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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Threading.Tasks;
namespace System.Runtime.CompilerServices
{
/// <summary>Provides an awaitable type that enables configured awaits on a <see cref="ValueTask{TResult}"/>.</summary>
/// <typeparam name="TResult">The type of the result produced.</typeparam>
[StructLayout(LayoutKind.Auto)]
public readonly struct ConfiguredValueTaskAwaitable<TResult>
{
/// <summary>The wrapped <see cref="ValueTask{TResult}"/>.</summary>
private readonly ValueTask<TResult> _value;
/// <summary>true to attempt to marshal the continuation back to the original context captured; otherwise, false.</summary>
private readonly bool _continueOnCapturedContext;
/// <summary>Initializes the awaitable.</summary>
/// <param name="value">The wrapped <see cref="ValueTask{TResult}"/>.</param>
/// <param name="continueOnCapturedContext">
/// true to attempt to marshal the continuation back to the original synchronization context captured; otherwise, false.
/// </param>
internal ConfiguredValueTaskAwaitable(ValueTask<TResult> value, bool continueOnCapturedContext)
{
_value = value;
_continueOnCapturedContext = continueOnCapturedContext;
}
/// <summary>Returns an awaiter for this <see cref="ConfiguredValueTaskAwaitable{TResult}"/> instance.</summary>
public ConfiguredValueTaskAwaiter GetAwaiter() =>
new ConfiguredValueTaskAwaiter(_value, _continueOnCapturedContext);
/// <summary>Provides an awaiter for a <see cref="ConfiguredValueTaskAwaitable{TResult}"/>.</summary>
[StructLayout(LayoutKind.Auto)]
public readonly struct ConfiguredValueTaskAwaiter : ICriticalNotifyCompletion, IConfiguredValueTaskAwaiter
{
/// <summary>The value being awaited.</summary>
private readonly ValueTask<TResult> _value;
/// <summary>The value to pass to ConfigureAwait.</summary>
internal readonly bool _continueOnCapturedContext;
/// <summary>Initializes the awaiter.</summary>
/// <param name="value">The value to be awaited.</param>
/// <param name="continueOnCapturedContext">The value to pass to ConfigureAwait.</param>
internal ConfiguredValueTaskAwaiter(ValueTask<TResult> value, bool continueOnCapturedContext)
{
_value = value;
_continueOnCapturedContext = continueOnCapturedContext;
}
/// <summary>Gets whether the <see cref="ConfiguredValueTaskAwaitable{TResult}"/> has completed.</summary>
public bool IsCompleted => _value.IsCompleted;
/// <summary>Gets the result of the ValueTask.</summary>
[StackTraceHidden]
public TResult GetResult() =>
_value._task == null ?
_value._result :
_value._task.GetAwaiter().GetResult();
/// <summary>Schedules the continuation action for the <see cref="ConfiguredValueTaskAwaitable{TResult}"/>.</summary>
public void OnCompleted(Action continuation) =>
_value.AsTask().ConfigureAwait(_continueOnCapturedContext).GetAwaiter().OnCompleted(continuation);
/// <summary>Schedules the continuation action for the <see cref="ConfiguredValueTaskAwaitable{TResult}"/>.</summary>
public void UnsafeOnCompleted(Action continuation) =>
_value.AsTask().ConfigureAwait(_continueOnCapturedContext).GetAwaiter().UnsafeOnCompleted(continuation);
/// <summary>Gets the task underlying <see cref="_value"/>.</summary>
internal Task<TResult> AsTask() => _value.AsTask();
/// <summary>Gets the task underlying the incomplete <see cref="_value"/>.</summary>
/// <remarks>This method is used when awaiting and IsCompleted returned false; thus we expect the value task to be wrapping a non-null task.</remarks>
Task IConfiguredValueTaskAwaiter.GetTask(out bool continueOnCapturedContext)
{
continueOnCapturedContext = _continueOnCapturedContext;
return _value.AsTaskExpectNonNull();
}
}
}
/// <summary>
/// Internal interface used to enable extract the Task from arbitrary configured ValueTask awaiters.
/// </summary>
internal interface IConfiguredValueTaskAwaiter
{
Task GetTask(out bool continueOnCapturedContext);
}
}
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