First cut at new layout
diff --git a/src/ProtocolBuffers/ExtendableMessage.cs b/src/ProtocolBuffers/ExtendableMessage.cs
new file mode 100644
index 0000000..a4a6e17
--- /dev/null
+++ b/src/ProtocolBuffers/ExtendableMessage.cs
@@ -0,0 +1,200 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.
+// http://code.google.com/p/protobuf/
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+using System;
+using System.Collections.Generic;
+using Google.ProtocolBuffers.Collections;
+using Google.ProtocolBuffers.Descriptors;
+
+namespace Google.ProtocolBuffers {
+ public abstract class ExtendableMessage<TMessage, TBuilder> : GeneratedMessage<TMessage, TBuilder>
+ where TMessage : GeneratedMessage<TMessage, TBuilder>
+ where TBuilder : GeneratedBuilder<TMessage, TBuilder> {
+
+ protected ExtendableMessage() {}
+ 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>(GeneratedExtensionBase<TExtension> extension) {
+ return extensions.HasField(extension.Descriptor);
+ }
+
+ /// <summary>
+ /// Returns the number of elements in a repeated extension.
+ /// </summary>
+ public int GetExtensionCount<TExtension>(GeneratedExtensionBase<IList<TExtension>> extension) {
+ return extensions.GetRepeatedFieldCount(extension.Descriptor);
+ }
+
+ /// <summary>
+ /// Returns the value of an extension.
+ /// </summary>
+ public TExtension GetExtension<TExtension>(GeneratedExtensionBase<TExtension> extension) {
+ object value = extensions[extension.Descriptor];
+ if (value == null) {
+ return (TExtension) extension.MessageDefaultInstance;
+ } else {
+ return (TExtension) extension.FromReflectionType(value);
+ }
+ }
+
+ /// <summary>
+ /// Returns one element of a repeated extension.
+ /// </summary>
+ public TExtension GetExtension<TExtension>(GeneratedExtensionBase<IList<TExtension>> extension, int index) {
+ return (TExtension) extension.SingularFromReflectionType(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 base.IsInitialized && ExtensionsAreInitialized;
+ }
+ }
+
+ #region Reflection
+ public override IDictionary<FieldDescriptor, object> AllFields {
+ get {
+ IDictionary<FieldDescriptor, object> result = GetMutableFieldMap();
+ foreach(KeyValuePair<FieldDescriptor, object> entry in extensions.AllFields) {
+ result[entry.Key] = entry.Value;
+ }
+ return Dictionaries.AsReadOnly(result);
+ }
+ }
+
+ public override bool HasField(FieldDescriptor field) {
+ if (field.IsExtension) {
+ VerifyContainingType(field);
+ return extensions.HasField(field);
+ } else {
+ return base.HasField(field);
+ }
+ }
+
+ public override object this[FieldDescriptor field] {
+ get {
+ if (field.IsExtension) {
+ VerifyContainingType(field);
+ object value = extensions[field];
+ if (value == null) {
+ // Lacking an ExtensionRegistry, we have no way to determine the
+ // extension's real type, so we return a DynamicMessage.
+ // TODO(jonskeet): Work out what this means
+ return DynamicMessage.GetDefaultInstance(field.MessageType);
+ } else {
+ return value;
+ }
+ } else {
+ return base[field];
+ }
+ }
+ }
+
+ public override int GetRepeatedFieldCount(FieldDescriptor field) {
+ if (field.IsExtension) {
+ VerifyContainingType(field);
+ return extensions.GetRepeatedFieldCount(field);
+ } else {
+ return base.GetRepeatedFieldCount(field);
+ }
+ }
+
+ public override object this[FieldDescriptor field, int index] {
+ get {
+ if (field.IsExtension) {
+ VerifyContainingType(field);
+ return extensions[field, index];
+ } else {
+ return base[field, index];
+ }
+ }
+ }
+
+ internal void VerifyContainingType(FieldDescriptor field) {
+ if (field.ContainingType != DescriptorForType) {
+ throw new ArgumentException("FieldDescriptor does not match message type.");
+ }
+ }
+ #endregion
+
+ /// <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<FieldDescriptor, object>> iterator;
+ readonly FieldSet extensions;
+ KeyValuePair<FieldDescriptor, object>? next = null;
+
+ internal ExtensionWriter(ExtendableMessage<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(ExtendableMessage<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>(GeneratedExtensionBase<TExtension> extension) {
+ if (extension.Descriptor.ContainingType != DescriptorForType) {
+ // This can only happen if someone uses unchecked operations.
+ throw new ArgumentException("Extension is for type \"" + extension.Descriptor.ContainingType.FullName
+ + "\" which does not match message type \"" + DescriptorForType.FullName + "\".");
+ }
+ }
+ }
+}