1 /*
2  * Copyright (C) 2024 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
18 
19 /**
20  * A collection of listeners, observers, callbacks, etc.
21  *
22  * This container is optimized for frequent mutation and infrequent iteration, with reentrant-safety
23  * guarantees but without thread-safety guarantees. Specifically, to ensure that
24  * [ConcurrentModificationException] is not thrown when listeners mutate the set, this iterator will
25  * not reflect changes made to the set after the iterator is constructed.
26  */
27 class CopyOnLoopListenerSet<E : Any>
28 /** Private constructor takes the internal list so that we can use auto-delegation */
29 private constructor(private val listeners: ArrayList<E>) :
30     Collection<E> by listeners, IListenerSet<E> {
31 
32     /** Create a new instance */
33     constructor() : this(ArrayList())
34 
35     @Suppress("UNCHECKED_CAST")
iteratornull36     override fun iterator(): Iterator<E> = listeners.toArray().iterator() as Iterator<E>
37 
38     override fun addIfAbsent(element: E): Boolean =
39         if (element in listeners) {
40             false
41         } else {
42             listeners.add(element)
43         }
44 
removenull45     override fun remove(element: E): Boolean = listeners.remove(element)
46 }
47