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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