Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Web/Hosting/ProcessHostSupportFunctionsExtensions.cs

@@ -0,0 +1,54 @@
+//------------------------------------------------------------------------------
+// <copyright file="ProcessHostSupportFunctionsExtensions.cs" company="Microsoft">
+//     Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>                                                                
+//------------------------------------------------------------------------------
+
+namespace System.Web.Hosting {
+    using System;
+    using System.Text;
+    using System.Web.Util;
+
+    internal static class ProcessHostSupportFunctionsExtensions {
+
+        // Use this instead of MapPath, as it encapsulates the correct way to invoke
+        // the MapPath method. Didn't bother much with efficiency since it's called
+        // so few times.
+        //
+        // Example inputs: MapPathInternal(appId, "/appVPath", "/bin/foo.dll");
+        public static string MapPathInternal(this IProcessHostSupportFunctions supportFunctions, string appId, string appVirtualPath, string relativePath) {
+            Debug.Assert(supportFunctions != null);
+            Debug.Assert(!String.IsNullOrWhiteSpace(appId));
+            Debug.Assert(!String.IsNullOrWhiteSpace(appVirtualPath) && appVirtualPath[0] == '/');
+            Debug.Assert(relativePath != null);
+
+            StringBuilder fullVirtualPath = new StringBuilder(appVirtualPath.Length + relativePath.Length + 2 /* for slashes */);
+
+            // Ensure the app virtual path is always preceded by a slash
+            if (appVirtualPath[0] != '/') {
+                fullVirtualPath.Append('/');
+            }
+            fullVirtualPath.Append(appVirtualPath);
+
+            // Ensure the app virtual path always ends with a slash
+            if (fullVirtualPath[fullVirtualPath.Length - 1] != '/') {
+                fullVirtualPath.Append('/');
+            }
+
+            // Append the relative path, removing the preceding slash if necessary
+            if (relativePath.Length > 0) {
+                if (relativePath[0] == '/') {
+                    fullVirtualPath.Append(relativePath, 1, relativePath.Length - 1);
+                }
+                else {
+                    fullVirtualPath.Append(relativePath);
+                }
+            }
+
+            string physicalPath;
+            supportFunctions.MapPath(appId, fullVirtualPath.ToString(), out physicalPath);
+            return physicalPath;
+        }
+
+    }
+}