Repository: groovy Updated Branches: refs/heads/GROOVY_2_5_X d7916b304 -> 6be146e19
Add concurrentlinkedhashmap Project: http://git-wip-us.apache.org/repos/asf/groovy/repo Commit: http://git-wip-us.apache.org/repos/asf/groovy/commit/6be146e1 Tree: http://git-wip-us.apache.org/repos/asf/groovy/tree/6be146e1 Diff: http://git-wip-us.apache.org/repos/asf/groovy/diff/6be146e1 Branch: refs/heads/GROOVY_2_5_X Commit: 6be146e19b233e017c389b05be25d4fa4825b228 Parents: d7916b3 Author: sunlan <[email protected]> Authored: Sat Dec 2 00:45:18 2017 +0800 Committer: sunlan <[email protected]> Committed: Sat Dec 2 00:45:18 2017 +0800 ---------------------------------------------------------------------- build.gradle | 3 + .../ConcurrentLinkedHashMap.java | 1600 ++++++++++++++++++ .../concurrentlinkedhashmap/EntryWeigher.java | 40 + .../EvictionListener.java | 48 + .../concurrentlinkedhashmap/LinkedDeque.java | 462 +++++ .../util/concurrentlinkedhashmap/Weigher.java | 39 + .../util/concurrentlinkedhashmap/Weighers.java | 282 +++ .../concurrentlinkedhashmap/package-info.java | 41 + 8 files changed, 2515 insertions(+) ---------------------------------------------------------------------- http://git-wip-us.apache.org/repos/asf/groovy/blob/6be146e1/build.gradle ---------------------------------------------------------------------- diff --git a/build.gradle b/build.gradle index f3bbfb4..17a281f 100644 --- a/build.gradle +++ b/build.gradle @@ -175,6 +175,7 @@ ext { xmlunitVersion = '1.6' xstreamVersion = '1.4.10' spockVersion = '1.0-groovy-2.4' + jsr305Version = '3.0.2' isReleaseVersion = !groovyVersion.toLowerCase().endsWith("snapshot") } @@ -201,6 +202,8 @@ dependencies { } compile files("${buildDir}/generated-classes") + compileOnly "com.google.code.findbugs:jsr305:$jsr305Version" + runtime("org.codehaus.gpars:gpars:$gparsVersion") { exclude(group: 'org.codehaus.groovy', module: 'groovy-all') } http://git-wip-us.apache.org/repos/asf/groovy/blob/6be146e1/src/main/org/apache/groovy/util/concurrentlinkedhashmap/ConcurrentLinkedHashMap.java ---------------------------------------------------------------------- diff --git a/src/main/org/apache/groovy/util/concurrentlinkedhashmap/ConcurrentLinkedHashMap.java b/src/main/org/apache/groovy/util/concurrentlinkedhashmap/ConcurrentLinkedHashMap.java new file mode 100644 index 0000000..938ef63 --- /dev/null +++ b/src/main/org/apache/groovy/util/concurrentlinkedhashmap/ConcurrentLinkedHashMap.java @@ -0,0 +1,1600 @@ +/* + * 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.groovy.util.concurrentlinkedhashmap; + +import javax.annotation.concurrent.GuardedBy; +import javax.annotation.concurrent.Immutable; +import javax.annotation.concurrent.ThreadSafe; +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; + +import static java.util.Collections.emptyList; +import static java.util.Collections.unmodifiableMap; +import static java.util.Collections.unmodifiableSet; +import static org.apache.groovy.util.concurrentlinkedhashmap.ConcurrentLinkedHashMap.DrainStatus.IDLE; +import static org.apache.groovy.util.concurrentlinkedhashmap.ConcurrentLinkedHashMap.DrainStatus.PROCESSING; +import static org.apache.groovy.util.concurrentlinkedhashmap.ConcurrentLinkedHashMap.DrainStatus.REQUIRED; + +/** + * 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 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> + */ +@ThreadSafe +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 + @GuardedBy("evictionLock") + final long[] readBufferReadCount; + @GuardedBy("evictionLock") + final LinkedDeque<Node<K, V>> evictionDeque; + + @GuardedBy("evictionLock") // must write under lock + final AtomicLong weightedSize; + @GuardedBy("evictionLock") // must write under lock + 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. */ + @GuardedBy("evictionLock") + 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. + */ + @GuardedBy("evictionLock") + 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. */ + @GuardedBy("evictionLock") + void drainBuffers() { + drainReadBuffers(); + drainWriteBuffer(); + } + + /** Drains the read buffers, each up to an amortized threshold. */ + @GuardedBy("evictionLock") + 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. */ + @GuardedBy("evictionLock") + 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. */ + @GuardedBy("evictionLock") + 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. */ + @GuardedBy("evictionLock") + 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 + */ + @GuardedBy("evictionLock") + 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 + @GuardedBy("evictionLock") + 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 + @GuardedBy("evictionLock") + 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 + @GuardedBy("evictionLock") + 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. */ + @Immutable + 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; + @GuardedBy("evictionLock") + Node<K, V> prev; + @GuardedBy("evictionLock") + Node<K, V> next; + + /** Creates a new, unlinked node. */ + Node(K key, WeightedValue<V> weightedValue) { + super(weightedValue); + this.key = key; + } + + @Override + @GuardedBy("evictionLock") + public Node<K, V> getPrevious() { + return prev; + } + + @Override + @GuardedBy("evictionLock") + public void setPrevious(Node<K, V> prev) { + this.prev = prev; + } + + @Override + @GuardedBy("evictionLock") + public Node<K, V> getNext() { + return next; + } + + @Override + @GuardedBy("evictionLock") + 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); + } + } +} http://git-wip-us.apache.org/repos/asf/groovy/blob/6be146e1/src/main/org/apache/groovy/util/concurrentlinkedhashmap/EntryWeigher.java ---------------------------------------------------------------------- diff --git a/src/main/org/apache/groovy/util/concurrentlinkedhashmap/EntryWeigher.java b/src/main/org/apache/groovy/util/concurrentlinkedhashmap/EntryWeigher.java new file mode 100644 index 0000000..1075c10 --- /dev/null +++ b/src/main/org/apache/groovy/util/concurrentlinkedhashmap/EntryWeigher.java @@ -0,0 +1,40 @@ +/* + * 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.groovy.util.concurrentlinkedhashmap; + +import javax.annotation.concurrent.ThreadSafe; + +/** + * 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> + */ +@ThreadSafe +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); +} http://git-wip-us.apache.org/repos/asf/groovy/blob/6be146e1/src/main/org/apache/groovy/util/concurrentlinkedhashmap/EvictionListener.java ---------------------------------------------------------------------- diff --git a/src/main/org/apache/groovy/util/concurrentlinkedhashmap/EvictionListener.java b/src/main/org/apache/groovy/util/concurrentlinkedhashmap/EvictionListener.java new file mode 100644 index 0000000..4b608a0 --- /dev/null +++ b/src/main/org/apache/groovy/util/concurrentlinkedhashmap/EvictionListener.java @@ -0,0 +1,48 @@ +/* + * 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.groovy.util.concurrentlinkedhashmap; + +import javax.annotation.concurrent.ThreadSafe; + +/** + * 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> + */ +@ThreadSafe +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); +} http://git-wip-us.apache.org/repos/asf/groovy/blob/6be146e1/src/main/org/apache/groovy/util/concurrentlinkedhashmap/LinkedDeque.java ---------------------------------------------------------------------- diff --git a/src/main/org/apache/groovy/util/concurrentlinkedhashmap/LinkedDeque.java b/src/main/org/apache/groovy/util/concurrentlinkedhashmap/LinkedDeque.java new file mode 100644 index 0000000..447b769 --- /dev/null +++ b/src/main/org/apache/groovy/util/concurrentlinkedhashmap/LinkedDeque.java @@ -0,0 +1,462 @@ +/* + * 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.groovy.util.concurrentlinkedhashmap; + +import javax.annotation.concurrent.NotThreadSafe; +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> + */ +@NotThreadSafe +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); +} http://git-wip-us.apache.org/repos/asf/groovy/blob/6be146e1/src/main/org/apache/groovy/util/concurrentlinkedhashmap/Weigher.java ---------------------------------------------------------------------- diff --git a/src/main/org/apache/groovy/util/concurrentlinkedhashmap/Weigher.java b/src/main/org/apache/groovy/util/concurrentlinkedhashmap/Weigher.java new file mode 100644 index 0000000..c7eac09 --- /dev/null +++ b/src/main/org/apache/groovy/util/concurrentlinkedhashmap/Weigher.java @@ -0,0 +1,39 @@ +/* + * 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.groovy.util.concurrentlinkedhashmap; + +import javax.annotation.concurrent.ThreadSafe; + +/** + * 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> + */ +@ThreadSafe +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); +} http://git-wip-us.apache.org/repos/asf/groovy/blob/6be146e1/src/main/org/apache/groovy/util/concurrentlinkedhashmap/Weighers.java ---------------------------------------------------------------------- diff --git a/src/main/org/apache/groovy/util/concurrentlinkedhashmap/Weighers.java b/src/main/org/apache/groovy/util/concurrentlinkedhashmap/Weighers.java new file mode 100644 index 0000000..6fd9b25 --- /dev/null +++ b/src/main/org/apache/groovy/util/concurrentlinkedhashmap/Weighers.java @@ -0,0 +1,282 @@ +/* + * 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.groovy.util.concurrentlinkedhashmap; + +import java.io.Serializable; +import java.util.Collection; +import java.util.Iterator; +import java.util.List; +import java.util.Map; +import java.util.Set; + +import static org.apache.groovy.util.concurrentlinkedhashmap.ConcurrentLinkedHashMap.checkNotNull; + +/** + * 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(); + } + } +} http://git-wip-us.apache.org/repos/asf/groovy/blob/6be146e1/src/main/org/apache/groovy/util/concurrentlinkedhashmap/package-info.java ---------------------------------------------------------------------- diff --git a/src/main/org/apache/groovy/util/concurrentlinkedhashmap/package-info.java b/src/main/org/apache/groovy/util/concurrentlinkedhashmap/package-info.java new file mode 100644 index 0000000..665de2e --- /dev/null +++ b/src/main/org/apache/groovy/util/concurrentlinkedhashmap/package-info.java @@ -0,0 +1,41 @@ +/* + * 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.groovy.util.concurrentlinkedhashmap.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.groovy.util.concurrentlinkedhashmap.Weighers} class provides + * utility methods for obtaining the most common kinds of implementations. + * <p> + * {@link org.apache.groovy.util.concurrentlinkedhashmap.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.groovy.util.concurrentlinkedhashmap.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.groovy.util.concurrentlinkedhashmap;
