CompactHashMap.java
/*
* Copyright (C) 2012 The Guava Authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.common.collect;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.collect.CollectPreconditions.checkRemove;
import static com.google.common.collect.CompactHashing.UNSET;
import static com.google.common.collect.Hashing.smearedHash;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Objects;
import com.google.common.base.Preconditions;
import com.google.common.primitives.Ints;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import com.google.j2objc.annotations.WeakOuter;
import java.io.IOException;
import java.io.InvalidObjectException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.AbstractMap;
import java.util.Arrays;
import java.util.Collection;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Set;
import java.util.Spliterator;
import java.util.Spliterators;
import java.util.function.BiConsumer;
import java.util.function.BiFunction;
import java.util.function.Consumer;
import org.checkerframework.checker.nullness.qual.Nullable;
/**
* CompactHashMap is an implementation of a Map. All optional operations (put and remove) are
* supported. Null keys and values are supported.
*
* <p>{@code containsKey(k)}, {@code put(k, v)} and {@code remove(k)} are all (expected and
* amortized) constant time operations. Expected in the hashtable sense (depends on the hash
* function doing a good job of distributing the elements to the buckets to a distribution not far
* from uniform), and amortized since some operations can trigger a hash table resize.
*
* <p>Unlike {@code java.util.HashMap}, iteration is only proportional to the actual {@code size()},
* which is optimal, and <i>not</i> the size of the internal hashtable, which could be much larger
* than {@code size()}. Furthermore, this structure places significantly reduced load on the garbage
* collector by only using a constant number of internal objects.
*
* <p>If there are no removals, then iteration order for the {@link #entrySet}, {@link #keySet}, and
* {@link #values} views is the same as insertion order. Any removal invalidates any ordering
* guarantees.
*
* <p>This class should not be assumed to be universally superior to {@code java.util.HashMap}.
* Generally speaking, this class reduces object allocation and memory consumption at the price of
* moderately increased constant factors of CPU. Only use this class when there is a specific reason
* to prioritize memory over CPU.
*
* @author Louis Wasserman
* @author Jon Noack
*/
@GwtIncompatible // not worth using in GWT for now
class CompactHashMap<K, V> extends AbstractMap<K, V> implements Serializable {
/*
* TODO: Make this a drop-in replacement for j.u. versions, actually drop them in, and test the
* world. Figure out what sort of space-time tradeoff we're actually going to get here with the
* *Map variants. This class is particularly hard to benchmark, because the benefit is not only in
* less allocation, but also having the GC do less work to scan the heap because of fewer
* references, which is particularly hard to quantify.
*/
/** Creates an empty {@code CompactHashMap} instance. */
public static <K, V> CompactHashMap<K, V> create() {
return new CompactHashMap<>();
}
/**
* Creates a {@code CompactHashMap} instance, with a high enough "initial capacity" that it
* <i>should</i> hold {@code expectedSize} elements without growth.
*
* @param expectedSize the number of elements you expect to add to the returned set
* @return a new, empty {@code CompactHashMap} with enough capacity to hold {@code expectedSize}
* elements without resizing
* @throws IllegalArgumentException if {@code expectedSize} is negative
*/
public static <K, V> CompactHashMap<K, V> createWithExpectedSize(int expectedSize) {
return new CompactHashMap<>(expectedSize);
}
private static final Object NOT_FOUND = new Object();
/**
* Maximum allowed false positive probability of detecting a hash flooding attack given random
* input.
*/
@VisibleForTesting(
)
static final double HASH_FLOODING_FPP = 0.001;
/**
* Maximum allowed length of a hash table bucket before falling back to a j.u.LinkedHashMap-based
* implementation. Experimentally determined.
*/
private static final int MAX_HASH_BUCKET_LENGTH = 9;
/**
* The hashtable object. This can be either:
*
* <ul>
* <li>a byte[], short[], or int[], with size a power of two, created by
* CompactHashing.createTable, whose values are either
* <ul>
* <li>UNSET, meaning "null pointer"
* <li>one plus an index into the keys, values, and entries arrays
* </ul>
* <li>another java.util.Map delegate implementation. In most modern JDKs, normal java.util hash
* collections intelligently fall back to a binary search tree if hash table collisions are
* detected. Rather than going to all the trouble of reimplementing this ourselves, we
* simply switch over to use the JDK implementation wholesale if probable hash flooding is
* detected, sacrificing the compactness guarantee in very rare cases in exchange for much
* more reliable worst-case behavior.
* <li>null, if no entries have yet been added to the map
* </ul>
*/
@Nullable private transient Object table;
/**
* Contains the logical entries, in the range of [0, size()). The high bits of each int are the
* part of the smeared hash of the key not covered by the hashtable mask, whereas the low bits are
* the "next" pointer (pointing to the next entry in the bucket chain), which will always be less
* than or equal to the hashtable mask.
*
* <pre>
* hash = aaaaaaaa
* mask = 0000ffff
* next = 0000bbbb
* entry = aaaabbbb
* </pre>
*
* <p>The pointers in [size(), entries.length) are all "null" (UNSET).
*/
@VisibleForTesting transient int @Nullable [] entries;
/**
* The keys of the entries in the map, in the range of [0, size()). The keys in [size(),
* keys.length) are all {@code null}.
*/
@VisibleForTesting transient Object @Nullable [] keys;
/**
* The values of the entries in the map, in the range of [0, size()). The values in [size(),
* values.length) are all {@code null}.
*/
@VisibleForTesting transient Object @Nullable [] values;
/**
* Keeps track of metadata like the number of hash table bits and modifications of this data
* structure (to make it possible to throw ConcurrentModificationException in the iterator). Note
* that we choose not to make this volatile, so we do less of a "best effort" to track such
* errors, for better performance.
*/
private transient int metadata;
/** The number of elements contained in the set. */
private transient int size;
/** Constructs a new empty instance of {@code CompactHashMap}. */
CompactHashMap() {
init(CompactHashing.DEFAULT_SIZE);
}
/**
* Constructs a new instance of {@code CompactHashMap} with the specified capacity.
*
* @param expectedSize the initial capacity of this {@code CompactHashMap}.
*/
CompactHashMap(int expectedSize) {
init(expectedSize);
}
/** Pseudoconstructor for serialization support. */
void init(int expectedSize) {
Preconditions.checkArgument(expectedSize >= 0, "Expected size must be >= 0");
// Save expectedSize for use in allocArrays()
this.metadata = Ints.constrainToRange(expectedSize, 1, CompactHashing.MAX_SIZE);
}
/** Returns whether arrays need to be allocated. */
@VisibleForTesting
boolean needsAllocArrays() {
return table == null;
}
/** Handle lazy allocation of arrays. */
@CanIgnoreReturnValue
int allocArrays() {
Preconditions.checkState(needsAllocArrays(), "Arrays already allocated");
int expectedSize = metadata;
int buckets = CompactHashing.tableSize(expectedSize);
this.table = CompactHashing.createTable(buckets);
setHashTableMask(buckets - 1);
this.entries = new int[expectedSize];
this.keys = new Object[expectedSize];
this.values = new Object[expectedSize];
return expectedSize;
}
@SuppressWarnings("unchecked")
@VisibleForTesting
@Nullable
Map<K, V> delegateOrNull() {
if (table instanceof Map) {
return (Map<K, V>) table;
}
return null;
}
Map<K, V> createHashFloodingResistantDelegate(int tableSize) {
return new LinkedHashMap<>(tableSize, 1.0f);
}
@SuppressWarnings("unchecked")
@VisibleForTesting
@CanIgnoreReturnValue
Map<K, V> convertToHashFloodingResistantImplementation() {
Map<K, V> newDelegate = createHashFloodingResistantDelegate(hashTableMask() + 1);
for (int i = firstEntryIndex(); i >= 0; i = getSuccessor(i)) {
newDelegate.put((K) keys[i], (V) values[i]);
}
this.table = newDelegate;
this.entries = null;
this.keys = null;
this.values = null;
incrementModCount();
return newDelegate;
}
/** Stores the hash table mask as the number of bits needed to represent an index. */
private void setHashTableMask(int mask) {
int hashTableBits = Integer.SIZE - Integer.numberOfLeadingZeros(mask);
metadata =
CompactHashing.maskCombine(metadata, hashTableBits, CompactHashing.HASH_TABLE_BITS_MASK);
}
/** Gets the hash table mask using the stored number of hash table bits. */
private int hashTableMask() {
return (1 << (metadata & CompactHashing.HASH_TABLE_BITS_MASK)) - 1;
}
void incrementModCount() {
metadata += CompactHashing.MODIFICATION_COUNT_INCREMENT;
}
/**
* Mark an access of the specified entry. Used only in {@code CompactLinkedHashMap} for LRU
* ordering.
*/
void accessEntry(int index) {
// no-op by default
}
@CanIgnoreReturnValue
@Override
public @Nullable V put(@Nullable K key, @Nullable V value) {
if (needsAllocArrays()) {
allocArrays();
}
@Nullable Map<K, V> delegate = delegateOrNull();
if (delegate != null) {
return delegate.put(key, value);
}
int[] entries = this.entries;
Object[] keys = this.keys;
Object[] values = this.values;
int newEntryIndex = this.size; // current size, and pointer to the entry to be appended
int newSize = newEntryIndex + 1;
int hash = smearedHash(key);
int mask = hashTableMask();
int tableIndex = hash & mask;
int next = CompactHashing.tableGet(table, tableIndex);
if (next == UNSET) { // uninitialized bucket
if (newSize > mask) {
// Resize and add new entry
mask = resizeTable(mask, CompactHashing.newCapacity(mask), hash, newEntryIndex);
} else {
CompactHashing.tableSet(table, tableIndex, newEntryIndex + 1);
}
} else {
int entryIndex;
int entry;
int hashPrefix = CompactHashing.getHashPrefix(hash, mask);
int bucketLength = 0;
do {
entryIndex = next - 1;
entry = entries[entryIndex];
if (CompactHashing.getHashPrefix(entry, mask) == hashPrefix
&& Objects.equal(key, keys[entryIndex])) {
@SuppressWarnings("unchecked") // known to be a V
@Nullable
V oldValue = (V) values[entryIndex];
values[entryIndex] = value;
accessEntry(entryIndex);
return oldValue;
}
next = CompactHashing.getNext(entry, mask);
bucketLength++;
} while (next != UNSET);
if (bucketLength >= MAX_HASH_BUCKET_LENGTH) {
return convertToHashFloodingResistantImplementation().put(key, value);
}
if (newSize > mask) {
// Resize and add new entry
mask = resizeTable(mask, CompactHashing.newCapacity(mask), hash, newEntryIndex);
} else {
entries[entryIndex] = CompactHashing.maskCombine(entry, newEntryIndex + 1, mask);
}
}
resizeMeMaybe(newSize);
insertEntry(newEntryIndex, key, value, hash, mask);
this.size = newSize;
incrementModCount();
return null;
}
/**
* Creates a fresh entry with the specified object at the specified position in the entry arrays.
*/
void insertEntry(int entryIndex, @Nullable K key, @Nullable V value, int hash, int mask) {
this.entries[entryIndex] = CompactHashing.maskCombine(hash, UNSET, mask);
this.keys[entryIndex] = key;
this.values[entryIndex] = value;
}
/** Resizes the entries storage if necessary. */
private void resizeMeMaybe(int newSize) {
int entriesSize = entries.length;
if (newSize > entriesSize) {
// 1.5x but round up to nearest odd (this is optimal for memory consumption on Android)
int newCapacity =
Math.min(CompactHashing.MAX_SIZE, (entriesSize + Math.max(1, entriesSize >>> 1)) | 1);
if (newCapacity != entriesSize) {
resizeEntries(newCapacity);
}
}
}
/**
* Resizes the internal entries array to the specified capacity, which may be greater or less than
* the current capacity.
*/
void resizeEntries(int newCapacity) {
this.entries = Arrays.copyOf(entries, newCapacity);
this.keys = Arrays.copyOf(keys, newCapacity);
this.values = Arrays.copyOf(values, newCapacity);
}
@CanIgnoreReturnValue
private int resizeTable(int mask, int newCapacity, int targetHash, int targetEntryIndex) {
Object newTable = CompactHashing.createTable(newCapacity);
int newMask = newCapacity - 1;
if (targetEntryIndex != UNSET) {
// Add target first; it must be last in the chain because its entry hasn't yet been created
CompactHashing.tableSet(newTable, targetHash & newMask, targetEntryIndex + 1);
}
Object table = this.table;
int[] entries = this.entries;
// Loop over current hashtable
for (int tableIndex = 0; tableIndex <= mask; tableIndex++) {
int next = CompactHashing.tableGet(table, tableIndex);
while (next != UNSET) {
int entryIndex = next - 1;
int entry = entries[entryIndex];
// Rebuild hash using entry hashPrefix and tableIndex ("hashSuffix")
int hash = CompactHashing.getHashPrefix(entry, mask) | tableIndex;
int newTableIndex = hash & newMask;
int newNext = CompactHashing.tableGet(newTable, newTableIndex);
CompactHashing.tableSet(newTable, newTableIndex, next);
entries[entryIndex] = CompactHashing.maskCombine(hash, newNext, newMask);
next = CompactHashing.getNext(entry, mask);
}
}
this.table = newTable;
setHashTableMask(newMask);
return newMask;
}
private int indexOf(@Nullable Object key) {
if (needsAllocArrays()) {
return -1;
}
int hash = smearedHash(key);
int mask = hashTableMask();
int next = CompactHashing.tableGet(table, hash & mask);
if (next == UNSET) {
return -1;
}
int hashPrefix = CompactHashing.getHashPrefix(hash, mask);
do {
int entryIndex = next - 1;
int entry = entries[entryIndex];
if (CompactHashing.getHashPrefix(entry, mask) == hashPrefix
&& Objects.equal(key, keys[entryIndex])) {
return entryIndex;
}
next = CompactHashing.getNext(entry, mask);
} while (next != UNSET);
return -1;
}
@Override
public boolean containsKey(@Nullable Object key) {
@Nullable Map<K, V> delegate = delegateOrNull();
return (delegate != null) ? delegate.containsKey(key) : indexOf(key) != -1;
}
@SuppressWarnings("unchecked") // known to be a V
@Override
public V get(@Nullable Object key) {
@Nullable Map<K, V> delegate = delegateOrNull();
if (delegate != null) {
return delegate.get(key);
}
int index = indexOf(key);
if (index == -1) {
return null;
}
accessEntry(index);
return (V) values[index];
}
@CanIgnoreReturnValue
@SuppressWarnings("unchecked") // known to be a V
@Override
public @Nullable V remove(@Nullable Object key) {
@Nullable Map<K, V> delegate = delegateOrNull();
if (delegate != null) {
return delegate.remove(key);
}
Object oldValue = removeHelper(key);
return (oldValue == NOT_FOUND) ? null : (V) oldValue;
}
private @Nullable Object removeHelper(@Nullable Object key) {
if (needsAllocArrays()) {
return NOT_FOUND;
}
int mask = hashTableMask();
int index =
CompactHashing.remove(
key, /* value= */ null, mask, table, entries, keys, /* values= */ null);
if (index == -1) {
return NOT_FOUND;
}
@Nullable Object oldValue = values[index];
moveLastEntry(index, mask);
size--;
incrementModCount();
return oldValue;
}
/**
* Moves the last entry in the entry array into {@code dstIndex}, and nulls out its old position.
*/
void moveLastEntry(int dstIndex, int mask) {
int srcIndex = size() - 1;
if (dstIndex < srcIndex) {
// move last entry to deleted spot
@Nullable Object key = keys[srcIndex];
keys[dstIndex] = key;
values[dstIndex] = values[srcIndex];
keys[srcIndex] = null;
values[srcIndex] = null;
// move the last entry to the removed spot, just like we moved the element
entries[dstIndex] = entries[srcIndex];
entries[srcIndex] = 0;
// also need to update whoever's "next" pointer was pointing to the last entry place
int tableIndex = smearedHash(key) & mask;
int next = CompactHashing.tableGet(table, tableIndex);
int srcNext = srcIndex + 1;
if (next == srcNext) {
// we need to update the root pointer
CompactHashing.tableSet(table, tableIndex, dstIndex + 1);
} else {
// we need to update a pointer in an entry
int entryIndex;
int entry;
do {
entryIndex = next - 1;
entry = entries[entryIndex];
next = CompactHashing.getNext(entry, mask);
} while (next != srcNext);
// here, entries[entryIndex] points to the old entry location; update it
entries[entryIndex] = CompactHashing.maskCombine(entry, dstIndex + 1, mask);
}
} else {
keys[dstIndex] = null;
values[dstIndex] = null;
entries[dstIndex] = 0;
}
}
int firstEntryIndex() {
return isEmpty() ? -1 : 0;
}
int getSuccessor(int entryIndex) {
return (entryIndex + 1 < size) ? entryIndex + 1 : -1;
}
/**
* Updates the index an iterator is pointing to after a call to remove: returns the index of the
* entry that should be looked at after a removal on indexRemoved, with indexBeforeRemove as the
* index that *was* the next entry that would be looked at.
*/
int adjustAfterRemove(int indexBeforeRemove, @SuppressWarnings("unused") int indexRemoved) {
return indexBeforeRemove - 1;
}
private abstract class Itr<T> implements Iterator<T> {
int expectedMetadata = metadata;
int currentIndex = firstEntryIndex();
int indexToRemove = -1;
@Override
public boolean hasNext() {
return currentIndex >= 0;
}
abstract T getOutput(int entry);
@Override
public T next() {
checkForConcurrentModification();
if (!hasNext()) {
throw new NoSuchElementException();
}
indexToRemove = currentIndex;
T result = getOutput(currentIndex);
currentIndex = getSuccessor(currentIndex);
return result;
}
@Override
public void remove() {
checkForConcurrentModification();
checkRemove(indexToRemove >= 0);
incrementExpectedModCount();
CompactHashMap.this.remove(keys[indexToRemove]);
currentIndex = adjustAfterRemove(currentIndex, indexToRemove);
indexToRemove = -1;
}
void incrementExpectedModCount() {
expectedMetadata += CompactHashing.MODIFICATION_COUNT_INCREMENT;
}
private void checkForConcurrentModification() {
if (metadata != expectedMetadata) {
throw new ConcurrentModificationException();
}
}
}
@SuppressWarnings("unchecked") // known to be Ks and Vs
@Override
public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
checkNotNull(function);
@Nullable Map<K, V> delegate = delegateOrNull();
if (delegate != null) {
delegate.replaceAll(function);
} else {
for (int i = 0; i < size; i++) {
values[i] = function.apply((K) keys[i], (V) values[i]);
}
}
}
private transient @Nullable Set<K> keySetView;
@Override
public Set<K> keySet() {
return (keySetView == null) ? keySetView = createKeySet() : keySetView;
}
Set<K> createKeySet() {
return new KeySetView();
}
@WeakOuter
class KeySetView extends Maps.KeySet<K, V> {
KeySetView() {
super(CompactHashMap.this);
}
@Override
public Object[] toArray() {
if (needsAllocArrays()) {
return new Object[0];
}
@Nullable Map<K, V> delegate = delegateOrNull();
return (delegate != null)
? delegate.keySet().toArray()
: ObjectArrays.copyAsObjectArray(keys, 0, size);
}
@Override
public <T> T[] toArray(T[] a) {
if (needsAllocArrays()) {
if (a.length > 0) {
a[0] = null;
}
return a;
}
@Nullable Map<K, V> delegate = delegateOrNull();
return (delegate != null)
? delegate.keySet().toArray(a)
: ObjectArrays.toArrayImpl(keys, 0, size, a);
}
@Override
public boolean remove(@Nullable Object o) {
@Nullable Map<K, V> delegate = delegateOrNull();
return (delegate != null)
? delegate.keySet().remove(o)
: CompactHashMap.this.removeHelper(o) != NOT_FOUND;
}
@Override
public Iterator<K> iterator() {
return keySetIterator();
}
@Override
public Spliterator<K> spliterator() {
if (needsAllocArrays()) {
return Spliterators.spliterator(new Object[0], Spliterator.DISTINCT | Spliterator.ORDERED);
}
@Nullable Map<K, V> delegate = delegateOrNull();
return (delegate != null)
? delegate.keySet().spliterator()
: Spliterators.spliterator(keys, 0, size, Spliterator.DISTINCT | Spliterator.ORDERED);
}
@SuppressWarnings("unchecked") // known to be Ks
@Override
public void forEach(Consumer<? super K> action) {
checkNotNull(action);
@Nullable Map<K, V> delegate = delegateOrNull();
if (delegate != null) {
delegate.keySet().forEach(action);
} else {
for (int i = firstEntryIndex(); i >= 0; i = getSuccessor(i)) {
action.accept((K) keys[i]);
}
}
}
}
Iterator<K> keySetIterator() {
@Nullable Map<K, V> delegate = delegateOrNull();
if (delegate != null) {
return delegate.keySet().iterator();
}
return new Itr<K>() {
@SuppressWarnings("unchecked") // known to be a K
@Override
K getOutput(int entry) {
return (K) keys[entry];
}
};
}
@SuppressWarnings("unchecked") // known to be Ks and Vs
@Override
public void forEach(BiConsumer<? super K, ? super V> action) {
checkNotNull(action);
@Nullable Map<K, V> delegate = delegateOrNull();
if (delegate != null) {
delegate.forEach(action);
} else {
for (int i = firstEntryIndex(); i >= 0; i = getSuccessor(i)) {
action.accept((K) keys[i], (V) values[i]);
}
}
}
private transient @Nullable Set<Entry<K, V>> entrySetView;
@Override
public Set<Entry<K, V>> entrySet() {
return (entrySetView == null) ? entrySetView = createEntrySet() : entrySetView;
}
Set<Entry<K, V>> createEntrySet() {
return new EntrySetView();
}
@WeakOuter
class EntrySetView extends Maps.EntrySet<K, V> {
@Override
Map<K, V> map() {
return CompactHashMap.this;
}
@Override
public Iterator<Entry<K, V>> iterator() {
return entrySetIterator();
}
@Override
public Spliterator<Entry<K, V>> spliterator() {
@Nullable Map<K, V> delegate = delegateOrNull();
return (delegate != null)
? delegate.entrySet().spliterator()
: CollectSpliterators.indexed(
size, Spliterator.DISTINCT | Spliterator.ORDERED, MapEntry::new);
}
@Override
public boolean contains(@Nullable Object o) {
@Nullable Map<K, V> delegate = delegateOrNull();
if (delegate != null) {
return delegate.entrySet().contains(o);
} else if (o instanceof Entry) {
Entry<?, ?> entry = (Entry<?, ?>) o;
int index = indexOf(entry.getKey());
return index != -1 && Objects.equal(values[index], entry.getValue());
}
return false;
}
@Override
public boolean remove(@Nullable Object o) {
@Nullable Map<K, V> delegate = delegateOrNull();
if (delegate != null) {
return delegate.entrySet().remove(o);
} else if (o instanceof Entry) {
Entry<?, ?> entry = (Entry<?, ?>) o;
if (needsAllocArrays()) {
return false;
}
int mask = hashTableMask();
int index =
CompactHashing.remove(
entry.getKey(), entry.getValue(), mask, table, entries, keys, values);
if (index == -1) {
return false;
}
moveLastEntry(index, mask);
size--;
incrementModCount();
return true;
}
return false;
}
}
Iterator<Entry<K, V>> entrySetIterator() {
@Nullable Map<K, V> delegate = delegateOrNull();
if (delegate != null) {
return delegate.entrySet().iterator();
}
return new Itr<Entry<K, V>>() {
@Override
Entry<K, V> getOutput(int entry) {
return new MapEntry(entry);
}
};
}
final class MapEntry extends AbstractMapEntry<K, V> {
private final @Nullable K key;
private int lastKnownIndex;
@SuppressWarnings("unchecked") // known to be a K
MapEntry(int index) {
this.key = (K) keys[index];
this.lastKnownIndex = index;
}
@Nullable
@Override
public K getKey() {
return key;
}
private void updateLastKnownIndex() {
if (lastKnownIndex == -1
|| lastKnownIndex >= size()
|| !Objects.equal(key, keys[lastKnownIndex])) {
lastKnownIndex = indexOf(key);
}
}
@SuppressWarnings("unchecked") // known to be a V
@Override
public @Nullable V getValue() {
@Nullable Map<K, V> delegate = delegateOrNull();
if (delegate != null) {
return delegate.get(key);
}
updateLastKnownIndex();
return (lastKnownIndex == -1) ? null : (V) values[lastKnownIndex];
}
@SuppressWarnings("unchecked") // known to be a V
@Override
public V setValue(V value) {
@Nullable Map<K, V> delegate = delegateOrNull();
if (delegate != null) {
return delegate.put(key, value);
}
updateLastKnownIndex();
if (lastKnownIndex == -1) {
put(key, value);
return null;
} else {
V old = (V) values[lastKnownIndex];
values[lastKnownIndex] = value;
return old;
}
}
}
@Override
public int size() {
@Nullable Map<K, V> delegate = delegateOrNull();
return (delegate != null) ? delegate.size() : size;
}
@Override
public boolean isEmpty() {
return size() == 0;
}
@Override
public boolean containsValue(@Nullable Object value) {
@Nullable Map<K, V> delegate = delegateOrNull();
if (delegate != null) {
return delegate.containsValue(value);
}
for (int i = 0; i < size; i++) {
if (Objects.equal(value, values[i])) {
return true;
}
}
return false;
}
private transient @Nullable Collection<V> valuesView;
@Override
public Collection<V> values() {
return (valuesView == null) ? valuesView = createValues() : valuesView;
}
Collection<V> createValues() {
return new ValuesView();
}
@WeakOuter
class ValuesView extends Maps.Values<K, V> {
ValuesView() {
super(CompactHashMap.this);
}
@Override
public Iterator<V> iterator() {
return valuesIterator();
}
@SuppressWarnings("unchecked") // known to be Vs
@Override
public void forEach(Consumer<? super V> action) {
checkNotNull(action);
@Nullable Map<K, V> delegate = delegateOrNull();
if (delegate != null) {
delegate.values().forEach(action);
} else {
for (int i = firstEntryIndex(); i >= 0; i = getSuccessor(i)) {
action.accept((V) values[i]);
}
}
}
@Override
public Spliterator<V> spliterator() {
if (needsAllocArrays()) {
return Spliterators.spliterator(new Object[0], Spliterator.ORDERED);
}
@Nullable Map<K, V> delegate = delegateOrNull();
return (delegate != null)
? delegate.values().spliterator()
: Spliterators.spliterator(values, 0, size, Spliterator.ORDERED);
}
@Override
public Object[] toArray() {
if (needsAllocArrays()) {
return new Object[0];
}
@Nullable Map<K, V> delegate = delegateOrNull();
return (delegate != null)
? delegate.values().toArray()
: ObjectArrays.copyAsObjectArray(values, 0, size);
}
@Override
public <T> T[] toArray(T[] a) {
if (needsAllocArrays()) {
if (a.length > 0) {
a[0] = null;
}
return a;
}
@Nullable Map<K, V> delegate = delegateOrNull();
return (delegate != null)
? delegate.values().toArray(a)
: ObjectArrays.toArrayImpl(values, 0, size, a);
}
}
Iterator<V> valuesIterator() {
@Nullable Map<K, V> delegate = delegateOrNull();
if (delegate != null) {
return delegate.values().iterator();
}
return new Itr<V>() {
@SuppressWarnings("unchecked") // known to be a V
@Override
V getOutput(int entry) {
return (V) values[entry];
}
};
}
/**
* Ensures that this {@code CompactHashMap} has the smallest representation in memory, given its
* current size.
*/
public void trimToSize() {
if (needsAllocArrays()) {
return;
}
@Nullable Map<K, V> delegate = delegateOrNull();
if (delegate != null) {
Map<K, V> newDelegate = createHashFloodingResistantDelegate(size());
newDelegate.putAll(delegate);
this.table = newDelegate;
return;
}
int size = this.size;
if (size < entries.length) {
resizeEntries(size);
}
int minimumTableSize = CompactHashing.tableSize(size);
int mask = hashTableMask();
if (minimumTableSize < mask) { // smaller table size will always be less than current mask
resizeTable(mask, minimumTableSize, UNSET, UNSET);
}
}
@Override
public void clear() {
if (needsAllocArrays()) {
return;
}
incrementModCount();
@Nullable Map<K, V> delegate = delegateOrNull();
if (delegate != null) {
metadata =
Ints.constrainToRange(size(), CompactHashing.DEFAULT_SIZE, CompactHashing.MAX_SIZE);
delegate.clear(); // invalidate any iterators left over!
table = null;
size = 0;
} else {
Arrays.fill(keys, 0, size, null);
Arrays.fill(values, 0, size, null);
CompactHashing.tableClear(table);
Arrays.fill(entries, 0, size, 0);
this.size = 0;
}
}
private void writeObject(ObjectOutputStream stream) throws IOException {
stream.defaultWriteObject();
stream.writeInt(size());
Iterator<Entry<K, V>> entryIterator = entrySetIterator();
while (entryIterator.hasNext()) {
Entry<K, V> e = entryIterator.next();
stream.writeObject(e.getKey());
stream.writeObject(e.getValue());
}
}
@SuppressWarnings("unchecked")
private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException {
stream.defaultReadObject();
int elementCount = stream.readInt();
if (elementCount < 0) {
throw new InvalidObjectException("Invalid size: " + elementCount);
}
init(elementCount);
for (int i = 0; i < elementCount; i++) {
K key = (K) stream.readObject();
V value = (V) stream.readObject();
put(key, value);
}
}
}