1 /*
2  * Copyright (C) 2017 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 package com.android.systemui.util.leak;
18 
19 import java.lang.ref.Reference;
20 import java.lang.ref.ReferenceQueue;
21 import java.lang.ref.WeakReference;
22 import java.util.Collection;
23 import java.util.HashMap;
24 import java.util.Map;
25 import java.util.Set;
26 
27 /**
28  * Like WeakHashMap, but uses identity instead of equality when comparing keys.
29  */
30 public class WeakIdentityHashMap<K,V> {
31 
32     private final HashMap<WeakReference<K>,V> mMap = new HashMap<>();
33     private final ReferenceQueue<Object> mRefQueue = new ReferenceQueue<>();
34 
cleanUp()35     private void cleanUp() {
36         Reference<?> ref;
37         while ((ref = mRefQueue.poll()) != null) {
38             mMap.remove(ref);
39         }
40     }
41 
put(K key, V value)42     public void put(K key, V value) {
43         cleanUp();
44         mMap.put(new CmpWeakReference<>(key, mRefQueue), value);
45     }
46 
get(K key)47     public V get(K key) {
48         cleanUp();
49         return mMap.get(new CmpWeakReference<>(key));
50     }
51 
values()52     public Collection<V> values() {
53         cleanUp();
54         return mMap.values();
55     }
56 
entrySet()57     public Set<Map.Entry<WeakReference<K>, V>> entrySet() {
58         return mMap.entrySet();
59     }
60 
size()61     public int size() {
62         cleanUp();
63         return mMap.size();
64     }
65 
isEmpty()66     public boolean isEmpty() {
67         cleanUp();
68         return mMap.isEmpty();
69     }
70 
71     private static class CmpWeakReference<K> extends WeakReference<K> {
72         private final int mHashCode;
73 
CmpWeakReference(K key)74         public CmpWeakReference(K key) {
75             super(key);
76             mHashCode = System.identityHashCode(key);
77         }
78 
CmpWeakReference(K key, ReferenceQueue<Object> refQueue)79         public CmpWeakReference(K key, ReferenceQueue<Object> refQueue) {
80             super(key, refQueue);
81             mHashCode = System.identityHashCode(key);
82         }
83 
84         @Override
equals(Object o)85         public boolean equals(Object o) {
86             if (o == this) {
87                 return true;
88             }
89             K k = get();
90             if (k != null && o instanceof CmpWeakReference) {
91                 return ((CmpWeakReference) o).get() == k;
92             }
93             return false;
94         }
95 
96         @Override
hashCode()97         public int hashCode() {
98             return mHashCode;
99         }
100     }
101 }
102