ final Weigher<? super V> weigher;
+
+ EntryWeigherView(Weigher<? super V> weigher) {
+ checkNotNull(weigher);
+ this.weigher = weigher;
+ }
+
+ @Override
+ public int weightOf(K key, V value) {
+ return weigher.weightOf(value);
+ }
+ }
+
+ enum SingletonEntryWeigher implements EntryWeigher<Object, Object> {
+ INSTANCE;
+
+ @Override
+ public int weightOf(Object key, Object value) {
+ return 1;
+ }
+ }
+
+ enum SingletonWeigher implements Weigher<Object> {
+ INSTANCE;
+
+ @Override
+ public int weightOf(Object value) {
+ return 1;
+ }
+ }
+
+ enum ByteArrayWeigher implements Weigher<byte[]> {
+ INSTANCE;
+
+ @Override
+ public int weightOf(byte[] value) {
+ return value.length;
+ }
+ }
+
+ enum IterableWeigher implements Weigher<Iterable<?>> {
+ INSTANCE;
+
+ @Override
+ public int weightOf(Iterable<?> values) {
+ if (values instanceof Collection<?>) {
+ return ((Collection<?>) values).size();
+ }
+ int size = 0;
+ for (Iterator<?> i = values.iterator(); i.hasNext();) {
+ i.next();
+ size++;
+ }
+ return size;
+ }
+ }
+
+ enum CollectionWeigher implements Weigher<Collection<?>> {
+ INSTANCE;
+
+ @Override
+ public int weightOf(Collection<?> values) {
+ return values.size();
+ }
+ }
+
+ enum ListWeigher implements Weigher<List<?>> {
+ INSTANCE;
+
+ @Override
+ public int weightOf(List<?> values) {
+ return values.size();
+ }
+ }
+
+ enum SetWeigher implements Weigher<Set<?>> {
+ INSTANCE;
+
+ @Override
+ public int weightOf(Set<?> values) {
+ return values.size();
+ }
+ }
+
+ enum MapWeigher implements Weigher<Map<?, ?>> {
+ INSTANCE;
+
+ @Override
+ public int weightOf(Map<?, ?> values) {
+ return values.size();
+ }
+ }
+}
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+/*
+ * Copyright 2011 Google 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.
+ */
+
+/**
+ * This package contains an implementation of a bounded
+ * {@link java.util.concurrent.ConcurrentMap} data structure.
+ * <p>
+ * {@link org.apache.commons.jcs.utils.clhm.Weigher} is a simple interface
+ * for determining how many units of capacity an entry consumes. Depending on
+ * which concrete Weigher class is used, an entry may consume a different
amount
+ * of space within the cache. The
+ * {@link org.apache.commons.jcs.utils.clhm.Weighers} class provides
+ * utility methods for obtaining the most common kinds of implementations.
+ * <p>
+ * {@link org.apache.commons.jcs.utils.clhm.EvictionListener} provides the
+ * ability to be notified when an entry is evicted from the map. An eviction
+ * occurs when the entry was automatically removed due to the map exceeding a
+ * capacity threshold. It is not called when an entry was explicitly removed.
+ * <p>
+ * The {@link org.apache.commons.jcs.utils.clhm.ConcurrentLinkedHashMap}
+ * class supplies an efficient, scalable, thread-safe, bounded map. As with the
+ * <tt>Java Collections Framework</tt> the "Concurrent" prefix is used to
+ * indicate that the map is not governed by a single exclusion lock.
+ *
+ * @see <a href="http://code.google.com/p/concurrentlinkedhashmap/";>
+ * http://code.google.com/p/concurrentlinkedhashmap/</a>
+ */
+package org.apache.commons.jcs.utils.clhm;
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+<!--
+ Licensed to the Apache Software Foundation (ASF) under one
+ or more contributor license agreements. See the NOTICE file
+ distributed with this work for additional information
+ regarding copyright ownership. The ASF licenses this file
+ to you 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.
+-->
+<html>
+ <head>
+ </head>
+ <body>
+ This is a clone of Ben Manes <code>ConcurrentLinkedHashMap</code>
+ <pre>
+ Copyright 2008, Ben Manes
+ Copyright 2010, Google Inc.
+
+ Some alternate data structures provided by JSR-166e
+ from http://gee.cs.oswego.edu/dl/concurrency-interest/.
+ Written by Doug Lea and released as Public Domain.
+ </pre>
+ </body>
+</html>
