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/*
* Copyright (C) 2018 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.RegularImmutableMap.makeImmutable;
import static java.util.Objects.requireNonNull;
import com.google.common.annotations.GwtCompatible;
import java.util.HashMap;
import java.util.Map;
import java.util.function.BiConsumer;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;
/**
* Implementation of ImmutableMap backed by a JDK HashMap, which has smartness protecting against
* hash flooding.
*/
@GwtCompatible(emulated = true)
@ElementTypesAreNonnullByDefault
final class JdkBackedImmutableMap<K, V> extends ImmutableMap<K, V> {
/**
* Creates an {@code ImmutableMap} backed by a JDK HashMap. Used when probable hash flooding is
* detected. This implementation may replace the entries in entryArray with its own entry objects
* (though they will have the same key/value contents), and will take ownership of entryArray.
*/
static <K, V> ImmutableMap<K, V> create(
int n, @Nullable Entry<K, V>[] entryArray, boolean throwIfDuplicateKeys) {
Map<K, V> delegateMap = Maps.newHashMapWithExpectedSize(n);
// If duplicates are allowed, this map will track the last value for each duplicated key.
// A second pass will retain only the first entry for that key, but with this last value. The
// value will then be replaced by null, signaling that later entries with the same key should
// be deleted.
Map<K, @Nullable V> duplicates = null;
int dupCount = 0;
for (int i = 0; i < n; i++) {
// requireNonNull is safe because the first `n` elements have been filled in.
entryArray[i] = makeImmutable(requireNonNull(entryArray[i]));
K key = entryArray[i].getKey();
V value = entryArray[i].getValue();
V oldValue = delegateMap.put(key, value);
if (oldValue != null) {
if (throwIfDuplicateKeys) {
throw conflictException("key", entryArray[i], entryArray[i].getKey() + "=" + oldValue);
}
if (duplicates == null) {
duplicates = new HashMap<>();
}
duplicates.put(key, value);
dupCount++;
}
}
if (duplicates != null) {
@SuppressWarnings({"rawtypes", "unchecked"})
Entry<K, V>[] newEntryArray = new Entry[n - dupCount];
for (int inI = 0, outI = 0; inI < n; inI++) {
Entry<K, V> entry = requireNonNull(entryArray[inI]);
K key = entry.getKey();
if (duplicates.containsKey(key)) {
V value = duplicates.get(key);
if (value == null) {
continue; // delete this duplicate
}
entry = new ImmutableMapEntry<>(key, value);
duplicates.put(key, null);
}
newEntryArray[outI++] = entry;
}
entryArray = newEntryArray;
}
return new JdkBackedImmutableMap<>(delegateMap, ImmutableList.asImmutableList(entryArray, n));
}
private final transient Map<K, V> delegateMap;
private final transient ImmutableList<Entry<K, V>> entries;
JdkBackedImmutableMap(Map<K, V> delegateMap, ImmutableList<Entry<K, V>> entries) {
this.delegateMap = delegateMap;
this.entries = entries;
}
@Override
public int size() {
return entries.size();
}
@Override
@CheckForNull
public V get(@CheckForNull Object key) {
return delegateMap.get(key);
}
@Override
ImmutableSet<Entry<K, V>> createEntrySet() {
return new ImmutableMapEntrySet.RegularEntrySet<>(this, entries);
}
@Override
public void forEach(BiConsumer<? super K, ? super V> action) {
checkNotNull(action);
entries.forEach(e -> action.accept(e.getKey(), e.getValue()));
}
@Override
ImmutableSet<K> createKeySet() {
return new ImmutableMapKeySet<>(this);
}
@Override
ImmutableCollection<V> createValues() {
return new ImmutableMapValues<>(this);
}
@Override
boolean isPartialView() {
return false;
}
}
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