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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.Collections.Generic;
using System.Reactive.Concurrency;
using System.Reactive.Disposables;
namespace System.Reactive
{
abstract class TailRecursiveSink<TSource> : Sink<TSource>, IObserver<TSource>
{
public TailRecursiveSink(IObserver<TSource> observer, IDisposable cancel)
: base(observer, cancel)
{
}
private bool _isDisposed;
private SerialDisposable _subscription;
private AsyncLock _gate;
private Stack<IEnumerator<IObservable<TSource>>> _stack;
private Stack<int?> _length;
protected Action _recurse;
public IDisposable Run(IEnumerable<IObservable<TSource>> sources)
{
_isDisposed = false;
_subscription = new SerialDisposable();
_gate = new AsyncLock();
_stack = new Stack<IEnumerator<IObservable<TSource>>>();
_length = new Stack<int?>();
var e = default(IEnumerator<IObservable<TSource>>);
if (!TryGetEnumerator(sources, out e))
return Disposable.Empty;
_stack.Push(e);
_length.Push(Helpers.GetLength(sources));
var cancelable = SchedulerDefaults.TailRecursion.Schedule(self =>
{
_recurse = self;
_gate.Wait(MoveNext);
});
return new CompositeDisposable(_subscription, cancelable, Disposable.Create(() => _gate.Wait(Dispose)));
}
protected abstract IEnumerable<IObservable<TSource>> Extract(IObservable<TSource> source);
private void MoveNext()
{
var hasNext = false;
var next = default(IObservable<TSource>);
do
{
if (_stack.Count == 0)
break;
if (_isDisposed)
return;
var e = _stack.Peek();
var l = _length.Peek();
var current = default(IObservable<TSource>);
try
{
hasNext = e.MoveNext();
if (hasNext)
current = e.Current;
}
catch (Exception ex)
{
e.Dispose();
base._observer.OnError(ex);
base.Dispose();
return;
}
if (!hasNext)
{
e.Dispose();
_stack.Pop();
_length.Pop();
}
else
{
var r = l - 1;
_length.Pop();
_length.Push(r);
try
{
next = Helpers.Unpack(current);
}
catch (Exception exception)
{
e.Dispose();
base._observer.OnError(exception);
base.Dispose();
return;
}
//
// Tail recursive case; drop the current frame.
//
if (r == 0)
{
e.Dispose();
_stack.Pop();
_length.Pop();
}
//
// Flattening of nested sequences. Prevents stack overflow in observers.
//
var nextSeq = Extract(next);
if (nextSeq != null)
{
var nextEnumerator = default(IEnumerator<IObservable<TSource>>);
if (!TryGetEnumerator(nextSeq, out nextEnumerator))
return;
_stack.Push(nextEnumerator);
_length.Push(Helpers.GetLength(nextSeq));
hasNext = false;
}
}
} while (!hasNext);
if (!hasNext)
{
Done();
return;
}
var d = new SingleAssignmentDisposable();
_subscription.Disposable = d;
d.Disposable = next.SubscribeSafe(this);
}
private new void Dispose()
{
while (_stack.Count > 0)
{
var e = _stack.Pop();
_length.Pop();
e.Dispose();
}
_isDisposed = true;
}
private bool TryGetEnumerator(IEnumerable<IObservable<TSource>> sources, out IEnumerator<IObservable<TSource>> result)
{
try
{
result = sources.GetEnumerator();
return true;
}
catch (Exception exception)
{
base._observer.OnError(exception);
base.Dispose();
result = null;
return false;
}
}
public abstract void OnCompleted();
public abstract void OnError(Exception error);
public abstract void OnNext(TSource value);
protected virtual void Done()
{
base._observer.OnCompleted();
base.Dispose();
}
}
}
#endif
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