128 lines
5.3 KiB
C#
128 lines
5.3 KiB
C#
// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.
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using System.Collections.Generic;
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namespace System.Reactive
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{
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/// <summary>
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/// Base class for classes that expose an observable sequence as a well-known event pattern (sender, event arguments).
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/// Contains functionality to maintain a map of event handler delegates to observable sequence subscriptions. Subclasses
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/// should only add an event with custom add and remove methods calling into the base class's operations.
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/// </summary>
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/// <typeparam name="TSender">The type of the sender that raises the event.</typeparam>
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/// <typeparam name="TEventArgs">The type of the event data generated by the event.</typeparam>
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public abstract class EventPatternSourceBase<TSender, TEventArgs>
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#if !NO_EVENTARGS_CONSTRAINT
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where TEventArgs : EventArgs
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#endif
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{
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private readonly IObservable<EventPattern<TSender, TEventArgs>> _source;
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private readonly Dictionary<Delegate, Stack<IDisposable>> _subscriptions;
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private readonly Action<Action<TSender, TEventArgs>, /*object,*/ EventPattern<TSender, TEventArgs>> _invokeHandler;
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/// <summary>
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/// Creates a new event pattern source.
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/// </summary>
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/// <param name="source">Source sequence to expose as an event.</param>
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/// <param name="invokeHandler">Delegate used to invoke the event for each element of the sequence.</param>
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/// <exception cref="ArgumentNullException"><paramref name="source"/> or <paramref name="invokeHandler"/> is null.</exception>
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protected EventPatternSourceBase(IObservable<EventPattern<TSender, TEventArgs>> source, Action<Action<TSender, TEventArgs>, /*object,*/ EventPattern<TSender, TEventArgs>> invokeHandler)
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{
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if (source == null)
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throw new ArgumentNullException("source");
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if (invokeHandler == null)
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throw new ArgumentNullException("invokeHandler");
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_source = source;
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_invokeHandler = invokeHandler;
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_subscriptions = new Dictionary<Delegate, Stack<IDisposable>>();
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}
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/// <summary>
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/// Adds the specified event handler, causing a subscription to the underlying source.
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/// </summary>
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/// <param name="handler">Event handler to add. The same delegate should be passed to the Remove operation in order to remove the event handler.</param>
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/// <param name="invoke">Invocation delegate to raise the event in the derived class.</param>
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/// <exception cref="ArgumentNullException"><paramref name="handler"/> or <paramref name="invoke"/> is null.</exception>
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protected void Add(Delegate handler, Action<TSender, TEventArgs> invoke)
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{
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if (handler == null)
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throw new ArgumentNullException("handler");
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if (invoke == null)
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throw new ArgumentNullException("invoke");
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var gate = new object();
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var isAdded = false;
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var isDone = false;
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var remove = new Action(() =>
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{
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lock (gate)
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{
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if (isAdded)
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Remove(handler);
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else
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isDone = true;
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}
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});
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//
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// [OK] Use of unsafe Subscribe: non-pretentious wrapper of an observable in an event; exceptions can occur during +=.
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//
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var d = _source.Subscribe/*Unsafe*/(
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x => _invokeHandler(invoke, /*this,*/ x),
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ex => { remove(); ex.Throw(); },
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() => remove()
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);
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lock (gate)
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{
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if (!isDone)
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{
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Add(handler, d);
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isAdded = true;
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}
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}
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}
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private void Add(Delegate handler, IDisposable disposable)
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{
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lock (_subscriptions)
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{
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var l = new Stack<IDisposable>();
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if (!_subscriptions.TryGetValue(handler, out l))
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_subscriptions[handler] = l = new Stack<IDisposable>();
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l.Push(disposable);
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}
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}
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/// <summary>
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/// Removes the specified event handler, causing a disposal of the corresponding subscription to the underlying source that was created during the Add operation.
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/// </summary>
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/// <param name="handler">Event handler to remove. This should be the same delegate as one that was passed to the Add operation.</param>
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/// <exception cref="ArgumentNullException"><paramref name="handler"/> is null.</exception>
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protected void Remove(Delegate handler)
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{
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if (handler == null)
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throw new ArgumentNullException("handler");
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var d = default(IDisposable);
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lock (_subscriptions)
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{
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var l = new Stack<IDisposable>();
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if (_subscriptions.TryGetValue(handler, out l))
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{
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d = l.Pop();
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if (l.Count == 0)
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_subscriptions.Remove(handler);
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}
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}
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if (d != null)
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d.Dispose();
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}
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}
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}
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