Full rutime working, Lite generator and runtime building but untested
diff --git a/src/ProtocolBuffers/ExtendableMessageLite.cs b/src/ProtocolBuffers/ExtendableMessageLite.cs
new file mode 100644
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+++ b/src/ProtocolBuffers/ExtendableMessageLite.cs
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+#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc. All rights reserved.
+// http://github.com/jskeet/dotnet-protobufs/
+// Original C++/Java/Python code:
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+// * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+// * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+// * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+
+using System;
+using System.Collections.Generic;
+namespace Google.ProtocolBuffers {
+ public abstract class ExtendableMessageLite<TMessage, TBuilder> : GeneratedMessageLite<TMessage, TBuilder>
+ where TMessage : GeneratedMessageLite<TMessage, TBuilder>
+ where TBuilder : GeneratedBuilderLite<TMessage, TBuilder> {
+
+ protected ExtendableMessageLite() { }
+ private readonly FieldSet extensions = FieldSet.CreateInstance();
+
+ /// <summary>
+ /// Access for the builder.
+ /// </summary>
+ internal FieldSet Extensions {
+ get { return extensions; }
+ }
+
+ /// <summary>
+ /// Checks if a singular extension is present.
+ /// </summary>
+ public bool HasExtension<TExtension>(GeneratedExtensionLite<TMessage, TExtension> extension) {
+ VerifyExtensionContainingType(extension);
+ return extensions.HasField(extension.Descriptor);
+ }
+
+ /// <summary>
+ /// Returns the number of elements in a repeated extension.
+ /// </summary>
+ public int GetExtensionCount<TExtension>(GeneratedExtensionLite<TMessage, IList<TExtension>> extension) {
+ VerifyExtensionContainingType(extension);
+ return extensions.GetRepeatedFieldCount(extension.Descriptor);
+ }
+
+ /// <summary>
+ /// Returns the value of an extension.
+ /// </summary>
+ public TExtension GetExtension<TExtension>(GeneratedExtensionLite<TMessage, TExtension> extension) {
+ VerifyExtensionContainingType(extension);
+ object value = extensions[extension.Descriptor];
+ if (value == null) {
+ return extension.DefaultValue;
+ } else {
+ return (TExtension)value;
+ }
+ }
+
+ /// <summary>
+ /// Returns one element of a repeated extension.
+ /// </summary>
+ public TExtension GetExtension<TExtension>(GeneratedExtensionLite<TMessage, IList<TExtension>> extension, int index) {
+ VerifyExtensionContainingType(extension);
+ return (TExtension)extensions[extension.Descriptor, index];
+ }
+
+ /// <summary>
+ /// Called to check if all extensions are initialized.
+ /// </summary>
+ protected bool ExtensionsAreInitialized {
+ get { return extensions.IsInitialized; }
+ }
+
+ public override bool IsInitialized {
+ get {
+ return ExtensionsAreInitialized;
+ }
+ }
+
+ /// <summary>
+ /// Used by subclasses to serialize extensions. Extension ranges may be
+ /// interleaves with field numbers, but we must write them in canonical
+ /// (sorted by field number) order. This class helps us to write individual
+ /// ranges of extensions at once.
+ ///
+ /// TODO(jonskeet): See if we can improve this in terms of readability.
+ /// </summary>
+ protected class ExtensionWriter {
+ readonly IEnumerator<KeyValuePair<IFieldDescriptorLite, object>> iterator;
+ readonly FieldSet extensions;
+ KeyValuePair<IFieldDescriptorLite, object>? next = null;
+
+ internal ExtensionWriter(ExtendableMessageLite<TMessage, TBuilder> message) {
+ extensions = message.extensions;
+ iterator = message.extensions.GetEnumerator();
+ if (iterator.MoveNext()) {
+ next = iterator.Current;
+ }
+ }
+
+ public void WriteUntil(int end, CodedOutputStream output) {
+ while (next != null && next.Value.Key.FieldNumber < end) {
+ extensions.WriteField(next.Value.Key, next.Value.Value, output);
+ if (iterator.MoveNext()) {
+ next = iterator.Current;
+ } else {
+ next = null;
+ }
+ }
+ }
+ }
+
+ protected ExtensionWriter CreateExtensionWriter(ExtendableMessageLite<TMessage, TBuilder> message) {
+ return new ExtensionWriter(message);
+ }
+
+ /// <summary>
+ /// Called by subclasses to compute the size of extensions.
+ /// </summary>
+ protected int ExtensionsSerializedSize {
+ get { return extensions.SerializedSize; }
+ }
+
+ internal void VerifyExtensionContainingType<TExtension>(GeneratedExtensionLite<TMessage, TExtension> extension) {
+ if (!ReferenceEquals(extension.ContainingTypeDefaultInstance, DefaultInstanceForType)) {
+ // This can only happen if someone uses unchecked operations.
+ throw new ArgumentException(
+ String.Format("Extension is for type \"{0}\" which does not match message type \"{1}\".",
+ extension.ContainingTypeDefaultInstance, DefaultInstanceForType
+ ));
+ }
+ }
+ }
+}