Date: Thu, 8 May 1997 17:06:20 +0300 (IDT)
From: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
To: Diego Zuccato <dz AT bo DOT dada DOT it>
cc: djgpp-workers AT delorie DOT com
Subject: Re: write() modified to handle __FSEXT funcs on text files
In-Reply-To: <33721B44.2FDB@bo.dada.it>
Message-ID: <Pine.SUN.3.91.970508165206.21083B-100000@is>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Precedence: bulk


On Thu, 8 May 1997, Diego Zuccato wrote:

> > Thanks, but I think the call to the __FSEXT function should be *before*
> > the conversion,
> I too. But it's quite anti-intuitive. After all, text files are DOS
> specific, right ?

Yes, but they look like Unix files *before* the conversion; after the 
conversion, they have those CR characters added that are DOS-specific.

> I wrote a 'portable' locker for a database and a friend told me that in
> Linux O_BINARY and O_TEXT aren't defined.

Just say this, and it will be portable to Unix/Linux also:

	#include <fcntl.h>
	#ifndef O_BINARY
	# define O_BINARY 0
	#endif
	#ifndef O_TEXT
	# define O_TEXT 0
	#endif

Now, when you say open ("blabla", O_RDONLY | O_BINARY), all systems will 
be happy.

If you want to be friendly to Win32 compilers, check for _O_BINARY and 
define O_BINARY to be _O_BINARY if O_BINARY isn't defined.

> >         1) The hook might not need the conversion at all, in which
> > case you are just waisting cycles.
> Right. But if I don't want conversion, I open it in binary format...

I disagree.  The beauty of Filesystem Extensions is exactly that it is so
completely transparent to the code that calls `write'.  You hook the
`write' call, but whoever called `write' doesn't even know that the call
winds up in your handler!  So this mechanism is ideal when you need to
radically change the behavior of a program without touching anything in
the main code of that program.  Therefore, we should not assume that the
same person both decides how to open the file and installs his/her FSEXT
hook. 

> original code...). Or we could call a user-defined function to handle
> text conversion (__FSEXT_txt_conv ?)...

I think that conversion NL -> CR-LF is so easy that any FSEXT hook that 
really needs it could do it by itself.  So I say: don't bother with 
conversion, let the hook do it.