Re: Expat Wrapper and SAX Filters

Stig, Can you give me some ideas about what the interface may look like some usage example or anything that can be useful? I'm working on a PHP book and we'll comment the XML_Parser class and I think it would be very nice to comment how you'll be able to code SAX filters and chains of filters with the listener interface even if this is not done yet. If you have n o clue no problem. Thanks, Luis "Stig S. Bakken" <ssb@fast.no> escribió en el mensaje news:1018436169.18496.2.camel@kirin.trondheim.fast.no... > Unless someone beats me to it, I'll implement a listener interface in > the next XML_Parser release. > > - Stig > > On Tue, 2002-04-09 at 19:14, Luis Argerich wrote: > > After taking a look at your Parser class wrapping the Expat parser I wanted > > to share and idea with you. > > > > IMHO the SAX wrapper class should allow the user to set a "listener" object, > > an object where SAX events are passed, > > the SAX wrapper should implement all the SAX handlers and only do a > > $this->listener->nameOfHandler(params) inside. > > This way we can program SAX filters that receive SAX events and produce more > > SAX events or some result, chaining > > filters allow to build complex SAX transformations/modifications or other > > operations over XML documents. > > > > For example take a look at this abstract classes: > > > > class AbstractSAXParser { > > var $listener; > > function AbstractSAXParser() {} > > function parserSetoption($opt,$val) {} > > function setListener($obj) { > > $this->listener=$obj; > > } > > function startElementHandler($parser,$name,$attribs) { > > $this->listener->startElementHandler($name,$attribs); > > } > > function endElementHandler($parser,$name) { > > $this->listener->endElementHandler($name); > > } > > function characterDataHandler($parser,$data) { > > $this->listener->characterDataHandler($data); > > } > > function parse() {} > > } > > > > class AbstractFilter { > > var $listener; > > > > function setListener($obj) { > > $this->listener=$obj; > > } > > function startElementHandler($name,$attribs) {} > > function endElementHandler($name) {} > > function characterDataHandler($data) {} > > > > } > > > > The abstract SAX parser wraps a SAX parser, we can make a derivative class > > for Expat or we can also derivate the AbstractClass to a class > > that parses non-xml data generating SAX events and thus allowing to convert > > non-xml data to XML. > > > > The Filter is the class that receives SAX events and in the handlers perform > > some operations and may propagate the events to a next listener, > > a final Filter that outputs XML for example just intercepts the events but > > don't propagate them. > > > > Example: > > > > $parser=new ExpatParser($xmlfilename); // ExpatParser extends > > AbstractSAXPaser > > $filter=new Filter(); // Some filter > > $parser->setListener($filter); > > $parser->parse(); > > We can for example chain filters to transform a document using several minor > > "modular" transformations or modify a document using a filter > > that adds or remove elements (several elements can be added or removed if we > > queue the modifications in the filter before parsing) > > This leads to several advantages since complex transformations/modifications > > can be performed reading the XML file just once and at > > SAX speed and cosuming very few resources. Results can also be streammed > > since SAX allows streaming the result as it is generated. > > > > I believe that PEAR is the place where the "standard" AbstractSAXParser and > > Filter classes can be defined standarizing the way to > > write SAX filters with PHP. > > > > Let me know what you think about this. > > > > > > > > > > > > -- > > PEAR Development Mailing List (http://pear.php.net/) > > To unsubscribe, visit: http://www.php.net/unsub.php >