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Coroutines support libraries for Kotlin
/*
* Copyright 2016-2021 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
*/
@file:OptIn(ExperimentalContracts::class)
package kotlinx.coroutines
import kotlinx.coroutines.internal.*
import kotlinx.coroutines.intrinsics.*
import kotlinx.coroutines.selects.*
import kotlin.contracts.*
import kotlin.coroutines.*
import kotlin.coroutines.intrinsics.*
import kotlin.jvm.*
import kotlin.time.*
/**
* Runs a given suspending [block] of code inside a coroutine with a specified [timeout][timeMillis] and throws
* a [TimeoutCancellationException] if the timeout was exceeded.
*
* The code that is executing inside the [block] is cancelled on timeout and the active or next invocation of
* the cancellable suspending function inside the block throws a [TimeoutCancellationException].
*
* The sibling function that does not throw an exception on timeout is [withTimeoutOrNull].
* Note that the timeout action can be specified for a [select] invocation with [onTimeout][SelectBuilder.onTimeout] clause.
*
* **The timeout event is asynchronous with respect to the code running in the block** and may happen at any time,
* even right before the return from inside of the timeout [block]. Keep this in mind if you open or acquire some
* resource inside the [block] that needs closing or release outside of the block.
* See the
* [Asynchronous timeout and resources][https://kotlinlang.org/docs/reference/coroutines/cancellation-and-timeouts.html#asynchronous-timeout-and-resources]
* section of the coroutines guide for details.
*
* > Implementation note: how the time is tracked exactly is an implementation detail of the context's [CoroutineDispatcher].
*
* @param timeMillis timeout time in milliseconds.
*/
public suspend fun withTimeout(timeMillis: Long, block: suspend CoroutineScope.() -> T): T {
contract {
callsInPlace(block, InvocationKind.EXACTLY_ONCE)
}
if (timeMillis <= 0L) throw TimeoutCancellationException("Timed out immediately")
return suspendCoroutineUninterceptedOrReturn { uCont ->
setupTimeout(TimeoutCoroutine(timeMillis, uCont), block)
}
}
/**
* Runs a given suspending [block] of code inside a coroutine with the specified [timeout] and throws
* a [TimeoutCancellationException] if the timeout was exceeded.
*
* The code that is executing inside the [block] is cancelled on timeout and the active or next invocation of
* the cancellable suspending function inside the block throws a [TimeoutCancellationException].
*
* The sibling function that does not throw an exception on timeout is [withTimeoutOrNull].
* Note that the timeout action can be specified for a [select] invocation with [onTimeout][SelectBuilder.onTimeout] clause.
*
* **The timeout event is asynchronous with respect to the code running in the block** and may happen at any time,
* even right before the return from inside of the timeout [block]. Keep this in mind if you open or acquire some
* resource inside the [block] that needs closing or release outside of the block.
* See the
* [Asynchronous timeout and resources][https://kotlinlang.org/docs/reference/coroutines/cancellation-and-timeouts.html#asynchronous-timeout-and-resources]
* section of the coroutines guide for details.
*
* > Implementation note: how the time is tracked exactly is an implementation detail of the context's [CoroutineDispatcher].
*/
@ExperimentalTime
public suspend fun withTimeout(timeout: Duration, block: suspend CoroutineScope.() -> T): T {
contract {
callsInPlace(block, InvocationKind.EXACTLY_ONCE)
}
return withTimeout(timeout.toDelayMillis(), block)
}
/**
* Runs a given suspending block of code inside a coroutine with a specified [timeout][timeMillis] and returns
* `null` if this timeout was exceeded.
*
* The code that is executing inside the [block] is cancelled on timeout and the active or next invocation of
* cancellable suspending function inside the block throws a [TimeoutCancellationException].
*
* The sibling function that throws an exception on timeout is [withTimeout].
* Note that the timeout action can be specified for a [select] invocation with [onTimeout][SelectBuilder.onTimeout] clause.
*
* **The timeout event is asynchronous with respect to the code running in the block** and may happen at any time,
* even right before the return from inside of the timeout [block]. Keep this in mind if you open or acquire some
* resource inside the [block] that needs closing or release outside of the block.
* See the
* [Asynchronous timeout and resources][https://kotlinlang.org/docs/reference/coroutines/cancellation-and-timeouts.html#asynchronous-timeout-and-resources]
* section of the coroutines guide for details.
*
* > Implementation note: how the time is tracked exactly is an implementation detail of the context's [CoroutineDispatcher].
*
* @param timeMillis timeout time in milliseconds.
*/
public suspend fun withTimeoutOrNull(timeMillis: Long, block: suspend CoroutineScope.() -> T): T? {
if (timeMillis <= 0L) return null
var coroutine: TimeoutCoroutine? = null
try {
return suspendCoroutineUninterceptedOrReturn { uCont ->
val timeoutCoroutine = TimeoutCoroutine(timeMillis, uCont)
coroutine = timeoutCoroutine
setupTimeout(timeoutCoroutine, block)
}
} catch (e: TimeoutCancellationException) {
// Return null if it's our exception, otherwise propagate it upstream (e.g. in case of nested withTimeouts)
if (e.coroutine.unweakRef() === coroutine) {
return null
}
throw e
}
}
/**
* Runs a given suspending block of code inside a coroutine with the specified [timeout] and returns
* `null` if this timeout was exceeded.
*
* The code that is executing inside the [block] is cancelled on timeout and the active or next invocation of
* cancellable suspending function inside the block throws a [TimeoutCancellationException].
*
* The sibling function that throws an exception on timeout is [withTimeout].
* Note that the timeout action can be specified for a [select] invocation with [onTimeout][SelectBuilder.onTimeout] clause.
*
* **The timeout event is asynchronous with respect to the code running in the block** and may happen at any time,
* even right before the return from inside of the timeout [block]. Keep this in mind if you open or acquire some
* resource inside the [block] that needs closing or release outside of the block.
* See the
* [Asynchronous timeout and resources][https://kotlinlang.org/docs/reference/coroutines/cancellation-and-timeouts.html#asynchronous-timeout-and-resources]
* section of the coroutines guide for details.
*
* > Implementation note: how the time is tracked exactly is an implementation detail of the context's [CoroutineDispatcher].
*/
@ExperimentalTime
public suspend fun withTimeoutOrNull(timeout: Duration, block: suspend CoroutineScope.() -> T): T? =
withTimeoutOrNull(timeout.toDelayMillis(), block)
private fun setupTimeout(
coroutine: TimeoutCoroutine,
block: suspend CoroutineScope.() -> T
): Any? {
// schedule cancellation of this coroutine on time
val cont = coroutine.uCont
val context = cont.context
coroutine.disposeOnCompletion(context.delay.invokeOnTimeout(coroutine.time, coroutine, coroutine.context))
// restart the block using a new coroutine with a new job,
// however, start it undispatched, because we already are in the proper context
return coroutine.startUndispatchedOrReturnIgnoreTimeout(coroutine, block)
}
private class TimeoutCoroutine(
@JvmField val time: Long,
uCont: Continuation // unintercepted continuation
) : ScopeCoroutine(uCont.context, uCont, false), Runnable {
init {
// Kludge for native
if (!isReuseSupportedInPlatform()) initParentForNativeUndispatchedCoroutine()
}
override fun run() {
cancelCoroutine(TimeoutCancellationException(time, this))
}
override fun nameString(): String =
"${super.nameString()}(timeMillis=$time)"
}
/**
* This exception is thrown by [withTimeout] to indicate timeout.
*/
public class TimeoutCancellationException internal constructor(
message: String,
@JvmField internal val coroutine: Any?
) : CancellationException(message), CopyableThrowable {
/**
* Creates a timeout exception with the given message.
* This constructor is needed for exception stack-traces recovery.
*/
@Suppress("UNUSED")
internal constructor(message: String) : this(message, null)
// message is never null in fact
override fun createCopy(): TimeoutCancellationException? =
TimeoutCancellationException(message ?: "", coroutine).also { it.initCause(this) }
}
@Suppress("FunctionName")
internal fun TimeoutCancellationException(
time: Long,
coroutine: Job
) : TimeoutCancellationException = TimeoutCancellationException("Timed out waiting for $time ms", coroutine.weakRef())