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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.Reactive.Concurrency;
using System.Reactive.Disposables;
using System.Threading;
namespace System.Reactive.Linq.ObservableImpl
{
class TakeUntil<TSource, TOther> : Producer<TSource>
{
private readonly IObservable<TSource> _source;
private readonly IObservable<TOther> _other;
public TakeUntil(IObservable<TSource> source, IObservable<TOther> other)
{
_source = source;
_other = other;
}
protected override IDisposable Run(IObserver<TSource> observer, IDisposable cancel, Action<IDisposable> setSink)
{
var sink = new _(this, observer, cancel);
setSink(sink);
return sink.Run();
}
class _ : Sink<TSource>
{
private readonly TakeUntil<TSource, TOther> _parent;
public _(TakeUntil<TSource, TOther> parent, IObserver<TSource> observer, IDisposable cancel)
: base(observer, cancel)
{
_parent = parent;
}
public IDisposable Run()
{
var sourceObserver = new T(this);
var otherObserver = new O(this, sourceObserver);
// COMPAT - Order of Subscribe calls per v1.0.10621
var otherSubscription = _parent._other.SubscribeSafe(otherObserver);
otherObserver.Disposable = otherSubscription;
var sourceSubscription = _parent._source.SubscribeSafe(sourceObserver);
return new CompositeDisposable(
otherSubscription,
sourceSubscription
);
}
/*
* We tried a more fine-grained synchronization scheme to make TakeUntil more efficient, but
* this requires several CAS instructions, which quickly add up to being non-beneficial.
*
* Notice an approach where the "other" channel performs an Interlocked.Exchange operation on
* the _parent._observer field to substitute it with a NopObserver<TSource> doesn't work,
* because the "other" channel still need to send an OnCompleted message, which could happen
* concurrently with another message when the "source" channel has already read from the
* _parent._observer field between making the On* call.
*
* Fixing this issue requires an ownership transfer mechanism for channels to get exclusive
* access to the outgoing observer while dispatching a message. Doing this more fine-grained
* than using locks turns out to be tricky and doesn't reduce cost.
*/
class T : IObserver<TSource>
{
private readonly _ _parent;
public volatile bool _open;
public T(_ parent)
{
_parent = parent;
_open = false;
}
public void OnNext(TSource value)
{
if (_open)
{
_parent._observer.OnNext(value);
}
else
{
lock (_parent)
{
_parent._observer.OnNext(value);
}
}
}
public void OnError(Exception error)
{
lock (_parent)
{
_parent._observer.OnError(error);
_parent.Dispose();
}
}
public void OnCompleted()
{
lock (_parent)
{
_parent._observer.OnCompleted();
_parent.Dispose();
}
}
}
class O : IObserver<TOther>
{
private readonly _ _parent;
private readonly T _sourceObserver;
private readonly SingleAssignmentDisposable _subscription;
public O(_ parent, T sourceObserver)
{
_parent = parent;
_sourceObserver = sourceObserver;
_subscription = new SingleAssignmentDisposable();
}
public IDisposable Disposable
{
set { _subscription.Disposable = value; }
}
public void OnNext(TOther value)
{
lock (_parent)
{
_parent._observer.OnCompleted();
_parent.Dispose();
}
}
public void OnError(Exception error)
{
lock (_parent)
{
_parent._observer.OnError(error);
_parent.Dispose();
}
}
public void OnCompleted()
{
lock (_parent)
{
_sourceObserver._open = true;
_subscription.Dispose();
}
}
}
}
}
class TakeUntil<TSource> : Producer<TSource>
{
private readonly IObservable<TSource> _source;
private readonly DateTimeOffset _endTime;
internal readonly IScheduler _scheduler;
public TakeUntil(IObservable<TSource> source, DateTimeOffset endTime, IScheduler scheduler)
{
_source = source;
_endTime = endTime;
_scheduler = scheduler;
}
public IObservable<TSource> Omega(DateTimeOffset endTime)
{
//
// Minimum semantics:
//
// t 0--1--2--3--4--5--6--7-> t 0--1--2--3--4--5--6--7->
//
// xs --o--o--o--o--o--o--| xs --o--o--o--o--o--o--|
// xs.TU(5AM) --o--o--o--o--o| xs.TU(3AM) --o--o--o|
// xs.TU(5AM).TU(3AM) --o--o--o| xs.TU(3AM).TU(5AM) --o--o--o|
//
if (_endTime <= endTime)
return this;
else
return new TakeUntil<TSource>(_source, endTime, _scheduler);
}
protected override IDisposable Run(IObserver<TSource> observer, IDisposable cancel, Action<IDisposable> setSink)
{
var sink = new _(this, observer, cancel);
setSink(sink);
return sink.Run();
}
class _ : Sink<TSource>, IObserver<TSource>
{
private readonly TakeUntil<TSource> _parent;
public _(TakeUntil<TSource> parent, IObserver<TSource> observer, IDisposable cancel)
: base(observer, cancel)
{
_parent = parent;
}
private object _gate;
public IDisposable Run()
{
_gate = new object();
var t = _parent._scheduler.Schedule(_parent._endTime, Tick);
var d = _parent._source.SubscribeSafe(this);
return new CompositeDisposable(t, d);
}
private void Tick()
{
lock (_gate)
{
base._observer.OnCompleted();
base.Dispose();
}
}
public void OnNext(TSource value)
{
lock (_gate)
{
base._observer.OnNext(value);
}
}
public void OnError(Exception error)
{
lock (_gate)
{
base._observer.OnError(error);
base.Dispose();
}
}
public void OnCompleted()
{
lock (_gate)
{
base._observer.OnCompleted();
base.Dispose();
}
}
}
}
}
#endif
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