1 files changed, 170 insertions, 0 deletions
diff --git a/csharp/src/ProtocolBuffers/MessageStreamIterator.cs b/csharp/src/ProtocolBuffers/MessageStreamIterator.cs
new file mode 100644
index 00000000..32d697ca
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+++ b/csharp/src/ProtocolBuffers/MessageStreamIterator.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;
+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();
+        }
+    }
+}
+\ No newline at end of file