1 files changed, 87 insertions, 0 deletions
diff --git a/src/mscorlib/shared/System/Resources/ResourceFallbackManager.cs b/src/mscorlib/shared/System/Resources/ResourceFallbackManager.cs
new file mode 100644
index 0000000000..8268f3208d
--- /dev/null
+++ b/src/mscorlib/shared/System/Resources/ResourceFallbackManager.cs
@@ -0,0 +1,87 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** 
+** 
+**
+**
+** Purpose: Encapsulates CultureInfo fallback for resource 
+** lookup
+**
+** 
+===========================================================*/
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Globalization;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
+
+namespace System.Resources
+{
+    internal class ResourceFallbackManager : IEnumerable<CultureInfo>
+    {
+        private CultureInfo m_startingCulture;
+        private CultureInfo m_neutralResourcesCulture;
+        private bool m_useParents;
+
+        internal ResourceFallbackManager(CultureInfo startingCulture, CultureInfo neutralResourcesCulture, bool useParents)
+        {
+            if (startingCulture != null)
+            {
+                m_startingCulture = startingCulture;
+            }
+            else
+            {
+                m_startingCulture = CultureInfo.CurrentUICulture;
+            }
+
+            m_neutralResourcesCulture = neutralResourcesCulture;
+            m_useParents = useParents;
+        }
+
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return GetEnumerator();
+        }
+
+        // WARING: This function must be kept in sync with ResourceManager.GetFirstResourceSet()
+        public IEnumerator<CultureInfo> GetEnumerator()
+        {
+            bool reachedNeutralResourcesCulture = false;
+
+            // 1. starting culture chain, up to neutral
+            CultureInfo currentCulture = m_startingCulture;
+            do
+            {
+                if (m_neutralResourcesCulture != null && currentCulture.Name == m_neutralResourcesCulture.Name)
+                {
+                    // Return the invariant culture all the time, even if the UltimateResourceFallbackLocation
+                    // is a satellite assembly.  This is fixed up later in ManifestBasedResourceGroveler::UltimateFallbackFixup.
+                    yield return CultureInfo.InvariantCulture;
+                    reachedNeutralResourcesCulture = true;
+                    break;
+                }
+                yield return currentCulture;
+                currentCulture = currentCulture.Parent;
+            } while (m_useParents && !currentCulture.HasInvariantCultureName);
+
+            if (!m_useParents || m_startingCulture.HasInvariantCultureName)
+            {
+                yield break;
+            }
+
+            // 2. invariant
+            //    Don't return invariant twice though.
+            if (reachedNeutralResourcesCulture)
+                yield break;
+
+            yield return CultureInfo.InvariantCulture;
+        }
+    }
+}