| /* |
| * Copyright 2021 The Android Open Source Project |
| * |
| * 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 androidx.compose.ui.platform |
| |
| import androidx.compose.runtime.collection.mutableVectorOf |
| import java.lang.ref.Reference |
| import java.lang.ref.ReferenceQueue |
| import java.lang.ref.WeakReference |
| |
| /** |
| * A simple collection that keeps values as [WeakReference]s. |
| * Elements are added with [push] and removed with [pop]. |
| */ |
| internal class WeakCache<T> { |
| private val values = mutableVectorOf<Reference<T>>() |
| private val referenceQueue = ReferenceQueue<T>() |
| |
| /** |
| * Add [element] to the collection as a [WeakReference]. It will be removed when |
| * garbage collected or from [pop]. |
| */ |
| fun push(element: T) { |
| clearWeakReferences() |
| values += WeakReference(element, referenceQueue) |
| } |
| |
| /** |
| * Remove an element from the collection and return it. If no element is |
| * available, `null` is returned. |
| */ |
| fun pop(): T? { |
| clearWeakReferences() |
| |
| while (values.isNotEmpty()) { |
| val item = values.removeAt(values.lastIndex).get() |
| if (item != null) { |
| return item |
| } |
| } |
| return null |
| } |
| |
| /** |
| * The number of elements currently in the collection. This may change between |
| * calls if the references have been garbage collected. |
| */ |
| val size: Int |
| get() { |
| clearWeakReferences() |
| return values.size |
| } |
| |
| private fun clearWeakReferences() { |
| do { |
| val item: Reference<out T>? = referenceQueue.poll() |
| if (item != null) { |
| @Suppress("UNCHECKED_CAST") |
| values.remove(item as Reference<T>) |
| } |
| } while (item != null) |
| } |
| } |