Re: [xml] IO callbacks are not thread-safe

[Rob Richards <rrichards cdatazone org>]

Daniel Veillard wrote:
> On Thu, Apr 02, 2009 at 05:33:54PM +0200, Petr Pajas wrote:
>   
> > I think the original reason for this was that when Perl bindings are 
> > used with mod_perl, there may be other (non-Perl) components using 
> > the global callbacks differently; that's why XML::LibXML Perl 
> > module tries to clean after itself (restoring whatever was in the 
> > callbacks previously). Is there any other way around this?
> >     
>
>   Urgh ..
> Why do they need global URI handler registration ?
> The cleanest wey would be to always use the I/O parser context creation
> routine like xmlCtxtReadIO/xmlReadIO... and define the I/O handlers
> to map to whatever is being registered globally now. Though the
> limitation is for external subset resources, that doesn't work well.
> Maybe we need to make those per-thread but this is getting ugly !
>
>
>   
I ran into a similar issue a while back, though dealing just with usage 
from within a process in a web servers rather than threads specifically. 
This was one of the reasons why I implemented the 
xmlParserInputBufferCreateFilenameDefault and 
xmlOutputBufferCreateFilenameDefault functions for use in PHP. That way 
we are able to completely isolate our I/O handling from anything else 
that might be running within the same process. An app could leverage 
those functions, though would require it to manage it its own handler 
lookup/setup routines.

Rob