Pack/Unpack implementation for Any.

We still need the JSON representation, which relies on something like a DescriptorPool to fetch message types from based on the type URL. That will come a bit later.
(The DescriptorPool comment in this commit is just a note which will prove useful if we use DescriptorPool itself.)

3 files changed, 82 insertions, 0 deletions

diff --git a/csharp/src/Google.Protobuf/Google.Protobuf.csproj b/csharp/src/Google.Protobuf/Google.Protobuf.csproj
index a17bf81c..8c680d46 100644
--- a/csharp/src/Google.Protobuf/Google.Protobuf.csproj
+++ b/csharp/src/Google.Protobuf/Google.Protobuf.csproj
@@ -118,6 +118,7 @@
     <Compile Include="Reflection\SingleFieldAccessor.cs" />

     <Compile Include="Preconditions.cs" />

     <Compile Include="WellKnownTypes\Any.cs" />

+    <Compile Include="WellKnownTypes\AnyPartial.cs" />

     <Compile Include="WellKnownTypes\Api.cs" />

     <Compile Include="WellKnownTypes\Duration.cs" />

     <Compile Include="WellKnownTypes\DurationPartial.cs" />

diff --git a/csharp/src/Google.Protobuf/Reflection/DescriptorPool.cs b/csharp/src/Google.Protobuf/Reflection/DescriptorPool.cs
index 759955e6..99ca4bf3 100644
--- a/csharp/src/Google.Protobuf/Reflection/DescriptorPool.cs
+++ b/csharp/src/Google.Protobuf/Reflection/DescriptorPool.cs
@@ -96,6 +96,8 @@ namespace Google.Protobuf.Reflection
                 return descriptor;
             }
 
+            // dependencies contains direct dependencies and any *public* dependencies
+            // of those dependencies (transitively)... so we don't need to recurse here.
             foreach (FileDescriptor dependency in dependencies)
             {
                 dependency.DescriptorPool.descriptorsByName.TryGetValue(fullName, out result);
diff --git a/csharp/src/Google.Protobuf/WellKnownTypes/AnyPartial.cs b/csharp/src/Google.Protobuf/WellKnownTypes/AnyPartial.cs
new file mode 100644
index 00000000..082f7432
--- /dev/null
+++ b/csharp/src/Google.Protobuf/WellKnownTypes/AnyPartial.cs
@@ -0,0 +1,79 @@
+#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2015 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// 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.
+#endregion
+
+using Google.Protobuf.Reflection;
+
+namespace Google.Protobuf.WellKnownTypes
+{
+    public partial class Any
+    {
+        // This could be moved to MessageDescriptor if we wanted to, but keeping it here means
+        // all the Any-specific code is in the same place.
+        private static string GetTypeUrl(MessageDescriptor descriptor)
+        {
+            return "type.googleapis.com/" + descriptor.FullName;
+        }
+
+        /// <summary>
+        /// Unpacks the content of this Any message into the target message type,
+        /// which must match the type URL within this Any message.
+        /// </summary>
+        /// <typeparam name="T">The type of message to unpack the content into.</typeparam>
+        /// <returns>The unpacked message.</returns>
+        /// <exception cref="InvalidProtocolBufferException">The target message type doesn't match the type URL in this message</exception>
+        public T Unpack<T>() where T : IMessage, new()
+        {
+            // Note: this doesn't perform as well is it might. We could take a MessageParser<T> in an alternative overload,
+            // which would be expected to perform slightly better... although the difference is likely to be negligible.
+            T target = new T();
+            string targetTypeUrl = GetTypeUrl(target.Descriptor);
+            if (TypeUrl != targetTypeUrl)
+            {
+                throw new InvalidProtocolBufferException(string.Format("Type url for {0} is {1}; Any message's type url is {2}",
+                    target.Descriptor.Name, targetTypeUrl, TypeUrl));
+            }
+            target.MergeFrom(Value);
+            return target;
+        }
+
+        /// <summary>
+        /// Packs the specified message into an Any message.
+        /// </summary>
+        /// <param name="message">The message to pack.</param>
+        /// <returns>An Any message with the content and type URL of <paramref name="message"/>.</returns>
+        public static Any Pack(IMessage message)
+        {
+            Preconditions.CheckNotNull(message, "message");
+            return new Any { TypeUrl = GetTypeUrl(message.Descriptor), Value = message.ToByteString() };
+        }
+    }
+}