バイト配列の部分コピーの速度のおはなし

    class Program
    {
        const int COUNT = 1000000;
        static void Main(string[] args)
        {
            var basearray = Enumerable.Range(0, 1024).Select(x => (byte) x).ToArray();

            var sw = Stopwatch.StartNew();
            for (var i = 0; i < COUNT; i++)
            {
                var buffer = basearray.Skip(20).Take(20).ToArray();
            }
            sw.Stop();

            Console.WriteLine($"linq {sw.ElapsedMilliseconds}ms");

            sw = Stopwatch.StartNew();
            for (var i = 0; i < COUNT; i++)
            {
                var buffer = new byte[20];
                Array.Copy(basearray, 20, buffer, 0, 20);
            }
            sw.Stop();

            Console.WriteLine($"ArrayCopy {sw.ElapsedMilliseconds}ms");

            sw = Stopwatch.StartNew();
            for (var i = 0; i < COUNT; i++)
            {
                var buffer = new byte[20];
                Buffer.BlockCopy(basearray, 20, buffer, 0, 20);
            }
            sw.Stop();

            Console.WriteLine($"BlockCopy {sw.ElapsedMilliseconds}ms");


            sw = Stopwatch.StartNew();
            var ptr = Marshal.AllocCoTaskMem(basearray.Length);
            Marshal.Copy(basearray, 0, ptr, basearray.Length);
            try
            {

                for (var i = 0; i < COUNT; i++)
                {
                    var buffer = new byte[20];
                    Marshal.Copy(ptr + 20, buffer, 0, 20);
                }
            }
            finally
            {
                Marshal.FreeCoTaskMem(ptr);
            }
            sw.Stop();

            Console.WriteLine($"marshal {sw.ElapsedMilliseconds}ms");

            Console.ReadKey();
        }