Initial implementation of JSON formatting

- No parsing
- Reflection based, so not hugely efficient
- No line breaks or indentation

csharp/src/ProtocolBuffers.Test/JsonFormatterTest.cs

@@ -0,0 +1,217 @@
+#region Copyright notice and license
+// 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.
+#endregion
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Google.Protobuf.TestProtos;
+using NUnit.Framework;
+
+namespace Google.Protobuf
+{
+    public class JsonFormatterTest
+    {
+        [Test]
+        public void DefaultValues_WhenOmitted()
+        {
+            var formatter = new JsonFormatter(new JsonFormatter.Settings(formatDefaultValues: false));
+
+            Assert.AreEqual("{ }", formatter.Format(new ForeignMessage()));
+            Assert.AreEqual("{ }", formatter.Format(new TestAllTypes()));
+            Assert.AreEqual("{ }", formatter.Format(new TestMap()));
+        }
+
+        [Test]
+        public void DefaultValues_WhenIncluded()
+        {
+            var formatter = new JsonFormatter(new JsonFormatter.Settings(formatDefaultValues: true));
+            Assert.AreEqual("{ \"c\": 0 }", formatter.Format(new ForeignMessage()));
+        }
+
+        [Test]
+        public void AllSingleFields()
+        {
+            var message = new TestAllTypes
+            {
+                SingleBool = true,
+                SingleBytes = ByteString.CopyFrom(1, 2, 3, 4),
+                SingleDouble = 23.5,
+                SingleFixed32 = 23,
+                SingleFixed64 = 1234567890123,
+                SingleFloat = 12.25f,
+                SingleForeignEnum = ForeignEnum.FOREIGN_BAR,
+                SingleForeignMessage = new ForeignMessage { C = 10 },
+                SingleImportEnum = ImportEnum.IMPORT_BAZ,
+                SingleImportMessage = new ImportMessage { D = 20 },
+                SingleInt32 = 100,
+                SingleInt64 = 3210987654321,
+                SingleNestedEnum = TestAllTypes.Types.NestedEnum.FOO,
+                SingleNestedMessage = new TestAllTypes.Types.NestedMessage { Bb = 35 },
+                SinglePublicImportMessage = new PublicImportMessage { E = 54 },
+                SingleSfixed32 = -123,
+                SingleSfixed64 = -12345678901234,
+                SingleSint32 = -456,
+                SingleSint64 = -12345678901235,
+                SingleString = "test\twith\ttabs",
+                SingleUint32 = uint.MaxValue,
+                SingleUint64 = ulong.MaxValue,
+            };
+            var actualText = JsonFormatter.Default.Format(message);
+
+            // Fields in declaration order, which matches numeric order.
+            var expectedText = "{ " +
+                "\"singleInt32\": 100, " +
+                "\"singleInt64\": \"3210987654321\", " +
+                "\"singleUint32\": 4294967295, " +
+                "\"singleUint64\": \"18446744073709551615\", " +
+                "\"singleSint32\": -456, " +
+                "\"singleSint64\": \"-12345678901235\", " +
+                "\"singleFixed32\": 23, " +
+                "\"singleFixed64\": \"1234567890123\", " +
+                "\"singleSfixed32\": -123, " +
+                "\"singleSfixed64\": \"-12345678901234\", " +
+                "\"singleFloat\": 12.25, " +
+                "\"singleDouble\": 23.5, " +
+                "\"singleBool\": true, " +
+                "\"singleString\": \"test\\twith\\ttabs\", " +
+                "\"singleBytes\": \"AQIDBA==\", " +
+                "\"singleNestedMessage\": { \"bb\": 35 }, " +
+                "\"singleForeignMessage\": { \"c\": 10 }, " +
+                "\"singleImportMessage\": { \"d\": 20 }, " +
+                "\"singleNestedEnum\": \"FOO\", " +
+                "\"singleForeignEnum\": \"FOREIGN_BAR\", " +
+                "\"singleImportEnum\": \"IMPORT_BAZ\", " +
+                "\"singlePublicImportMessage\": { \"e\": 54 }" +
+                " }";
+            Assert.AreEqual(expectedText, actualText);
+        }
+
+        [Test]
+        public void RepeatedField()
+        {
+            Assert.AreEqual("{ \"repeatedInt32\": [ 1, 2, 3, 4, 5 ] }",
+                JsonFormatter.Default.Format(new TestAllTypes { RepeatedInt32 = { 1, 2, 3, 4, 5 } }));
+        }
+
+        [Test]
+        public void MapField_StringString()
+        {
+            Assert.AreEqual("{ \"mapStringString\": { \"with spaces\": \"bar\", \"a\": \"b\" } }",
+                JsonFormatter.Default.Format(new TestMap { MapStringString = { { "with spaces", "bar" }, { "a", "b" } } }));
+        }
+
+        [Test]
+        public void MapField_Int32Int32()
+        {
+            // The keys are quoted, but the values aren't.
+            Assert.AreEqual("{ \"mapInt32Int32\": { \"0\": 1, \"2\": 3 } }",
+                JsonFormatter.Default.Format(new TestMap { MapInt32Int32 = { { 0, 1 }, { 2, 3 } } }));
+        }
+
+        [Test]
+        public void MapField_BoolBool()
+        {
+            // The keys are quoted, but the values aren't.
+            Assert.AreEqual("{ \"mapBoolBool\": { \"false\": true, \"true\": false } }",
+                JsonFormatter.Default.Format(new TestMap { MapBoolBool = { { false, true }, { true, false } } }));
+        }
+
+        [TestCase(1.0, "1")]
+        [TestCase(double.NaN, "\"NaN\"")]
+        [TestCase(double.PositiveInfinity, "\"Infinity\"")]
+        [TestCase(double.NegativeInfinity, "\"-Infinity\"")]
+        public void DoubleRepresentations(double value, string expectedValueText)
+        {
+            var message = new TestAllTypes { SingleDouble = value };
+            string actualText = JsonFormatter.Default.Format(message);
+            string expectedText = "{ \"singleDouble\": " + expectedValueText + " }";
+            Assert.AreEqual(expectedText, actualText);
+        }
+
+        [Test]
+        public void UnknownEnumValue()
+        {
+            var message = new TestAllTypes { SingleForeignEnum = (ForeignEnum) 100 };
+            Assert.AreEqual("{ \"singleForeignEnum\": 100 }", JsonFormatter.Default.Format(message));
+        }
+
+        [Test]
+        public void NullValueForMessage()
+        {
+            var message = new TestMap { MapInt32ForeignMessage = { { 10, null } } };
+            Assert.AreEqual("{ \"mapInt32ForeignMessage\": { \"10\": null } }", JsonFormatter.Default.Format(message));
+        }
+
+        [Test]
+        [TestCase("a\u17b4b", "a\\u17b4b")] // Explicit
+        [TestCase("a\u0601b", "a\\u0601b")] // Ranged
+        [TestCase("a\u0605b", "a\u0605b")] // Passthrough (note lack of double backslash...)
+        public void SimpleNonAscii(string text, string encoded)
+        {
+            var message = new TestAllTypes { SingleString = text };
+            Assert.AreEqual("{ \"singleString\": \"" + encoded + "\" }", JsonFormatter.Default.Format(message));
+        }
+
+        [Test]
+        public void SurrogatePairEscaping()
+        {
+            var message = new TestAllTypes { SingleString = "a\uD801\uDC01b" };
+            Assert.AreEqual("{ \"singleString\": \"a\\ud801\\udc01b\" }", JsonFormatter.Default.Format(message));
+        }
+
+        [Test]
+        public void InvalidSurrogatePairsFail()
+        {
+            // Note: don't use TestCase for these, as the strings can't be reliably represented 
+            // See http://codeblog.jonskeet.uk/2014/11/07/when-is-a-string-not-a-string/
+
+            // Lone low surrogate
+            var message = new TestAllTypes { SingleString = "a\uDC01b" };
+            Assert.Throws<ArgumentException>(() => JsonFormatter.Default.Format(message));
+
+            // Lone high surrogate
+            message = new TestAllTypes { SingleString = "a\uD801b" };
+            Assert.Throws<ArgumentException>(() => JsonFormatter.Default.Format(message));
+        }
+
+        [Test]
+        [TestCase("foo_bar", "fooBar")]
+        [TestCase("bananaBanana", "bananaBanana")]
+        [TestCase("BANANABanana", "bananaBanana")]
+        public void ToCamelCase(string original, string expected)
+        {
+            Assert.AreEqual(expected, JsonFormatter.ToCamelCase(original));
+        }
+    }
+}

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

@@ -80,6 +80,7 @@
     <Compile Include="GeneratedMessageTest.cs" />
     <Compile Include="Collections\MapFieldTest.cs" />
     <Compile Include="Collections\RepeatedFieldTest.cs" />
+    <Compile Include="JsonFormatterTest.cs" />
     <Compile Include="SampleEnum.cs" />
     <Compile Include="SampleMessages.cs" />
     <Compile Include="TestProtos\MapUnittestProto3.cs" />

csharp/src/ProtocolBuffers/Descriptors/EnumDescriptor.cs

@@ -89,6 +89,7 @@ namespace Google.Protobuf.Descriptors
         /// <summary>
         /// Finds an enum value by number. If multiple enum values have the
         /// same number, this returns the first defined value with that number.
+        /// If there is no value for the given number, this returns <c>null</c>.
         /// </summary>
         public EnumValueDescriptor FindValueByNumber(int number)
         {

csharp/src/ProtocolBuffers/FieldAccess/IFieldAccessor.cs

@@ -44,6 +44,8 @@ namespace Google.Protobuf.FieldAccess
         /// </summary>
         FieldDescriptor Descriptor { get; }
 
+        // TODO: Should the argument type for these messages by IReflectedMessage?
+
         /// <summary>
         /// Clears the field in the specified message. (For repeated fields,
         /// this clears the list.)

csharp/src/ProtocolBuffers/IMessage.cs

@@ -40,9 +40,9 @@ namespace Google.Protobuf
     // TODO(jonskeet): Split these interfaces into separate files when we're happy with them.
 
     /// <summary>
-    /// Reflection support for a specific message type.
+    /// Reflection support for accessing field values.
     /// </summary>
-    public interface IReflectedMessage
+    public interface IReflectedMessage : IMessage
     {
         FieldAccessorTable Fields { get; }
         // TODO(jonskeet): Descriptor? Or a single property which has "all you need for reflection"?
@@ -81,7 +81,7 @@ namespace Google.Protobuf
     /// the implementation class.
     /// </summary>
     /// <typeparam name="T">The message type.</typeparam>
-    public interface IMessage<T> : IMessage, IEquatable<T>, IDeepCloneable<T>, IFreezable where T : IMessage<T>
+    public interface IMessage<T> : IReflectedMessage, IEquatable<T>, IDeepCloneable<T>, IFreezable where T : IMessage<T>
     {
         /// <summary>
         /// Merges the given message into this one.

csharp/src/ProtocolBuffers/JsonFormatter.cs

@@ -0,0 +1,521 @@
+#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;
+using System.Globalization;
+using System.Text;
+using Google.Protobuf.Descriptors;
+using Google.Protobuf.FieldAccess;
+
+namespace Google.Protobuf
+{
+    /// <summary>
+    /// Reflection-based converter from messages to JSON.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// Instances of this class are thread-safe, with no mutable state.
+    /// </para>
+    /// <para>
+    /// This is a simple start to get JSON formatting working. As it's reflection-based,
+    /// it's not as quick as baking calls into generated messages - but is a simpler implementation.
+    /// (This code is generally not heavily optimized.)
+    /// </para>
+    /// </remarks>
+    public sealed class JsonFormatter
+    {
+        private static JsonFormatter defaultInstance = new JsonFormatter(Settings.Default);
+
+        /// <summary>
+        /// Returns a formatter using the default settings.
+        /// </summary>
+        public static JsonFormatter Default { get { return defaultInstance; } }
+
+        /// <summary>
+        /// The JSON representation of the first 160 characters of Unicode.
+        /// Empty strings are replaced by the static constructor.
+        /// </summary>
+        private static readonly string[] CommonRepresentations = {
+            // C0 (ASCII and derivatives) control characters
+            "\\u0000", "\\u0001", "\\u0002", "\\u0003",  // 0x00
+          "\\u0004", "\\u0005", "\\u0006", "\\u0007",
+          "\\b",     "\\t",     "\\n",     "\\u000b",
+          "\\f",     "\\r",     "\\u000e", "\\u000f",
+          "\\u0010", "\\u0011", "\\u0012", "\\u0013",  // 0x10
+          "\\u0014", "\\u0015", "\\u0016", "\\u0017",
+          "\\u0018", "\\u0019", "\\u001a", "\\u001b",
+          "\\u001c", "\\u001d", "\\u001e", "\\u001f",
+            // Escaping of " and \ are required by www.json.org string definition.
+            // Escaping of < and > are required for HTML security.
+            "", "", "\\\"", "", "",        "", "",        "",  // 0x20
+          "", "", "",     "", "",        "", "",        "",
+          "", "", "",     "", "",        "", "",        "",  // 0x30
+          "", "", "",     "", "\\u003c", "", "\\u003e", "",
+          "", "", "",     "", "",        "", "",        "",  // 0x40
+          "", "", "",     "", "",        "", "",        "",
+          "", "", "",     "", "",        "", "",        "",  // 0x50
+          "", "", "",     "", "\\\\",    "", "",        "",
+          "", "", "",     "", "",        "", "",        "",  // 0x60
+          "", "", "",     "", "",        "", "",        "",
+          "", "", "",     "", "",        "", "",        "",  // 0x70
+          "", "", "",     "", "",        "", "",        "\\u007f",
+            // C1 (ISO 8859 and Unicode) extended control characters
+            "\\u0080", "\\u0081", "\\u0082", "\\u0083",  // 0x80
+          "\\u0084", "\\u0085", "\\u0086", "\\u0087",
+          "\\u0088", "\\u0089", "\\u008a", "\\u008b",
+          "\\u008c", "\\u008d", "\\u008e", "\\u008f",
+          "\\u0090", "\\u0091", "\\u0092", "\\u0093",  // 0x90
+          "\\u0094", "\\u0095", "\\u0096", "\\u0097",
+          "\\u0098", "\\u0099", "\\u009a", "\\u009b",
+          "\\u009c", "\\u009d", "\\u009e", "\\u009f"
+        };
+
+        static JsonFormatter()
+        {
+            for (int i = 0; i < CommonRepresentations.Length; i++)
+            {
+                if (CommonRepresentations[i] == "")
+                {
+                    CommonRepresentations[i] = ((char) i).ToString();
+                }
+            }
+        }
+
+        private readonly Settings settings;
+
+        public JsonFormatter(Settings settings)
+        {
+            this.settings = settings;
+        }
+
+        public string Format(IReflectedMessage message)
+        {
+            ThrowHelper.ThrowIfNull(message, "message");
+            StringBuilder builder = new StringBuilder();
+            WriteMessage(builder, message);
+            return builder.ToString();
+        }
+
+        private void WriteMessage(StringBuilder builder, IReflectedMessage message)
+        {
+            if (message == null)
+            {
+                WriteNull(builder);
+                return;
+            }
+            builder.Append("{ ");
+            var fields = message.Fields;
+            bool first = true;
+            foreach (var accessor in fields.Accessors)
+            {
+                object value = accessor.GetValue(message);
+                if (!settings.FormatDefaultValues && IsDefaultValue(accessor, value))
+                {
+                    continue;
+                }
+                if (!first)
+                {
+                    builder.Append(", ");
+                }
+                WriteString(builder, ToCamelCase(accessor.Descriptor.Name));
+                builder.Append(": ");
+                WriteValue(builder, accessor, value);
+                first = false;
+            }
+            builder.Append(first ? "}" : " }");
+        }
+
+        // Converted from src/google/protobuf/util/internal/utility.cc ToCamelCase
+        internal static string ToCamelCase(string input)
+        {
+            bool capitalizeNext = false;
+            bool wasCap = true;
+            bool isCap = false;
+            bool firstWord = true;
+            StringBuilder result = new StringBuilder(input.Length);
+
+            for (int i = 0; i < input.Length; i++, wasCap = isCap)
+            {
+                isCap = char.IsUpper(input[i]);
+                if (input[i] == '_')
+                {
+                    capitalizeNext = true;
+                    if (result.Length != 0)
+                    {
+                        firstWord = false;
+                    }
+                    continue;
+                }
+                else if (firstWord)
+                {
+                    // Consider when the current character B is capitalized,
+                    // first word ends when:
+                    // 1) following a lowercase:   "...aB..."
+                    // 2) followed by a lowercase: "...ABc..."
+                    if (result.Length != 0 && isCap &&
+                        (!wasCap || (i + 1 < input.Length && char.IsLower(input[i + 1]))))
+                    {
+                        firstWord = false;
+                    }
+                    else
+                    {
+                        result.Append(char.ToLowerInvariant(input[i]));
+                        continue;
+                    }
+                }
+                else if (capitalizeNext)
+                {
+                    capitalizeNext = false;
+                    if (char.IsLower(input[i]))
+                    {
+                        result.Append(char.ToUpperInvariant(input[i]));
+                        continue;
+                    }
+                }
+                result.Append(input[i]);
+            }
+            return result.ToString();
+        }
+        
+        private static void WriteNull(StringBuilder builder)
+        {
+            builder.Append("null");
+        }
+
+        private static bool IsDefaultValue(IFieldAccessor accessor, object value)
+        {
+            if (accessor.Descriptor.IsMap)
+            {
+                IDictionary dictionary = (IDictionary) value;
+                return dictionary.Count == 0;
+            }
+            if (accessor.Descriptor.IsRepeated)
+            {
+                IList list = (IList) value;
+                return list.Count == 0;
+            }
+            switch (accessor.Descriptor.FieldType)
+            {
+                case FieldType.Bool:
+                    return (bool) value == false;
+                case FieldType.Bytes:
+                    return (ByteString) value == ByteString.Empty;
+                case FieldType.String:
+                    return (string) value == "";
+                case FieldType.Double:
+                    return (double) value == 0.0;
+                case FieldType.SInt32:
+                case FieldType.Int32:
+                case FieldType.SFixed32:
+                case FieldType.Enum:
+                    return (int) value == 0;
+                case FieldType.Fixed32:
+                case FieldType.UInt32:
+                    return (uint) value == 0;
+                case FieldType.Fixed64:
+                case FieldType.UInt64:
+                    return (ulong) value == 0;
+                case FieldType.SFixed64:
+                case FieldType.Int64:
+                case FieldType.SInt64:
+                    return (long) value == 0;
+                case FieldType.Float:
+                    return (float) value == 0f;
+                case FieldType.Message:
+                case FieldType.Group: // Never expect to get this, but...
+                    return value == null;
+                default:
+                    throw new ArgumentException("Invalid field type");
+            }
+        }
+
+        private void WriteValue(StringBuilder builder, IFieldAccessor accessor, object value)
+        {
+            if (accessor.Descriptor.IsMap)
+            {
+                WriteDictionary(builder, accessor, (IDictionary) value);
+            }
+            else if (accessor.Descriptor.IsRepeated)
+            {
+                WriteList(builder, accessor, (IList) value);
+            }
+            else
+            {
+                WriteSingleValue(builder, accessor.Descriptor, value);
+            }
+        }
+
+        private void WriteSingleValue(StringBuilder builder, FieldDescriptor descriptor, object value)
+        {
+            switch (descriptor.FieldType)
+            {
+                case FieldType.Bool:
+                    builder.Append((bool) value ? "true" : "false");
+                    break;
+                case FieldType.Bytes:
+                    // Nothing in Base64 needs escaping
+                    builder.Append('"');
+                    builder.Append(((ByteString) value).ToBase64());
+                    builder.Append('"');
+                    break;
+                case FieldType.String:
+                    WriteString(builder, (string) value);
+                    break;
+                case FieldType.Fixed32:
+                case FieldType.UInt32:
+                case FieldType.SInt32:
+                case FieldType.Int32:
+                case FieldType.SFixed32:
+                    {
+                        IFormattable formattable = (IFormattable) value;
+                        builder.Append(formattable.ToString("d", CultureInfo.InvariantCulture));
+                        break;
+                    }
+                case FieldType.Enum:
+                    EnumValueDescriptor enumValue = descriptor.EnumType.FindValueByNumber((int) value);
+                    if (enumValue != null)
+                    {
+                        WriteString(builder, enumValue.Name);
+                    }
+                    else
+                    {
+                        // ??? Need more documentation
+                        builder.Append(((int) value).ToString("d", CultureInfo.InvariantCulture));
+                    }
+                    break;
+                case FieldType.Fixed64:
+                case FieldType.UInt64:
+                case FieldType.SFixed64:
+                case FieldType.Int64:
+                case FieldType.SInt64:
+                    {
+                        builder.Append('"');
+                        IFormattable formattable = (IFormattable) value;
+                        builder.Append(formattable.ToString("d", CultureInfo.InvariantCulture));
+                        builder.Append('"');
+                        break;
+                    }
+                case FieldType.Double:
+                case FieldType.Float:
+                    string text = ((IFormattable) value).ToString("r", CultureInfo.InvariantCulture);
+                    if (text == "NaN" || text == "Infinity" || text == "-Infinity")
+                    {
+                        builder.Append('"');
+                        builder.Append(text);
+                        builder.Append('"');
+                    }
+                    else
+                    {
+                        builder.Append(text);
+                    }
+                    break;
+                case FieldType.Message:
+                case FieldType.Group: // Never expect to get this, but...
+                    WriteMessage(builder, (IReflectedMessage) value);
+                    break;
+                default:
+                    throw new ArgumentException("Invalid field type: " + descriptor.FieldType);
+            }
+        }
+
+        private void WriteList(StringBuilder builder, IFieldAccessor accessor, IList list)
+        {
+            builder.Append("[ ");
+            bool first = true;
+            foreach (var value in list)
+            {
+                if (!first)
+                {
+                    builder.Append(", ");
+                }
+                WriteSingleValue(builder, accessor.Descriptor, value);
+                first = false;
+            }
+            builder.Append(first ? "]" : " ]");
+        }
+
+        private void WriteDictionary(StringBuilder builder, IFieldAccessor accessor, IDictionary dictionary)
+        {
+            builder.Append("{ ");
+            bool first = true;
+            FieldDescriptor keyType = accessor.Descriptor.MessageType.FindFieldByNumber(1);
+            FieldDescriptor valueType = accessor.Descriptor.MessageType.FindFieldByNumber(2);
+            // This will box each pair. Could use IDictionaryEnumerator, but that's ugly in terms of disposal.
+            foreach (DictionaryEntry pair in dictionary)
+            {
+                if (!first)
+                {
+                    builder.Append(", ");
+                }
+                string keyText;
+                switch (keyType.FieldType)
+                {
+                    case FieldType.String:
+                        keyText = (string) pair.Key;
+                        break;
+                    case FieldType.Bool:
+                        keyText = (bool) pair.Key ? "true" : "false";
+                        break;
+                    case FieldType.Fixed32:
+                    case FieldType.Fixed64:
+                    case FieldType.SFixed32:
+                    case FieldType.SFixed64:
+                    case FieldType.Int32:
+                    case FieldType.Int64:
+                    case FieldType.SInt32:
+                    case FieldType.SInt64:
+                    case FieldType.UInt32:
+                    case FieldType.UInt64:
+                        keyText = ((IFormattable) pair.Key).ToString("d", CultureInfo.InvariantCulture);
+                        break;
+                    default:
+                        throw new ArgumentException("Invalid key type: " + keyType.FieldType);
+                }
+                WriteString(builder, keyText);
+                builder.Append(": ");
+                WriteSingleValue(builder, valueType, pair.Value);
+                first = false;
+            }
+            builder.Append(first ? "}" : " }");
+        }
+
+        /// <summary>
+        /// Writes a string (including leading and trailing double quotes) to a builder, escaping as required.
+        /// </summary>
+        /// <remarks>
+        /// Other than surrogate pair handling, this code is mostly taken from src/google/protobuf/util/internal/json_escaping.cc.
+        /// </remarks>
+        private void WriteString(StringBuilder builder, string text)
+        {
+            builder.Append('"');
+            for (int i = 0; i < text.Length; i++)
+            {
+                char c = text[i];
+                if (c < 0xa0)
+                {
+                    builder.Append(CommonRepresentations[c]);
+                    continue;
+                }
+                if (char.IsHighSurrogate(c))
+                {
+                    // Encountered first part of a surrogate pair.
+                    // Check that we have the whole pair, and encode both parts as hex.
+                    i++;
+                    if (i == text.Length || !char.IsLowSurrogate(text[i]))
+                    {
+                        throw new ArgumentException("String contains low surrogate not followed by high surrogate");
+                    }
+                    HexEncodeUtf16CodeUnit(builder, c);
+                    HexEncodeUtf16CodeUnit(builder, text[i]);
+                    continue;
+                }
+                else if (char.IsLowSurrogate(c))
+                {
+                    throw new ArgumentException("String contains high surrogate not preceded by low surrogate");
+                }
+                switch ((uint) c)
+                {
+                    // These are not required by json spec
+                    // but used to prevent security bugs in javascript.
+                    case 0xfeff:  // Zero width no-break space
+                    case 0xfff9:  // Interlinear annotation anchor
+                    case 0xfffa:  // Interlinear annotation separator
+                    case 0xfffb:  // Interlinear annotation terminator
+
+                    case 0x00ad:  // Soft-hyphen
+                    case 0x06dd:  // Arabic end of ayah
+                    case 0x070f:  // Syriac abbreviation mark
+                    case 0x17b4:  // Khmer vowel inherent Aq
+                    case 0x17b5:  // Khmer vowel inherent Aa
+                        HexEncodeUtf16CodeUnit(builder, c);
+                        break;
+
+                    default:
+                        if ((c >= 0x0600 && c <= 0x0603) ||  // Arabic signs
+                            (c >= 0x200b && c <= 0x200f) ||  // Zero width etc.
+                            (c >= 0x2028 && c <= 0x202e) ||  // Separators etc.
+                            (c >= 0x2060 && c <= 0x2064) ||  // Invisible etc.
+                            (c >= 0x206a && c <= 0x206f))
+                        {
+                            HexEncodeUtf16CodeUnit(builder, c);
+                        }
+                        else
+                        {
+                            // No handling of surrogates here - that's done earlier
+                            builder.Append(c);
+                        }
+                        break;
+                }
+            }
+            builder.Append('"');
+        }
+
+        private const string Hex = "0123456789abcdef";
+        private static void HexEncodeUtf16CodeUnit(StringBuilder builder, char c)
+        {
+            uint utf16 = c;
+            builder.Append("\\u");
+            builder.Append(Hex[(c >> 12) & 0xf]);
+            builder.Append(Hex[(c >> 8) & 0xf]);
+            builder.Append(Hex[(c >> 4) & 0xf]);
+            builder.Append(Hex[(c >> 0) & 0xf]);
+        }
+
+        /// <summary>
+        /// Settings controlling JSON formatting.
+        /// </summary>
+        public sealed class Settings
+        {
+            private static readonly Settings defaultInstance = new Settings(false);
+
+            /// <summary>
+            /// Default settings, as used by <see cref="JsonFormatter.Default"/>
+            /// </summary>
+            public static Settings Default { get { return defaultInstance; } }
+
+            private readonly bool formatDefaultValues;
+
+
+            /// <summary>
+            /// Whether fields whose values are the default for the field type (e.g. 0 for integers)
+            /// should be formatted (true) or omitted (false).
+            /// </summary>
+            public bool FormatDefaultValues { get { return formatDefaultValues; } }
+
+            public Settings(bool formatDefaultValues)
+            {
+                this.formatDefaultValues = formatDefaultValues;
+            }
+        }
+    }
+}

csharp/src/ProtocolBuffers/ProtocolBuffers.csproj

@@ -81,6 +81,7 @@
     <Compile Include="FieldCodec.cs" />
     <Compile Include="FrameworkPortability.cs" />
     <Compile Include="Freezable.cs" />
+    <Compile Include="JsonFormatter.cs" />
     <Compile Include="MessageExtensions.cs" />
     <Compile Include="FieldAccess\FieldAccessorBase.cs" />
     <Compile Include="FieldAccess\ReflectionUtil.cs" />