Why doesn't Createfile() have a binary flag

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c++
winapi

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+4 Q:

Why doesn't Createfile() have a binary flag

One of the great joys of windows programming is remembering to put 'wb' or 'rb' or ios::binary in all the file open calls so that Windows doesn't merrily convert all your 0x13s.

I just had to convert a bunch of nicely standard code to use Createfile() to get a certain flag - and it occurred to me that there is no way to specify binary.
How does it know? I really don't want it changing bytes in my MP4 stream thank-you-very-much.

+1 A:

You can't specify a binary or text flag, because to the Windows OS, all files are binary! The wb and rb options are introduced as a nicety, as part of the C IO stream functionality, and even then only on DOS / Windows, to help the developer read and write text files and perform CR/LF to LF conversion.

Michael Goldshteyn 2010-10-29 18:21:16

+5 A:

Because CreateFile doesn't do "text-mode"/newline conversions. Those are handled at a higher level, either in FILE for the CRT or iostreams for C++.

Roger Pate 2010-10-29 18:21:52

Never really thought of Createfile as a lower level FILE, just as a windows only equivalent. I suppose to MS everything is Windows so you write cr/lf and read cr/lf, no need to ever convert.

Martin Beckett 2010-10-29 18:47:26

@Martin Beckett: actually, the `CreateFile()` function is just poorly named. It is used to open many, many other types of resources (folders, drives, serial/parallel ports, etc.), for most of which text/binary doesn't make sense because you're not transferring text.

André Caron 2010-10-29 19:31:23

CreateFile is the user-mode interface to the ZwCreateFile kernel function, so it's as low-level as you can get in user-mode.

Gerald 2010-10-29 21:19:32

Actually I misspoke there... NtCreateFile is the user-mode interface to ZwCreateFile, and CreateFile calls NtCreateFile. So you could go a little lower than CreateFile by calling NtCreateFile directly, but it's somewhat uglier.

Gerald 2010-10-29 21:26:46

+3 A:

Everything is binary as far as the Windows API is concerned. Personally I prefer it that way. I never use the "text mode" in the standard library stuff.

Gerald 2010-10-29 18:26:16

+1: I totally agree. Especially that many higher-level tools filter CR/LF only when they know you're reading text. For instance, the `<iostream>` standard library filters then out when using `operator>>` with `std::string` but not when using the `get(char*,streamsize)`.

André Caron 2010-10-29 19:32:53

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Why doesn't Createfile() have a binary flag

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