Re: [Mingw-users] Strategies for dealing with Unix-style files on Windows

[Earnie <ea...@us...>]

Paul Leder wrote:
> I'd like to handle Unix-style as well as DOS-style line endings on the 
> MinGW version of my code. Does anyone have any thoughts on this?
> 
> The problem is that I'd prefer to open input files in text mode. When 
> your open a NL-only file in text mode, however, fpos/fseek don't work on 
> the file. If you get a file position, and then seek to it, you end up 
> somewhere else in the file. This works for CR/NL files, of course, but 
> not NL-only files.
> 

I think you're backwards here, or I'm understanding you backwards.  The
text mode I/O will remove the CR making fpos/fseek worthless.  You want
to open the files in binary mode and handle the dangling CR at the end
of the strings.

> I've also tried fgetpos/fsetpos, but they have exactly the same problem.
> 
> I've also tried _setmode, to set the file mode to binary before the fpos 
> and back to text after the fseek. This works for NL-only files, but 
> fails for CR/NL files. MSDN also says that you should call _setmode 
> before doing any file I/O, so I wouldn't want to do this anyway.
> 

Yea, you need to leave them in binary mode.

> AFAICT, if I want to deal with "text" files that are NL-only, and I want 
> to fpos/fseek on those files, then I must open them in binary mode. 
> Unfortunately, when I do this, I get other errors in my code, which I 
> haven't looked at yet. I guess I may just have to fix these instead.
> 

Yes, you should fix the other errors.  It is a long known issue.  The
other errors may be related to dangling CR which will remain in the
strings when read.

> I suppose one point of view is that you shouldn't open NL-only files in 
> "text" mode on Windows, because they're not what Windows considers to be 
> "text". Now that I've written it down, I suppose that's the only logical 
> answer.
> 

The only problem I know for NL only files is notepad because it reads
the data in binary mode expecting to find a CR to put the data on the
next line and some versions of MSVC editor.  I've never heard of
fpos/fseek having an issue with NL only files, rather the reverse.  But
things may have changed for newer versions of the OS and/or MSVCRT?

-- 
Earnie
-- http://www.for-my-kids.com