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food.xml

This example demonstrate the parsing of an XML using static addressing method. In this method the target address to store XML content is specified at compile time.

XML

Sample of XML data to be parsed.

<food>
    <name>Belgian Waffles</name>
    <price>5.95</price>
    <description>Two of our famous Belgian Waffles with plenty of real maple syrup</description>
    <calories>650</calories>
</food>

Schema

This is the schema of above XML data.

<?xml version="1.0"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
 <xs:element name="food">
    <xs:complexType>
      <xs:sequence>
        <xs:element type="xs:string" name="name"/>
        <xs:element type="xs:float" name="price"/>
        <xs:element type="xs:string" name="description"/>
        <xs:element type="xs:unsignedInt" name="calories"/>
      </xs:sequence>
    </xs:complexType>
  </xs:element>
</xs:schema>

The schema of above XML file is defined here food.xsd. the root element of this XML is "food". It contains four child elements,

  • name : Name of food item
  • price : Price of food item
  • description : Description of food item
  • calories : Calories of food item

food_t

food_t is a structure that represent the content of above XML schema. It is defined in food.h.

typedef struct
{
    char* name;           //!< Holds content of "name" XML element
    float price;          //!< Holds content of "price" XML element
    char* description;    //!< Holds content of "description" XML element
    uint32_t calories;    //!< Holds content of "calories" XML element
}food_t;

food.c contain a global variable food_t waffle;, where we shall extract the content of XML data.

xs_element_t

food.c file contains xs_element_t structure for all the elements of XML schema including root element "food". The xs_element_t structure contains all the validation rules of an XML element specified in the schema.

  • xs_element_t food_root; : holds properties of root element "food".
  • xs_attribute_t food_attribute : holds properties of attributes of root element "food".
  • xs_element_t food_descendant[4] : holds properties of all the child elements of root element "food". Each element of an array represent child elements like name, price, description and calories sequentially. Each element also hold the address of target address statically. e.g.
  food_descendant[0].Target.Address  = &waffle.name,
  food_descendant[1].Target.Address  = &waffle.price,
  food_descendant[2].Target.Address  = &waffle.description,
  food_descendant[3].Target.Address  = &waffle.calories,

parse_xml

To parse the given XML data, call parse_xml function.

xml_parse_result_t result = parse_xml(&food_root, xml_str, NULL);

Where,

  • food_root is an instance of xs_element_t of root element.
  • xml_str is a NULL terminated (char*) string containing XML data to parse.

How to build and run

This example doesn't use any platform or OS specific libraries. You only need standard C99 compiler to build this example. No need to change any configuration/#define in the parse_xml.c file.

This is a console application. When you execute/run this example it prints extracted XML data on the console.

Output