LocalCache.java
/*
* 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 org.glassfish.jersey.internal.guava;
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.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.ConcurrentLinkedQueue;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicReferenceArray;
import java.util.concurrent.locks.ReentrantLock;
import java.util.function.Function;
import java.util.logging.Level;
import java.util.logging.Logger;
import static org.glassfish.jersey.internal.guava.MoreExecutors.directExecutor;
import static org.glassfish.jersey.internal.guava.Preconditions.checkNotNull;
import static org.glassfish.jersey.internal.guava.Preconditions.checkState;
import static org.glassfish.jersey.internal.guava.Uninterruptibles.getUninterruptibly;
import static java.util.concurrent.TimeUnit.NANOSECONDS;
/**
* The concurrent hash map implementation built by {@link CacheBuilder}.
* <p>
* <p>This implementation is heavily derived from revision 1.96 of <a
* href="http://tinyurl.com/ConcurrentHashMap">ConcurrentHashMap.java</a>.
*
* @author Charles Fry
* @author Bob Lee ({@code org.glassfish.jersey.internal.guava.MapMaker})
* @author Doug Lea ({@code ConcurrentHashMap})
*/
class LocalCache<K, V> extends AbstractMap<K, V> implements ConcurrentMap<K, V> {
/*
* 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.
*/
private static final int MAXIMUM_CAPACITY = 1 << 30;
/**
* The maximum number of segments to allow; used to bound constructor arguments.
*/
private static final int MAX_SEGMENTS = 1 << 16; // slightly conservative
/**
* Number of (unsynchronized) retries in the containsValue method.
*/
private 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>
* <p>This must be a (2^n)-1 as it is used as a mask.
*/
private 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
private static final int DRAIN_MAX = 16;
// Fields
private static final Logger logger = Logger.getLogger(LocalCache.class.getName());
/**
* Placeholder. Indicates that the value hasn't been set yet.
*/
private static final ValueReference<Object, Object> UNSET = new ValueReference<Object, Object>() {
@Override
public Object get() {
return null;
}
@Override
public int getWeight() {
return 0;
}
@Override
public ReferenceEntry<Object, Object> getEntry() {
return null;
}
@Override
public ValueReference<Object, Object> copyFor(ReferenceQueue<Object> queue,
Object value, ReferenceEntry<Object, Object> entry) {
return this;
}
@Override
public boolean isLoading() {
return false;
}
@Override
public boolean isActive() {
return false;
}
@Override
public Object waitForValue() {
return null;
}
@Override
public void notifyNewValue(Object newValue) {
}
};
private static final Queue<?> DISCARDING_QUEUE = new AbstractQueue<Object>() {
@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<Object> iterator() {
return Iterators.emptyIterator();
}
};
/**
* Mask value for indexing into segments. The upper bits of a key's hash code are used to choose
* the segment.
*/
private final 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.
*/
private final int segmentShift;
/**
* The segments, each of which is a specialized hash table.
*/
private final Segment<K, V>[] segments;
/**
* The concurrency level.
*/
private final int concurrencyLevel;
/**
* Strategy for comparing keys.
*/
private final Equivalence<Object> keyEquivalence;
/**
* Strategy for comparing values.
*/
private final Equivalence<Object> valueEquivalence;
/**
* Strategy for referencing keys.
*/
private final Strength keyStrength;
/**
* Strategy for referencing values.
*/
private final Strength valueStrength;
/**
* The maximum weight of this map. UNSET_INT if there is no maximum.
*/
private final long maxWeight;
/**
* How long after the last access to an entry the map will retain that entry.
*/
private final long expireAfterAccessNanos;
/**
* How long after the last write to an entry the map will retain that entry.
*/
private final long expireAfterWriteNanos;
/**
* How long after the last write an entry becomes a candidate for refresh.
*/
private final long refreshNanos;
/**
* Entries waiting to be consumed by the removal listener.
*/
// TODO(fry): define a new type which creates event objects and automates the clear logic
private final Queue<RemovalNotification<K, V>> removalNotificationQueue;
/**
* Measures time in a testable way.
*/
private final Ticker ticker;
/**
* Factory used to create new entries.
*/
private final EntryFactory entryFactory;
/**
* The default cache loader to use on loading operations.
*/
private final CacheLoader<? super K, V> defaultLoader;
private Set<K> keySet;
private Collection<V> values;
private Set<Entry<K, V>> entrySet;
/**
* Creates a new, empty map with the specified strategy, initial capacity and concurrency level.
*/
private LocalCache(
CacheBuilder<? super K, ? super V> builder, CacheLoader<? super K, V> loader) {
concurrencyLevel = Math.min(builder.getConcurrencyLevel(), MAX_SEGMENTS);
keyStrength = Strength.STRONG;
valueStrength = Strength.STRONG;
keyEquivalence = keyStrength.defaultEquivalence();
valueEquivalence = valueStrength.defaultEquivalence();
maxWeight = CacheBuilder.UNSET_INT;
expireAfterAccessNanos = builder.getExpireAfterAccessNanos();
expireAfterWriteNanos = CacheBuilder.DEFAULT_EXPIRATION_NANOS;
refreshNanos = CacheBuilder.DEFAULT_REFRESH_NANOS;
removalNotificationQueue = LocalCache.discardingQueue();
ticker = recordsTime() ? Ticker.systemTicker() : CacheBuilder.NULL_TICKER;
entryFactory = EntryFactory.getFactory(keyStrength, usesAccessEntries(), usesWriteEntries());
defaultLoader = loader;
int initialCapacity = Math.min(CacheBuilder.DEFAULT_INITIAL_CAPACITY, MAXIMUM_CAPACITY);
if (evictsBySize()) {
initialCapacity = Math.min(initialCapacity, (int) maxWeight);
}
// Find the lowest power-of-two segmentCount that exceeds concurrencyLevel, unless
// maximumSize/Weight is specified in which case ensure that each segment gets at least 10
// entries. The special casing for size-based eviction is only necessary because that eviction
// happens per segment instead of globally, so too many segments compared to the maximum size
// will result in random eviction behavior.
int segmentShift = 0;
int segmentCount = 1;
while (segmentCount < concurrencyLevel
&& (!evictsBySize() || segmentCount * 20 <= maxWeight)) {
++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 weights = overall max weights
long maxSegmentWeight = maxWeight / segmentCount + 1;
long remainder = maxWeight % segmentCount;
for (int i = 0; i < this.segments.length; ++i) {
if (i == remainder) {
maxSegmentWeight--;
}
this.segments[i] =
createSegment(segmentSize, maxSegmentWeight);
}
} else {
for (int i = 0; i < this.segments.length; ++i) {
this.segments[i] =
createSegment(segmentSize, CacheBuilder.UNSET_INT);
}
}
}
/**
* Singleton placeholder that indicates a value is being loaded.
*/
@SuppressWarnings("unchecked") // impl never uses a parameter or returns any non-null value
private static <K, V> ValueReference<K, V> unset() {
return (ValueReference<K, V>) UNSET;
}
@SuppressWarnings("unchecked") // impl never uses a parameter or returns any non-null value
private static <K, V> ReferenceEntry<K, V> nullEntry() {
return (ReferenceEntry<K, V>) NullEntry.INSTANCE;
}
/**
* Queue that discards all elements.
*/
@SuppressWarnings("unchecked") // impl never uses a parameter or returns any non-null value
private static <E> Queue<E> discardingQueue() {
return (Queue) DISCARDING_QUEUE;
}
/**
* 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
*/
private 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);
}
// Guarded By Segment.this
private static <K, V> void connectAccessOrder(ReferenceEntry<K, V> previous, ReferenceEntry<K, V> next) {
previous.setNextInAccessQueue(next);
next.setPreviousInAccessQueue(previous);
}
// Guarded By Segment.this
private static <K, V> void nullifyAccessOrder(ReferenceEntry<K, V> nulled) {
ReferenceEntry<K, V> nullEntry = nullEntry();
nulled.setNextInAccessQueue(nullEntry);
nulled.setPreviousInAccessQueue(nullEntry);
}
// Guarded By Segment.this
private static <K, V> void connectWriteOrder(ReferenceEntry<K, V> previous, ReferenceEntry<K, V> next) {
previous.setNextInWriteQueue(next);
next.setPreviousInWriteQueue(previous);
}
// Guarded By Segment.this
private static <K, V> void nullifyWriteOrder(ReferenceEntry<K, V> nulled) {
ReferenceEntry<K, V> nullEntry = nullEntry();
nulled.setNextInWriteQueue(nullEntry);
nulled.setPreviousInWriteQueue(nullEntry);
}
boolean evictsBySize() {
return maxWeight >= 0;
}
private boolean expiresAfterWrite() {
return expireAfterWriteNanos > 0;
}
private boolean expiresAfterAccess() {
return expireAfterAccessNanos > 0;
}
boolean refreshes() {
return refreshNanos > 0;
}
boolean usesAccessQueue() {
return expiresAfterAccess() || evictsBySize();
}
boolean usesWriteQueue() {
return expiresAfterWrite();
}
boolean recordsWrite() {
return expiresAfterWrite() || refreshes();
}
boolean recordsAccess() {
return expiresAfterAccess();
}
private boolean recordsTime() {
return recordsWrite() || recordsAccess();
}
private boolean usesWriteEntries() {
return usesWriteQueue() || recordsWrite();
}
private boolean usesAccessEntries() {
return usesAccessQueue() || recordsAccess();
}
/*
* 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.
*/
boolean usesKeyReferences() {
return keyStrength != Strength.STRONG;
}
boolean usesValueReferences() {
return valueStrength != Strength.STRONG;
}
private int hash(Object key) {
int h = keyEquivalence.hash(key);
return rehash(h);
}
void reclaimValue(ValueReference<K, V> valueReference) {
ReferenceEntry<K, V> entry = valueReference.getEntry();
int hash = entry.getHash();
segmentFor(hash).reclaimValue(entry.getKey(), hash, valueReference);
}
void reclaimKey(ReferenceEntry<K, V> entry) {
int hash = entry.getHash();
segmentFor(hash).reclaimKey(entry, hash);
}
/**
* 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
*/
private Segment<K, V> segmentFor(int hash) {
// TODO(fry): Lazily create segments?
return segments[(hash >>> segmentShift) & segmentMask];
}
private Segment<K, V> createSegment(
int initialCapacity, long maxSegmentWeight) {
return new Segment<K, V>(this, initialCapacity, maxSegmentWeight);
}
/**
* Gets the value from an entry. Returns null if the entry is invalid, partially-collected,
* loading, or expired. Unlike {@link Segment#getLiveValue} this method does not attempt to
* cleanup stale entries. As such it should only be called outside of a segment context, such as
* during iteration.
*/
private V getLiveValue(ReferenceEntry<K, V> entry, long now) {
if (entry.getKey() == null) {
return null;
}
V value = entry.getValueReference().get();
if (value == null) {
return null;
}
if (isExpired(entry, now)) {
return null;
}
return value;
}
/**
* Returns true if the entry has expired.
*/
boolean isExpired(ReferenceEntry<K, V> entry, long now) {
checkNotNull(entry);
if (expiresAfterAccess()
&& (now - entry.getAccessTime() >= expireAfterAccessNanos)) {
return true;
}
if (expiresAfterWrite()
&& (now - entry.getWriteTime() >= expireAfterWriteNanos)) {
return true;
}
return false;
}
@SuppressWarnings("unchecked")
private Segment<K, V>[] newSegmentArray(int ssize) {
return new Segment[ssize];
}
@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>[] 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;
}
private long longSize() {
Segment<K, V>[] segments = this.segments;
long sum = 0;
for (int i = 0; i < segments.length; ++i) {
sum += segments[i].count;
}
return sum;
}
@Override
public int size() {
return Ints.saturatedCast(longSize());
}
@Override
public V get(Object key) {
if (key == null) {
return null;
}
int hash = hash(key);
return segmentFor(hash).get(key, hash);
}
V getIfPresent(Object key) {
int hash = hash(checkNotNull(key));
return segmentFor(hash).get(key, hash);
}
private V get(K key, CacheLoader<? super K, V> loader) throws ExecutionException {
int hash = hash(checkNotNull(key));
return segmentFor(hash).get(key, hash, loader);
}
V getOrLoad(K key) throws ExecutionException {
return get(key, defaultLoader);
}
@Override
public boolean containsKey(Object key) {
// does not impact recency ordering
if (key == null) {
return false;
}
int hash = hash(key);
return segmentFor(hash).containsKey(key, hash);
}
@Override
public boolean containsValue(Object value) {
// does not impact recency ordering
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.
long now = ticker.read();
final Segment<K, V>[] segments = this.segments;
long last = -1L;
for (int i = 0; i < CONTAINS_VALUE_RETRIES; i++) {
long sum = 0L;
for (Segment<K, V> segment : segments) {
// ensure visibility of most recent completed write
@SuppressWarnings({"UnusedDeclaration", "unused"})
int c = segment.count; // read-volatile
AtomicReferenceArray<ReferenceEntry<K, V>> table = segment.table;
for (int j = 0; j < table.length(); j++) {
for (ReferenceEntry<K, V> e = table.get(j); e != null; e = e.getNext()) {
V v = segment.getLiveValue(e, now);
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);
}
// expiration
@Override
public V putIfAbsent(K key, V value) {
checkNotNull(key);
checkNotNull(value);
int hash = hash(key);
return segmentFor(hash).put(key, hash, value, true);
}
// queues
@Override
public void putAll(Map<? extends K, ? extends V> m) {
for (Entry<? extends K, ? extends V> e : m.entrySet()) {
put(e.getKey(), e.getValue());
}
}
@Override
public V remove(Object key) {
if (key == null) {
return null;
}
int hash = hash(key);
return segmentFor(hash).remove(key, hash);
}
@Override
public boolean remove(Object key, 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, 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<K, V> segment : segments) {
segment.clear();
}
}
// Inner Classes
@Override
public Set<K> keySet() {
// does not impact recency ordering
Set<K> ks = keySet;
return (ks != null) ? ks : (keySet = new KeySet(this));
}
@Override
public Collection<V> values() {
// does not impact recency ordering
Collection<V> vs = values;
return (vs != null) ? vs : (values = new Values(this));
}
// Queues
@Override
public Set<Entry<K, V>> entrySet() {
// does not impact recency ordering
Set<Entry<K, V>> es = entrySet;
return (es != null) ? es : (entrySet = new EntrySet(this));
}
enum Strength {
/*
* TODO(kevinb): If we strongly reference the value and aren't loading, we needn't wrap the
* value. This could save ~8 bytes per entry.
*/
STRONG {
@Override
<K, V> ValueReference<K, V> referenceValue(
Segment<K, V> segment, ReferenceEntry<K, V> entry, V value, int weight) {
return (weight == 1)
? new StrongValueReference<K, V>(value)
: new WeightedStrongValueReference<K, V>(value, weight);
}
@Override
Equivalence<Object> defaultEquivalence() {
return Equivalence.equals();
}
},
WEAK {
@Override
<K, V> ValueReference<K, V> referenceValue(
Segment<K, V> segment, ReferenceEntry<K, V> entry, V value, int weight) {
return (weight == 1)
? new WeakValueReference<K, V>(segment.valueReferenceQueue, value, entry)
: new WeightedWeakValueReference<K, V>(
segment.valueReferenceQueue, value, entry, weight);
}
@Override
Equivalence<Object> defaultEquivalence() {
return Equivalence.identity();
}
};
/**
* Creates a reference for the given value according to this value strength.
*/
abstract <K, V> ValueReference<K, V> referenceValue(
Segment<K, V> segment, ReferenceEntry<K, V> entry, V value, int weight);
/**
* 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();
}
// Cache support
// ConcurrentMap methods
/**
* Creates new entries.
*/
enum EntryFactory {
STRONG {
@Override
<K, V> ReferenceEntry<K, V> newEntry(
Segment<K, V> segment, K key, int hash, ReferenceEntry<K, V> next) {
return new StrongEntry<K, V>(key, hash, next);
}
},
STRONG_ACCESS {
@Override
<K, V> ReferenceEntry<K, V> newEntry(
Segment<K, V> segment, K key, int hash, ReferenceEntry<K, V> next) {
return new StrongAccessEntry<K, V>(key, hash, next);
}
@Override
<K, V> ReferenceEntry<K, V> copyEntry(
Segment<K, V> segment, ReferenceEntry<K, V> original, ReferenceEntry<K, V> newNext) {
ReferenceEntry<K, V> newEntry = super.copyEntry(segment, original, newNext);
copyAccessEntry(original, newEntry);
return newEntry;
}
},
STRONG_WRITE {
@Override
<K, V> ReferenceEntry<K, V> newEntry(
Segment<K, V> segment, K key, int hash, ReferenceEntry<K, V> next) {
return new StrongWriteEntry<K, V>(key, hash, next);
}
@Override
<K, V> ReferenceEntry<K, V> copyEntry(
Segment<K, V> segment, ReferenceEntry<K, V> original, ReferenceEntry<K, V> newNext) {
ReferenceEntry<K, V> newEntry = super.copyEntry(segment, original, newNext);
copyWriteEntry(original, newEntry);
return newEntry;
}
},
STRONG_ACCESS_WRITE {
@Override
<K, V> ReferenceEntry<K, V> newEntry(
Segment<K, V> segment, K key, int hash, ReferenceEntry<K, V> next) {
return new StrongAccessWriteEntry<K, V>(key, hash, next);
}
@Override
<K, V> ReferenceEntry<K, V> copyEntry(
Segment<K, V> segment, ReferenceEntry<K, V> original, ReferenceEntry<K, V> newNext) {
ReferenceEntry<K, V> newEntry = super.copyEntry(segment, original, newNext);
copyAccessEntry(original, newEntry);
copyWriteEntry(original, newEntry);
return newEntry;
}
},
WEAK {
@Override
<K, V> ReferenceEntry<K, V> newEntry(
Segment<K, V> segment, K key, int hash, ReferenceEntry<K, V> next) {
return new WeakEntry<K, V>(segment.keyReferenceQueue, key, hash, next);
}
},
WEAK_ACCESS {
@Override
<K, V> ReferenceEntry<K, V> newEntry(
Segment<K, V> segment, K key, int hash, ReferenceEntry<K, V> next) {
return new WeakAccessEntry<K, V>(segment.keyReferenceQueue, key, hash, next);
}
@Override
<K, V> ReferenceEntry<K, V> copyEntry(
Segment<K, V> segment, ReferenceEntry<K, V> original, ReferenceEntry<K, V> newNext) {
ReferenceEntry<K, V> newEntry = super.copyEntry(segment, original, newNext);
copyAccessEntry(original, newEntry);
return newEntry;
}
},
WEAK_WRITE {
@Override
<K, V> ReferenceEntry<K, V> newEntry(
Segment<K, V> segment, K key, int hash, ReferenceEntry<K, V> next) {
return new WeakWriteEntry<K, V>(segment.keyReferenceQueue, key, hash, next);
}
@Override
<K, V> ReferenceEntry<K, V> copyEntry(
Segment<K, V> segment, ReferenceEntry<K, V> original, ReferenceEntry<K, V> newNext) {
ReferenceEntry<K, V> newEntry = super.copyEntry(segment, original, newNext);
copyWriteEntry(original, newEntry);
return newEntry;
}
},
WEAK_ACCESS_WRITE {
@Override
<K, V> ReferenceEntry<K, V> newEntry(
Segment<K, V> segment, K key, int hash, ReferenceEntry<K, V> next) {
return new WeakAccessWriteEntry<K, V>(segment.keyReferenceQueue, key, hash, next);
}
@Override
<K, V> ReferenceEntry<K, V> copyEntry(
Segment<K, V> segment, ReferenceEntry<K, V> original, ReferenceEntry<K, V> newNext) {
ReferenceEntry<K, V> newEntry = super.copyEntry(segment, original, newNext);
copyAccessEntry(original, newEntry);
copyWriteEntry(original, newEntry);
return newEntry;
}
};
/**
* Masks used to compute indices in the following table.
*/
static final int ACCESS_MASK = 1;
static final int WRITE_MASK = 2;
static final int WEAK_MASK = 4;
/**
* Look-up table for factories.
*/
static final EntryFactory[] factories = {
STRONG, STRONG_ACCESS, STRONG_WRITE, STRONG_ACCESS_WRITE,
WEAK, WEAK_ACCESS, WEAK_WRITE, WEAK_ACCESS_WRITE,
};
static EntryFactory getFactory(Strength keyStrength, boolean usesAccessQueue,
boolean usesWriteQueue) {
int flags = ((keyStrength == Strength.WEAK) ? WEAK_MASK : 0)
| (usesAccessQueue ? ACCESS_MASK : 0)
| (usesWriteQueue ? WRITE_MASK : 0);
return factories[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 <K, V> ReferenceEntry<K, V> newEntry(
Segment<K, V> segment, K key, int hash, ReferenceEntry<K, V> next);
/**
* Copies an entry, assigning it a new {@code next} entry.
*
* @param original the entry to copy
* @param newNext entry in the same bucket
*/
// Guarded By Segment.this
<K, V> ReferenceEntry<K, V> copyEntry(
Segment<K, V> segment, ReferenceEntry<K, V> original, ReferenceEntry<K, V> newNext) {
return newEntry(segment, original.getKey(), original.getHash(), newNext);
}
// Guarded By Segment.this
<K, V> void copyAccessEntry(ReferenceEntry<K, V> original, ReferenceEntry<K, V> newEntry) {
// TODO(fry): when we link values instead of entries this method can go
// away, as can connectAccessOrder, nullifyAccessOrder.
newEntry.setAccessTime(original.getAccessTime());
connectAccessOrder(original.getPreviousInAccessQueue(), newEntry);
connectAccessOrder(newEntry, original.getNextInAccessQueue());
nullifyAccessOrder(original);
}
// Guarded By Segment.this
<K, V> void copyWriteEntry(ReferenceEntry<K, V> original, ReferenceEntry<K, V> newEntry) {
// TODO(fry): when we link values instead of entries this method can go
// away, as can connectWriteOrder, nullifyWriteOrder.
newEntry.setWriteTime(original.getWriteTime());
connectWriteOrder(original.getPreviousInWriteQueue(), newEntry);
connectWriteOrder(newEntry, original.getNextInWriteQueue());
nullifyWriteOrder(original);
}
}
private enum NullEntry implements ReferenceEntry<Object, Object> {
INSTANCE;
@Override
public ValueReference<Object, Object> getValueReference() {
return null;
}
@Override
public void setValueReference(ValueReference<Object, Object> valueReference) {
}
@Override
public ReferenceEntry<Object, Object> getNext() {
return null;
}
@Override
public int getHash() {
return 0;
}
@Override
public Object getKey() {
return null;
}
@Override
public long getAccessTime() {
return 0;
}
@Override
public void setAccessTime(long time) {
}
@Override
public ReferenceEntry<Object, Object> getNextInAccessQueue() {
return this;
}
@Override
public void setNextInAccessQueue(ReferenceEntry<Object, Object> next) {
}
@Override
public ReferenceEntry<Object, Object> getPreviousInAccessQueue() {
return this;
}
@Override
public void setPreviousInAccessQueue(ReferenceEntry<Object, Object> previous) {
}
@Override
public long getWriteTime() {
return 0;
}
@Override
public void setWriteTime(long time) {
}
@Override
public ReferenceEntry<Object, Object> getNextInWriteQueue() {
return this;
}
@Override
public void setNextInWriteQueue(ReferenceEntry<Object, Object> next) {
}
@Override
public ReferenceEntry<Object, Object> getPreviousInWriteQueue() {
return this;
}
@Override
public void setPreviousInWriteQueue(ReferenceEntry<Object, Object> previous) {
}
}
/**
* A reference to a value.
*/
interface ValueReference<K, V> {
/**
* Returns the value. Does not block or throw exceptions.
*/
V get();
/**
* Waits for a value that may still be loading. Unlike get(), this method can block (in the
* case of FutureValueReference).
*
* @throws ExecutionException if the loading thread throws an exception
* @throws ExecutionError if the loading thread throws an error
*/
V waitForValue() throws ExecutionException;
/**
* Returns the weight of this entry. This is assumed to be static between calls to setValue.
*/
int getWeight();
/**
* Returns the entry associated with this value reference, or {@code null} if this value
* reference is independent of any entry.
*/
ReferenceEntry<K, V> getEntry();
/**
* Creates a copy of this reference for the given entry.
* <p>
* <p>{@code value} may be null only for a loading reference.
*/
ValueReference<K, V> copyFor(
ReferenceQueue<V> queue, V value, ReferenceEntry<K, V> entry);
/**
* Notifify pending loads that a new value was set. This is only relevant to loading
* value references.
*/
void notifyNewValue(V newValue);
/**
* Returns true if a new value is currently loading, regardless of whether or not there is an
* existing value. It is assumed that the return value of this method is constant for any given
* ValueReference instance.
*/
boolean isLoading();
/**
* Returns true if this reference contains an active value, meaning one that is still considered
* present in the cache. Active values consist of live values, which are returned by cache
* lookups, and dead values, which have been evicted but awaiting removal. Non-active values
* consist strictly of loading values, though during refresh a value may be both active and
* loading.
*/
boolean isActive();
}
/**
* An entry in a reference map.
* <p>
* Entries in the map can be in the following states:
* <p>
* Valid:
* - Live: valid key/value are set
* - Loading: loading is pending
* <p>
* Invalid:
* - Expired: time expired (key/value may still be set)
* - Collected: key/value was partially collected, but not yet cleaned up
* - Unset: marked as unset, awaiting cleanup or reuse
*/
interface ReferenceEntry<K, V> {
/**
* Returns the value reference from this entry.
*/
ValueReference<K, V> getValueReference();
/**
* Sets the value reference for this entry.
*/
void setValueReference(ValueReference<K, V> valueReference);
/**
* Returns the next entry in the chain.
*/
ReferenceEntry<K, V> getNext();
/**
* Returns the entry's hash.
*/
int getHash();
/**
* Returns the key for this entry.
*/
K getKey();
/*
* Used by entries that use access order. Access 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.
*/
/**
* Returns the time that this entry was last accessed, in ns.
*/
long getAccessTime();
/**
* Sets the entry access time in ns.
*/
void setAccessTime(long time);
/**
* Returns the next entry in the access queue.
*/
ReferenceEntry<K, V> getNextInAccessQueue();
/**
* Sets the next entry in the access queue.
*/
void setNextInAccessQueue(ReferenceEntry<K, V> next);
/**
* Returns the previous entry in the access queue.
*/
ReferenceEntry<K, V> getPreviousInAccessQueue();
/**
* Sets the previous entry in the access queue.
*/
void setPreviousInAccessQueue(ReferenceEntry<K, V> previous);
/*
* Implemented by entries that use write order. Write 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.
*/
/**
* Returns the time that this entry was last written, in ns.
*/
long getWriteTime();
/**
* Sets the entry write time in ns.
*/
void setWriteTime(long time);
/**
* Returns the next entry in the write queue.
*/
ReferenceEntry<K, V> getNextInWriteQueue();
/**
* Sets the next entry in the write queue.
*/
void setNextInWriteQueue(ReferenceEntry<K, V> next);
/**
* Returns the previous entry in the write queue.
*/
ReferenceEntry<K, V> getPreviousInWriteQueue();
/**
* Sets the previous entry in the write queue.
*/
void setPreviousInWriteQueue(ReferenceEntry<K, V> previous);
}
abstract static class AbstractReferenceEntry<K, V> implements ReferenceEntry<K, V> {
@Override
public ValueReference<K, V> getValueReference() {
throw new UnsupportedOperationException();
}
@Override
public void setValueReference(ValueReference<K, V> valueReference) {
throw new UnsupportedOperationException();
}
@Override
public ReferenceEntry<K, V> getNext() {
throw new UnsupportedOperationException();
}
@Override
public int getHash() {
throw new UnsupportedOperationException();
}
@Override
public K getKey() {
throw new UnsupportedOperationException();
}
@Override
public long getAccessTime() {
throw new UnsupportedOperationException();
}
@Override
public void setAccessTime(long time) {
throw new UnsupportedOperationException();
}
@Override
public ReferenceEntry<K, V> getNextInAccessQueue() {
throw new UnsupportedOperationException();
}
@Override
public void setNextInAccessQueue(ReferenceEntry<K, V> next) {
throw new UnsupportedOperationException();
}
@Override
public ReferenceEntry<K, V> getPreviousInAccessQueue() {
throw new UnsupportedOperationException();
}
@Override
public void setPreviousInAccessQueue(ReferenceEntry<K, V> previous) {
throw new UnsupportedOperationException();
}
@Override
public long getWriteTime() {
throw new UnsupportedOperationException();
}
@Override
public void setWriteTime(long time) {
throw new UnsupportedOperationException();
}
@Override
public ReferenceEntry<K, V> getNextInWriteQueue() {
throw new UnsupportedOperationException();
}
@Override
public void setNextInWriteQueue(ReferenceEntry<K, V> next) {
throw new UnsupportedOperationException();
}
@Override
public ReferenceEntry<K, V> getPreviousInWriteQueue() {
throw new UnsupportedOperationException();
}
@Override
public void setPreviousInWriteQueue(ReferenceEntry<K, V> previous) {
throw new UnsupportedOperationException();
}
}
/**
* Used for strongly-referenced keys.
*/
static class StrongEntry<K, V> extends AbstractReferenceEntry<K, V> {
final K key;
final int hash;
final ReferenceEntry<K, V> next;
// The code below is exactly the same for each entry type.
volatile ValueReference<K, V> valueReference = unset();
StrongEntry(K key, int hash, ReferenceEntry<K, V> next) {
this.key = key;
this.hash = hash;
this.next = next;
}
@Override
public K getKey() {
return this.key;
}
@Override
public ValueReference<K, V> getValueReference() {
return valueReference;
}
@Override
public void setValueReference(ValueReference<K, V> valueReference) {
this.valueReference = valueReference;
}
@Override
public int getHash() {
return hash;
}
@Override
public ReferenceEntry<K, V> getNext() {
return next;
}
}
static final class StrongAccessEntry<K, V> extends StrongEntry<K, V> {
volatile long accessTime = Long.MAX_VALUE;
// The code below is exactly the same for each access entry type.
// Guarded By Segment.this
ReferenceEntry<K, V> nextAccess = nullEntry();
// Guarded By Segment.this
ReferenceEntry<K, V> previousAccess = nullEntry();
StrongAccessEntry(K key, int hash, ReferenceEntry<K, V> next) {
super(key, hash, next);
}
@Override
public long getAccessTime() {
return accessTime;
}
@Override
public void setAccessTime(long time) {
this.accessTime = time;
}
@Override
public ReferenceEntry<K, V> getNextInAccessQueue() {
return nextAccess;
}
@Override
public void setNextInAccessQueue(ReferenceEntry<K, V> next) {
this.nextAccess = next;
}
@Override
public ReferenceEntry<K, V> getPreviousInAccessQueue() {
return previousAccess;
}
@Override
public void setPreviousInAccessQueue(ReferenceEntry<K, V> previous) {
this.previousAccess = previous;
}
}
static final class StrongWriteEntry<K, V> extends StrongEntry<K, V> {
volatile long writeTime = Long.MAX_VALUE;
// The code below is exactly the same for each write entry type.
// Guarded By Segment.this
ReferenceEntry<K, V> nextWrite = nullEntry();
// Guarded By Segment.this
ReferenceEntry<K, V> previousWrite = nullEntry();
StrongWriteEntry(K key, int hash, ReferenceEntry<K, V> next) {
super(key, hash, next);
}
@Override
public long getWriteTime() {
return writeTime;
}
@Override
public void setWriteTime(long time) {
this.writeTime = time;
}
@Override
public ReferenceEntry<K, V> getNextInWriteQueue() {
return nextWrite;
}
@Override
public void setNextInWriteQueue(ReferenceEntry<K, V> next) {
this.nextWrite = next;
}
@Override
public ReferenceEntry<K, V> getPreviousInWriteQueue() {
return previousWrite;
}
@Override
public void setPreviousInWriteQueue(ReferenceEntry<K, V> previous) {
this.previousWrite = previous;
}
}
static final class StrongAccessWriteEntry<K, V> extends StrongEntry<K, V> {
volatile long accessTime = Long.MAX_VALUE;
// The code below is exactly the same for each access entry type.
// Guarded By Segment.this
ReferenceEntry<K, V> nextAccess = nullEntry();
// Guarded By Segment.this
ReferenceEntry<K, V> previousAccess = nullEntry();
volatile long writeTime = Long.MAX_VALUE;
// Guarded By Segment.this
ReferenceEntry<K, V> nextWrite = nullEntry();
// Guarded By Segment.this
ReferenceEntry<K, V> previousWrite = nullEntry();
StrongAccessWriteEntry(K key, int hash, ReferenceEntry<K, V> next) {
super(key, hash, next);
}
@Override
public long getAccessTime() {
return accessTime;
}
@Override
public void setAccessTime(long time) {
this.accessTime = time;
}
@Override
public ReferenceEntry<K, V> getNextInAccessQueue() {
return nextAccess;
}
// The code below is exactly the same for each write entry type.
@Override
public void setNextInAccessQueue(ReferenceEntry<K, V> next) {
this.nextAccess = next;
}
@Override
public ReferenceEntry<K, V> getPreviousInAccessQueue() {
return previousAccess;
}
@Override
public void setPreviousInAccessQueue(ReferenceEntry<K, V> previous) {
this.previousAccess = previous;
}
@Override
public long getWriteTime() {
return writeTime;
}
@Override
public void setWriteTime(long time) {
this.writeTime = time;
}
@Override
public ReferenceEntry<K, V> getNextInWriteQueue() {
return nextWrite;
}
@Override
public void setNextInWriteQueue(ReferenceEntry<K, V> next) {
this.nextWrite = next;
}
@Override
public ReferenceEntry<K, V> getPreviousInWriteQueue() {
return previousWrite;
}
@Override
public void setPreviousInWriteQueue(ReferenceEntry<K, V> previous) {
this.previousWrite = previous;
}
}
/**
* Used for weakly-referenced keys.
*/
static class WeakEntry<K, V> extends WeakReference<K> implements ReferenceEntry<K, V> {
final int hash;
final ReferenceEntry<K, V> next;
/*
* It'd be nice to get these for free from AbstractReferenceEntry, but we're already extending
* WeakReference<K>.
*/
// null access
volatile ValueReference<K, V> valueReference = unset();
WeakEntry(ReferenceQueue<K> queue, K key, int hash, ReferenceEntry<K, V> next) {
super(key, queue);
this.hash = hash;
this.next = next;
}
@Override
public K getKey() {
return get();
}
@Override
public long getAccessTime() {
throw new UnsupportedOperationException();
}
@Override
public void setAccessTime(long time) {
throw new UnsupportedOperationException();
}
@Override
public ReferenceEntry<K, V> getNextInAccessQueue() {
throw new UnsupportedOperationException();
}
// null write
@Override
public void setNextInAccessQueue(ReferenceEntry<K, V> next) {
throw new UnsupportedOperationException();
}
@Override
public ReferenceEntry<K, V> getPreviousInAccessQueue() {
throw new UnsupportedOperationException();
}
@Override
public void setPreviousInAccessQueue(ReferenceEntry<K, V> previous) {
throw new UnsupportedOperationException();
}
@Override
public long getWriteTime() {
throw new UnsupportedOperationException();
}
@Override
public void setWriteTime(long time) {
throw new UnsupportedOperationException();
}
@Override
public ReferenceEntry<K, V> getNextInWriteQueue() {
throw new UnsupportedOperationException();
}
// The code below is exactly the same for each entry type.
@Override
public void setNextInWriteQueue(ReferenceEntry<K, V> next) {
throw new UnsupportedOperationException();
}
@Override
public ReferenceEntry<K, V> getPreviousInWriteQueue() {
throw new UnsupportedOperationException();
}
@Override
public void setPreviousInWriteQueue(ReferenceEntry<K, V> previous) {
throw new UnsupportedOperationException();
}
@Override
public ValueReference<K, V> getValueReference() {
return valueReference;
}
@Override
public void setValueReference(ValueReference<K, V> valueReference) {
this.valueReference = valueReference;
}
@Override
public int getHash() {
return hash;
}
@Override
public ReferenceEntry<K, V> getNext() {
return next;
}
}
static final class WeakAccessEntry<K, V> extends WeakEntry<K, V> {
volatile long accessTime = Long.MAX_VALUE;
// The code below is exactly the same for each access entry type.
// Guarded By Segment.this
ReferenceEntry<K, V> nextAccess = nullEntry();
// Guarded By Segment.this
ReferenceEntry<K, V> previousAccess = nullEntry();
WeakAccessEntry(
ReferenceQueue<K> queue, K key, int hash, ReferenceEntry<K, V> next) {
super(queue, key, hash, next);
}
@Override
public long getAccessTime() {
return accessTime;
}
@Override
public void setAccessTime(long time) {
this.accessTime = time;
}
@Override
public ReferenceEntry<K, V> getNextInAccessQueue() {
return nextAccess;
}
@Override
public void setNextInAccessQueue(ReferenceEntry<K, V> next) {
this.nextAccess = next;
}
@Override
public ReferenceEntry<K, V> getPreviousInAccessQueue() {
return previousAccess;
}
@Override
public void setPreviousInAccessQueue(ReferenceEntry<K, V> previous) {
this.previousAccess = previous;
}
}
static final class WeakWriteEntry<K, V> extends WeakEntry<K, V> {
volatile long writeTime = Long.MAX_VALUE;
// The code below is exactly the same for each write entry type.
// Guarded By Segment.this
ReferenceEntry<K, V> nextWrite = nullEntry();
// Guarded By Segment.this
ReferenceEntry<K, V> previousWrite = nullEntry();
WeakWriteEntry(
ReferenceQueue<K> queue, K key, int hash, ReferenceEntry<K, V> next) {
super(queue, key, hash, next);
}
@Override
public long getWriteTime() {
return writeTime;
}
@Override
public void setWriteTime(long time) {
this.writeTime = time;
}
@Override
public ReferenceEntry<K, V> getNextInWriteQueue() {
return nextWrite;
}
@Override
public void setNextInWriteQueue(ReferenceEntry<K, V> next) {
this.nextWrite = next;
}
@Override
public ReferenceEntry<K, V> getPreviousInWriteQueue() {
return previousWrite;
}
@Override
public void setPreviousInWriteQueue(ReferenceEntry<K, V> previous) {
this.previousWrite = previous;
}
}
static final class WeakAccessWriteEntry<K, V> extends WeakEntry<K, V> {
volatile long accessTime = Long.MAX_VALUE;
// The code below is exactly the same for each access entry type.
// Guarded By Segment.this
ReferenceEntry<K, V> nextAccess = nullEntry();
// Guarded By Segment.this
ReferenceEntry<K, V> previousAccess = nullEntry();
volatile long writeTime = Long.MAX_VALUE;
// Guarded By Segment.this
ReferenceEntry<K, V> nextWrite = nullEntry();
// Guarded By Segment.this
ReferenceEntry<K, V> previousWrite = nullEntry();
WeakAccessWriteEntry(
ReferenceQueue<K> queue, K key, int hash, ReferenceEntry<K, V> next) {
super(queue, key, hash, next);
}
@Override
public long getAccessTime() {
return accessTime;
}
@Override
public void setAccessTime(long time) {
this.accessTime = time;
}
@Override
public ReferenceEntry<K, V> getNextInAccessQueue() {
return nextAccess;
}
// The code below is exactly the same for each write entry type.
@Override
public void setNextInAccessQueue(ReferenceEntry<K, V> next) {
this.nextAccess = next;
}
@Override
public ReferenceEntry<K, V> getPreviousInAccessQueue() {
return previousAccess;
}
@Override
public void setPreviousInAccessQueue(ReferenceEntry<K, V> previous) {
this.previousAccess = previous;
}
@Override
public long getWriteTime() {
return writeTime;
}
@Override
public void setWriteTime(long time) {
this.writeTime = time;
}
@Override
public ReferenceEntry<K, V> getNextInWriteQueue() {
return nextWrite;
}
@Override
public void setNextInWriteQueue(ReferenceEntry<K, V> next) {
this.nextWrite = next;
}
@Override
public ReferenceEntry<K, V> getPreviousInWriteQueue() {
return previousWrite;
}
@Override
public void setPreviousInWriteQueue(ReferenceEntry<K, V> previous) {
this.previousWrite = previous;
}
}
/**
* References a weak value.
*/
static class WeakValueReference<K, V>
extends WeakReference<V> implements ValueReference<K, V> {
final ReferenceEntry<K, V> entry;
WeakValueReference(ReferenceQueue<V> queue, V referent, ReferenceEntry<K, V> entry) {
super(referent, queue);
this.entry = entry;
}
@Override
public int getWeight() {
return 1;
}
@Override
public ReferenceEntry<K, V> getEntry() {
return entry;
}
@Override
public void notifyNewValue(V newValue) {
}
@Override
public ValueReference<K, V> copyFor(
ReferenceQueue<V> queue, V value, ReferenceEntry<K, V> entry) {
return new WeakValueReference<K, V>(queue, value, entry);
}
@Override
public boolean isLoading() {
return false;
}
@Override
public boolean isActive() {
return true;
}
@Override
public V waitForValue() {
return get();
}
}
/**
* References a strong value.
*/
static class StrongValueReference<K, V> implements ValueReference<K, V> {
final V referent;
StrongValueReference(V referent) {
this.referent = referent;
}
@Override
public V get() {
return referent;
}
@Override
public int getWeight() {
return 1;
}
@Override
public ReferenceEntry<K, V> getEntry() {
return null;
}
@Override
public ValueReference<K, V> copyFor(
ReferenceQueue<V> queue, V value, ReferenceEntry<K, V> entry) {
return this;
}
@Override
public boolean isLoading() {
return false;
}
@Override
public boolean isActive() {
return true;
}
@Override
public V waitForValue() {
return get();
}
@Override
public void notifyNewValue(V newValue) {
}
}
/**
* References a weak value.
*/
static final class WeightedWeakValueReference<K, V> extends WeakValueReference<K, V> {
final int weight;
WeightedWeakValueReference(ReferenceQueue<V> queue, V referent, ReferenceEntry<K, V> entry,
int weight) {
super(queue, referent, entry);
this.weight = weight;
}
@Override
public int getWeight() {
return weight;
}
@Override
public ValueReference<K, V> copyFor(
ReferenceQueue<V> queue, V value, ReferenceEntry<K, V> entry) {
return new WeightedWeakValueReference<K, V>(queue, value, entry, weight);
}
}
/**
* References a strong value.
*/
static final class WeightedStrongValueReference<K, V> extends StrongValueReference<K, V> {
final int weight;
WeightedStrongValueReference(V referent, int weight) {
super(referent);
this.weight = weight;
}
@Override
public int getWeight() {
return weight;
}
}
/**
* 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<K, V> 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 LocalCache<K, V> map;
/**
* The maximum weight of this segment. UNSET_INT if there is no maximum.
*/
final long maxSegmentWeight;
/**
* The key reference queue contains entries whose keys have been garbage collected, and which
* need to be cleaned up internally.
*/
final ReferenceQueue<K> keyReferenceQueue;
/**
* The value reference queue contains value references whose values have been garbage collected,
* and which need to be cleaned up internally.
*/
final ReferenceQueue<V> valueReferenceQueue;
/**
* The recency queue is used to record which entries were accessed for updating the access
* 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<ReferenceEntry<K, V>> 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 write time. Elements are added to the
* tail of the queue on write.
*/
final Queue<ReferenceEntry<K, V>> writeQueue;
/**
* A queue of elements currently in the map, ordered by access time. Elements are added to the
* tail of the queue on access (note that writes count as accesses).
*/
final Queue<ReferenceEntry<K, V>> accessQueue;
/**
* The number of live elements in this segment's region.
*/
volatile int count;
/**
* The weight of the live elements in this segment's region.
*/
long totalWeight;
/**
* 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
* loading 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<ReferenceEntry<K, V>> table;
Segment(LocalCache<K, V> map, int initialCapacity, long maxSegmentWeight) {
this.map = map;
this.maxSegmentWeight = maxSegmentWeight;
initTable(newEntryArray(initialCapacity));
keyReferenceQueue = map.usesKeyReferences()
? new ReferenceQueue<K>() : null;
valueReferenceQueue = map.usesValueReferences()
? new ReferenceQueue<V>() : null;
recencyQueue = map.usesAccessQueue()
? new ConcurrentLinkedQueue<ReferenceEntry<K, V>>()
: LocalCache.discardingQueue();
writeQueue = map.usesWriteQueue()
? new WriteQueue<K, V>()
: LocalCache.discardingQueue();
accessQueue = map.usesAccessQueue()
? new AccessQueue<K, V>()
: LocalCache.discardingQueue();
}
AtomicReferenceArray<ReferenceEntry<K, V>> newEntryArray(int size) {
return new AtomicReferenceArray<ReferenceEntry<K, V>>(size);
}
void initTable(AtomicReferenceArray<ReferenceEntry<K, V>> newTable) {
this.threshold = newTable.length() * 3 / 4; // 0.75
if (this.threshold == maxSegmentWeight) {
// prevent spurious expansion before eviction
this.threshold++;
}
this.table = newTable;
}
ReferenceEntry<K, V> newEntry(K key, int hash, ReferenceEntry<K, V> next) {
return map.entryFactory.newEntry(this, checkNotNull(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.
*/
ReferenceEntry<K, V> copyEntry(ReferenceEntry<K, V> original, ReferenceEntry<K, V> newNext) {
if (original.getKey() == null) {
// key collected
return null;
}
ValueReference<K, V> valueReference = original.getValueReference();
V value = valueReference.get();
if ((value == null) && valueReference.isActive()) {
// value collected
return null;
}
ReferenceEntry<K, V> 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 access queue.
*/
void setValue(ReferenceEntry<K, V> entry, K key, V value, long now) {
ValueReference<K, V> previous = entry.getValueReference();
int weight = 1;
checkState(weight >= 0, "Weights must be non-negative");
ValueReference<K, V> valueReference =
map.valueStrength.referenceValue(this, entry, value, weight);
entry.setValueReference(valueReference);
recordWrite(entry, weight, now);
previous.notifyNewValue(value);
}
// loading
V get(K key, int hash, CacheLoader<? super K, V> loader) throws ExecutionException {
checkNotNull(key);
checkNotNull(loader);
try {
if (count != 0) { // read-volatile
// don't call getLiveEntry, which would ignore loading values
ReferenceEntry<K, V> e = getEntry(key, hash);
if (e != null) {
long now = map.ticker.read();
V value = getLiveValue(e, now);
if (value != null) {
recordRead(e, now);
return scheduleRefresh(e, key, hash, value, now, loader);
}
ValueReference<K, V> valueReference = e.getValueReference();
if (valueReference.isLoading()) {
return waitForLoadingValue(e, key, valueReference);
}
}
}
// at this point e is either null or expired;
return lockedGetOrLoad(key, hash, loader);
} catch (ExecutionException ee) {
Throwable cause = ee.getCause();
if (cause instanceof Error) {
throw new ExecutionError((Error) cause);
} else if (cause instanceof RuntimeException) {
throw new UncheckedExecutionException(cause);
}
throw ee;
} finally {
postReadCleanup();
}
}
V lockedGetOrLoad(K key, int hash, CacheLoader<? super K, V> loader)
throws ExecutionException {
ReferenceEntry<K, V> e;
ValueReference<K, V> valueReference = null;
LoadingValueReference<K, V> loadingValueReference = null;
boolean createNewEntry = true;
lock();
try {
// re-read ticker once inside the lock
long now = map.ticker.read();
preWriteCleanup(now);
int newCount = this.count - 1;
AtomicReferenceArray<ReferenceEntry<K, V>> table = this.table;
int index = hash & (table.length() - 1);
ReferenceEntry<K, V> first = table.get(index);
for (e = first; e != null; e = e.getNext()) {
K entryKey = e.getKey();
if (e.getHash() == hash && entryKey != null
&& map.keyEquivalence.equivalent(key, entryKey)) {
valueReference = e.getValueReference();
if (valueReference.isLoading()) {
createNewEntry = false;
} else {
V value = valueReference.get();
if (value == null) {
enqueueNotification(entryKey, hash, valueReference, RemovalCause.COLLECTED);
} else if (map.isExpired(e, now)) {
// This is a duplicate check, as preWriteCleanup already purged expired
// entries, but let's accomodate an incorrect expiration queue.
enqueueNotification(entryKey, hash, valueReference, RemovalCause.EXPIRED);
} else {
recordLockedRead(e, now);
// we were concurrent with loading; don't consider refresh
return value;
}
// immediately reuse invalid entries
writeQueue.remove(e);
accessQueue.remove(e);
this.count = newCount; // write-volatile
}
break;
}
}
if (createNewEntry) {
loadingValueReference = new LoadingValueReference<K, V>();
if (e == null) {
e = newEntry(key, hash, first);
e.setValueReference(loadingValueReference);
table.set(index, e);
} else {
e.setValueReference(loadingValueReference);
}
}
} finally {
unlock();
postWriteCleanup();
}
if (createNewEntry) {
// Synchronizes on the entry to allow failing fast when a recursive load is
// detected. This may be circumvented when an entry is copied, but will fail fast most
// of the time.
synchronized (e) {
return loadSync(key, hash, loadingValueReference, loader);
}
} else {
// The entry already exists. Wait for loading.
return waitForLoadingValue(e, key, valueReference);
}
}
V waitForLoadingValue(ReferenceEntry<K, V> e, K key, ValueReference<K, V> valueReference)
throws ExecutionException {
if (!valueReference.isLoading()) {
throw new AssertionError();
}
checkState(!Thread.holdsLock(e), "Recursive load of: %s", key);
// don't consider expiration as we're concurrent with loading
V value = valueReference.waitForValue();
if (value == null) {
throw new CacheLoader.InvalidCacheLoadException("CacheLoader returned null for key " + key + ".");
}
// re-read ticker now that loading has completed
long now = map.ticker.read();
recordRead(e, now);
return value;
}
// at most one of loadSync/loadAsync may be called for any given LoadingValueReference
V loadSync(K key, int hash, LoadingValueReference<K, V> loadingValueReference,
CacheLoader<? super K, V> loader) throws ExecutionException {
ListenableFuture<V> loadingFuture = loadingValueReference.loadFuture(key, loader);
return getAndRecordStats(key, hash, loadingValueReference, loadingFuture);
}
ListenableFuture<V> loadAsync(final K key, final int hash,
final LoadingValueReference<K, V> loadingValueReference, CacheLoader<? super K, V> loader) {
final ListenableFuture<V> loadingFuture = loadingValueReference.loadFuture(key, loader);
loadingFuture.addListener(
new Runnable() {
@Override
public void run() {
try {
V newValue = getAndRecordStats(key, hash, loadingValueReference, loadingFuture);
} catch (Throwable t) {
logger.log(Level.WARNING, "Exception thrown during refresh", t);
loadingValueReference.setException(t);
}
}
}, directExecutor());
return loadingFuture;
}
/**
* Waits uninterruptibly for {@code newValue} to be loaded, and then records loading stats.
*/
V getAndRecordStats(K key, int hash, LoadingValueReference<K, V> loadingValueReference,
ListenableFuture<V> newValue) throws ExecutionException {
V value = null;
try {
value = getUninterruptibly(newValue);
if (value == null) {
throw new CacheLoader.InvalidCacheLoadException("CacheLoader returned null for key " + key + ".");
}
storeLoadedValue(key, hash, loadingValueReference, value);
return value;
} finally {
if (value == null) {
removeLoadingValue(key, hash, loadingValueReference);
}
}
}
V scheduleRefresh(ReferenceEntry<K, V> entry, K key, int hash, V oldValue, long now,
CacheLoader<? super K, V> loader) {
if (map.refreshes() && (now - entry.getWriteTime() > map.refreshNanos)
&& !entry.getValueReference().isLoading()) {
V newValue = refresh(key, hash, loader, true);
if (newValue != null) {
return newValue;
}
}
return oldValue;
}
/**
* Refreshes the value associated with {@code key}, unless another thread is already doing so.
* Returns the newly refreshed value associated with {@code key} if it was refreshed inline, or
* {@code null} if another thread is performing the refresh or if an error occurs during
* refresh.
*/
V refresh(K key, int hash, CacheLoader<? super K, V> loader, boolean checkTime) {
final LoadingValueReference<K, V> loadingValueReference =
insertLoadingValueReference(key, hash, checkTime);
if (loadingValueReference == null) {
return null;
}
ListenableFuture<V> result = loadAsync(key, hash, loadingValueReference, loader);
if (result.isDone()) {
try {
return Uninterruptibles.getUninterruptibly(result);
} catch (Throwable t) {
// don't let refresh exceptions propagate; error was already logged
}
}
return null;
}
/**
* Returns a newly inserted {@code LoadingValueReference}, or null if the live value reference
* is already loading.
*/
LoadingValueReference<K, V> insertLoadingValueReference(final K key, final int hash,
boolean checkTime) {
ReferenceEntry<K, V> e = null;
lock();
try {
long now = map.ticker.read();
preWriteCleanup(now);
AtomicReferenceArray<ReferenceEntry<K, V>> table = this.table;
int index = hash & (table.length() - 1);
ReferenceEntry<K, V> first = table.get(index);
// Look for an existing entry.
for (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<K, V> valueReference = e.getValueReference();
if (valueReference.isLoading()
|| (checkTime && (now - e.getWriteTime() < map.refreshNanos))) {
// refresh is a no-op if loading is pending
// if checkTime, we want to check *after* acquiring the lock if refresh still needs
// to be scheduled
return null;
}
// continue returning old value while loading
++modCount;
LoadingValueReference<K, V> loadingValueReference =
new LoadingValueReference<K, V>(valueReference);
e.setValueReference(loadingValueReference);
return loadingValueReference;
}
}
++modCount;
LoadingValueReference<K, V> loadingValueReference = new LoadingValueReference<K, V>();
e = newEntry(key, hash, first);
e.setValueReference(loadingValueReference);
table.set(index, e);
return loadingValueReference;
} finally {
unlock();
postWriteCleanup();
}
}
// 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.
*/
void drainReferenceQueues() {
if (map.usesKeyReferences()) {
drainKeyReferenceQueue();
}
if (map.usesValueReferences()) {
drainValueReferenceQueue();
}
}
void drainKeyReferenceQueue() {
Reference<? extends K> ref;
int i = 0;
while ((ref = keyReferenceQueue.poll()) != null) {
@SuppressWarnings("unchecked")
ReferenceEntry<K, V> entry = (ReferenceEntry<K, V>) ref;
map.reclaimKey(entry);
if (++i == DRAIN_MAX) {
break;
}
}
}
void drainValueReferenceQueue() {
Reference<? extends V> ref;
int i = 0;
while ((ref = valueReferenceQueue.poll()) != null) {
@SuppressWarnings("unchecked")
ValueReference<K, V> valueReference = (ValueReference<K, V>) 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.
* <p>
* <p>Note: locked reads should use {@link #recordLockedRead}.
*/
void recordRead(ReferenceEntry<K, V> entry, long now) {
if (map.recordsAccess()) {
entry.setAccessTime(now);
}
recencyQueue.add(entry);
}
/**
* Updates the eviction metadata that {@code entry} was just read. This currently amounts to
* adding {@code entry} to relevant eviction lists.
* <p>
* <p>Note: this method should only be called under lock, as it directly manipulates the
* eviction queues. Unlocked reads should use {@link #recordRead}.
*/
void recordLockedRead(ReferenceEntry<K, V> entry, long now) {
if (map.recordsAccess()) {
entry.setAccessTime(now);
}
accessQueue.add(entry);
}
/**
* Updates eviction metadata that {@code entry} was just written. This currently amounts to
* adding {@code entry} to relevant eviction lists.
*/
void recordWrite(ReferenceEntry<K, V> entry, int weight, long now) {
// we are already under lock, so drain the recency queue immediately
drainRecencyQueue();
totalWeight += weight;
if (map.recordsAccess()) {
entry.setAccessTime(now);
}
if (map.recordsWrite()) {
entry.setWriteTime(now);
}
accessQueue.add(entry);
writeQueue.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).
*/
void drainRecencyQueue() {
ReferenceEntry<K, V> 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 (accessQueue.contains(e)) {
accessQueue.add(e);
}
}
}
// expiration
/**
* Cleanup expired entries when the lock is available.
*/
void tryExpireEntries(long now) {
if (tryLock()) {
try {
expireEntries(now);
} finally {
unlock();
// don't call postWriteCleanup as we're in a read
}
}
}
void expireEntries(long now) {
drainRecencyQueue();
ReferenceEntry<K, V> e;
while ((e = writeQueue.peek()) != null && map.isExpired(e, now)) {
if (!removeEntry(e, e.getHash(), RemovalCause.EXPIRED)) {
throw new AssertionError();
}
}
while ((e = accessQueue.peek()) != null && map.isExpired(e, now)) {
if (!removeEntry(e, e.getHash(), RemovalCause.EXPIRED)) {
throw new AssertionError();
}
}
}
// eviction
void enqueueNotification(ReferenceEntry<K, V> entry, RemovalCause cause) {
enqueueNotification(entry.getKey(), entry.getHash(), entry.getValueReference(), cause);
}
void enqueueNotification(K key, int hash, ValueReference<K, V> valueReference,
RemovalCause cause) {
totalWeight -= valueReference.getWeight();
if (map.removalNotificationQueue != DISCARDING_QUEUE) {
V value = valueReference.get();
RemovalNotification<K, V> notification = new RemovalNotification<K, V>(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}.
*/
void evictEntries() {
if (!map.evictsBySize()) {
return;
}
drainRecencyQueue();
while (totalWeight > maxSegmentWeight) {
ReferenceEntry<K, V> e = getNextEvictable();
if (!removeEntry(e, e.getHash(), RemovalCause.SIZE)) {
throw new AssertionError();
}
}
}
// TODO(fry): instead implement this with an eviction head
ReferenceEntry<K, V> getNextEvictable() {
for (ReferenceEntry<K, V> e : accessQueue) {
int weight = e.getValueReference().getWeight();
if (weight > 0) {
return e;
}
}
throw new AssertionError();
}
/**
* Returns first entry of bin for given hash.
*/
ReferenceEntry<K, V> getFirst(int hash) {
// read this volatile field only once
AtomicReferenceArray<ReferenceEntry<K, V>> table = this.table;
return table.get(hash & (table.length() - 1));
}
// Specialized implementations of map methods
ReferenceEntry<K, V> getEntry(Object key, int hash) {
for (ReferenceEntry<K, V> 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<K, V> getLiveEntry(Object key, int hash, long now) {
ReferenceEntry<K, V> e = getEntry(key, hash);
if (e == null) {
return null;
} else if (map.isExpired(e, now)) {
tryExpireEntries(now);
return null;
}
return e;
}
/**
* Gets the value from an entry. Returns null if the entry is invalid, partially-collected,
* loading, or expired.
*/
V getLiveValue(ReferenceEntry<K, V> entry, long now) {
if (entry.getKey() == null) {
tryDrainReferenceQueues();
return null;
}
V value = entry.getValueReference().get();
if (value == null) {
tryDrainReferenceQueues();
return null;
}
if (map.isExpired(entry, now)) {
tryExpireEntries(now);
return null;
}
return value;
}
V get(Object key, int hash) {
try {
if (count != 0) { // read-volatile
long now = map.ticker.read();
ReferenceEntry<K, V> e = getLiveEntry(key, hash, now);
if (e == null) {
return null;
}
V value = e.getValueReference().get();
if (value != null) {
recordRead(e, now);
return scheduleRefresh(e, e.getKey(), hash, value, now, map.defaultLoader);
}
tryDrainReferenceQueues();
}
return null;
} finally {
postReadCleanup();
}
}
boolean containsKey(Object key, int hash) {
try {
if (count != 0) { // read-volatile
long now = map.ticker.read();
ReferenceEntry<K, V> e = getLiveEntry(key, hash, now);
if (e == null) {
return false;
}
return e.getValueReference().get() != null;
}
return false;
} finally {
postReadCleanup();
}
}
V put(K key, int hash, V value, boolean onlyIfAbsent) {
lock();
try {
long now = map.ticker.read();
preWriteCleanup(now);
int newCount = this.count + 1;
if (newCount > this.threshold) { // ensure capacity
expand();
newCount = this.count + 1;
}
AtomicReferenceArray<ReferenceEntry<K, V>> table = this.table;
int index = hash & (table.length() - 1);
ReferenceEntry<K, V> first = table.get(index);
// Look for an existing entry.
for (ReferenceEntry<K, V> 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<K, V> valueReference = e.getValueReference();
V entryValue = valueReference.get();
if (entryValue == null) {
++modCount;
if (valueReference.isActive()) {
enqueueNotification(key, hash, valueReference, RemovalCause.COLLECTED);
setValue(e, key, value, now);
newCount = this.count; // count remains unchanged
} else {
setValue(e, key, value, now);
newCount = this.count + 1;
}
this.count = newCount; // write-volatile
evictEntries();
return null;
} else if (onlyIfAbsent) {
// Mimic
// "if (!map.containsKey(key)) ...
// else return map.get(key);
recordLockedRead(e, now);
return entryValue;
} else {
// clobber existing entry, count remains unchanged
++modCount;
enqueueNotification(key, hash, valueReference, RemovalCause.REPLACED);
setValue(e, key, value, now);
evictEntries();
return entryValue;
}
}
}
// Create a new entry.
++modCount;
ReferenceEntry<K, V> newEntry = newEntry(key, hash, first);
setValue(newEntry, key, value, now);
table.set(index, newEntry);
newCount = this.count + 1;
this.count = newCount; // write-volatile
evictEntries();
return null;
} finally {
unlock();
postWriteCleanup();
}
}
/**
* Expands the table if possible.
*/
void expand() {
AtomicReferenceArray<ReferenceEntry<K, V>> 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<ReferenceEntry<K, V>> 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<K, V> head = oldTable.get(oldIndex);
if (head != null) {
ReferenceEntry<K, V> 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<K, V> tail = head;
int tailIndex = headIndex;
for (ReferenceEntry<K, V> 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<K, V> e = head; e != tail; e = e.getNext()) {
int newIndex = e.getHash() & newMask;
ReferenceEntry<K, V> newNext = newTable.get(newIndex);
ReferenceEntry<K, V> 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 {
long now = map.ticker.read();
preWriteCleanup(now);
AtomicReferenceArray<ReferenceEntry<K, V>> table = this.table;
int index = hash & (table.length() - 1);
ReferenceEntry<K, V> first = table.get(index);
for (ReferenceEntry<K, V> e = first; e != null; e = e.getNext()) {
K entryKey = e.getKey();
if (e.getHash() == hash && entryKey != null
&& map.keyEquivalence.equivalent(key, entryKey)) {
ValueReference<K, V> valueReference = e.getValueReference();
V entryValue = valueReference.get();
if (entryValue == null) {
if (valueReference.isActive()) {
// If the value disappeared, this entry is partially collected.
int newCount = this.count - 1;
++modCount;
ReferenceEntry<K, V> newFirst = removeValueFromChain(
first, e, entryKey, hash, valueReference, RemovalCause.COLLECTED);
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, valueReference, RemovalCause.REPLACED);
setValue(e, key, newValue, now);
evictEntries();
return true;
} else {
// Mimic
// "if (map.containsKey(key) && map.get(key).equals(oldValue))..."
recordLockedRead(e, now);
return false;
}
}
}
return false;
} finally {
unlock();
postWriteCleanup();
}
}
V replace(K key, int hash, V newValue) {
lock();
try {
long now = map.ticker.read();
preWriteCleanup(now);
AtomicReferenceArray<ReferenceEntry<K, V>> table = this.table;
int index = hash & (table.length() - 1);
ReferenceEntry<K, V> first = table.get(index);
for (ReferenceEntry<K, V> e = first; e != null; e = e.getNext()) {
K entryKey = e.getKey();
if (e.getHash() == hash && entryKey != null
&& map.keyEquivalence.equivalent(key, entryKey)) {
ValueReference<K, V> valueReference = e.getValueReference();
V entryValue = valueReference.get();
if (entryValue == null) {
if (valueReference.isActive()) {
// If the value disappeared, this entry is partially collected.
int newCount = this.count - 1;
++modCount;
ReferenceEntry<K, V> newFirst = removeValueFromChain(
first, e, entryKey, hash, valueReference, RemovalCause.COLLECTED);
newCount = this.count - 1;
table.set(index, newFirst);
this.count = newCount; // write-volatile
}
return null;
}
++modCount;
enqueueNotification(key, hash, valueReference, RemovalCause.REPLACED);
setValue(e, key, newValue, now);
evictEntries();
return entryValue;
}
}
return null;
} finally {
unlock();
postWriteCleanup();
}
}
V remove(Object key, int hash) {
lock();
try {
long now = map.ticker.read();
preWriteCleanup(now);
int newCount = this.count - 1;
AtomicReferenceArray<ReferenceEntry<K, V>> table = this.table;
int index = hash & (table.length() - 1);
ReferenceEntry<K, V> first = table.get(index);
for (ReferenceEntry<K, V> e = first; e != null; e = e.getNext()) {
K entryKey = e.getKey();
if (e.getHash() == hash && entryKey != null
&& map.keyEquivalence.equivalent(key, entryKey)) {
ValueReference<K, V> valueReference = e.getValueReference();
V entryValue = valueReference.get();
RemovalCause cause;
if (entryValue != null) {
cause = RemovalCause.EXPLICIT;
} else if (valueReference.isActive()) {
cause = RemovalCause.COLLECTED;
} else {
// currently loading
return null;
}
++modCount;
ReferenceEntry<K, V> newFirst = removeValueFromChain(
first, e, entryKey, hash, valueReference, cause);
newCount = this.count - 1;
table.set(index, newFirst);
this.count = newCount; // write-volatile
return entryValue;
}
}
return null;
} finally {
unlock();
postWriteCleanup();
}
}
boolean storeLoadedValue(K key, int hash, LoadingValueReference<K, V> oldValueReference,
V newValue) {
lock();
try {
long now = map.ticker.read();
preWriteCleanup(now);
int newCount = this.count + 1;
if (newCount > this.threshold) { // ensure capacity
expand();
newCount = this.count + 1;
}
AtomicReferenceArray<ReferenceEntry<K, V>> table = this.table;
int index = hash & (table.length() - 1);
ReferenceEntry<K, V> first = table.get(index);
for (ReferenceEntry<K, V> e = first; e != null; e = e.getNext()) {
K entryKey = e.getKey();
if (e.getHash() == hash && entryKey != null
&& map.keyEquivalence.equivalent(key, entryKey)) {
ValueReference<K, V> valueReference = e.getValueReference();
V entryValue = valueReference.get();
// replace the old LoadingValueReference if it's live, otherwise
// perform a putIfAbsent
if (oldValueReference == valueReference
|| (entryValue == null && valueReference != UNSET)) {
++modCount;
if (oldValueReference.isActive()) {
RemovalCause cause =
(entryValue == null) ? RemovalCause.COLLECTED : RemovalCause.REPLACED;
enqueueNotification(key, hash, oldValueReference, cause);
newCount--;
}
setValue(e, key, newValue, now);
this.count = newCount; // write-volatile
evictEntries();
return true;
}
// the loaded value was already clobbered
valueReference = new WeightedStrongValueReference<K, V>(newValue, 0);
enqueueNotification(key, hash, valueReference, RemovalCause.REPLACED);
return false;
}
}
++modCount;
ReferenceEntry<K, V> newEntry = newEntry(key, hash, first);
setValue(newEntry, key, newValue, now);
table.set(index, newEntry);
this.count = newCount; // write-volatile
evictEntries();
return true;
} finally {
unlock();
postWriteCleanup();
}
}
boolean remove(Object key, int hash, Object value) {
lock();
try {
long now = map.ticker.read();
preWriteCleanup(now);
int newCount = this.count - 1;
AtomicReferenceArray<ReferenceEntry<K, V>> table = this.table;
int index = hash & (table.length() - 1);
ReferenceEntry<K, V> first = table.get(index);
for (ReferenceEntry<K, V> e = first; e != null; e = e.getNext()) {
K entryKey = e.getKey();
if (e.getHash() == hash && entryKey != null
&& map.keyEquivalence.equivalent(key, entryKey)) {
ValueReference<K, V> valueReference = e.getValueReference();
V entryValue = valueReference.get();
RemovalCause cause;
if (map.valueEquivalence.equivalent(value, entryValue)) {
cause = RemovalCause.EXPLICIT;
} else if (entryValue == null && valueReference.isActive()) {
cause = RemovalCause.COLLECTED;
} else {
// currently loading
return false;
}
++modCount;
ReferenceEntry<K, V> newFirst = removeValueFromChain(
first, e, entryKey, hash, valueReference, cause);
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) { // read-volatile
lock();
try {
AtomicReferenceArray<ReferenceEntry<K, V>> table = this.table;
for (int i = 0; i < table.length(); ++i) {
for (ReferenceEntry<K, V> e = table.get(i); e != null; e = e.getNext()) {
// Loading references aren't actually in the map yet.
if (e.getValueReference().isActive()) {
enqueueNotification(e, RemovalCause.EXPLICIT);
}
}
}
for (int i = 0; i < table.length(); ++i) {
table.set(i, null);
}
clearReferenceQueues();
writeQueue.clear();
accessQueue.clear();
readCount.set(0);
++modCount;
count = 0; // write-volatile
} finally {
unlock();
postWriteCleanup();
}
}
}
ReferenceEntry<K, V> removeValueFromChain(ReferenceEntry<K, V> first,
ReferenceEntry<K, V> entry, K key, int hash,
ValueReference<K, V> valueReference,
RemovalCause cause) {
enqueueNotification(key, hash, valueReference, cause);
writeQueue.remove(entry);
accessQueue.remove(entry);
if (valueReference.isLoading()) {
valueReference.notifyNewValue(null);
return first;
} else {
return removeEntryFromChain(first, entry);
}
}
ReferenceEntry<K, V> removeEntryFromChain(ReferenceEntry<K, V> first,
ReferenceEntry<K, V> entry) {
int newCount = count;
ReferenceEntry<K, V> newFirst = entry.getNext();
for (ReferenceEntry<K, V> e = first; e != entry; e = e.getNext()) {
ReferenceEntry<K, V> next = copyEntry(e, newFirst);
if (next != null) {
newFirst = next;
} else {
removeCollectedEntry(e);
newCount--;
}
}
this.count = newCount;
return newFirst;
}
void removeCollectedEntry(ReferenceEntry<K, V> entry) {
enqueueNotification(entry, RemovalCause.COLLECTED);
writeQueue.remove(entry);
accessQueue.remove(entry);
}
/**
* Removes an entry whose key has been garbage collected.
*/
boolean reclaimKey(ReferenceEntry<K, V> entry, int hash) {
lock();
try {
int newCount = count - 1;
AtomicReferenceArray<ReferenceEntry<K, V>> table = this.table;
int index = hash & (table.length() - 1);
ReferenceEntry<K, V> first = table.get(index);
for (ReferenceEntry<K, V> e = first; e != null; e = e.getNext()) {
if (e == entry) {
++modCount;
ReferenceEntry<K, V> newFirst = removeValueFromChain(
first, e, e.getKey(), hash, e.getValueReference(), RemovalCause.COLLECTED);
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<K, V> valueReference) {
lock();
try {
int newCount = this.count - 1;
AtomicReferenceArray<ReferenceEntry<K, V>> table = this.table;
int index = hash & (table.length() - 1);
ReferenceEntry<K, V> first = table.get(index);
for (ReferenceEntry<K, V> e = first; e != null; e = e.getNext()) {
K entryKey = e.getKey();
if (e.getHash() == hash && entryKey != null
&& map.keyEquivalence.equivalent(key, entryKey)) {
ValueReference<K, V> v = e.getValueReference();
if (v == valueReference) {
++modCount;
ReferenceEntry<K, V> newFirst = removeValueFromChain(
first, e, entryKey, hash, valueReference, RemovalCause.COLLECTED);
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();
}
}
}
boolean removeLoadingValue(K key, int hash, LoadingValueReference<K, V> valueReference) {
lock();
try {
AtomicReferenceArray<ReferenceEntry<K, V>> table = this.table;
int index = hash & (table.length() - 1);
ReferenceEntry<K, V> first = table.get(index);
for (ReferenceEntry<K, V> e = first; e != null; e = e.getNext()) {
K entryKey = e.getKey();
if (e.getHash() == hash && entryKey != null
&& map.keyEquivalence.equivalent(key, entryKey)) {
ValueReference<K, V> v = e.getValueReference();
if (v == valueReference) {
if (valueReference.isActive()) {
e.setValueReference(valueReference.getOldValue());
} else {
ReferenceEntry<K, V> newFirst = removeEntryFromChain(first, e);
table.set(index, newFirst);
}
return true;
}
return false;
}
}
return false;
} finally {
unlock();
postWriteCleanup();
}
}
boolean removeEntry(ReferenceEntry<K, V> entry, int hash, RemovalCause cause) {
int newCount = this.count - 1;
AtomicReferenceArray<ReferenceEntry<K, V>> table = this.table;
int index = hash & (table.length() - 1);
ReferenceEntry<K, V> first = table.get(index);
for (ReferenceEntry<K, V> e = first; e != null; e = e.getNext()) {
if (e == entry) {
++modCount;
ReferenceEntry<K, V> newFirst = removeValueFromChain(
first, e, e.getKey(), hash, e.getValueReference(), cause);
newCount = this.count - 1;
table.set(index, newFirst);
this.count = newCount; // write-volatile
return true;
}
}
return false;
}
/**
* Performs routine cleanup following a read. Normally cleanup happens during writes. 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) {
cleanUp();
}
}
/**
* 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.
* <p>
* <p>Post-condition: expireEntries has been run.
*/
void preWriteCleanup(long now) {
runLockedCleanup(now);
}
/**
* Performs routine cleanup following a write.
*/
void postWriteCleanup() {
}
void cleanUp() {
long now = map.ticker.read();
runLockedCleanup(now);
}
void runLockedCleanup(long now) {
if (tryLock()) {
try {
drainReferenceQueues();
expireEntries(now); // calls drainRecencyQueue
readCount.set(0);
} finally {
unlock();
}
}
}
}
static class LoadingValueReference<K, V> implements ValueReference<K, V> {
// TODO(fry): rename get, then extend AbstractFuture instead of containing SettableFuture
final SettableFuture<V> futureValue = SettableFuture.create();
final Stopwatch stopwatch = Stopwatch.createUnstarted();
volatile ValueReference<K, V> oldValue;
public LoadingValueReference() {
this(LocalCache.unset());
}
public LoadingValueReference(ValueReference<K, V> oldValue) {
this.oldValue = oldValue;
}
@Override
public boolean isLoading() {
return true;
}
@Override
public boolean isActive() {
return oldValue.isActive();
}
@Override
public int getWeight() {
return oldValue.getWeight();
}
public boolean set(V newValue) {
return futureValue.set(newValue);
}
public boolean setException(Throwable t) {
return futureValue.setException(t);
}
private ListenableFuture<V> fullyFailedFuture(Throwable t) {
return Futures.immediateFailedFuture(t);
}
@Override
public void notifyNewValue(V newValue) {
if (newValue != null) {
// The pending load was clobbered by a manual write.
// Unblock all pending gets, and have them return the new value.
set(newValue);
} else {
// The pending load was removed. Delay notifications until loading completes.
oldValue = unset();
}
// TODO(fry): could also cancel loading if we had a handle on its future
}
public ListenableFuture<V> loadFuture(K key, CacheLoader<? super K, V> loader) {
stopwatch.start();
V previousValue = oldValue.get();
try {
if (previousValue == null) {
V newValue = loader.load(key);
return set(newValue) ? futureValue : Futures.immediateFuture(newValue);
}
ListenableFuture<V> newValue = loader.reload(key, previousValue);
if (newValue == null) {
return Futures.immediateFuture(null);
}
// To avoid a race, make sure the refreshed value is set into loadingValueReference
// *before* returning newValue from the cache query.
return Futures.transform(newValue, new Function<V, V>() {
@Override
public V apply(V newValue) {
LoadingValueReference.this.set(newValue);
return newValue;
}
});
} catch (Throwable t) {
if (t instanceof InterruptedException) {
Thread.currentThread().interrupt();
}
return setException(t) ? futureValue : fullyFailedFuture(t);
}
}
@Override
public V waitForValue() throws ExecutionException {
return getUninterruptibly(futureValue);
}
@Override
public V get() {
return oldValue.get();
}
public ValueReference<K, V> getOldValue() {
return oldValue;
}
@Override
public ReferenceEntry<K, V> getEntry() {
return null;
}
@Override
public ValueReference<K, V> copyFor(
ReferenceQueue<V> queue, V value, ReferenceEntry<K, V> entry) {
return this;
}
}
/**
* A custom queue for managing eviction order. Note that this is tightly integrated with {@code
* ReferenceEntry}, upon which it relies to perform its linking.
* <p>
* <p>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.
* <p>
* <p>The benefits of creating our own queue are that (1) we can replace elements in the middle
* of the queue as part of copyWriteEntry, and (2) the contains method is highly optimized
* for the current model.
*/
static final class WriteQueue<K, V> extends AbstractQueue<ReferenceEntry<K, V>> {
final ReferenceEntry<K, V> head = new AbstractReferenceEntry<K, V>() {
ReferenceEntry<K, V> nextWrite = this;
ReferenceEntry<K, V> previousWrite = this;
@Override
public long getWriteTime() {
return Long.MAX_VALUE;
}
@Override
public void setWriteTime(long time) {
}
@Override
public ReferenceEntry<K, V> getNextInWriteQueue() {
return nextWrite;
}
@Override
public void setNextInWriteQueue(ReferenceEntry<K, V> next) {
this.nextWrite = next;
}
@Override
public ReferenceEntry<K, V> getPreviousInWriteQueue() {
return previousWrite;
}
@Override
public void setPreviousInWriteQueue(ReferenceEntry<K, V> previous) {
this.previousWrite = previous;
}
};
// implements Queue
@Override
public boolean offer(ReferenceEntry<K, V> entry) {
// unlink
connectWriteOrder(entry.getPreviousInWriteQueue(), entry.getNextInWriteQueue());
// add to tail
connectWriteOrder(head.getPreviousInWriteQueue(), entry);
connectWriteOrder(entry, head);
return true;
}
@Override
public ReferenceEntry<K, V> peek() {
ReferenceEntry<K, V> next = head.getNextInWriteQueue();
return (next == head) ? null : next;
}
@Override
public ReferenceEntry<K, V> poll() {
ReferenceEntry<K, V> next = head.getNextInWriteQueue();
if (next == head) {
return null;
}
remove(next);
return next;
}
@Override
@SuppressWarnings("unchecked")
public boolean remove(Object o) {
ReferenceEntry<K, V> e = (ReferenceEntry) o;
ReferenceEntry<K, V> previous = e.getPreviousInWriteQueue();
ReferenceEntry<K, V> next = e.getNextInWriteQueue();
connectWriteOrder(previous, next);
nullifyWriteOrder(e);
return next != NullEntry.INSTANCE;
}
@Override
@SuppressWarnings("unchecked")
public boolean contains(Object o) {
ReferenceEntry<K, V> e = (ReferenceEntry) o;
return e.getNextInWriteQueue() != NullEntry.INSTANCE;
}
@Override
public boolean isEmpty() {
return head.getNextInWriteQueue() == head;
}
@Override
public int size() {
int size = 0;
for (ReferenceEntry<K, V> e = head.getNextInWriteQueue(); e != head;
e = e.getNextInWriteQueue()) {
size++;
}
return size;
}
@Override
public void clear() {
ReferenceEntry<K, V> e = head.getNextInWriteQueue();
while (e != head) {
ReferenceEntry<K, V> next = e.getNextInWriteQueue();
nullifyWriteOrder(e);
e = next;
}
head.setNextInWriteQueue(head);
head.setPreviousInWriteQueue(head);
}
@Override
public Iterator<ReferenceEntry<K, V>> iterator() {
return new AbstractSequentialIterator<ReferenceEntry<K, V>>(peek()) {
@Override
protected ReferenceEntry<K, V> computeNext(ReferenceEntry<K, V> previous) {
ReferenceEntry<K, V> next = previous.getNextInWriteQueue();
return (next == head) ? null : next;
}
};
}
}
/**
* A custom queue for managing access order. Note that this is tightly integrated with
* {@code ReferenceEntry}, upon which it reliese to perform its linking.
* <p>
* <p>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.
* <p>
* <p>The benefits of creating our own queue are that (1) we can replace elements in the middle
* of the queue as part of copyWriteEntry, and (2) the contains method is highly optimized
* for the current model.
*/
static final class AccessQueue<K, V> extends AbstractQueue<ReferenceEntry<K, V>> {
final ReferenceEntry<K, V> head = new AbstractReferenceEntry<K, V>() {
ReferenceEntry<K, V> nextAccess = this;
ReferenceEntry<K, V> previousAccess = this;
@Override
public long getAccessTime() {
return Long.MAX_VALUE;
}
@Override
public void setAccessTime(long time) {
}
@Override
public ReferenceEntry<K, V> getNextInAccessQueue() {
return nextAccess;
}
@Override
public void setNextInAccessQueue(ReferenceEntry<K, V> next) {
this.nextAccess = next;
}
@Override
public ReferenceEntry<K, V> getPreviousInAccessQueue() {
return previousAccess;
}
@Override
public void setPreviousInAccessQueue(ReferenceEntry<K, V> previous) {
this.previousAccess = previous;
}
};
// implements Queue
@Override
public boolean offer(ReferenceEntry<K, V> entry) {
// unlink
connectAccessOrder(entry.getPreviousInAccessQueue(), entry.getNextInAccessQueue());
// add to tail
connectAccessOrder(head.getPreviousInAccessQueue(), entry);
connectAccessOrder(entry, head);
return true;
}
@Override
public ReferenceEntry<K, V> peek() {
ReferenceEntry<K, V> next = head.getNextInAccessQueue();
return (next == head) ? null : next;
}
@Override
public ReferenceEntry<K, V> poll() {
ReferenceEntry<K, V> next = head.getNextInAccessQueue();
if (next == head) {
return null;
}
remove(next);
return next;
}
@Override
@SuppressWarnings("unchecked")
public boolean remove(Object o) {
ReferenceEntry<K, V> e = (ReferenceEntry) o;
ReferenceEntry<K, V> previous = e.getPreviousInAccessQueue();
ReferenceEntry<K, V> next = e.getNextInAccessQueue();
connectAccessOrder(previous, next);
nullifyAccessOrder(e);
return next != NullEntry.INSTANCE;
}
@Override
@SuppressWarnings("unchecked")
public boolean contains(Object o) {
ReferenceEntry<K, V> e = (ReferenceEntry) o;
return e.getNextInAccessQueue() != NullEntry.INSTANCE;
}
@Override
public boolean isEmpty() {
return head.getNextInAccessQueue() == head;
}
@Override
public int size() {
int size = 0;
for (ReferenceEntry<K, V> e = head.getNextInAccessQueue(); e != head;
e = e.getNextInAccessQueue()) {
size++;
}
return size;
}
@Override
public void clear() {
ReferenceEntry<K, V> e = head.getNextInAccessQueue();
while (e != head) {
ReferenceEntry<K, V> next = e.getNextInAccessQueue();
nullifyAccessOrder(e);
e = next;
}
head.setNextInAccessQueue(head);
head.setPreviousInAccessQueue(head);
}
@Override
public Iterator<ReferenceEntry<K, V>> iterator() {
return new AbstractSequentialIterator<ReferenceEntry<K, V>>(peek()) {
@Override
protected ReferenceEntry<K, V> computeNext(ReferenceEntry<K, V> previous) {
ReferenceEntry<K, V> next = previous.getNextInAccessQueue();
return (next == head) ? null : next;
}
};
}
}
// Iterator Support
static class LocalManualCache<K, V> implements Cache<K, V>, Serializable {
private static final long serialVersionUID = 1;
final LocalCache<K, V> localCache;
LocalManualCache(CacheBuilder<? super K, ? super V> builder) {
this(new LocalCache<K, V>(builder, null));
}
// Cache methods
private LocalManualCache(LocalCache<K, V> localCache) {
this.localCache = localCache;
}
@Override
public V getIfPresent(Object key) {
return localCache.getIfPresent(key);
}
// Serialization Support
@Override
public void put(K key, V value) {
localCache.put(key, value);
}
}
static class LocalLoadingCache<K, V>
extends LocalManualCache<K, V> implements LoadingCache<K, V> {
private static final long serialVersionUID = 1;
// LoadingCache methods
LocalLoadingCache(CacheBuilder<? super K, ? super V> builder,
CacheLoader<? super K, V> loader) {
super(new LocalCache<K, V>(builder, checkNotNull(loader)));
}
@Override
public V get(K key) throws ExecutionException {
return localCache.getOrLoad(key);
}
public V getUnchecked(K key) {
try {
return get(key);
} catch (ExecutionException e) {
throw new UncheckedExecutionException(e.getCause());
}
}
// Serialization Support
@Override
public final V apply(K key) {
return getUnchecked(key);
}
}
abstract class HashIterator<T> implements Iterator<T> {
int nextSegmentIndex;
int nextTableIndex;
Segment<K, V> currentSegment;
AtomicReferenceArray<ReferenceEntry<K, V>> currentTable;
ReferenceEntry<K, V> nextEntry;
WriteThroughEntry nextExternal;
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 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 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 true if the entry was valid, false if it should be
* skipped.
*/
boolean advanceTo(ReferenceEntry<K, V> entry) {
try {
long now = ticker.read();
K key = entry.getKey();
V value = getLiveValue(entry, now);
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() {
checkState(lastReturned != null);
LocalCache.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 implements Entry<K, V> {
final K key; // non-null
final 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(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) {
throw new UnsupportedOperationException();
}
/**
* Returns a string representation of the form <code>{key}={value}</code>.
*/
@Override
public String toString() {
return getKey() + "=" + getValue();
}
}
final class EntryIterator extends HashIterator<Entry<K, V>> {
@Override
public Entry<K, V> next() {
return nextEntry();
}
}
// Serialization Support
abstract class AbstractCacheSet<T> extends AbstractSet<T> {
final ConcurrentMap<?, ?> map;
AbstractCacheSet(ConcurrentMap<?, ?> map) {
this.map = map;
}
@Override
public int size() {
return map.size();
}
@Override
public boolean isEmpty() {
return map.isEmpty();
}
@Override
public void clear() {
map.clear();
}
}
final class KeySet extends AbstractCacheSet<K> {
KeySet(ConcurrentMap<?, ?> map) {
super(map);
}
@Override
public Iterator<K> iterator() {
return new KeyIterator();
}
@Override
public boolean contains(Object o) {
return map.containsKey(o);
}
@Override
public boolean remove(Object o) {
return map.remove(o) != null;
}
}
final class Values extends AbstractCollection<V> {
private final ConcurrentMap<?, ?> map;
Values(ConcurrentMap<?, ?> map) {
this.map = map;
}
@Override
public int size() {
return map.size();
}
@Override
public boolean isEmpty() {
return map.isEmpty();
}
@Override
public void clear() {
map.clear();
}
@Override
public Iterator<V> iterator() {
return new ValueIterator();
}
@Override
public boolean contains(Object o) {
return map.containsValue(o);
}
}
final class EntrySet extends AbstractCacheSet<Entry<K, V>> {
EntrySet(ConcurrentMap<?, ?> map) {
super(map);
}
@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 = LocalCache.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 && LocalCache.this.remove(key, e.getValue());
}
}
}