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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
using System.Runtime.CompilerServices;
using System.Threading;
using System.Collections.Generic;
namespace System
{
// error CS0436: When building PresentationFramework, the type 'LocalAppContext'
// conflicts with the imported type 'LocalAppContext' in 'PresentationCore
#pragma warning disable 436
internal partial class LocalAppContext
{
private static Dictionary<string, bool> s_switchMap = new Dictionary<string, bool>();
private static readonly object s_syncLock = new object();
private static bool DisableCaching { get; set; }
static LocalAppContext()
{
// Populate the default values of the local app context
AppContextDefaultValues.PopulateDefaultValues();
// Cache the value of the switch that help with testing
DisableCaching = IsSwitchEnabled(@"TestSwitch.LocalAppContext.DisableCaching");
}
public static bool IsSwitchEnabled(string switchName)
{
if (System.AppContext.TryGetSwitch(switchName, out var isEnabledCentrally))
{
// we found the switch, so return whatever value it has
return isEnabledCentrally;
}
// if we could not get the value from the central authority, try the local storage.
return IsSwitchEnabledLocal(switchName);
}
private static bool IsSwitchEnabledLocal(string switchName)
{
// read the value from the set of local defaults
bool isEnabled, isPresent;
lock (s_switchMap)
{
isPresent = s_switchMap.TryGetValue(switchName, out isEnabled);
}
// If the value is in the set of local switches, return the value
if (isPresent)
{
return isEnabled;
}
// if we could not find the switch name, we should return 'false'
// This will preserve the concept of switches been 'off' unless explicitly set to 'on'
return false;
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
internal static bool GetCachedSwitchValue(string switchName, ref int switchValue)
{
if (switchValue < 0) return false;
if (switchValue > 0) return true;
return GetCachedSwitchValueInternal(switchName, ref switchValue);
}
private static bool GetCachedSwitchValueInternal(string switchName, ref int switchValue)
{
if (LocalAppContext.DisableCaching)
{
return LocalAppContext.IsSwitchEnabled(switchName);
}
bool isEnabled = LocalAppContext.IsSwitchEnabled(switchName);
switchValue = isEnabled ? 1 /*true*/ : -1 /*false*/;
return isEnabled;
}
/// <summary>
/// This method is going to be called from the AppContextDefaultValues class when setting up the
/// default values for the switches. !!!! This method is called during the static constructor so it does not
/// take a lock !!!! If you are planning to use this outside of that, please ensure proper locking.
/// </summary>
internal static void DefineSwitchDefault(string switchName, bool initialValue)
{
s_switchMap[switchName] = initialValue;
}
}
#pragma warning restore 436
}
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