[Python-Dev] C standard io library, flush/read/write problem

[Emerson Clarke]

The other night i was watching a google techtalk about python 3000 and
Guido mentioned some problems with the C standard io library.

In particular he highlighted an issue with switching between reading
and writing without flushing and the fact that it caused serious
errors.  Not that i dont think its a good idea to write a new io
library, but I wondered if it was the same problem ive encounted.

It only happens on windows that i know off, but the fix is simple...

Assuming you have a hanlde to the file called "Handle" and a Flush()
method, the following logic for read and write will allow you to
detect and prevent the problem.

Add this to the Read() method before reading takes place:

if ( Handle && (Handle->_flag & _IORW) && (Handle->_flag & (_IOREAD |
_IOWRT)) == _IOWRT )
{
	Flush();
	Handle->_flag |= _IOREAD;
}

Add this to the Write() method before writing takes place:

if ( Handle && (Handle->_flag & _IORW) && (Handle->_flag & (_IOREAD |
_IOWRT)) == _IOREAD )
{
	Flush();
	Handle->_flag |= _IOWRT;
}



Emerson