How can libxml2 be used to parse data from XML? - c

Question

I have looked around at the libxml2 code samples and I am confused on how to piece them all together.
What are the steps needed when using libxml2 to just parse or extract data from an XML file?
I would like to get hold of, and possibly store information for, certain attributes. How is this done?

Answer 1

I believe you first need to create a Parse tree. Maybe this article can help, look through the section which says How to Parse a Tree with Libxml2.

Answer 2

libxml2 provides various examples showing basic usage.
http://xmlsoft.org/examples/index.html
For your stated goals, tree1.c would probably be most relevant.
tree1.c: Navigates a tree to print
element names
Parse a file to a tree, use
xmlDocGetRootElement() to get the root
element, then walk the document and
print all the element name in document
order.
http://xmlsoft.org/examples/tree1.c
Once you have an xmlNode struct for an element, the "properties" member is a linked list of attributes. Each xmlAttr object has a "name" and "children" object (which are the name/value for that attribute, respectively), and a "next" member which points to the next attribute (or null for the last one).
http://xmlsoft.org/html/libxml-tree.html#xmlNode
http://xmlsoft.org/html/libxml-tree.html#xmlAttr

Answer 3

I found these two resources helpful when I was learning to use libxml2 to build a rss feed parser.
Tutorial with SAX interface
Tutorial using the DOM Tree (code example for getting an attribute value included)

Answer 4

Here, I mentioned complete process to extract XML/HTML data from file on windows platform.
First download pre-compiled .dll form http://xmlsoft.org/sources/win32/
Also download its dependency iconv.dll and zlib1.dll from the same page
Extract all .zip files into the same directory. For Ex: D:\demo\
Copy iconv.dll, zlib1.dll and libxml2.dll into c:\windows\system32 deirectory
Make libxml_test.cpp file and copy following code into that file.
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <libxml/HTMLparser.h>
void traverse_dom_trees(xmlNode * a_node)
{
xmlNode *cur_node = NULL;
if(NULL == a_node)
{
//printf("Invalid argument a_node %p\n", a_node);
return;
}
for (cur_node = a_node; cur_node; cur_node = cur_node->next)
{
if (cur_node->type == XML_ELEMENT_NODE)
{
/* Check for if current node should be exclude or not */
printf("Node type: Text, name: %s\n", cur_node->name);
}
else if(cur_node->type == XML_TEXT_NODE)
{
/* Process here text node, It is available in cpStr :TODO: */
printf("node type: Text, node content: %s, content length %d\n", (char *)cur_node->content, strlen((char *)cur_node->content));
}
traverse_dom_trees(cur_node->children);
}
}
int main(int argc, char **argv)
{
htmlDocPtr doc;
xmlNode *roo_element = NULL;
if (argc != 2)
{
printf("\nInvalid argument\n");
return(1);
}
/* Macro to check API for match with the DLL we are using */
LIBXML_TEST_VERSION
doc = htmlReadFile(argv[1], NULL, HTML_PARSE_NOBLANKS | HTML_PARSE_NOERROR | HTML_PARSE_NOWARNING | HTML_PARSE_NONET);
if (doc == NULL)
{
fprintf(stderr, "Document not parsed successfully.\n");
return 0;
}
roo_element = xmlDocGetRootElement(doc);
if (roo_element == NULL)
{
fprintf(stderr, "empty document\n");
xmlFreeDoc(doc);
return 0;
}
printf("Root Node is %s\n", roo_element->name);
traverse_dom_trees(roo_element);
xmlFreeDoc(doc); // free document
xmlCleanupParser(); // Free globals
return 0;
}
Open Visual Studio Command Promt
Go To D:\demo directory
execute cl libxml_test.cpp /I".\libxml2-2.7.8.win32\include" /I".\iconv-1.9.2.win32\include" /link libxml2-2.7.8.win32\lib\libxml2.lib command
Run binary using libxml_test.exe test.html command(Here test.html may be any valid HTML file)

Answer 5

You can refere this answer.
here they store data into structure format and use further by passing structure address to a function.
You can find detail code in c for use.
code ->> this