Imported Upstream version 3.6.0

Former-commit-id: da6be194a6b1221998fc28233f2503bd61dd9d14

external/aspnetwebstack/src/System.Web.WebPages/BrowserHelpers.cs

@@ -0,0 +1,170 @@
+// Copyright (c) Microsoft Corporation. All rights reserved. See License.txt in the project root for license information.
+
+using System.Web.Hosting;
+
+namespace System.Web.WebPages
+{
+    /// <summary>
+    /// Extension methods used to determine what browser a visitor wants to be seen as using.
+    /// </summary>
+    public static class BrowserHelpers
+    {
+        /// <summary>
+        /// Stock IE6 user agent string
+        /// </summary>
+        private const string DesktopUserAgent = "Mozilla/4.0 (compatible; MSIE 6.1; Windows XP)";
+
+        /// <summary>
+        /// Stock Windows Mobile 6.0 user agent string
+        /// </summary>
+        private const string MobileUserAgent = "Mozilla/4.0 (compatible; MSIE 6.0; Windows CE; IEMobile 8.12; MSIEMobile 6.0)";
+
+        private static readonly object _browserOverrideKey = new object();
+        private static readonly object _userAgentKey = new object();
+
+        /// <summary>
+        /// Clears the set browser for the request. After clearing the browser the overridden browser will be the browser for the request.
+        /// </summary>
+        public static void ClearOverriddenBrowser(this HttpContextBase httpContext)
+        {
+            SetOverriddenBrowser(httpContext, userAgent: null);
+        }
+
+        // Default implementation to generate an HttpBrowserCapabilities object using the current HttpCapabilitiesProvider
+        private static HttpBrowserCapabilitiesBase CreateOverriddenBrowser(string userAgent)
+        {
+            HttpBrowserCapabilities overriddenBrowser = new HttpContext(new UserAgentWorkerRequest(userAgent)).Request.Browser;
+            return new HttpBrowserCapabilitiesWrapper(overriddenBrowser);
+        }
+
+        /// <summary>
+        /// Gets the overridden browser for the request based on the overridden user agent.
+        /// If no overridden user agent is set, returns the browser for the request.
+        /// </summary>
+        public static HttpBrowserCapabilitiesBase GetOverriddenBrowser(this HttpContextBase httpContext)
+        {
+            return GetOverriddenBrowser(httpContext, CreateOverriddenBrowser);
+        }
+
+        internal static HttpBrowserCapabilitiesBase GetOverriddenBrowser(this HttpContextBase httpContext, Func<string, HttpBrowserCapabilitiesBase> createBrowser)
+        {
+            HttpBrowserCapabilitiesBase overriddenBrowser = (HttpBrowserCapabilitiesBase)httpContext.Items[_browserOverrideKey];
+
+            if (overriddenBrowser == null)
+            {
+                string overriddenUserAgent = GetOverriddenUserAgent(httpContext);
+
+                if (!String.Equals(overriddenUserAgent, httpContext.Request.UserAgent))
+                {
+                    overriddenBrowser = createBrowser(overriddenUserAgent);
+                }
+                else
+                {
+                    overriddenBrowser = httpContext.Request.Browser;
+                }
+
+                httpContext.Items[_browserOverrideKey] = overriddenBrowser;
+            }
+
+            return overriddenBrowser;
+        }
+
+        /// <summary>
+        /// Gets the overridden user agent for the request. If no overridden user agent is set, returns the user agent for the request.
+        /// </summary>
+        public static string GetOverriddenUserAgent(this HttpContextBase httpContext)
+        {
+            return (string)httpContext.Items[_userAgentKey] ??
+                   BrowserOverrideStores.Current.GetOverriddenUserAgent(httpContext) ??
+                   httpContext.Request.UserAgent;
+        }
+
+        /// <summary>
+        /// Gets a string that varies based upon the type of the browser. Can be used to override
+        /// System.Web.HttpApplication.GetVaryByCustomString to differentiate cache keys based on
+        /// the overridden browser.
+        /// </summary>
+        public static string GetVaryByCustomStringForOverriddenBrowser(this HttpContext httpContext)
+        {
+            return GetVaryByCustomStringForOverriddenBrowser(new HttpContextWrapper(httpContext));
+        }
+
+        /// <summary>
+        /// Gets a string that varies based upon the type of the browser. Can be used to override
+        /// System.Web.HttpApplication.GetVaryByCustomString to differentiate cache keys based on
+        /// the overridden browser.
+        /// </summary>
+        public static string GetVaryByCustomStringForOverriddenBrowser(this HttpContextBase httpContext)
+        {
+            return GetVaryByCustomStringForOverriddenBrowser(httpContext, userAgent => CreateOverriddenBrowser(userAgent));
+        }
+
+        internal static string GetVaryByCustomStringForOverriddenBrowser(this HttpContextBase httpContext, Func<string, HttpBrowserCapabilitiesBase> generateBrowser)
+        {
+            return GetOverriddenBrowser(httpContext, generateBrowser).Type;
+        }
+
+        /// <summary>
+        /// Sets the overridden user agent for the request using a BrowserOverride.
+        /// </summary>
+        public static void SetOverriddenBrowser(this HttpContextBase httpContext, BrowserOverride browserOverride)
+        {
+            string userAgent = null;
+
+            switch (browserOverride)
+            {
+                case BrowserOverride.Desktop:
+                    // bug:262389 override only if the request was not made from a browser or the browser is not of a desktop device
+                    if (httpContext.Request.Browser == null || httpContext.Request.Browser.IsMobileDevice)
+                    {
+                        userAgent = DesktopUserAgent;
+                    }
+                    break;
+                case BrowserOverride.Mobile:
+                    if (httpContext.Request.Browser == null || !httpContext.Request.Browser.IsMobileDevice)
+                    {
+                        userAgent = MobileUserAgent;
+                    }
+                    break;
+            }
+
+            if (userAgent != null)
+            {
+                SetOverriddenBrowser(httpContext, userAgent);
+            }
+            else
+            {
+                ClearOverriddenBrowser(httpContext);
+            }
+        }
+
+        /// <summary>
+        /// Sets the overridden user agent for the request using a string
+        /// </summary>
+        public static void SetOverriddenBrowser(this HttpContextBase httpContext, string userAgent)
+        {
+            // Set the overridden user agent and clear the overridden browser
+            // so that it can be generated from the new overridden user agent.
+            httpContext.Items[_userAgentKey] = userAgent;
+            httpContext.Items[_browserOverrideKey] = null;
+
+            BrowserOverrideStores.Current.SetOverriddenUserAgent(httpContext, userAgent);
+        }
+
+        private sealed class UserAgentWorkerRequest : SimpleWorkerRequest
+        {
+            private readonly string _userAgent;
+
+            public UserAgentWorkerRequest(string userAgent)
+                : base(String.Empty, String.Empty, output: null)
+            {
+                _userAgent = userAgent;
+            }
+
+            public override string GetKnownRequestHeader(int index)
+            {
+                return index == HeaderUserAgent ? _userAgent : null;
+            }
+        }
+    }
+}