Re: [xml] Per parser xmlGcMemSetup

[Joachim Zobel <jz-2006 heute-morgen de>]

Am Samstag, den 05.05.2007, 15:28 -0400 schrieb Daniel Veillard:

>   if you're calling the callbacks from libxml2 just to build a tree it's
> bad, either use one of the parsers or build the tree with the tree API.
> Other uses are not suported, in the sense that I may break randomly 
> how the callback works. 

>   I don't know why you are doing this but this sounds extremely fishy,
> would you care to explain, because I'm trying to guess and mostly I see
> only bad reasons.

THis is IMHO necessarily so. Apache has so called filters that can
modify the outgoing contents. mod_xml2 is such a filter. It runs the
libxml2 parser to turn a stream of text buffers (called buckets by
apache) into a stream of sax events (called sax buckets by me). Other
filters can then modify these sax events. The sax buckets automatically
turn back into text when they are treated as such, so no filter is
necessary on the network end.

One of such filter is mod_i18n. It checks the stream of sax events it
passes until it detects a certain attribute and then starts building a
small partial tree, which is modified and then turned back into sax
events. 

The point with this is that it stays streaming as much as possible and
it is also possible to do tree manipulation. It is in many cases a
usable workaround for the sax/dom dilemma and I am already thinking
about using the same trick for another module.

It does however require to call the SAX2 callbacks.

Sincerely,
Joachim