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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 com.google.common.annotations.GwtCompatible;
import com.google.common.primitives.Ints;
import com.google.errorprone.annotations.concurrent.LazyInit;
import java.util.Collection;
import java.util.Map;
import javax.annotation.CheckForNull;
/**
* An implementation of ImmutableMultiset backed by a JDK Map and a list of entries. Used to protect
* against hash flooding attacks.
*
* @author Louis Wasserman
*/
@GwtCompatible
@ElementTypesAreNonnullByDefault
final class JdkBackedImmutableMultiset<E> extends ImmutableMultiset<E> {
private final Map<E, Integer> delegateMap;
private final ImmutableList<Entry<E>> entries;
private final long size;
static <E> ImmutableMultiset<E> create(Collection<? extends Entry<? extends E>> entries) {
@SuppressWarnings("unchecked")
Entry<E>[] entriesArray = entries.toArray(new Entry[0]);
Map<E, Integer> delegateMap = Maps.newHashMapWithExpectedSize(entriesArray.length);
long size = 0;
for (int i = 0; i < entriesArray.length; i++) {
Entry<E> entry = entriesArray[i];
int count = entry.getCount();
size += count;
E element = checkNotNull(entry.getElement());
delegateMap.put(element, count);
if (!(entry instanceof Multisets.ImmutableEntry)) {
entriesArray[i] = Multisets.immutableEntry(element, count);
}
}
return new JdkBackedImmutableMultiset<>(
delegateMap, ImmutableList.asImmutableList(entriesArray), size);
}
private JdkBackedImmutableMultiset(
Map<E, Integer> delegateMap, ImmutableList<Entry<E>> entries, long size) {
this.delegateMap = delegateMap;
this.entries = entries;
this.size = size;
}
@Override
public int count(@CheckForNull Object element) {
return delegateMap.getOrDefault(element, 0);
}
@LazyInit @CheckForNull private transient ImmutableSet<E> elementSet;
@Override
public ImmutableSet<E> elementSet() {
ImmutableSet<E> result = elementSet;
return (result == null) ? elementSet = new ElementSet<>(entries, this) : result;
}
@Override
Entry<E> getEntry(int index) {
return entries.get(index);
}
@Override
boolean isPartialView() {
return false;
}
@Override
public int size() {
return Ints.saturatedCast(size);
}
}
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