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// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.
#if !NO_PERF
using System;
using System.Collections.Generic;
using System.Threading;
namespace System.Reactive.Linq.ObservableImpl
{
class MostRecent<TSource> : PushToPullAdapter<TSource, TSource>
{
private readonly TSource _initialValue;
public MostRecent(IObservable<TSource> source, TSource initialValue)
: base(source)
{
_initialValue = initialValue;
}
protected override PushToPullSink<TSource, TSource> Run(IDisposable subscription)
{
return new _(_initialValue, subscription);
}
class _ : PushToPullSink<TSource, TSource>
{
public _(TSource initialValue, IDisposable subscription)
: base(subscription)
{
_kind = NotificationKind.OnNext;
_value = initialValue;
}
private volatile NotificationKind _kind;
private TSource _value;
private Exception _error;
public override void OnNext(TSource value)
{
_value = value;
_kind = NotificationKind.OnNext; // Write last!
}
public override void OnError(Exception error)
{
base.Dispose();
_error = error;
_kind = NotificationKind.OnError; // Write last!
}
public override void OnCompleted()
{
base.Dispose();
_kind = NotificationKind.OnCompleted; // Write last!
}
public override bool TryMoveNext(out TSource current)
{
//
// Notice the _kind field is marked volatile and read before the other fields.
//
// In case of a concurrent change, we may read a stale OnNext value, which is
// fine because this push-to-pull adapter is about sampling.
//
switch (_kind)
{
case NotificationKind.OnNext:
current = _value;
return true;
case NotificationKind.OnError:
_error.Throw();
break;
case NotificationKind.OnCompleted:
break;
}
current = default(TSource);
return false;
}
}
}
}
#endif
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