Understanding DOM with DOMC (a C implementation of DOM - minus a few features)
Use the Source Luke!!
Note: DOMC is freely available under the MIT License
- Download the DOMC source code (200 KB)
- Download the libmba helper code (200 KB)
- cd domc/src
- ctags *
- vim domc.h
- Navigate through the struct Document, Node, NodeList etc to understand the utter simplicity of the DOM C implementation
domc.h and node.c are THE most important files.
Core implementation
a)
DOM_Node is THE struct to understand and it's very very simple
It's recursively defined - a tree is a node containing other nodes/nodelists.
1) Fixed part - common to all nodes from document to attribute
struct DOM_Node {
DOM_String *nodeName;
DOM_String *nodeValue;
unsigned short nodeType; //Used as selector on union of variable parts below
//Pointers to other Nodes
DOM_Node *parentNode;
DOM_NodeList *childNodes;
DOM_Node *firstChild;
DOM_Node *lastChild;
DOM_Node *previousSibling;
DOM_Node *nextSibling;
DOM_NamedNodeMap *attributes;
DOM_Document *ownerDocument;
[...]2) Variable part -
DOMNode.nodeType above selects between document vs element vs attribute vs processing-instruction
union {
struct {
DOM_DocumentType *doctype;
DOM_Element *documentElement;
DOM_DocumentView *document;
DOM_AbstractView *defaultView;
DOM_Node *commonParent;
DOM_String *version;
DOM_String *encoding;
int standalone;
} Document;
struct {
DOM_String *tagName;
} Element;
struct {
DOM_String *name;
int specified;
DOM_String *value;
DOM_Element *ownerElement;
} Attr;
struct { // small code stripped out for clarity } DocumentType;
struct { // small code stripped out for clarity } CharacterData;
struct { // small code stripped out for clarity } Notation;
struct { // small code stripped out for clarity } Entity;
struct { // small code stripped out for clarity } ProcessingInstruction;
} u;b)
DOM_NodeList itself is a doubly-linked list with head/tail pointers
struct NodeEntry { struct Node *data; NodeEntry *before, *after; };
struct DOM_NodeList { NodeEntry *first, *last; DOM_NodeList *list; }Don't need the documentation at all but here it is anyway :
DOMC - A C Implementation of DOM docs
