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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.Collections.Generic;
using System.Diagnostics;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Threading.Tasks.Sources;
#if !netstandard
using Internal.Runtime.CompilerServices;
#endif
namespace System.Threading.Tasks
{
/// <summary>Provides an awaitable result of an asynchronous operation.</summary>
/// <remarks>
/// <see cref="ValueTask"/>s are meant to be directly awaited. To do more complicated operations with them, a <see cref="Task"/>
/// should be extracted using <see cref="AsTask"/>. Such operations might include caching an instance to be awaited later,
/// registering multiple continuations with a single operation, awaiting the same task multiple times, and using combinators over
/// multiple operations.
/// </remarks>
[AsyncMethodBuilder(typeof(AsyncValueTaskMethodBuilder))]
[StructLayout(LayoutKind.Auto)]
public readonly struct ValueTask : IEquatable<ValueTask>
{
internal static Task CompletedTask
#if netstandard
{ get; } = Task.Delay(0);
#else
=> Task.CompletedTask;
#endif
/// <summary>null if representing a successful synchronous completion, otherwise a <see cref="Task"/> or a <see cref="IValueTaskSource"/>.</summary>
internal readonly object _obj;
/// <summary>Flags providing additional details about the ValueTask's contents and behavior.</summary>
internal readonly ValueTaskFlags _flags;
/// <summary>Opaque value passed through to the <see cref="IValueTaskSource"/>.</summary>
internal readonly short _token;
// An instance created with the default ctor (a zero init'd struct) represents a synchronously, successfully completed operation.
/// <summary>Initialize the <see cref="ValueTask"/> with a <see cref="Task"/> that represents the operation.</summary>
/// <param name="task">The task.</param>
[MethodImpl(MethodImplOptions.AggressiveInlining)]
public ValueTask(Task task)
{
if (task == null)
{
ThrowHelper.ThrowArgumentNullException(ExceptionArgument.task);
}
_obj = task;
_flags = ValueTaskFlags.ObjectIsTask;
_token = 0;
}
/// <summary>Initialize the <see cref="ValueTask"/> with a <see cref="IValueTaskSource"/> object that represents the operation.</summary>
/// <param name="source">The source.</param>
/// <param name="token">Opaque value passed through to the <see cref="IValueTaskSource"/>.</param>
[MethodImpl(MethodImplOptions.AggressiveInlining)]
public ValueTask(IValueTaskSource source, short token)
{
if (source == null)
{
ThrowHelper.ThrowArgumentNullException(ExceptionArgument.source);
}
_obj = source;
_token = token;
_flags = 0;
}
/// <summary>Non-verified initialization of the struct to the specified values.</summary>
/// <param name="obj">The object.</param>
/// <param name="token">The token.</param>
/// <param name="flags">The flags.</param>
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private ValueTask(object obj, short token, ValueTaskFlags flags)
{
_obj = obj;
_token = token;
_flags = flags;
}
/// <summary>Gets whether the contination should be scheduled to the current context.</summary>
internal bool ContinueOnCapturedContext
{
[MethodImpl(MethodImplOptions.AggressiveInlining)]
get => (_flags & ValueTaskFlags.AvoidCapturedContext) == 0;
}
/// <summary>Gets whether the object in the <see cref="_obj"/> field is a <see cref="Task"/>.</summary>
internal bool ObjectIsTask
{
[MethodImpl(MethodImplOptions.AggressiveInlining)]
get => (_flags & ValueTaskFlags.ObjectIsTask) != 0;
}
/// <summary>Returns the <see cref="Task"/> stored in <see cref="_obj"/>. This uses <see cref="Unsafe"/>.</summary>
[MethodImpl(MethodImplOptions.AggressiveInlining)]
internal Task UnsafeGetTask()
{
Debug.Assert(ObjectIsTask);
Debug.Assert(_obj is Task);
return Unsafe.As<Task>(_obj);
}
/// <summary>Returns the <see cref="IValueTaskSource"/> stored in <see cref="_obj"/>. This uses <see cref="Unsafe"/>.</summary>
[MethodImpl(MethodImplOptions.AggressiveInlining)]
internal IValueTaskSource UnsafeGetValueTaskSource()
{
Debug.Assert(!ObjectIsTask);
Debug.Assert(_obj is IValueTaskSource);
return Unsafe.As<IValueTaskSource>(_obj);
}
/// <summary>Returns the hash code for this instance.</summary>
public override int GetHashCode() => _obj?.GetHashCode() ?? 0;
/// <summary>Returns a value indicating whether this value is equal to a specified <see cref="object"/>.</summary>
public override bool Equals(object obj) =>
obj is ValueTask &&
Equals((ValueTask)obj);
/// <summary>Returns a value indicating whether this value is equal to a specified <see cref="ValueTask"/> value.</summary>
public bool Equals(ValueTask other) => _obj == other._obj && _token == other._token;
/// <summary>Returns a value indicating whether two <see cref="ValueTask"/> values are equal.</summary>
public static bool operator ==(ValueTask left, ValueTask right) =>
left.Equals(right);
/// <summary>Returns a value indicating whether two <see cref="ValueTask"/> values are not equal.</summary>
public static bool operator !=(ValueTask left, ValueTask right) =>
!left.Equals(right);
/// <summary>
/// Gets a <see cref="Task"/> object to represent this ValueTask.
/// </summary>
/// <remarks>
/// It will either return the wrapped task object if one exists, or it'll
/// manufacture a new task object to represent the result.
/// </remarks>
public Task AsTask() =>
_obj == null ? ValueTask.CompletedTask :
ObjectIsTask ? UnsafeGetTask() :
GetTaskForValueTaskSource();
/// <summary>Gets a <see cref="ValueTask"/> that may be used at any point in the future.</summary>
public ValueTask Preserve() => _obj == null ? this : new ValueTask(AsTask());
/// <summary>Creates a <see cref="Task"/> to represent the <see cref="IValueTaskSource"/>.</summary>
private Task GetTaskForValueTaskSource()
{
IValueTaskSource t = UnsafeGetValueTaskSource();
ValueTaskSourceStatus status = t.GetStatus(_token);
if (status != ValueTaskSourceStatus.Pending)
{
try
{
// Propagate any exceptions that may have occurred, then return
// an already successfully completed task.
t.GetResult(_token);
return ValueTask.CompletedTask;
// If status is Faulted or Canceled, GetResult should throw. But
// we can't guarantee every implementation will do the "right thing".
// If it doesn't throw, we just treat that as success and ignore
// the status.
}
catch (Exception exc)
{
if (status == ValueTaskSourceStatus.Canceled)
{
#if netstandard
var tcs = new TaskCompletionSource<bool>();
tcs.TrySetCanceled();
return tcs.Task;
#else
if (exc is OperationCanceledException oce)
{
var task = new Task<VoidTaskResult>();
task.TrySetCanceled(oce.CancellationToken, oce);
return task;
}
else
{
return Task.FromCanceled(new CancellationToken(true));
}
#endif
}
else
{
#if netstandard
var tcs = new TaskCompletionSource<bool>();
tcs.TrySetException(exc);
return tcs.Task;
#else
return Task.FromException(exc);
#endif
}
}
}
var m = new ValueTaskSourceTask(t, _token);
return
#if netstandard
m.Task;
#else
m;
#endif
}
/// <summary>Type used to create a <see cref="Task"/> to represent a <see cref="IValueTaskSource"/>.</summary>
private sealed class ValueTaskSourceTask :
#if netstandard
TaskCompletionSource<bool>
#else
Task<VoidTaskResult>
#endif
{
private static readonly Action<object> s_completionAction = state =>
{
if (!(state is ValueTaskSourceTask vtst) ||
!(vtst._source is IValueTaskSource source))
{
// This could only happen if the IValueTaskSource passed the wrong state
// or if this callback were invoked multiple times such that the state
// was previously nulled out.
ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.state);
return;
}
vtst._source = null;
ValueTaskSourceStatus status = source.GetStatus(vtst._token);
try
{
source.GetResult(vtst._token);
vtst.TrySetResult(default);
}
catch (Exception exc)
{
if (status == ValueTaskSourceStatus.Canceled)
{
#if netstandard
vtst.TrySetCanceled();
#else
if (exc is OperationCanceledException oce)
{
vtst.TrySetCanceled(oce.CancellationToken, oce);
}
else
{
vtst.TrySetCanceled(new CancellationToken(true));
}
#endif
}
else
{
vtst.TrySetException(exc);
}
}
};
/// <summary>The associated <see cref="IValueTaskSource"/>.</summary>
private IValueTaskSource _source;
/// <summary>The token to pass through to operations on <see cref="_source"/></summary>
private readonly short _token;
public ValueTaskSourceTask(IValueTaskSource source, short token)
{
_token = token;
_source = source;
source.OnCompleted(s_completionAction, this, token, ValueTaskSourceOnCompletedFlags.None);
}
}
/// <summary>Gets whether the <see cref="ValueTask"/> represents a completed operation.</summary>
public bool IsCompleted
{
[MethodImpl(MethodImplOptions.AggressiveInlining)]
get => _obj == null || (ObjectIsTask ? UnsafeGetTask().IsCompleted : UnsafeGetValueTaskSource().GetStatus(_token) != ValueTaskSourceStatus.Pending);
}
/// <summary>Gets whether the <see cref="ValueTask"/> represents a successfully completed operation.</summary>
public bool IsCompletedSuccessfully
{
[MethodImpl(MethodImplOptions.AggressiveInlining)]
get =>
_obj == null ||
(ObjectIsTask ?
#if netstandard
UnsafeGetTask().Status == TaskStatus.RanToCompletion :
#else
UnsafeGetTask().IsCompletedSuccessfully :
#endif
UnsafeGetValueTaskSource().GetStatus(_token) == ValueTaskSourceStatus.Succeeded);
}
/// <summary>Gets whether the <see cref="ValueTask"/> represents a failed operation.</summary>
public bool IsFaulted
{
get =>
_obj != null &&
(ObjectIsTask ? UnsafeGetTask().IsFaulted : UnsafeGetValueTaskSource().GetStatus(_token) == ValueTaskSourceStatus.Faulted);
}
/// <summary>Gets whether the <see cref="ValueTask"/> represents a canceled operation.</summary>
/// <remarks>
/// If the <see cref="ValueTask"/> is backed by a result or by a <see cref="IValueTaskSource"/>,
/// this will always return false. If it's backed by a <see cref="Task"/>, it'll return the
/// value of the task's <see cref="Task.IsCanceled"/> property.
/// </remarks>
public bool IsCanceled
{
get =>
_obj != null &&
(ObjectIsTask ? UnsafeGetTask().IsCanceled : UnsafeGetValueTaskSource().GetStatus(_token) == ValueTaskSourceStatus.Canceled);
}
/// <summary>Throws the exception that caused the <see cref="ValueTask"/> to fail. If it completed successfully, nothing is thrown.</summary>
[MethodImpl(MethodImplOptions.AggressiveInlining)]
[StackTraceHidden]
internal void ThrowIfCompletedUnsuccessfully()
{
if (_obj != null)
{
if (ObjectIsTask)
{
#if netstandard
UnsafeGetTask().GetAwaiter().GetResult();
#else
TaskAwaiter.ValidateEnd(UnsafeGetTask());
#endif
}
else
{
UnsafeGetValueTaskSource().GetResult(_token);
}
}
}
/// <summary>Gets an awaiter for this <see cref="ValueTask"/>.</summary>
public ValueTaskAwaiter GetAwaiter() => new ValueTaskAwaiter(this);
/// <summary>Configures an awaiter for this <see cref="ValueTask"/>.</summary>
/// <param name="continueOnCapturedContext">
/// true to attempt to marshal the continuation back to the captured context; otherwise, false.
/// </param>
[MethodImpl(MethodImplOptions.AggressiveInlining)]
public ConfiguredValueTaskAwaitable ConfigureAwait(bool continueOnCapturedContext)
{
// TODO: Simplify once https://github.com/dotnet/coreclr/pull/16138 is fixed.
bool avoidCapture = !continueOnCapturedContext;
return new ConfiguredValueTaskAwaitable(new ValueTask(_obj, _token, _flags | Unsafe.As<bool, ValueTaskFlags>(ref avoidCapture)));
}
}
/// <summary>Provides a value type that can represent a synchronously available value or a task object.</summary>
/// <typeparam name="TResult">Specifies the type of the result.</typeparam>
/// <remarks>
/// <see cref="ValueTask{TResult}"/>s are meant to be directly awaited. To do more complicated operations with them, a <see cref="Task"/>
/// should be extracted using <see cref="AsTask"/> or <see cref="Preserve"/>. Such operations might include caching an instance to
/// be awaited later, registering multiple continuations with a single operation, awaiting the same task multiple times, and using
/// combinators over multiple operations.
/// </remarks>
[AsyncMethodBuilder(typeof(AsyncValueTaskMethodBuilder<>))]
[StructLayout(LayoutKind.Auto)]
public readonly struct ValueTask<TResult> : IEquatable<ValueTask<TResult>>
{
/// <summary>null if <see cref="_result"/> has the result, otherwise a <see cref="Task{TResult}"/> or a <see cref="IValueTaskSource{TResult}"/>.</summary>
internal readonly object _obj;
/// <summary>The result to be used if the operation completed successfully synchronously.</summary>
internal readonly TResult _result;
/// <summary>Flags providing additional details about the ValueTask's contents and behavior.</summary>
internal readonly ValueTaskFlags _flags;
/// <summary>Opaque value passed through to the <see cref="IValueTaskSource{TResult}"/>.</summary>
internal readonly short _token;
// An instance created with the default ctor (a zero init'd struct) represents a synchronously, successfully completed operation
// with a result of default(TResult).
/// <summary>Initialize the <see cref="ValueTask{TResult}"/> with a <typeparamref name="TResult"/> result value.</summary>
/// <param name="result">The result.</param>
[MethodImpl(MethodImplOptions.AggressiveInlining)]
public ValueTask(TResult result)
{
_result = result;
_obj = null;
_flags = 0;
_token = 0;
}
/// <summary>Initialize the <see cref="ValueTask{TResult}"/> with a <see cref="Task{TResult}"/> that represents the operation.</summary>
/// <param name="task">The task.</param>
[MethodImpl(MethodImplOptions.AggressiveInlining)]
public ValueTask(Task<TResult> task)
{
if (task == null)
{
ThrowHelper.ThrowArgumentNullException(ExceptionArgument.task);
}
_obj = task;
_result = default;
_flags = ValueTaskFlags.ObjectIsTask;
_token = 0;
}
/// <summary>Initialize the <see cref="ValueTask{TResult}"/> with a <see cref="IValueTaskSource{TResult}"/> object that represents the operation.</summary>
/// <param name="source">The source.</param>
/// <param name="token">Opaque value passed through to the <see cref="IValueTaskSource"/>.</param>
[MethodImpl(MethodImplOptions.AggressiveInlining)]
public ValueTask(IValueTaskSource<TResult> source, short token)
{
if (source == null)
{
ThrowHelper.ThrowArgumentNullException(ExceptionArgument.source);
}
_obj = source;
_token = token;
_result = default;
_flags = 0;
}
/// <summary>Non-verified initialization of the struct to the specified values.</summary>
/// <param name="obj">The object.</param>
/// <param name="result">The result.</param>
/// <param name="token">The token.</param>
/// <param name="flags">The flags.</param>
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private ValueTask(object obj, TResult result, short token, ValueTaskFlags flags)
{
_obj = obj;
_result = result;
_token = token;
_flags = flags;
}
/// <summary>Gets whether the contination should be scheduled to the current context.</summary>
internal bool ContinueOnCapturedContext
{
[MethodImpl(MethodImplOptions.AggressiveInlining)]
get => (_flags & ValueTaskFlags.AvoidCapturedContext) == 0;
}
/// <summary>Gets whether the object in the <see cref="_obj"/> field is a <see cref="Task{TResult}"/>.</summary>
internal bool ObjectIsTask
{
[MethodImpl(MethodImplOptions.AggressiveInlining)]
get => (_flags & ValueTaskFlags.ObjectIsTask) != 0;
}
/// <summary>Returns the <see cref="Task{TResult}"/> stored in <see cref="_obj"/>. This uses <see cref="Unsafe"/>.</summary>
[MethodImpl(MethodImplOptions.AggressiveInlining)]
internal Task<TResult> UnsafeGetTask()
{
Debug.Assert(ObjectIsTask);
Debug.Assert(_obj is Task<TResult>);
return Unsafe.As<Task<TResult>>(_obj);
}
/// <summary>Returns the <see cref="IValueTaskSource{TResult}"/> stored in <see cref="_obj"/>. This uses <see cref="Unsafe"/>.</summary>
[MethodImpl(MethodImplOptions.AggressiveInlining)]
internal IValueTaskSource<TResult> UnsafeGetValueTaskSource()
{
Debug.Assert(!ObjectIsTask);
Debug.Assert(_obj is IValueTaskSource<TResult>);
return Unsafe.As<IValueTaskSource<TResult>>(_obj);
}
/// <summary>Returns the hash code for this instance.</summary>
public override int GetHashCode() =>
_obj != null ? _obj.GetHashCode() :
_result != null ? _result.GetHashCode() :
0;
/// <summary>Returns a value indicating whether this value is equal to a specified <see cref="object"/>.</summary>
public override bool Equals(object obj) =>
obj is ValueTask<TResult> &&
Equals((ValueTask<TResult>)obj);
/// <summary>Returns a value indicating whether this value is equal to a specified <see cref="ValueTask{TResult}"/> value.</summary>
public bool Equals(ValueTask<TResult> other) =>
_obj != null || other._obj != null ?
_obj == other._obj && _token == other._token :
EqualityComparer<TResult>.Default.Equals(_result, other._result);
/// <summary>Returns a value indicating whether two <see cref="ValueTask{TResult}"/> values are equal.</summary>
public static bool operator ==(ValueTask<TResult> left, ValueTask<TResult> right) =>
left.Equals(right);
/// <summary>Returns a value indicating whether two <see cref="ValueTask{TResult}"/> values are not equal.</summary>
public static bool operator !=(ValueTask<TResult> left, ValueTask<TResult> right) =>
!left.Equals(right);
/// <summary>
/// Gets a <see cref="Task{TResult}"/> object to represent this ValueTask.
/// </summary>
/// <remarks>
/// It will either return the wrapped task object if one exists, or it'll
/// manufacture a new task object to represent the result.
/// </remarks>
public Task<TResult> AsTask() =>
_obj == null ?
#if netstandard
Task.FromResult(_result) :
#else
AsyncTaskMethodBuilder<TResult>.GetTaskForResult(_result) :
#endif
ObjectIsTask ? UnsafeGetTask() :
GetTaskForValueTaskSource();
/// <summary>Gets a <see cref="ValueTask{TResult}"/> that may be used at any point in the future.</summary>
public ValueTask<TResult> Preserve() => _obj == null ? this : new ValueTask<TResult>(AsTask());
/// <summary>Creates a <see cref="Task{TResult}"/> to represent the <see cref="IValueTaskSource{TResult}"/>.</summary>
private Task<TResult> GetTaskForValueTaskSource()
{
IValueTaskSource<TResult> t = UnsafeGetValueTaskSource();
ValueTaskSourceStatus status = t.GetStatus(_token);
if (status != ValueTaskSourceStatus.Pending)
{
try
{
// Get the result of the operation and return a task for it.
// If any exception occurred, propagate it
return
#if netstandard
Task.FromResult(t.GetResult(_token));
#else
AsyncTaskMethodBuilder<TResult>.GetTaskForResult(t.GetResult(_token));
#endif
// If status is Faulted or Canceled, GetResult should throw. But
// we can't guarantee every implementation will do the "right thing".
// If it doesn't throw, we just treat that as success and ignore
// the status.
}
catch (Exception exc)
{
if (status == ValueTaskSourceStatus.Canceled)
{
#if netstandard
var tcs = new TaskCompletionSource<TResult>();
tcs.TrySetCanceled();
return tcs.Task;
#else
if (exc is OperationCanceledException oce)
{
var task = new Task<TResult>();
task.TrySetCanceled(oce.CancellationToken, oce);
return task;
}
else
{
return Task.FromCanceled<TResult>(new CancellationToken(true));
}
#endif
}
else
{
#if netstandard
var tcs = new TaskCompletionSource<TResult>();
tcs.TrySetException(exc);
return tcs.Task;
#else
return Task.FromException<TResult>(exc);
#endif
}
}
}
var m = new ValueTaskSourceTask(t, _token);
return
#if netstandard
m.Task;
#else
m;
#endif
}
/// <summary>Type used to create a <see cref="Task{TResult}"/> to represent a <see cref="IValueTaskSource{TResult}"/>.</summary>
private sealed class ValueTaskSourceTask :
#if netstandard
TaskCompletionSource<TResult>
#else
Task<TResult>
#endif
{
private static readonly Action<object> s_completionAction = state =>
{
if (!(state is ValueTaskSourceTask vtst) ||
!(vtst._source is IValueTaskSource<TResult> source))
{
// This could only happen if the IValueTaskSource<TResult> passed the wrong state
// or if this callback were invoked multiple times such that the state
// was previously nulled out.
ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.state);
return;
}
vtst._source = null;
ValueTaskSourceStatus status = source.GetStatus(vtst._token);
try
{
vtst.TrySetResult(source.GetResult(vtst._token));
}
catch (Exception exc)
{
if (status == ValueTaskSourceStatus.Canceled)
{
#if netstandard
vtst.TrySetCanceled();
#else
if (exc is OperationCanceledException oce)
{
vtst.TrySetCanceled(oce.CancellationToken, oce);
}
else
{
vtst.TrySetCanceled(new CancellationToken(true));
}
#endif
}
else
{
vtst.TrySetException(exc);
}
}
};
/// <summary>The associated <see cref="IValueTaskSource"/>.</summary>
private IValueTaskSource<TResult> _source;
/// <summary>The token to pass through to operations on <see cref="_source"/></summary>
private readonly short _token;
public ValueTaskSourceTask(IValueTaskSource<TResult> source, short token)
{
_source = source;
_token = token;
source.OnCompleted(s_completionAction, this, token, ValueTaskSourceOnCompletedFlags.None);
}
}
/// <summary>Gets whether the <see cref="ValueTask{TResult}"/> represents a completed operation.</summary>
public bool IsCompleted
{
[MethodImpl(MethodImplOptions.AggressiveInlining)]
get => _obj == null || (ObjectIsTask ? UnsafeGetTask().IsCompleted : UnsafeGetValueTaskSource().GetStatus(_token) != ValueTaskSourceStatus.Pending);
}
/// <summary>Gets whether the <see cref="ValueTask{TResult}"/> represents a successfully completed operation.</summary>
public bool IsCompletedSuccessfully
{
[MethodImpl(MethodImplOptions.AggressiveInlining)]
get =>
_obj == null ||
(ObjectIsTask ?
#if netstandard
UnsafeGetTask().Status == TaskStatus.RanToCompletion :
#else
UnsafeGetTask().IsCompletedSuccessfully :
#endif
UnsafeGetValueTaskSource().GetStatus(_token) == ValueTaskSourceStatus.Succeeded);
}
/// <summary>Gets whether the <see cref="ValueTask{TResult}"/> represents a failed operation.</summary>
public bool IsFaulted
{
get =>
_obj != null &&
(ObjectIsTask ? UnsafeGetTask().IsFaulted : UnsafeGetValueTaskSource().GetStatus(_token) == ValueTaskSourceStatus.Faulted);
}
/// <summary>Gets whether the <see cref="ValueTask{TResult}"/> represents a canceled operation.</summary>
/// <remarks>
/// If the <see cref="ValueTask{TResult}"/> is backed by a result or by a <see cref="IValueTaskSource{TResult}"/>,
/// this will always return false. If it's backed by a <see cref="Task"/>, it'll return the
/// value of the task's <see cref="Task.IsCanceled"/> property.
/// </remarks>
public bool IsCanceled
{
get =>
_obj != null &&
(ObjectIsTask ? UnsafeGetTask().IsCanceled : UnsafeGetValueTaskSource().GetStatus(_token) == ValueTaskSourceStatus.Canceled);
}
/// <summary>Gets the result.</summary>
public TResult Result
{
[MethodImpl(MethodImplOptions.AggressiveInlining)]
get
{
if (_obj == null)
{
return _result;
}
if (ObjectIsTask)
{
#if netstandard
return UnsafeGetTask().GetAwaiter().GetResult();
#else
Task<TResult> t = UnsafeGetTask();
TaskAwaiter.ValidateEnd(t);
return t.ResultOnSuccess;
#endif
}
return UnsafeGetValueTaskSource().GetResult(_token);
}
}
/// <summary>Gets an awaiter for this <see cref="ValueTask{TResult}"/>.</summary>
[MethodImpl(MethodImplOptions.AggressiveInlining)]
public ValueTaskAwaiter<TResult> GetAwaiter() => new ValueTaskAwaiter<TResult>(this);
/// <summary>Configures an awaiter for this <see cref="ValueTask{TResult}"/>.</summary>
/// <param name="continueOnCapturedContext">
/// true to attempt to marshal the continuation back to the captured context; otherwise, false.
/// </param>
[MethodImpl(MethodImplOptions.AggressiveInlining)]
public ConfiguredValueTaskAwaitable<TResult> ConfigureAwait(bool continueOnCapturedContext)
{
// TODO: Simplify once https://github.com/dotnet/coreclr/pull/16138 is fixed.
bool avoidCapture = !continueOnCapturedContext;
return new ConfiguredValueTaskAwaitable<TResult>(new ValueTask<TResult>(_obj, _result, _token, _flags | Unsafe.As<bool, ValueTaskFlags>(ref avoidCapture)));
}
/// <summary>Gets a string-representation of this <see cref="ValueTask{TResult}"/>.</summary>
public override string ToString()
{
if (IsCompletedSuccessfully)
{
TResult result = Result;
if (result != null)
{
return result.ToString();
}
}
return string.Empty;
}
}
/// <summary>Internal flags used in the implementation of <see cref="ValueTask"/> and <see cref="ValueTask{TResult}"/>.</summary>
[Flags]
internal enum ValueTaskFlags : byte
{
/// <summary>
/// Indicates that context (e.g. SynchronizationContext) should not be captured when adding
/// a continuation.
/// </summary>
/// <remarks>
/// The value here must be 0x1, to match the value of a true Boolean reinterpreted as a byte.
/// This only has meaning when awaiting a ValueTask, with ConfigureAwait creating a new
/// ValueTask setting or not setting this flag appropriately.
/// </remarks>
AvoidCapturedContext = 0x1,
/// <summary>
/// Indicates that the ValueTask's object field stores a Task. This is used to avoid
/// a type check on whatever is stored in the object field.
/// </summary>
ObjectIsTask = 0x2
}
}
|