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// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.
using System.Collections.Generic;
using System.Reactive.Concurrency;
using System.Reactive.Disposables;
using System.Reactive.Subjects;
using System.Threading;
#if !NO_TPL
using System.Threading.Tasks;
#endif
namespace System.Reactive.Linq
{
#if !NO_PERF
using Observαble;
#endif
internal partial class QueryLanguage
{
#region ForEachAsync
#if !NO_TPL
public virtual Task ForEachAsync<TSource>(IObservable<TSource> source, Action<TSource> onNext)
{
return ForEachAsync_(source, onNext, CancellationToken.None);
}
public virtual Task ForEachAsync<TSource>(IObservable<TSource> source, Action<TSource> onNext, CancellationToken cancellationToken)
{
return ForEachAsync_(source, onNext, cancellationToken);
}
public virtual Task ForEachAsync<TSource>(IObservable<TSource> source, Action<TSource, int> onNext)
{
var i = 0;
return ForEachAsync_(source, x => onNext(x, checked(i++)), CancellationToken.None);
}
public virtual Task ForEachAsync<TSource>(IObservable<TSource> source, Action<TSource, int> onNext, CancellationToken cancellationToken)
{
var i = 0;
return ForEachAsync_(source, x => onNext(x, checked(i++)), cancellationToken);
}
private static Task ForEachAsync_<TSource>(IObservable<TSource> source, Action<TSource> onNext, CancellationToken cancellationToken)
{
var tcs = new TaskCompletionSource<object>();
var subscription = new SingleAssignmentDisposable();
var ctr = default(CancellationTokenRegistration);
if (cancellationToken.CanBeCanceled)
{
ctr = cancellationToken.Register(() =>
{
tcs.TrySetCanceled();
subscription.Dispose();
});
}
if (!cancellationToken.IsCancellationRequested)
{
// Making sure we always complete, even if disposing throws.
var dispose = new Action<Action>(action =>
{
try
{
ctr.Dispose(); // no null-check needed (struct)
subscription.Dispose();
}
catch (Exception ex)
{
tcs.TrySetException(ex);
return;
}
action();
});
var taskCompletionObserver = new AnonymousObserver<TSource>(
x =>
{
if (!subscription.IsDisposed)
{
try
{
onNext(x);
}
catch (Exception exception)
{
dispose(() => tcs.TrySetException(exception));
}
}
},
exception =>
{
dispose(() => tcs.TrySetException(exception));
},
() =>
{
dispose(() => tcs.TrySetResult(null));
}
);
//
// Subtle race condition: if the source completes before we reach the line below, the SingleAssigmentDisposable
// will already have been disposed. Upon assignment, the disposable resource being set will be disposed on the
// spot, which may throw an exception. (See TFS 487142)
//
try
{
//
// [OK] Use of unsafe Subscribe: we're catching the exception here to set the TaskCompletionSource.
//
// Notice we could use a safe subscription to route errors through OnError, but we still need the
// exception handling logic here for the reason explained above. We cannot afford to throw here
// and as a result never set the TaskCompletionSource, so we tunnel everything through here.
//
subscription.Disposable = source.Subscribe/*Unsafe*/(taskCompletionObserver);
}
catch (Exception ex)
{
tcs.TrySetException(ex);
}
}
return tcs.Task;
}
#endif
#endregion
#region + Case +
public virtual IObservable<TResult> Case<TValue, TResult>(Func<TValue> selector, IDictionary<TValue, IObservable<TResult>> sources)
{
return Case(selector, sources, Empty<TResult>());
}
public virtual IObservable<TResult> Case<TValue, TResult>(Func<TValue> selector, IDictionary<TValue, IObservable<TResult>> sources, IScheduler scheduler)
{
return Case(selector, sources, Empty<TResult>(scheduler));
}
public virtual IObservable<TResult> Case<TValue, TResult>(Func<TValue> selector, IDictionary<TValue, IObservable<TResult>> sources, IObservable<TResult> defaultSource)
{
#if !NO_PERF
return new Case<TValue, TResult>(selector, sources, defaultSource);
#else
return Observable.Defer(() =>
{
IObservable<TResult> result;
if (!sources.TryGetValue(selector(), out result))
result = defaultSource;
return result;
});
#endif
}
#endregion
#region + DoWhile +
public virtual IObservable<TSource> DoWhile<TSource>(IObservable<TSource> source, Func<bool> condition)
{
#if !NO_PERF
return new DoWhile<TSource>(source, condition);
#else
return source.Concat(While(condition, source));
#endif
}
#endregion
#region + For +
public virtual IObservable<TResult> For<TSource, TResult>(IEnumerable<TSource> source, Func<TSource, IObservable<TResult>> resultSelector)
{
#if !NO_PERF
return new For<TSource, TResult>(source, resultSelector);
#else
return ForCore(source, resultSelector).Concat();
#endif
}
#if NO_PERF
static IEnumerable<IObservable<TResult>> ForCore<TSource, TResult>(IEnumerable<TSource> source, Func<TSource, IObservable<TResult>> resultSelector)
{
foreach (var item in source)
yield return resultSelector(item);
}
#endif
#endregion
#region + If +
public virtual IObservable<TResult> If<TResult>(Func<bool> condition, IObservable<TResult> thenSource)
{
return If(condition, thenSource, Empty<TResult>());
}
public virtual IObservable<TResult> If<TResult>(Func<bool> condition, IObservable<TResult> thenSource, IScheduler scheduler)
{
return If(condition, thenSource, Empty<TResult>(scheduler));
}
public virtual IObservable<TResult> If<TResult>(Func<bool> condition, IObservable<TResult> thenSource, IObservable<TResult> elseSource)
{
#if !NO_PERF
return new If<TResult>(condition, thenSource, elseSource);
#else
return Observable.Defer(() => condition() ? thenSource : elseSource);
#endif
}
#endregion
#region + While +
public virtual IObservable<TSource> While<TSource>(Func<bool> condition, IObservable<TSource> source)
{
#if !NO_PERF
return new While<TSource>(condition, source);
#else
return WhileCore(condition, source).Concat();
#endif
}
#if NO_PERF
static IEnumerable<IObservable<TSource>> WhileCore<TSource>(Func<bool> condition, IObservable<TSource> source)
{
while (condition())
yield return source;
}
#endif
#endregion
}
}
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