csharp/src/Google.Protobuf/Collections/Lists.cs

#region Copyright notice and license
// Protocol Buffers - Google's data interchange format
// Copyright 2017 Google Inc.  All rights reserved.
// https://developers.google.com/protocol-buffers/
//
// 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
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#endregion

using System.Collections.Generic;
using System.Collections.ObjectModel;

namespace Google.Protobuf.Collections
{
    /// <summary>
    /// Utility to compare if two Lists are the same, and the hash code
    /// of a List.
    /// </summary>
    public static class Lists
    {
        /// <summary>
        /// Checks if two lists are equal.
        /// </summary>
        public static bool Equals<T>(List<T> left, List<T> right)
        {
            if (left == right)
            {
                return true;
            }
            if (left == null || right == null)
            {
                return false;
            }
            if (left.Count != right.Count)
            {
                return false;
            }
            IEqualityComparer<T> comparer = EqualityComparer<T>.Default;
            for (int i = 0; i < left.Count; i++)
            {
                if (!comparer.Equals(left[i], right[i]))
                {
                    return false;
                }
            }
            return true;
        }

        /// <summary>
        /// Gets the list's hash code.
        /// </summary>
        public static int GetHashCode<T>(List<T> list)
        {
            if (list == null)
            {
                return 0;
            }
            int hash = 31;
            foreach (T element in list)
            {
                hash = hash * 29 + element.GetHashCode();
            }
            return hash;
        }
    }
}