Code:
/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / cdf / src / NetFx40 / System.Xaml.Hosting / System / Xaml / Hosting / XamlHttpHandlerFactory.cs / 1305376 / XamlHttpHandlerFactory.cs
//------------------------------------------------------------ // Copyright (c) Microsoft Corporation. All rights reserved. //----------------------------------------------------------- namespace System.Xaml.Hosting { using System; using System.Web; using System.Web.Hosting; using System.Web.Compilation; using System.CodeDom.Compiler; using System.Collections.Generic; using System.IO; using System.Diagnostics.CodeAnalysis; using System.Reflection; using System.Xaml.Hosting.Configuration; using System.Configuration; using System.Diagnostics; using System.Threading; using System.Net; using System.Runtime; using System.Security; using System.Collections; [SuppressMessage(FxCop.Category.Performance, FxCop.Rule.AvoidUninstantiatedInternalClasses, Justification = "This is instantiated by AspNet.")] sealed class XamlHttpHandlerFactory : IHttpHandlerFactory { public IHttpHandler GetHandler(HttpContext context, string requestType, string url, string pathTranslated) { //Get the "cache pointer" for the virtual path - if does not exist, create a cache pointer //This should happen under global lock PathInfo pathInfo = PathCache.EnsurePathInfo(context.Request.AppRelativeCurrentExecutionFilePath); return pathInfo.GetHandler(context, requestType, url, pathTranslated); } public void ReleaseHandler(IHttpHandler httphandler) { //Check whether the handler was created by an internal factory if (httphandler is HandlerWrapper) { ((HandlerWrapper)(httphandler)).ReleaseWrappedHandler(); } } static object CreateInstance(Type type) { //The handler/factory should have an empty constructor but need not be public return Activator.CreateInstance(type, BindingFlags.CreateInstance | BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance, null, null, null); } static class PathCache { [Fx.Tag.Cache( typeof(PathInfo), Fx.Tag.CacheAttrition.None, Scope = "instance of declaring class", SizeLimit = "unbounded", Timeout = "infinite" )] static Hashtable pathCache = new Hashtable(StringComparer.OrdinalIgnoreCase); static object writeLock = new object(); public static PathInfo EnsurePathInfo(string path) { PathInfo pathInfo = (PathInfo)pathCache[path]; if (pathInfo != null) { return pathInfo; } lock (writeLock) { pathInfo = (PathInfo)pathCache[path]; if (pathInfo != null) { return pathInfo; } if (HostingEnvironment.VirtualPathProvider.FileExists(path)) { pathInfo = new PathInfo(); pathCache.Add(path, pathInfo); return pathInfo; } else { throw FxTrace.Exception.AsError(new HttpException((int)HttpStatusCode.NotFound, SR.ResourceNotFound)); } } } } class HandlerWrapper : IHttpHandler { IHttpHandlerFactory factory; IHttpHandler httpHandler; private HandlerWrapper(IHttpHandler httpHandler, IHttpHandlerFactory factory) { this.httpHandler = httpHandler; this.factory = factory; } public bool IsReusable { get { return httpHandler.IsReusable; } } public static IHttpHandler Create( IHttpHandler httpHandler, IHttpHandlerFactory factory) { if (httpHandler is IHttpAsyncHandler) { return new AsyncHandlerWrapper((IHttpAsyncHandler)httpHandler, factory); } else { return new HandlerWrapper(httpHandler, factory); } } public void ProcessRequest(HttpContext context) { httpHandler.ProcessRequest(context); } public void ReleaseWrappedHandler() { this.factory.ReleaseHandler(httpHandler); } class AsyncHandlerWrapper : HandlerWrapper, IHttpAsyncHandler { //Storing a local copy to avoid unnecessary typecasts during begin/end IHttpAsyncHandler httpAsyncHandler; public AsyncHandlerWrapper(IHttpAsyncHandler httpAsyncHandler, IHttpHandlerFactory factory) : base(httpAsyncHandler, factory) { this.httpAsyncHandler = httpAsyncHandler; } public IAsyncResult BeginProcessRequest(HttpContext context, AsyncCallback cb, object extraData) { return this.httpAsyncHandler.BeginProcessRequest(context, cb, extraData); } public void EndProcessRequest(IAsyncResult result) { this.httpAsyncHandler.EndProcessRequest(result); } } } class PathInfo { object cachedResult; Type hostedXamlType; object writeLock; public PathInfo() { this.writeLock = new object(); } [Fx.Tag.Throws(typeof(ConfigurationErrorsException), "Invalid Configuration.")] public IHttpHandler GetHandler(HttpContext context, string requestType, string url, string pathTranslated) { if (this.cachedResult == null) { //Cache won't be available if it is invoked first time //Use a local "lock" specifically for this url lock (this.writeLock) { if (this.cachedResult == null) { return GetHandlerFirstTime(context, requestType, url, pathTranslated); } } } return GetHandlerSubSequent(context, requestType, url, pathTranslated); } [Fx.Tag.SecurityNote(Critical = "Uses SecurityCritical method UnsafeImpersonate to establish the impersonation context", Safe = "Does not leak anything, does not let caller influence impersonation.")] // Why this triple try blocks instead of using "using" statement: // 1. "using" will do the impersonation prior to entering the try, // which leaves an opertunity to Thread.Abort this thread and get it to exit the method still impersonated. // 2. put the assignment of unsafeImpersonate in a finally block // in order to prevent Threat.Abort after impersonation but before the assignment. // 3. the finally of a "using" doesn't run until exception filters higher up the stack have executed. // they will do so in the impersonated context if an exception is thrown inside the try. // In sumary, this should prevent the thread from existing this method well still impersonated. Type GetCompiledCustomString(string normalizedVirtualPath) { try { IDisposable unsafeImpersonate = null; try { try { } finally { unsafeImpersonate = HostingEnvironmentWrapper.UnsafeImpersonate(); } return BuildManager.GetCompiledType(normalizedVirtualPath); } finally { if (null != unsafeImpersonate) { unsafeImpersonate.Dispose(); } } } catch { throw; } } //This function is invoked the first time a request is made to XAMLx file //It caches url as key and one of the //following 4 as value -> "Handler/Factory/HandlerCLRType/Exception" IHttpHandler GetHandlerFirstTime(HttpContext context, string requestType, string url, string pathTranslated) { Type httpHandlerType; ConfigurationErrorsException configException; //GetCompiledType is costly - invoke it just once. //This null check is required for "error after GetCompiledType on first attempt" cases only if (this.hostedXamlType == null) { this.hostedXamlType = GetCompiledCustomString(context.Request.AppRelativeCurrentExecutionFilePath); } if (XamlHostingConfiguration.TryGetHttpHandlerType(url, this.hostedXamlType, out httpHandlerType)) { if (TD.HttpHandlerPickedForUrlIsEnabled()) { TD.HttpHandlerPickedForUrl(url, hostedXamlType.FullName, httpHandlerType.FullName); } if (typeof(IHttpHandler).IsAssignableFrom(httpHandlerType)) { IHttpHandler handler = (IHttpHandler)CreateInstance(httpHandlerType); if (handler.IsReusable) { this.cachedResult = handler; } else { this.cachedResult = httpHandlerType; } return handler; } else if (typeof(IHttpHandlerFactory).IsAssignableFrom(httpHandlerType)) { IHttpHandlerFactory factory = (IHttpHandlerFactory)CreateInstance(httpHandlerType); this.cachedResult = factory; IHttpHandler handler = factory.GetHandler(context, requestType, url, pathTranslated); return HandlerWrapper.Create(handler, factory); } else { configException = new ConfigurationErrorsException(SR.NotHttpHandlerType(url, this.hostedXamlType, httpHandlerType.FullName)); this.cachedResult = configException; throw FxTrace.Exception.AsError(configException); } } configException = new ConfigurationErrorsException(SR.HttpHandlerForXamlTypeNotFound(url, this.hostedXamlType, XamlHostingConfiguration.XamlHostingSection)); this.cachedResult = configException; throw FxTrace.Exception.AsError(configException); } //This function retrievs the cached object and uses it to get handler or exception IHttpHandler GetHandlerSubSequent(HttpContext context, string requestType, string url, string pathTranslated) { if (this.cachedResult is IHttpHandler) { return ((IHttpHandler)this.cachedResult); } else if (this.cachedResult is IHttpHandlerFactory) { IHttpHandlerFactory factory = ((IHttpHandlerFactory)this.cachedResult); IHttpHandler handler = factory.GetHandler(context, requestType, url, pathTranslated); return HandlerWrapper.Create(handler, factory); } else if (this.cachedResult is Type) { return (IHttpHandler)CreateInstance((Type)this.cachedResult); } else { throw FxTrace.Exception.AsError((ConfigurationErrorsException)this.cachedResult); } } } } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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