Re: URGENT! always open files in rb mode because of new lines

[Michal H. <ms...@gm...>]

On Mon, Aug 10, 2009 at 10:46:47AM +0200, Michal Hocko wrote:
> On Sun, Aug 09, 2009 at 10:15:17PM +0000, Jozef Misutka wrote:
[...]
> I would consider this as Windows specific ill-behavior. Handling
> end-line in text mode differently than in binary mode sounds little bit
> crazy to me.
> 
[...]
> 
> And one last thing. If fread translates end-lines on the background and
> it returns correct numbers of read elements then we should be safe,
> shouldn't we?
> The code is prepared for \r\n vs \n and we are getting data from already
> read buffer.
> 
> Stream::getLine
> 	-> for()
> 		getChar()
> 		if (EOF || \n)
> 			break
> 		if (\r) && lookChar == \n
> 			getChar();
> 
> FileStream::getChar()
> 	return (bufPtr >= bufEnd && !fillBuf()) ? EOF : (*bufPtr++ & 0xff);
> 
> FileStream::lookChar is basically same excpet it doesnt update bufPtr.
> 
> FileStream::fillBuffer()
> {
>   [...]
>   n = fread(buf, 1, n, f);
>   bufEnd = buf + n;
>   [...]
> }
> 
> How this can be off-by-one?

Ahh, I've got it. This is about fread return value:
"
fread returns the number of full items actually read...
"

This is expected but:
"
If the given stream is opened in text mode, carriage return?linefeed
pairs are replaced with single linefeed characters. The replacement has
no effect on the file pointer or the return value.
"

That means that you don't have any idea what has been filled into the
buffer unless you prefill it with 0 before you call fread. Crazy!
fread is really useless in Windows for text files.

> I am little bit confused about that. Could you check it?
> 
> Btw. I have already prepared patch but I would like to be sure I
> understand where is the problem before I commit it.

I will add this into the log message and commit it right away.

> 
> > 
> > http://pdfedit.petricek.net/bt/view.php?id=324
> > 
> > 
> > /jozo
> 
> -- 
> Michal Hocko
> 
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-- 
Michal Hocko