netcore/System.Private.CoreLib/shared/System/LocalAppContextSwitches.Common.cs

   1 // Licensed to the .NET Foundation under one or more agreements.
   2 // The .NET Foundation licenses this file to you under the MIT license.
   3 // See the LICENSE file in the project root for more information.
   4
   5 using System.Runtime.CompilerServices;
   6
   7 namespace System
   8 {
   9     // Helper method for local caching of compatibility quirks. Keep this lean and simple - this file is included into
  10     // every framework assembly that implements any compatibility quirks.
  11     internal static partial class LocalAppContextSwitches
  12     {
  13         // Returns value of given switch using provided cache.
  14         [MethodImpl(MethodImplOptions.AggressiveInlining)]
  15         internal static bool GetCachedSwitchValue(string switchName, ref int cachedSwitchValue)
  16         {
  17             // The cached switch value has 3 states: 0 - unknown, 1 - true, -1 - false
  18             if (cachedSwitchValue < 0) return false;
  19             if (cachedSwitchValue > 0) return true;
  20
  21             return GetCachedSwitchValueInternal(switchName, ref cachedSwitchValue);
  22         }
  23
  24         private static bool GetCachedSwitchValueInternal(string switchName, ref int cachedSwitchValue)
  25         {
  26             bool isSwitchEnabled;
  27
  28             bool hasSwitch = AppContext.TryGetSwitch(switchName, out isSwitchEnabled);
  29             if (!hasSwitch)
  30             {
  31                 isSwitchEnabled = GetSwitchDefaultValue(switchName);
  32             }
  33
  34             AppContext.TryGetSwitch(@"TestSwitch.LocalAppContext.DisableCaching", out bool disableCaching);
  35             if (!disableCaching)
  36             {
  37                 cachedSwitchValue = isSwitchEnabled ? 1 /*true*/ : -1 /*false*/;
  38             }
  39
  40             return isSwitchEnabled;
  41         }
  42
  43         // Provides default values for switches if they're not always false by default
  44         private static bool GetSwitchDefaultValue(string switchName)
  45         {
  46             if (switchName == "Switch.System.Runtime.Serialization.SerializationGuard")
  47             {
  48                 return true;
  49             }
  50
  51             return false;
  52         }
  53     }
  54 }