mirror of https://github.com/ppy/osu
70 lines
3.1 KiB
C#
70 lines
3.1 KiB
C#
// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
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// See the LICENCE file in the repository root for full licence text.
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#nullable enable
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using System;
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using System.Threading;
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using System.Threading.Tasks;
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using osu.Framework.Extensions.ObjectExtensions;
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namespace osu.Game.Extensions
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{
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public static class TaskExtensions
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{
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/// <summary>
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/// Add a continuation to be performed only after the attached task has completed.
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/// </summary>
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/// <param name="task">The previous task to be awaited on.</param>
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/// <param name="action">The action to run.</param>
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/// <param name="cancellationToken">An optional cancellation token. Will only cancel the provided action, not the sequence.</param>
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/// <returns>A task representing the provided action.</returns>
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public static Task ContinueWithSequential(this Task task, Action action, CancellationToken cancellationToken = default) =>
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task.ContinueWithSequential(() => Task.Run(action, cancellationToken), cancellationToken);
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/// <summary>
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/// Add a continuation to be performed only after the attached task has completed.
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/// </summary>
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/// <param name="task">The previous task to be awaited on.</param>
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/// <param name="continuationFunction">The continuation to run. Generally should be an async function.</param>
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/// <param name="cancellationToken">An optional cancellation token. Will only cancel the provided action, not the sequence.</param>
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/// <returns>A task representing the provided action.</returns>
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public static Task ContinueWithSequential(this Task task, Func<Task> continuationFunction, CancellationToken cancellationToken = default)
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{
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var tcs = new TaskCompletionSource<bool>();
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task.ContinueWith(t =>
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{
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// the previous task has finished execution or been cancelled, so we can run the provided continuation.
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if (cancellationToken.IsCancellationRequested)
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{
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tcs.SetCanceled();
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}
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else
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{
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continuationFunction().ContinueWith(continuationTask =>
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{
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if (cancellationToken.IsCancellationRequested || continuationTask.IsCanceled)
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{
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tcs.TrySetCanceled();
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}
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else if (continuationTask.IsFaulted)
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{
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tcs.TrySetException(continuationTask.Exception.AsNonNull());
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}
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else
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{
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tcs.TrySetResult(true);
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}
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}, cancellationToken: default);
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}
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}, cancellationToken: default);
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// importantly, we are not returning the continuation itself but rather a task which represents its status in sequential execution order.
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// this will not be cancelled or completed until the previous task has also.
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return tcs.Task;
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}
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}
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}
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