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WithLatestFrom.cs
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WithLatestFrom.cs
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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the Apache 2.0 License.
// See the LICENSE file in the project root for more information.
using System.Reactive.Disposables;
namespace System.Reactive.Linq.ObservableImpl
{
internal sealed class WithLatestFrom<TFirst, TSecond, TResult> : Producer<TResult, WithLatestFrom<TFirst, TSecond, TResult>._>
{
private readonly IObservable<TFirst> _first;
private readonly IObservable<TSecond> _second;
private readonly Func<TFirst, TSecond, TResult> _resultSelector;
public WithLatestFrom(IObservable<TFirst> first, IObservable<TSecond> second, Func<TFirst, TSecond, TResult> resultSelector)
{
_first = first;
_second = second;
_resultSelector = resultSelector;
}
protected override _ CreateSink(IObserver<TResult> observer) => new _(_resultSelector, observer);
protected override void Run(_ sink) => sink.Run(_first, _second);
internal sealed class _ : IdentitySink<TResult>
{
private readonly Func<TFirst, TSecond, TResult> _resultSelector;
public _(Func<TFirst, TSecond, TResult> resultSelector, IObserver<TResult> observer)
: base(observer)
{
_resultSelector = resultSelector;
}
private object _gate;
private volatile bool _hasLatest;
private TSecond _latest;
private object _latestGate;
private IDisposable _secondDisposable;
public void Run(IObservable<TFirst> first, IObservable<TSecond> second)
{
_gate = new object();
_latestGate = new object();
var fstO = new FirstObserver(this);
var sndO = new SecondObserver(this);
Disposable.SetSingle(ref _secondDisposable, second.SubscribeSafe(sndO));
SetUpstream(first.SubscribeSafe(fstO));
}
protected override void Dispose(bool disposing)
{
if (disposing)
{
Disposable.TryDispose(ref _secondDisposable);
}
base.Dispose(disposing);
}
private sealed class FirstObserver : IObserver<TFirst>
{
private readonly _ _parent;
public FirstObserver(_ parent)
{
_parent = parent;
}
public void OnCompleted()
{
lock (_parent._gate)
{
_parent.ForwardOnCompleted();
}
}
public void OnError(Exception error)
{
lock (_parent._gate)
{
_parent.ForwardOnError(error);
}
}
public void OnNext(TFirst value)
{
if (_parent._hasLatest) // Volatile read
{
TSecond latest;
lock (_parent._latestGate)
{
latest = _parent._latest;
}
TResult res;
try
{
res = _parent._resultSelector(value, latest);
}
catch (Exception ex)
{
lock (_parent._gate)
{
_parent.ForwardOnError(ex);
}
return;
}
lock (_parent._gate)
{
_parent.ForwardOnNext(res);
}
}
}
}
private sealed class SecondObserver : IObserver<TSecond>
{
private readonly _ _parent;
public SecondObserver(_ parent)
{
_parent = parent;
}
public void OnCompleted()
{
Disposable.TryDispose(ref _parent._secondDisposable);
}
public void OnError(Exception error)
{
lock (_parent._gate)
{
_parent.ForwardOnError(error);
}
}
public void OnNext(TSecond value)
{
lock (_parent._latestGate)
{
_parent._latest = value;
}
if (!_parent._hasLatest)
{
_parent._hasLatest = true;
}
}
}
}
}
}