src/ProtocolBuffers/ExtendableMessageLite.cs

#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/
//
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// 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
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#endregion

using System;
using System.Collections.Generic;
namespace Google.ProtocolBuffers {
  public abstract class ExtendableMessageLite<TMessage, TBuilder> : GeneratedMessageLite<TMessage, TBuilder>
    where TMessage : GeneratedMessageLite<TMessage, TBuilder>
    where TBuilder : GeneratedBuilderLite<TMessage, TBuilder> {

    protected ExtendableMessageLite() { }
    private readonly FieldSet extensions = FieldSet.CreateInstance();

    /// <summary>
    /// Access for the builder.
    /// </summary>
    internal FieldSet Extensions {
      get { return extensions; }
    }

    /// <summary>
    /// Checks if a singular extension is present.
    /// </summary>
    public bool HasExtension<TExtension>(GeneratedExtensionLite<TMessage, TExtension> extension) {
      VerifyExtensionContainingType(extension);
      return extensions.HasField(extension.Descriptor);
    }

    /// <summary>
    /// Returns the number of elements in a repeated extension.
    /// </summary>
    public int GetExtensionCount<TExtension>(GeneratedExtensionLite<TMessage, IList<TExtension>> extension) {
      VerifyExtensionContainingType(extension);
      return extensions.GetRepeatedFieldCount(extension.Descriptor);
    }

    /// <summary>
    /// Returns the value of an extension.
    /// </summary>
    public TExtension GetExtension<TExtension>(GeneratedExtensionLite<TMessage, TExtension> extension) {
      VerifyExtensionContainingType(extension);
      object value = extensions[extension.Descriptor];
      if (value == null) {
        return extension.DefaultValue;
      } else {
        return (TExtension)extension.FromReflectionType(value);
      }
    }

    /// <summary>
    /// Returns one element of a repeated extension.
    /// </summary>
    public TExtension GetExtension<TExtension>(GeneratedExtensionLite<TMessage, IList<TExtension>> extension, int index) {
      VerifyExtensionContainingType(extension);
      return (TExtension)extension.SingularFromReflectionType(extensions[extension.Descriptor, index]);
    }

    /// <summary>
    /// Called to check if all extensions are initialized.
    /// </summary>
    protected bool ExtensionsAreInitialized {
      get { return extensions.IsInitialized; }
    }

    public override bool IsInitialized {
      get {
        return ExtensionsAreInitialized;
      }
    }

    /// <summary>
    /// Used by subclasses to serialize extensions. Extension ranges may be
    /// interleaves with field numbers, but we must write them in canonical
    /// (sorted by field number) order. This class helps us to write individual
    /// ranges of extensions at once.
    /// 
    /// TODO(jonskeet): See if we can improve this in terms of readability.
    /// </summary>
    protected class ExtensionWriter {
      readonly IEnumerator<KeyValuePair<IFieldDescriptorLite, object>> iterator;
      readonly FieldSet extensions;
      KeyValuePair<IFieldDescriptorLite, object>? next = null;

      internal ExtensionWriter(ExtendableMessageLite<TMessage, TBuilder> message) {
        extensions = message.extensions;
        iterator = message.extensions.GetEnumerator();
        if (iterator.MoveNext()) {
          next = iterator.Current;
        }
      }

      public void WriteUntil(int end, CodedOutputStream output) {
        while (next != null && next.Value.Key.FieldNumber < end) {
          extensions.WriteField(next.Value.Key, next.Value.Value, output);
          if (iterator.MoveNext()) {
            next = iterator.Current;
          } else {
            next = null;
          }
        }
      }
    }

    protected ExtensionWriter CreateExtensionWriter(ExtendableMessageLite<TMessage, TBuilder> message) {
      return new ExtensionWriter(message);
    }

    /// <summary>
    /// Called by subclasses to compute the size of extensions.
    /// </summary>
    protected int ExtensionsSerializedSize {
      get { return extensions.SerializedSize; }
    }

    internal void VerifyExtensionContainingType<TExtension>(GeneratedExtensionLite<TMessage, TExtension> extension) {
      if (!ReferenceEquals(extension.ContainingTypeDefaultInstance, DefaultInstanceForType)) {
        // This can only happen if someone uses unchecked operations.
        throw new ArgumentException(
          String.Format("Extension is for type \"{0}\" which does not match message type \"{1}\".",
          extension.ContainingTypeDefaultInstance, DefaultInstanceForType
          ));
      }
    }
  }
}