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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.ComponentModel;
using System.Threading;
namespace System.Reactive.PlatformServices
{
/// <summary>
/// (Infrastructure) Provides access to local system clock services.
/// </summary>
/// <remarks>
/// This type is used by the Rx infrastructure and not meant for public consumption or implementation.
/// No guarantees are made about forward compatibility of the type's functionality and its usage.
/// </remarks>
[EditorBrowsable(EditorBrowsableState.Never)]
public static class SystemClock
{
private static Lazy<ISystemClock> s_serviceSystemClock = new Lazy<ISystemClock>(InitializeSystemClock);
private static Lazy<INotifySystemClockChanged> s_serviceSystemClockChanged = new Lazy<INotifySystemClockChanged>(InitializeSystemClockChanged);
private static int _refCount;
/// <summary>
/// Gets the local system clock time.
/// </summary>
public static DateTimeOffset UtcNow
{
get { return s_serviceSystemClock.Value.UtcNow; }
}
/// <summary>
/// Event that gets raised when a system clock change is detected, if there's any interest as indicated by AddRef calls.
/// </summary>
public static event EventHandler<SystemClockChangedEventArgs> SystemClockChanged;
/// <summary>
/// Adds a reference to the system clock monitor, causing it to be sending notifications.
/// </summary>
/// <exception cref="NotSupportedException">Thrown when the system doesn't support sending clock change notifications.</exception>
public static void AddRef()
{
if (Interlocked.Increment(ref _refCount) == 1)
{
s_serviceSystemClockChanged.Value.SystemClockChanged += OnSystemClockChanged;
}
}
/// <summary>
/// Removes a reference to the system clock monitor, causing it to stop sending notifications
/// if the removed reference was the last one.
/// </summary>
public static void Release()
{
if (Interlocked.Decrement(ref _refCount) == 0)
{
s_serviceSystemClockChanged.Value.SystemClockChanged -= OnSystemClockChanged;
}
}
private static void OnSystemClockChanged(object sender, SystemClockChangedEventArgs e)
{
var scc = SystemClockChanged;
if (scc != null)
scc(sender, e);
}
private static ISystemClock InitializeSystemClock()
{
return PlatformEnlightenmentProvider.Current.GetService<ISystemClock>() ?? new DefaultSystemClock();
}
private static INotifySystemClockChanged InitializeSystemClockChanged()
{
return PlatformEnlightenmentProvider.Current.GetService<INotifySystemClockChanged>() ?? new DefaultSystemClockMonitor();
}
}
/// <summary>
/// (Infrastructure) Provides access to the local system clock.
/// </summary>
/// <remarks>
/// This type is used by the Rx infrastructure and not meant for public consumption or implementation.
/// No guarantees are made about forward compatibility of the type's functionality and its usage.
/// </remarks>
[EditorBrowsable(EditorBrowsableState.Never)]
public interface ISystemClock
{
/// <summary>
/// Gets the current time.
/// </summary>
DateTimeOffset UtcNow { get; }
}
/// <summary>
/// (Infrastructure) Provides a mechanism to notify local schedulers about system clock changes.
/// </summary>
/// <remarks>
/// This type is used by the Rx infrastructure and not meant for public consumption or implementation.
/// No guarantees are made about forward compatibility of the type's functionality and its usage.
/// </remarks>
[EditorBrowsable(EditorBrowsableState.Never)]
public interface INotifySystemClockChanged
{
/// <summary>
/// Event that gets raised when a system clock change is detected.
/// </summary>
event EventHandler<SystemClockChangedEventArgs> SystemClockChanged;
}
/// <summary>
/// (Infrastructure) Event arguments for system clock change notifications.
/// </summary>
/// <remarks>
/// This type is used by the Rx infrastructure and not meant for public consumption or implementation.
/// No guarantees are made about forward compatibility of the type's functionality and its usage.
/// </remarks>
[EditorBrowsable(EditorBrowsableState.Never)]
public class SystemClockChangedEventArgs : EventArgs
{
/// <summary>
/// Creates a new system clock notification object with unknown old and new times.
/// </summary>
public SystemClockChangedEventArgs()
: this(DateTimeOffset.MinValue, DateTimeOffset.MaxValue)
{
}
/// <summary>
/// Creates a new system clock notification object with the specified old and new times.
/// </summary>
/// <param name="oldTime">Time before the system clock changed, or DateTimeOffset.MinValue if not known.</param>
/// <param name="newTime">Time after the system clock changed, or DateTimeOffset.MaxValue if not known.</param>
public SystemClockChangedEventArgs(DateTimeOffset oldTime, DateTimeOffset newTime)
{
OldTime = oldTime;
NewTime = newTime;
}
/// <summary>
/// Gets the time before the system clock changed, or DateTimeOffset.MinValue if not known.
/// </summary>
public DateTimeOffset OldTime { get; private set; }
/// <summary>
/// Gets the time after the system clock changed, or DateTimeOffset.MaxValue if not known.
/// </summary>
public DateTimeOffset NewTime { get; private set; }
}
}
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