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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;
#if !NO_WEAKTABLE
using System.Runtime.CompilerServices;
#endif
namespace System.Reactive.Concurrency
{
internal abstract class SchedulerWrapper : IScheduler, IServiceProvider
{
protected readonly IScheduler _scheduler;
public SchedulerWrapper(IScheduler scheduler)
{
_scheduler = scheduler;
#if !NO_WEAKTABLE
_cache = new ConditionalWeakTable<IScheduler, IScheduler>();
#endif
}
public DateTimeOffset Now
{
get { return _scheduler.Now; }
}
public IDisposable Schedule<TState>(TState state, Func<IScheduler, TState, IDisposable> action)
{
if (action == null)
throw new ArgumentNullException("action");
return _scheduler.Schedule(state, Wrap(action));
}
public IDisposable Schedule<TState>(TState state, TimeSpan dueTime, Func<IScheduler, TState, IDisposable> action)
{
if (action == null)
throw new ArgumentNullException("action");
return _scheduler.Schedule(state, dueTime, Wrap(action));
}
public IDisposable Schedule<TState>(TState state, DateTimeOffset dueTime, Func<IScheduler, TState, IDisposable> action)
{
if (action == null)
throw new ArgumentNullException("action");
return _scheduler.Schedule(state, dueTime, Wrap(action));
}
protected virtual Func<IScheduler, TState, IDisposable> Wrap<TState>(Func<IScheduler, TState, IDisposable> action)
{
return (self, state) => action(GetRecursiveWrapper(self), state);
}
#if !NO_WEAKTABLE
private readonly ConditionalWeakTable<IScheduler, IScheduler> _cache;
public SchedulerWrapper(IScheduler scheduler, ConditionalWeakTable<IScheduler, IScheduler> cache)
{
_scheduler = scheduler;
_cache = cache;
}
protected IScheduler GetRecursiveWrapper(IScheduler scheduler)
{
return _cache.GetValue(scheduler, s => Clone(s, _cache));
}
protected abstract SchedulerWrapper Clone(IScheduler scheduler, ConditionalWeakTable<IScheduler, IScheduler> cache);
#else
private readonly object _gate = new object();
private IScheduler _recursiveOriginal;
private IScheduler _recursiveWrapper;
protected IScheduler GetRecursiveWrapper(IScheduler scheduler)
{
var recursiveWrapper = default(IScheduler);
lock (_gate)
{
//
// Chances are the recursive scheduler will remain the same. In practice, this
// single-shot caching scheme works out quite well. Notice we propagate our
// mini-cache to recursive raw scheduler wrappers too.
//
if (!object.ReferenceEquals(scheduler, _recursiveOriginal))
{
_recursiveOriginal = scheduler;
var wrapper = Clone(scheduler);
wrapper._recursiveOriginal = scheduler;
wrapper._recursiveWrapper = wrapper;
_recursiveWrapper = wrapper;
}
recursiveWrapper = _recursiveWrapper;
}
return recursiveWrapper;
}
protected abstract SchedulerWrapper Clone(IScheduler scheduler);
#endif
public object GetService(Type serviceType)
{
var serviceProvider = _scheduler as IServiceProvider;
if (serviceProvider == null)
return null;
var result = default(object);
if (TryGetService(serviceProvider, serviceType, out result))
return result;
return serviceProvider.GetService(serviceType);
}
protected abstract bool TryGetService(IServiceProvider provider, Type serviceType, out object service);
}
}
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