Code:
/ DotNET / DotNET / 8.0 / untmp / whidbey / REDBITS / ndp / fx / src / xsp / System / Web / Configuration / HttpCapabilitiesEvaluator.cs / 1 / HttpCapabilitiesEvaluator.cs
//------------------------------------------------------------------------------ //// Copyright (c) Microsoft Corporation. All rights reserved. // //----------------------------------------------------------------------------- namespace System.Web.Configuration { using System.Collections; using System.Collections.Specialized; using System.Diagnostics; using System.Globalization; using System.Reflection; using System.Security; using System.Text; using System.Text.RegularExpressions; using System.Threading; using System.Web.Caching; using System.Web.Compilation; using System.Web.Hosting; using System.Security.Permissions; // // CapabilitiesEvaluator encapabilitiesulates a set of rules for deducing // a capabilities object from an HttpRequest // internal class HttpCapabilitiesEvaluator { internal CapabilitiesRule _rule; internal Hashtable _variables; internal Type _resultType; internal TimeSpan _cachetime; internal string _cacheKeyPrefix; private int _userAgentCacheKeyLength; private static int _idCounter; private const string _isMobileDeviceCapKey = "isMobileDevice"; private static object _disableOptimisticCachingSingleton = new object(); internal int UserAgentCacheKeyLength { get { return _userAgentCacheKeyLength; } set { _userAgentCacheKeyLength = value; } } // // internal constructor; inherit from parent // internal HttpCapabilitiesEvaluator(HttpCapabilitiesEvaluator parent) { int id = Interlocked.Increment(ref _idCounter); // don't do id.ToString() on every request, do it here _cacheKeyPrefix = CacheInternal.PrefixHttpCapabilities + id.ToString(CultureInfo.InvariantCulture); if (parent == null) { ClearParent(); } else { _rule = parent._rule; if (parent._variables == null) _variables = null; else _variables = new Hashtable(parent._variables); _cachetime = parent._cachetime; _resultType = parent._resultType; } // AddDependency(String.Empty); } internal BrowserCapabilitiesFactoryBase BrowserCapFactory { get { return BrowserCapabilitiesCompiler.BrowserCapabilitiesFactory; } } // // remove inheritance for// internal virtual void ClearParent() { _rule = null; _cachetime = TimeSpan.FromSeconds(60); // one minute default expiry _variables = new Hashtable(); _resultType = typeof(HttpCapabilitiesBase); } // // set // internal virtual void SetCacheTime(int sec) { _cachetime = TimeSpan.FromSeconds(sec); } // // add a dependency when we encounter a // internal virtual void AddDependency(String variable) { if (variable.Equals("HTTP_USER_AGENT")) variable = String.Empty; _variables[variable] = true; } // // sets the set of rules // internal virtual void AddRuleList(ArrayList rulelist) { if (rulelist.Count == 0) return; if (_rule != null) rulelist.Insert(0, _rule); _rule = new CapabilitiesSection(CapabilitiesRule.Filter, null, null, rulelist); } internal static string GetUserAgent(HttpRequest request) { string userAgent; if (request.ClientTarget.Length > 0) { userAgent = GetUserAgentFromClientTarget( request.Context.ConfigurationPath, request.ClientTarget); } else { userAgent = request.UserAgent; } // Protect against attacks with long User-Agent headers if (userAgent != null && userAgent.Length > 256) { userAgent = userAgent.Substring(0, 256); } return userAgent; } internal static string GetUserAgentFromClientTarget(VirtualPath configPath, string clientTarget) { // Lookup ClientTarget section in config. ClientTargetSection clientTargetConfig = RuntimeConfig.GetConfig(configPath).ClientTarget; string userAgent = null; if ( clientTargetConfig.ClientTargets[ clientTarget ] != null ) { userAgent = clientTargetConfig.ClientTargets[ clientTarget ].UserAgent; } if ( userAgent == null ) { throw new HttpException(SR.GetString(SR.Invalid_client_target, clientTarget)); } return userAgent; } private void CacheBrowserCapResult(ref HttpCapabilitiesBase result) { // Use the previously cached browserCap object if an identical // browserCap is found. CacheInternal cacheInternal = System.Web.HttpRuntime.CacheInternal; if (result.Capabilities == null) { return; } string hashKey = CacheInternal.PrefixBrowserCapsHash; StringBuilder builder = new StringBuilder(); foreach (string attribute in result.Capabilities.Keys) { // Ignore useragent that is stored with empty key. if (String.IsNullOrEmpty(attribute)) { continue; } string value = (String)result.Capabilities[attribute]; if (value != null) { builder.Append(attribute); builder.Append("$"); builder.Append(value); builder.Append("$"); } } hashKey += builder.ToString().GetHashCode().ToString(CultureInfo.InvariantCulture); HttpCapabilitiesBase newResult = cacheInternal.Get(hashKey) as HttpCapabilitiesBase; if (newResult != null) { result = newResult; } else { cacheInternal.UtcInsert(hashKey, result); } } // // Actually computes the browser capabilities // internal HttpCapabilitiesBase Evaluate(HttpRequest request) { HttpCapabilitiesBase result; CacheInternal cacheInternal = System.Web.HttpRuntime.CacheInternal; // // 1) grab UA and do optimistic cache lookup (if UA is in dependency list) // string userAgent = GetUserAgent(request); string userAgentCacheKey = userAgent; // Use the shorten userAgent as the cache key. Debug.Assert(UserAgentCacheKeyLength != 0); // Trim the useragent string based on config if (userAgentCacheKey != null && userAgentCacheKey.Length > UserAgentCacheKeyLength) { userAgentCacheKey = userAgentCacheKey.Substring(0, UserAgentCacheKeyLength); } bool doFullCacheKeyLookup = false; string optimisticCacheKey = _cacheKeyPrefix + userAgentCacheKey; object optimisticCacheResult = cacheInternal.Get(optimisticCacheKey); // optimize for common case (desktop browser) result = optimisticCacheResult as HttpCapabilitiesBase; if (result != null) { return result; } // // 1.1) optimistic cache entry could tell us to do full cache lookup // if (optimisticCacheResult == _disableOptimisticCachingSingleton) { doFullCacheKeyLookup = true; } else { // cache it and respect _cachetime result = EvaluateFinal(request, true); // Optimized cache key is disabled if the request matches any headers defined within identifications. if (result.UseOptimizedCacheKey) { // Use the same browserCap result if one with the same capabilities can be found in the cache. // This is to reduce the number of identical browserCap instances being cached. CacheBrowserCapResult(ref result); // Cache the result using the optimisicCacheKey cacheInternal.UtcInsert(optimisticCacheKey, result, null, Cache.NoAbsoluteExpiration, _cachetime); return result; } } // // 2) either: // // We've never seen the UA before (parse all headers to // determine if the new UA also carries modile device // httpheaders). // // It's a mobile UA (so parse all headers) and do full // cache lookup // // UA isn't in dependency list (customer custom caps section) // IDictionaryEnumerator de = _variables.GetEnumerator(); StringBuilder sb = new StringBuilder(_cacheKeyPrefix); InternalSecurityPermissions.AspNetHostingPermissionLevelLow.Assert(); while (de.MoveNext()) { string key = (string)de.Key; string value; if (key.Length == 0) { value = userAgent; } else { value = request.ServerVariables[key]; } if (value != null) { sb.Append(value); } } CodeAccessPermission.RevertAssert(); sb.Append(BrowserCapabilitiesFactoryBase.GetBrowserCapKey(BrowserCapFactory.InternalGetMatchedHeaders(), request)); string fullCacheKey = sb.ToString(); // // Only do full cache lookup if the optimistic cache // result was _disableOptimisticCachingSingleton or // if UserAgent wasn't in the cap var list. // if (userAgent == null || doFullCacheKeyLookup) { result = cacheInternal.Get(fullCacheKey) as HttpCapabilitiesBase; if (result != null) return result; } result = EvaluateFinal(request, false); // Use the same browserCap result if one with the same matched nodes can be found in the cache. // This is to reduce the number of identical browserCap instances being cached. CacheBrowserCapResult(ref result); // cache it and respect _cachetime cacheInternal.UtcInsert(fullCacheKey, result, null, Cache.NoAbsoluteExpiration, _cachetime); if(optimisticCacheKey != null) { cacheInternal.UtcInsert(optimisticCacheKey, _disableOptimisticCachingSingleton, null, Cache.NoAbsoluteExpiration, _cachetime); } return result; } internal HttpCapabilitiesBase EvaluateFinal(HttpRequest request, bool onlyEvaluateUserAgent) { HttpBrowserCapabilities browserCaps = BrowserCapFactory.GetHttpBrowserCapabilities(request); CapabilitiesState state = new CapabilitiesState(request, browserCaps.Capabilities); if (onlyEvaluateUserAgent) { state.EvaluateOnlyUserAgent = true; } if(_rule != null) { string oldIsMobileDevice = browserCaps[_isMobileDeviceCapKey]; browserCaps.Capabilities[_isMobileDeviceCapKey] = null; _rule.Evaluate(state); string newIsMobileDevice = browserCaps[_isMobileDeviceCapKey]; if (newIsMobileDevice == null) { browserCaps.Capabilities[_isMobileDeviceCapKey] = oldIsMobileDevice; } else if (newIsMobileDevice.Equals("true")) { browserCaps.DisableOptimizedCacheKey(); } } // create the new type // HttpCapabilitiesBase result = (HttpCapabilitiesBase)HttpRuntime.CreateNonPublicInstance(_resultType); result.InitInternal(browserCaps); return result; } } }
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