Every piece of information in an XML file (elements, text, numbers) is stored in memory in "nodes". Nodes are defined by the mxml_node_t structure. The type member defines the node type (element, integer, opaque, real, or text) which determines which value you want to look at in the value union.
| Value | Type | Node member |
|---|---|---|
| Custom | void * | node->value.custom.data |
| Element | char * | node->value.element.name |
| Integer | int | node->value.integer |
| Opaque (string) | char * | node->value.opaque |
| Real | double | node->value.real |
| Text | char * | node->value.text.string |
Each node also has a user_data member which allows you to associate application-specific data with each node as needed.
New nodes are created using the mxmlNewElement, mxmlNewInteger, mxmlNewOpaque, mxmlNewReal, mxmlNewText mxmlNewTextf mxmlNewXML functions. Only elements can have child nodes, and the top node must be an element, usually the <?xml version="1.0"?> node created by mxmlNewXML().
Nodes have pointers to the node above (parent), below ( child), left (prev), and right (next) of the current node. If you have an XML file like the following:
<?xml version="1.0"?>
<data>
<node>val1</node>
<node>val2</node>
<node>val3</node>
<group>
<node>val4</node>
<node>val5</node>
<node>val6</node>
</group>
<node>val7</node>
<node>val8</node>
</data>
the node tree for the file would look like the following in memory:
?xml
|
data
|
node - node - node - group - node - node
| | | | | |
val1 val2 val3 | val7 val8
|
node - node - node
| | |
val4 val5 val6
where "-" is a pointer to the next node and "|" is a pointer to the first child node.
Once you are done with the XML data, use the mxmlDelete function to recursively free the memory that is used for a particular node or the entire tree:
mxmlDelete(tree);