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using System; | |
using System.Collections.Concurrent; | |
using System.Threading; | |
using System.Threading.Tasks; | |
namespace AsyncScheduler | |
{ | |
public class ActionQueueScheduler : IDisposable | |
{ | |
private readonly ConcurrentQueue<Func<Task>> queue; | |
private readonly ConcurrentQueue<Func<Task>> immediate; | |
private readonly CancellationTokenSource canceller; | |
private int state; // [ 0: stopped, 1: setup, 2: running ] | |
private Task runner; | |
public ActionQueueScheduler() | |
{ | |
this.queue = new ConcurrentQueue<Func<Task>>(); | |
this.immediate = new ConcurrentQueue<Func<Task>>(); | |
this.canceller = new CancellationTokenSource(); | |
} | |
public Task Add(Action<CancellationToken> action) | |
=> this.Add(token => { action(token); return default(object); }); | |
public Task<T> Add<T>(Func<CancellationToken, T> action) | |
{ | |
if (this.canceller.IsCancellationRequested) | |
return Task.FromCanceled<T>(this.canceller.Token); | |
var tcs = new TaskCompletionSource<T>(); | |
this.queue.Enqueue(() => this.InvokeAction(action, tcs)); | |
this.Run(); | |
return tcs.Task; | |
} | |
public Task Add(Func<CancellationToken, Task> action) | |
=> this.Add(async token => { await action(token); return default(object); }); | |
public Task<T> Add<T>(Func<CancellationToken, Task<T>> action) | |
{ | |
if (this.canceller.IsCancellationRequested) | |
return Task.FromCanceled<T>(this.canceller.Token); | |
var tcs = new TaskCompletionSource<T>(); | |
this.queue.Enqueue(() => this.InvokeActionAsync(action, tcs)); | |
this.Run(); | |
return tcs.Task; | |
} | |
public Task Interrupt(Action<CancellationToken> action) | |
=> this.Interrupt(token => { action(token); return default(object); }); | |
public Task<T> Interrupt<T>(Func<CancellationToken, T> action) | |
{ | |
if (this.canceller.IsCancellationRequested) | |
return Task.FromCanceled<T>(this.canceller.Token); | |
var tcs = new TaskCompletionSource<T>(); | |
this.immediate.Enqueue(() => this.InvokeAction(action, tcs)); | |
this.Run(); | |
return tcs.Task; | |
} | |
public Task Interrupt(Func<CancellationToken, Task> action) | |
=> this.Interrupt(async token => { await action(token); return default(object); }); | |
public Task<T> Interrupt<T>(Func<CancellationToken, Task<T>> action) | |
{ | |
if (this.canceller.IsCancellationRequested) | |
return Task.FromCanceled<T>(this.canceller.Token); | |
var tcs = new TaskCompletionSource<T>(); | |
this.immediate.Enqueue(() => this.InvokeActionAsync(action, tcs)); | |
this.Run(); | |
return tcs.Task; | |
} | |
private Task InvokeAction<T>(Func<CancellationToken, T> action, TaskCompletionSource<T> tcs) | |
{ | |
try | |
{ | |
this.canceller.Token.ThrowIfCancellationRequested(); | |
tcs.TrySetResult(action(this.canceller.Token)); | |
} | |
catch (OperationCanceledException exception) | |
{ | |
tcs.TrySetCanceled(exception.CancellationToken); | |
} | |
catch (Exception exception) | |
{ | |
tcs.TrySetException(exception); | |
} | |
return Task.FromResult(default(object)); | |
} | |
private async Task InvokeActionAsync<T>(Func<CancellationToken, Task<T>> asyncAction, TaskCompletionSource<T> tcs) | |
{ | |
try | |
{ | |
this.canceller.Token.ThrowIfCancellationRequested(); | |
tcs.TrySetResult(await asyncAction(this.canceller.Token).ConfigureAwait(false)); | |
} | |
catch (OperationCanceledException exception) | |
{ | |
tcs.TrySetCanceled(exception.CancellationToken); | |
} | |
catch (Exception exception) | |
{ | |
tcs.TrySetException(exception); | |
} | |
} | |
private Task Run() | |
{ | |
while (Interlocked.CompareExchange(ref this.state, 1, 0) != 0) | |
if (this.state == 2) | |
return this.runner; | |
this.runner = Task.Run(async () => | |
{ | |
var action = default(Func<Task>); | |
while (true) | |
{ | |
if (this.immediate.TryDequeue(out action)) | |
await action().ConfigureAwait(false); | |
else if (this.queue.TryDequeue(out action)) | |
await action().ConfigureAwait(false); | |
else | |
break; | |
} | |
while (Interlocked.CompareExchange(ref this.state, 0, 2) != 2) ; | |
if (this.queue.Count != 0) | |
await this.Run().ConfigureAwait(false); | |
}); | |
Interlocked.Exchange(ref this.state, 2); | |
return this.runner; | |
} | |
public void Dispose() | |
{ | |
this.canceller.Cancel(); | |
this.Run().Wait(); | |
} | |
} | |
} |
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