[8295] | 1 | #region Copyright notice and license
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| 2 |
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| 3 | // Protocol Buffers - Google's data interchange format
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| 4 | // Copyright 2008 Google Inc. All rights reserved.
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| 5 | // http://github.com/jskeet/dotnet-protobufs/
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| 6 | // Original C++/Java/Python code:
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| 7 | // http://code.google.com/p/protobuf/
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| 8 | //
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| 9 | // Redistribution and use in source and binary forms, with or without
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| 10 | // modification, are permitted provided that the following conditions are
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| 11 | // met:
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| 12 | //
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| 13 | // * Redistributions of source code must retain the above copyright
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| 14 | // notice, this list of conditions and the following disclaimer.
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| 15 | // * Redistributions in binary form must reproduce the above
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| 16 | // copyright notice, this list of conditions and the following disclaimer
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| 17 | // in the documentation and/or other materials provided with the
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| 18 | // distribution.
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| 19 | // * Neither the name of Google Inc. nor the names of its
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| 20 | // contributors may be used to endorse or promote products derived from
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| 21 | // this software without specific prior written permission.
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| 22 | //
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| 23 | // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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| 24 | // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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| 25 | // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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| 26 | // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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| 27 | // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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| 28 | // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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| 29 | // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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| 30 | // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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| 31 | // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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| 32 | // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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| 33 | // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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| 34 |
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| 35 | #endregion
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| 36 |
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| 37 | using System;
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| 38 | using System.Collections;
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| 39 | using System.Collections.Generic;
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| 40 | using System.IO;
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| 41 | using System.Reflection;
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| 42 |
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| 43 | namespace Google.ProtocolBuffers
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| 44 | {
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| 45 | /// <summary>
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| 46 | /// Iterates over data created using a <see cref="MessageStreamWriter{T}" />.
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| 47 | /// Unlike MessageStreamWriter, this class is not usually constructed directly with
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| 48 | /// a stream; instead it is provided with a way of opening a stream when iteration
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| 49 | /// is started. The stream is closed when the iteration is completed or the enumerator
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| 50 | /// is disposed. (This occurs naturally when using <c>foreach</c>.)
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| 51 | /// </summary>
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| 52 | public class MessageStreamIterator<TMessage> : IEnumerable<TMessage>
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| 53 | where TMessage : IMessage<TMessage>
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| 54 | {
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| 55 | private readonly StreamProvider streamProvider;
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| 56 | private readonly ExtensionRegistry extensionRegistry;
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| 57 | private readonly int sizeLimit;
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| 58 |
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| 59 | // Type.EmptyTypes isn't present on the compact framework
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| 60 | private static readonly Type[] EmptyTypes = new Type[0];
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| 61 |
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| 62 | /// <summary>
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| 63 | /// Delegate created via reflection trickery (once per type) to create a builder
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| 64 | /// and read a message from a CodedInputStream with it. Note that unlike in Java,
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| 65 | /// there's one static field per constructed type.
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| 66 | /// </summary>
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| 67 | private static readonly Func<CodedInputStream, ExtensionRegistry, TMessage> messageReader = BuildMessageReader();
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| 68 |
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| 69 | /// <summary>
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| 70 | /// Any exception (within reason) thrown within messageReader is caught and rethrown in the constructor.
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| 71 | /// This makes life a lot simpler for the caller.
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| 72 | /// </summary>
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| 73 | private static Exception typeInitializationException;
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| 74 |
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| 75 | /// <summary>
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| 76 | /// Creates the delegate later used to read messages. This is only called once per type, but to
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| 77 | /// avoid exceptions occurring at confusing times, if this fails it will set typeInitializationException
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| 78 | /// to the appropriate error and return null.
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| 79 | /// </summary>
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| 80 | private static Func<CodedInputStream, ExtensionRegistry, TMessage> BuildMessageReader()
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| 81 | {
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| 82 | try
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| 83 | {
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| 84 | Type builderType = FindBuilderType();
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| 85 |
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| 86 | // Yes, it's redundant to find this again, but it's only the once...
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| 87 | MethodInfo createBuilderMethod = typeof (TMessage).GetMethod("CreateBuilder", EmptyTypes);
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| 88 | Delegate builderBuilder = Delegate.CreateDelegate(
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| 89 | typeof (Func<>).MakeGenericType(builderType), null, createBuilderMethod);
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| 90 |
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| 91 | MethodInfo buildMethod = typeof (MessageStreamIterator<TMessage>)
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| 92 | .GetMethod("BuildImpl", BindingFlags.Static | BindingFlags.NonPublic)
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| 93 | .MakeGenericMethod(typeof (TMessage), builderType);
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| 94 |
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| 95 | return (Func<CodedInputStream, ExtensionRegistry, TMessage>) Delegate.CreateDelegate(
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| 96 | typeof (Func<CodedInputStream, ExtensionRegistry, TMessage>), builderBuilder, buildMethod);
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| 97 | }
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| 98 | catch (ArgumentException e)
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| 99 | {
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| 100 | typeInitializationException = e;
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| 101 | }
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| 102 | catch (InvalidOperationException e)
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| 103 | {
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| 104 | typeInitializationException = e;
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| 105 | }
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| 106 | catch (InvalidCastException e)
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| 107 | {
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| 108 | // Can't see why this would happen, but best to know about it.
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| 109 | typeInitializationException = e;
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| 110 | }
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| 111 | return null;
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| 112 | }
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| 113 |
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| 114 | /// <summary>
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| 115 | /// Works out the builder type for TMessage, or throws an ArgumentException to explain why it can't.
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| 116 | /// </summary>
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| 117 | private static Type FindBuilderType()
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| 118 | {
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| 119 | MethodInfo createBuilderMethod = typeof (TMessage).GetMethod("CreateBuilder", EmptyTypes);
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| 120 | if (createBuilderMethod == null)
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| 121 | {
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| 122 | throw new ArgumentException("Message type " + typeof (TMessage).FullName +
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| 123 | " has no CreateBuilder method.");
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| 124 | }
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| 125 | if (createBuilderMethod.ReturnType == typeof (void))
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| 126 | {
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| 127 | throw new ArgumentException("CreateBuilder method in " + typeof (TMessage).FullName +
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| 128 | " has void return type");
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| 129 | }
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| 130 | Type builderType = createBuilderMethod.ReturnType;
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| 131 | Type messageInterface = typeof (IMessage<,>).MakeGenericType(typeof (TMessage), builderType);
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| 132 | Type builderInterface = typeof (IBuilder<,>).MakeGenericType(typeof (TMessage), builderType);
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| 133 | if (Array.IndexOf(typeof (TMessage).GetInterfaces(), messageInterface) == -1)
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| 134 | {
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| 135 | throw new ArgumentException("Message type " + typeof (TMessage) + " doesn't implement " +
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| 136 | messageInterface.FullName);
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| 137 | }
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| 138 | if (Array.IndexOf(builderType.GetInterfaces(), builderInterface) == -1)
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| 139 | {
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| 140 | throw new ArgumentException("Builder type " + typeof (TMessage) + " doesn't implement " +
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| 141 | builderInterface.FullName);
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| 142 | }
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| 143 | return builderType;
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| 144 | }
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| 145 |
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| 146 | // This is only ever fetched by reflection, so the compiler may
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| 147 | // complain that it's unused
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| 148 | #pragma warning disable 0169
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| 149 | /// <summary>
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| 150 | /// Method we'll use to build messageReader, with the first parameter fixed to TMessage.CreateBuilder. Note that we
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| 151 | /// have to introduce another type parameter (TMessage2) as we can't constrain TMessage for just a single method
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| 152 | /// (and we can't do it at the type level because we don't know TBuilder). However, by constraining TMessage2
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| 153 | /// to not only implement IMessage appropriately but also to derive from TMessage2, we can avoid doing a cast
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| 154 | /// for every message; the implicit reference conversion will be fine. In practice, TMessage2 and TMessage will
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| 155 | /// be the same type when we construct the generic method by reflection.
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| 156 | /// </summary>
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| 157 | private static TMessage BuildImpl<TMessage2, TBuilder>(Func<TBuilder> builderBuilder, CodedInputStream input,
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| 158 | ExtensionRegistry registry)
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| 159 | where TBuilder : IBuilder<TMessage2, TBuilder>
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| 160 | where TMessage2 : TMessage, IMessage<TMessage2, TBuilder>
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| 161 | {
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| 162 | TBuilder builder = builderBuilder();
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| 163 | input.ReadMessage(builder, registry);
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| 164 | return builder.Build();
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| 165 | }
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| 166 | #pragma warning restore 0414
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| 167 |
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| 168 | private static readonly uint ExpectedTag = WireFormat.MakeTag(1, WireFormat.WireType.LengthDelimited);
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| 169 |
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| 170 | private MessageStreamIterator(StreamProvider streamProvider, ExtensionRegistry extensionRegistry, int sizeLimit)
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| 171 | {
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| 172 | if (messageReader == null)
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| 173 | {
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| 174 | throw typeInitializationException;
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| 175 | }
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| 176 | this.streamProvider = streamProvider;
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| 177 | this.extensionRegistry = extensionRegistry;
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| 178 | this.sizeLimit = sizeLimit;
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| 179 | }
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| 180 |
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| 181 | private MessageStreamIterator(StreamProvider streamProvider, ExtensionRegistry extensionRegistry)
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| 182 | : this(streamProvider, extensionRegistry, CodedInputStream.DefaultSizeLimit)
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| 183 | {
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| 184 | }
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| 185 |
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| 186 | /// <summary>
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| 187 | /// Creates a new instance which uses the same stream provider as this one,
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| 188 | /// but the specified extension registry.
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| 189 | /// </summary>
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| 190 | public MessageStreamIterator<TMessage> WithExtensionRegistry(ExtensionRegistry newRegistry)
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| 191 | {
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| 192 | return new MessageStreamIterator<TMessage>(streamProvider, newRegistry, sizeLimit);
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| 193 | }
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| 194 |
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| 195 | /// <summary>
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| 196 | /// Creates a new instance which uses the same stream provider and extension registry as this one,
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| 197 | /// but with the specified size limit. Note that this must be big enough for the largest message
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| 198 | /// and the tag and size preceding it.
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| 199 | /// </summary>
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| 200 | public MessageStreamIterator<TMessage> WithSizeLimit(int newSizeLimit)
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| 201 | {
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| 202 | return new MessageStreamIterator<TMessage>(streamProvider, extensionRegistry, newSizeLimit);
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| 203 | }
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| 204 |
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| 205 | public static MessageStreamIterator<TMessage> FromFile(string file)
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| 206 | {
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| 207 | return new MessageStreamIterator<TMessage>(() => File.OpenRead(file), ExtensionRegistry.Empty);
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| 208 | }
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| 209 |
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| 210 | public static MessageStreamIterator<TMessage> FromStreamProvider(StreamProvider streamProvider)
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| 211 | {
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| 212 | return new MessageStreamIterator<TMessage>(streamProvider, ExtensionRegistry.Empty);
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| 213 | }
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| 214 |
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| 215 | public IEnumerator<TMessage> GetEnumerator()
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| 216 | {
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| 217 | using (Stream stream = streamProvider())
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| 218 | {
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| 219 | CodedInputStream input = CodedInputStream.CreateInstance(stream);
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| 220 | input.SetSizeLimit(sizeLimit);
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| 221 | uint tag;
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| 222 | string name;
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| 223 | while (input.ReadTag(out tag, out name))
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| 224 | {
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| 225 | if ((tag == 0 && name == "item") || (tag == ExpectedTag))
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| 226 | {
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| 227 | yield return messageReader(input, extensionRegistry);
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| 228 | }
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| 229 | else
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| 230 | {
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| 231 | throw InvalidProtocolBufferException.InvalidMessageStreamTag();
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| 232 | }
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| 233 |
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| 234 | input.ResetSizeCounter();
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| 235 | }
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| 236 | }
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| 237 | }
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| 238 |
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| 239 | IEnumerator IEnumerable.GetEnumerator()
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| 240 | {
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| 241 | return GetEnumerator();
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| 242 | }
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| 243 | }
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| 244 | } |
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