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android / platform / external / guava / f6044de72265d1bc5e85a13e6ce0886504f2b0ea / . / android / guava / src / com / google / common / collect / MapMakerInternalMap.java
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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 com.google.common.collect;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.collect.CollectPreconditions.checkRemove;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Equivalence;
import com.google.common.collect.MapMaker.Dummy;
import com.google.common.primitives.Ints;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import com.google.errorprone.annotations.concurrent.GuardedBy;
import com.google.j2objc.annotations.Weak;
import com.google.j2objc.annotations.WeakOuter;
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.WeakReference;
import java.util.AbstractCollection;
import java.util.AbstractMap;
import java.util.AbstractSet;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Set;
import java.util.concurrent.CancellationException;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicReferenceArray;
import java.util.concurrent.locks.ReentrantLock;
import org.checkerframework.checker.nullness.compatqual.NullableDecl;
/**
* The concurrent hash map implementation built by {@link MapMaker}.
*
* <p>This implementation is heavily derived from revision 1.96 of <a
* href="http://tinyurl.com/ConcurrentHashMap">ConcurrentHashMap.java</a>.
*
* @param <K> the type of the keys in the map
* @param <V> the type of the values in the map
* @param <E> the type of the {@link InternalEntry} entry implementation used internally
* @param <S> the type of the {@link Segment} entry implementation used internally
* @author Bob Lee
* @author Charles Fry
* @author Doug Lea ({@code ConcurrentHashMap})
*/
// TODO(kak): Consider removing @CanIgnoreReturnValue from this class.
@GwtIncompatible
@SuppressWarnings("GuardedBy") // TODO(b/35466881): Fix or suppress.
class MapMakerInternalMap<
K,
V,
E extends MapMakerInternalMap.InternalEntry<K, V, E>,
S extends MapMakerInternalMap.Segment<K, V, E, S>>
extends AbstractMap<K, V> implements ConcurrentMap<K, V>, 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.
*
* 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 no greater than {@code 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.
*
* <p>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
/**
* 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<K, V, E, S>[] segments;
/** The concurrency level. */
final int concurrencyLevel;
/** Strategy for comparing keys. */
final Equivalence<Object> keyEquivalence;
/** Strategy for handling entries and segments in a type-safe and efficient manner. */
final transient InternalEntryHelper<K, V, E, S> entryHelper;
/**
* Creates a new, empty map with the specified strategy, initial capacity and concurrency level.
*/
private MapMakerInternalMap(MapMaker builder, InternalEntryHelper<K, V, E, S> entryHelper) {
concurrencyLevel = Math.min(builder.getConcurrencyLevel(), MAX_SEGMENTS);
keyEquivalence = builder.getKeyEquivalence();
this.entryHelper = entryHelper;
int initialCapacity = Math.min(builder.getInitialCapacity(), MAXIMUM_CAPACITY);
// Find power-of-two sizes best matching arguments. Constraints:
// (segmentCount > concurrencyLevel)
int segmentShift = 0;
int segmentCount = 1;
while (segmentCount < concurrencyLevel) {
++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;
}
for (int i = 0; i < this.segments.length; ++i) {
this.segments[i] = createSegment(segmentSize, MapMaker.UNSET_INT);
}
}
/** Returns a fresh {@link MapMakerInternalMap} as specified by the given {@code builder}. */
static <K, V> MapMakerInternalMap<K, V, ? extends InternalEntry<K, V, ?>, ?> create(
MapMaker builder) {
if (builder.getKeyStrength() == Strength.STRONG
&& builder.getValueStrength() == Strength.STRONG) {
return new MapMakerInternalMap<>(builder, StrongKeyStrongValueEntry.Helper.<K, V>instance());
}
if (builder.getKeyStrength() == Strength.STRONG
&& builder.getValueStrength() == Strength.WEAK) {
return new MapMakerInternalMap<>(builder, StrongKeyWeakValueEntry.Helper.<K, V>instance());
}
if (builder.getKeyStrength() == Strength.WEAK
&& builder.getValueStrength() == Strength.STRONG) {
return new MapMakerInternalMap<>(builder, WeakKeyStrongValueEntry.Helper.<K, V>instance());
}
if (builder.getKeyStrength() == Strength.WEAK && builder.getValueStrength() == Strength.WEAK) {
return new MapMakerInternalMap<>(builder, WeakKeyWeakValueEntry.Helper.<K, V>instance());
}
throw new AssertionError();
}
/**
* Returns a fresh {@link MapMakerInternalMap} with {@link MapMaker.Dummy} values but otherwise as
* specified by the given {@code builder}. The returned {@link MapMakerInternalMap} will be
* optimized to saved memory. Since {@link MapMaker.Dummy} is a singleton, we don't need to store
* any values at all. Because of this optimization, {@code build.getValueStrength()} must be
* {@link Strength#STRONG}.
*
* <p>This method is intended to only be used by the internal implementation of {@link Interners},
* since a map of dummy values is the exact use case there.
*/
static <K>
MapMakerInternalMap<K, Dummy, ? extends InternalEntry<K, Dummy, ?>, ?> createWithDummyValues(
MapMaker builder) {
if (builder.getKeyStrength() == Strength.STRONG
&& builder.getValueStrength() == Strength.STRONG) {
return new MapMakerInternalMap<>(builder, StrongKeyDummyValueEntry.Helper.<K>instance());
}
if (builder.getKeyStrength() == Strength.WEAK
&& builder.getValueStrength() == Strength.STRONG) {
return new MapMakerInternalMap<>(builder, WeakKeyDummyValueEntry.Helper.<K>instance());
}
if (builder.getValueStrength() == Strength.WEAK) {
throw new IllegalArgumentException("Map cannot have both weak and dummy values");
}
throw new AssertionError();
}
enum Strength {
STRONG {
@Override
Equivalence<Object> defaultEquivalence() {
return Equivalence.equals();
}
},
WEAK {
@Override
Equivalence<Object> defaultEquivalence() {
return Equivalence.identity();
}
};
/**
* 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<Object> defaultEquivalence();
}
/**
* A helper object for operating on {@link InternalEntry} instances in a type-safe and efficient
* manner.
*
* <p>For each of the four combinations of strong/weak key and strong/weak value, there are
* corresponding {@link InternalEntry}, {@link Segment}, and {@link InternalEntryHelper}
* implementations.
*
* @param <K> the type of the key in each entry
* @param <V> the type of the value in each entry
* @param <E> the type of the {@link InternalEntry} entry implementation
* @param <S> the type of the {@link Segment} entry implementation
*/
interface InternalEntryHelper<
K, V, E extends InternalEntry<K, V, E>, S extends Segment<K, V, E, S>> {
/** The strength of the key type in each entry. */
Strength keyStrength();
/** The strength of the value type in each entry. */
Strength valueStrength();
/** Returns a freshly created segment, typed at the {@code S} type. */
S newSegment(MapMakerInternalMap<K, V, E, S> map, int initialCapacity, int maxSegmentSize);
/**
* Returns a freshly created entry, typed at the {@code E} type, for the given {@code segment}.
*/
E newEntry(S segment, K key, int hash, @NullableDecl E next);
/**
* Returns a freshly created entry, typed at the {@code E} type, for the given {@code segment},
* that is a copy of the given {@code entry}.
*/
E copy(S segment, E entry, @NullableDecl E newNext);
/**
* Sets the value of the given {@code entry} in the given {@code segment} to be the given {@code
* value}
*/
void setValue(S segment, E entry, V value);
}
/**
* An entry in a hash table of a {@link Segment}.
*
* <p>Entries in the map can be in the following states:
*
* <p>Valid: - Live: valid key/value are set
*
* <p>Invalid: - Collected: key/value was partially collected, but not yet cleaned up
*/
interface InternalEntry<K, V, E extends InternalEntry<K, V, E>> {
/** Gets the next entry in the chain. */
E getNext();
/** Gets the entry's hash. */
int getHash();
/** Gets the key for this entry. */
K getKey();
/** Gets the value for the entry. */
V getValue();
}
/*
* Note: the following classes have a lot of duplicate code. It sucks, but it saves a lot of
* memory. If only Java had mixins!
*/
/** Base class for {@link InternalEntry} implementations for strong keys. */
abstract static class AbstractStrongKeyEntry<K, V, E extends InternalEntry<K, V, E>>
implements InternalEntry<K, V, E> {
final K key;
final int hash;
@NullableDecl final E next;
AbstractStrongKeyEntry(K key, int hash, @NullableDecl E next) {
this.key = key;
this.hash = hash;
this.next = next;
}
@Override
public K getKey() {
return this.key;
}
@Override
public int getHash() {
return hash;
}
@Override
public E getNext() {
return next;
}
}
/** Marker interface for {@link InternalEntry} implementations for strong values. */
interface StrongValueEntry<K, V, E extends InternalEntry<K, V, E>>
extends InternalEntry<K, V, E> {}
/** Marker interface for {@link InternalEntry} implementations for weak values. */
interface WeakValueEntry<K, V, E extends InternalEntry<K, V, E>> extends InternalEntry<K, V, E> {
/** Gets the weak value reference held by entry. */
WeakValueReference<K, V, E> getValueReference();
/**
* Clears the weak value reference held by the entry. Should be used when the entry's value is
* overwritten.
*/
void clearValue();
}
@SuppressWarnings("unchecked") // impl never uses a parameter or returns any non-null value
static <K, V, E extends InternalEntry<K, V, E>>
WeakValueReference<K, V, E> unsetWeakValueReference() {
return (WeakValueReference<K, V, E>) UNSET_WEAK_VALUE_REFERENCE;
}
/** Concrete implementation of {@link InternalEntry} for strong keys and strong values. */
static final class StrongKeyStrongValueEntry<K, V>
extends AbstractStrongKeyEntry<K, V, StrongKeyStrongValueEntry<K, V>>
implements StrongValueEntry<K, V, StrongKeyStrongValueEntry<K, V>> {
@NullableDecl private volatile V value = null;
StrongKeyStrongValueEntry(K key, int hash, @NullableDecl StrongKeyStrongValueEntry<K, V> next) {
super(key, hash, next);
}
@Override
@NullableDecl
public V getValue() {
return value;
}
void setValue(V value) {
this.value = value;
}
StrongKeyStrongValueEntry<K, V> copy(StrongKeyStrongValueEntry<K, V> newNext) {
StrongKeyStrongValueEntry<K, V> newEntry =
new StrongKeyStrongValueEntry<>(this.key, this.hash, newNext);
newEntry.value = this.value;
return newEntry;
}
/** Concrete implementation of {@link InternalEntryHelper} for strong keys and strong values. */
static final class Helper<K, V>
implements InternalEntryHelper<
K, V, StrongKeyStrongValueEntry<K, V>, StrongKeyStrongValueSegment<K, V>> {
private static final Helper<?, ?> INSTANCE = new Helper<>();
@SuppressWarnings("unchecked")
static <K, V> Helper<K, V> instance() {
return (Helper<K, V>) INSTANCE;
}
@Override
public Strength keyStrength() {
return Strength.STRONG;
}
@Override
public Strength valueStrength() {
return Strength.STRONG;
}
@Override
public StrongKeyStrongValueSegment<K, V> newSegment(
MapMakerInternalMap<
K, V, StrongKeyStrongValueEntry<K, V>, StrongKeyStrongValueSegment<K, V>>
map,
int initialCapacity,
int maxSegmentSize) {
return new StrongKeyStrongValueSegment<>(map, initialCapacity, maxSegmentSize);
}
@Override
public StrongKeyStrongValueEntry<K, V> copy(
StrongKeyStrongValueSegment<K, V> segment,
StrongKeyStrongValueEntry<K, V> entry,
@NullableDecl StrongKeyStrongValueEntry<K, V> newNext) {
return entry.copy(newNext);
}
@Override
public void setValue(
StrongKeyStrongValueSegment<K, V> segment,
StrongKeyStrongValueEntry<K, V> entry,
V value) {
entry.setValue(value);
}
@Override
public StrongKeyStrongValueEntry<K, V> newEntry(
StrongKeyStrongValueSegment<K, V> segment,
K key,
int hash,
@NullableDecl StrongKeyStrongValueEntry<K, V> next) {
return new StrongKeyStrongValueEntry<>(key, hash, next);
}
}
}
/** Concrete implementation of {@link InternalEntry} for strong keys and weak values. */
static final class StrongKeyWeakValueEntry<K, V>
extends AbstractStrongKeyEntry<K, V, StrongKeyWeakValueEntry<K, V>>
implements WeakValueEntry<K, V, StrongKeyWeakValueEntry<K, V>> {
private volatile WeakValueReference<K, V, StrongKeyWeakValueEntry<K, V>> valueReference =
unsetWeakValueReference();
StrongKeyWeakValueEntry(K key, int hash, @NullableDecl StrongKeyWeakValueEntry<K, V> next) {
super(key, hash, next);
}
@Override
public V getValue() {
return valueReference.get();
}
@Override
public void clearValue() {
valueReference.clear();
}
void setValue(V value, ReferenceQueue<V> queueForValues) {
WeakValueReference<K, V, StrongKeyWeakValueEntry<K, V>> previous = this.valueReference;
this.valueReference = new WeakValueReferenceImpl<>(queueForValues, value, this);
previous.clear();
}
StrongKeyWeakValueEntry<K, V> copy(
ReferenceQueue<V> queueForValues, StrongKeyWeakValueEntry<K, V> newNext) {
StrongKeyWeakValueEntry<K, V> newEntry = new StrongKeyWeakValueEntry<>(key, hash, newNext);
newEntry.valueReference = valueReference.copyFor(queueForValues, newEntry);
return newEntry;
}
@Override
public WeakValueReference<K, V, StrongKeyWeakValueEntry<K, V>> getValueReference() {
return valueReference;
}
/** Concrete implementation of {@link InternalEntryHelper} for strong keys and weak values. */
static final class Helper<K, V>
implements InternalEntryHelper<
K, V, StrongKeyWeakValueEntry<K, V>, StrongKeyWeakValueSegment<K, V>> {
private static final Helper<?, ?> INSTANCE = new Helper<>();
@SuppressWarnings("unchecked")
static <K, V> Helper<K, V> instance() {
return (Helper<K, V>) INSTANCE;
}
@Override
public Strength keyStrength() {
return Strength.STRONG;
}
@Override
public Strength valueStrength() {
return Strength.WEAK;
}
@Override
public StrongKeyWeakValueSegment<K, V> newSegment(
MapMakerInternalMap<K, V, StrongKeyWeakValueEntry<K, V>, StrongKeyWeakValueSegment<K, V>>
map,
int initialCapacity,
int maxSegmentSize) {
return new StrongKeyWeakValueSegment<>(map, initialCapacity, maxSegmentSize);
}
@Override
public StrongKeyWeakValueEntry<K, V> copy(
StrongKeyWeakValueSegment<K, V> segment,
StrongKeyWeakValueEntry<K, V> entry,
@NullableDecl StrongKeyWeakValueEntry<K, V> newNext) {
if (Segment.isCollected(entry)) {
return null;
}
return entry.copy(segment.queueForValues, newNext);
}
@Override
public void setValue(
StrongKeyWeakValueSegment<K, V> segment, StrongKeyWeakValueEntry<K, V> entry, V value) {
entry.setValue(value, segment.queueForValues);
}
@Override
public StrongKeyWeakValueEntry<K, V> newEntry(
StrongKeyWeakValueSegment<K, V> segment,
K key,
int hash,
@NullableDecl StrongKeyWeakValueEntry<K, V> next) {
return new StrongKeyWeakValueEntry<>(key, hash, next);
}
}
}
/** Concrete implementation of {@link InternalEntry} for strong keys and {@link Dummy} values. */
static final class StrongKeyDummyValueEntry<K>
extends AbstractStrongKeyEntry<K, Dummy, StrongKeyDummyValueEntry<K>>
implements StrongValueEntry<K, Dummy, StrongKeyDummyValueEntry<K>> {
StrongKeyDummyValueEntry(K key, int hash, @NullableDecl StrongKeyDummyValueEntry<K> next) {
super(key, hash, next);
}
@Override
public Dummy getValue() {
return Dummy.VALUE;
}
void setValue(Dummy value) {}
StrongKeyDummyValueEntry<K> copy(StrongKeyDummyValueEntry<K> newNext) {
return new StrongKeyDummyValueEntry<K>(this.key, this.hash, newNext);
}
/**
* Concrete implementation of {@link InternalEntryHelper} for strong keys and {@link Dummy}
* values.
*/
static final class Helper<K>
implements InternalEntryHelper<
K, Dummy, StrongKeyDummyValueEntry<K>, StrongKeyDummyValueSegment<K>> {
private static final Helper<?> INSTANCE = new Helper<>();
@SuppressWarnings("unchecked")
static <K> Helper<K> instance() {
return (Helper<K>) INSTANCE;
}
@Override
public Strength keyStrength() {
return Strength.STRONG;
}
@Override
public Strength valueStrength() {
return Strength.STRONG;
}
@Override
public StrongKeyDummyValueSegment<K> newSegment(
MapMakerInternalMap<K, Dummy, StrongKeyDummyValueEntry<K>, StrongKeyDummyValueSegment<K>>
map,
int initialCapacity,
int maxSegmentSize) {
return new StrongKeyDummyValueSegment<K>(map, initialCapacity, maxSegmentSize);
}
@Override
public StrongKeyDummyValueEntry<K> copy(
StrongKeyDummyValueSegment<K> segment,
StrongKeyDummyValueEntry<K> entry,
@NullableDecl StrongKeyDummyValueEntry<K> newNext) {
return entry.copy(newNext);
}
@Override
public void setValue(
StrongKeyDummyValueSegment<K> segment, StrongKeyDummyValueEntry<K> entry, Dummy value) {}
@Override
public StrongKeyDummyValueEntry<K> newEntry(
StrongKeyDummyValueSegment<K> segment,
K key,
int hash,
@NullableDecl StrongKeyDummyValueEntry<K> next) {
return new StrongKeyDummyValueEntry<K>(key, hash, next);
}
}
}
/** Base class for {@link InternalEntry} implementations for weak keys. */
abstract static class AbstractWeakKeyEntry<K, V, E extends InternalEntry<K, V, E>>
extends WeakReference<K> implements InternalEntry<K, V, E> {
final int hash;
@NullableDecl final E next;
AbstractWeakKeyEntry(ReferenceQueue<K> queue, K key, int hash, @NullableDecl E next) {
super(key, queue);
this.hash = hash;
this.next = next;
}
@Override
public K getKey() {
return get();
}
@Override
public int getHash() {
return hash;
}
@Override
public E getNext() {
return next;
}
}
/** Concrete implementation of {@link InternalEntry} for weak keys and {@link Dummy} values. */
static final class WeakKeyDummyValueEntry<K>
extends AbstractWeakKeyEntry<K, Dummy, WeakKeyDummyValueEntry<K>>
implements StrongValueEntry<K, Dummy, WeakKeyDummyValueEntry<K>> {
WeakKeyDummyValueEntry(
ReferenceQueue<K> queue, K key, int hash, @NullableDecl WeakKeyDummyValueEntry<K> next) {
super(queue, key, hash, next);
}
@Override
public Dummy getValue() {
return Dummy.VALUE;
}
void setValue(Dummy value) {}
WeakKeyDummyValueEntry<K> copy(
ReferenceQueue<K> queueForKeys, WeakKeyDummyValueEntry<K> newNext) {
return new WeakKeyDummyValueEntry<K>(queueForKeys, getKey(), this.hash, newNext);
}
/**
* Concrete implementation of {@link InternalEntryHelper} for weak keys and {@link Dummy}
* values.
*/
static final class Helper<K>
implements InternalEntryHelper<
K, Dummy, WeakKeyDummyValueEntry<K>, WeakKeyDummyValueSegment<K>> {
private static final Helper<?> INSTANCE = new Helper<>();
@SuppressWarnings("unchecked")
static <K> Helper<K> instance() {
return (Helper<K>) INSTANCE;
}
@Override
public Strength keyStrength() {
return Strength.WEAK;
}
@Override
public Strength valueStrength() {
return Strength.STRONG;
}
@Override
public WeakKeyDummyValueSegment<K> newSegment(
MapMakerInternalMap<K, Dummy, WeakKeyDummyValueEntry<K>, WeakKeyDummyValueSegment<K>> map,
int initialCapacity,
int maxSegmentSize) {
return new WeakKeyDummyValueSegment<K>(map, initialCapacity, maxSegmentSize);
}
@Override
public WeakKeyDummyValueEntry<K> copy(
WeakKeyDummyValueSegment<K> segment,
WeakKeyDummyValueEntry<K> entry,
@NullableDecl WeakKeyDummyValueEntry<K> newNext) {
if (entry.getKey() == null) {
// key collected
return null;
}
return entry.copy(segment.queueForKeys, newNext);
}
@Override
public void setValue(
WeakKeyDummyValueSegment<K> segment, WeakKeyDummyValueEntry<K> entry, Dummy value) {}
@Override
public WeakKeyDummyValueEntry<K> newEntry(
WeakKeyDummyValueSegment<K> segment,
K key,
int hash,
@NullableDecl WeakKeyDummyValueEntry<K> next) {
return new WeakKeyDummyValueEntry<K>(segment.queueForKeys, key, hash, next);
}
}
}
/** Concrete implementation of {@link InternalEntry} for weak keys and strong values. */
static final class WeakKeyStrongValueEntry<K, V>
extends AbstractWeakKeyEntry<K, V, WeakKeyStrongValueEntry<K, V>>
implements StrongValueEntry<K, V, WeakKeyStrongValueEntry<K, V>> {
@NullableDecl private volatile V value = null;
WeakKeyStrongValueEntry(
ReferenceQueue<K> queue,
K key,
int hash,
@NullableDecl WeakKeyStrongValueEntry<K, V> next) {
super(queue, key, hash, next);
}
@Override
@NullableDecl
public V getValue() {
return value;
}
void setValue(V value) {
this.value = value;
}
WeakKeyStrongValueEntry<K, V> copy(
ReferenceQueue<K> queueForKeys, WeakKeyStrongValueEntry<K, V> newNext) {
WeakKeyStrongValueEntry<K, V> newEntry =
new WeakKeyStrongValueEntry<>(queueForKeys, getKey(), this.hash, newNext);
newEntry.setValue(value);
return newEntry;
}
/** Concrete implementation of {@link InternalEntryHelper} for weak keys and strong values. */
static final class Helper<K, V>
implements InternalEntryHelper<
K, V, WeakKeyStrongValueEntry<K, V>, WeakKeyStrongValueSegment<K, V>> {
private static final Helper<?, ?> INSTANCE = new Helper<>();
@SuppressWarnings("unchecked")
static <K, V> Helper<K, V> instance() {
return (Helper<K, V>) INSTANCE;
}
@Override
public Strength keyStrength() {
return Strength.WEAK;
}
@Override
public Strength valueStrength() {
return Strength.STRONG;
}
@Override
public WeakKeyStrongValueSegment<K, V> newSegment(
MapMakerInternalMap<K, V, WeakKeyStrongValueEntry<K, V>, WeakKeyStrongValueSegment<K, V>>
map,
int initialCapacity,
int maxSegmentSize) {
return new WeakKeyStrongValueSegment<>(map, initialCapacity, maxSegmentSize);
}
@Override
public WeakKeyStrongValueEntry<K, V> copy(
WeakKeyStrongValueSegment<K, V> segment,
WeakKeyStrongValueEntry<K, V> entry,
@NullableDecl WeakKeyStrongValueEntry<K, V> newNext) {
if (entry.getKey() == null) {
// key collected
return null;
}
return entry.copy(segment.queueForKeys, newNext);
}
@Override
public void setValue(
WeakKeyStrongValueSegment<K, V> segment, WeakKeyStrongValueEntry<K, V> entry, V value) {
entry.setValue(value);
}
@Override
public WeakKeyStrongValueEntry<K, V> newEntry(
WeakKeyStrongValueSegment<K, V> segment,
K key,
int hash,
@NullableDecl WeakKeyStrongValueEntry<K, V> next) {
return new WeakKeyStrongValueEntry<>(segment.queueForKeys, key, hash, next);
}
}
}
/** Concrete implementation of {@link InternalEntry} for weak keys and weak values. */
static final class WeakKeyWeakValueEntry<K, V>
extends AbstractWeakKeyEntry<K, V, WeakKeyWeakValueEntry<K, V>>
implements WeakValueEntry<K, V, WeakKeyWeakValueEntry<K, V>> {
private volatile WeakValueReference<K, V, WeakKeyWeakValueEntry<K, V>> valueReference =
unsetWeakValueReference();
WeakKeyWeakValueEntry(
ReferenceQueue<K> queue, K key, int hash, @NullableDecl WeakKeyWeakValueEntry<K, V> next) {
super(queue, key, hash, next);
}
@Override
public V getValue() {
return valueReference.get();
}
WeakKeyWeakValueEntry<K, V> copy(
ReferenceQueue<K> queueForKeys,
ReferenceQueue<V> queueForValues,
WeakKeyWeakValueEntry<K, V> newNext) {
WeakKeyWeakValueEntry<K, V> newEntry =
new WeakKeyWeakValueEntry<>(queueForKeys, getKey(), this.hash, newNext);
newEntry.valueReference = valueReference.copyFor(queueForValues, newEntry);
return newEntry;
}
@Override
public void clearValue() {
valueReference.clear();
}
void setValue(V value, ReferenceQueue<V> queueForValues) {
WeakValueReference<K, V, WeakKeyWeakValueEntry<K, V>> previous = this.valueReference;
this.valueReference = new WeakValueReferenceImpl<>(queueForValues, value, this);
previous.clear();
}
@Override
public WeakValueReference<K, V, WeakKeyWeakValueEntry<K, V>> getValueReference() {
return valueReference;
}
/** Concrete implementation of {@link InternalEntryHelper} for weak keys and weak values. */
static final class Helper<K, V>
implements InternalEntryHelper<
K, V, WeakKeyWeakValueEntry<K, V>, WeakKeyWeakValueSegment<K, V>> {
private static final Helper<?, ?> INSTANCE = new Helper<>();
@SuppressWarnings("unchecked")
static <K, V> Helper<K, V> instance() {
return (Helper<K, V>) INSTANCE;
}
@Override
public Strength keyStrength() {
return Strength.WEAK;
}
@Override
public Strength valueStrength() {
return Strength.WEAK;
}
@Override
public WeakKeyWeakValueSegment<K, V> newSegment(
MapMakerInternalMap<K, V, WeakKeyWeakValueEntry<K, V>, WeakKeyWeakValueSegment<K, V>> map,
int initialCapacity,
int maxSegmentSize) {
return new WeakKeyWeakValueSegment<>(map, initialCapacity, maxSegmentSize);
}
@Override
public WeakKeyWeakValueEntry<K, V> copy(
WeakKeyWeakValueSegment<K, V> segment,
WeakKeyWeakValueEntry<K, V> entry,
@NullableDecl WeakKeyWeakValueEntry<K, V> newNext) {
if (entry.getKey() == null) {
// key collected
return null;
}
if (Segment.isCollected(entry)) {
return null;
}
return entry.copy(segment.queueForKeys, segment.queueForValues, newNext);
}
@Override
public void setValue(
WeakKeyWeakValueSegment<K, V> segment, WeakKeyWeakValueEntry<K, V> entry, V value) {
entry.setValue(value, segment.queueForValues);
}
@Override
public WeakKeyWeakValueEntry<K, V> newEntry(
WeakKeyWeakValueSegment<K, V> segment,
K key,
int hash,
@NullableDecl WeakKeyWeakValueEntry<K, V> next) {
return new WeakKeyWeakValueEntry<>(segment.queueForKeys, key, hash, next);
}
}
}
/** A weakly referenced value that also has a reference to its containing entry. */
interface WeakValueReference<K, V, E extends InternalEntry<K, V, E>> {
/**
* Returns the current value being referenced, or {@code null} if there is none (e.g. because
* either it got collected, or {@link #clear} was called, or it wasn't set in the first place).
*/
@NullableDecl
V get();
/** Returns the entry which contains this {@link WeakValueReference}. */
E getEntry();
/** Unsets the referenced value. Subsequent calls to {@link #get} will return {@code null}. */
void clear();
/**
* Returns a freshly created {@link WeakValueReference} for the given {@code entry} (and on the
* given {@code queue} with the same value as this {@link WeakValueReference}.
*/
WeakValueReference<K, V, E> copyFor(ReferenceQueue<V> queue, E entry);
}
/**
* A dummy implementation of {@link InternalEntry}, solely for use in the type signature of {@link
* #UNSET_WEAK_VALUE_REFERENCE} below.
*/
static final class DummyInternalEntry
implements InternalEntry<Object, Object, DummyInternalEntry> {
private DummyInternalEntry() {
throw new AssertionError();
}
@Override
public DummyInternalEntry getNext() {
throw new AssertionError();
}
@Override
public int getHash() {
throw new AssertionError();
}
@Override
public Object getKey() {
throw new AssertionError();
}
@Override
public Object getValue() {
throw new AssertionError();
}
}
/**
* A singleton {@link WeakValueReference} used to denote an unset value in a entry with weak
* values.
*/
static final WeakValueReference<Object, Object, DummyInternalEntry> UNSET_WEAK_VALUE_REFERENCE =
new WeakValueReference<Object, Object, DummyInternalEntry>() {
@Override
public DummyInternalEntry getEntry() {
return null;
}
@Override
public void clear() {}
@Override
public Object get() {
return null;
}
@Override
public WeakValueReference<Object, Object, DummyInternalEntry> copyFor(
ReferenceQueue<Object> queue, DummyInternalEntry entry) {
return this;
}
};
/** Concrete implementation of {@link WeakValueReference}. */
static final class WeakValueReferenceImpl<K, V, E extends InternalEntry<K, V, E>>
extends WeakReference<V> implements WeakValueReference<K, V, E> {
@Weak final E entry;
WeakValueReferenceImpl(ReferenceQueue<V> queue, V referent, E entry) {
super(referent, queue);
this.entry = entry;
}
@Override
public E getEntry() {
return entry;
}
@Override
public WeakValueReference<K, V, E> copyFor(ReferenceQueue<V> queue, E entry) {
return new WeakValueReferenceImpl<>(queue, get(), entry);
}
}
/**
* 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#copyEntry} directly.
*/
// Guarded By Segment.this
@VisibleForTesting
E copyEntry(E original, E newNext) {
int hash = original.getHash();
return segmentFor(hash).copyEntry(original, newNext);
}
int hash(Object key) {
int h = keyEquivalence.hash(key);
return rehash(h);
}
void reclaimValue(WeakValueReference<K, V, E> valueReference) {
E entry = valueReference.getEntry();
int hash = entry.getHash();
segmentFor(hash).reclaimValue(entry.getKey(), hash, valueReference);
}
void reclaimKey(E 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 isLiveForTesting(InternalEntry<K, V, ?> entry) {
return segmentFor(entry.getHash()).getLiveValueForTesting(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<K, V, E, S> segmentFor(int hash) {
// TODO(fry): Lazily create segments?
return segments[(hash >>> segmentShift) & segmentMask];
}
Segment<K, V, E, S> createSegment(int initialCapacity, int maxSegmentSize) {
return entryHelper.newSegment(this, initialCapacity, maxSegmentSize);
}
/**
* Gets the value from an entry. Returns {@code null} if the entry is invalid, partially-collected
* or computing.
*/
V getLiveValue(E entry) {
if (entry.getKey() == null) {
return null;
}
return entry.getValue();
}
@SuppressWarnings("unchecked")
final Segment<K, V, E, S>[] 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.
abstract static class Segment<
K, V, E extends InternalEntry<K, V, E>, S extends Segment<K, V, E, S>>
extends ReentrantLock {
/*
* 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.
*/
@Weak final MapMakerInternalMap<K, V, E, S> 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. */
@NullableDecl volatile AtomicReferenceArray<E> table;
/** The maximum size of this map. MapMaker.UNSET_INT if there is no maximum. */
final int maxSegmentSize;
/**
* 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();
Segment(MapMakerInternalMap<K, V, E, S> map, int initialCapacity, int maxSegmentSize) {
this.map = map;
this.maxSegmentSize = maxSegmentSize;
initTable(newEntryArray(initialCapacity));
}
/**
* Returns {@code this} up-casted to the specific {@link Segment} implementation type {@code S}.
*
* <p>This method exists so that the {@link Segment} code can be generic in terms of {@code S},
* the type of the concrete implementation.
*/
abstract S self();
/** Drains the reference queues used by this segment, if any. */
@GuardedBy("this")
void maybeDrainReferenceQueues() {}
/** Clears the reference queues used by this segment, if any. */
void maybeClearReferenceQueues() {}
/** Sets the value of the given {@code entry}. */
void setValue(E entry, V value) {
this.map.entryHelper.setValue(self(), entry, value);
}
/** Returns a copy of the given {@code entry}. */
E copyEntry(E original, E newNext) {
return this.map.entryHelper.copy(self(), original, newNext);
}
AtomicReferenceArray<E> newEntryArray(int size) {
return new AtomicReferenceArray<E>(size);
}
void initTable(AtomicReferenceArray<E> newTable) {
this.threshold = newTable.length() * 3 / 4; // 0.75
if (this.threshold == maxSegmentSize) {
// prevent spurious expansion before eviction
this.threshold++;
}
this.table = newTable;
}
// Convenience methods for testing
/**
* Unsafe cast of the given entry to {@code E}, the type of the specific {@link InternalEntry}
* implementation type.
*
* <p>This method is provided as a convenience for tests. Otherwise they'd need to be
* knowledgable about all the implementation details of our type system trickery.
*/
abstract E castForTesting(InternalEntry<K, V, ?> entry);
/** Unsafely extracts the key reference queue used by this segment. */
ReferenceQueue<K> getKeyReferenceQueueForTesting() {
throw new AssertionError();
}
/** Unsafely extracts the value reference queue used by this segment. */
ReferenceQueue<V> getValueReferenceQueueForTesting() {
throw new AssertionError();
}
/** Unsafely extracts the weak value reference inside of the given {@code entry}. */
WeakValueReference<K, V, E> getWeakValueReferenceForTesting(InternalEntry<K, V, ?> entry) {
throw new AssertionError();
}
/**
* Unsafely creates of a fresh {@link WeakValueReference}, referencing the given {@code value},
* for the given {@code entry}
*/
WeakValueReference<K, V, E> newWeakValueReferenceForTesting(
InternalEntry<K, V, ?> entry, V value) {
throw new AssertionError();
}
/**
* Unsafely sets the weak value reference inside the given {@code entry} to be the given {@code
* valueReference}
*/
void setWeakValueReferenceForTesting(
InternalEntry<K, V, ?> entry,
WeakValueReference<K, V, ? extends InternalEntry<K, V, ?>> valueReference) {
throw new AssertionError();
}
/**
* Unsafely sets the given index of this segment's internal hash table to be the given entry.
*/
void setTableEntryForTesting(int i, InternalEntry<K, V, ?> entry) {
table.set(i, castForTesting(entry));
}
/** Unsafely returns a copy of the given entry. */
E copyForTesting(InternalEntry<K, V, ?> entry, @NullableDecl InternalEntry<K, V, ?> newNext) {
return this.map.entryHelper.copy(self(), castForTesting(entry), castForTesting(newNext));
}
/** Unsafely sets the value of the given entry. */
void setValueForTesting(InternalEntry<K, V, ?> entry, V value) {
this.map.entryHelper.setValue(self(), castForTesting(entry), value);
}
/** Unsafely returns a fresh entry. */
E newEntryForTesting(K key, int hash, @NullableDecl InternalEntry<K, V, ?> next) {
return this.map.entryHelper.newEntry(self(), key, hash, castForTesting(next));
}
/** Unsafely removes the given entry from this segment's hash table. */
@CanIgnoreReturnValue
boolean removeTableEntryForTesting(InternalEntry<K, V, ?> entry) {
return removeEntryForTesting(castForTesting(entry));
}
/** Unsafely removes the given entry from the given chain in this segment's hash table. */
E removeFromChainForTesting(InternalEntry<K, V, ?> first, InternalEntry<K, V, ?> entry) {
return removeFromChain(castForTesting(first), castForTesting(entry));
}
/**
* Unsafely returns the value of the given entry if it's still live, or {@code null} otherwise.
*/
@NullableDecl
V getLiveValueForTesting(InternalEntry<K, V, ?> entry) {
return getLiveValue(castForTesting(entry));
}
// reference queues, for garbage collection cleanup
/** Cleanup collected entries when the lock is available. */
void tryDrainReferenceQueues() {
if (tryLock()) {
try {
maybeDrainReferenceQueues();
} finally {
unlock();
}
}
}
@GuardedBy("this")
void drainKeyReferenceQueue(ReferenceQueue<K> keyReferenceQueue) {
Reference<? extends K> ref;
int i = 0;
while ((ref = keyReferenceQueue.poll()) != null) {
@SuppressWarnings("unchecked")
E entry = (E) ref;
map.reclaimKey(entry);
if (++i == DRAIN_MAX) {
break;
}
}
}
@GuardedBy("this")
void drainValueReferenceQueue(ReferenceQueue<V> valueReferenceQueue) {
Reference<? extends V> ref;
int i = 0;
while ((ref = valueReferenceQueue.poll()) != null) {
@SuppressWarnings("unchecked")
WeakValueReference<K, V, E> valueReference = (WeakValueReference<K, V, E>) ref;
map.reclaimValue(valueReference);
if (++i == DRAIN_MAX) {
break;
}
}
}
<T> void clearReferenceQueue(ReferenceQueue<T> referenceQueue) {
while (referenceQueue.poll() != null) {}
}
/** Returns first entry of bin for given hash. */
E getFirst(int hash) {
// read this volatile field only once
AtomicReferenceArray<E> table = this.table;
return table.get(hash & (table.length() - 1));
}
// Specialized implementations of map methods
E getEntry(Object key, int hash) {
if (count != 0) { // read-volatile
for (E 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;
}
E getLiveEntry(Object key, int hash) {
return getEntry(key, hash);
}
V get(Object key, int hash) {
try {
E e = getLiveEntry(key, hash);
if (e == null) {
return null;
}
V value = e.getValue();
if (value == null) {
tryDrainReferenceQueues();
}
return value;
} finally {
postReadCleanup();
}
}
boolean containsKey(Object key, int hash) {
try {
if (count != 0) { // read-volatile
E e = getLiveEntry(key, hash);
return e != null && e.getValue() != 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<E> table = this.table;
int length = table.length();
for (int i = 0; i < length; ++i) {
for (E 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<E> table = this.table;
int index = hash & (table.length() - 1);
E first = table.get(index);
// Look for an existing entry.
for (E 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.
V entryValue = e.getValue();
if (entryValue == null) {
++modCount;
setValue(e, value);
newCount = this.count; // count remains unchanged
this.count = newCount; // write-volatile
return null;
} else if (onlyIfAbsent) {
// Mimic
// "if (!map.containsKey(key)) ...
// else return map.get(key);
return entryValue;
} else {
// clobber existing entry, count remains unchanged
++modCount;
setValue(e, value);
return entryValue;
}
}
}
// Create a new entry.
++modCount;
E newEntry = map.entryHelper.newEntry(self(), key, hash, first);
setValue(newEntry, value);
table.set(index, newEntry);
this.count = newCount; // write-volatile
return null;
} finally {
unlock();
}
}
/** Expands the table if possible. */
@GuardedBy("this")
void expand() {
AtomicReferenceArray<E> 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<E> 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.
E head = oldTable.get(oldIndex);
if (head != null) {
E 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.
E tail = head;
int tailIndex = headIndex;
for (E 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 (E e = head; e != tail; e = e.getNext()) {
int newIndex = e.getHash() & newMask;
E newNext = newTable.get(newIndex);
E newFirst = copyEntry(e, newNext);
if (newFirst != null) {
newTable.set(newIndex, newFirst);
} else {
newCount--;
}
}
}
}
}
table = newTable;
this.count = newCount;
}
boolean replace(K key, int hash, V oldValue, V newValue) {
lock();
try {
preWriteCleanup();
AtomicReferenceArray<E> table = this.table;
int index = hash & (table.length() - 1);
E first = table.get(index);
for (E 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.
V entryValue = e.getValue();
if (entryValue == null) {
if (isCollected(e)) {
int newCount = this.count - 1;
++modCount;
E 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;
setValue(e, newValue);
return true;
} else {
// Mimic
// "if (map.containsKey(key) && map.get(key).equals(oldValue))..."
return false;
}
}
}
return false;
} finally {
unlock();
}
}
V replace(K key, int hash, V newValue) {
lock();
try {
preWriteCleanup();
AtomicReferenceArray<E> table = this.table;
int index = hash & (table.length() - 1);
E first = table.get(index);
for (E 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.
V entryValue = e.getValue();
if (entryValue == null) {
if (isCollected(e)) {
int newCount = this.count - 1;
++modCount;
E newFirst = removeFromChain(first, e);
newCount = this.count - 1;
table.set(index, newFirst);
this.count = newCount; // write-volatile
}
return null;
}
++modCount;
setValue(e, newValue);
return entryValue;
}
}
return null;
} finally {
unlock();
}
}
@CanIgnoreReturnValue
V remove(Object key, int hash) {
lock();
try {
preWriteCleanup();
int newCount = this.count - 1;
AtomicReferenceArray<E> table = this.table;
int index = hash & (table.length() - 1);
E first = table.get(index);
for (E e = first; e != null; e = e.getNext()) {
K entryKey = e.getKey();
if (e.getHash() == hash
&& entryKey != null
&& map.keyEquivalence.equivalent(key, entryKey)) {
V entryValue = e.getValue();
if (entryValue != null) {
// TODO(kak): Remove this branch
} else if (isCollected(e)) {
// TODO(kak): Remove this branch
} else {
return null;
}
++modCount;
E newFirst = removeFromChain(first, e);
newCount = this.count - 1;
table.set(index, newFirst);
this.count = newCount; // write-volatile
return entryValue;
}
}
return null;
} finally {
unlock();
}
}
boolean remove(Object key, int hash, Object value) {
lock();
try {
preWriteCleanup();
int newCount = this.count - 1;
AtomicReferenceArray<E> table = this.table;
int index = hash & (table.length() - 1);
E first = table.get(index);
for (E e = first; e != null; e = e.getNext()) {
K entryKey = e.getKey();
if (e.getHash() == hash
&& entryKey != null
&& map.keyEquivalence.equivalent(key, entryKey)) {
V entryValue = e.getValue();
boolean explicitRemoval = false;
if (map.valueEquivalence().equivalent(value, entryValue)) {
explicitRemoval = true;
} else if (isCollected(e)) {
// TODO(kak): Remove this branch
} else {
return false;
}
++modCount;
E newFirst = removeFromChain(first, e);
newCount = this.count - 1;
table.set(index, newFirst);
this.count = newCount; // write-volatile
return explicitRemoval;
}
}
return false;
} finally {
unlock();
}
}
void clear() {
if (count != 0) {
lock();
try {
AtomicReferenceArray<E> table = this.table;
for (int i = 0; i < table.length(); ++i) {
table.set(i, null);
}
maybeClearReferenceQueues();
readCount.set(0);
++modCount;
count = 0; // write-volatile
} finally {
unlock();
}
}
}
/**
* Removes an entry from within a table. All entries following the removed node can stay, but
* all preceding ones need to be cloned.
*
* <p>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("this")
E removeFromChain(E first, E entry) {
int newCount = count;
E newFirst = entry.getNext();
for (E e = first; e != entry; e = e.getNext()) {
E next = copyEntry(e, newFirst);
if (next != null) {
newFirst = next;
} else {
newCount--;
}
}
this.count = newCount;
return newFirst;
}
/** Removes an entry whose key has been garbage collected. */
@CanIgnoreReturnValue
boolean reclaimKey(E entry, int hash) {
lock();
try {
int newCount = count - 1;
AtomicReferenceArray<E> table = this.table;
int index = hash & (table.length() - 1);
E first = table.get(index);
for (E e = first; e != null; e = e.getNext()) {
if (e == entry) {
++modCount;
E newFirst = removeFromChain(first, e);
newCount = this.count - 1;
table.set(index, newFirst);
this.count = newCount; // write-volatile
return true;
}
}
return false;
} finally {
unlock();
}
}
/** Removes an entry whose value has been garbage collected. */
@CanIgnoreReturnValue
boolean reclaimValue(K key, int hash, WeakValueReference<K, V, E> valueReference) {
lock();
try {
int newCount = this.count - 1;
AtomicReferenceArray<E> table = this.table;
int index = hash & (table.length() - 1);
E first = table.get(index);
for (E e = first; e != null; e = e.getNext()) {
K entryKey = e.getKey();
if (e.getHash() == hash
&& entryKey != null
&& map.keyEquivalence.equivalent(key, entryKey)) {
WeakValueReference<K, V, E> v = ((WeakValueEntry<K, V, E>) e).getValueReference();
if (v == valueReference) {
++modCount;
E 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();
}
}
/** Clears a value that has not yet been set, and thus does not require count to be modified. */
@CanIgnoreReturnValue
boolean clearValueForTesting(
K key,
int hash,
WeakValueReference<K, V, ? extends InternalEntry<K, V, ?>> valueReference) {
lock();
try {
AtomicReferenceArray<E> table = this.table;
int index = hash & (table.length() - 1);
E first = table.get(index);
for (E e = first; e != null; e = e.getNext()) {
K entryKey = e.getKey();
if (e.getHash() == hash
&& entryKey != null
&& map.keyEquivalence.equivalent(key, entryKey)) {
WeakValueReference<K, V, E> v = ((WeakValueEntry<K, V, E>) e).getValueReference();
if (v == valueReference) {
E newFirst = removeFromChain(first, e);
table.set(index, newFirst);
return true;
}
return false;
}
}
return false;
} finally {
unlock();
}
}
@GuardedBy("this")
boolean removeEntryForTesting(E entry) {
int hash = entry.getHash();
int newCount = this.count - 1;
AtomicReferenceArray<E> table = this.table;
int index = hash & (table.length() - 1);
E first = table.get(index);
for (E e = first; e != null; e = e.getNext()) {
if (e == entry) {
++modCount;
E 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.
*/
static <K, V, E extends InternalEntry<K, V, E>> boolean isCollected(E entry) {
return entry.getValue() == null;
}
/**
* Gets the value from an entry. Returns {@code null} if the entry is invalid or
* partially-collected.
*/
@NullableDecl
V getLiveValue(E entry) {
if (entry.getKey() == null) {
tryDrainReferenceQueues();
return null;
}
V value = entry.getValue();
if (value == null) {
tryDrainReferenceQueues();
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.
*/
@GuardedBy("this")
void preWriteCleanup() {
runLockedCleanup();
}
void runCleanup() {
runLockedCleanup();
}
void runLockedCleanup() {
if (tryLock()) {
try {
maybeDrainReferenceQueues();
readCount.set(0);
} finally {
unlock();
}
}
}
}
/** Concrete implementation of {@link Segment} for strong keys and strong values. */
static final class StrongKeyStrongValueSegment<K, V>
extends Segment<K, V, StrongKeyStrongValueEntry<K, V>, StrongKeyStrongValueSegment<K, V>> {
StrongKeyStrongValueSegment(
MapMakerInternalMap<
K, V, StrongKeyStrongValueEntry<K, V>, StrongKeyStrongValueSegment<K, V>>
map,
int initialCapacity,
int maxSegmentSize) {
super(map, initialCapacity, maxSegmentSize);
}
@Override
StrongKeyStrongValueSegment<K, V> self() {
return this;
}
@SuppressWarnings("unchecked")
@Override
public StrongKeyStrongValueEntry<K, V> castForTesting(InternalEntry<K, V, ?> entry) {
return (StrongKeyStrongValueEntry<K, V>) entry;
}
}
/** Concrete implementation of {@link Segment} for strong keys and weak values. */
static final class StrongKeyWeakValueSegment<K, V>
extends Segment<K, V, StrongKeyWeakValueEntry<K, V>, StrongKeyWeakValueSegment<K, V>> {
private final ReferenceQueue<V> queueForValues = new ReferenceQueue<V>();
StrongKeyWeakValueSegment(
MapMakerInternalMap<K, V, StrongKeyWeakValueEntry<K, V>, StrongKeyWeakValueSegment<K, V>>
map,
int initialCapacity,
int maxSegmentSize) {
super(map, initialCapacity, maxSegmentSize);
}
@Override
StrongKeyWeakValueSegment<K, V> self() {
return this;
}
@Override
ReferenceQueue<V> getValueReferenceQueueForTesting() {
return queueForValues;
}
@SuppressWarnings("unchecked")
@Override
public StrongKeyWeakValueEntry<K, V> castForTesting(InternalEntry<K, V, ?> entry) {
return (StrongKeyWeakValueEntry<K, V>) entry;
}
@Override
public WeakValueReference<K, V, StrongKeyWeakValueEntry<K, V>> getWeakValueReferenceForTesting(
InternalEntry<K, V, ?> e) {
return castForTesting(e).getValueReference();
}
@Override
public WeakValueReference<K, V, StrongKeyWeakValueEntry<K, V>> newWeakValueReferenceForTesting(
InternalEntry<K, V, ?> e, V value) {
return new WeakValueReferenceImpl<>(queueForValues, value, castForTesting(e));
}
@Override
public void setWeakValueReferenceForTesting(
InternalEntry<K, V, ?> e,
WeakValueReference<K, V, ? extends InternalEntry<K, V, ?>> valueReference) {
StrongKeyWeakValueEntry<K, V> entry = castForTesting(e);
@SuppressWarnings("unchecked")
WeakValueReference<K, V, StrongKeyWeakValueEntry<K, V>> newValueReference =
(WeakValueReference<K, V, StrongKeyWeakValueEntry<K, V>>) valueReference;
WeakValueReference<K, V, StrongKeyWeakValueEntry<K, V>> previous = entry.valueReference;
entry.valueReference = newValueReference;
previous.clear();
}
@Override
void maybeDrainReferenceQueues() {
drainValueReferenceQueue(queueForValues);
}
@Override
void maybeClearReferenceQueues() {
clearReferenceQueue(queueForValues);
}
}
/** Concrete implementation of {@link Segment} for strong keys and {@link Dummy} values. */
static final class StrongKeyDummyValueSegment<K>
extends Segment<K, Dummy, StrongKeyDummyValueEntry<K>, StrongKeyDummyValueSegment<K>> {
StrongKeyDummyValueSegment(
MapMakerInternalMap<K, Dummy, StrongKeyDummyValueEntry<K>, StrongKeyDummyValueSegment<K>>
map,
int initialCapacity,
int maxSegmentSize) {
super(map, initialCapacity, maxSegmentSize);
}
@Override
StrongKeyDummyValueSegment<K> self() {
return this;
}
@SuppressWarnings("unchecked")
@Override
public StrongKeyDummyValueEntry<K> castForTesting(InternalEntry<K, Dummy, ?> entry) {
return (StrongKeyDummyValueEntry<K>) entry;
}
}
/** Concrete implementation of {@link Segment} for weak keys and strong values. */
static final class WeakKeyStrongValueSegment<K, V>
extends Segment<K, V, WeakKeyStrongValueEntry<K, V>, WeakKeyStrongValueSegment<K, V>> {
private final ReferenceQueue<K> queueForKeys = new ReferenceQueue<K>();
WeakKeyStrongValueSegment(
MapMakerInternalMap<K, V, WeakKeyStrongValueEntry<K, V>, WeakKeyStrongValueSegment<K, V>>
map,
int initialCapacity,
int maxSegmentSize) {
super(map, initialCapacity, maxSegmentSize);
}
@Override
WeakKeyStrongValueSegment<K, V> self() {
return this;
}
@Override
ReferenceQueue<K> getKeyReferenceQueueForTesting() {
return queueForKeys;
}
@SuppressWarnings("unchecked")
@Override
public WeakKeyStrongValueEntry<K, V> castForTesting(InternalEntry<K, V, ?> entry) {
return (WeakKeyStrongValueEntry<K, V>) entry;
}
@Override
void maybeDrainReferenceQueues() {
drainKeyReferenceQueue(queueForKeys);
}
@Override
void maybeClearReferenceQueues() {
clearReferenceQueue(queueForKeys);
}
}
/** Concrete implementation of {@link Segment} for weak keys and weak values. */
static final class WeakKeyWeakValueSegment<K, V>
extends Segment<K, V, WeakKeyWeakValueEntry<K, V>, WeakKeyWeakValueSegment<K, V>> {
private final ReferenceQueue<K> queueForKeys = new ReferenceQueue<K>();
private final ReferenceQueue<V> queueForValues = new ReferenceQueue<V>();
WeakKeyWeakValueSegment(
MapMakerInternalMap<K, V, WeakKeyWeakValueEntry<K, V>, WeakKeyWeakValueSegment<K, V>> map,
int initialCapacity,
int maxSegmentSize) {
super(map, initialCapacity, maxSegmentSize);
}
@Override
WeakKeyWeakValueSegment<K, V> self() {
return this;
}
@Override
ReferenceQueue<K> getKeyReferenceQueueForTesting() {
return queueForKeys;
}
@Override
ReferenceQueue<V> getValueReferenceQueueForTesting() {
return queueForValues;
}
@SuppressWarnings("unchecked")
@Override
public WeakKeyWeakValueEntry<K, V> castForTesting(InternalEntry<K, V, ?> entry) {
return (WeakKeyWeakValueEntry<K, V>) entry;
}
@Override
public WeakValueReference<K, V, WeakKeyWeakValueEntry<K, V>> getWeakValueReferenceForTesting(
InternalEntry<K, V, ?> e) {
return castForTesting(e).getValueReference();
}
@Override
public WeakValueReference<K, V, WeakKeyWeakValueEntry<K, V>> newWeakValueReferenceForTesting(
InternalEntry<K, V, ?> e, V value) {
return new WeakValueReferenceImpl<>(queueForValues, value, castForTesting(e));
}
@Override
public void setWeakValueReferenceForTesting(
InternalEntry<K, V, ?> e,
WeakValueReference<K, V, ? extends InternalEntry<K, V, ?>> valueReference) {
WeakKeyWeakValueEntry<K, V> entry = castForTesting(e);
@SuppressWarnings("unchecked")
WeakValueReference<K, V, WeakKeyWeakValueEntry<K, V>> newValueReference =
(WeakValueReference<K, V, WeakKeyWeakValueEntry<K, V>>) valueReference;
WeakValueReference<K, V, WeakKeyWeakValueEntry<K, V>> previous = entry.valueReference;
entry.valueReference = newValueReference;
previous.clear();
}
@Override
void maybeDrainReferenceQueues() {
drainKeyReferenceQueue(queueForKeys);
drainValueReferenceQueue(queueForValues);
}
@Override
void maybeClearReferenceQueues() {
clearReferenceQueue(queueForKeys);
}
}
/** Concrete implementation of {@link Segment} for weak keys and {@link Dummy} values. */
static final class WeakKeyDummyValueSegment<K>
extends Segment<K, Dummy, WeakKeyDummyValueEntry<K>, WeakKeyDummyValueSegment<K>> {
private final ReferenceQueue<K> queueForKeys = new ReferenceQueue<K>();
WeakKeyDummyValueSegment(
MapMakerInternalMap<K, Dummy, WeakKeyDummyValueEntry<K>, WeakKeyDummyValueSegment<K>> map,
int initialCapacity,
int maxSegmentSize) {
super(map, initialCapacity, maxSegmentSize);
}
@Override
WeakKeyDummyValueSegment<K> self() {
return this;
}
@Override
ReferenceQueue<K> getKeyReferenceQueueForTesting() {
return queueForKeys;
}
@SuppressWarnings("unchecked")
@Override
public WeakKeyDummyValueEntry<K> castForTesting(InternalEntry<K, Dummy, ?> entry) {
return (WeakKeyDummyValueEntry<K>) entry;
}
@Override
void maybeDrainReferenceQueues() {
drainKeyReferenceQueue(queueForKeys);
}
@Override
void maybeClearReferenceQueues() {
clearReferenceQueue(queueForKeys);
}
}
static final class CleanupMapTask implements Runnable {
final WeakReference<MapMakerInternalMap<?, ?, ?, ?>> mapReference;
public CleanupMapTask(MapMakerInternalMap<?, ?, ?, ?> map) {
this.mapReference = new WeakReference<MapMakerInternalMap<?, ?, ?, ?>>(map);
}
@Override
public void run() {
MapMakerInternalMap<?, ?, ?, ?> map = mapReference.get();
if (map == null) {
throw new CancellationException();
}
for (Segment<?, ?, ?, ?> segment : map.segments) {
segment.runCleanup();
}
}
}
@VisibleForTesting
Strength keyStrength() {
return entryHelper.keyStrength();
}
@VisibleForTesting
Strength valueStrength() {
return entryHelper.valueStrength();
}
@VisibleForTesting
Equivalence<Object> valueEquivalence() {
return entryHelper.valueStrength().defaultEquivalence();
}
// 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<K, V, E, S>[] 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;
}
return sum == 0L;
}
return true;
}
@Override
public int size() {
Segment<K, V, E, S>[] 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(@NullableDecl 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 or partially
* collected. Does not impact recency ordering.
*/
E getEntry(@NullableDecl Object key) {
if (key == null) {
return null;
}
int hash = hash(key);
return segmentFor(hash).getEntry(key, hash);
}
@Override
public boolean containsKey(@NullableDecl Object key) {
if (key == null) {
return false;
}
int hash = hash(key);
return segmentFor(hash).containsKey(key, hash);
}
@Override
public boolean containsValue(@NullableDecl 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<K, V, E, S>[] segments = this.segments;
long last = -1L;
for (int i = 0; i < CONTAINS_VALUE_RETRIES; i++) {
long sum = 0L;
for (Segment<K, V, E, S> segment : segments) {
// ensure visibility of most recent completed write
int unused = segment.count; // read-volatile
AtomicReferenceArray<E> table = segment.table;
for (int j = 0; j < table.length(); j++) {
for (E 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;
}
@CanIgnoreReturnValue
@Override
public V put(K key, V value) {
checkNotNull(key);
checkNotNull(value);
int hash = hash(key);
return segmentFor(hash).put(key, hash, value, false);
}
@CanIgnoreReturnValue
@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<? extends K, ? extends V> m) {
for (Entry<? extends K, ? extends V> e : m.entrySet()) {
put(e.getKey(), e.getValue());
}
}
@CanIgnoreReturnValue
@Override
public V remove(@NullableDecl Object key) {
if (key == null) {
return null;
}
int hash = hash(key);
return segmentFor(hash).remove(key, hash);
}
@CanIgnoreReturnValue
@Override
public boolean remove(@NullableDecl Object key, @NullableDecl Object value) {
if (key == null || value == null) {
return false;
}
int hash = hash(key);
return segmentFor(hash).remove(key, hash, value);
}
@CanIgnoreReturnValue
@Override
public boolean replace(K key, @NullableDecl 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);
}
@CanIgnoreReturnValue
@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<K, V, E, S> segment : segments) {
segment.clear();
}
}
@NullableDecl transient Set<K> keySet;
@Override
public Set<K> keySet() {
Set<K> ks = keySet;
return (ks != null) ? ks : (keySet = new KeySet());
}
@NullableDecl transient Collection<V> values;
@Override
public Collection<V> values() {
Collection<V> vs = values;
return (vs != null) ? vs : (values = new Values());
}
@NullableDecl transient Set<Entry<K, V>> entrySet;
@Override
public Set<Entry<K, V>> entrySet() {
Set<Entry<K, V>> es = entrySet;
return (es != null) ? es : (entrySet = new EntrySet());
}
// Iterator Support
abstract class HashIterator<T> implements Iterator<T> {
int nextSegmentIndex;
int nextTableIndex;
@NullableDecl Segment<K, V, E, S> currentSegment;
@NullableDecl AtomicReferenceArray<E> currentTable;
@NullableDecl E nextEntry;
@NullableDecl WriteThroughEntry nextExternal;
@NullableDecl WriteThroughEntry lastReturned;
HashIterator() {
nextSegmentIndex = segments.length - 1;
nextTableIndex = -1;
advance();
}
@Override
public abstract T 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(E 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();
}
}
@Override
public boolean hasNext() {
return nextExternal != null;
}
WriteThroughEntry nextEntry() {
if (nextExternal == null) {
throw new NoSuchElementException();
}
lastReturned = nextExternal;
advance();
return lastReturned;
}
@Override
public void remove() {
checkRemove(lastReturned != null);
MapMakerInternalMap.this.remove(lastReturned.getKey());
lastReturned = null;
}
}
final class KeyIterator extends HashIterator<K> {
@Override
public K next() {
return nextEntry().getKey();
}
}
final class ValueIterator extends HashIterator<V> {
@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<K, V> {
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(@NullableDecl 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<Entry<K, V>> {
@Override
public Entry<K, V> next() {
return nextEntry();
}
}
@WeakOuter
final class KeySet extends SafeToArraySet<K> {
@Override
public Iterator<K> 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();
}
}
@WeakOuter
final class Values extends AbstractCollection<V> {
@Override
public Iterator<V> 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();
}
// super.toArray() may misbehave if size() is inaccurate, at least on old versions of Android.
// https://code.google.com/p/android/issues/detail?id=36519 / http://r.android.com/47508
@Override
public Object[] toArray() {
return toArrayList(this).toArray();
}
@Override
public <T> T[] toArray(T[] a) {
return toArrayList(this).toArray(a);
}
}
@WeakOuter
final class EntrySet extends SafeToArraySet<Entry<K, V>> {
@Override
public Iterator<Entry<K, V>> 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();
}
}
private abstract static class SafeToArraySet<E> extends AbstractSet<E> {
// super.toArray() may misbehave if size() is inaccurate, at least on old versions of Android.
// https://code.google.com/p/android/issues/detail?id=36519 / http://r.android.com/47508
@Override
public Object[] toArray() {
return toArrayList(this).toArray();
}
@Override
public <T> T[] toArray(T[] a) {
return toArrayList(this).toArray(a);
}
}
private static <E> ArrayList<E> toArrayList(Collection<E> c) {
// Avoid calling ArrayList(Collection), which may call back into toArray.
ArrayList<E> result = new ArrayList<>(c.size());
Iterators.addAll(result, c.iterator());
return result;
}
// Serialization Support
private static final long serialVersionUID = 5;
Object writeReplace() {
return new SerializationProxy<>(
entryHelper.keyStrength(),
entryHelper.valueStrength(),
keyEquivalence,
entryHelper.valueStrength().defaultEquivalence(),
concurrencyLevel,
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<K, V> extends ForwardingConcurrentMap<K, V>
implements Serializable {
private static final long serialVersionUID = 3;
final Strength keyStrength;
final Strength valueStrength;
final Equivalence<Object> keyEquivalence;
final Equivalence<Object> valueEquivalence;
final int concurrencyLevel;
transient ConcurrentMap<K, V> delegate;
AbstractSerializationProxy(
Strength keyStrength,
Strength valueStrength,
Equivalence<Object> keyEquivalence,
Equivalence<Object> valueEquivalence,
int concurrencyLevel,
ConcurrentMap<K, V> delegate) {
this.keyStrength = keyStrength;
this.valueStrength = valueStrength;
this.keyEquivalence = keyEquivalence;
this.valueEquivalence = valueEquivalence;
this.concurrencyLevel = concurrencyLevel;
this.delegate = delegate;
}
@Override
protected ConcurrentMap<K, V> delegate() {
return delegate;
}
void writeMapTo(ObjectOutputStream out) throws IOException {
out.writeInt(delegate.size());
for (Entry<K, V> 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();
return new MapMaker()
.initialCapacity(size)
.setKeyStrength(keyStrength)
.setValueStrength(valueStrength)
.keyEquivalence(keyEquivalence)
.concurrencyLevel(concurrencyLevel);
}
@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<K, V> extends AbstractSerializationProxy<K, V> {
private static final long serialVersionUID = 3;
SerializationProxy(
Strength keyStrength,
Strength valueStrength,
Equivalence<Object> keyEquivalence,
Equivalence<Object> valueEquivalence,
int concurrencyLevel,
ConcurrentMap<K, V> delegate) {
super(
keyStrength, valueStrength, keyEquivalence, valueEquivalence, concurrencyLevel, 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;
}
}
}