HostExecutionContextManager.cs source code in C# .NET

                        Code:
                         / FXUpdate3074 / FXUpdate3074 / 1.1 / untmp / whidbey / QFE / ndp / clr / src / BCL / System / Threading / HostExecutionContextManager.cs / 3 / HostExecutionContextManager.cs
                        
                        
                            // ==++== 
//
//   Copyright (c) Microsoft Corporation.  All rights reserved.
//
/*============================================================ 
**
** Class:  ExecutionContext 
** 
**
** Purpose: Capture Host execution  context for a thread 
**
**
===========================================================*/
namespace System.Threading 
{
    using System.Security; 
   using System.Runtime.Remoting; 
   using System.Runtime.CompilerServices;
   using System.Runtime.Serialization; 
    using System.Security.Permissions;
   using System.Runtime.Remoting.Contexts;
    using System.Runtime.Remoting.Messaging;
       using System.Runtime.ConstrainedExecution; 
    using System.Runtime.InteropServices;
 
 

   internal class HostExecutionContextSwitcher 
    {
      internal ExecutionContext        executionContext;
      internal HostExecutionContext    previousHostContext;
      internal HostExecutionContext    currentHostContext; 

       [ReliabilityContract(Consistency.WillNotCorruptState, Cer.MayFail)] 
      static public void Undo(Object switcherObject) 
       {
          if (switcherObject == null) 
               return;
         // otherwise call the host
          HostExecutionContextManager hostMgr = HostExecutionContextManager.GetCurrentHostExecutionContextManager();
         if (hostMgr != null) 
         {
            hostMgr.Revert(switcherObject); 
          } 
      }
    } 
 


   public class HostExecutionContext 
    {
      private Object state; 
 
      protected internal Object State {
           get { 
              return state;
           }
           set {
              state = value; 
           }
      } 
 
      public HostExecutionContext()
       { 
      }

       public HostExecutionContext(Object state)
       { 
         this.state = state;
       } 
 
      public virtual HostExecutionContext CreateCopy()
      { 
                     Object newState = state;
         if (state is IUnknownSafeHandle)
          {
                            // Clone the IUnknown handle 
                            newState = ((IUnknownSafeHandle)state).Clone();
         } 
          return new HostExecutionContext(state); 
       }
   } 

    internal class IUnknownSafeHandle : SafeHandle
   {
      public IUnknownSafeHandle() : base(IntPtr.Zero, true) 
      {
       } 
 
      public override bool IsInvalid {
                   get { return handle == IntPtr.Zero; } 
          }

       override protected bool ReleaseHandle()
      { 
          HostExecutionContextManager.ReleaseHostSecurityContext(this.handle);
         return true; 
      } 

             internal Object Clone() 
             {
                IUnknownSafeHandle unkSafeHandleCloned = new IUnknownSafeHandle();
                // call into the Hosting API to CLONE the host context
                // stores the output IUnknown in the safehandle, 
                if (!IsInvalid)
                { 
                    HostExecutionContextManager.CloneHostSecurityContext(this, unkSafeHandleCloned); 
                }
                return unkSafeHandleCloned; 
             }
   }

 

    public class HostExecutionContextManager 
   { 
       private static bool           _fIsHostedChecked;
       private static bool           _fIsHosted; 
      private static HostExecutionContextManager _hostExecutionContextManager;

              [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
              [MethodImplAttribute(MethodImplOptions.InternalCall)] 
         static private extern bool HostSecurityManagerPresent();
 
              [MethodImplAttribute(MethodImplOptions.InternalCall)] 
       static internal extern int ReleaseHostSecurityContext(IntPtr context);
 
              [MethodImplAttribute(MethodImplOptions.InternalCall)]
      static internal extern int CloneHostSecurityContext(SafeHandle context, SafeHandle clonedContext);

      [MethodImplAttribute(MethodImplOptions.InternalCall)] 
      static private extern int CaptureHostSecurityContext(SafeHandle capturedContext);
 
              [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)] 
       [MethodImplAttribute(MethodImplOptions.InternalCall)]
      static private extern int SetHostSecurityContext(SafeHandle context, bool fReturnPrevious, SafeHandle prevContext); 

       internal static bool CheckIfHosted()
       {
         if (!_fIsHostedChecked) 
          {
            _fIsHosted = HostSecurityManagerPresent(); 
            _fIsHostedChecked = true; 
         }
          return _fIsHosted; 
      }
 
        // capture Host SecurityContext
      public virtual  HostExecutionContext Capture() 
       {
         HostExecutionContext context =  null; 
         // 
         if (CheckIfHosted())
          { 
            IUnknownSafeHandle unkSafeHandle = new IUnknownSafeHandle();
                            context = new HostExecutionContext(unkSafeHandle);

             // call into the Hosting API to capture the host context 
             // stores the output IUnknown in the safehandle,
            CaptureHostSecurityContext(unkSafeHandle); 
          } 

         // otherwise 
         return context;

       }
      // Set Host SecurityContext 
       [SecurityPermissionAttribute(SecurityAction.LinkDemand, Flags=SecurityPermissionFlag.Infrastructure)]
       public virtual Object SetHostExecutionContext(HostExecutionContext hostExecutionContext) 
      { 
            if (hostExecutionContext == null)
            { 
                throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_NotNewCaptureContext"));
            }
 
         HostExecutionContextSwitcher switcher = new HostExecutionContextSwitcher(); 
                     ExecutionContext currentExecutionContext = Thread.CurrentThread.ExecutionContext;
 
         switcher.executionContext = currentExecutionContext; 
         switcher.currentHostContext = hostExecutionContext;
                     switcher.previousHostContext = null; 

          if (CheckIfHosted())
         {
             if (hostExecutionContext.State is IUnknownSafeHandle) 
             {
                                    // setup the previous unknown handle 
                                   IUnknownSafeHandle unkPrevSafeHandle = new IUnknownSafeHandle(); 
                        switcher.previousHostContext = new HostExecutionContext(unkPrevSafeHandle);
 
                                    // get the current handle
               IUnknownSafeHandle unkSafeHandle  = (IUnknownSafeHandle)hostExecutionContext.State;

                                   // call into the Hosting API to set the host context 
                                   // second arg indicates whether we want to retrieve the previous context
                   SetHostSecurityContext(unkSafeHandle,true,unkPrevSafeHandle); 
            } 
         }
 
                    // store the current HostExecutionContext in the ExecutionContext.
         currentExecutionContext.HostExecutionContext = hostExecutionContext;
 
         return switcher; 
       }
 
       // this method needs to be reliable 
      [SecurityPermissionAttribute(SecurityAction.LinkDemand, Flags=SecurityPermissionFlag.Infrastructure),
        ReliabilityContract(Consistency.WillNotCorruptState, Cer.MayFail)] 
      public virtual void Revert(Object previousState)
      {
          HostExecutionContextSwitcher hostContextSwitcher = previousState as HostExecutionContextSwitcher;
            if (hostContextSwitcher == null) 
            {
                throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_CannotOverrideSetWithoutRevert")); 
            } 
 
         // 
          ExecutionContext executionContext = Thread.CurrentThread.ExecutionContext;
 
         if (executionContext != hostContextSwitcher.executionContext)
          { 
             throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_CannotUseSwitcherOtherThread"));
         } 
            hostContextSwitcher.executionContext = null; // Make sure switcher cannot be re-used. 

            HostExecutionContext revertFromHostContext = executionContext.HostExecutionContext; 
         // if the current host context is not the same as the one in the switcher, then revert is being called out of order
          if (revertFromHostContext != hostContextSwitcher.currentHostContext)
         {
              throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_CannotUseSwitcherOtherThread")); 
          }
 
         // get the previous host context 
          HostExecutionContext revertToHostContext = hostContextSwitcher.previousHostContext;
 
            // now
            if (CheckIfHosted())
            {
                // try restore the previous context as the current context 
                if (revertToHostContext != null && revertToHostContext.State is IUnknownSafeHandle)
                { 
                    IUnknownSafeHandle unkprevSafeHandle = (IUnknownSafeHandle)revertToHostContext.State; 
                    // call into the Hosting API to set the host context
                    SetHostSecurityContext(unkprevSafeHandle, false, null); 
                }
            }

            //restore the previous host context in the executioncontext 
            executionContext.HostExecutionContext = revertToHostContext;
 
        } 

      internal static HostExecutionContext CaptureHostExecutionContext() 
      {
         HostExecutionContext hostContext = null;
           // capture the host execution context
             HostExecutionContextManager hostMgr = HostExecutionContextManager.GetCurrentHostExecutionContextManager(); 
                if (hostMgr != null)
                  { 
                     hostContext = hostMgr.Capture(); 
            }
         return hostContext; 
       }

        internal static Object SetHostExecutionContextInternal(HostExecutionContext hostContext)
        { 
            HostExecutionContextManager hostMgr = HostExecutionContextManager.GetCurrentHostExecutionContextManager();
            Object switcher = null; 
            if (hostMgr != null) 
            {
                switcher = hostMgr.SetHostExecutionContext(hostContext); 
                //
            }
            return switcher;
        } 

              // retun the HostExecutionContextManager for the current AppDomain 
        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)] 
       internal static HostExecutionContextManager GetCurrentHostExecutionContextManager()
      { 
          // this is called during AppDomainManager initialization, this is a thread safe place
         // to setup the HostExecutionContextManager for the current AppDomain
         if (AppDomainManager.CurrentAppDomainManager != null) {
 
             return AppDomainManager.CurrentAppDomainManager.HostExecutionContextManager;
         } 
            return null; 
       }
 
              // retun the HostExecutionContextManager for the current AppDomain
       internal static HostExecutionContextManager GetInternalHostExecutionContextManager()
      {
          if (_hostExecutionContextManager == null) { 
            // setup the HostExecutionContextManager for the current AppDomain
            BCLDebug.Assert(_hostExecutionContextManager == null, "HostExecutionContextManager should be null"); 
            _hostExecutionContextManager = new HostExecutionContextManager(); 
          }
         return _hostExecutionContextManager; 
       }
    }
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.
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