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DistinctUntilChanged.cs
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DistinctUntilChanged.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.Collections.Generic;
namespace System.Reactive.Linq.ObservableImpl
{
internal sealed class DistinctUntilChanged<TSource, TKey> : Producer<TSource, DistinctUntilChanged<TSource, TKey>._>
{
private readonly IObservable<TSource> _source;
private readonly Func<TSource, TKey> _keySelector;
private readonly IEqualityComparer<TKey> _comparer;
public DistinctUntilChanged(IObservable<TSource> source, Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer)
{
_source = source;
_keySelector = keySelector;
_comparer = comparer;
}
protected override _ CreateSink(IObserver<TSource> observer) => new _(this, observer);
protected override void Run(_ sink) => sink.Run(_source);
internal sealed class _ : IdentitySink<TSource>
{
private readonly Func<TSource, TKey> _keySelector;
private readonly IEqualityComparer<TKey> _comparer;
private TKey _currentKey;
private bool _hasCurrentKey;
public _(DistinctUntilChanged<TSource, TKey> parent, IObserver<TSource> observer)
: base(observer)
{
_keySelector = parent._keySelector;
_comparer = parent._comparer;
}
public override void OnNext(TSource value)
{
TKey key;
try
{
key = _keySelector(value);
}
catch (Exception exception)
{
ForwardOnError(exception);
return;
}
var comparerEquals = false;
if (_hasCurrentKey)
{
try
{
comparerEquals = _comparer.Equals(_currentKey, key);
}
catch (Exception exception)
{
ForwardOnError(exception);
return;
}
}
if (!_hasCurrentKey || !comparerEquals)
{
_hasCurrentKey = true;
_currentKey = key;
ForwardOnNext(value);
}
}
}
}
}