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

#region Copyright notice and license
// Protocol Buffers - Google's data interchange format
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// https://developers.google.com/protocol-buffers/
//
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//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
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// in the documentation and/or other materials provided with the
// distribution.
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// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
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#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;
        }
    }
}