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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;
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;
private readonly int sizeLimit;
// Type.EmptyTypes isn't present on the compact framework
private static readonly Type[] EmptyTypes = new Type[0];
/// <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", 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.
/// </summary>
private static Type FindBuilderType() {
MethodInfo createBuilderMethod = typeof(TMessage).GetMethod("CreateBuilder", 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;
}
// This is only ever fetched by reflection, so the compiler may
// complain that it's unused
#pragma warning disable 0169
/// <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();
}
#pragma warning restore 0414
private static readonly uint ExpectedTag = WireFormat.MakeTag(1, WireFormat.WireType.LengthDelimited);
private MessageStreamIterator(StreamProvider streamProvider, ExtensionRegistry extensionRegistry, int sizeLimit) {
if (messageReader == null) {
throw typeInitializationException;
}
this.streamProvider = streamProvider;
this.extensionRegistry = extensionRegistry;
this.sizeLimit = sizeLimit;
}
private MessageStreamIterator(StreamProvider streamProvider, ExtensionRegistry extensionRegistry)
: this (streamProvider, extensionRegistry, CodedInputStream.DefaultSizeLimit) {
}
/// <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, sizeLimit);
}
/// <summary>
/// Creates a new instance which uses the same stream provider and extension registry as this one,
/// but with the specified size limit. Note that this must be big enough for the largest message
/// and the tag and size preceding it.
/// </summary>
public MessageStreamIterator<TMessage> WithSizeLimit(int newSizeLimit) {
return new MessageStreamIterator<TMessage>(streamProvider, extensionRegistry, newSizeLimit);
}
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);
input.SetSizeLimit(sizeLimit);
uint tag;
while ((tag = input.ReadTag()) != 0) {
if (tag != ExpectedTag) {
throw InvalidProtocolBufferException.InvalidMessageStreamTag();
}
yield return messageReader(input, extensionRegistry);
input.ResetSizeCounter();
}
}
}
IEnumerator IEnumerable.GetEnumerator() {
return GetEnumerator();
}
}
}
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