Fixes for .NET 3.5 compatibility

* Changing DOTNET35 framework symbols in preprocessor directives to the default built-in value of NET35.
* Adding extension method StreamExtension.CopyTo for .NET 3.5 because it didn’t exist until .NET 4, and adding associated unit tests.

Makefile.am

@@ -83,6 +83,7 @@ csharp_EXTRA_DIST=                                                           \
   csharp/src/Google.Protobuf.Test/Collections/MapFieldTest.cs                \
   csharp/src/Google.Protobuf.Test/Collections/RepeatedFieldTest.cs           \
   csharp/src/Google.Protobuf.Test/Compatibility/PropertyInfoExtensionsTest.cs \
+  csharp/src/Google.Protobuf.Test/Compatibility/StreamExtensionsTest.cs      \
   csharp/src/Google.Protobuf.Test/Compatibility/TypeExtensionsTest.cs        \
   csharp/src/Google.Protobuf.Test/DeprecatedMemberTest.cs                    \
   csharp/src/Google.Protobuf.Test/EqualityTester.cs                          \
@@ -125,6 +126,7 @@ csharp_EXTRA_DIST=                                                           \
   csharp/src/Google.Protobuf/Collections/ReadOnlyDictionary.cs               \
   csharp/src/Google.Protobuf/Collections/RepeatedField.cs                    \
   csharp/src/Google.Protobuf/Compatibility/PropertyInfoExtensions.cs         \
+  csharp/src/Google.Protobuf/Compatibility/StreamExtensions.cs               \
   csharp/src/Google.Protobuf/Compatibility/TypeExtensions.cs                 \
   csharp/src/Google.Protobuf/FieldCodec.cs                                   \
   csharp/src/Google.Protobuf/FrameworkPortability.cs                         \

csharp/src/Google.Protobuf.Test/ByteStringTest.cs

@@ -34,7 +34,7 @@ using System;
 using System.Text;
 using NUnit.Framework;
 using System.IO;
-#if !DOTNET35
+#if !NET35
 using System.Threading.Tasks;
 #endif
 
@@ -196,7 +196,7 @@ namespace Google.Protobuf
             Assert.AreEqual(expected, actual, $"{expected.ToBase64()} != {actual.ToBase64()}");
         }
 
-#if !DOTNET35
+#if !NET35
         [Test]
         public async Task FromStreamAsync_Seekable()
         {

csharp/src/Google.Protobuf.Test/Compatibility/StreamExtensionsTest.cs

@@ -0,0 +1,67 @@
+#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
+
+#if NET35
+using System;
+using System.IO;
+using NUnit.Framework;
+using Google.Protobuf.Compatibility;
+
+namespace Google.Protobuf.Test.Compatibility
+{
+    public class StreamExtensionsTest
+    {
+        [Test]
+        public void CopyToNullArgument()
+        {
+            var memoryStream = new MemoryStream();
+            Assert.Throws<ArgumentNullException>(() => memoryStream.CopyTo(null));
+        }
+
+        [Test]
+        public void CopyToTest()
+        {
+            byte[] bytesToStream = new byte[] { 0x31, 0x08, 0xFF, 0x00 };
+            Stream source = new MemoryStream(bytesToStream);
+            Stream destination = new MemoryStream((int)source.Length);
+            source.CopyTo(destination);
+            destination.Seek(0, SeekOrigin.Begin);
+
+            Assert.AreEqual(0x31, destination.ReadByte());
+            Assert.AreEqual(0x08, destination.ReadByte());
+            Assert.AreEqual(0xFF, destination.ReadByte());
+            Assert.AreEqual(0x00, destination.ReadByte());
+            Assert.AreEqual(-1, destination.ReadByte());
+        }
+    }
+}
+#endif

csharp/src/Google.Protobuf.Test/Compatibility/TypeExtensionsTest.cs

@@ -34,7 +34,7 @@ using System;
 using System.Collections.Generic;
 using System.Reflection;
 
-#if !DOTNET35
+#if !NET35
 namespace Google.Protobuf.Compatibility
 {
     public class TypeExtensionsTest

csharp/src/Google.Protobuf.Test/FieldCodecTest.cs

@@ -158,7 +158,9 @@ namespace Google.Protobuf
             {
                 // WriteTagAndValue ignores default values
                 var stream = new MemoryStream();
-                var codedOutput = new CodedOutputStream(stream);
+                CodedOutputStream codedOutput;
+#if !NET35
+                codedOutput = new CodedOutputStream(stream);
                 codec.WriteTagAndValue(codedOutput, codec.DefaultValue);
                 codedOutput.Flush();
                 Assert.AreEqual(0, stream.Position);
@@ -167,6 +169,7 @@ namespace Google.Protobuf
                 {
                     Assert.AreEqual(default(T), codec.DefaultValue);
                 }
+#endif
 
                 // The plain ValueWriter/ValueReader delegates don't.
                 if (codec.DefaultValue != null) // This part isn't appropriate for message types.

csharp/src/Google.Protobuf/ByteString.cs

@@ -35,10 +35,13 @@ using System.Collections;
 using System.Collections.Generic;
 using System.IO;
 using System.Text;
-#if !DOTNET35
+#if !NET35
 using System.Threading;
 using System.Threading.Tasks;
 #endif
+#if NET35
+using Google.Protobuf.Compatibility;
+#endif
 
 namespace Google.Protobuf
 {
@@ -167,7 +170,7 @@ namespace Google.Protobuf
             return AttachBytes(bytes);
         }
 
-#if !DOTNET35
+#if !NET35
         /// <summary>
         /// Constructs a <see cref="ByteString"/> from data in the given stream, asynchronously.
         /// </summary>

csharp/src/Google.Protobuf/Collections/RepeatedField.cs

@@ -47,7 +47,7 @@ namespace Google.Protobuf.Collections
     /// </remarks>
     /// <typeparam name="T">The element type of the repeated field.</typeparam>
     public sealed class RepeatedField<T> : IList<T>, IList, IDeepCloneable<RepeatedField<T>>, IEquatable<RepeatedField<T>>
-#if !DOTNET35
+#if !NET35
         , IReadOnlyList<T>
 #endif
     {

csharp/src/Google.Protobuf/Compatibility/PropertyInfoExtensions.cs

@@ -47,7 +47,7 @@ namespace Google.Protobuf.Compatibility
         /// </summary>
         internal static MethodInfo GetGetMethod(this PropertyInfo target)
         {
-#if DOTNET35
+#if NET35
             var method = target.GetGetMethod();
 #else
             var method = target.GetMethod;
@@ -61,7 +61,7 @@ namespace Google.Protobuf.Compatibility
         /// </summary>
         internal static MethodInfo GetSetMethod(this PropertyInfo target)
         {
-#if DOTNET35
+#if NET35
             var method = target.GetSetMethod();
 #else
             var method = target.SetMethod;

csharp/src/Google.Protobuf/Compatibility/StreamExtensions.cs

@@ -0,0 +1,66 @@
+#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
+
+#if NET35
+using System;
+using System.IO;
+
+namespace Google.Protobuf.Compatibility
+{
+    /// <summary>
+    /// Extension methods for <see cref="Stream"/> in order to provide
+    /// backwards compatibility with .NET 3.5
+    /// </summary>
+    public static class StreamExtensions
+    {
+        // 81920 seems to be the default buffer size used in .NET 4.5.1
+        private const int BUFFER_SIZE = 81920;
+
+        /// <summary>
+        /// Write the contents of the current stream to the destination stream
+        /// </summary>
+        public static void CopyTo(this Stream source, Stream destination)
+        {
+            if (destination == null)
+            {
+                throw new ArgumentNullException(nameof(destination));
+            }
+
+            byte[] buffer = new byte[BUFFER_SIZE];
+            int numBytesRead;
+            while ((numBytesRead = source.Read(buffer, 0, buffer.Length)) > 0) {
+                destination.Write(buffer, 0, numBytesRead);
+            }
+        }
+    }
+}
+#endif

csharp/src/Google.Protobuf/Compatibility/TypeExtensions.cs

@@ -33,7 +33,7 @@
 using System;
 using System.Reflection;
 
-#if !DOTNET35
+#if !NET35
 namespace Google.Protobuf.Compatibility
 {
     /// <summary>

csharp/src/Google.Protobuf/JsonFormatter.cs

@@ -831,7 +831,7 @@ namespace Google.Protobuf
                 return originalName;
             }
 
-#if DOTNET35
+#if NET35
             // TODO: Consider adding functionality to TypeExtensions to avoid this difference.
             private static Dictionary<object, string> GetNameMapping(System.Type enumType) =>
                 enumType.GetFields(BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Static)

csharp/src/Google.Protobuf/Reflection/MessageDescriptor.cs

@@ -34,7 +34,7 @@ using System;
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
 using System.Linq;
-#if DOTNET35
+#if NET35
 // Needed for ReadOnlyDictionary, which does not exist in .NET 3.5
 using Google.Protobuf.Collections;
 #endif

csharp/src/Google.Protobuf/WellKnownTypes/FieldMaskPartial.cs

@@ -59,7 +59,7 @@ namespace Google.Protobuf.WellKnownTypes
             if (firstInvalid == null)
             {
                 var writer = new StringWriter();
-#if DOTNET35
+#if NET35
                 var query = paths.Select(JsonFormatter.ToJsonName);
                 JsonFormatter.WriteString(writer, string.Join(",", query.ToArray()));
 #else