com.google.common.collect.RegularImmutableMap Maven / Gradle / Ivy
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This artifact provides a single jar that contains all classes required to use remote EJB and JMS, including
all dependencies. It is intended for use by those not using maven, maven users should just import the EJB and
JMS BOM's instead (shaded JAR's cause lots of problems with maven, as it is very easy to inadvertently end up
with different versions on classes on the class path).
/*
* Copyright (C) 2008 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.base.Preconditions.checkPositionIndex;
import static com.google.common.collect.CollectPreconditions.checkEntryNotNull;
import static com.google.common.collect.ImmutableMapEntry.createEntryArray;
import static java.util.Objects.requireNonNull;
import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.collect.ImmutableMapEntry.NonTerminalImmutableMapEntry;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.io.Serializable;
import java.util.IdentityHashMap;
import java.util.function.BiConsumer;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;
/**
* Implementation of {@link ImmutableMap} with two or more entries.
*
* @author Jesse Wilson
* @author Kevin Bourrillion
* @author Gregory Kick
*/
@GwtCompatible(serializable = true, emulated = true)
@ElementTypesAreNonnullByDefault
final class RegularImmutableMap extends ImmutableMap {
@SuppressWarnings("unchecked")
static final ImmutableMap EMPTY =
new RegularImmutableMap<>((Entry[]) ImmutableMap.EMPTY_ENTRY_ARRAY, null, 0);
/**
* Closed addressing tends to perform well even with high load factors. Being conservative here
* ensures that the table is still likely to be relatively sparse (hence it misses fast) while
* saving space.
*/
@VisibleForTesting static final double MAX_LOAD_FACTOR = 1.2;
/**
* 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.HashMap based
* implementation. Experimentally determined.
*/
@VisibleForTesting static final int MAX_HASH_BUCKET_LENGTH = 8;
// entries in insertion order
@VisibleForTesting final transient Entry[] entries;
// array of linked lists of entries
@CheckForNull private final transient @Nullable ImmutableMapEntry[] table;
// 'and' with an int to get a table index
private final transient int mask;
static ImmutableMap fromEntries(Entry... entries) {
return fromEntryArray(entries.length, entries, /* throwIfDuplicateKeys= */ true);
}
/**
* Creates an ImmutableMap from the first n entries in entryArray. This implementation may replace
* the entries in entryArray with its own entry objects (though they will have the same key/value
* contents), and may take ownership of entryArray.
*/
static ImmutableMap fromEntryArray(
int n, @Nullable Entry[] entryArray, boolean throwIfDuplicateKeys) {
checkPositionIndex(n, entryArray.length);
if (n == 0) {
@SuppressWarnings("unchecked") // it has no entries so the type variables don't matter
ImmutableMap empty = (ImmutableMap) EMPTY;
return empty;
}
try {
return fromEntryArrayCheckingBucketOverflow(n, entryArray, throwIfDuplicateKeys);
} catch (BucketOverflowException e) {
// probable hash flooding attack, fall back to j.u.HM based implementation and use its
// implementation of hash flooding protection
return JdkBackedImmutableMap.create(n, entryArray, throwIfDuplicateKeys);
}
}
private static ImmutableMap fromEntryArrayCheckingBucketOverflow(
int n, @Nullable Entry[] entryArray, boolean throwIfDuplicateKeys)
throws BucketOverflowException {
/*
* The cast is safe: n==entryArray.length means that we have filled the whole array with Entry
* instances, in which case it is safe to cast it from an array of nullable entries to an array
* of non-null entries.
*/
@SuppressWarnings("nullness")
Entry[] entries =
(n == entryArray.length) ? (Entry[]) entryArray : createEntryArray(n);
int tableSize = Hashing.closedTableSize(n, MAX_LOAD_FACTOR);
@Nullable ImmutableMapEntry[] table = createEntryArray(tableSize);
int mask = tableSize - 1;
// If duplicates are allowed, this IdentityHashMap will record the final Entry for each
// duplicated key. We will use this final Entry to overwrite earlier slots in the entries array
// that have the same key. Then a second pass will remove all but the first of the slots that
// have this Entry. The value in the map becomes false when this first entry has been copied, so
// we know not to copy the remaining ones.
IdentityHashMap, Boolean> duplicates = null;
int dupCount = 0;
for (int entryIndex = n - 1; entryIndex >= 0; entryIndex--) {
// requireNonNull is safe because the first `n` elements have been filled in.
Entry entry = requireNonNull(entryArray[entryIndex]);
K key = entry.getKey();
V value = entry.getValue();
checkEntryNotNull(key, value);
int tableIndex = Hashing.smear(key.hashCode()) & mask;
ImmutableMapEntry keyBucketHead = table[tableIndex];
ImmutableMapEntry effectiveEntry =
checkNoConflictInKeyBucket(key, value, keyBucketHead, throwIfDuplicateKeys);
if (effectiveEntry == null) {
// prepend, not append, so the entries can be immutable
effectiveEntry =
(keyBucketHead == null)
? makeImmutable(entry, key, value)
: new NonTerminalImmutableMapEntry(key, value, keyBucketHead);
table[tableIndex] = effectiveEntry;
} else {
// We already saw this key, and the first value we saw (going backwards) is the one we are
// keeping. So we won't touch table[], but we do still want to add the existing entry that
// we found to entries[] so that we will see this key in the right place when iterating.
if (duplicates == null) {
duplicates = new IdentityHashMap<>();
}
duplicates.put(effectiveEntry, true);
dupCount++;
// Make sure we are not overwriting the original entries array, in case we later do
// buildOrThrow(). We would want an exception to include two values for the duplicate key.
if (entries == entryArray) {
entries = entries.clone();
}
}
entries[entryIndex] = effectiveEntry;
}
if (duplicates != null) {
// Explicit type parameters needed here to avoid a problem with nullness inference.
entries = RegularImmutableMap.removeDuplicates(entries, n, n - dupCount, duplicates);
int newTableSize = Hashing.closedTableSize(entries.length, MAX_LOAD_FACTOR);
if (newTableSize != tableSize) {
return fromEntryArrayCheckingBucketOverflow(
entries.length, entries, /* throwIfDuplicateKeys= */ true);
}
}
return new RegularImmutableMap<>(entries, table, mask);
}
/**
* Constructs a new entry array where each duplicated key from the original appears only once, at
* its first position but with its final value. The {@code duplicates} map is modified.
*
* @param entries the original array of entries including duplicates
* @param n the number of valid entries in {@code entries}
* @param newN the expected number of entries once duplicates are removed
* @param duplicates a map of canonical {@link Entry} objects for each duplicate key. This map
* will be updated by the method, setting each value to false as soon as the {@link Entry} has
* been included in the new entry array.
* @return an array of {@code newN} entries where no key appears more than once.
*/
static Entry[] removeDuplicates(
Entry[] entries, int n, int newN, IdentityHashMap, Boolean> duplicates) {
Entry[] newEntries = createEntryArray(newN);
for (int in = 0, out = 0; in < n; in++) {
Entry entry = entries[in];
Boolean status = duplicates.get(entry);
// null=>not dup'd; true=>dup'd, first; false=>dup'd, not first
if (status != null) {
if (status) {
duplicates.put(entry, false);
} else {
continue; // delete this entry; we already copied an earlier one for the same key
}
}
newEntries[out++] = entry;
}
return newEntries;
}
/** Makes an entry usable internally by a new ImmutableMap without rereading its contents. */
static ImmutableMapEntry makeImmutable(Entry entry, K key, V value) {
boolean reusable =
entry instanceof ImmutableMapEntry && ((ImmutableMapEntry) entry).isReusable();
return reusable ? (ImmutableMapEntry) entry : new ImmutableMapEntry(key, value);
}
/** Makes an entry usable internally by a new ImmutableMap. */
static ImmutableMapEntry makeImmutable(Entry entry) {
return makeImmutable(entry, entry.getKey(), entry.getValue());
}
private RegularImmutableMap(
Entry[] entries, @CheckForNull @Nullable ImmutableMapEntry[] table, int mask) {
this.entries = entries;
this.table = table;
this.mask = mask;
}
/**
* Checks if the given key already appears in the hash chain starting at {@code keyBucketHead}. If
* it does not, then null is returned. If it does, then if {@code throwIfDuplicateKeys} is true an
* {@code IllegalArgumentException} is thrown, and otherwise the existing {@link Entry} is
* returned.
*
* @throws IllegalArgumentException if another entry in the bucket has the same key and {@code
* throwIfDuplicateKeys} is true
* @throws BucketOverflowException if this bucket has too many entries, which may indicate a hash
* flooding attack
*/
@CanIgnoreReturnValue
static @Nullable ImmutableMapEntry checkNoConflictInKeyBucket(
Object key,
Object newValue,
@CheckForNull ImmutableMapEntry keyBucketHead,
boolean throwIfDuplicateKeys)
throws BucketOverflowException {
int bucketSize = 0;
for (; keyBucketHead != null; keyBucketHead = keyBucketHead.getNextInKeyBucket()) {
if (keyBucketHead.getKey().equals(key)) {
if (throwIfDuplicateKeys) {
checkNoConflict(/* safe= */ false, "key", keyBucketHead, key + "=" + newValue);
} else {
return keyBucketHead;
}
}
if (++bucketSize > MAX_HASH_BUCKET_LENGTH) {
throw new BucketOverflowException();
}
}
return null;
}
static class BucketOverflowException extends Exception {}
@Override
@CheckForNull
public V get(@CheckForNull Object key) {
return get(key, table, mask);
}
@CheckForNull
static V get(
@CheckForNull Object key,
@CheckForNull @Nullable ImmutableMapEntry[] keyTable,
int mask) {
if (key == null || keyTable == null) {
return null;
}
int index = Hashing.smear(key.hashCode()) & mask;
for (ImmutableMapEntry entry = keyTable[index];
entry != null;
entry = entry.getNextInKeyBucket()) {
Object candidateKey = entry.getKey();
/*
* Assume that equals uses the == optimization when appropriate, and that
* it would check hash codes as an optimization when appropriate. If we
* did these things, it would just make things worse for the most
* performance-conscious users.
*/
if (key.equals(candidateKey)) {
return entry.getValue();
}
}
return null;
}
@Override
public void forEach(BiConsumer action) {
checkNotNull(action);
for (Entry entry : entries) {
action.accept(entry.getKey(), entry.getValue());
}
}
@Override
public int size() {
return entries.length;
}
@Override
boolean isPartialView() {
return false;
}
@Override
ImmutableSet> createEntrySet() {
return new ImmutableMapEntrySet.RegularEntrySet<>(this, entries);
}
@Override
ImmutableSet createKeySet() {
return new KeySet<>(this);
}
@GwtCompatible(emulated = true)
private static final class KeySet extends IndexedImmutableSet {
private final RegularImmutableMap map;
KeySet(RegularImmutableMap map) {
this.map = map;
}
@Override
K get(int index) {
return map.entries[index].getKey();
}
@Override
public boolean contains(@CheckForNull Object object) {
return map.containsKey(object);
}
@Override
boolean isPartialView() {
return true;
}
@Override
public int size() {
return map.size();
}
// No longer used for new writes, but kept so that old data can still be read.
@GwtIncompatible // serialization
@SuppressWarnings("unused")
private static class SerializedForm implements Serializable {
final ImmutableMap map;
SerializedForm(ImmutableMap map) {
this.map = map;
}
Object readResolve() {
return map.keySet();
}
private static final long serialVersionUID = 0;
}
}
@Override
ImmutableCollection createValues() {
return new Values<>(this);
}
@GwtCompatible(emulated = true)
private static final class Values extends ImmutableList {
final RegularImmutableMap map;
Values(RegularImmutableMap map) {
this.map = map;
}
@Override
public V get(int index) {
return map.entries[index].getValue();
}
@Override
public int size() {
return map.size();
}
@Override
boolean isPartialView() {
return true;
}
// No longer used for new writes, but kept so that old data can still be read.
@GwtIncompatible // serialization
@SuppressWarnings("unused")
private static class SerializedForm implements Serializable {
final ImmutableMap map;
SerializedForm(ImmutableMap map) {
this.map = map;
}
Object readResolve() {
return map.values();
}
private static final long serialVersionUID = 0;
}
}
// This class is never actually serialized directly, but we have to make the
// warning go away (and suppressing would suppress for all nested classes too)
private static final long serialVersionUID = 0;
}