dotnet-installer/scripts/dotnet-cli-build/Utils/Utils.cs

using System;
using System.IO;
using System.Runtime.InteropServices;
using System.Security.Cryptography;

namespace Microsoft.DotNet.Cli.Build
{
    public static class Utils
    {
        public static void CleanNuGetTempCache()
        {
            // Clean NuGet Temp Cache on Linux (seeing some issues on Linux)
            if (RuntimeInformation.IsOSPlatform(OSPlatform.Linux) && Directory.Exists("/tmp/NuGet"))
            {
                Directory.Delete("/tmp/NuGet", recursive: true);
            }
        }

        public static string GetOSName()
        {
            if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
            {
                return "win";
            }
            else if (RuntimeInformation.IsOSPlatform(OSPlatform.OSX))
            {
                return "osx";
            }
            else if (RuntimeInformation.IsOSPlatform(OSPlatform.Linux))
            {
                throw new NotImplementedException();
            }
            else
            {
                throw new PlatformNotSupportedException();
            }
        }

        // Generate a Version 5 (SHA1 Name Based) Guid from a name.
        public static Guid GenerateGuidFromName(string name)
        {
            // Any fixed GUID will do for a namespace.
            Guid namespaceId = new Guid("28F1468D-672B-489A-8E0C-7C5B3030630C");

            using (SHA1 hasher = SHA1.Create())
            {
                var nameBytes = System.Text.Encoding.UTF8.GetBytes(name ?? string.Empty);
                var namespaceBytes = namespaceId.ToByteArray();

                SwapGuidByteOrder(namespaceBytes);

                var streamToHash = new byte[namespaceBytes.Length + nameBytes.Length];

                Array.Copy(namespaceBytes, streamToHash, namespaceBytes.Length);
                Array.Copy(nameBytes, 0, streamToHash, namespaceBytes.Length, nameBytes.Length);

                var hashResult = hasher.ComputeHash(streamToHash);

                var res = new byte[16];

                Array.Copy(hashResult, res, res.Length);

                unchecked { res[6] = (byte)(0x50 | (res[6] & 0x0F)); }
                unchecked { res[8] = (byte)(0x40 | (res[8] & 0x3F)); }

                SwapGuidByteOrder(res);

                return new Guid(res);
            }
        }

        // Do a byte order swap, .NET GUIDs store multi byte components in little
        // endian.
        private static void SwapGuidByteOrder(byte[] b)
        {
            Swap(b, 0, 3);
            Swap(b, 1, 2);
            Swap(b, 5, 6);
            Swap(b, 7, 8);
        }

        private static void Swap(byte[] b, int x, int y)
        {
            byte t = b[x];
            b[x] = b[y];
            b[y] = t;
        }

        public static void DeleteDirectory(string path)
        {
            if (Directory.Exists(path))
            {
                string[] files = Directory.GetFiles(path, "*", SearchOption.AllDirectories);
                foreach (string file in files)
                {
                    File.SetAttributes(file, FileAttributes.Normal);
                    File.Delete(file);
                }

                Directory.Delete(path, true);
            }
        }

        public static void CopyDirectoryRecursively(string path, string destination)
        {
            foreach (var file in Directory.GetFiles(path, "*", SearchOption.AllDirectories))
            {
                string destFile = file.Replace(path, destination);
                Directory.CreateDirectory(Path.GetDirectoryName(destFile));
                File.Copy(file, destFile, true);
            }
        }
    }
}