136 lines
3.8 KiB
C#
136 lines
3.8 KiB
C#
// Licensed to the .NET Foundation under one or more agreements.
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// The .NET Foundation licenses this file to you under the MIT License.
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// See the LICENSE file in the project root for more information.
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using System.Diagnostics.CodeAnalysis;
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using System.Threading;
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namespace System.Reactive.Linq.ObservableImpl
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{
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internal sealed class Latest<TSource> : PushToPullAdapter<TSource, TSource>
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{
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public Latest(IObservable<TSource> source)
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: base(source)
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{
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}
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protected override PushToPullSink<TSource, TSource> Run()
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{
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return new _();
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}
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private sealed class _ : PushToPullSink<TSource, TSource>
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{
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private readonly object _gate;
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private readonly SemaphoreSlim _semaphore;
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public _()
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{
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_gate = new object();
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_semaphore = new SemaphoreSlim(0, 1);
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}
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private bool _notificationAvailable;
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private NotificationKind _kind;
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private TSource? _value;
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private Exception? _error;
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public override void OnNext(TSource value)
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{
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var lackedValue = false;
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lock (_gate)
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{
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lackedValue = !_notificationAvailable;
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_notificationAvailable = true;
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_kind = NotificationKind.OnNext;
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_value = value;
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}
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if (lackedValue)
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{
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_semaphore.Release();
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}
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}
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public override void OnError(Exception error)
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{
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Dispose();
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var lackedValue = false;
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lock (_gate)
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{
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lackedValue = !_notificationAvailable;
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_notificationAvailable = true;
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_kind = NotificationKind.OnError;
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_error = error;
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}
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if (lackedValue)
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{
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_semaphore.Release();
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}
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}
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public override void OnCompleted()
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{
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Dispose();
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var lackedValue = false;
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lock (_gate)
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{
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lackedValue = !_notificationAvailable;
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_notificationAvailable = true;
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_kind = NotificationKind.OnCompleted;
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}
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if (lackedValue)
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{
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_semaphore.Release();
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}
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}
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public override bool TryMoveNext([MaybeNullWhen(false)] out TSource current)
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{
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NotificationKind kind;
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var value = default(TSource);
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var error = default(Exception);
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_semaphore.Wait();
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lock (_gate)
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{
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kind = _kind;
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switch (kind)
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{
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case NotificationKind.OnNext:
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value = _value;
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break;
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case NotificationKind.OnError:
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error = _error;
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break;
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}
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_notificationAvailable = false;
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}
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switch (kind)
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{
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case NotificationKind.OnNext:
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current = value!;
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return true;
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case NotificationKind.OnError:
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error!.Throw();
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break;
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case NotificationKind.OnCompleted:
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break;
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}
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current = default;
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return false;
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}
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}
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}
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}
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