protobuf/src/ProtocolBuffers/RpcUtil.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/
//
// 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
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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#endregion

using System;

namespace Google.ProtocolBuffers {
  /// <summary>
  /// Grab-bag of utility functions useful when dealing with RPCs.
  /// </summary>
  public static class RpcUtil {

    /// <summary>
    /// Converts an Action[IMessage] to an Action[T].
    /// </summary>
    public static Action<T> SpecializeCallback<T>(Action<IMessage> action) 
        where T : IMessage<T> {
      return message => action(message);
    }

    /// <summary>
    /// Converts an Action[T] to an Action[IMessage].
    /// The generalized action will accept any message object which has
    /// the same descriptor, and will convert it to the correct class
    /// before calling the original action. However, if the generalized
    /// callback is given a message with a different descriptor, an
    /// exception will be thrown.
    /// </summary>
    public static Action<IMessage> GeneralizeCallback<TMessage, TBuilder>(Action<TMessage> action, TMessage defaultInstance)
        where TMessage : class, IMessage<TMessage, TBuilder> 
        where TBuilder : IBuilder<TMessage, TBuilder> {
      return message => {
        TMessage castMessage = message as TMessage;
        if (castMessage == null) {  
          castMessage = defaultInstance.CreateBuilderForType().MergeFrom(message).Build();
        }
        action(castMessage);
      };
    }
  }
}