1#region Copyright notice and license
2// Protocol Buffers - Google's data interchange format
3// Copyright 2008 Google Inc.  All rights reserved.
4// https://developers.google.com/protocol-buffers/
5//
6// Redistribution and use in source and binary forms, with or without
7// modification, are permitted provided that the following conditions are
8// met:
9//
10//     * Redistributions of source code must retain the above copyright
11// notice, this list of conditions and the following disclaimer.
12//     * Redistributions in binary form must reproduce the above
13// copyright notice, this list of conditions and the following disclaimer
14// in the documentation and/or other materials provided with the
15// distribution.
16//     * Neither the name of Google Inc. nor the names of its
17// contributors may be used to endorse or promote products derived from
18// this software without specific prior written permission.
19//
20// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
21// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
22// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
23// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
24// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
25// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
26// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
27// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
28// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
29// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
30// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
31#endregion
32
33using System.Collections.Generic;
34using System.Collections.ObjectModel;
35
36namespace Google.Protobuf.Reflection
37{
38    /// <summary>
39    /// Internal class containing utility methods when working with descriptors.
40    /// </summary>
41    internal static class DescriptorUtil
42    {
43        /// <summary>
44        /// Equivalent to Func[TInput, int, TOutput] but usable in .NET 2.0. Only used to convert
45        /// arrays.
46        /// </summary>
47        internal delegate TOutput IndexedConverter<TInput, TOutput>(TInput element, int index);
48
49        /// <summary>
50        /// Converts the given array into a read-only list, applying the specified conversion to
51        /// each input element.
52        /// </summary>
53        internal static IList<TOutput> ConvertAndMakeReadOnly<TInput, TOutput>
54            (IList<TInput> input, IndexedConverter<TInput, TOutput> converter)
55        {
56            TOutput[] array = new TOutput[input.Count];
57            for (int i = 0; i < array.Length; i++)
58            {
59                array[i] = converter(input[i], i);
60            }
61            return new ReadOnlyCollection<TOutput>(array);
62        }
63    }
64}