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//
// TaskScheduler.cs
//
// Authors:
// Jérémie "Garuma" Laval <jeremie.laval@gmail.com>
// Marek Safar <marek.safar@gmail.com>
//
// Copyright (c) 2009 Jérémie "Garuma" Laval
// Copyright 2012 Xamarin, Inc (http://www.xamarin.com)
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
#if NET_4_0
using System.Collections.Generic;
using System.Diagnostics;
namespace System.Threading.Tasks
{
[DebuggerDisplay ("Id={Id}")]
[DebuggerTypeProxy (typeof (TaskSchedulerDebuggerView))]
public abstract class TaskScheduler
{
sealed class TaskSchedulerDebuggerView
{
readonly TaskScheduler scheduler;
public TaskSchedulerDebuggerView (TaskScheduler scheduler)
{
this.scheduler = scheduler;
}
public IEnumerable<Task> ScheduledTasks {
get {
return scheduler.GetScheduledTasks ();
}
}
}
static readonly TaskScheduler defaultScheduler = new TpScheduler ();
[ThreadStatic]
static TaskScheduler currentScheduler;
int id;
static int lastId = int.MinValue;
public static event EventHandler<UnobservedTaskExceptionEventArgs> UnobservedTaskException;
protected TaskScheduler ()
{
this.id = Interlocked.Increment (ref lastId);
}
public static TaskScheduler FromCurrentSynchronizationContext ()
{
var syncCtx = SynchronizationContext.Current;
if (syncCtx == null)
throw new InvalidOperationException ("The current SynchronizationContext is null and cannot be used as a TaskScheduler");
return new SynchronizationContextScheduler (syncCtx);
}
public static TaskScheduler Default {
get {
return defaultScheduler;
}
}
public static TaskScheduler Current {
get {
if (currentScheduler != null)
return currentScheduler;
return defaultScheduler;
}
internal set {
currentScheduler = value;
}
}
public int Id {
get {
return id;
}
}
internal static bool IsDefault {
get {
return currentScheduler == null || currentScheduler == defaultScheduler;
}
}
public virtual int MaximumConcurrencyLevel {
get {
return int.MaxValue;
}
}
protected abstract IEnumerable<Task> GetScheduledTasks ();
protected internal abstract void QueueTask (Task task);
protected internal virtual bool TryDequeue (Task task)
{
return false;
}
internal protected bool TryExecuteTask (Task task)
{
if (task.IsCompleted)
return false;
if (task.Status == TaskStatus.WaitingToRun) {
task.Execute ();
if (task.WaitOnChildren ())
task.Wait ();
return true;
}
return false;
}
protected abstract bool TryExecuteTaskInline (Task task, bool taskWasPreviouslyQueued);
internal bool RunInline (Task task, bool taskWasPreviouslyQueued)
{
if (!TryExecuteTaskInline (task, taskWasPreviouslyQueued))
return false;
if (!task.IsCompleted)
throw new InvalidOperationException ("The TryExecuteTaskInline call to the underlying scheduler succeeded, but the task body was not invoked");
return true;
}
internal static UnobservedTaskExceptionEventArgs FireUnobservedEvent (Task task, AggregateException e)
{
UnobservedTaskExceptionEventArgs args = new UnobservedTaskExceptionEventArgs (e);
EventHandler<UnobservedTaskExceptionEventArgs> temp = UnobservedTaskException;
if (temp == null)
return args;
temp (task, args);
return args;
}
}
}
#endif
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