1 /* 2 * Copyright 2016-2020 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license. 3 */ 4 5 package kotlinx.coroutines 6 7 import kotlin.coroutines.* 8 import kotlin.jvm.* 9 10 /** 11 * A coroutine dispatcher that is not confined to any specific thread. 12 */ 13 internal object Unconfined : CoroutineDispatcher() { isDispatchNeedednull14 override fun isDispatchNeeded(context: CoroutineContext): Boolean = false 15 16 override fun dispatch(context: CoroutineContext, block: Runnable) { 17 // It can only be called by the "yield" function. See also code of "yield" function. 18 val yieldContext = context[YieldContext] 19 if (yieldContext != null) { 20 // report to "yield" that it is an unconfined dispatcher and don't call "block.run()" 21 yieldContext.dispatcherWasUnconfined = true 22 return 23 } 24 throw UnsupportedOperationException("Dispatchers.Unconfined.dispatch function can only be used by the yield function. " + 25 "If you wrap Unconfined dispatcher in your code, make sure you properly delegate " + 26 "isDispatchNeeded and dispatch calls.") 27 } 28 toStringnull29 override fun toString(): String = "Dispatchers.Unconfined" 30 } 31 32 /** 33 * Used to detect calls to [Unconfined.dispatch] from [yield] function. 34 */ 35 internal class YieldContext : AbstractCoroutineContextElement(Key) { 36 companion object Key : CoroutineContext.Key<YieldContext> 37 38 @JvmField 39 var dispatcherWasUnconfined = false 40 } 41