PackWebRequestFactory.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / wpf / src / Core / CSharp / System / IO / Packaging / PackWebRequestFactory.cs / 1305600 / PackWebRequestFactory.cs
                        

                        
                            //------------------------------------------------------------------------------ 
//
// 
//    Copyright (C) Microsoft Corporation.  All rights reserved.
//  
//
// Description: 
//  Creates a PackWebRequest object 
//
// History: 
//  10/09/2003: BruceMac: Created.
//  05/10/2004: BruceMac: Rework for Pack scheme (from CompoundFile scheme)
//  05/26/2004: BruceMac: Use ILoader cache instead of PackageCache
//  04/26/2005: BruceMac: Use PackUriHelper to obtain Authority for cache lookup 
//
//----------------------------------------------------------------------------- 
 
#if DEBUG
#define TRACE 
#endif

using System;
using System.Net; 
using System.Diagnostics;               // for Assert
using MS.Internal.IO.Packaging;         // for PackageCache 
using MS.Internal.PresentationCore;     // for ExceptionStringTable 
using System.Security;
using System.Security.Permissions; 
using MS.Internal;

namespace System.IO.Packaging
{ 
    /// 
    /// Invoked by .NET framework when our schema is recognized during a WebRequest 
    ///  
    public sealed class PackWebRequestFactory : IWebRequestCreate
    { 
        /// 
        /// Critical as the BooleanSwitch has a LinkDemand
        /// TreatAsSafe as this is just a diag switch, Debug-only, no input data is used,
        ///   and the usage is considered safe (tracing). 
        /// 
        [SecurityCritical, SecurityTreatAsSafe] 
        static PackWebRequestFactory() 
        {
#if DEBUG 
            _traceSwitch = new BooleanSwitch("PackWebRequest", "PackWebRequest/Response and NetStream trace messages");
#endif
        }
 
        //-----------------------------------------------------
        // 
        //  IWebRequestCreate 
        //
        //----------------------------------------------------- 
        /// 
        /// Create
        /// 
        /// uri 
        /// PackWebRequest
        /// Note that this factory may or may not be "registered" with the .NET WebRequest factory as handler 
        /// for "pack" scheme web requests.  Because of this, callers should be sure to use the PackUriHelper static class 
        /// to prepare their Uri's.  Calling any PackUriHelper method has the side effect of registering
        /// the "pack" scheme and associating this factory class as its default handler. 
        /// 
        /// Critical: Access a package instance from PreloadedPackages.
        /// TreatAsSafe: because it is a public method and no Package related objects
        ///         are given out from this API other than a part stream 
        /// 
        [SecurityCritical, SecurityTreatAsSafe] 
        WebRequest IWebRequestCreate.Create(Uri uri) 
        {
            if (uri == null) 
                throw new ArgumentNullException("uri");

            // Ensure uri is absolute - if we don't check now, the get_Scheme property will throw
            // InvalidOperationException which would be misleading to the caller. 
            if (!uri.IsAbsoluteUri)
                throw new ArgumentException(SR.Get(SRID.UriMustBeAbsolute), "uri"); 
 
            // Ensure uri is correct scheme because we can be called directly.  Case sensitive
            // is fine because Uri.Scheme contract is to return in lower case only. 
            if (String.Compare(uri.Scheme, PackUriHelper.UriSchemePack, StringComparison.Ordinal) != 0)
                throw new ArgumentException(SR.Get(SRID.UriSchemeMismatch, PackUriHelper.UriSchemePack), "uri");

#if DEBUG 
            if (_traceSwitch.Enabled)
                System.Diagnostics.Trace.TraceInformation( 
                        DateTime.Now.ToLongTimeString() + " " + DateTime.Now.Millisecond + " " + 
                        System.Threading.Thread.CurrentThread.ManagedThreadId + ": " +
                        "PackWebRequestFactory - responding to uri: " + uri); 
#endif
            // only inspect cache if part name is present because cache only contains an object, not
            // the stream it was derived from
            Uri packageUri; 
            Uri partUri;
            PackUriHelper.ValidateAndGetPackUriComponents(uri, out packageUri, out partUri); 
 
            if (partUri != null)
            { 
                // Note: we look at PreloadedPackages first before we examine the PackageStore
                //  This is to make sure that an app cannot override any predefine packages

                // match cached object by authority component only - ignore the local path (part name) 
                // inspect local package cache and default to that if possible
 
                // All predefined packages such as a package activated by DocumentApplication, 
                //  ResourceContainer, and SiteOfOriginContainer are placed in PreloadedPackages
                bool cachedPackageIsThreadSafe; 
                Package c = PreloadedPackages.GetPackage(packageUri, out cachedPackageIsThreadSafe);

                // If we don't find anything in the preloaded packages, look into the PackageStore
                bool cachedPackageIsFromPublicStore = false; 
                if (c == null)
                { 
                    cachedPackageIsThreadSafe = false;          // always assume PackageStore packages are not thread-safe 
                    cachedPackageIsFromPublicStore = true;
 
                    // Try to get a package from the package store
                    c = PackageStore.GetPackage(packageUri);
                }
 
                // do we have a package?
                if (c != null) 
                { 
#if DEBUG
                    if (_traceSwitch.Enabled) 
                        System.Diagnostics.Trace.TraceInformation(
                                DateTime.Now.ToLongTimeString() + " " + DateTime.Now.Millisecond + " " +
                                System.Threading.Thread.CurrentThread.ManagedThreadId + ": " +
                                "PackWebRequestFactory - cache hit - returning CachedPackWebRequest"); 
#endif
                    // use the cached object 
                    return new PackWebRequest(uri, packageUri, partUri, c, 
                        cachedPackageIsFromPublicStore, cachedPackageIsThreadSafe);
                } 

            }

#if DEBUG 
            if (_traceSwitch.Enabled)
                System.Diagnostics.Trace.TraceInformation( 
                        DateTime.Now.ToLongTimeString() + " " + DateTime.Now.Millisecond + " " + 
                        System.Threading.Thread.CurrentThread.ManagedThreadId + ": " +
                        "PackWebRequestFactory - spawning regular PackWebRequest"); 
#endif
            return new PackWebRequest(uri, packageUri, partUri);
        }
 
        //------------------------------------------------------
        // 
        //  Internal Methods 
        //
        //----------------------------------------------------- 

        // CreateWebRequest: Explicitly calls Create on PackWebRequest if uri is pack scheme
        // Ideally we would want to use RegisterPrefix and WebRequest.Create.
        // However, these two functions regress 700k working set in System.dll and System.xml.dll 
        //  which is mostly for logging and config.
        // This helper function provides a way to bypass the regression 
        [FriendAccessAllowed] 
        internal static WebRequest CreateWebRequest(Uri uri)
        { 
            if (String.Compare(uri.Scheme, PackUriHelper.UriSchemePack, StringComparison.Ordinal) == 0)
            {
                return ((IWebRequestCreate) _factorySingleton).Create(uri);
            } 
            else
            { 
                return WpfWebRequestHelper.CreateRequest(uri); 
            }
        } 

#if DEBUG
        ///
        ///     Critical: sets BooleanSwitch.Enabled which LinkDemands 
        ///     TreatAsSafe: ok to enable tracing, and it's in debug only
        /// 
        internal static bool TraceSwitchEnabled 
        {
            get 
            {
                return _traceSwitch.Enabled;
            }
 
            [SecurityCritical, SecurityTreatAsSafe]
            set 
            { 
                _traceSwitch.Enabled = value;
            } 
        }

        internal static System.Diagnostics.BooleanSwitch _traceSwitch;
#endif 

        //------------------------------------------------------ 
        // 
        //  Private Members
        // 
        //------------------------------------------------------
        private static PackWebRequestFactory _factorySingleton = new PackWebRequestFactory();
    }
} 

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

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