using BenchmarkDotNet.Attributes;

using BenchmarkDotNet.Running;

using System;

using System.Diagnostics;

using System.Threading;

using System.Security.Cryptography;

using Microsoft.EntityFrameworkCore.ValueGeneration;

​

public class Program

{

    public class LongGenerator 

    {

        public static long LastDateTimeTicks = DateTime.UtcNow.Ticks;

        // Ensure that the same DateTime.UtcNow.Ticks value cannot be 

        // returned twice. This is important for concurrent operations.

        public static long Next()

        {

            long result = 0L;

            long ticksNow = DateTime.UtcNow.Ticks;

            do 

            {

                result = Interlocked.Increment(ref LastDateTimeTicks);

                if (result >= ticksNow)

                {

                    return result;

                }

            }

            while(Interlocked.CompareExchange(ref LastDateTimeTicks, ticksNow, result) != result);

            return result;

        }

    }

    public class SequentialGuidGenerator

    {

        private static byte[] ProcessId = new byte[8];

        static SequentialGuidGenerator()

        {

            using (var cryptoServiceProvider = new RNGCryptoServiceProvider())

            {

                cryptoServiceProvider.GetBytes(ProcessId);

            }

        }

        public static Guid Next()

        {

            var result = new byte[16];

            var sequentialTimestamp = BitConverter.GetBytes(LongGenerator.Next());

            if (!BitConverter.IsLittleEndian)

            {

                Array.Reverse(sequentialTimestamp); 

            }

            result[0] = ProcessId[0];

            result[1] = ProcessId[1];

            result[2] = ProcessId[2];

            result[3] = ProcessId[3];

            result[4] = ProcessId[4];

            result[5] = ProcessId[5];

            result[6] = ProcessId[6];

            result[7] = ProcessId[7];

            result[8] = sequentialTimestamp[1];

            result[9] = sequentialTimestamp[0];

            result[10] = sequentialTimestamp[7];

            result[11] = sequentialTimestamp[6];

            result[12] = sequentialTimestamp[5];

            result[13] = sequentialTimestamp[4];

            result[14] = sequentialTimestamp[3];

            result[15] = sequentialTimestamp[2];

            return new Guid(result);

        }

        public static Guid NewGuid()

        {

            var result = new byte[16];

            var sequentialTimestamp = BitConverter.GetBytes(LongGenerator.Next());

            if (!BitConverter.IsLittleEndian)

            {

                Array.Reverse(sequentialTimestamp); 

            }

            using (var cryptoServiceProvider = new RNGCryptoServiceProvider())

            {

                cryptoServiceProvider.GetBytes(ProcessId);

            }

            result[0] = ProcessId[0];

            result[1] = ProcessId[1];

            result[2] = ProcessId[2];

            result[3] = ProcessId[3];

            result[4] = ProcessId[4];

            result[5] = ProcessId[5];

            result[6] = ProcessId[6];

            result[7] = ProcessId[7];

            result[8] = sequentialTimestamp[1];

            result[9] = sequentialTimestamp[0];

            result[10] = sequentialTimestamp[7];

            result[11] = sequentialTimestamp[6];

            result[12] = sequentialTimestamp[5];

            result[13] = sequentialTimestamp[4];

            result[14] = sequentialTimestamp[3];

            result[15] = sequentialTimestamp[2];

            return new Guid(result);

        }

    }

    public class Profiler

    {

        private Stopwatch _stopwatch = new Stopwatch();

        public Profiler()

        {

            _stopwatch = new Stopwatch();

        }

        public void Profile(Action method)

        {

            _stopwatch = Stopwatch.StartNew();

            method();

            _stopwatch.Stop();

            var result = _stopwatch.Elapsed;

            Console.WriteLine(result.TotalMilliseconds.ToString("\n0.000\n"));

            _stopwatch = null;

        }

    }

    public class TestBenchmark

    {

        [BenchmarkDotNet.Attributes.Benchmark]

        public void SequentialGuidTest1()

        {

            var numberOfIterations = 10;

            while(numberOfIterations != 0)

            {

                numberOfIterations--;

                Console.WriteLine(SequentialGuidGenerator.Next());

            }

        }

        [BenchmarkDotNet.Attributes.Benchmark]

        public void SequentialGuidTest2()

        {

            var numberOfIterations = 10;

            while(numberOfIterations != 0)

            {

                numberOfIterations--;

                Console.WriteLine(SequentialGuidGenerator.NewGuid());

            }

        }

        [BenchmarkDotNet.Attributes.Benchmark]

        public void SequentialGuidTest3()

        {

            var sequentialGuid = new SequentialGuidValueGenerator();

            var numberOfIterations = 10;

            while(numberOfIterations != 0)

            {

                numberOfIterations--;

                Console.WriteLine(sequentialGuid.Next(null));

            }

        }

    }

    public static void Main(string[] args)

    {   

        var summary = BenchmarkRunner.Run<TestBenchmark>();

    }

}