[libxml2.wiki] Create SAX interface

[Nick Wellnhofer <nwellnhof src gnome org>]

commit 80c451d53c3bce5c4e29c10bf842233505fb4101
Author: Nick Wellnhofer <wellnhofer aevum de>
Date:   Sat Feb 12 18:08:55 2022 +0000

    Create SAX interface

 SAX-interface.md | 44 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)
---
diff --git a/SAX-interface.md b/SAX-interface.md
new file mode 100644
index 0000000..ce579bd
--- /dev/null
+++ b/SAX-interface.md
@@ -0,0 +1,44 @@
+Sometimes the DOM tree output is just too large to fit reasonably into memory. In that case (and if you 
don't expect to save back the XML document loaded using libxml), it's better to use the SAX interface of 
libxml. SAX is a **callback-based interface** to the parser. Before parsing, the application layer registers 
a customized set of callbacks which are called by the library as it progresses through the XML input.
+
+To get more detailed step-by-step guidance on using the SAX interface of libxml, see the [nice 
documentation](http://www.jamesh.id.au/articles/libxml-sax/libxml-sax.html) written by [James 
Henstridge](mailto:james daa com au).
+
+You can debug the SAX behaviour by using the **testSAX** program located in the gnome-xml module (it's 
usually not shipped in the binary packages of libxml, but you can find it in the tar source distribution). 
Here is the sequence of callbacks that would be reported by testSAX when parsing the example XML document 
shown earlier:
+
+```
+SAX.setDocumentLocator()
+SAX.startDocument()
+SAX.getEntity(amp)
+SAX.startElement(EXAMPLE, prop1='gnome is great', prop2='&amp; linux too')
+SAX.characters(   , 3)
+SAX.startElement(head)
+SAX.characters(    , 4)
+SAX.startElement(title)
+SAX.characters(Welcome to Gnome, 16)
+SAX.endElement(title)
+SAX.characters(   , 3)
+SAX.endElement(head)
+SAX.characters(   , 3)
+SAX.startElement(chapter)
+SAX.characters(    , 4)
+SAX.startElement(title)
+SAX.characters(The Linux adventure, 19)
+SAX.endElement(title)
+SAX.characters(    , 4)
+SAX.startElement(p)
+SAX.characters(bla bla bla ..., 15)
+SAX.endElement(p)
+SAX.characters(    , 4)
+SAX.startElement(image, href='linus.gif')
+SAX.endElement(image)
+SAX.characters(    , 4)
+SAX.startElement(p)
+SAX.characters(..., 3)
+SAX.endElement(p)
+SAX.characters(   , 3)
+SAX.endElement(chapter)
+SAX.characters( , 1)
+SAX.endElement(EXAMPLE)
+SAX.endDocument()
+```
+
+Most of the other interfaces of libxml2 are based on the DOM tree-building facility, so nearly everything up 
to the end of this document presupposes the use of the standard DOM tree build. Note that the DOM tree itself 
is built by a set of registered default callbacks, without internal specific interface.
\ No newline at end of file