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@@ -0,0 +1,45 @@
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+@file:Suppress("unused", "FunctionName")
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+
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+package net.mamoe.mirai.utils
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+
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+import kotlinx.coroutines.CompletableDeferred
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+import kotlinx.coroutines.CoroutineScope
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+import kotlinx.coroutines.Deferred
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+import kotlinx.coroutines.async
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+import net.mamoe.mirai.contact.QQ
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+
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+/**
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+ * 创建一个在当前 [CoroutineScope] 下执行的 [SuspendLazy]
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+ */
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+fun <R> CoroutineScope.SuspendLazy(initializer: suspend () -> R): SuspendLazy<R> = SuspendLazy(this, initializer)
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+
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+/**
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+ * 挂起初始化的 [lazy], 是属性不能 `suspend` 的替代品.
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+ *
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+ * 本对象代表值初始化时将会通过 [CoroutineScope.async] 运行 [initializer]
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+ *
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+ * [SuspendLazy] 是:
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+ * - 线程安全
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+ * - 只会被初始化一次.
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+ * - `SuspendLazy<R>.value` 返回 `Deferred<R>`
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+ * - 可以用作属性代表 (`val profile: by SuspendLazy(GlobalScope) { calculateValue() }`)
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+ *
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+ * @sample QQ.profile
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+ */
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+class SuspendLazy<R>(scope: CoroutineScope, val initializer: suspend () -> R) : Lazy<Deferred<R>> {
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+ private val valueUpdater: Deferred<R> by lazy { scope.async { initializer() } }
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+
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+ @Suppress("EXPERIMENTAL_API_USAGE")
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+ override val value: Deferred<R>
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+ get() = if (isInitialized()) {
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+ CompletableDeferred(valueUpdater.getCompleted())
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+ } else {
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+ CompletableDeferred<R>().apply {
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+ valueUpdater.invokeOnCompletion {
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+ this.complete(valueUpdater.getCompleted())
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+ }
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+ }
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+ }
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+
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+ override fun isInitialized(): Boolean = valueUpdater.isCompleted
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+}
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Him188