chickadee » ssax » ssax:make-parser

(ssax:make-parser TAG1 VAL1 [TAG2 VAL2 ...]) syntax

Create a custom XML parser instance of the XML parsing framework. This will be a SAX, a DOM or a specialized parser depending on the supplied user-handlers.

The arguments to ssax::make-parser are symbol-value pairs, interleaved in the argument list. In other words, TAG1, TAG2 etc are unquoted(!) symbols that identify the type of value that follows the tagsee below for the list of allowed tags.

The output of this macro is a procedure that represents a parser which accepts two arguments, PORT and SEED. PORT is the port from which to read the XML data and SEED is the initial value of an accumulator that will be passed into the first procedure, where it can be appended to and returned. Then this value will be passed on to the next procedure and so on to eventually obtain a result, in a FOLD-like fashion.

Given below are tags and signatures of the corresponding values. Not all tags have to be specified. If some are omitted, reasonable defaults will apply. SEED always represents the current value of the accumulator that will eventually be returned by the parser.

DOCTYPE

     procedure PORT DOCNAME SYSTEMID INTERNAL-SUBSET? SEED

If INTERNAL-SUBSET? is #t, the current position in the port is right after we have read #\[ that begins the internal DTD subset. We must finish reading of this subset before we return (or must call ssax:skip-internal-dtd if we aren't interested in reading it).

The port at exit must be at the first symbol after the whole DOCTYPE declaration. The handler-procedure must generate four values:

     ELEMS ENTITIES NAMESPACES SEED

See xml-decl::elems for ELEMS. It may be #f to switch off the validation. NAMESPACES will typically contain user prefixes for selected URI symbols. The default handler-procedure skips the internal subset, if any, and returns (values #f '() '() SEED).

UNDECL-ROOT

     procedure ELEM-GI SEED

where ELEM-GI is an UNRES-NAME of the root element. This procedure is called when an XML document under parsing contains no DOCTYPE declaration. The handler-procedure, as a DOCTYPE handler procedure above, must generate four values:

      ELEMS ENTITIES NAMESPACES SEED

The default handler-procedure returns (values #f '() '() seed)

NEW-LEVEL-SEED

     procedure ELEM-GI ATTRIBUTES NAMESPACES EXPECTED-CONTENT SEED

where ELEM-GI is a RES-NAME of the element about to be processed. This procedure is to generate the seed to be passed to handlers that process the content of the element.

FINISH-ELEMENT

     procedure ELEM-GI ATTRIBUTES NAMESPACES PARENT-SEED SEED

This procedure is called when parsing of ELEM-GI is finished. The SEED is the result from the last content parser (or from new-level-seed if the element has the empty content). PARENT-SEED is the same seed as was passed to new-level-seed. The procedure is to generate a seed that will be the result of the element parser.

CHAR-DATA-HANDLER

     procedure STRING1 STRING2 SEED

The procedure is supposed to handle a chunk of character data STRING1 followed by a chunk of character data STRING2. STRING2 is a short string, often "\n" and even "" Returns a new SEED.

PI

     association-list ((PI-TAG . PI-HANDLER) ...)

where PI-TAG is the name of the processing instruction and PI-HANDLER is a procedure PORT PI-TAG SEED.

The handler should read the rest of the PI from PORT, up to and including the combination "?>" that terminates the PI. The handler should return a new seed.

One of the PI-TAGs may be the symbol *DEFAULT*. The corresponding handler will handle PIs that no other handler will. If the *DEFAULT* PI-TAG is not specified, ssax:make-pi-parser will assume the default handler that skips the body of the PI.