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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_SYNCCTX
using System.Reactive.Disposables;
using System.Threading;
namespace System.Reactive.Concurrency
{
/// <summary>
/// Represents an object that schedules units of work on a provided <seealso cref="T:System.Threading.SynchronizationContext"/>.
/// </summary>
public class SynchronizationContextScheduler : LocalScheduler
{
private readonly SynchronizationContext _context;
private readonly bool _alwaysPost;
/// <summary>
/// Creates an object that schedules units of work on the provided <see cref="T:System.Threading.SynchronizationContext"/>.
/// </summary>
/// <param name="context">Synchronization context to schedule units of work on.</param>
/// <exception cref="ArgumentNullException"><paramref name="context"/> is null.</exception>
public SynchronizationContextScheduler(SynchronizationContext context)
{
if (context == null)
throw new ArgumentNullException("context");
_context = context;
_alwaysPost = true;
}
/// <summary>
/// Creates an object that schedules units of work on the provided <see cref="T:System.Threading.SynchronizationContext"/>.
/// </summary>
/// <param name="context">Synchronization context to schedule units of work on.</param>
/// <param name="alwaysPost">Configures whether scheduling always posts to the synchronization context, regardless whether the caller is on the same synchronization context.</param>
/// <exception cref="ArgumentNullException"><paramref name="context"/> is null.</exception>
public SynchronizationContextScheduler(SynchronizationContext context, bool alwaysPost)
{
if (context == null)
throw new ArgumentNullException("context");
_context = context;
_alwaysPost = alwaysPost;
}
/// <summary>
/// Schedules an action to be executed.
/// </summary>
/// <typeparam name="TState">The type of the state passed to the scheduled action.</typeparam>
/// <param name="state">State passed to the action to be executed.</param>
/// <param name="action">Action to be executed.</param>
/// <returns>The disposable object used to cancel the scheduled action (best effort).</returns>
/// <exception cref="ArgumentNullException"><paramref name="action"/> is null.</exception>
public override IDisposable Schedule<TState>(TState state, Func<IScheduler, TState, IDisposable> action)
{
if (action == null)
throw new ArgumentNullException("action");
var d = new SingleAssignmentDisposable();
if (!_alwaysPost && _context == SynchronizationContext.Current)
{
d.Disposable = action(this, state);
}
else
{
_context.PostWithStartComplete(() =>
{
if (!d.IsDisposed)
d.Disposable = action(this, state);
});
}
return d;
}
/// <summary>
/// Schedules an action to be executed after dueTime.
/// </summary>
/// <typeparam name="TState">The type of the state passed to the scheduled action.</typeparam>
/// <param name="state">State passed to the action to be executed.</param>
/// <param name="action">Action to be executed.</param>
/// <param name="dueTime">Relative time after which to execute the action.</param>
/// <returns>The disposable object used to cancel the scheduled action (best effort).</returns>
/// <exception cref="ArgumentNullException"><paramref name="action"/> is null.</exception>
public override IDisposable Schedule<TState>(TState state, TimeSpan dueTime, Func<IScheduler, TState, IDisposable> action)
{
if (action == null)
throw new ArgumentNullException("action");
var dt = Scheduler.Normalize(dueTime);
if (dt.Ticks == 0)
return Schedule(state, action);
return DefaultScheduler.Instance.Schedule(state, dt, (_, state1) => Schedule(state1, action));
}
}
}
#endif
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