How do I inform Windows that I'm writing a binary file?

(devblogs.microsoft.com)

17 points | by ingve 2 days ago ago

16 comments

  • Isamu an hour ago

    Going all the way back to the earliest C compilers. There was a decision made to make “\n” just work on DOS for portability of Unix programs, and to make the examples from the C programming book just work.

    But in Unix “\n” is a single byte, and in DOS it is 2. So they introduced text and binary modes for files on DOS. Behind the scenes the library will handle the extra byte. This is not necessary in Unix.

    I used to have to be careful about importing files to DOS. Did the file come from Unix?

    • criddell an hour ago

      Linefeed (\n) is a single byte in DOS as well.

      I think you are talking about carriage return linefeed pair (CRLF or \r\n),

      These control codes go back to line printers. Linefeed advances the paper one line and carriage return moves the print head to the left.

      • Isamu 13 minutes ago

        >Linefeed (\n) is a single byte in DOS as well.

        In binary mode. In text mode if you printf(“Hello World\n”) you get CRLF because that’s how text works on DOS. Unix had the convention of only requiring the LF for text. And Unix didn’t have text/binary modes. That’s the compatibility hack on DOS.

  • saltyoldman 2 days ago

    fopen(..., "wb") ?

    • qbane an hour ago

      It's C library taking care of the "b" part for you according to the article.

      • wahern an hour ago

        It's the other way around. It's the C runtime that treats text ("t") mode differently, because the C standard specifies \n as a line delimiter but the Windows convention is \r\n. In text mode C stdio translates between \n and \r\n. In binary mode it does no translation.

  • lmm an hour ago

    The article seems to be taking the position that the C runtime library is not part of "Windows", which feels like a rather odd view to me. What is the stable API that Windows offers to application developers if not that?

    • ChrisSD an hour ago

      The Win32 API. E.g. using WriteFile to write files (https://learn.microsoft.com/en-us/windows/win32/api/fileapi/...)

      It wasn't until fairly recently that the C runtime was stably shipped with Windows. Previously you had to install the correct version of the C library alongside your application.

      • userbinator 7 minutes ago

        It wasn't until fairly recently

        By "recently" you mean Win95? MSVCRT.DLL has been there for at least that long.

      • lmm an hour ago

        > The Win32 API. E.g. using WriteFile to write files (https://learn.microsoft.com/en-us/windows/win32/api/fileapi/...)

        Which is called from what, if not C? Does windows really offer no API for writing text (rather than bytes) to files? Or does it rely on the application developer to manage line endings in their own code? Neither of those sounds very developer-friendly.

        • ChrisSD 40 minutes ago

          Calling it from C does not mean you need a full C standard library to exist. For example, much of the C standard library is itself written in C. But it's a "freestanding" C which assumes only a minimal set of library functions exist (e.g. functions for copying memory from one place to another, filling memory with zeroes, etc).

          And you can of course use non-C languages to call the Win32 API. Or even directly using assembly code.

          • lmm 16 minutes ago

            > you can of course use non-C languages to call the Win32 API. Or even directly using assembly code.

            Is that a supported/official API though? On Linux you "can" put your arguments in registers and trigger the system call interrupt directly, and I think Go programs even do this, but it's not the official interface and they reserve the right to break your program in future updates, at least in theory.

            • Pannoniae 8 minutes ago

              Calling win32 from other languages is supported, calling it from assembly is supported (as long as you use the calling convention properly, obviously), using ntdll to bypass the win32 API is not supported.

              Basically on Linux the syscalls are the equivalent of Win32 except much narrower in scope.

        • p_l an hour ago

          The whole issue is specific to C and languages that copied C or use its runtime underneath in implementations (like Python)

          For reference, Unix has no API other than bytes either.

          • lmm 11 minutes ago

            > The whole issue is specific to C and languages that copied C or use its runtime underneath in implementations (like Python)

            So it's "specific to" almost all programming languages in actual use. That's a rather esoteric point.

            > For reference, Unix has no API other than bytes either.

            Unix does offer an API for writing C-standard in-memory text strings to Unix-standard on-disk text files, it just happens to be the same one as the API for writing in-memory binary strings to on-disk binary files.

    • p_l an hour ago

      Indeed, C runtime is not part of windows API, and it's normal to have a program include few different copies of C runtime library due to different modules compiled with different compilers/options.

      C runtime library being part of OS is accidental thing in Unix, 16bit and 32bit Windows API even does not use C-compatible ABI (instead, Pascal-compatible one is present)