using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.IO;

using System.Reflection;

using System.Collections.ObjectModel;

using System.Threading.Tasks;

using System.Net.Http;

using System.Threading;

using System.Security.Cryptography;

​

using System.Text.Json;

​

using NUnit.Framework; // Throws NUnit.Framework.AssertionException

​

//https://stackoverflow.com/questions/73284540/how-to-calculate-hash-while-saving-file-to-disk-using-streams

​

    public static partial class JsonExtensions

    {

        public static void ReadAndAssert(this ref Utf8JsonReader reader)

        {

            if (!reader.Read())

                throw new JsonException();

        }

    }

​

    public class Program

    {

        public async Task Test()

        {

            var inputFileName = "Question73284540In.txt";

            var outputFileName = "Question73284540Out.txt";

            File.WriteAllText(inputFileName, "this is some text");

            await using (var stream = new FileStream(inputFileName, FileMode.Open, FileAccess.Read, FileShare.Read, bufferSize: 4096, useAsync: true))

            {

                await SaveAsync(stream, outputFileName, default(CancellationToken));

            }

        }

​

        async Task SaveAsync(Stream stream, string path, CancellationToken ct)

        {

            var sha512 = SHA512.Create();

#if false           

            var fileName = Path.GetFileName(path);

            var destinationPath = Path.Combine("/tmp", fileName);

#else

            var destinationPath = path;

#endif  

            await using (var fileStream = File.Create(path))

            await using (var cryptoStream = new CryptoStream(fileStream, sha512, CryptoStreamMode.Write))

            {

                await stream.CopyToAsync(cryptoStream, ct);

​

            }

            if (sha512?.Hash is { } computedHash)

                Console.WriteLine(Convert.ToBase64String(computedHash));

            else

                Console.WriteLine("err");

        }       

        public static async Task Main(string[] args)

        {

            Console.WriteLine("Environment version: {0} ({1})", System.Runtime.InteropServices.RuntimeInformation.FrameworkDescription , GetNetCoreVersion());

            Console.WriteLine("{0} version: {1}", typeof(JsonSerializer).Assembly.GetName().Name,  typeof(JsonSerializer).Assembly.FullName);

            Console.WriteLine();

​

            try

            {

                await new Program().Test();

            }

            catch (Exception ex)

            {

                Console.WriteLine("Failed with unhandled exception: ");

                Console.WriteLine(ex);

                throw;

            }

        }

        public static string GetNetCoreVersion()

        {

            //https://techblog.dorogin.com/how-to-detect-net-core-version-in-runtime-ecd65ad695be

            //

            var assembly = typeof(System.Runtime.GCSettings).GetTypeInfo().Assembly;

            var assemblyPath = assembly.Location.Split(new[] { '/', '\\' }, StringSplitOptions.RemoveEmptyEntries);

            int netCoreAppIndex = Array.IndexOf(assemblyPath, "Microsoft.NETCore.App");

            if (netCoreAppIndex > 0 && netCoreAppIndex < assemblyPath.Length - 2)

                return assemblyPath[netCoreAppIndex + 1];

            return null;

        }

    }

​