internal FileStreamImpl()

in csharp/NativeUtils/FileStream.cs [289:333]
33 lines of code
8 McCabe index (conditional complexity)

		internal FileStreamImpl(string path, FileMode mode, FileAccess access, FileShare share, int bufferSize, FileOptions options)
		{
			_deleteOnClose = options.HasFlag(FileOptions.DeleteOnClose);
			_fileName = path; //_deleteOnClose ? path : null;
			_fd = -1;

			if (options.HasFlag((FileOptions.Asynchronous | FileOptions.Encrypted)))
				throw new NotImplementedException($"options: {options}");

			int flags = 0;
			if ((int)mode < 1 || (int)mode > 6)
				throw new ArgumentException($"mode: {mode}?");

			if ((int)access < 1 || (int)access > 3)
				throw new ArgumentException($"access: {access}?");

			if (mode == FileMode.Append && access != FileAccess.Write)
				throw new ArgumentException($"mode: Append, access: {access}?");

			// Arrays treated as 1-based
			flags = ModeFlags[(int)mode - 1] | AccessFlags[(int)access - 1];

			// We never modify our file on open, truncation is done separately, in order to not damage the file if it turns out to be locked
			int fd = Check("open", open(path, flags & ~O_TRUNC, Convert.ToInt32("777", 8)));

			try
			{
				LockFd(fd, share, path);
				// If the lock is taken and the file is opened, try to truncate, if necessary
				if (0 != (flags & O_TRUNC))
				{
					Check("lseek", lseek(fd, 0, 0));
					Check("ftruncate", ftruncate(fd, 0));
				}

				_fd = fd;
			}
			catch
			{
				// On error, close file/lock and rethrow
				close(fd);
				GC.SuppressFinalize(this);
				throw;
			}
		}