1 files changed, 85 insertions, 0 deletions
diff --git a/csharp/src/ProtocolBuffers/Descriptors/FieldMappingAttribute.cs b/csharp/src/ProtocolBuffers/Descriptors/FieldMappingAttribute.cs
new file mode 100644
index 00000000..752ecf66
--- /dev/null
+++ b/csharp/src/ProtocolBuffers/Descriptors/FieldMappingAttribute.cs
@@ -0,0 +1,85 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// http://github.com/jskeet/dotnet-protobufs/
+// Original C++/Java/Python code:
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+using System;
+using System.Collections.Generic;
+using System.Reflection;
+using Google.ProtocolBuffers.Collections;
+
+namespace Google.ProtocolBuffers.Descriptors
+{
+    /// <summary>
+    /// Defined specifically for the <see cref="FieldType" /> enumeration,
+    /// this allows each field type to specify the mapped type and wire type.
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Field)]
+    public sealed class FieldMappingAttribute : Attribute
+    {
+        public FieldMappingAttribute(MappedType mappedType, WireFormat.WireType wireType)
+        {
+            MappedType = mappedType;
+            WireType = wireType;
+        }
+
+        public MappedType MappedType { get; private set; }
+        public WireFormat.WireType WireType { get; private set; }
+
+
+        /// <summary>
+        /// Immutable mapping from field type to mapped type. Built using the attributes on
+        /// FieldType values.
+        /// </summary>
+        private static readonly IDictionary<FieldType, FieldMappingAttribute> FieldTypeToMappedTypeMap = MapFieldTypes();
+
+        private static IDictionary<FieldType, FieldMappingAttribute> MapFieldTypes()
+        {
+            var map = new Dictionary<FieldType, FieldMappingAttribute>();
+            foreach (FieldInfo field in typeof(FieldType).GetFields(BindingFlags.Static | BindingFlags.Public))
+            {
+                FieldType fieldType = (FieldType) field.GetValue(null);
+                FieldMappingAttribute mapping =
+                    (FieldMappingAttribute) field.GetCustomAttributes(typeof(FieldMappingAttribute), false)[0];
+                map[fieldType] = mapping;
+            }
+            return Dictionaries.AsReadOnly(map);
+        }
+
+        internal static MappedType MappedTypeFromFieldType(FieldType type)
+        {
+            return FieldTypeToMappedTypeMap[type].MappedType;
+        }
+
+        internal static WireFormat.WireType WireTypeFromFieldType(FieldType type, bool packed)
+        {
+            return packed ? WireFormat.WireType.LengthDelimited : FieldTypeToMappedTypeMap[type].WireType;
+        }
+    }
+}
+\ No newline at end of file