HostExecutionContextManager.cs source code in C# .NET

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Code:

                         / DotNET / DotNET / 8.0 / untmp / whidbey / REDBITS / ndp / clr / src / BCL / System / Threading / HostExecutionContextManager.cs / 1 / 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; 
			// check if we are hosted 
			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")); 
            } 
 		
			// check Undo is happening on the correct thread 
 			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 check if we are hosted and revert the context in the host
            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; 
 		}		
 	}
}

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