Chris@0: # The Parser Model
Chris@0: 
Chris@0: The parser model here follows the model in section
Chris@0: [8.2.1](http://www.w3.org/TR/2012/CR-html5-20121217/syntax.html#parsing)
Chris@0: of the HTML5 specification, though we do not assume a networking layer.
Chris@0: 
Chris@0:      [ InputStream ]    // Generic support for reading input.
Chris@0:            ||
Chris@0:       [ Scanner ]       // Breaks down the stream into characters.
Chris@0:            ||
Chris@0:      [ Tokenizer ]      // Groups characters into syntactic
Chris@0:            ||
Chris@0:     [ Tree Builder ]    // Organizes units into a tree of objects
Chris@0:            ||
Chris@0:      [ DOM Document ]     // The final state of the parsed document.
Chris@0: 
Chris@0: 
Chris@0: ## InputStream
Chris@0: 
Chris@0: This is an interface with at least two concrete implementations:
Chris@0: 
Chris@0: - StringInputStream: Reads an HTML5 string.
Chris@0: - FileInputStream: Reads an HTML5 file.
Chris@0: 
Chris@0: ## Scanner
Chris@0: 
Chris@0: This is a mechanical piece of the parser.
Chris@0: 
Chris@0: ## Tokenizer
Chris@0: 
Chris@0: This follows section 8.4 of the HTML5 spec. It is (roughly) a recursive
Chris@0: descent parser. (Though there are plenty of optimizations that are less
Chris@0: than purely functional.
Chris@0: 
Chris@0: ## EventHandler and DOMTree
Chris@0: 
Chris@0: EventHandler is the interface for tree builders. Since not all
Chris@0: implementations will necessarily build trees, we've chosen a more
Chris@0: generic name.
Chris@0: 
Chris@0: The event handler emits tokens during tokenization.
Chris@0: 
Chris@0: The DOMTree is an event handler that builds a DOM tree. The output of
Chris@0: the DOMTree builder is a DOMDocument.
Chris@0: 
Chris@0: ## DOMDocument
Chris@0: 
Chris@0: PHP has a DOMDocument class built-in (technically, it's part of libxml.)
Chris@0: We use that, thus rendering the output of this process compatible with
Chris@0: SimpleXML, QueryPath, and many other XML/HTML processing tools.
Chris@0: 
Chris@0: For cases where the HTML5 is a fragment of a HTML5 document a
Chris@0: DOMDocumentFragment is returned instead. This is another built-in class.