// Copyright (c) .NET Foundation and contributors. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.

#if !NETSTANDARD2_0
using System;
#endif

// This is needed due to NativeAOT which doesn't enable nullable globally yet
#nullable enable

namespace ILLink.Shared
{
    internal static class HashUtils
    {
#if NETSTANDARD2_0
        // This constant is taken from code that Roslyn generates for GetHashCode of records.
        private const int Multiplier = -1521134295;
#endif
        public static int Combine<T1, T2>(T1 value1, T2 value2)
            where T1 : notnull
            where T2 : notnull
        {
#if NETSTANDARD2_0
            return value1.GetHashCode() * Multiplier + value2.GetHashCode();
#else
            return HashCode.Combine(value1, value2);
#endif
        }

        public static int Combine<T1, T2, T3>(T1 value1, T2 value2, T3 value3)
            where T1 : notnull
            where T2 : notnull
            where T3 : notnull
        {
#if NETSTANDARD2_0
            return (value1.GetHashCode() * Multiplier + value2.GetHashCode()) * Multiplier + value3.GetHashCode();
#else
            return HashCode.Combine(value1, value2, value3);
#endif
        }
    }
}