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/**
 * Copyright (C) 2008 Google Inc.
 *
 * 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.inject.internal;

import com.google.inject.Key;
import com.google.inject.internal.util.Maps;
import com.google.inject.internal.util.Sets;
import com.google.inject.internal.util.SourceProvider;

import java.util.Map;
import java.util.Set;

/**
 * Minimal set that doesn't hold strong references to the contained keys.
 *
 * @author [email protected] (Jesse Wilson)
 */
final class WeakKeySet {

  /**
   * We store strings rather than keys so we don't hold strong references.
   *
   * 

One potential problem with this approach is that parent and child injectors cannot define * keys whose class names are equal but class loaders are different. This shouldn't be an issue * in practice. */ private Map> backingSet; public void add(Key key, Object source) { if (backingSet == null) { backingSet = Maps.newHashMap(); } // if it's an instanceof Class, it was a JIT binding, which we don't // want to retain. if (source instanceof Class || source == SourceProvider.UNKNOWN_SOURCE) { source = null; } String k = key.toString(); Set sources = backingSet.get(k); if (sources == null) { sources = Sets.newLinkedHashSet(); backingSet.put(k, sources); } sources.add(Errors.convert(source)); } public boolean contains(Key key) { // avoid calling key.toString() if the backing set is empty. toString is expensive in aggregate, // and most WeakKeySets are empty in practice (because they're used by top-level injectors) return backingSet != null && backingSet.containsKey(key.toString()); } public Set getSources(Key key) { return backingSet.get(key.toString()); } }