path: root/src/ProtocolBuffers/Descriptors/DescriptorUtil.cs

// 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:
//
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// in the documentation and/or other materials provided with the
// distribution.
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using System.Collections.Generic;
using Google.ProtocolBuffers.Collections;

namespace Google.ProtocolBuffers.Descriptors {
  /// <summary>
  /// Internal class containing utility methods when working with descriptors.
  /// </summary>
  internal static class DescriptorUtil {
    /// <summary>
    /// Equivalent to Func[TInput, int, TOutput] but usable in .NET 2.0. Only used to convert
    /// arrays.
    /// </summary>
    internal delegate TOutput IndexedConverter<TInput, TOutput>(TInput element, int index);

    /// <summary>
    /// Converts the given array into a read-only list, applying the specified conversion to
    /// each input element.
    /// </summary>
    internal static IList<TOutput> ConvertAndMakeReadOnly<TInput, TOutput>(IList<TInput> input,
        IndexedConverter<TInput, TOutput> converter) {
      TOutput[] array = new TOutput[input.Count];
      for (int i = 0; i < array.Length; i++) {
        array[i] = converter(input[i], i);
      }
      return Lists<TOutput>.AsReadOnly(array);
    }
  }
}