1 #region Copyright notice and license
2 // Protocol Buffers - Google's data interchange format
3 // Copyright 2017 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 
33 using System.Collections.Generic;
34 using System.Collections.ObjectModel;
35 
36 namespace Google.Protobuf.Collections
37 {
38     /// <summary>
39     /// Utility to compare if two Lists are the same, and the hash code
40     /// of a List.
41     /// </summary>
42     public static class Lists
43     {
44         /// <summary>
45         /// Checks if two lists are equal.
46         /// </summary>
Equals(List<T> left, List<T> right)47         public static bool Equals<T>(List<T> left, List<T> right)
48         {
49             if (left == right)
50             {
51                 return true;
52             }
53             if (left == null || right == null)
54             {
55                 return false;
56             }
57             if (left.Count != right.Count)
58             {
59                 return false;
60             }
61             IEqualityComparer<T> comparer = EqualityComparer<T>.Default;
62             for (int i = 0; i < left.Count; i++)
63             {
64                 if (!comparer.Equals(left[i], right[i]))
65                 {
66                     return false;
67                 }
68             }
69             return true;
70         }
71 
72         /// <summary>
73         /// Gets the list's hash code.
74         /// </summary>
GetHashCode(List<T> list)75         public static int GetHashCode<T>(List<T> list)
76         {
77             if (list == null)
78             {
79                 return 0;
80             }
81             int hash = 31;
82             foreach (T element in list)
83             {
84                 hash = hash * 29 + element.GetHashCode();
85             }
86             return hash;
87         }
88     }
89 }