Merge pull request #543 from jskeet/proto3-map

Proto3 map support for C#

cmake/libprotoc.cmake

@@ -19,6 +19,7 @@ set(libprotoc_files
   ${protobuf_source_dir}/src/google/protobuf/compiler/csharp/csharp_field_base.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/csharp/csharp_generator.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/csharp/csharp_helpers.cc
+  ${protobuf_source_dir}/src/google/protobuf/compiler/csharp/csharp_map_field.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/csharp/csharp_message.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/csharp/csharp_message_field.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/csharp/csharp_primitive_field.cc

csharp/generate_protos.sh

@@ -43,10 +43,12 @@ $PROTOC -Isrc --csharp_out=csharp/src/ProtocolBuffers/DescriptorProtos \
 rm src/google/protobuf/descriptor_proto_file.proto
 
 $PROTOC -Isrc --csharp_out=csharp/src/ProtocolBuffers.Test/TestProtos \
+    src/google/protobuf/map_unittest_proto3.proto \
     src/google/protobuf/unittest_proto3.proto \
     src/google/protobuf/unittest_import_proto3.proto \
     src/google/protobuf/unittest_import_public_proto3.proto
 
+
 $PROTOC -Icsharp/protos/extest --csharp_out=csharp/src/ProtocolBuffers.Test/TestProtos \
     csharp/protos/extest/unittest_issues.proto
 

csharp/src/AddressBook/Addressbook.cs

@@ -155,7 +155,7 @@ namespace Google.ProtocolBuffers.Examples.AddressBook {
     }
 
     public override int GetHashCode() {
-      int hash = 0;
+      int hash = 1;
       if (Name.Length != 0) hash ^= Name.GetHashCode();
       if (Id != 0) hash ^= Id.GetHashCode();
       if (Email.Length != 0) hash ^= Email.GetHashCode();
@@ -200,6 +200,7 @@ namespace Google.ProtocolBuffers.Examples.AddressBook {
       }
       return size;
     }
+
     public void MergeFrom(Person other) {
       if (other == null) {
         return;
@@ -329,7 +330,7 @@ namespace Google.ProtocolBuffers.Examples.AddressBook {
         }
 
         public override int GetHashCode() {
-          int hash = 0;
+          int hash = 1;
           if (Number.Length != 0) hash ^= Number.GetHashCode();
           if (Type != global::Google.ProtocolBuffers.Examples.AddressBook.Person.Types.PhoneType.HOME) hash ^= Type.GetHashCode();
           return hash;
@@ -356,6 +357,7 @@ namespace Google.ProtocolBuffers.Examples.AddressBook {
           }
           return size;
         }
+
         public void MergeFrom(PhoneNumber other) {
           if (other == null) {
             return;
@@ -456,7 +458,7 @@ namespace Google.ProtocolBuffers.Examples.AddressBook {
     }
 
     public override int GetHashCode() {
-      int hash = 0;
+      int hash = 1;
       hash ^= person_.GetHashCode();
       return hash;
     }
@@ -477,6 +479,7 @@ namespace Google.ProtocolBuffers.Examples.AddressBook {
       }
       return size;
     }
+
     public void MergeFrom(AddressBook other) {
       if (other == null) {
         return;

csharp/src/ProtocolBuffers.Test/RepeatedFieldTest.cs → csharp/src/ProtocolBuffers.Test/Collections/RepeatedFieldTest.cs

 using System;
 using System.Collections.Generic;
-using Google.Protobuf.Collections;
 using Google.Protobuf.TestProtos;
 using NUnit.Framework;
 
-namespace Google.Protobuf
+namespace Google.Protobuf.Collections
 {
     public class RepeatedFieldTest
     {

csharp/src/ProtocolBuffers.Test/EqualityTester.cs

+#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 System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using NUnit.Framework;
+
+namespace Google.Protobuf
+{
+    /// <summary>
+    /// Helper methods when testing equality. NUnit's Assert.AreEqual and
+    /// Assert.AreNotEqual methods try to be clever with collections, which can
+    /// be annoying...
+    /// </summary>
+    internal static class EqualityTester
+    {
+        public static void AssertEquality<T>(T first, T second) where T : IEquatable<T>
+        {
+            Assert.IsTrue(first.Equals(second));
+            Assert.AreEqual(first.GetHashCode(), second.GetHashCode());
+        }
+
+        public static void AssertInequality<T>(T first, T second) where T : IEquatable<T>
+        {
+            Assert.IsFalse(first.Equals(second));
+            // While this isn't a requirement, the chances of this test failing due to
+            // coincidence rather than a bug are very small.
+            Assert.AreNotEqual(first.GetHashCode(), second.GetHashCode());
+        }
+    }
+}

csharp/src/ProtocolBuffers.Test/FieldCodecTest.cs

+#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 System.Collections.Generic;
+using System.IO;
+using Google.Protobuf.TestProtos;
+using NUnit.Framework;
+
+namespace Google.Protobuf
+{
+    public class FieldCodecTest
+    {
+        private static readonly List<ICodecTestData> Codecs = new List<ICodecTestData>
+        {
+            new FieldCodecTestData<bool>(FieldCodec.ForBool(100), true, "Bool"),
+            new FieldCodecTestData<string>(FieldCodec.ForString(100), "sample", "String"),
+            new FieldCodecTestData<ByteString>(FieldCodec.ForBytes(100), ByteString.CopyFrom(1, 2, 3), "Bytes"),
+            new FieldCodecTestData<int>(FieldCodec.ForInt32(100), -1000, "Int32"),
+            new FieldCodecTestData<int>(FieldCodec.ForSInt32(100), -1000, "SInt32"),
+            new FieldCodecTestData<int>(FieldCodec.ForSFixed32(100), -1000, "SFixed32"),
+            new FieldCodecTestData<uint>(FieldCodec.ForUInt32(100), 1234, "UInt32"),
+            new FieldCodecTestData<uint>(FieldCodec.ForFixed32(100), 1234, "Fixed32"),
+            new FieldCodecTestData<long>(FieldCodec.ForInt64(100), -1000, "Int64"),
+            new FieldCodecTestData<long>(FieldCodec.ForSInt64(100), -1000, "SInt64"),
+            new FieldCodecTestData<long>(FieldCodec.ForSFixed64(100), -1000, "SFixed64"),
+            new FieldCodecTestData<ulong>(FieldCodec.ForUInt64(100), 1234, "UInt64"),
+            new FieldCodecTestData<ulong>(FieldCodec.ForFixed64(100), 1234, "Fixed64"),
+            new FieldCodecTestData<float>(FieldCodec.ForFloat(100), 1234.5f, "Float"),
+            new FieldCodecTestData<double>(FieldCodec.ForDouble(100), 1234567890.5d, "Double"),
+            new FieldCodecTestData<ForeignEnum>(
+                FieldCodec.ForEnum(100, t => (int) t, t => (ForeignEnum) t), ForeignEnum.FOREIGN_BAZ, "Enum"),
+            new FieldCodecTestData<ForeignMessage>(
+                FieldCodec.ForMessage(100, ForeignMessage.Parser), new ForeignMessage { C = 10 }, "Message"),
+        };
+
+        [Test, TestCaseSource("Codecs")]
+        public void RoundTrip(ICodecTestData codec)
+        {
+            codec.TestRoundTrip();
+        }
+
+        [Test, TestCaseSource("Codecs")]
+        public void CalculateSize(ICodecTestData codec)
+        {
+            codec.TestCalculateSize();
+        }
+
+        [Test, TestCaseSource("Codecs")]
+        public void DefaultValue(ICodecTestData codec)
+        {
+            codec.TestDefaultValue();
+        }
+
+        public interface ICodecTestData
+        {
+            void TestRoundTrip();
+            void TestCalculateSize();
+            void TestDefaultValue();
+        }
+
+        public class FieldCodecTestData<T> : ICodecTestData
+        {
+            private readonly FieldCodec<T> codec;
+            private readonly T sampleValue;
+            private readonly string name;
+
+            public FieldCodecTestData(FieldCodec<T> codec, T sampleValue, string name)
+            {
+                this.codec = codec;
+                this.sampleValue = sampleValue;
+                this.name = name;
+            }
+
+            public void TestRoundTrip()
+            {
+                var stream = new MemoryStream();
+                var codedOutput = CodedOutputStream.CreateInstance(stream);
+                codec.Write(codedOutput, sampleValue);
+                codedOutput.Flush();
+                stream.Position = 0;
+                var codedInput = CodedInputStream.CreateInstance(stream);
+                uint tag;
+                Assert.IsTrue(codedInput.ReadTag(out tag));
+                Assert.AreEqual(codec.Tag, tag);
+                Assert.AreEqual(sampleValue, codec.Read(codedInput));
+                Assert.IsTrue(codedInput.IsAtEnd);
+            }
+
+            public void TestCalculateSize()
+            {
+                var stream = new MemoryStream();
+                var codedOutput = CodedOutputStream.CreateInstance(stream);
+                codec.Write(codedOutput, sampleValue);
+                codedOutput.Flush();
+                Assert.AreEqual(stream.Position, codec.CalculateSize(sampleValue));
+            }
+
+            public void TestDefaultValue()
+            {
+                var stream = new MemoryStream();
+                var codedOutput = CodedOutputStream.CreateInstance(stream);
+                codec.Write(codedOutput, codec.DefaultValue);
+                codedOutput.Flush();
+                Assert.AreEqual(0, stream.Position);
+                Assert.AreEqual(0, codec.CalculateSize(codec.DefaultValue));
+                if (typeof(T).IsValueType)
+                {
+                    Assert.AreEqual(default(T), codec.DefaultValue);
+                }
+            }
+
+            public string Description { get { return name; } }
+
+            public override string ToString()
+            {
+                return name;
+            }
+        }
+    }
+}

csharp/src/ProtocolBuffers.Test/GeneratedMessageTest.cs

 using System;
+using System.IO;
 using Google.Protobuf.TestProtos;
 using NUnit.Framework;
 
@@ -9,6 +10,15 @@ namespace Google.Protobuf
     /// </summary>
     public class GeneratedMessageTest
     {
+        [Test]
+        public void EmptyMessageFieldDistinctFromMissingMessageField()
+        {
+            // This demonstrates what we're really interested in...
+            var message1 = new TestAllTypes { SingleForeignMessage = new ForeignMessage() };
+            var message2 = new TestAllTypes(); // SingleForeignMessage is null
+            EqualityTester.AssertInequality(message1, message2);
+        }
+
         [Test]
         public void DefaultValues()
         {
@@ -146,6 +156,206 @@ namespace Google.Protobuf
             Assert.AreEqual(message, parsed);
         }
 
+        // Note that not every map within map_unittest_proto3 is used. They all go through very
+        // similar code paths. The fact that all maps are present is validation that we have codecs
+        // for every type.
+        [Test]
+        public void RoundTrip_Maps()
+        {
+            var message = new TestMap
+            {
+                MapBoolBool = {
+                    { false, true },
+                    { true, false }
+                },
+                MapInt32Bytes = {
+                    { 5, ByteString.CopyFrom(6, 7, 8) },
+                    { 25, ByteString.CopyFrom(1, 2, 3, 4, 5) },
+                    { 10, ByteString.Empty }
+                },
+                MapInt32ForeignMessage = {
+                    { 0, new ForeignMessage { C = 10 } },
+                    { 5, null },
+                },
+                MapInt32Enum = {
+                    { 1, MapEnum.MAP_ENUM_BAR },
+                    { 2000, MapEnum.MAP_ENUM_FOO }
+                }
+            };
+
+            byte[] bytes = message.ToByteArray();
+            TestMap parsed = TestMap.Parser.ParseFrom(bytes);
+            Assert.AreEqual(message, parsed);
+        }
+
+        [Test]
+        public void MapWithEmptyEntry()
+        {
+            var message = new TestMap
+            {
+                MapInt32Bytes = { { 0, ByteString.Empty } }
+            };
+
+            byte[] bytes = message.ToByteArray();
+            Assert.AreEqual(2, bytes.Length); // Tag for field entry (1 byte), length of entry (0; 1 byte)
+
+            var parsed = TestMap.Parser.ParseFrom(bytes);
+            Assert.AreEqual(1, parsed.MapInt32Bytes.Count);
+            Assert.AreEqual(ByteString.Empty, parsed.MapInt32Bytes[0]);
+        }
+        
+        [Test]
+        public void MapWithOnlyValue()
+        {
+            // Hand-craft the stream to contain a single entry with just a value.
+            var memoryStream = new MemoryStream();
+            var output = CodedOutputStream.CreateInstance(memoryStream);
+            output.WriteTag(TestMap.MapInt32ForeignMessageFieldNumber, WireFormat.WireType.LengthDelimited);
+            var nestedMessage = new ForeignMessage { C = 20 };
+            // Size of the entry (tag, size written by WriteMessage, data written by WriteMessage)
+            output.WriteRawVarint32((uint)(nestedMessage.CalculateSize() + 3));
+            output.WriteTag(2, WireFormat.WireType.LengthDelimited);
+            output.WriteMessage(nestedMessage);
+            output.Flush();
+
+            var parsed = TestMap.Parser.ParseFrom(memoryStream.ToArray());
+            Assert.AreEqual(nestedMessage, parsed.MapInt32ForeignMessage[0]);
+        }
+
+        [Test]
+        public void MapIgnoresExtraFieldsWithinEntryMessages()
+        {
+            // Hand-craft the stream to contain a single entry with three fields
+            var memoryStream = new MemoryStream();
+            var output = CodedOutputStream.CreateInstance(memoryStream);
+
+            output.WriteTag(TestMap.MapInt32Int32FieldNumber, WireFormat.WireType.LengthDelimited);
+
+            var key = 10; // Field 1 
+            var value = 20; // Field 2
+            var extra = 30; // Field 3
+
+            // Each field can be represented in a single byte, with a single byte tag.
+            // Total message size: 6 bytes.
+            output.WriteRawVarint32(6);
+            output.WriteTag(1, WireFormat.WireType.Varint);
+            output.WriteInt32(key);
+            output.WriteTag(2, WireFormat.WireType.Varint);
+            output.WriteInt32(value);
+            output.WriteTag(3, WireFormat.WireType.Varint);
+            output.WriteInt32(extra);
+            output.Flush();
+
+            var parsed = TestMap.Parser.ParseFrom(memoryStream.ToArray());
+            Assert.AreEqual(value, parsed.MapInt32Int32[key]);
+        }
+
+        [Test]
+        public void MapFieldOrderIsIrrelevant()
+        {
+            var memoryStream = new MemoryStream();
+            var output = CodedOutputStream.CreateInstance(memoryStream);
+
+            output.WriteTag(TestMap.MapInt32Int32FieldNumber, WireFormat.WireType.LengthDelimited);
+
+            var key = 10;
+            var value = 20;
+
+            // Each field can be represented in a single byte, with a single byte tag.
+            // Total message size: 4 bytes.
+            output.WriteRawVarint32(4);
+            output.WriteTag(2, WireFormat.WireType.Varint);
+            output.WriteInt32(value);
+            output.WriteTag(1, WireFormat.WireType.Varint);
+            output.WriteInt32(key);
+            output.Flush();
+
+            var parsed = TestMap.Parser.ParseFrom(memoryStream.ToArray());
+            Assert.AreEqual(value, parsed.MapInt32Int32[key]);
+        }
+
+        [Test]
+        public void MapNonContiguousEntries()
+        {
+            var memoryStream = new MemoryStream();
+            var output = CodedOutputStream.CreateInstance(memoryStream);
+
+            // Message structure:
+            // Entry for MapInt32Int32
+            // Entry for MapStringString
+            // Entry for MapInt32Int32
+
+            // First entry
+            var key1 = 10;
+            var value1 = 20;
+            output.WriteTag(TestMap.MapInt32Int32FieldNumber, WireFormat.WireType.LengthDelimited);
+            output.WriteRawVarint32(4);
+            output.WriteTag(1, WireFormat.WireType.Varint);
+            output.WriteInt32(key1);
+            output.WriteTag(2, WireFormat.WireType.Varint);
+            output.WriteInt32(value1);
+
+            // Second entry
+            var key2 = "a";
+            var value2 = "b";
+            output.WriteTag(TestMap.MapStringStringFieldNumber, WireFormat.WireType.LengthDelimited);
+            output.WriteRawVarint32(6); // 3 bytes per entry: tag, size, character
+            output.WriteTag(1, WireFormat.WireType.LengthDelimited);
+            output.WriteString(key2);
+            output.WriteTag(2, WireFormat.WireType.LengthDelimited);
+            output.WriteString(value2);
+
+            // Third entry
+            var key3 = 15;
+            var value3 = 25;
+            output.WriteTag(TestMap.MapInt32Int32FieldNumber, WireFormat.WireType.LengthDelimited);
+            output.WriteRawVarint32(4);
+            output.WriteTag(1, WireFormat.WireType.Varint);
+            output.WriteInt32(key3);
+            output.WriteTag(2, WireFormat.WireType.Varint);
+            output.WriteInt32(value3);
+
+            output.Flush();
+            var parsed = TestMap.Parser.ParseFrom(memoryStream.ToArray());
+            var expected = new TestMap
+            {
+                MapInt32Int32 = { { key1, value1 }, { key3, value3 } },
+                MapStringString = { { key2, value2 } }
+            };
+            Assert.AreEqual(expected, parsed);
+        }
+
+        [Test]
+        public void DuplicateKeys_LastEntryWins()
+        {
+            var memoryStream = new MemoryStream();
+            var output = CodedOutputStream.CreateInstance(memoryStream);
+
+            var key = 10;
+            var value1 = 20;
+            var value2 = 30;
+
+            // First entry
+            output.WriteTag(TestMap.MapInt32Int32FieldNumber, WireFormat.WireType.LengthDelimited);
+            output.WriteRawVarint32(4);
+            output.WriteTag(1, WireFormat.WireType.Varint);
+            output.WriteInt32(key);
+            output.WriteTag(2, WireFormat.WireType.Varint);
+            output.WriteInt32(value1);
+
+            // Second entry - same key, different value
+            output.WriteTag(TestMap.MapInt32Int32FieldNumber, WireFormat.WireType.LengthDelimited);
+            output.WriteRawVarint32(4);
+            output.WriteTag(1, WireFormat.WireType.Varint);
+            output.WriteInt32(key);
+            output.WriteTag(2, WireFormat.WireType.Varint);
+            output.WriteInt32(value2);
+            output.Flush();
+
+            var parsed = TestMap.Parser.ParseFrom(memoryStream.ToArray());
+            Assert.AreEqual(value2, parsed.MapInt32Int32[key]);
+        }
+
         [Test]
         public void CloneSingleNonMessageValues()
         {

csharp/src/ProtocolBuffers.Test/ProtocolBuffers.Test.csproj

@@ -74,8 +74,12 @@
     <Compile Include="ByteStringTest.cs" />
     <Compile Include="CodedInputStreamTest.cs" />
     <Compile Include="CodedOutputStreamTest.cs" />
+    <Compile Include="EqualityTester.cs" />
+    <Compile Include="FieldCodecTest.cs" />
     <Compile Include="GeneratedMessageTest.cs" />
-    <Compile Include="RepeatedFieldTest.cs" />
+    <Compile Include="Collections\MapFieldTest.cs" />
+    <Compile Include="Collections\RepeatedFieldTest.cs" />
+    <Compile Include="TestProtos\MapUnittestProto3.cs" />
     <Compile Include="TestProtos\UnittestImportProto3.cs" />
     <Compile Include="TestProtos\UnittestImportPublicProto3.cs" />
     <Compile Include="TestProtos\UnittestIssues.cs" />
@@ -99,9 +103,7 @@
   <ItemGroup>
     <Service Include="{82A7F48D-3B50-4B1E-B82E-3ADA8210C358}" />
   </ItemGroup>
-  <ItemGroup>
-    <Folder Include="Collections\" />
-  </ItemGroup>
+  <ItemGroup />
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
   <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 
        Other similar extension points exist, see Microsoft.Common.targets.

csharp/src/ProtocolBuffers.Test/TestProtos/UnittestImportProto3.cs

@@ -120,7 +120,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override int GetHashCode() {
-      int hash = 0;
+      int hash = 1;
       if (D != 0) hash ^= D.GetHashCode();
       return hash;
     }
@@ -139,6 +139,7 @@ namespace Google.Protobuf.TestProtos {
       }
       return size;
     }
+
     public void MergeFrom(ImportMessage other) {
       if (other == null) {
         return;

csharp/src/ProtocolBuffers.Test/TestProtos/UnittestImportPublicProto3.cs

@@ -105,7 +105,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override int GetHashCode() {
-      int hash = 0;
+      int hash = 1;
       if (E != 0) hash ^= E.GetHashCode();
       return hash;
     }
@@ -124,6 +124,7 @@ namespace Google.Protobuf.TestProtos {
       }
       return size;
     }
+
     public void MergeFrom(PublicImportMessage other) {
       if (other == null) {
         return;

csharp/src/ProtocolBuffers.Test/TestProtos/UnittestIssues.cs

@@ -168,7 +168,7 @@ namespace UnitTest.Issues.TestProtos {
     }
 
     public override int GetHashCode() {
-      int hash = 0;
+      int hash = 1;
       if (Value != global::UnitTest.Issues.TestProtos.NegativeEnum.NEGATIVE_ENUM_ZERO) hash ^= Value.GetHashCode();
       hash ^= values_.GetHashCode();
       hash ^= packedValues_.GetHashCode();
@@ -212,6 +212,7 @@ namespace UnitTest.Issues.TestProtos {
       }
       return size;
     }
+
     public void MergeFrom(NegativeEnumMessage other) {
       if (other == null) {
         return;
@@ -303,7 +304,7 @@ namespace UnitTest.Issues.TestProtos {
     }
 
     public override int GetHashCode() {
-      int hash = 0;
+      int hash = 1;
       return hash;
     }
 
@@ -314,6 +315,7 @@ namespace UnitTest.Issues.TestProtos {
       int size = 0;
       return size;
     }
+
     public void MergeFrom(DeprecatedChild other) {
       if (other == null) {
         return;
@@ -456,7 +458,7 @@ namespace UnitTest.Issues.TestProtos {
     }
 
     public override int GetHashCode() {
-      int hash = 0;
+      int hash = 1;
       if (PrimitiveValue != 0) hash ^= PrimitiveValue.GetHashCode();
       hash ^= primitiveArray_.GetHashCode();
       if (messageValue_ != null) hash ^= MessageValue.GetHashCode();
@@ -527,6 +529,7 @@ namespace UnitTest.Issues.TestProtos {
       }
       return size;
     }
+
     public void MergeFrom(DeprecatedFieldsMessage other) {
       if (other == null) {
         return;
@@ -655,7 +658,7 @@ namespace UnitTest.Issues.TestProtos {
     }
 
     public override int GetHashCode() {
-      int hash = 0;
+      int hash = 1;
       if (Item != 0) hash ^= Item.GetHashCode();
       return hash;
     }
@@ -674,6 +677,7 @@ namespace UnitTest.Issues.TestProtos {
       }
       return size;
     }
+
     public void MergeFrom(ItemField other) {
       if (other == null) {
         return;

csharp/src/ProtocolBuffers/CodedInputStream.cs

@@ -456,14 +456,16 @@ namespace Google.Protobuf
         }
 
         /// <summary>
-        /// Returns true if the next tag is also part of the same unpacked array.
+        /// Peeks at the next tag in the stream. If it matches <paramref name="tag"/>,
+        /// the tag is consumed and the method returns <c>true</c>; otherwise, the
+        /// stream is left in the original position and the method returns <c>false</c>.
         /// </summary>
-        private bool ContinueArray(uint currentTag)
+        public bool MaybeConsumeTag(uint tag)
         {
             uint next;
             if (PeekNextTag(out next))
             {
-                if (next == currentTag)
+                if (next == tag)
                 {
                     hasNextTag = false;
                     return true;
@@ -486,17 +488,7 @@ namespace Google.Protobuf
                 }
                 return true;
             }
-
-            uint next;
-            if (PeekNextTag(out next))
-            {
-                if (next == currentTag)
-                {
-                    hasNextTag = false;
-                    return true;
-                }
-            }
-            return false;
+            return MaybeConsumeTag(currentTag);
         }
 
         /// <summary>
@@ -512,7 +504,7 @@ namespace Google.Protobuf
             do
             {
                 list.Add(ReadString());
-            } while (ContinueArray(fieldTag));
+            } while (MaybeConsumeTag(fieldTag));
         }
 
         public void ReadBytesArray(ICollection<ByteString> list)
@@ -521,7 +513,7 @@ namespace Google.Protobuf
             do
             {
                 list.Add(ReadBytes());
-            } while (ContinueArray(fieldTag));
+            } while (MaybeConsumeTag(fieldTag));
         }
 
         public void ReadBoolArray(ICollection<bool> list)
@@ -729,7 +721,7 @@ namespace Google.Protobuf
                 do
                 {
                     list.Add((T)(object) ReadEnum());
-                } while (ContinueArray(fieldTag));
+                } while (MaybeConsumeTag(fieldTag));
             }
         }
 
@@ -742,7 +734,7 @@ namespace Google.Protobuf
                 T message = messageParser.CreateTemplate();
                 ReadMessage(message);
                 list.Add(message);
-            } while (ContinueArray(fieldTag));
+            } while (MaybeConsumeTag(fieldTag));
         }
         #endregion
 

csharp/src/ProtocolBuffers/CodedOutputStream.cs

@@ -475,6 +475,14 @@ namespace Google.Protobuf
             WriteRawVarint32(WireFormat.MakeTag(fieldNumber, type));
         }
 
+        /// <summary>
+        /// Writes an already-encoded tag.
+        /// </summary>
+        public void WriteTag(uint tag)
+        {
+            WriteRawVarint32(tag);
+        }
+
         /// <summary>
         /// Writes the given single-byte tag directly to the stream.
         /// </summary>

csharp/src/ProtocolBuffers/Collections/RepeatedField.cs

@@ -193,7 +193,7 @@ namespace Google.Protobuf.Collections
 
         public override int GetHashCode()
         {
-            int hash = 23;
+            int hash = 0;
             for (int i = 0; i < count; i++)
             {
                 hash = hash * 31 + array[i].GetHashCode();

csharp/src/ProtocolBuffers/FieldCodec.cs

+using System;
+using System.Collections.Generic;
+
+namespace Google.Protobuf
+{
+    /// <summary>
+    /// Factory methods for <see cref="FieldCodec{T}"/>.
+    /// </summary>
+    public static class FieldCodec
+    {
+        public static FieldCodec<string> ForString(uint tag)
+        {
+            return new FieldCodec<string>(input => input.ReadString(), (output, value) => output.WriteString(value), CodedOutputStream.ComputeStringSize, tag); 
+        }
+
+        public static FieldCodec<ByteString> ForBytes(uint tag)
+        {
+            return new FieldCodec<ByteString>(input => input.ReadBytes(), (output, value) => output.WriteBytes(value), CodedOutputStream.ComputeBytesSize, tag);
+        }
+
+        public static FieldCodec<bool> ForBool(uint tag)
+        {
+            return new FieldCodec<bool>(input => input.ReadBool(), (output, value) => output.WriteBool(value), CodedOutputStream.ComputeBoolSize, tag);
+        }
+
+        public static FieldCodec<int> ForInt32(uint tag)
+        {
+            return new FieldCodec<int>(input => input.ReadInt32(), (output, value) => output.WriteInt32(value), CodedOutputStream.ComputeInt32Size, tag);
+        }
+
+        public static FieldCodec<int> ForSInt32(uint tag)
+        {
+            return new FieldCodec<int>(input => input.ReadSInt32(), (output, value) => output.WriteSInt32(value), CodedOutputStream.ComputeSInt32Size, tag);
+        }
+
+        public static FieldCodec<uint> ForFixed32(uint tag)
+        {
+            return new FieldCodec<uint>(input => input.ReadFixed32(), (output, value) => output.WriteFixed32(value), CodedOutputStream.ComputeFixed32Size, tag);
+        }
+
+        public static FieldCodec<int> ForSFixed32(uint tag)
+        {
+            return new FieldCodec<int>(input => input.ReadSFixed32(), (output, value) => output.WriteSFixed32(value), CodedOutputStream.ComputeSFixed32Size, tag);
+        }
+
+        public static FieldCodec<uint> ForUInt32(uint tag)
+        {
+            return new FieldCodec<uint>(input => input.ReadUInt32(), (output, value) => output.WriteUInt32(value), CodedOutputStream.ComputeUInt32Size, tag);
+        }
+
+        public static FieldCodec<long> ForInt64(uint tag)
+        {
+            return new FieldCodec<long>(input => input.ReadInt64(), (output, value) => output.WriteInt64(value), CodedOutputStream.ComputeInt64Size, tag);
+        }
+
+        public static FieldCodec<long> ForSInt64(uint tag)
+        {
+            return new FieldCodec<long>(input => input.ReadSInt64(), (output, value) => output.WriteSInt64(value), CodedOutputStream.ComputeSInt64Size, tag);
+        }
+
+        public static FieldCodec<ulong> ForFixed64(uint tag)
+        {
+            return new FieldCodec<ulong>(input => input.ReadFixed64(), (output, value) => output.WriteFixed64(value), CodedOutputStream.ComputeFixed64Size, tag);
+        }
+
+        public static FieldCodec<long> ForSFixed64(uint tag)
+        {
+            return new FieldCodec<long>(input => input.ReadSFixed64(), (output, value) => output.WriteSFixed64(value), CodedOutputStream.ComputeSFixed64Size, tag);
+        }
+
+        public static FieldCodec<ulong> ForUInt64(uint tag)
+        {
+            return new FieldCodec<ulong>(input => input.ReadUInt64(), (output, value) => output.WriteUInt64(value), CodedOutputStream.ComputeUInt64Size, tag);
+        }
+
+        public static FieldCodec<float> ForFloat(uint tag)
+        {
+            return new FieldCodec<float>(input => input.ReadFloat(), (output, value) => output.WriteFloat(value), CodedOutputStream.ComputeFloatSize, tag);
+        }
+
+        public static FieldCodec<double> ForDouble(uint tag)
+        {
+            return new FieldCodec<double>(input => input.ReadDouble(), (output, value) => output.WriteDouble(value), CodedOutputStream.ComputeDoubleSize, tag);
+        }
+
+        // Enums are tricky. We can probably use expression trees to build these delegates automatically,
+        // but it's easy to generate the code fdor it.
+        public static FieldCodec<T> ForEnum<T>(uint tag, Func<T, int> toInt32, Func<int, T> fromInt32)
+        {
+            return new FieldCodec<T>(input => fromInt32(
+                input.ReadEnum()),
+                (output, value) => output.WriteEnum(toInt32(value)),
+                value => CodedOutputStream.ComputeEnumSize(toInt32(value)), tag);
+        }
+
+        public static FieldCodec<T> ForMessage<T>(uint tag, MessageParser<T> parser) where T : IMessage<T>
+        {
+            return new FieldCodec<T>(input => { T message = parser.CreateTemplate(); input.ReadMessage(message); return message; },
+                (output, value) => output.WriteMessage(value), message => CodedOutputStream.ComputeMessageSize(message), tag);
+        }
+    }
+
+    /// <summary>
+    /// An encode/decode pair for a single field. This effectively encapsulates
+    /// all the information needed to read or write the field value from/to a coded
+    /// stream.
+    /// </summary>
+    /// <remarks>
+    /// This never writes default values to the stream, and is not currently designed
+    /// to play well with packed arrays.
+    /// </remarks>
+    public sealed class FieldCodec<T>
+    {
+        private static readonly Func<T, bool> IsDefault;
+        private static readonly T Default;
+
+        static FieldCodec()
+        {
+            if (typeof(T) == typeof(string))
+            {
+                Default = (T)(object)"";
+                IsDefault = CreateDefaultValueCheck<string>(x => x.Length == 0);
+            }
+            else if (typeof(T) == typeof(ByteString))
+            {
+                Default = (T)(object)ByteString.Empty;
+                IsDefault = CreateDefaultValueCheck<ByteString>(x => x.Length == 0);
+            }
+            else if (!typeof(T).IsValueType)
+            {
+                // Default default
+                IsDefault = CreateDefaultValueCheck<T>(x => x == null);
+            }
+            else
+            {
+                // Default default
+                IsDefault = CreateDefaultValueCheck<T>(x => EqualityComparer<T>.Default.Equals(x, default(T)));
+            }
+        }
+
+        private static Func<T, bool> CreateDefaultValueCheck<TTmp>(Func<TTmp, bool> check)
+        {
+            return (Func<T, bool>)(object)check;
+        }
+
+        private readonly Func<CodedInputStream, T> reader;
+        private readonly Action<CodedOutputStream, T> writer;
+        private readonly Func<T, int> sizeComputer;
+        private readonly uint tag;
+        private readonly int tagSize;
+
+        internal FieldCodec(
+            Func<CodedInputStream, T> reader,
+            Action<CodedOutputStream, T> writer,
+            Func<T, int> sizeComputer,
+            uint tag)
+        {
+            this.reader = reader;
+            this.writer = writer;
+            this.sizeComputer = sizeComputer;
+            this.tag = tag;
+            tagSize = CodedOutputStream.ComputeRawVarint32Size(tag);
+        }
+
+        public uint Tag { get { return tag; } }
+
+        public T DefaultValue { get { return Default; } }
+
+        public void Write(CodedOutputStream output, T value)
+        {
+            if (!IsDefault(value))
+            {
+                output.WriteTag(tag);
+                writer(output, value);
+            }
+        }
+
+        public T Read(CodedInputStream input)
+        {
+            return reader(input);
+        }
+
+        public int CalculateSize(T value)
+        {
+            return IsDefault(value) ? 0 : sizeComputer(value) + CodedOutputStream.ComputeRawVarint32Size(tag);
+        }        
+    }
+}

csharp/src/ProtocolBuffers/ProtocolBuffers.csproj

@@ -60,6 +60,7 @@
     <Compile Include="CodedOutputStream.cs" />
     <Compile Include="Collections\Dictionaries.cs" />
     <Compile Include="Collections\Lists.cs" />
+    <Compile Include="Collections\MapField.cs" />
     <Compile Include="Collections\ReadOnlyDictionary.cs" />
     <Compile Include="Collections\RepeatedField.cs" />
     <Compile Include="Collections\RepeatedFieldExtensions.cs" />
@@ -84,6 +85,7 @@
     <Compile Include="Descriptors\MethodDescriptor.cs" />
     <Compile Include="Descriptors\PackageDescriptor.cs" />
     <Compile Include="Descriptors\ServiceDescriptor.cs" />
+    <Compile Include="FieldCodec.cs" />
     <Compile Include="FrameworkPortability.cs" />
     <Compile Include="Freezable.cs" />
     <Compile Include="MessageExtensions.cs" />

src/Makefile.am

@@ -425,6 +425,8 @@ libprotoc_la_SOURCES =                                         \
   google/protobuf/compiler/csharp/csharp_generator.cc          \
   google/protobuf/compiler/csharp/csharp_helpers.cc            \
   google/protobuf/compiler/csharp/csharp_helpers.h             \
+  google/protobuf/compiler/csharp/csharp_map_field.cc          \
+  google/protobuf/compiler/csharp/csharp_map_field.h           \
   google/protobuf/compiler/csharp/csharp_message.cc            \
   google/protobuf/compiler/csharp/csharp_message.h             \
   google/protobuf/compiler/csharp/csharp_message_field.cc      \

src/google/protobuf/compiler/csharp/csharp_enum_field.cc

@@ -74,6 +74,12 @@ void EnumFieldGenerator::GenerateSerializedSizeCode(io::Printer* printer) {
     "}\n");
 }
 
+void EnumFieldGenerator::GenerateCodecCode(io::Printer* printer) {
+    printer->Print(
+        variables_,
+        "pb::FieldCodec.ForEnum($tag$, x => (int) x, x => ($type_name$) x)");
+}
+
 EnumOneofFieldGenerator::EnumOneofFieldGenerator(const FieldDescriptor* descriptor,
 						 int fieldOrdinal)
   : PrimitiveOneofFieldGenerator(descriptor, fieldOrdinal) {

src/google/protobuf/compiler/csharp/csharp_enum_field.h

@@ -46,6 +46,7 @@ class EnumFieldGenerator : public PrimitiveFieldGenerator {
   EnumFieldGenerator(const FieldDescriptor* descriptor, int fieldOrdinal);
   ~EnumFieldGenerator();
 
+  virtual void GenerateCodecCode(io::Printer* printer);
   virtual void GenerateParsingCode(io::Printer* printer);
   virtual void GenerateSerializationCode(io::Printer* printer);
   virtual void GenerateSerializedSizeCode(io::Printer* printer);

src/google/protobuf/compiler/csharp/csharp_field_base.cc

@@ -65,6 +65,7 @@ void FieldGeneratorBase::SetCommonFieldVariables(
     tag_bytes += ", " + SimpleItoa(tag_array[i]);
   }
 
+  (*variables)["tag"] = SimpleItoa(tag);
   (*variables)["tag_size"] = SimpleItoa(tag_size);
   (*variables)["tag_bytes"] = tag_bytes;
 
@@ -112,6 +113,11 @@ void FieldGeneratorBase::GenerateFreezingCode(io::Printer* printer) {
   // special handling for freezing, so default to not generating any code.
 }
 
+void FieldGeneratorBase::GenerateCodecCode(io::Printer* printer) {
+    // No-op: expect this to be overridden by appropriate types.
+    // Could fail if we get called here though...
+}
+
 void FieldGeneratorBase::AddDeprecatedFlag(io::Printer* printer) {
   if (descriptor_->options().deprecated())
   {
@@ -151,12 +157,16 @@ std::string FieldGeneratorBase::name() {
 }
 
 std::string FieldGeneratorBase::type_name() {
-  switch (descriptor_->type()) {
+  return type_name(descriptor_);
+}
+
+std::string FieldGeneratorBase::type_name(const FieldDescriptor* descriptor) {
+  switch (descriptor->type()) {
     case FieldDescriptor::TYPE_ENUM:
-      return GetClassName(descriptor_->enum_type());
+      return GetClassName(descriptor->enum_type());
     case FieldDescriptor::TYPE_MESSAGE:
     case FieldDescriptor::TYPE_GROUP:
-      return GetClassName(descriptor_->message_type());
+      return GetClassName(descriptor->message_type());
     case FieldDescriptor::TYPE_DOUBLE:
       return "double";
     case FieldDescriptor::TYPE_FLOAT:

src/google/protobuf/compiler/csharp/csharp_field_base.h

@@ -49,6 +49,7 @@ class FieldGeneratorBase : public SourceGeneratorBase {
 
   virtual void GenerateCloningCode(io::Printer* printer) = 0;
   virtual void GenerateFreezingCode(io::Printer* printer);
+  virtual void GenerateCodecCode(io::Printer* printer);
   virtual void GenerateMembers(io::Printer* printer) = 0;
   virtual void GenerateMergingCode(io::Printer* printer) = 0;
   virtual void GenerateParsingCode(io::Printer* printer) = 0;
@@ -76,6 +77,7 @@ class FieldGeneratorBase : public SourceGeneratorBase {
   std::string property_name();
   std::string name();
   std::string type_name();
+  std::string type_name(const FieldDescriptor* descriptor);
   bool has_default_value();
   bool is_nullable_type();
   std::string default_value();

src/google/protobuf/compiler/csharp/csharp_helpers.cc

@@ -46,6 +46,7 @@
 
 #include <google/protobuf/compiler/csharp/csharp_field_base.h>
 #include <google/protobuf/compiler/csharp/csharp_enum_field.h>
+#include <google/protobuf/compiler/csharp/csharp_map_field.h>
 #include <google/protobuf/compiler/csharp/csharp_message_field.h>
 #include <google/protobuf/compiler/csharp/csharp_primitive_field.h>
 #include <google/protobuf/compiler/csharp/csharp_repeated_enum_field.h>
@@ -355,7 +356,11 @@ FieldGeneratorBase* CreateFieldGenerator(const FieldDescriptor* descriptor,
     case FieldDescriptor::TYPE_GROUP:
     case FieldDescriptor::TYPE_MESSAGE:
       if (descriptor->is_repeated()) {
-        return new RepeatedMessageFieldGenerator(descriptor, fieldOrdinal);
+        if (descriptor->is_map()) {
+          return new MapFieldGenerator(descriptor, fieldOrdinal);
+        } else {
+          return new RepeatedMessageFieldGenerator(descriptor, fieldOrdinal);
+        }
       } else {
 	if (descriptor->containing_oneof()) {
 	  return new MessageOneofFieldGenerator(descriptor, fieldOrdinal);

src/google/protobuf/compiler/csharp/csharp_map_field.cc

+// 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.
+
+#include <sstream>
+
+#include <google/protobuf/compiler/code_generator.h>
+#include <google/protobuf/compiler/plugin.h>
+#include <google/protobuf/descriptor.h>
+#include <google/protobuf/descriptor.pb.h>
+#include <google/protobuf/io/printer.h>
+#include <google/protobuf/io/zero_copy_stream.h>
+#include <google/protobuf/stubs/strutil.h>
+
+#include <google/protobuf/compiler/csharp/csharp_helpers.h>
+#include <google/protobuf/compiler/csharp/csharp_map_field.h>
+
+namespace google {
+namespace protobuf {
+namespace compiler {
+namespace csharp {
+
+MapFieldGenerator::MapFieldGenerator(const FieldDescriptor* descriptor,
+                                             int fieldOrdinal)
+    : FieldGeneratorBase(descriptor, fieldOrdinal) {
+}
+
+MapFieldGenerator::~MapFieldGenerator() {
+}
+
+void MapFieldGenerator::GenerateMembers(io::Printer* printer) {   
+  const FieldDescriptor* key_descriptor =
+      descriptor_->message_type()->FindFieldByName("key");
+  const FieldDescriptor* value_descriptor =
+      descriptor_->message_type()->FindFieldByName("value");
+  variables_["key_type_name"] = type_name(key_descriptor);
+  variables_["value_type_name"] = type_name(value_descriptor);
+  scoped_ptr<FieldGeneratorBase> key_generator(CreateFieldGenerator(key_descriptor, 1));  
+  scoped_ptr<FieldGeneratorBase> value_generator(CreateFieldGenerator(value_descriptor, 2));
+
+  printer->Print(
+    variables_,
+    "private static readonly pbc::MapField<$key_type_name$, $value_type_name$>.Codec _map_$name$_codec\n"
+    "    = new pbc::MapField<$key_type_name$, $value_type_name$>.Codec(");
+  key_generator->GenerateCodecCode(printer);
+  printer->Print(", ");
+  value_generator->GenerateCodecCode(printer);
+  printer->Print(
+    variables_,
+    ", $tag$);\n"
+    "private readonly pbc::MapField<$key_type_name$, $value_type_name$> $name$_ = new pbc::MapField<$key_type_name$, $value_type_name$>();\n");
+  AddDeprecatedFlag(printer);
+  printer->Print(
+    variables_,
+    "public pbc::MapField<$key_type_name$, $value_type_name$> $property_name$ {\n"
+    "  get { return $name$_; }\n"
+    "}\n");
+}
+
+void MapFieldGenerator::GenerateMergingCode(io::Printer* printer) {
+  printer->Print(
+      variables_,
+      "$name$_.Add(other.$name$_);\n");
+}
+
+void MapFieldGenerator::GenerateParsingCode(io::Printer* printer) {
+  printer->Print(
+    variables_,
+    "$name$_.AddEntriesFrom(input, _map_$name$_codec);\n");
+}
+
+void MapFieldGenerator::GenerateSerializationCode(io::Printer* printer) {
+  printer->Print(
+    variables_,
+    "$name$_.WriteTo(output, _map_$name$_codec);\n");
+}
+
+void MapFieldGenerator::GenerateSerializedSizeCode(io::Printer* printer) {
+  printer->Print(
+    variables_,
+    "size += $name$_.CalculateSize(_map_$name$_codec);\n");
+}
+
+void MapFieldGenerator::WriteHash(io::Printer* printer) {
+  printer->Print(
+    variables_,
+    "hash ^= $property_name$.GetHashCode();\n");
+}
+void MapFieldGenerator::WriteEquals(io::Printer* printer) {
+  printer->Print(
+    variables_,
+    "if (!$property_name$.Equals(other.$property_name$)) return false;\n");
+}
+void MapFieldGenerator::WriteToString(io::Printer* printer) {
+    /*
+  variables_["field_name"] = GetFieldName(descriptor_);
+  printer->Print(
+    variables_,
+    "PrintField(\"$field_name$\", has$property_name$, $name$_, writer);\n");*/
+}
+
+void MapFieldGenerator::GenerateCloningCode(io::Printer* printer) {
+  printer->Print(variables_,
+    "$name$_ = other.$name$_.Clone();\n");
+}
+
+void MapFieldGenerator::GenerateFreezingCode(io::Printer* printer) {
+  printer->Print(variables_,
+    "$name$_.Freeze();\n");
+}
+
+}  // namespace csharp
+}  // namespace compiler
+}  // namespace protobuf
+}  // namespace google

src/google/protobuf/compiler/csharp/csharp_map_field.h

+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 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.
+
+#ifndef GOOGLE_PROTOBUF_COMPILER_CSHARP_MAP_FIELD_H__
+#define GOOGLE_PROTOBUF_COMPILER_CSHARP_MAP_FIELD_H__
+
+#include <string>
+
+#include <google/protobuf/compiler/code_generator.h>
+#include <google/protobuf/compiler/csharp/csharp_field_base.h>
+
+namespace google {
+namespace protobuf {
+namespace compiler {
+namespace csharp {
+
+class MapFieldGenerator : public FieldGeneratorBase {
+ public:
+  MapFieldGenerator(const FieldDescriptor* descriptor, int fieldOrdinal);
+  ~MapFieldGenerator();
+
+  virtual void GenerateCloningCode(io::Printer* printer);
+  virtual void GenerateFreezingCode(io::Printer* printer);
+  virtual void GenerateMembers(io::Printer* printer);
+  virtual void GenerateMergingCode(io::Printer* printer);
+  virtual void GenerateParsingCode(io::Printer* printer);
+  virtual void GenerateSerializationCode(io::Printer* printer);
+  virtual void GenerateSerializedSizeCode(io::Printer* printer);
+
+  virtual void WriteHash(io::Printer* printer);
+  virtual void WriteEquals(io::Printer* printer);
+  virtual void WriteToString(io::Printer* printer);
+
+ private:
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(MapFieldGenerator);
+};
+
+}  // namespace csharp
+}  // namespace compiler
+}  // namespace protobuf
+}  // namespace google
+
+#endif  // GOOGLE_PROTOBUF_COMPILER_CSHARP_MAP_FIELD_H__
+

src/google/protobuf/compiler/csharp/csharp_message.cc

@@ -268,8 +268,6 @@ void MessageGenerator::Generate(io::Printer* printer) {
       "}\n\n");
   }
 
-  // TODO(jonskeet): Map properties
-
   // Standard methods
   GenerateFrameworkMethods(printer);
   GenerateMessageSerializationMethods(printer);
@@ -299,7 +297,6 @@ void MessageGenerator::Generate(io::Printer* printer) {
   printer->Outdent();
   printer->Print("}\n");
   printer->Print("\n");
-
 }
 
 void MessageGenerator::GenerateCloningCode(io::Printer* printer) {
@@ -408,9 +405,10 @@ void MessageGenerator::GenerateFrameworkMethods(io::Printer* printer) {
         "}\n\n");
 
     // GetHashCode
+    // Start with a non-zero value to easily distinguish between null and "empty" messages.
     printer->Print(
         "public override int GetHashCode() {\n"
-        "  int hash = 0;\n");
+        "  int hash = 1;\n");
     printer->Indent();
     for (int i = 0; i < descriptor_->field_count(); i++) {
         scoped_ptr<FieldGeneratorBase> generator(
@@ -451,7 +449,7 @@ void MessageGenerator::GenerateMessageSerializationMethods(io::Printer* printer)
   }
   printer->Print("return size;\n");
   printer->Outdent();
-  printer->Print("}\n");
+  printer->Print("}\n\n");
 }
 
 void MessageGenerator::GenerateMergingMethods(io::Printer* printer) {
@@ -469,7 +467,6 @@ void MessageGenerator::GenerateMergingMethods(io::Printer* printer) {
     "if (other == null) {\n"
     "  return;\n"
     "}\n");
-  // TODO(jonskeet): Maps?
   // Merge non-oneof fields
   for (int i = 0; i < descriptor_->field_count(); i++) {
     if (!descriptor_->field(i)->containing_oneof()) {      

src/google/protobuf/compiler/csharp/csharp_message_field.cc

@@ -138,6 +138,12 @@ void MessageFieldGenerator::GenerateFreezingCode(io::Printer* printer) {
     "if ($has_property_check$) $property_name$.Freeze();\n");
 }
 
+void MessageFieldGenerator::GenerateCodecCode(io::Printer* printer) {
+  printer->Print(
+    variables_,
+    "pb::FieldCodec.ForMessage($tag$, $type_name$.Parser)");
+}
+
 MessageOneofFieldGenerator::MessageOneofFieldGenerator(const FieldDescriptor* descriptor,
 						       int fieldOrdinal)
     : MessageFieldGenerator(descriptor, fieldOrdinal) {

src/google/protobuf/compiler/csharp/csharp_message_field.h

@@ -46,6 +46,7 @@ class MessageFieldGenerator : public FieldGeneratorBase {
   MessageFieldGenerator(const FieldDescriptor* descriptor, int fieldOrdinal);
   ~MessageFieldGenerator();
 
+  virtual void GenerateCodecCode(io::Printer* printer);
   virtual void GenerateCloningCode(io::Printer* printer);
   virtual void GenerateFreezingCode(io::Printer* printer);
   virtual void GenerateMembers(io::Printer* printer);

src/google/protobuf/compiler/csharp/csharp_primitive_field.cc

@@ -129,7 +129,7 @@ void PrimitiveFieldGenerator::GenerateSerializedSizeCode(io::Printer* printer) {
       "size += $tag_size$ + $fixed_size$;\n",
       "fixed_size", SimpleItoa(fixedSize),
       "tag_size", variables_["tag_size"]);
-  }    
+  }
   printer->Outdent();
   printer->Print("}\n");
 }
@@ -155,6 +155,12 @@ void PrimitiveFieldGenerator::GenerateCloningCode(io::Printer* printer) {
     "$name$_ = other.$name$_;\n");
 }
 
+void PrimitiveFieldGenerator::GenerateCodecCode(io::Printer* printer) {
+  printer->Print(
+    variables_,
+    "pb::FieldCodec.For$capitalized_type_name$($tag$)");
+}
+
 PrimitiveOneofFieldGenerator::PrimitiveOneofFieldGenerator(
     const FieldDescriptor* descriptor, int fieldOrdinal)
     : PrimitiveFieldGenerator(descriptor, fieldOrdinal) {

src/google/protobuf/compiler/csharp/csharp_primitive_field.h

@@ -46,6 +46,7 @@ class PrimitiveFieldGenerator : public FieldGeneratorBase {
   PrimitiveFieldGenerator(const FieldDescriptor* descriptor, int fieldOrdinal);
   ~PrimitiveFieldGenerator();
 
+  virtual void GenerateCodecCode(io::Printer* printer);
   virtual void GenerateCloningCode(io::Printer* printer);
   virtual void GenerateMembers(io::Printer* printer);
   virtual void GenerateMergingCode(io::Printer* printer);

src/google/protobuf/map_unittest_proto3.proto

+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 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.
+
+// This file is mostly equivalent to map_unittest.proto, but imports
+// unittest_proto3.proto instead of unittest.proto, so that it only
+// uses proto3 messages. This makes it suitable for testing
+// implementations which only support proto3.
+// The TestRequiredMessageMap message has been removed as there are no
+// required fields in proto3.
+syntax = "proto3";
+
+option cc_enable_arenas = true;
+option csharp_namespace = "Google.Protobuf.TestProtos";
+
+import "google/protobuf/unittest_proto3.proto";
+
+// We don't put this in a package within proto2 because we need to make sure
+// that the generated code doesn't depend on being in the proto2 namespace.
+// In map_test_util.h we do "using namespace unittest = protobuf_unittest".
+package protobuf_unittest;
+
+// Tests maps.
+message TestMap {
+  map<int32   , int32   > map_int32_int32       = 1;
+  map<int64   , int64   > map_int64_int64       = 2;
+  map<uint32  , uint32  > map_uint32_uint32     = 3;
+  map<uint64  , uint64  > map_uint64_uint64     = 4;
+  map<sint32  , sint32  > map_sint32_sint32     = 5;
+  map<sint64  , sint64  > map_sint64_sint64     = 6;
+  map<fixed32 , fixed32 > map_fixed32_fixed32   = 7;
+  map<fixed64 , fixed64 > map_fixed64_fixed64   = 8;
+  map<sfixed32, sfixed32> map_sfixed32_sfixed32 = 9;
+  map<sfixed64, sfixed64> map_sfixed64_sfixed64 = 10;
+  map<int32   , float   > map_int32_float       = 11;
+  map<int32   , double  > map_int32_double      = 12;
+  map<bool    , bool    > map_bool_bool         = 13;
+  map<string  , string  > map_string_string     = 14;
+  map<int32   , bytes   > map_int32_bytes       = 15;
+  map<int32   , MapEnum > map_int32_enum        = 16;
+  map<int32   , ForeignMessage> map_int32_foreign_message = 17;
+}
+
+message TestMapSubmessage {
+  TestMap test_map = 1;
+}
+
+message TestMessageMap {
+  map<int32, TestAllTypes> map_int32_message = 1;
+}
+
+// Two map fields share the same entry default instance.
+message TestSameTypeMap {
+  map<int32, int32> map1 = 1;
+  map<int32, int32> map2 = 2;
+}
+
+enum MapEnum {
+  MAP_ENUM_FOO = 0;
+  MAP_ENUM_BAR = 1;
+  MAP_ENUM_BAZ = 2;
+}
+
+message TestArenaMap {
+  map<int32   , int32   > map_int32_int32       = 1;
+  map<int64   , int64   > map_int64_int64       = 2;
+  map<uint32  , uint32  > map_uint32_uint32     = 3;
+  map<uint64  , uint64  > map_uint64_uint64     = 4;
+  map<sint32  , sint32  > map_sint32_sint32     = 5;
+  map<sint64  , sint64  > map_sint64_sint64     = 6;
+  map<fixed32 , fixed32 > map_fixed32_fixed32   = 7;
+  map<fixed64 , fixed64 > map_fixed64_fixed64   = 8;
+  map<sfixed32, sfixed32> map_sfixed32_sfixed32 = 9;
+  map<sfixed64, sfixed64> map_sfixed64_sfixed64 = 10;
+  map<int32   , float   > map_int32_float       = 11;
+  map<int32   , double  > map_int32_double      = 12;
+  map<bool    , bool    > map_bool_bool         = 13;
+  map<int32   , MapEnum > map_int32_enum        = 14;
+  map<int32   , ForeignMessage> map_int32_foreign_message = 15;
+}
+
+// Previously, message containing enum called Type cannot be used as value of
+// map field.
+message MessageContainingEnumCalledType {
+  enum Type {
+    TYPE_FOO = 0;
+  }
+  map<int32, MessageContainingEnumCalledType> type = 1;
+}
+
+// Previously, message cannot contain map field called "entry".
+message MessageContainingMapCalledEntry {
+  map<int32, int32> entry = 1;
+}