Re: [xml] Per parser xmlGcMemSetup

On Sat, May 05, 2007 at 10:40:22PM +0200, Joachim Zobel wrote:
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

But mod_i18n should know it is operating on top of libxml2 parser,
so why doesn't it use the libxml2 allocation routines ? The SAX interfaces
at the C level are really parser specific, and libxml2 SAX2 have been heavilly
modified to improve performances, so I don't see why it would use a different
allocator then.

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.

That sounds quite complex, though there is certainly good reasons for this :-)


Red Hat Virtualization group
Daniel Veillard      | virtualization library
veillard redhat com  | libxml GNOME XML XSLT toolkit | Rpmfind RPM search engine

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