com.google.common.collect.CompactHashMap Maven / Gradle / Ivy
/*
* 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 static com.google.common.collect.NullnessCasts.uncheckedCastNullableTToT;
import static com.google.common.collect.NullnessCasts.unsafeNull;
import static java.util.Objects.requireNonNull;
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 javax.annotation.CheckForNull;
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.
*
* {@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.
*
*
Unlike {@code java.util.HashMap}, iteration is only proportional to the actual {@code size()},
* which is optimal, and not 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.
*
*
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.
*
*
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
@ElementTypesAreNonnullByDefault
class CompactHashMap
extends AbstractMap 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
CompactHashMap create() {
return new CompactHashMap<>();
}
/**
* Creates a {@code CompactHashMap} instance, with a high enough "initial capacity" that it
* should 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
CompactHashMap 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 way the `table`, `entries`, `keys`, and `values` arrays work together is as follows.
//
// The `table` array always has a size that is a power of 2. The hashcode of a key in the map
// is masked in order to correspond to the current table size. For example, if the table size
// is 128 then the mask is 127 == 0x7f, keeping the bottom 7 bits of the hash value.
// If a key hashes to 0x89abcdef the mask reduces it to 0x89abcdef & 0x7f == 0x6f. We'll call this
// the "short hash".
//
// The `keys`, `values`, and `entries` arrays always have the same size as each other. They can be
// seen as fields of an imaginary `Entry` object like this:
//
// class Entry {
// int hash;
// Entry next;
// K key;
// V value;
// }
//
// The imaginary `hash` and `next` values are combined into a single `int` value in the `entries`
// array. The top bits of this value are the remaining bits of the hash value that were not used
// in the short hash. We saw that a mask of 0x7f would keep the 7-bit value 0x6f from a full
// hashcode of 0x89abcdef. The imaginary `hash` value would then be the remaining top 25 bits,
// 0x89abcd80. To this is added (or'd) the `next` value, which is an index within `entries`
// (and therefore within `keys` and `values`) of another entry that has the same short hash
// value. In our example, it would be another entry for a key whose short hash is also 0x6f.
//
// Essentially, then, `table[h]` gives us the start of a linked list in `entries`, where every
// element of the list has the short hash value h.
//
// A wrinkle here is that the value 0 (called UNSET in the code) is used as the equivalent of a
// null pointer. If `table[h] == 0` that means there are no keys in the map whose short hash is h.
// If the `next` bits in `entries[i]` are 0 that means there are no further entries for the given
// short hash. But 0 is also a valid index in `entries`, so we add 1 to these indices before
// putting them in `table` or in `next` bits, and subtract 1 again when we need an index value.
//
// The elements of `keys`, `values`, and `entries` are added sequentially, so that elements 0 to
// `size() - 1` are used and remaining elements are not. This makes iteration straightforward.
// Removing an entry generally involves moving the last element of each array to where the removed
// entry was, and adjusting index links accordingly.
/**
* The hashtable object. This can be either:
*
*
* - a byte[], short[], or int[], with size a power of two, created by
* CompactHashing.createTable, whose values are either
*
* - UNSET, meaning "null pointer"
*
- one plus an index into the keys, values, and entries arrays
*
* - 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.
*
- null, if no entries have yet been added to the map
*
*/
@CheckForNull 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.
*
*
* hash = aaaaaaaa
* mask = 00000fff
* next = 00000bbb
* entry = aaaaabbb
*
*
* The pointers in [size(), entries.length) are all "null" (UNSET).
*/
@VisibleForTesting @CheckForNull transient int[] 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 @CheckForNull transient @Nullable Object[] 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 @CheckForNull transient @Nullable Object[] 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.
*
*
For a new instance, where the arrays above have not yet been allocated, the value of {@code
* metadata} is the size that the arrays should be allocated with. Once the arrays have been
* allocated, the value of {@code metadata} combines the number of bits in the "short hash", in
* its bottom {@value CompactHashing#HASH_TABLE_BITS_MAX_BITS} bits, with a modification count in
* the remaining bits that is used to detect concurrent modification during iteration.
*/
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
@CheckForNull
Map delegateOrNull() {
if (table instanceof Map) {
return (Map) table;
}
return null;
}
Map createHashFloodingResistantDelegate(int tableSize) {
return new LinkedHashMap<>(tableSize, 1.0f);
}
@VisibleForTesting
@CanIgnoreReturnValue
Map convertToHashFloodingResistantImplementation() {
Map newDelegate = createHashFloodingResistantDelegate(hashTableMask() + 1);
for (int i = firstEntryIndex(); i >= 0; i = getSuccessor(i)) {
newDelegate.put(key(i), value(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
@CheckForNull
public V put(@ParametricNullness K key, @ParametricNullness V value) {
if (needsAllocArrays()) {
allocArrays();
}
Map delegate = delegateOrNull();
if (delegate != null) {
return delegate.put(key, value);
}
int[] entries = requireEntries();
@Nullable Object[] keys = requireKeys();
@Nullable Object[] values = requireValues();
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(requireTable(), 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(requireTable(), 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
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, @ParametricNullness K key, @ParametricNullness V value, int hash, int mask) {
this.setEntry(entryIndex, CompactHashing.maskCombine(hash, UNSET, mask));
this.setKey(entryIndex, key);
this.setValue(entryIndex, value);
}
/** Resizes the entries storage if necessary. */
private void resizeMeMaybe(int newSize) {
int entriesSize = requireEntries().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(requireEntries(), newCapacity);
this.keys = Arrays.copyOf(requireKeys(), newCapacity);
this.values = Arrays.copyOf(requireValues(), newCapacity);
}
@CanIgnoreReturnValue
private int resizeTable(int oldMask, 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 oldTable = requireTable();
int[] entries = requireEntries();
// Loop over `oldTable` to construct its replacement, ``newTable`. The entries do not move, so
// the `keys` and `values` arrays do not need to change. But because the "short hash" now has a
// different number of bits, we must rewrite each element of `entries` so that its contribution
// to the full hashcode reflects the change, and so that its `next` link corresponds to the new
// linked list of entries with the new short hash.
for (int oldTableIndex = 0; oldTableIndex <= oldMask; oldTableIndex++) {
int oldNext = CompactHashing.tableGet(oldTable, oldTableIndex);
// Each element of `oldTable` is the head of a (possibly empty) linked list of elements in
// `entries`. The `oldNext` loop is going to traverse that linked list.
// We need to rewrite the `next` link of each of the elements so that it is in the appropriate
// linked list starting from `newTable`. In general, each element from the old linked list
// belongs to a different linked list from `newTable`. We insert each element in turn at the
// head of its appropriate `newTable` linked list.
while (oldNext != UNSET) {
int entryIndex = oldNext - 1;
int oldEntry = entries[entryIndex];
// Rebuild the full 32-bit hash using entry hashPrefix and oldTableIndex ("hashSuffix").
int hash = CompactHashing.getHashPrefix(oldEntry, oldMask) | oldTableIndex;
int newTableIndex = hash & newMask;
int newNext = CompactHashing.tableGet(newTable, newTableIndex);
CompactHashing.tableSet(newTable, newTableIndex, oldNext);
entries[entryIndex] = CompactHashing.maskCombine(hash, newNext, newMask);
oldNext = CompactHashing.getNext(oldEntry, oldMask);
}
}
this.table = newTable;
setHashTableMask(newMask);
return newMask;
}
private int indexOf(@CheckForNull Object key) {
if (needsAllocArrays()) {
return -1;
}
int hash = smearedHash(key);
int mask = hashTableMask();
int next = CompactHashing.tableGet(requireTable(), hash & mask);
if (next == UNSET) {
return -1;
}
int hashPrefix = CompactHashing.getHashPrefix(hash, mask);
do {
int entryIndex = next - 1;
int entry = entry(entryIndex);
if (CompactHashing.getHashPrefix(entry, mask) == hashPrefix
&& Objects.equal(key, key(entryIndex))) {
return entryIndex;
}
next = CompactHashing.getNext(entry, mask);
} while (next != UNSET);
return -1;
}
@Override
public boolean containsKey(@CheckForNull Object key) {
Map delegate = delegateOrNull();
return (delegate != null) ? delegate.containsKey(key) : indexOf(key) != -1;
}
@Override
@CheckForNull
public V get(@CheckForNull Object key) {
Map delegate = delegateOrNull();
if (delegate != null) {
return delegate.get(key);
}
int index = indexOf(key);
if (index == -1) {
return null;
}
accessEntry(index);
return value(index);
}
@CanIgnoreReturnValue
@SuppressWarnings("unchecked") // known to be a V
@Override
@CheckForNull
public V remove(@CheckForNull Object key) {
Map delegate = delegateOrNull();
if (delegate != null) {
return delegate.remove(key);
}
Object oldValue = removeHelper(key);
return (oldValue == NOT_FOUND) ? null : (V) oldValue;
}
private @Nullable Object removeHelper(@CheckForNull Object key) {
if (needsAllocArrays()) {
return NOT_FOUND;
}
int mask = hashTableMask();
int index =
CompactHashing.remove(
key,
/* value= */ null,
mask,
requireTable(),
requireEntries(),
requireKeys(),
/* values= */ null);
if (index == -1) {
return NOT_FOUND;
}
Object oldValue = value(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) {
Object table = requireTable();
int[] entries = requireEntries();
@Nullable Object[] keys = requireKeys();
@Nullable Object[] values = requireValues();
int srcIndex = size() - 1;
if (dstIndex < srcIndex) {
// move last entry to deleted spot
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 implements Iterator {
int expectedMetadata = metadata;
int currentIndex = firstEntryIndex();
int indexToRemove = -1;
@Override
public boolean hasNext() {
return currentIndex >= 0;
}
@ParametricNullness
abstract T getOutput(int entry);
@Override
@ParametricNullness
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(key(indexToRemove));
currentIndex = adjustAfterRemove(currentIndex, indexToRemove);
indexToRemove = -1;
}
void incrementExpectedModCount() {
expectedMetadata += CompactHashing.MODIFICATION_COUNT_INCREMENT;
}
private void checkForConcurrentModification() {
if (metadata != expectedMetadata) {
throw new ConcurrentModificationException();
}
}
}
@Override
public void replaceAll(BiFunction function) {
checkNotNull(function);
Map delegate = delegateOrNull();
if (delegate != null) {
delegate.replaceAll(function);
} else {
for (int i = 0; i < size; i++) {
setValue(i, function.apply(key(i), value(i)));
}
}
}
@CheckForNull private transient Set keySetView;
@Override
public Set keySet() {
return (keySetView == null) ? keySetView = createKeySet() : keySetView;
}
Set createKeySet() {
return new KeySetView();
}
@WeakOuter
class KeySetView extends Maps.KeySet {
KeySetView() {
super(CompactHashMap.this);
}
@Override
public @Nullable Object[] toArray() {
if (needsAllocArrays()) {
return new Object[0];
}
Map delegate = delegateOrNull();
return (delegate != null)
? delegate.keySet().toArray()
: ObjectArrays.copyAsObjectArray(requireKeys(), 0, size);
}
@Override
@SuppressWarnings("nullness") // b/192354773 in our checker affects toArray declarations
public T[] toArray(T[] a) {
if (needsAllocArrays()) {
if (a.length > 0) {
@Nullable Object[] unsoundlyCovariantArray = a;
unsoundlyCovariantArray[0] = null;
}
return a;
}
Map delegate = delegateOrNull();
return (delegate != null)
? delegate.keySet().toArray(a)
: ObjectArrays.toArrayImpl(requireKeys(), 0, size, a);
}
@Override
public boolean remove(@CheckForNull Object o) {
Map delegate = delegateOrNull();
return (delegate != null)
? delegate.keySet().remove(o)
: CompactHashMap.this.removeHelper(o) != NOT_FOUND;
}
@Override
public Iterator iterator() {
return keySetIterator();
}
@Override
public Spliterator spliterator() {
if (needsAllocArrays()) {
return Spliterators.spliterator(new Object[0], Spliterator.DISTINCT | Spliterator.ORDERED);
}
Map delegate = delegateOrNull();
return (delegate != null)
? delegate.keySet().spliterator()
: Spliterators.spliterator(
requireKeys(), 0, size, Spliterator.DISTINCT | Spliterator.ORDERED);
}
@Override
public void forEach(Consumer action) {
checkNotNull(action);
Map delegate = delegateOrNull();
if (delegate != null) {
delegate.keySet().forEach(action);
} else {
for (int i = firstEntryIndex(); i >= 0; i = getSuccessor(i)) {
action.accept(key(i));
}
}
}
}
Iterator keySetIterator() {
Map delegate = delegateOrNull();
if (delegate != null) {
return delegate.keySet().iterator();
}
return new Itr() {
@Override
@ParametricNullness
K getOutput(int entry) {
return key(entry);
}
};
}
@Override
public void forEach(BiConsumer action) {
checkNotNull(action);
Map delegate = delegateOrNull();
if (delegate != null) {
delegate.forEach(action);
} else {
for (int i = firstEntryIndex(); i >= 0; i = getSuccessor(i)) {
action.accept(key(i), value(i));
}
}
}
@CheckForNull private transient Set> entrySetView;
@Override
public Set> entrySet() {
return (entrySetView == null) ? entrySetView = createEntrySet() : entrySetView;
}
Set> createEntrySet() {
return new EntrySetView();
}
@WeakOuter
class EntrySetView extends Maps.EntrySet {
@Override
Map map() {
return CompactHashMap.this;
}
@Override
public Iterator> iterator() {
return entrySetIterator();
}
@Override
public Spliterator> spliterator() {
Map delegate = delegateOrNull();
return (delegate != null)
? delegate.entrySet().spliterator()
: CollectSpliterators.indexed(
size, Spliterator.DISTINCT | Spliterator.ORDERED, MapEntry::new);
}
@Override
public boolean contains(@CheckForNull Object o) {
Map 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(value(index), entry.getValue());
}
return false;
}
@Override
public boolean remove(@CheckForNull Object o) {
Map 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,
requireTable(),
requireEntries(),
requireKeys(),
requireValues());
if (index == -1) {
return false;
}
moveLastEntry(index, mask);
size--;
incrementModCount();
return true;
}
return false;
}
}
Iterator> entrySetIterator() {
Map delegate = delegateOrNull();
if (delegate != null) {
return delegate.entrySet().iterator();
}
return new Itr>() {
@Override
Entry getOutput(int entry) {
return new MapEntry(entry);
}
};
}
final class MapEntry extends AbstractMapEntry {
@ParametricNullness private final K key;
private int lastKnownIndex;
MapEntry(int index) {
this.key = key(index);
this.lastKnownIndex = index;
}
@Override
@ParametricNullness
public K getKey() {
return key;
}
private void updateLastKnownIndex() {
if (lastKnownIndex == -1
|| lastKnownIndex >= size()
|| !Objects.equal(key, key(lastKnownIndex))) {
lastKnownIndex = indexOf(key);
}
}
@Override
@ParametricNullness
public V getValue() {
Map delegate = delegateOrNull();
if (delegate != null) {
/*
* The cast is safe because the entry is present in the map. Or, if it has been removed by a
* concurrent modification, behavior is undefined.
*/
return uncheckedCastNullableTToT(delegate.get(key));
}
updateLastKnownIndex();
/*
* If the entry has been removed from the map, we return null, even though that might not be a
* valid value. That's the best we can do, short of holding a reference to the most recently
* seen value. And while we *could* do that, we aren't required to: Map.Entry explicitly says
* that behavior is undefined when the backing map is modified through another API. (It even
* permits us to throw IllegalStateException. Maybe we should have done that, but we probably
* shouldn't change now for fear of breaking people.)
*/
return (lastKnownIndex == -1) ? unsafeNull() : value(lastKnownIndex);
}
@Override
@ParametricNullness
public V setValue(@ParametricNullness V value) {
Map delegate = delegateOrNull();
if (delegate != null) {
return uncheckedCastNullableTToT(delegate.put(key, value)); // See discussion in getValue().
}
updateLastKnownIndex();
if (lastKnownIndex == -1) {
put(key, value);
return unsafeNull(); // See discussion in getValue().
} else {
V old = value(lastKnownIndex);
CompactHashMap.this.setValue(lastKnownIndex, value);
return old;
}
}
}
@Override
public int size() {
Map delegate = delegateOrNull();
return (delegate != null) ? delegate.size() : size;
}
@Override
public boolean isEmpty() {
return size() == 0;
}
@Override
public boolean containsValue(@CheckForNull Object value) {
Map delegate = delegateOrNull();
if (delegate != null) {
return delegate.containsValue(value);
}
for (int i = 0; i < size; i++) {
if (Objects.equal(value, value(i))) {
return true;
}
}
return false;
}
@CheckForNull private transient Collection valuesView;
@Override
public Collection values() {
return (valuesView == null) ? valuesView = createValues() : valuesView;
}
Collection createValues() {
return new ValuesView();
}
@WeakOuter
class ValuesView extends Maps.Values {
ValuesView() {
super(CompactHashMap.this);
}
@Override
public Iterator iterator() {
return valuesIterator();
}
@Override
public void forEach(Consumer action) {
checkNotNull(action);
Map delegate = delegateOrNull();
if (delegate != null) {
delegate.values().forEach(action);
} else {
for (int i = firstEntryIndex(); i >= 0; i = getSuccessor(i)) {
action.accept(value(i));
}
}
}
@Override
public Spliterator spliterator() {
if (needsAllocArrays()) {
return Spliterators.spliterator(new Object[0], Spliterator.ORDERED);
}
Map delegate = delegateOrNull();
return (delegate != null)
? delegate.values().spliterator()
: Spliterators.spliterator(requireValues(), 0, size, Spliterator.ORDERED);
}
@Override
public @Nullable Object[] toArray() {
if (needsAllocArrays()) {
return new Object[0];
}
Map delegate = delegateOrNull();
return (delegate != null)
? delegate.values().toArray()
: ObjectArrays.copyAsObjectArray(requireValues(), 0, size);
}
@Override
@SuppressWarnings("nullness") // b/192354773 in our checker affects toArray declarations
public T[] toArray(T[] a) {
if (needsAllocArrays()) {
if (a.length > 0) {
@Nullable Object[] unsoundlyCovariantArray = a;
unsoundlyCovariantArray[0] = null;
}
return a;
}
Map delegate = delegateOrNull();
return (delegate != null)
? delegate.values().toArray(a)
: ObjectArrays.toArrayImpl(requireValues(), 0, size, a);
}
}
Iterator valuesIterator() {
Map delegate = delegateOrNull();
if (delegate != null) {
return delegate.values().iterator();
}
return new Itr() {
@Override
@ParametricNullness
V getOutput(int entry) {
return value(entry);
}
};
}
/**
* Ensures that this {@code CompactHashMap} has the smallest representation in memory, given its
* current size.
*/
public void trimToSize() {
if (needsAllocArrays()) {
return;
}
Map delegate = delegateOrNull();
if (delegate != null) {
Map newDelegate = createHashFloodingResistantDelegate(size());
newDelegate.putAll(delegate);
this.table = newDelegate;
return;
}
int size = this.size;
if (size < requireEntries().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();
Map 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(requireKeys(), 0, size, null);
Arrays.fill(requireValues(), 0, size, null);
CompactHashing.tableClear(requireTable());
Arrays.fill(requireEntries(), 0, size, 0);
this.size = 0;
}
}
private void writeObject(ObjectOutputStream stream) throws IOException {
stream.defaultWriteObject();
stream.writeInt(size());
Iterator> entryIterator = entrySetIterator();
while (entryIterator.hasNext()) {
Entry 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);
}
}
/*
* The following methods are safe to call as long as both of the following hold:
*
* - allocArrays() has been called. Callers can confirm this by checking needsAllocArrays().
*
* - The map has not switched to delegating to a java.util implementation to mitigate hash
* flooding. Callers can confirm this by null-checking delegateOrNull().
*
* In an ideal world, we would document why we know those things are true every time we call these
* methods. But that is a bit too painful....
*/
private Object requireTable() {
return requireNonNull(table);
}
private int[] requireEntries() {
return requireNonNull(entries);
}
private @Nullable Object[] requireKeys() {
return requireNonNull(keys);
}
private @Nullable Object[] requireValues() {
return requireNonNull(values);
}
/*
* The following methods are safe to call as long as the conditions in the *previous* comment are
* met *and* the index is less than size().
*
* (The above explains when these methods are safe from a `nullness` perspective. From an
* `unchecked` perspective, they're safe because we put only K/V elements into each array.)
*/
@SuppressWarnings("unchecked")
private K key(int i) {
return (K) requireKeys()[i];
}
@SuppressWarnings("unchecked")
private V value(int i) {
return (V) requireValues()[i];
}
private int entry(int i) {
return requireEntries()[i];
}
private void setKey(int i, K key) {
requireKeys()[i] = key;
}
private void setValue(int i, V value) {
requireValues()[i] = value;
}
private void setEntry(int i, int value) {
requireEntries()[i] = value;
}
}