mirai/mirai-core-utils/src/commonMain/kotlin/WeakRef.kt
Him188 cda6aaa79b Simplify cache configuration.
Improve cache saving:
- Use ProtoBuf to serialize BdhSession
- More readable servers.json
2021-02-10 15:20:39 +08:00

97 lines
2.9 KiB
Kotlin

/*
* Copyright 2019-2021 Mamoe Technologies and contributors.
*
* 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
* Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
*
* https://github.com/mamoe/mirai/blob/master/LICENSE
*/
@file:JvmMultifileClass
@file:JvmName("MiraiUtils")
@file:Suppress("unused", "NOTHING_TO_INLINE")
package net.mamoe.mirai.utils
import kotlin.reflect.KProperty
/**
* WeakRef that `getValue` for delegation throws an [IllegalStateException] if the referent is released by GC. Therefore it returns notnull value only
*/
public class UnsafeWeakRef<T>(private val weakRef: WeakRef<T>) {
public fun get(): T = weakRef.get() ?: error("WeakRef is released")
public fun clear(): Unit = weakRef.clear()
}
/**
* Provides delegate value.
*
* ```kotlin
* val bot: Bot by param.unsafeWeakRef()
* ```
*/
@JvmSynthetic
public inline operator fun <T> UnsafeWeakRef<T>.getValue(thisRef: Any?, property: KProperty<*>): T = get()
/**
* Weak Reference.
* On JVM, it is implemented as a typealias referring to `WeakReference` from JDK.
*
* Details:
* On JVM, instances of objects are stored in the JVM Heap and are accessed via references.
* GC(garbage collection) can automatically collect and release the memory used by objects that are not directly referred by any other.
* [WeakRef] is not a direct reference, therefore it doesn't hinder GC.
*
* @see weakRef provides a WeakRef
* @see unsafeWeakRef provides a UnsafeWeakRef
*/
public typealias WeakRef<T> = java.lang.ref.WeakReference<T>
/**
* Indicates that the property is delegated by a [WeakRef]
*
* @see weakRef
*/
@Target(AnnotationTarget.PROPERTY)
@Retention(AnnotationRetention.SOURCE)
public annotation class WeakRefProperty
/**
* Provides a weak reference to [this]
* The `getValue` for delegation returns [this] when [this] is not released by GC
*/
@JvmSynthetic
public inline fun <T> T.weakRef(): WeakRef<T> = WeakRef(this)
/**
* Constructs an unsafe inline delegate for [this]
*/
@JvmSynthetic
public inline fun <T> WeakRef<T>.unsafe(): UnsafeWeakRef<T> = UnsafeWeakRef(this)
/**
* Provides a weak reference to [this].
* The `getValue` for delegation throws an [IllegalStateException] if the referent is released by GC. Therefore it returns notnull value only
*
* **UNSTABLE API**: It is strongly suggested not to use this api
*/
@JvmSynthetic
public inline fun <T> T.unsafeWeakRef(): UnsafeWeakRef<T> = UnsafeWeakRef(this.weakRef())
/**
* Provides delegate value.
*
* ```kotlin
* val bot: Bot? by param.weakRef()
* ```
*/
@JvmSynthetic
public inline operator fun <T> WeakRef<T>.getValue(thisRef: Any?, property: KProperty<*>): T? = this.get()
/**
* Call the block if the referent is absent
*/
@JvmSynthetic
public inline fun <T, R> WeakRef<T>.ifAbsent(block: (T) -> R): R? = this.get()?.let(block)