Requesting complete, compilable libxml2 sax example

Question

I'm having a heck of a time figuring out how to use the sax parser for libxml2. Can someone post an example that parses this XML ( yes, without the <xml...> header and footer tags, if that can be parsed by the libxml2 sax parser):

<hello foo="bar">world</hello>

The parser should print out the data enclosed in element hello and also grab the value of attribute foo.

I'm working on this example, but hoping that someone else beats me to the punch since I'm not making much progress. The Google hasn't yielded any complete, working examples for libxml2 sax parser.

Answer 1

Adapted from http://julp.developpez.com/c/libxml2/?page=sax

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <libxml/tree.h>
#include <libxml/parser.h>
#include <libxml/parserInternals.h>


void start_element_callback(void *user_data, const xmlChar *name, const xmlChar **attrs) {
  printf("Beginning of element : %s \n", name);
  while (NULL != attrs && NULL != attrs[0]) {
    printf("attribute: %s=%s\n",attrs[0],attrs[1]);
    attrs = &attrs[2];
  }
}

int main() {
  const char* xml_path = "hello_world.xml";
  FILE *xml_fh = fopen(xml_path,"w+");
  fputs("<hello foo=\"bar\" baz=\"baa\">world</hello>",xml_fh);
  fclose(xml_fh);


  // Initialize all fields to zero
  xmlSAXHandler sh = { 0 };

  // register callback
  sh.startElement = start_element_callback;

  xmlParserCtxtPtr ctxt;

  // create the context
  if ((ctxt = xmlCreateFileParserCtxt(xml_path)) == NULL) {
    fprintf(stderr, "Erreur lors de la création du contexte\n");
    return EXIT_FAILURE;
  }
  // register sax handler with the context
  ctxt->sax = &sh;

  // parse the doc
  xmlParseDocument(ctxt);
  // well-formed document?
  if (ctxt->wellFormed) {
    printf("XML Document is well formed\n");
  } else {
    fprintf(stderr, "XML Document isn't well formed\n");
    //xmlFreeParserCtxt(ctxt);
    return EXIT_FAILURE;
  }

  // free the memory
  // xmlFreeParserCtxt(ctxt);


  return EXIT_SUCCESS;
}

This produces output:

Beginning of element : hello 
attribute: foo=bar
attribute: baz=baa
XML Document is well formed

Compiled with the following command on Ubuntu 10.04.1:

g++ -I/usr/include/libxml2 libxml2_hello_world.cpp /usr/lib/libxml2.a -lz\
    -o libxml2_hello_world