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/*
 * Copyright (C) 2009 The Guava Authors
 *
 * 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 jersey.repackaged.com.google.common.collect;

import static jersey.repackaged.com.google.common.base.Preconditions.checkNotNull;
import static jersey.repackaged.com.google.common.base.Preconditions.checkState;

import jersey.repackaged.com.google.common.annotations.VisibleForTesting;
import jersey.repackaged.com.google.common.base.Equivalence;
import jersey.repackaged.com.google.common.base.Ticker;
import jersey.repackaged.com.google.common.collect.GenericMapMaker.NullListener;
import jersey.repackaged.com.google.common.collect.MapMaker.RemovalCause;
import jersey.repackaged.com.google.common.collect.MapMaker.RemovalListener;
import jersey.repackaged.com.google.common.collect.MapMaker.RemovalNotification;
import jersey.repackaged.com.google.common.primitives.Ints;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.lang.ref.Reference;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.SoftReference;
import java.lang.ref.WeakReference;
import java.util.AbstractCollection;
import java.util.AbstractMap;
import java.util.AbstractQueue;
import java.util.AbstractSet;
import java.util.Collection;
import java.util.Iterator;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Queue;
import java.util.Set;
import java.util.concurrent.CancellationException;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicReferenceArray;
import java.util.concurrent.locks.ReentrantLock;
import java.util.logging.Level;
import java.util.logging.Logger;

import javax.annotation.Nullable;
import javax.annotation.concurrent.GuardedBy;

/**
 * The concurrent hash map implementation built by {@link MapMaker}.
 *
 * 

This implementation is heavily derived from revision 1.96 of ConcurrentHashMap.java. * * @author Bob Lee * @author Charles Fry * @author Doug Lea ({@code ConcurrentHashMap}) */ class MapMakerInternalMap extends AbstractMap implements ConcurrentMap, Serializable { /* * The basic strategy is to subdivide the table among Segments, each of which itself is a * concurrently readable hash table. The map supports non-blocking reads and concurrent writes * across different segments. * * If a maximum size is specified, a best-effort bounding is performed per segment, using a * page-replacement algorithm to determine which entries to evict when the capacity has been * exceeded. * * The page replacement algorithm's data structures are kept casually consistent with the map. The * ordering of writes to a segment is sequentially consistent. 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 operation without enforcing the capacity constraint. * * This implementation uses a per-segment queue to record a memento of the additions, removals, * and accesses that were performed on the map. The queue is drained on writes and when it exceeds * its capacity threshold. * * 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 initial LRU implementation * operates per-segment rather than globally for increased implementation simplicity. We expect * the cache hit rate to be similar to that of a global LRU algorithm. */ // Constants /** * The maximum capacity, used if a higher value is implicitly specified by either of the * constructors with arguments. MUST be a power of two <= 1<<30 to ensure that entries are * indexable using ints. */ static final int MAXIMUM_CAPACITY = Ints.MAX_POWER_OF_TWO; /** The maximum number of segments to allow; used to bound constructor arguments. */ static final int MAX_SEGMENTS = 1 << 16; // slightly conservative /** Number of (unsynchronized) retries in the containsValue method. */ static final int CONTAINS_VALUE_RETRIES = 3; /** * Number of cache access operations that can be buffered per segment before the cache's recency * ordering information is updated. This is used to avoid lock contention by recording a memento * of reads and delaying a lock acquisition until the threshold is crossed or a mutation occurs. * *

This must be a (2^n)-1 as it is used as a mask. */ static final int DRAIN_THRESHOLD = 0x3F; /** * Maximum number of entries to be drained in a single cleanup run. This applies independently to * the cleanup queue and both reference queues. */ // TODO(fry): empirically optimize this static final int DRAIN_MAX = 16; static final long CLEANUP_EXECUTOR_DELAY_SECS = 60; // Fields private static final Logger logger = Logger.getLogger(MapMakerInternalMap.class.getName()); /** * Mask value for indexing into segments. The upper bits of a key's hash code are used to choose * the segment. */ final transient int segmentMask; /** * Shift value for indexing within segments. Helps prevent entries that end up in the same segment * from also ending up in the same bucket. */ final transient int segmentShift; /** The segments, each of which is a specialized hash table. */ final transient Segment[] segments; /** The concurrency level. */ final int concurrencyLevel; /** Strategy for comparing keys. */ final Equivalence keyEquivalence; /** Strategy for comparing values. */ final Equivalence valueEquivalence; /** Strategy for referencing keys. */ final Strength keyStrength; /** Strategy for referencing values. */ final Strength valueStrength; /** The maximum size of this map. MapMaker.UNSET_INT if there is no maximum. */ final int maximumSize; /** How long after the last access to an entry the map will retain that entry. */ final long expireAfterAccessNanos; /** How long after the last write to an entry the map will retain that entry. */ final long expireAfterWriteNanos; /** Entries waiting to be consumed by the removal listener. */ // TODO(fry): define a new type which creates event objects and automates the clear logic final Queue> removalNotificationQueue; /** * A listener that is invoked when an entry is removed due to expiration or garbage collection of * soft/weak entries. */ final RemovalListener removalListener; /** Factory used to create new entries. */ final transient EntryFactory entryFactory; /** Measures time in a testable way. */ final Ticker ticker; /** * Creates a new, empty map with the specified strategy, initial capacity and concurrency level. */ MapMakerInternalMap(MapMaker builder) { concurrencyLevel = Math.min(builder.getConcurrencyLevel(), MAX_SEGMENTS); keyStrength = builder.getKeyStrength(); valueStrength = builder.getValueStrength(); keyEquivalence = builder.getKeyEquivalence(); valueEquivalence = valueStrength.defaultEquivalence(); maximumSize = builder.maximumSize; expireAfterAccessNanos = builder.getExpireAfterAccessNanos(); expireAfterWriteNanos = builder.getExpireAfterWriteNanos(); entryFactory = EntryFactory.getFactory(keyStrength, expires(), evictsBySize()); ticker = builder.getTicker(); removalListener = builder.getRemovalListener(); removalNotificationQueue = (removalListener == NullListener.INSTANCE) ? MapMakerInternalMap.>discardingQueue() : new ConcurrentLinkedQueue>(); int initialCapacity = Math.min(builder.getInitialCapacity(), MAXIMUM_CAPACITY); if (evictsBySize()) { initialCapacity = Math.min(initialCapacity, maximumSize); } // Find power-of-two sizes best matching arguments. Constraints: // (segmentCount <= maximumSize) // && (concurrencyLevel > maximumSize || segmentCount > concurrencyLevel) int segmentShift = 0; int segmentCount = 1; while (segmentCount < concurrencyLevel && (!evictsBySize() || segmentCount * 2 <= maximumSize)) { ++segmentShift; segmentCount <<= 1; } this.segmentShift = 32 - segmentShift; segmentMask = segmentCount - 1; this.segments = newSegmentArray(segmentCount); int segmentCapacity = initialCapacity / segmentCount; if (segmentCapacity * segmentCount < initialCapacity) { ++segmentCapacity; } int segmentSize = 1; while (segmentSize < segmentCapacity) { segmentSize <<= 1; } if (evictsBySize()) { // Ensure sum of segment max sizes = overall max size int maximumSegmentSize = maximumSize / segmentCount + 1; int remainder = maximumSize % segmentCount; for (int i = 0; i < this.segments.length; ++i) { if (i == remainder) { maximumSegmentSize--; } this.segments[i] = createSegment(segmentSize, maximumSegmentSize); } } else { for (int i = 0; i < this.segments.length; ++i) { this.segments[i] = createSegment(segmentSize, MapMaker.UNSET_INT); } } } boolean evictsBySize() { return maximumSize != MapMaker.UNSET_INT; } boolean expires() { return expiresAfterWrite() || expiresAfterAccess(); } boolean expiresAfterWrite() { return expireAfterWriteNanos > 0; } boolean expiresAfterAccess() { return expireAfterAccessNanos > 0; } boolean usesKeyReferences() { return keyStrength != Strength.STRONG; } boolean usesValueReferences() { return valueStrength != Strength.STRONG; } enum Strength { /* * TODO(kevinb): If we strongly reference the value and aren't computing, we needn't wrap the * value. This could save ~8 bytes per entry. */ STRONG { @Override ValueReference referenceValue( Segment segment, ReferenceEntry entry, V value) { return new StrongValueReference(value); } @Override Equivalence defaultEquivalence() { return Equivalence.equals(); } }, SOFT { @Override ValueReference referenceValue( Segment segment, ReferenceEntry entry, V value) { return new SoftValueReference(segment.valueReferenceQueue, value, entry); } @Override Equivalence defaultEquivalence() { return Equivalence.identity(); } }, WEAK { @Override ValueReference referenceValue( Segment segment, ReferenceEntry entry, V value) { return new WeakValueReference(segment.valueReferenceQueue, value, entry); } @Override Equivalence defaultEquivalence() { return Equivalence.identity(); } }; /** * Creates a reference for the given value according to this value strength. */ abstract ValueReference referenceValue( Segment segment, ReferenceEntry entry, V value); /** * Returns the default equivalence strategy used to compare and hash keys or values referenced * at this strength. This strategy will be used unless the user explicitly specifies an * alternate strategy. */ abstract Equivalence defaultEquivalence(); } /** * Creates new entries. */ enum EntryFactory { STRONG { @Override ReferenceEntry newEntry( Segment segment, K key, int hash, @Nullable ReferenceEntry next) { return new StrongEntry(key, hash, next); } }, STRONG_EXPIRABLE { @Override ReferenceEntry newEntry( Segment segment, K key, int hash, @Nullable ReferenceEntry next) { return new StrongExpirableEntry(key, hash, next); } @Override ReferenceEntry copyEntry( Segment segment, ReferenceEntry original, ReferenceEntry newNext) { ReferenceEntry newEntry = super.copyEntry(segment, original, newNext); copyExpirableEntry(original, newEntry); return newEntry; } }, STRONG_EVICTABLE { @Override ReferenceEntry newEntry( Segment segment, K key, int hash, @Nullable ReferenceEntry next) { return new StrongEvictableEntry(key, hash, next); } @Override ReferenceEntry copyEntry( Segment segment, ReferenceEntry original, ReferenceEntry newNext) { ReferenceEntry newEntry = super.copyEntry(segment, original, newNext); copyEvictableEntry(original, newEntry); return newEntry; } }, STRONG_EXPIRABLE_EVICTABLE { @Override ReferenceEntry newEntry( Segment segment, K key, int hash, @Nullable ReferenceEntry next) { return new StrongExpirableEvictableEntry(key, hash, next); } @Override ReferenceEntry copyEntry( Segment segment, ReferenceEntry original, ReferenceEntry newNext) { ReferenceEntry newEntry = super.copyEntry(segment, original, newNext); copyExpirableEntry(original, newEntry); copyEvictableEntry(original, newEntry); return newEntry; } }, WEAK { @Override ReferenceEntry newEntry( Segment segment, K key, int hash, @Nullable ReferenceEntry next) { return new WeakEntry(segment.keyReferenceQueue, key, hash, next); } }, WEAK_EXPIRABLE { @Override ReferenceEntry newEntry( Segment segment, K key, int hash, @Nullable ReferenceEntry next) { return new WeakExpirableEntry(segment.keyReferenceQueue, key, hash, next); } @Override ReferenceEntry copyEntry( Segment segment, ReferenceEntry original, ReferenceEntry newNext) { ReferenceEntry newEntry = super.copyEntry(segment, original, newNext); copyExpirableEntry(original, newEntry); return newEntry; } }, WEAK_EVICTABLE { @Override ReferenceEntry newEntry( Segment segment, K key, int hash, @Nullable ReferenceEntry next) { return new WeakEvictableEntry(segment.keyReferenceQueue, key, hash, next); } @Override ReferenceEntry copyEntry( Segment segment, ReferenceEntry original, ReferenceEntry newNext) { ReferenceEntry newEntry = super.copyEntry(segment, original, newNext); copyEvictableEntry(original, newEntry); return newEntry; } }, WEAK_EXPIRABLE_EVICTABLE { @Override ReferenceEntry newEntry( Segment segment, K key, int hash, @Nullable ReferenceEntry next) { return new WeakExpirableEvictableEntry(segment.keyReferenceQueue, key, hash, next); } @Override ReferenceEntry copyEntry( Segment segment, ReferenceEntry original, ReferenceEntry newNext) { ReferenceEntry newEntry = super.copyEntry(segment, original, newNext); copyExpirableEntry(original, newEntry); copyEvictableEntry(original, newEntry); return newEntry; } }; /** * Masks used to compute indices in the following table. */ static final int EXPIRABLE_MASK = 1; static final int EVICTABLE_MASK = 2; /** * Look-up table for factories. First dimension is the reference type. The second dimension is * the result of OR-ing the feature masks. */ static final EntryFactory[][] factories = { { STRONG, STRONG_EXPIRABLE, STRONG_EVICTABLE, STRONG_EXPIRABLE_EVICTABLE }, {}, // no support for SOFT keys { WEAK, WEAK_EXPIRABLE, WEAK_EVICTABLE, WEAK_EXPIRABLE_EVICTABLE } }; static EntryFactory getFactory(Strength keyStrength, boolean expireAfterWrite, boolean evictsBySize) { int flags = (expireAfterWrite ? EXPIRABLE_MASK : 0) | (evictsBySize ? EVICTABLE_MASK : 0); return factories[keyStrength.ordinal()][flags]; } /** * Creates a new entry. * * @param segment to create the entry for * @param key of the entry * @param hash of the key * @param next entry in the same bucket */ abstract ReferenceEntry newEntry( Segment segment, K key, int hash, @Nullable ReferenceEntry next); /** * Copies an entry, assigning it a new {@code next} entry. * * @param original the entry to copy * @param newNext entry in the same bucket */ @GuardedBy("Segment.this") ReferenceEntry copyEntry( Segment segment, ReferenceEntry original, ReferenceEntry newNext) { return newEntry(segment, original.getKey(), original.getHash(), newNext); } @GuardedBy("Segment.this") void copyExpirableEntry(ReferenceEntry original, ReferenceEntry newEntry) { // TODO(fry): when we link values instead of entries this method can go // away, as can connectExpirables, nullifyExpirable. newEntry.setExpirationTime(original.getExpirationTime()); connectExpirables(original.getPreviousExpirable(), newEntry); connectExpirables(newEntry, original.getNextExpirable()); nullifyExpirable(original); } @GuardedBy("Segment.this") void copyEvictableEntry(ReferenceEntry original, ReferenceEntry newEntry) { // TODO(fry): when we link values instead of entries this method can go // away, as can connectEvictables, nullifyEvictable. connectEvictables(original.getPreviousEvictable(), newEntry); connectEvictables(newEntry, original.getNextEvictable()); nullifyEvictable(original); } } /** * A reference to a value. */ interface ValueReference { /** * Gets the value. Does not block or throw exceptions. */ V get(); /** * Waits for a value that may still be computing. Unlike get(), this method can block (in the * case of FutureValueReference). * * @throws ExecutionException if the computing thread throws an exception */ V waitForValue() throws ExecutionException; /** * Returns the entry associated with this value reference, or {@code null} if this value * reference is independent of any entry. */ ReferenceEntry getEntry(); /** * Creates a copy of this reference for the given entry. * *

{@code value} may be null only for a loading reference. */ ValueReference copyFor( ReferenceQueue queue, @Nullable V value, ReferenceEntry entry); /** * Clears this reference object. * * @param newValue the new value reference which will replace this one; this is only used during * computation to immediately notify blocked threads of the new value */ void clear(@Nullable ValueReference newValue); /** * Returns {@code true} if the value type is a computing reference (regardless of whether or not * computation has completed). This is necessary to distiguish between partially-collected * entries and computing entries, which need to be cleaned up differently. */ boolean isComputingReference(); } /** * Placeholder. Indicates that the value hasn't been set yet. */ static final ValueReference UNSET = new ValueReference() { @Override public Object get() { return null; } @Override public ReferenceEntry getEntry() { return null; } @Override public ValueReference copyFor(ReferenceQueue queue, @Nullable Object value, ReferenceEntry entry) { return this; } @Override public boolean isComputingReference() { return false; } @Override public Object waitForValue() { return null; } @Override public void clear(ValueReference newValue) {} }; /** * Singleton placeholder that indicates a value is being computed. */ @SuppressWarnings("unchecked") // impl never uses a parameter or returns any non-null value static ValueReference unset() { return (ValueReference) UNSET; } /** * An entry in a reference map. * * Entries in the map can be in the following states: * * Valid: * - Live: valid key/value are set * - Computing: computation is pending * * Invalid: * - Expired: time expired (key/value may still be set) * - Collected: key/value was partially collected, but not yet cleaned up */ interface ReferenceEntry { /** * Gets the value reference from this entry. */ ValueReference getValueReference(); /** * Sets the value reference for this entry. */ void setValueReference(ValueReference valueReference); /** * Gets the next entry in the chain. */ ReferenceEntry getNext(); /** * Gets the entry's hash. */ int getHash(); /** * Gets the key for this entry. */ K getKey(); /* * Used by entries that are expirable. Expirable entries are maintained in a doubly-linked list. * New entries are added at the tail of the list at write time; stale entries are expired from * the head of the list. */ /** * Gets the entry expiration time in ns. */ long getExpirationTime(); /** * Sets the entry expiration time in ns. */ void setExpirationTime(long time); /** * Gets the next entry in the recency list. */ ReferenceEntry getNextExpirable(); /** * Sets the next entry in the recency list. */ void setNextExpirable(ReferenceEntry next); /** * Gets the previous entry in the recency list. */ ReferenceEntry getPreviousExpirable(); /** * Sets the previous entry in the recency list. */ void setPreviousExpirable(ReferenceEntry previous); /* * Implemented by entries that are evictable. Evictable entries are maintained in a * doubly-linked list. New entries are added at the tail of the list at write time and stale * entries are expired from the head of the list. */ /** * Gets the next entry in the recency list. */ ReferenceEntry getNextEvictable(); /** * Sets the next entry in the recency list. */ void setNextEvictable(ReferenceEntry next); /** * Gets the previous entry in the recency list. */ ReferenceEntry getPreviousEvictable(); /** * Sets the previous entry in the recency list. */ void setPreviousEvictable(ReferenceEntry previous); } private enum NullEntry implements ReferenceEntry { INSTANCE; @Override public ValueReference getValueReference() { return null; } @Override public void setValueReference(ValueReference valueReference) {} @Override public ReferenceEntry getNext() { return null; } @Override public int getHash() { return 0; } @Override public Object getKey() { return null; } @Override public long getExpirationTime() { return 0; } @Override public void setExpirationTime(long time) {} @Override public ReferenceEntry getNextExpirable() { return this; } @Override public void setNextExpirable(ReferenceEntry next) {} @Override public ReferenceEntry getPreviousExpirable() { return this; } @Override public void setPreviousExpirable(ReferenceEntry previous) {} @Override public ReferenceEntry getNextEvictable() { return this; } @Override public void setNextEvictable(ReferenceEntry next) {} @Override public ReferenceEntry getPreviousEvictable() { return this; } @Override public void setPreviousEvictable(ReferenceEntry previous) {} } abstract static class AbstractReferenceEntry implements ReferenceEntry { @Override public ValueReference getValueReference() { throw new UnsupportedOperationException(); } @Override public void setValueReference(ValueReference valueReference) { throw new UnsupportedOperationException(); } @Override public ReferenceEntry getNext() { throw new UnsupportedOperationException(); } @Override public int getHash() { throw new UnsupportedOperationException(); } @Override public K getKey() { throw new UnsupportedOperationException(); } @Override public long getExpirationTime() { throw new UnsupportedOperationException(); } @Override public void setExpirationTime(long time) { throw new UnsupportedOperationException(); } @Override public ReferenceEntry getNextExpirable() { throw new UnsupportedOperationException(); } @Override public void setNextExpirable(ReferenceEntry next) { throw new UnsupportedOperationException(); } @Override public ReferenceEntry getPreviousExpirable() { throw new UnsupportedOperationException(); } @Override public void setPreviousExpirable(ReferenceEntry previous) { throw new UnsupportedOperationException(); } @Override public ReferenceEntry getNextEvictable() { throw new UnsupportedOperationException(); } @Override public void setNextEvictable(ReferenceEntry next) { throw new UnsupportedOperationException(); } @Override public ReferenceEntry getPreviousEvictable() { throw new UnsupportedOperationException(); } @Override public void setPreviousEvictable(ReferenceEntry previous) { throw new UnsupportedOperationException(); } } @SuppressWarnings("unchecked") // impl never uses a parameter or returns any non-null value static ReferenceEntry nullEntry() { return (ReferenceEntry) NullEntry.INSTANCE; } static final Queue DISCARDING_QUEUE = new AbstractQueue() { @Override public boolean offer(Object o) { return true; } @Override public Object peek() { return null; } @Override public Object poll() { return null; } @Override public int size() { return 0; } @Override public Iterator iterator() { return Iterators.emptyIterator(); } }; /** * Queue that discards all elements. */ @SuppressWarnings("unchecked") // impl never uses a parameter or returns any non-null value static Queue discardingQueue() { return (Queue) DISCARDING_QUEUE; } /* * Note: All of this duplicate code sucks, but it saves a lot of memory. If only Java had mixins! * To maintain this code, make a change for the strong reference type. Then, cut and paste, and * replace "Strong" with "Soft" or "Weak" within the pasted text. The primary difference is that * strong entries store the key reference directly while soft and weak entries delegate to their * respective superclasses. */ /** * Used for strongly-referenced keys. */ static class StrongEntry implements ReferenceEntry { final K key; StrongEntry(K key, int hash, @Nullable ReferenceEntry next) { this.key = key; this.hash = hash; this.next = next; } @Override public K getKey() { return this.key; } // null expiration @Override public long getExpirationTime() { throw new UnsupportedOperationException(); } @Override public void setExpirationTime(long time) { throw new UnsupportedOperationException(); } @Override public ReferenceEntry getNextExpirable() { throw new UnsupportedOperationException(); } @Override public void setNextExpirable(ReferenceEntry next) { throw new UnsupportedOperationException(); } @Override public ReferenceEntry getPreviousExpirable() { throw new UnsupportedOperationException(); } @Override public void setPreviousExpirable(ReferenceEntry previous) { throw new UnsupportedOperationException(); } // null eviction @Override public ReferenceEntry getNextEvictable() { throw new UnsupportedOperationException(); } @Override public void setNextEvictable(ReferenceEntry next) { throw new UnsupportedOperationException(); } @Override public ReferenceEntry getPreviousEvictable() { throw new UnsupportedOperationException(); } @Override public void setPreviousEvictable(ReferenceEntry previous) { throw new UnsupportedOperationException(); } // The code below is exactly the same for each entry type. final int hash; final ReferenceEntry next; volatile ValueReference valueReference = unset(); @Override public ValueReference getValueReference() { return valueReference; } @Override public void setValueReference(ValueReference valueReference) { ValueReference previous = this.valueReference; this.valueReference = valueReference; previous.clear(valueReference); } @Override public int getHash() { return hash; } @Override public ReferenceEntry getNext() { return next; } } static final class StrongExpirableEntry extends StrongEntry implements ReferenceEntry { StrongExpirableEntry(K key, int hash, @Nullable ReferenceEntry next) { super(key, hash, next); } // The code below is exactly the same for each expirable entry type. volatile long time = Long.MAX_VALUE; @Override public long getExpirationTime() { return time; } @Override public void setExpirationTime(long time) { this.time = time; } @GuardedBy("Segment.this") ReferenceEntry nextExpirable = nullEntry(); @Override public ReferenceEntry getNextExpirable() { return nextExpirable; } @Override public void setNextExpirable(ReferenceEntry next) { this.nextExpirable = next; } @GuardedBy("Segment.this") ReferenceEntry previousExpirable = nullEntry(); @Override public ReferenceEntry getPreviousExpirable() { return previousExpirable; } @Override public void setPreviousExpirable(ReferenceEntry previous) { this.previousExpirable = previous; } } static final class StrongEvictableEntry extends StrongEntry implements ReferenceEntry { StrongEvictableEntry(K key, int hash, @Nullable ReferenceEntry next) { super(key, hash, next); } // The code below is exactly the same for each evictable entry type. @GuardedBy("Segment.this") ReferenceEntry nextEvictable = nullEntry(); @Override public ReferenceEntry getNextEvictable() { return nextEvictable; } @Override public void setNextEvictable(ReferenceEntry next) { this.nextEvictable = next; } @GuardedBy("Segment.this") ReferenceEntry previousEvictable = nullEntry(); @Override public ReferenceEntry getPreviousEvictable() { return previousEvictable; } @Override public void setPreviousEvictable(ReferenceEntry previous) { this.previousEvictable = previous; } } static final class StrongExpirableEvictableEntry extends StrongEntry implements ReferenceEntry { StrongExpirableEvictableEntry(K key, int hash, @Nullable ReferenceEntry next) { super(key, hash, next); } // The code below is exactly the same for each expirable entry type. volatile long time = Long.MAX_VALUE; @Override public long getExpirationTime() { return time; } @Override public void setExpirationTime(long time) { this.time = time; } @GuardedBy("Segment.this") ReferenceEntry nextExpirable = nullEntry(); @Override public ReferenceEntry getNextExpirable() { return nextExpirable; } @Override public void setNextExpirable(ReferenceEntry next) { this.nextExpirable = next; } @GuardedBy("Segment.this") ReferenceEntry previousExpirable = nullEntry(); @Override public ReferenceEntry getPreviousExpirable() { return previousExpirable; } @Override public void setPreviousExpirable(ReferenceEntry previous) { this.previousExpirable = previous; } // The code below is exactly the same for each evictable entry type. @GuardedBy("Segment.this") ReferenceEntry nextEvictable = nullEntry(); @Override public ReferenceEntry getNextEvictable() { return nextEvictable; } @Override public void setNextEvictable(ReferenceEntry next) { this.nextEvictable = next; } @GuardedBy("Segment.this") ReferenceEntry previousEvictable = nullEntry(); @Override public ReferenceEntry getPreviousEvictable() { return previousEvictable; } @Override public void setPreviousEvictable(ReferenceEntry previous) { this.previousEvictable = previous; } } /** * Used for softly-referenced keys. */ static class SoftEntry extends SoftReference implements ReferenceEntry { SoftEntry(ReferenceQueue queue, K key, int hash, @Nullable ReferenceEntry next) { super(key, queue); this.hash = hash; this.next = next; } @Override public K getKey() { return get(); } // null expiration @Override public long getExpirationTime() { throw new UnsupportedOperationException(); } @Override public void setExpirationTime(long time) { throw new UnsupportedOperationException(); } @Override public ReferenceEntry getNextExpirable() { throw new UnsupportedOperationException(); } @Override public void setNextExpirable(ReferenceEntry next) { throw new UnsupportedOperationException(); } @Override public ReferenceEntry getPreviousExpirable() { throw new UnsupportedOperationException(); } @Override public void setPreviousExpirable(ReferenceEntry previous) { throw new UnsupportedOperationException(); } // null eviction @Override public ReferenceEntry getNextEvictable() { throw new UnsupportedOperationException(); } @Override public void setNextEvictable(ReferenceEntry next) { throw new UnsupportedOperationException(); } @Override public ReferenceEntry getPreviousEvictable() { throw new UnsupportedOperationException(); } @Override public void setPreviousEvictable(ReferenceEntry previous) { throw new UnsupportedOperationException(); } // The code below is exactly the same for each entry type. final int hash; final ReferenceEntry next; volatile ValueReference valueReference = unset(); @Override public ValueReference getValueReference() { return valueReference; } @Override public void setValueReference(ValueReference valueReference) { ValueReference previous = this.valueReference; this.valueReference = valueReference; previous.clear(valueReference); } @Override public int getHash() { return hash; } @Override public ReferenceEntry getNext() { return next; } } static final class SoftExpirableEntry extends SoftEntry implements ReferenceEntry { SoftExpirableEntry( ReferenceQueue queue, K key, int hash, @Nullable ReferenceEntry next) { super(queue, key, hash, next); } // The code below is exactly the same for each expirable entry type. volatile long time = Long.MAX_VALUE; @Override public long getExpirationTime() { return time; } @Override public void setExpirationTime(long time) { this.time = time; } @GuardedBy("Segment.this") ReferenceEntry nextExpirable = nullEntry(); @Override public ReferenceEntry getNextExpirable() { return nextExpirable; } @Override public void setNextExpirable(ReferenceEntry next) { this.nextExpirable = next; } @GuardedBy("Segment.this") ReferenceEntry previousExpirable = nullEntry(); @Override public ReferenceEntry getPreviousExpirable() { return previousExpirable; } @Override public void setPreviousExpirable(ReferenceEntry previous) { this.previousExpirable = previous; } } static final class SoftEvictableEntry extends SoftEntry implements ReferenceEntry { SoftEvictableEntry( ReferenceQueue queue, K key, int hash, @Nullable ReferenceEntry next) { super(queue, key, hash, next); } // The code below is exactly the same for each evictable entry type. @GuardedBy("Segment.this") ReferenceEntry nextEvictable = nullEntry(); @Override public ReferenceEntry getNextEvictable() { return nextEvictable; } @Override public void setNextEvictable(ReferenceEntry next) { this.nextEvictable = next; } @GuardedBy("Segment.this") ReferenceEntry previousEvictable = nullEntry(); @Override public ReferenceEntry getPreviousEvictable() { return previousEvictable; } @Override public void setPreviousEvictable(ReferenceEntry previous) { this.previousEvictable = previous; } } static final class SoftExpirableEvictableEntry extends SoftEntry implements ReferenceEntry { SoftExpirableEvictableEntry( ReferenceQueue queue, K key, int hash, @Nullable ReferenceEntry next) { super(queue, key, hash, next); } // The code below is exactly the same for each expirable entry type. volatile long time = Long.MAX_VALUE; @Override public long getExpirationTime() { return time; } @Override public void setExpirationTime(long time) { this.time = time; } @GuardedBy("Segment.this") ReferenceEntry nextExpirable = nullEntry(); @Override public ReferenceEntry getNextExpirable() { return nextExpirable; } @Override public void setNextExpirable(ReferenceEntry next) { this.nextExpirable = next; } @GuardedBy("Segment.this") ReferenceEntry previousExpirable = nullEntry(); @Override public ReferenceEntry getPreviousExpirable() { return previousExpirable; } @Override public void setPreviousExpirable(ReferenceEntry previous) { this.previousExpirable = previous; } // The code below is exactly the same for each evictable entry type. @GuardedBy("Segment.this") ReferenceEntry nextEvictable = nullEntry(); @Override public ReferenceEntry getNextEvictable() { return nextEvictable; } @Override public void setNextEvictable(ReferenceEntry next) { this.nextEvictable = next; } @GuardedBy("Segment.this") ReferenceEntry previousEvictable = nullEntry(); @Override public ReferenceEntry getPreviousEvictable() { return previousEvictable; } @Override public void setPreviousEvictable(ReferenceEntry previous) { this.previousEvictable = previous; } } /** * Used for weakly-referenced keys. */ static class WeakEntry extends WeakReference implements ReferenceEntry { WeakEntry(ReferenceQueue queue, K key, int hash, @Nullable ReferenceEntry next) { super(key, queue); this.hash = hash; this.next = next; } @Override public K getKey() { return get(); } // null expiration @Override public long getExpirationTime() { throw new UnsupportedOperationException(); } @Override public void setExpirationTime(long time) { throw new UnsupportedOperationException(); } @Override public ReferenceEntry getNextExpirable() { throw new UnsupportedOperationException(); } @Override public void setNextExpirable(ReferenceEntry next) { throw new UnsupportedOperationException(); } @Override public ReferenceEntry getPreviousExpirable() { throw new UnsupportedOperationException(); } @Override public void setPreviousExpirable(ReferenceEntry previous) { throw new UnsupportedOperationException(); } // null eviction @Override public ReferenceEntry getNextEvictable() { throw new UnsupportedOperationException(); } @Override public void setNextEvictable(ReferenceEntry next) { throw new UnsupportedOperationException(); } @Override public ReferenceEntry getPreviousEvictable() { throw new UnsupportedOperationException(); } @Override public void setPreviousEvictable(ReferenceEntry previous) { throw new UnsupportedOperationException(); } // The code below is exactly the same for each entry type. final int hash; final ReferenceEntry next; volatile ValueReference valueReference = unset(); @Override public ValueReference getValueReference() { return valueReference; } @Override public void setValueReference(ValueReference valueReference) { ValueReference previous = this.valueReference; this.valueReference = valueReference; previous.clear(valueReference); } @Override public int getHash() { return hash; } @Override public ReferenceEntry getNext() { return next; } } static final class WeakExpirableEntry extends WeakEntry implements ReferenceEntry { WeakExpirableEntry( ReferenceQueue queue, K key, int hash, @Nullable ReferenceEntry next) { super(queue, key, hash, next); } // The code below is exactly the same for each expirable entry type. volatile long time = Long.MAX_VALUE; @Override public long getExpirationTime() { return time; } @Override public void setExpirationTime(long time) { this.time = time; } @GuardedBy("Segment.this") ReferenceEntry nextExpirable = nullEntry(); @Override public ReferenceEntry getNextExpirable() { return nextExpirable; } @Override public void setNextExpirable(ReferenceEntry next) { this.nextExpirable = next; } @GuardedBy("Segment.this") ReferenceEntry previousExpirable = nullEntry(); @Override public ReferenceEntry getPreviousExpirable() { return previousExpirable; } @Override public void setPreviousExpirable(ReferenceEntry previous) { this.previousExpirable = previous; } } static final class WeakEvictableEntry extends WeakEntry implements ReferenceEntry { WeakEvictableEntry( ReferenceQueue queue, K key, int hash, @Nullable ReferenceEntry next) { super(queue, key, hash, next); } // The code below is exactly the same for each evictable entry type. @GuardedBy("Segment.this") ReferenceEntry nextEvictable = nullEntry(); @Override public ReferenceEntry getNextEvictable() { return nextEvictable; } @Override public void setNextEvictable(ReferenceEntry next) { this.nextEvictable = next; } @GuardedBy("Segment.this") ReferenceEntry previousEvictable = nullEntry(); @Override public ReferenceEntry getPreviousEvictable() { return previousEvictable; } @Override public void setPreviousEvictable(ReferenceEntry previous) { this.previousEvictable = previous; } } static final class WeakExpirableEvictableEntry extends WeakEntry implements ReferenceEntry { WeakExpirableEvictableEntry( ReferenceQueue queue, K key, int hash, @Nullable ReferenceEntry next) { super(queue, key, hash, next); } // The code below is exactly the same for each expirable entry type. volatile long time = Long.MAX_VALUE; @Override public long getExpirationTime() { return time; } @Override public void setExpirationTime(long time) { this.time = time; } @GuardedBy("Segment.this") ReferenceEntry nextExpirable = nullEntry(); @Override public ReferenceEntry getNextExpirable() { return nextExpirable; } @Override public void setNextExpirable(ReferenceEntry next) { this.nextExpirable = next; } @GuardedBy("Segment.this") ReferenceEntry previousExpirable = nullEntry(); @Override public ReferenceEntry getPreviousExpirable() { return previousExpirable; } @Override public void setPreviousExpirable(ReferenceEntry previous) { this.previousExpirable = previous; } // The code below is exactly the same for each evictable entry type. @GuardedBy("Segment.this") ReferenceEntry nextEvictable = nullEntry(); @Override public ReferenceEntry getNextEvictable() { return nextEvictable; } @Override public void setNextEvictable(ReferenceEntry next) { this.nextEvictable = next; } @GuardedBy("Segment.this") ReferenceEntry previousEvictable = nullEntry(); @Override public ReferenceEntry getPreviousEvictable() { return previousEvictable; } @Override public void setPreviousEvictable(ReferenceEntry previous) { this.previousEvictable = previous; } } /** * References a weak value. */ static final class WeakValueReference extends WeakReference implements ValueReference { final ReferenceEntry entry; WeakValueReference(ReferenceQueue queue, V referent, ReferenceEntry entry) { super(referent, queue); this.entry = entry; } @Override public ReferenceEntry getEntry() { return entry; } @Override public void clear(ValueReference newValue) { clear(); } @Override public ValueReference copyFor( ReferenceQueue queue, V value, ReferenceEntry entry) { return new WeakValueReference(queue, value, entry); } @Override public boolean isComputingReference() { return false; } @Override public V waitForValue() { return get(); } } /** * References a soft value. */ static final class SoftValueReference extends SoftReference implements ValueReference { final ReferenceEntry entry; SoftValueReference(ReferenceQueue queue, V referent, ReferenceEntry entry) { super(referent, queue); this.entry = entry; } @Override public ReferenceEntry getEntry() { return entry; } @Override public void clear(ValueReference newValue) { clear(); } @Override public ValueReference copyFor( ReferenceQueue queue, V value, ReferenceEntry entry) { return new SoftValueReference(queue, value, entry); } @Override public boolean isComputingReference() { return false; } @Override public V waitForValue() { return get(); } } /** * References a strong value. */ static final class StrongValueReference implements ValueReference { final V referent; StrongValueReference(V referent) { this.referent = referent; } @Override public V get() { return referent; } @Override public ReferenceEntry getEntry() { return null; } @Override public ValueReference copyFor( ReferenceQueue queue, V value, ReferenceEntry entry) { return this; } @Override public boolean isComputingReference() { return false; } @Override public V waitForValue() { return get(); } @Override public void clear(ValueReference newValue) {} } /** * Applies a supplemental hash function to a given hash code, which defends against poor quality * hash functions. This is critical when the concurrent hash map uses power-of-two length hash * tables, that otherwise encounter collisions for hash codes that do not differ in lower or * upper bits. * * @param h hash code */ static int rehash(int h) { // Spread bits to regularize both segment and index locations, // using variant of single-word Wang/Jenkins hash. // TODO(kevinb): use Hashing/move this to Hashing? h += (h << 15) ^ 0xffffcd7d; h ^= (h >>> 10); h += (h << 3); h ^= (h >>> 6); h += (h << 2) + (h << 14); return h ^ (h >>> 16); } /** * This method is a convenience for testing. Code should call {@link Segment#newEntry} directly. */ @GuardedBy("Segment.this") @VisibleForTesting ReferenceEntry newEntry(K key, int hash, @Nullable ReferenceEntry next) { return segmentFor(hash).newEntry(key, hash, next); } /** * This method is a convenience for testing. Code should call {@link Segment#copyEntry} directly. */ @GuardedBy("Segment.this") @VisibleForTesting ReferenceEntry copyEntry(ReferenceEntry original, ReferenceEntry newNext) { int hash = original.getHash(); return segmentFor(hash).copyEntry(original, newNext); } /** * This method is a convenience for testing. Code should call {@link Segment#setValue} instead. */ @GuardedBy("Segment.this") @VisibleForTesting ValueReference newValueReference(ReferenceEntry entry, V value) { int hash = entry.getHash(); return valueStrength.referenceValue(segmentFor(hash), entry, value); } int hash(Object key) { int h = keyEquivalence.hash(key); return rehash(h); } void reclaimValue(ValueReference valueReference) { ReferenceEntry entry = valueReference.getEntry(); int hash = entry.getHash(); segmentFor(hash).reclaimValue(entry.getKey(), hash, valueReference); } void reclaimKey(ReferenceEntry entry) { int hash = entry.getHash(); segmentFor(hash).reclaimKey(entry, hash); } /** * This method is a convenience for testing. Code should call {@link Segment#getLiveValue} * instead. */ @VisibleForTesting boolean isLive(ReferenceEntry entry) { return segmentFor(entry.getHash()).getLiveValue(entry) != null; } /** * Returns the segment that should be used for a key with the given hash. * * @param hash the hash code for the key * @return the segment */ Segment segmentFor(int hash) { // TODO(fry): Lazily create segments? return segments[(hash >>> segmentShift) & segmentMask]; } Segment createSegment(int initialCapacity, int maxSegmentSize) { return new Segment(this, initialCapacity, maxSegmentSize); } /** * Gets the value from an entry. Returns {@code null} if the entry is invalid, * partially-collected, computing, or expired. Unlike {@link Segment#getLiveValue} this method * does not attempt to clean up stale entries. */ V getLiveValue(ReferenceEntry entry) { if (entry.getKey() == null) { return null; } V value = entry.getValueReference().get(); if (value == null) { return null; } if (expires() && isExpired(entry)) { return null; } return value; } // expiration /** * Returns {@code true} if the entry has expired. */ boolean isExpired(ReferenceEntry entry) { return isExpired(entry, ticker.read()); } /** * Returns {@code true} if the entry has expired. */ boolean isExpired(ReferenceEntry entry, long now) { // if the expiration time had overflowed, this "undoes" the overflow return now - entry.getExpirationTime() > 0; } @GuardedBy("Segment.this") static void connectExpirables(ReferenceEntry previous, ReferenceEntry next) { previous.setNextExpirable(next); next.setPreviousExpirable(previous); } @GuardedBy("Segment.this") static void nullifyExpirable(ReferenceEntry nulled) { ReferenceEntry nullEntry = nullEntry(); nulled.setNextExpirable(nullEntry); nulled.setPreviousExpirable(nullEntry); } // eviction /** * Notifies listeners that an entry has been automatically removed due to expiration, eviction, * or eligibility for garbage collection. This should be called every time expireEntries or * evictEntry is called (once the lock is released). */ void processPendingNotifications() { RemovalNotification notification; while ((notification = removalNotificationQueue.poll()) != null) { try { removalListener.onRemoval(notification); } catch (Exception e) { logger.log(Level.WARNING, "Exception thrown by removal listener", e); } } } /** Links the evitables together. */ @GuardedBy("Segment.this") static void connectEvictables(ReferenceEntry previous, ReferenceEntry next) { previous.setNextEvictable(next); next.setPreviousEvictable(previous); } @GuardedBy("Segment.this") static void nullifyEvictable(ReferenceEntry nulled) { ReferenceEntry nullEntry = nullEntry(); nulled.setNextEvictable(nullEntry); nulled.setPreviousEvictable(nullEntry); } @SuppressWarnings("unchecked") final Segment[] newSegmentArray(int ssize) { return new Segment[ssize]; } // Inner Classes /** * Segments are specialized versions of hash tables. This subclass inherits from ReentrantLock * opportunistically, just to simplify some locking and avoid separate construction. */ @SuppressWarnings("serial") // This class is never serialized. static class Segment extends ReentrantLock { /* * TODO(fry): Consider copying variables (like evictsBySize) from outer class into this class. * It will require more memory but will reduce indirection. */ /* * Segments maintain a table of entry lists that are ALWAYS kept in a consistent state, so can * be read without locking. Next fields of nodes are immutable (final). All list additions are * performed at the front of each bin. This makes it easy to check changes, and also fast to * traverse. When nodes would otherwise be changed, new nodes are created to replace them. This * works well for hash tables since the bin lists tend to be short. (The average length is less * than two.) * * Read operations can thus proceed without locking, but rely on selected uses of volatiles to * ensure that completed write operations performed by other threads are noticed. For most * purposes, the "count" field, tracking the number of elements, serves as that volatile * variable ensuring visibility. This is convenient because this field needs to be read in many * read operations anyway: * * - All (unsynchronized) read operations must first read the "count" field, and should not * look at table entries if it is 0. * * - All (synchronized) write operations should write to the "count" field after structurally * changing any bin. The operations must not take any action that could even momentarily * cause a concurrent read operation to see inconsistent data. This is made easier by the * nature of the read operations in Map. For example, no operation can reveal that the table * has grown but the threshold has not yet been updated, so there are no atomicity requirements * for this with respect to reads. * * As a guide, all critical volatile reads and writes to the count field are marked in code * comments. */ final MapMakerInternalMap map; /** * The number of live elements in this segment's region. This does not include unset elements * which are awaiting cleanup. */ volatile int count; /** * Number of updates that alter the size of the table. This is used during bulk-read methods to * make sure they see a consistent snapshot: If modCounts change during a traversal of segments * computing size or checking containsValue, then we might have an inconsistent view of state * so (usually) must retry. */ int modCount; /** * The table is expanded when its size exceeds this threshold. (The value of this field is * always {@code (int)(capacity * 0.75)}.) */ int threshold; /** * The per-segment table. */ volatile AtomicReferenceArray> table; /** * The maximum size of this map. MapMaker.UNSET_INT if there is no maximum. */ final int maxSegmentSize; /** * The key reference queue contains entries whose keys have been garbage collected, and which * need to be cleaned up internally. */ final ReferenceQueue keyReferenceQueue; /** * The value reference queue contains value references whose values have been garbage collected, * and which need to be cleaned up internally. */ final ReferenceQueue valueReferenceQueue; /** * The recency queue is used to record which entries were accessed for updating the eviction * list's ordering. It is drained as a batch operation when either the DRAIN_THRESHOLD is * crossed or a write occurs on the segment. */ final Queue> recencyQueue; /** * A counter of the number of reads since the last write, used to drain queues on a small * fraction of read operations. */ final AtomicInteger readCount = new AtomicInteger(); /** * A queue of elements currently in the map, ordered by access time. Elements are added to the * tail of the queue on access/write. */ @GuardedBy("Segment.this") final Queue> evictionQueue; /** * A queue of elements currently in the map, ordered by expiration time (either access or write * time). Elements are added to the tail of the queue on access/write. */ @GuardedBy("Segment.this") final Queue> expirationQueue; Segment(MapMakerInternalMap map, int initialCapacity, int maxSegmentSize) { this.map = map; this.maxSegmentSize = maxSegmentSize; initTable(newEntryArray(initialCapacity)); keyReferenceQueue = map.usesKeyReferences() ? new ReferenceQueue() : null; valueReferenceQueue = map.usesValueReferences() ? new ReferenceQueue() : null; recencyQueue = (map.evictsBySize() || map.expiresAfterAccess()) ? new ConcurrentLinkedQueue>() : MapMakerInternalMap.>discardingQueue(); evictionQueue = map.evictsBySize() ? new EvictionQueue() : MapMakerInternalMap.>discardingQueue(); expirationQueue = map.expires() ? new ExpirationQueue() : MapMakerInternalMap.>discardingQueue(); } AtomicReferenceArray> newEntryArray(int size) { return new AtomicReferenceArray>(size); } void initTable(AtomicReferenceArray> newTable) { this.threshold = newTable.length() * 3 / 4; // 0.75 if (this.threshold == maxSegmentSize) { // prevent spurious expansion before eviction this.threshold++; } this.table = newTable; } @GuardedBy("Segment.this") ReferenceEntry newEntry(K key, int hash, @Nullable ReferenceEntry next) { return map.entryFactory.newEntry(this, key, hash, next); } /** * Copies {@code original} into a new entry chained to {@code newNext}. Returns the new entry, * or {@code null} if {@code original} was already garbage collected. */ @GuardedBy("Segment.this") ReferenceEntry copyEntry(ReferenceEntry original, ReferenceEntry newNext) { if (original.getKey() == null) { // key collected return null; } ValueReference valueReference = original.getValueReference(); V value = valueReference.get(); if ((value == null) && !valueReference.isComputingReference()) { // value collected return null; } ReferenceEntry newEntry = map.entryFactory.copyEntry(this, original, newNext); newEntry.setValueReference(valueReference.copyFor(this.valueReferenceQueue, value, newEntry)); return newEntry; } /** * Sets a new value of an entry. Adds newly created entries at the end of the expiration queue. */ @GuardedBy("Segment.this") void setValue(ReferenceEntry entry, V value) { ValueReference valueReference = map.valueStrength.referenceValue(this, entry, value); entry.setValueReference(valueReference); recordWrite(entry); } // reference queues, for garbage collection cleanup /** * Cleanup collected entries when the lock is available. */ void tryDrainReferenceQueues() { if (tryLock()) { try { drainReferenceQueues(); } finally { unlock(); } } } /** * Drain the key and value reference queues, cleaning up internal entries containing garbage * collected keys or values. */ @GuardedBy("Segment.this") void drainReferenceQueues() { if (map.usesKeyReferences()) { drainKeyReferenceQueue(); } if (map.usesValueReferences()) { drainValueReferenceQueue(); } } @GuardedBy("Segment.this") void drainKeyReferenceQueue() { Reference ref; int i = 0; while ((ref = keyReferenceQueue.poll()) != null) { @SuppressWarnings("unchecked") ReferenceEntry entry = (ReferenceEntry) ref; map.reclaimKey(entry); if (++i == DRAIN_MAX) { break; } } } @GuardedBy("Segment.this") void drainValueReferenceQueue() { Reference ref; int i = 0; while ((ref = valueReferenceQueue.poll()) != null) { @SuppressWarnings("unchecked") ValueReference valueReference = (ValueReference) ref; map.reclaimValue(valueReference); if (++i == DRAIN_MAX) { break; } } } /** * Clears all entries from the key and value reference queues. */ void clearReferenceQueues() { if (map.usesKeyReferences()) { clearKeyReferenceQueue(); } if (map.usesValueReferences()) { clearValueReferenceQueue(); } } void clearKeyReferenceQueue() { while (keyReferenceQueue.poll() != null) {} } void clearValueReferenceQueue() { while (valueReferenceQueue.poll() != null) {} } // recency queue, shared by expiration and eviction /** * Records the relative order in which this read was performed by adding {@code entry} to the * recency queue. At write-time, or when the queue is full past the threshold, the queue will * be drained and the entries therein processed. * *

Note: locked reads should use {@link #recordLockedRead}. */ void recordRead(ReferenceEntry entry) { if (map.expiresAfterAccess()) { recordExpirationTime(entry, map.expireAfterAccessNanos); } recencyQueue.add(entry); } /** * Updates the eviction metadata that {@code entry} was just read. This currently amounts to * adding {@code entry} to relevant eviction lists. * *

Note: this method should only be called under lock, as it directly manipulates the * eviction queues. Unlocked reads should use {@link #recordRead}. */ @GuardedBy("Segment.this") void recordLockedRead(ReferenceEntry entry) { evictionQueue.add(entry); if (map.expiresAfterAccess()) { recordExpirationTime(entry, map.expireAfterAccessNanos); expirationQueue.add(entry); } } /** * Updates eviction metadata that {@code entry} was just written. This currently amounts to * adding {@code entry} to relevant eviction lists. */ @GuardedBy("Segment.this") void recordWrite(ReferenceEntry entry) { // we are already under lock, so drain the recency queue immediately drainRecencyQueue(); evictionQueue.add(entry); if (map.expires()) { // currently MapMaker ensures that expireAfterWrite and // expireAfterAccess are mutually exclusive long expiration = map.expiresAfterAccess() ? map.expireAfterAccessNanos : map.expireAfterWriteNanos; recordExpirationTime(entry, expiration); expirationQueue.add(entry); } } /** * Drains the recency queue, updating eviction metadata that the entries therein were read in * the specified relative order. This currently amounts to adding them to relevant eviction * lists (accounting for the fact that they could have been removed from the map since being * added to the recency queue). */ @GuardedBy("Segment.this") void drainRecencyQueue() { ReferenceEntry e; while ((e = recencyQueue.poll()) != null) { // An entry may be in the recency queue despite it being removed from // the map . This can occur when the entry was concurrently read while a // writer is removing it from the segment or after a clear has removed // all of the segment's entries. if (evictionQueue.contains(e)) { evictionQueue.add(e); } if (map.expiresAfterAccess() && expirationQueue.contains(e)) { expirationQueue.add(e); } } } // expiration void recordExpirationTime(ReferenceEntry entry, long expirationNanos) { // might overflow, but that's okay (see isExpired()) entry.setExpirationTime(map.ticker.read() + expirationNanos); } /** * Cleanup expired entries when the lock is available. */ void tryExpireEntries() { if (tryLock()) { try { expireEntries(); } finally { unlock(); // don't call postWriteCleanup as we're in a read } } } @GuardedBy("Segment.this") void expireEntries() { drainRecencyQueue(); if (expirationQueue.isEmpty()) { // There's no point in calling nanoTime() if we have no entries to // expire. return; } long now = map.ticker.read(); ReferenceEntry e; while ((e = expirationQueue.peek()) != null && map.isExpired(e, now)) { if (!removeEntry(e, e.getHash(), RemovalCause.EXPIRED)) { throw new AssertionError(); } } } // eviction void enqueueNotification(ReferenceEntry entry, RemovalCause cause) { enqueueNotification(entry.getKey(), entry.getHash(), entry.getValueReference().get(), cause); } void enqueueNotification(@Nullable K key, int hash, @Nullable V value, RemovalCause cause) { if (map.removalNotificationQueue != DISCARDING_QUEUE) { RemovalNotification notification = new RemovalNotification(key, value, cause); map.removalNotificationQueue.offer(notification); } } /** * Performs eviction if the segment is full. This should only be called prior to adding a new * entry and increasing {@code count}. * * @return {@code true} if eviction occurred */ @GuardedBy("Segment.this") boolean evictEntries() { if (map.evictsBySize() && count >= maxSegmentSize) { drainRecencyQueue(); ReferenceEntry e = evictionQueue.remove(); if (!removeEntry(e, e.getHash(), RemovalCause.SIZE)) { throw new AssertionError(); } return true; } return false; } /** * Returns first entry of bin for given hash. */ ReferenceEntry getFirst(int hash) { // read this volatile field only once AtomicReferenceArray> table = this.table; return table.get(hash & (table.length() - 1)); } // Specialized implementations of map methods ReferenceEntry getEntry(Object key, int hash) { if (count != 0) { // read-volatile for (ReferenceEntry e = getFirst(hash); e != null; e = e.getNext()) { if (e.getHash() != hash) { continue; } K entryKey = e.getKey(); if (entryKey == null) { tryDrainReferenceQueues(); continue; } if (map.keyEquivalence.equivalent(key, entryKey)) { return e; } } } return null; } ReferenceEntry getLiveEntry(Object key, int hash) { ReferenceEntry e = getEntry(key, hash); if (e == null) { return null; } else if (map.expires() && map.isExpired(e)) { tryExpireEntries(); return null; } return e; } V get(Object key, int hash) { try { ReferenceEntry e = getLiveEntry(key, hash); if (e == null) { return null; } V value = e.getValueReference().get(); if (value != null) { recordRead(e); } else { tryDrainReferenceQueues(); } return value; } finally { postReadCleanup(); } } boolean containsKey(Object key, int hash) { try { if (count != 0) { // read-volatile ReferenceEntry e = getLiveEntry(key, hash); if (e == null) { return false; } return e.getValueReference().get() != null; } return false; } finally { postReadCleanup(); } } /** * This method is a convenience for testing. Code should call {@link * MapMakerInternalMap#containsValue} directly. */ @VisibleForTesting boolean containsValue(Object value) { try { if (count != 0) { // read-volatile AtomicReferenceArray> table = this.table; int length = table.length(); for (int i = 0; i < length; ++i) { for (ReferenceEntry e = table.get(i); e != null; e = e.getNext()) { V entryValue = getLiveValue(e); if (entryValue == null) { continue; } if (map.valueEquivalence.equivalent(value, entryValue)) { return true; } } } } return false; } finally { postReadCleanup(); } } V put(K key, int hash, V value, boolean onlyIfAbsent) { lock(); try { preWriteCleanup(); int newCount = this.count + 1; if (newCount > this.threshold) { // ensure capacity expand(); newCount = this.count + 1; } AtomicReferenceArray> table = this.table; int index = hash & (table.length() - 1); ReferenceEntry first = table.get(index); // Look for an existing entry. for (ReferenceEntry e = first; e != null; e = e.getNext()) { K entryKey = e.getKey(); if (e.getHash() == hash && entryKey != null && map.keyEquivalence.equivalent(key, entryKey)) { // We found an existing entry. ValueReference valueReference = e.getValueReference(); V entryValue = valueReference.get(); if (entryValue == null) { ++modCount; setValue(e, value); if (!valueReference.isComputingReference()) { enqueueNotification(key, hash, entryValue, RemovalCause.COLLECTED); newCount = this.count; // count remains unchanged } else if (evictEntries()) { // evictEntries after setting new value newCount = this.count + 1; } this.count = newCount; // write-volatile return null; } else if (onlyIfAbsent) { // Mimic // "if (!map.containsKey(key)) ... // else return map.get(key); recordLockedRead(e); return entryValue; } else { // clobber existing entry, count remains unchanged ++modCount; enqueueNotification(key, hash, entryValue, RemovalCause.REPLACED); setValue(e, value); return entryValue; } } } // Create a new entry. ++modCount; ReferenceEntry newEntry = newEntry(key, hash, first); setValue(newEntry, value); table.set(index, newEntry); if (evictEntries()) { // evictEntries after setting new value newCount = this.count + 1; } this.count = newCount; // write-volatile return null; } finally { unlock(); postWriteCleanup(); } } /** * Expands the table if possible. */ @GuardedBy("Segment.this") void expand() { AtomicReferenceArray> oldTable = table; int oldCapacity = oldTable.length(); if (oldCapacity >= MAXIMUM_CAPACITY) { return; } /* * Reclassify nodes in each list to new Map. Because we are using power-of-two expansion, the * elements from each bin must either stay at same index, or move with a power of two offset. * We eliminate unnecessary node creation by catching cases where old nodes can be reused * because their next fields won't change. Statistically, at the default threshold, only * about one-sixth of them need cloning when a table doubles. The nodes they replace will be * garbage collectable as soon as they are no longer referenced by any reader thread that may * be in the midst of traversing table right now. */ int newCount = count; AtomicReferenceArray> newTable = newEntryArray(oldCapacity << 1); threshold = newTable.length() * 3 / 4; int newMask = newTable.length() - 1; for (int oldIndex = 0; oldIndex < oldCapacity; ++oldIndex) { // We need to guarantee that any existing reads of old Map can // proceed. So we cannot yet null out each bin. ReferenceEntry head = oldTable.get(oldIndex); if (head != null) { ReferenceEntry next = head.getNext(); int headIndex = head.getHash() & newMask; // Single node on list if (next == null) { newTable.set(headIndex, head); } else { // Reuse the consecutive sequence of nodes with the same target // index from the end of the list. tail points to the first // entry in the reusable list. ReferenceEntry tail = head; int tailIndex = headIndex; for (ReferenceEntry e = next; e != null; e = e.getNext()) { int newIndex = e.getHash() & newMask; if (newIndex != tailIndex) { // The index changed. We'll need to copy the previous entry. tailIndex = newIndex; tail = e; } } newTable.set(tailIndex, tail); // Clone nodes leading up to the tail. for (ReferenceEntry e = head; e != tail; e = e.getNext()) { int newIndex = e.getHash() & newMask; ReferenceEntry newNext = newTable.get(newIndex); ReferenceEntry newFirst = copyEntry(e, newNext); if (newFirst != null) { newTable.set(newIndex, newFirst); } else { removeCollectedEntry(e); newCount--; } } } } } table = newTable; this.count = newCount; } boolean replace(K key, int hash, V oldValue, V newValue) { lock(); try { preWriteCleanup(); AtomicReferenceArray> table = this.table; int index = hash & (table.length() - 1); ReferenceEntry first = table.get(index); for (ReferenceEntry e = first; e != null; e = e.getNext()) { K entryKey = e.getKey(); if (e.getHash() == hash && entryKey != null && map.keyEquivalence.equivalent(key, entryKey)) { // If the value disappeared, this entry is partially collected, // and we should pretend like it doesn't exist. ValueReference valueReference = e.getValueReference(); V entryValue = valueReference.get(); if (entryValue == null) { if (isCollected(valueReference)) { int newCount = this.count - 1; ++modCount; enqueueNotification(entryKey, hash, entryValue, RemovalCause.COLLECTED); ReferenceEntry newFirst = removeFromChain(first, e); newCount = this.count - 1; table.set(index, newFirst); this.count = newCount; // write-volatile } return false; } if (map.valueEquivalence.equivalent(oldValue, entryValue)) { ++modCount; enqueueNotification(key, hash, entryValue, RemovalCause.REPLACED); setValue(e, newValue); return true; } else { // Mimic // "if (map.containsKey(key) && map.get(key).equals(oldValue))..." recordLockedRead(e); return false; } } } return false; } finally { unlock(); postWriteCleanup(); } } V replace(K key, int hash, V newValue) { lock(); try { preWriteCleanup(); AtomicReferenceArray> table = this.table; int index = hash & (table.length() - 1); ReferenceEntry first = table.get(index); for (ReferenceEntry e = first; e != null; e = e.getNext()) { K entryKey = e.getKey(); if (e.getHash() == hash && entryKey != null && map.keyEquivalence.equivalent(key, entryKey)) { // If the value disappeared, this entry is partially collected, // and we should pretend like it doesn't exist. ValueReference valueReference = e.getValueReference(); V entryValue = valueReference.get(); if (entryValue == null) { if (isCollected(valueReference)) { int newCount = this.count - 1; ++modCount; enqueueNotification(entryKey, hash, entryValue, RemovalCause.COLLECTED); ReferenceEntry newFirst = removeFromChain(first, e); newCount = this.count - 1; table.set(index, newFirst); this.count = newCount; // write-volatile } return null; } ++modCount; enqueueNotification(key, hash, entryValue, RemovalCause.REPLACED); setValue(e, newValue); return entryValue; } } return null; } finally { unlock(); postWriteCleanup(); } } V remove(Object key, int hash) { lock(); try { preWriteCleanup(); int newCount = this.count - 1; AtomicReferenceArray> table = this.table; int index = hash & (table.length() - 1); ReferenceEntry first = table.get(index); for (ReferenceEntry e = first; e != null; e = e.getNext()) { K entryKey = e.getKey(); if (e.getHash() == hash && entryKey != null && map.keyEquivalence.equivalent(key, entryKey)) { ValueReference valueReference = e.getValueReference(); V entryValue = valueReference.get(); RemovalCause cause; if (entryValue != null) { cause = RemovalCause.EXPLICIT; } else if (isCollected(valueReference)) { cause = RemovalCause.COLLECTED; } else { return null; } ++modCount; enqueueNotification(entryKey, hash, entryValue, cause); ReferenceEntry newFirst = removeFromChain(first, e); newCount = this.count - 1; table.set(index, newFirst); this.count = newCount; // write-volatile return entryValue; } } return null; } finally { unlock(); postWriteCleanup(); } } boolean remove(Object key, int hash, Object value) { lock(); try { preWriteCleanup(); int newCount = this.count - 1; AtomicReferenceArray> table = this.table; int index = hash & (table.length() - 1); ReferenceEntry first = table.get(index); for (ReferenceEntry e = first; e != null; e = e.getNext()) { K entryKey = e.getKey(); if (e.getHash() == hash && entryKey != null && map.keyEquivalence.equivalent(key, entryKey)) { ValueReference valueReference = e.getValueReference(); V entryValue = valueReference.get(); RemovalCause cause; if (map.valueEquivalence.equivalent(value, entryValue)) { cause = RemovalCause.EXPLICIT; } else if (isCollected(valueReference)) { cause = RemovalCause.COLLECTED; } else { return false; } ++modCount; enqueueNotification(entryKey, hash, entryValue, cause); ReferenceEntry newFirst = removeFromChain(first, e); newCount = this.count - 1; table.set(index, newFirst); this.count = newCount; // write-volatile return (cause == RemovalCause.EXPLICIT); } } return false; } finally { unlock(); postWriteCleanup(); } } void clear() { if (count != 0) { lock(); try { AtomicReferenceArray> table = this.table; if (map.removalNotificationQueue != DISCARDING_QUEUE) { for (int i = 0; i < table.length(); ++i) { for (ReferenceEntry e = table.get(i); e != null; e = e.getNext()) { // Computing references aren't actually in the map yet. if (!e.getValueReference().isComputingReference()) { enqueueNotification(e, RemovalCause.EXPLICIT); } } } } for (int i = 0; i < table.length(); ++i) { table.set(i, null); } clearReferenceQueues(); evictionQueue.clear(); expirationQueue.clear(); readCount.set(0); ++modCount; count = 0; // write-volatile } finally { unlock(); postWriteCleanup(); } } } /** * Removes an entry from within a table. All entries following the removed node can stay, but * all preceding ones need to be cloned. * *

This method does not decrement count for the removed entry, but does decrement count for * all partially collected entries which are skipped. As such callers which are modifying count * must re-read it after calling removeFromChain. * * @param first the first entry of the table * @param entry the entry being removed from the table * @return the new first entry for the table */ @GuardedBy("Segment.this") ReferenceEntry removeFromChain(ReferenceEntry first, ReferenceEntry entry) { evictionQueue.remove(entry); expirationQueue.remove(entry); int newCount = count; ReferenceEntry newFirst = entry.getNext(); for (ReferenceEntry e = first; e != entry; e = e.getNext()) { ReferenceEntry next = copyEntry(e, newFirst); if (next != null) { newFirst = next; } else { removeCollectedEntry(e); newCount--; } } this.count = newCount; return newFirst; } void removeCollectedEntry(ReferenceEntry entry) { enqueueNotification(entry, RemovalCause.COLLECTED); evictionQueue.remove(entry); expirationQueue.remove(entry); } /** * Removes an entry whose key has been garbage collected. */ boolean reclaimKey(ReferenceEntry entry, int hash) { lock(); try { int newCount = count - 1; AtomicReferenceArray> table = this.table; int index = hash & (table.length() - 1); ReferenceEntry first = table.get(index); for (ReferenceEntry e = first; e != null; e = e.getNext()) { if (e == entry) { ++modCount; enqueueNotification( e.getKey(), hash, e.getValueReference().get(), RemovalCause.COLLECTED); ReferenceEntry newFirst = removeFromChain(first, e); newCount = this.count - 1; table.set(index, newFirst); this.count = newCount; // write-volatile return true; } } return false; } finally { unlock(); postWriteCleanup(); } } /** * Removes an entry whose value has been garbage collected. */ boolean reclaimValue(K key, int hash, ValueReference valueReference) { lock(); try { int newCount = this.count - 1; AtomicReferenceArray> table = this.table; int index = hash & (table.length() - 1); ReferenceEntry first = table.get(index); for (ReferenceEntry e = first; e != null; e = e.getNext()) { K entryKey = e.getKey(); if (e.getHash() == hash && entryKey != null && map.keyEquivalence.equivalent(key, entryKey)) { ValueReference v = e.getValueReference(); if (v == valueReference) { ++modCount; enqueueNotification(key, hash, valueReference.get(), RemovalCause.COLLECTED); ReferenceEntry newFirst = removeFromChain(first, e); newCount = this.count - 1; table.set(index, newFirst); this.count = newCount; // write-volatile return true; } return false; } } return false; } finally { unlock(); if (!isHeldByCurrentThread()) { // don't cleanup inside of put postWriteCleanup(); } } } /** * Clears a value that has not yet been set, and thus does not require count to be modified. */ boolean clearValue(K key, int hash, ValueReference valueReference) { lock(); try { AtomicReferenceArray> table = this.table; int index = hash & (table.length() - 1); ReferenceEntry first = table.get(index); for (ReferenceEntry e = first; e != null; e = e.getNext()) { K entryKey = e.getKey(); if (e.getHash() == hash && entryKey != null && map.keyEquivalence.equivalent(key, entryKey)) { ValueReference v = e.getValueReference(); if (v == valueReference) { ReferenceEntry newFirst = removeFromChain(first, e); table.set(index, newFirst); return true; } return false; } } return false; } finally { unlock(); postWriteCleanup(); } } @GuardedBy("Segment.this") boolean removeEntry(ReferenceEntry entry, int hash, RemovalCause cause) { int newCount = this.count - 1; AtomicReferenceArray> table = this.table; int index = hash & (table.length() - 1); ReferenceEntry first = table.get(index); for (ReferenceEntry e = first; e != null; e = e.getNext()) { if (e == entry) { ++modCount; enqueueNotification(e.getKey(), hash, e.getValueReference().get(), cause); ReferenceEntry newFirst = removeFromChain(first, e); newCount = this.count - 1; table.set(index, newFirst); this.count = newCount; // write-volatile return true; } } return false; } /** * Returns {@code true} if the value has been partially collected, meaning that the value is * null and it is not computing. */ boolean isCollected(ValueReference valueReference) { if (valueReference.isComputingReference()) { return false; } return (valueReference.get() == null); } /** * Gets the value from an entry. Returns {@code null} if the entry is invalid, * partially-collected, computing, or expired. */ V getLiveValue(ReferenceEntry entry) { if (entry.getKey() == null) { tryDrainReferenceQueues(); return null; } V value = entry.getValueReference().get(); if (value == null) { tryDrainReferenceQueues(); return null; } if (map.expires() && map.isExpired(entry)) { tryExpireEntries(); return null; } return value; } /** * Performs routine cleanup following a read. Normally cleanup happens during writes, or from * the cleanupExecutor. If cleanup is not observed after a sufficient number of reads, try * cleaning up from the read thread. */ void postReadCleanup() { if ((readCount.incrementAndGet() & DRAIN_THRESHOLD) == 0) { runCleanup(); } } /** * Performs routine cleanup prior to executing a write. This should be called every time a * write thread acquires the segment lock, immediately after acquiring the lock. * *

Post-condition: expireEntries has been run. */ @GuardedBy("Segment.this") void preWriteCleanup() { runLockedCleanup(); } /** * Performs routine cleanup following a write. */ void postWriteCleanup() { runUnlockedCleanup(); } void runCleanup() { runLockedCleanup(); runUnlockedCleanup(); } void runLockedCleanup() { if (tryLock()) { try { drainReferenceQueues(); expireEntries(); // calls drainRecencyQueue readCount.set(0); } finally { unlock(); } } } void runUnlockedCleanup() { // locked cleanup may generate notifications we can send unlocked if (!isHeldByCurrentThread()) { map.processPendingNotifications(); } } } // Queues /** * A custom queue for managing eviction order. Note that this is tightly integrated with {@code * ReferenceEntry}, upon which it relies to perform its linking. * *

Note that this entire implementation makes the assumption that all elements which are in * the map are also in this queue, and that all elements not in the queue are not in the map. * *

The benefits of creating our own queue are that (1) we can replace elements in the middle * of the queue as part of copyEvictableEntry, and (2) the contains method is highly optimized * for the current model. */ static final class EvictionQueue extends AbstractQueue> { final ReferenceEntry head = new AbstractReferenceEntry() { ReferenceEntry nextEvictable = this; @Override public ReferenceEntry getNextEvictable() { return nextEvictable; } @Override public void setNextEvictable(ReferenceEntry next) { this.nextEvictable = next; } ReferenceEntry previousEvictable = this; @Override public ReferenceEntry getPreviousEvictable() { return previousEvictable; } @Override public void setPreviousEvictable(ReferenceEntry previous) { this.previousEvictable = previous; } }; // implements Queue @Override public boolean offer(ReferenceEntry entry) { // unlink connectEvictables(entry.getPreviousEvictable(), entry.getNextEvictable()); // add to tail connectEvictables(head.getPreviousEvictable(), entry); connectEvictables(entry, head); return true; } @Override public ReferenceEntry peek() { ReferenceEntry next = head.getNextEvictable(); return (next == head) ? null : next; } @Override public ReferenceEntry poll() { ReferenceEntry next = head.getNextEvictable(); if (next == head) { return null; } remove(next); return next; } @Override @SuppressWarnings("unchecked") public boolean remove(Object o) { ReferenceEntry e = (ReferenceEntry) o; ReferenceEntry previous = e.getPreviousEvictable(); ReferenceEntry next = e.getNextEvictable(); connectEvictables(previous, next); nullifyEvictable(e); return next != NullEntry.INSTANCE; } @Override @SuppressWarnings("unchecked") public boolean contains(Object o) { ReferenceEntry e = (ReferenceEntry) o; return e.getNextEvictable() != NullEntry.INSTANCE; } @Override public boolean isEmpty() { return head.getNextEvictable() == head; } @Override public int size() { int size = 0; for (ReferenceEntry e = head.getNextEvictable(); e != head; e = e.getNextEvictable()) { size++; } return size; } @Override public void clear() { ReferenceEntry e = head.getNextEvictable(); while (e != head) { ReferenceEntry next = e.getNextEvictable(); nullifyEvictable(e); e = next; } head.setNextEvictable(head); head.setPreviousEvictable(head); } @Override public Iterator> iterator() { return new AbstractSequentialIterator>(peek()) { @Override protected ReferenceEntry computeNext(ReferenceEntry previous) { ReferenceEntry next = previous.getNextEvictable(); return (next == head) ? null : next; } }; } } /** * A custom queue for managing expiration order. Note that this is tightly integrated with * {@code ReferenceEntry}, upon which it reliese to perform its linking. * *

Note that this entire implementation makes the assumption that all elements which are in * the map are also in this queue, and that all elements not in the queue are not in the map. * *

The benefits of creating our own queue are that (1) we can replace elements in the middle * of the queue as part of copyEvictableEntry, and (2) the contains method is highly optimized * for the current model. */ static final class ExpirationQueue extends AbstractQueue> { final ReferenceEntry head = new AbstractReferenceEntry() { @Override public long getExpirationTime() { return Long.MAX_VALUE; } @Override public void setExpirationTime(long time) {} ReferenceEntry nextExpirable = this; @Override public ReferenceEntry getNextExpirable() { return nextExpirable; } @Override public void setNextExpirable(ReferenceEntry next) { this.nextExpirable = next; } ReferenceEntry previousExpirable = this; @Override public ReferenceEntry getPreviousExpirable() { return previousExpirable; } @Override public void setPreviousExpirable(ReferenceEntry previous) { this.previousExpirable = previous; } }; // implements Queue @Override public boolean offer(ReferenceEntry entry) { // unlink connectExpirables(entry.getPreviousExpirable(), entry.getNextExpirable()); // add to tail connectExpirables(head.getPreviousExpirable(), entry); connectExpirables(entry, head); return true; } @Override public ReferenceEntry peek() { ReferenceEntry next = head.getNextExpirable(); return (next == head) ? null : next; } @Override public ReferenceEntry poll() { ReferenceEntry next = head.getNextExpirable(); if (next == head) { return null; } remove(next); return next; } @Override @SuppressWarnings("unchecked") public boolean remove(Object o) { ReferenceEntry e = (ReferenceEntry) o; ReferenceEntry previous = e.getPreviousExpirable(); ReferenceEntry next = e.getNextExpirable(); connectExpirables(previous, next); nullifyExpirable(e); return next != NullEntry.INSTANCE; } @Override @SuppressWarnings("unchecked") public boolean contains(Object o) { ReferenceEntry e = (ReferenceEntry) o; return e.getNextExpirable() != NullEntry.INSTANCE; } @Override public boolean isEmpty() { return head.getNextExpirable() == head; } @Override public int size() { int size = 0; for (ReferenceEntry e = head.getNextExpirable(); e != head; e = e.getNextExpirable()) { size++; } return size; } @Override public void clear() { ReferenceEntry e = head.getNextExpirable(); while (e != head) { ReferenceEntry next = e.getNextExpirable(); nullifyExpirable(e); e = next; } head.setNextExpirable(head); head.setPreviousExpirable(head); } @Override public Iterator> iterator() { return new AbstractSequentialIterator>(peek()) { @Override protected ReferenceEntry computeNext(ReferenceEntry previous) { ReferenceEntry next = previous.getNextExpirable(); return (next == head) ? null : next; } }; } } static final class CleanupMapTask implements Runnable { final WeakReference> mapReference; public CleanupMapTask(MapMakerInternalMap map) { this.mapReference = new WeakReference>(map); } @Override public void run() { MapMakerInternalMap map = mapReference.get(); if (map == null) { throw new CancellationException(); } for (Segment segment : map.segments) { segment.runCleanup(); } } } // ConcurrentMap methods @Override public boolean isEmpty() { /* * Sum per-segment modCounts to avoid mis-reporting when elements are concurrently added and * removed in one segment while checking another, in which case the table was never actually * empty at any point. (The sum ensures accuracy up through at least 1<<31 per-segment * modifications before recheck.) Method containsValue() uses similar constructions for * stability checks. */ long sum = 0L; Segment[] segments = this.segments; for (int i = 0; i < segments.length; ++i) { if (segments[i].count != 0) { return false; } sum += segments[i].modCount; } if (sum != 0L) { // recheck unless no modifications for (int i = 0; i < segments.length; ++i) { if (segments[i].count != 0) { return false; } sum -= segments[i].modCount; } if (sum != 0L) { return false; } } return true; } @Override public int size() { Segment[] segments = this.segments; long sum = 0; for (int i = 0; i < segments.length; ++i) { sum += segments[i].count; } return Ints.saturatedCast(sum); } @Override public V get(@Nullable Object key) { if (key == null) { return null; } int hash = hash(key); return segmentFor(hash).get(key, hash); } /** * Returns the internal entry for the specified key. The entry may be computing, expired, or * partially collected. Does not impact recency ordering. */ ReferenceEntry getEntry(@Nullable Object key) { if (key == null) { return null; } int hash = hash(key); return segmentFor(hash).getEntry(key, hash); } @Override public boolean containsKey(@Nullable Object key) { if (key == null) { return false; } int hash = hash(key); return segmentFor(hash).containsKey(key, hash); } @Override public boolean containsValue(@Nullable Object value) { if (value == null) { return false; } // This implementation is patterned after ConcurrentHashMap, but without the locking. The only // way for it to return a false negative would be for the target value to jump around in the map // such that none of the subsequent iterations observed it, despite the fact that at every point // in time it was present somewhere int the map. This becomes increasingly unlikely as // CONTAINS_VALUE_RETRIES increases, though without locking it is theoretically possible. final Segment[] segments = this.segments; long last = -1L; for (int i = 0; i < CONTAINS_VALUE_RETRIES; i++) { long sum = 0L; for (Segment segment : segments) { // ensure visibility of most recent completed write @SuppressWarnings({"UnusedDeclaration", "unused"}) int c = segment.count; // read-volatile AtomicReferenceArray> table = segment.table; for (int j = 0; j < table.length(); j++) { for (ReferenceEntry e = table.get(j); e != null; e = e.getNext()) { V v = segment.getLiveValue(e); if (v != null && valueEquivalence.equivalent(value, v)) { return true; } } } sum += segment.modCount; } if (sum == last) { break; } last = sum; } return false; } @Override public V put(K key, V value) { checkNotNull(key); checkNotNull(value); int hash = hash(key); return segmentFor(hash).put(key, hash, value, false); } @Override public V putIfAbsent(K key, V value) { checkNotNull(key); checkNotNull(value); int hash = hash(key); return segmentFor(hash).put(key, hash, value, true); } @Override public void putAll(Map m) { for (Entry e : m.entrySet()) { put(e.getKey(), e.getValue()); } } @Override public V remove(@Nullable Object key) { if (key == null) { return null; } int hash = hash(key); return segmentFor(hash).remove(key, hash); } @Override public boolean remove(@Nullable Object key, @Nullable Object value) { if (key == null || value == null) { return false; } int hash = hash(key); return segmentFor(hash).remove(key, hash, value); } @Override public boolean replace(K key, @Nullable V oldValue, V newValue) { checkNotNull(key); checkNotNull(newValue); if (oldValue == null) { return false; } int hash = hash(key); return segmentFor(hash).replace(key, hash, oldValue, newValue); } @Override public V replace(K key, V value) { checkNotNull(key); checkNotNull(value); int hash = hash(key); return segmentFor(hash).replace(key, hash, value); } @Override public void clear() { for (Segment segment : segments) { segment.clear(); } } transient Set keySet; @Override public Set keySet() { Set ks = keySet; return (ks != null) ? ks : (keySet = new KeySet()); } transient Collection values; @Override public Collection values() { Collection vs = values; return (vs != null) ? vs : (values = new Values()); } transient Set> entrySet; @Override public Set> entrySet() { Set> es = entrySet; return (es != null) ? es : (entrySet = new EntrySet()); } // Iterator Support abstract class HashIterator implements Iterator { int nextSegmentIndex; int nextTableIndex; Segment currentSegment; AtomicReferenceArray> currentTable; ReferenceEntry nextEntry; WriteThroughEntry nextExternal; WriteThroughEntry lastReturned; HashIterator() { nextSegmentIndex = segments.length - 1; nextTableIndex = -1; advance(); } public abstract E next(); final void advance() { nextExternal = null; if (nextInChain()) { return; } if (nextInTable()) { return; } while (nextSegmentIndex >= 0) { currentSegment = segments[nextSegmentIndex--]; if (currentSegment.count != 0) { currentTable = currentSegment.table; nextTableIndex = currentTable.length() - 1; if (nextInTable()) { return; } } } } /** * Finds the next entry in the current chain. Returns {@code true} if an entry was found. */ boolean nextInChain() { if (nextEntry != null) { for (nextEntry = nextEntry.getNext(); nextEntry != null; nextEntry = nextEntry.getNext()) { if (advanceTo(nextEntry)) { return true; } } } return false; } /** * Finds the next entry in the current table. Returns {@code true} if an entry was found. */ boolean nextInTable() { while (nextTableIndex >= 0) { if ((nextEntry = currentTable.get(nextTableIndex--)) != null) { if (advanceTo(nextEntry) || nextInChain()) { return true; } } } return false; } /** * Advances to the given entry. Returns {@code true} if the entry was valid, {@code false} if it * should be skipped. */ boolean advanceTo(ReferenceEntry entry) { try { K key = entry.getKey(); V value = getLiveValue(entry); if (value != null) { nextExternal = new WriteThroughEntry(key, value); return true; } else { // Skip stale entry. return false; } } finally { currentSegment.postReadCleanup(); } } public boolean hasNext() { return nextExternal != null; } WriteThroughEntry nextEntry() { if (nextExternal == null) { throw new NoSuchElementException(); } lastReturned = nextExternal; advance(); return lastReturned; } public void remove() { checkState(lastReturned != null); MapMakerInternalMap.this.remove(lastReturned.getKey()); lastReturned = null; } } final class KeyIterator extends HashIterator { @Override public K next() { return nextEntry().getKey(); } } final class ValueIterator extends HashIterator { @Override public V next() { return nextEntry().getValue(); } } /** * Custom Entry class used by EntryIterator.next(), that relays setValue changes to the * underlying map. */ final class WriteThroughEntry extends AbstractMapEntry { final K key; // non-null V value; // non-null WriteThroughEntry(K key, V value) { this.key = key; this.value = value; } @Override public K getKey() { return key; } @Override public V getValue() { return value; } @Override public boolean equals(@Nullable Object object) { // Cannot use key and value equivalence if (object instanceof Entry) { Entry that = (Entry) object; return key.equals(that.getKey()) && value.equals(that.getValue()); } return false; } @Override public int hashCode() { // Cannot use key and value equivalence return key.hashCode() ^ value.hashCode(); } @Override public V setValue(V newValue) { V oldValue = put(key, newValue); value = newValue; // only if put succeeds return oldValue; } } final class EntryIterator extends HashIterator> { @Override public Entry next() { return nextEntry(); } } final class KeySet extends AbstractSet { @Override public Iterator iterator() { return new KeyIterator(); } @Override public int size() { return MapMakerInternalMap.this.size(); } @Override public boolean isEmpty() { return MapMakerInternalMap.this.isEmpty(); } @Override public boolean contains(Object o) { return MapMakerInternalMap.this.containsKey(o); } @Override public boolean remove(Object o) { return MapMakerInternalMap.this.remove(o) != null; } @Override public void clear() { MapMakerInternalMap.this.clear(); } } final class Values extends AbstractCollection { @Override public Iterator iterator() { return new ValueIterator(); } @Override public int size() { return MapMakerInternalMap.this.size(); } @Override public boolean isEmpty() { return MapMakerInternalMap.this.isEmpty(); } @Override public boolean contains(Object o) { return MapMakerInternalMap.this.containsValue(o); } @Override public void clear() { MapMakerInternalMap.this.clear(); } } final class EntrySet extends AbstractSet> { @Override public Iterator> iterator() { return new EntryIterator(); } @Override public boolean contains(Object o) { if (!(o instanceof Entry)) { return false; } Entry e = (Entry) o; Object key = e.getKey(); if (key == null) { return false; } V v = MapMakerInternalMap.this.get(key); return v != null && valueEquivalence.equivalent(e.getValue(), v); } @Override public boolean remove(Object o) { if (!(o instanceof Entry)) { return false; } Entry e = (Entry) o; Object key = e.getKey(); return key != null && MapMakerInternalMap.this.remove(key, e.getValue()); } @Override public int size() { return MapMakerInternalMap.this.size(); } @Override public boolean isEmpty() { return MapMakerInternalMap.this.isEmpty(); } @Override public void clear() { MapMakerInternalMap.this.clear(); } } // Serialization Support private static final long serialVersionUID = 5; Object writeReplace() { return new SerializationProxy(keyStrength, valueStrength, keyEquivalence, valueEquivalence, expireAfterWriteNanos, expireAfterAccessNanos, maximumSize, concurrencyLevel, removalListener, this); } /** * The actual object that gets serialized. Unfortunately, readResolve() doesn't get called when a * circular dependency is present, so the proxy must be able to behave as the map itself. */ abstract static class AbstractSerializationProxy extends ForwardingConcurrentMap implements Serializable { private static final long serialVersionUID = 3; final Strength keyStrength; final Strength valueStrength; final Equivalence keyEquivalence; final Equivalence valueEquivalence; final long expireAfterWriteNanos; final long expireAfterAccessNanos; final int maximumSize; final int concurrencyLevel; final RemovalListener removalListener; transient ConcurrentMap delegate; AbstractSerializationProxy(Strength keyStrength, Strength valueStrength, Equivalence keyEquivalence, Equivalence valueEquivalence, long expireAfterWriteNanos, long expireAfterAccessNanos, int maximumSize, int concurrencyLevel, RemovalListener removalListener, ConcurrentMap delegate) { this.keyStrength = keyStrength; this.valueStrength = valueStrength; this.keyEquivalence = keyEquivalence; this.valueEquivalence = valueEquivalence; this.expireAfterWriteNanos = expireAfterWriteNanos; this.expireAfterAccessNanos = expireAfterAccessNanos; this.maximumSize = maximumSize; this.concurrencyLevel = concurrencyLevel; this.removalListener = removalListener; this.delegate = delegate; } @Override protected ConcurrentMap delegate() { return delegate; } void writeMapTo(ObjectOutputStream out) throws IOException { out.writeInt(delegate.size()); for (Entry entry : delegate.entrySet()) { out.writeObject(entry.getKey()); out.writeObject(entry.getValue()); } out.writeObject(null); // terminate entries } @SuppressWarnings("deprecation") // serialization of deprecated feature MapMaker readMapMaker(ObjectInputStream in) throws IOException { int size = in.readInt(); MapMaker mapMaker = new MapMaker() .initialCapacity(size) .setKeyStrength(keyStrength) .setValueStrength(valueStrength) .keyEquivalence(keyEquivalence) .concurrencyLevel(concurrencyLevel); mapMaker.removalListener(removalListener); if (expireAfterWriteNanos > 0) { mapMaker.expireAfterWrite(expireAfterWriteNanos, TimeUnit.NANOSECONDS); } if (expireAfterAccessNanos > 0) { mapMaker.expireAfterAccess(expireAfterAccessNanos, TimeUnit.NANOSECONDS); } if (maximumSize != MapMaker.UNSET_INT) { mapMaker.maximumSize(maximumSize); } return mapMaker; } @SuppressWarnings("unchecked") void readEntries(ObjectInputStream in) throws IOException, ClassNotFoundException { while (true) { K key = (K) in.readObject(); if (key == null) { break; // terminator } V value = (V) in.readObject(); delegate.put(key, value); } } } /** * The actual object that gets serialized. Unfortunately, readResolve() doesn't get called when a * circular dependency is present, so the proxy must be able to behave as the map itself. */ private static final class SerializationProxy extends AbstractSerializationProxy { private static final long serialVersionUID = 3; SerializationProxy(Strength keyStrength, Strength valueStrength, Equivalence keyEquivalence, Equivalence valueEquivalence, long expireAfterWriteNanos, long expireAfterAccessNanos, int maximumSize, int concurrencyLevel, RemovalListener removalListener, ConcurrentMap delegate) { super(keyStrength, valueStrength, keyEquivalence, valueEquivalence, expireAfterWriteNanos, expireAfterAccessNanos, maximumSize, concurrencyLevel, removalListener, delegate); } private void writeObject(ObjectOutputStream out) throws IOException { out.defaultWriteObject(); writeMapTo(out); } private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException { in.defaultReadObject(); MapMaker mapMaker = readMapMaker(in); delegate = mapMaker.makeMap(); readEntries(in); } private Object readResolve() { return delegate; } } }