First cut at new layout
diff --git a/src/ProtocolBuffers/MessageStreamIterator.cs b/src/ProtocolBuffers/MessageStreamIterator.cs
new file mode 100644
index 0000000..61dbf84
--- /dev/null
+++ b/src/ProtocolBuffers/MessageStreamIterator.cs
@@ -0,0 +1,150 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using System.Collections;
+using System.IO;
+using System.Reflection;
+
+namespace Google.ProtocolBuffers {
+
+ /// <summary>
+ /// Iterates over data created using a <see cref="MessageStreamWriter{T}" />.
+ /// Unlike MessageStreamWriter, this class is not usually constructed directly with
+ /// a stream; instead it is provided with a way of opening a stream when iteration
+ /// is started. The stream is closed when the iteration is completed or the enumerator
+ /// is disposed. (This occurs naturally when using <c>foreach</c>.)
+ /// </summary>
+ public class MessageStreamIterator<TMessage> : IEnumerable<TMessage>
+ where TMessage : IMessage<TMessage> {
+
+ private readonly StreamProvider streamProvider;
+ private readonly ExtensionRegistry extensionRegistry;
+
+ /// <summary>
+ /// Delegate created via reflection trickery (once per type) to create a builder
+ /// and read a message from a CodedInputStream with it. Note that unlike in Java,
+ /// there's one static field per constructed type.
+ /// </summary>
+ private static readonly Func<CodedInputStream, ExtensionRegistry, TMessage> messageReader = BuildMessageReader();
+
+ /// <summary>
+ /// Any exception (within reason) thrown within messageReader is caught and rethrown in the constructor.
+ /// This makes life a lot simpler for the caller.
+ /// </summary>
+ private static Exception typeInitializationException;
+
+ /// <summary>
+ /// Creates the delegate later used to read messages. This is only called once per type, but to
+ /// avoid exceptions occurring at confusing times, if this fails it will set typeInitializationException
+ /// to the appropriate error and return null.
+ /// </summary>
+ private static Func<CodedInputStream, ExtensionRegistry, TMessage> BuildMessageReader() {
+ try {
+ Type builderType = FindBuilderType();
+
+ // Yes, it's redundant to find this again, but it's only the once...
+ MethodInfo createBuilderMethod = typeof(TMessage).GetMethod("CreateBuilder", Type.EmptyTypes);
+ Delegate builderBuilder = Delegate.CreateDelegate(
+ typeof(Func<>).MakeGenericType(builderType), null, createBuilderMethod);
+
+ MethodInfo buildMethod = typeof(MessageStreamIterator<TMessage>)
+ .GetMethod("BuildImpl", BindingFlags.Static | BindingFlags.NonPublic)
+ .MakeGenericMethod(typeof(TMessage), builderType);
+
+ return (Func<CodedInputStream, ExtensionRegistry, TMessage>)Delegate.CreateDelegate(
+ typeof(Func<CodedInputStream, ExtensionRegistry, TMessage>), builderBuilder, buildMethod);
+ } catch (ArgumentException e) {
+ typeInitializationException = e;
+ } catch (InvalidOperationException e) {
+ typeInitializationException = e;
+ } catch (InvalidCastException e) {
+ // Can't see why this would happen, but best to know about it.
+ typeInitializationException = e;
+ }
+ return null;
+ }
+
+ /// <summary>
+ /// Works out the builder type for TMessage, or throws an ArgumentException to explain why it can't.
+ /// This will check
+ /// </summary>
+ private static Type FindBuilderType() {
+ MethodInfo createBuilderMethod = typeof(TMessage).GetMethod("CreateBuilder", Type.EmptyTypes);
+ if (createBuilderMethod == null) {
+ throw new ArgumentException("Message type " + typeof(TMessage).FullName + " has no CreateBuilder method.");
+ }
+ if (createBuilderMethod.ReturnType == typeof(void)) {
+ throw new ArgumentException("CreateBuilder method in " + typeof(TMessage).FullName + " has void return type");
+ }
+ Type builderType = createBuilderMethod.ReturnType;
+ Type messageInterface = typeof(IMessage<,>).MakeGenericType(typeof(TMessage), builderType);
+ Type builderInterface = typeof(IBuilder<,>).MakeGenericType(typeof(TMessage), builderType);
+ if (Array.IndexOf(typeof(TMessage).GetInterfaces(), messageInterface) == -1) {
+ throw new ArgumentException("Message type " + typeof(TMessage) + " doesn't implement " + messageInterface.FullName);
+ }
+ if (Array.IndexOf(builderType.GetInterfaces(), builderInterface) == -1) {
+ throw new ArgumentException("Builder type " + typeof(TMessage) + " doesn't implement " + builderInterface.FullName);
+ }
+ return builderType;
+ }
+
+ /// <summary>
+ /// Method we'll use to build messageReader, with the first parameter fixed to TMessage.CreateBuilder. Note that we
+ /// have to introduce another type parameter (TMessage2) as we can't constrain TMessage for just a single method
+ /// (and we can't do it at the type level because we don't know TBuilder). However, by constraining TMessage2
+ /// to not only implement IMessage appropriately but also to derive from TMessage2, we can avoid doing a cast
+ /// for every message; the implicit reference conversion will be fine. In practice, TMessage2 and TMessage will
+ /// be the same type when we construct the generic method by reflection.
+ /// </summary>
+ private static TMessage BuildImpl<TMessage2, TBuilder>(Func<TBuilder> builderBuilder, CodedInputStream input, ExtensionRegistry registry)
+ where TBuilder : IBuilder<TMessage2, TBuilder>
+ where TMessage2 : TMessage, IMessage<TMessage2, TBuilder> {
+ TBuilder builder = builderBuilder();
+ input.ReadMessage(builder, registry);
+ return builder.Build();
+ }
+
+ private static readonly uint ExpectedTag = WireFormat.MakeTag(1, WireFormat.WireType.LengthDelimited);
+
+ private MessageStreamIterator(StreamProvider streamProvider, ExtensionRegistry extensionRegistry) {
+ if (messageReader == null) {
+ throw typeInitializationException;
+ }
+ this.streamProvider = streamProvider;
+ this.extensionRegistry = extensionRegistry;
+ }
+
+ /// <summary>
+ /// Creates a new instance which uses the same stream provider as this one,
+ /// but the specified extension registry.
+ /// </summary>
+ public MessageStreamIterator<TMessage> WithExtensionRegistry(ExtensionRegistry newRegistry) {
+ return new MessageStreamIterator<TMessage>(streamProvider, newRegistry);
+ }
+
+ public static MessageStreamIterator<TMessage> FromFile(string file) {
+ return new MessageStreamIterator<TMessage>(() => File.OpenRead(file), ExtensionRegistry.Empty);
+ }
+
+ public static MessageStreamIterator<TMessage> FromStreamProvider(StreamProvider streamProvider) {
+ return new MessageStreamIterator<TMessage>(streamProvider, ExtensionRegistry.Empty);
+ }
+
+ public IEnumerator<TMessage> GetEnumerator() {
+ using (Stream stream = streamProvider()) {
+ CodedInputStream input = CodedInputStream.CreateInstance(stream);
+ uint tag;
+ while ((tag = input.ReadTag()) != 0) {
+ if (tag != ExpectedTag) {
+ throw InvalidProtocolBufferException.InvalidMessageStreamTag();
+ }
+ yield return messageReader(input, extensionRegistry);
+ }
+ }
+ }
+
+ IEnumerator IEnumerable.GetEnumerator() {
+ return GetEnumerator();
+ }
+ }
+}