NRHashCode.cs

using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;
using System;

namespace hash
{
    public class Program
    {
        const int Iterations = 10;

        static void Main(string[] args)
        {
            BenchmarkRunner.Run<Program>();
        }

        [Params(
            "",
            "1",
            "12",
            "123",
            "1234",
            "12345",
            "123456",
            "1234567",
            "12345678",
            "123456789",
            "1234567890",
            "12345678901234567890",
            "1234567890123456789012345678901234567890",
            "12345678901234567890123456789012345678901234567890123456789012345678901234567890",
            "1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890"
        )]
        public string Input { get; set; }

        [Benchmark(OperationsPerInvoke = Iterations, Baseline = true)]
        public int CurrentHashCode()
        {
            var input = Input;
            var hashCode = 0;
            for (var i = 0; i < Iterations; i++)
            {
                hashCode += CurrentHashCode(input);
            }
            return hashCode;
        }


        [Benchmark(OperationsPerInvoke = Iterations)]
        public int NewHashCode()
        {
            var input = Input;
            var hashCode = 0;
            for (var i = 0; i < Iterations; i++)
            {
                hashCode += HashCode(input);
            }
            return hashCode;
        }

        public int CurrentHashCode(string str)
        {
            unsafe
            {
                fixed (char* src = str)
                {
                    int hash1 = 5381;

                    int hash2 = hash1;

                    int c;
                    char* s = src;
                    while ((c = s[0]) != 0)
                    {
                        hash1 = ((hash1 << 5) + hash1) ^ c;
                        c = s[1];
                        if (c == 0)
                            break;
                        hash2 = ((hash2 << 5) + hash2) ^ c;
                        s += 2;
                    }

                    return hash1 + (hash2 * 1566083941);
                }
            }
        }

        public int HashCode(string str)
        {
            unsafe
            {
                fixed (char* src = str)
                {
                    int hash1 = 5381;

                    int hash2 = hash1;

                    char* current = src;
                    char* end = current + str.Length;
                    while (current < end - 1)
                    {
                        hash1 = ((hash1 << 5) + hash1) ^ current[0];
                        hash2 = ((hash2 << 5) + hash2) ^ current[1];
                        current += 2;
                    }

                    if (current < end)
                    {
                        hash1 = ((hash1 << 5) + hash1) ^ current[0];
                    }

                    return hash1 + (hash2 * 1566083941);
                }
            }
        }
    }
}