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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;
using System.Collections.Generic;
using System.IO;
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;
/// <summary>
/// The default instance of TMessage type used to construct builders while reading
/// </summary>
private static readonly TMessage defaultMessageInstance = CreateDefaultInstance();
/// <summary>
/// Any exception (within reason) thrown in type ctor is caught and rethrown in the constructor.
/// This makes life a lot simpler for the caller.
/// </summary>
private static Exception typeInitializationException;
/// <summary>
/// Vastly simplified the reflection to simply obtain the default instance and use it to construct
/// the weak builder while simply casting the result. Ideally this class should have required a
/// TBuilder type argument with a new() constraint to construct the initial instance thereby the
/// reflection could be eliminated.
/// </summary>
private static TMessage CreateDefaultInstance()
{
try
{
return (TMessage)typeof(TMessage)
.GetProperty("DefaultInstance", typeof(TMessage), new Type[0])
.GetValue(null, null);
}
catch (Exception e)
{
typeInitializationException = e;
return default(TMessage);
}
}
private static readonly uint ExpectedTag = WireFormat.MakeTag(1, WireFormat.WireType.LengthDelimited);
private MessageStreamIterator(StreamProvider streamProvider, ExtensionRegistry extensionRegistry, int sizeLimit)
{
if (ReferenceEquals(defaultMessageInstance, null))
{
throw new System.Reflection.TargetInvocationException(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);
}
#if CLIENTPROFILE
public static MessageStreamIterator<TMessage> FromFile(string file)
{
return new MessageStreamIterator<TMessage>(() => File.OpenRead(file), ExtensionRegistry.Empty);
}
#endif
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;
string name;
while (input.ReadTag(out tag, out name))
{
if ((tag == 0 && name == "item") || (tag == ExpectedTag))
{
IBuilder builder = defaultMessageInstance.WeakCreateBuilderForType();
input.ReadMessage(builder, extensionRegistry);
yield return (TMessage)builder.WeakBuild();
}
else
{
throw InvalidProtocolBufferException.InvalidMessageStreamTag();
}
input.ResetSizeCounter();
}
}
}
IEnumerator IEnumerable.GetEnumerator()
{
return GetEnumerator();
}
}
}
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