Daniel Veillard | c948420 | 2001-10-24 12:35:52 +0000 | [diff] [blame^] | 1 | <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/REC-html40/loose.dtd"> |
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| 12 | <title>The SAX interface</title> |
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| 20 | <h1>The XML C library for Gnome</h1> |
| 21 | <h2>The SAX interface</h2> |
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| 57 | <p>Sometimes the DOM tree output is just too large to fit reasonably into |
| 58 | memory. In that case (and if you don't expect to save back the XML document |
| 59 | loaded using libxml), it's better to use the SAX interface of libxml. SAX is |
| 60 | a <strong>callback-based interface</strong> to the parser. Before parsing, |
| 61 | the application layer registers a customized set of callbacks which are |
| 62 | called by the library as it progresses through the XML input.</p> |
| 63 | <p>To get more detailed step-by-step guidance on using the SAX interface of |
| 64 | libxml, see the <a href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">nice |
| 65 | documentation</a>.written by <a href="mailto:james@daa.com.au">James |
| 66 | Henstridge</a>.</p> |
| 67 | <p>You can debug the SAX behaviour by using the <strong>testSAX</strong> |
| 68 | program located in the gnome-xml module (it's usually not shipped in the |
| 69 | binary packages of libxml, but you can find it in the tar source |
| 70 | distribution). Here is the sequence of callbacks that would be reported by |
| 71 | testSAX when parsing the example XML document shown earlier:</p> |
| 72 | <pre>SAX.setDocumentLocator() |
| 73 | SAX.startDocument() |
| 74 | SAX.getEntity(amp) |
| 75 | SAX.startElement(EXAMPLE, prop1='gnome is great', prop2='&amp; linux too') |
| 76 | SAX.characters( , 3) |
| 77 | SAX.startElement(head) |
| 78 | SAX.characters( , 4) |
| 79 | SAX.startElement(title) |
| 80 | SAX.characters(Welcome to Gnome, 16) |
| 81 | SAX.endElement(title) |
| 82 | SAX.characters( , 3) |
| 83 | SAX.endElement(head) |
| 84 | SAX.characters( , 3) |
| 85 | SAX.startElement(chapter) |
| 86 | SAX.characters( , 4) |
| 87 | SAX.startElement(title) |
| 88 | SAX.characters(The Linux adventure, 19) |
| 89 | SAX.endElement(title) |
| 90 | SAX.characters( , 4) |
| 91 | SAX.startElement(p) |
| 92 | SAX.characters(bla bla bla ..., 15) |
| 93 | SAX.endElement(p) |
| 94 | SAX.characters( , 4) |
| 95 | SAX.startElement(image, href='linus.gif') |
| 96 | SAX.endElement(image) |
| 97 | SAX.characters( , 4) |
| 98 | SAX.startElement(p) |
| 99 | SAX.characters(..., 3) |
| 100 | SAX.endElement(p) |
| 101 | SAX.characters( , 3) |
| 102 | SAX.endElement(chapter) |
| 103 | SAX.characters( , 1) |
| 104 | SAX.endElement(EXAMPLE) |
| 105 | SAX.endDocument()</pre> |
| 106 | <p>Most of the other interfaces of libxml are based on the DOM tree-building |
| 107 | facility, so nearly everything up to the end of this document presupposes the |
| 108 | use of the standard DOM tree build. Note that the DOM tree itself is built by |
| 109 | a set of registered default callbacks, without internal specific |
| 110 | interface.</p> |
| 111 | <p><a href="mailto:daniel@veillard.com">Daniel Veillard</a></p> |
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