## NAME

CheckExpatParserObj, CHandlerSetInstall, CHandlerSetRemove, CHandlerSetCreate, CHandlerSetGetUserData, GetExpatInfo -
Functions to create, install and remove expat parser object extensions.

## SYNOPSIS

    #include <tclexpat.h>

    int
    CheckExpatParserObj (interp, nameObj)

    int
    CHandlerSetInstall (interp, expatObj, handlerSet)

    int
    CHandlerSetRemove (interp, expatObj, handlerSetName)

    CHandlerSet*
    CHandlerSetCreate (handlerSetName)

    CHandlerSet*
    CHandlerSetGet (interp, expatObj, handlerSetName)

    void*
    CHandlerSetGetUserData (interp, expatObj, handlerSetName)

    TclGenExpatInfo*
    GetExpatInfo (interp, expatObj)

## ARGUMENTS

Type | Name | Mode
--- | --- | ---
Tcl_Interp | *interp | in
| Interpreter with the expat parser object.
Tcl_Obj | *expatObj | in
| A Tcl Object containing the command name of the expat parser object to be queried or modified.
char | *handlerSetName | in
| Identifier of the handler set.
CHandlerSet | *handlerSet | in
| Pointer to a C handler set.
Tcl_Obj | *nameObj |
| A Tcl Object containing the name of a expat parser object

## DESCRIPTION

The functions described in this manual allows one to add C level coded event handler to an tDOM Tcl expat parser objects. A tDOM Tcl expat parser object is able to have several Tcl scripts and C functions associated with a specific event. If the event occurs, first the Tcl scripts then the C functions associated with the event are called in turn.

A tDOM Tcl expat parser extension is an ordinary Tcl extension and loaded like every other Tcl extension. It must install at least one new Tcl Level command, that manipulates a tDOM Tcl expat parser object.

A C level handler set is a data structure like this:

    typedef struct CHandlerSet {
        struct CHandlerSet *nextHandlerSet;
        char *name;                     /* refname of the handler set */
        int ignoreWhiteCDATAs;          /* ignore 'white' CDATA sections */

        void *userData;                 /* Handler set specific Data Structure;
                                           the C handler set extension has to
                                           malloc the needed structure in his
                                           init func and has to provide a
                                           cleanup func (to free it). */

        CHandlerSet_userDataReset        resetProc;
        CHandlerSet_userDataFree         freeProc;

        /* C func for element start */
        XML_StartElementHandler          elementstartcommand;
        /* C func for element end */
        XML_EndElementHandler            elementendcommand;
        /* C func for character data */
        XML_CharacterDataHandler         datacommand;
        /* C func for namespace decl start */
        XML_StartNamespaceDeclHandler    startnsdeclcommand;
        /* C func for namespace decl end */
        XML_EndNamespaceDeclHandler      endnsdeclcommand;
        /* C func for processing instruction */
        XML_ProcessingInstructionHandler picommand;
        /* C func for default data */
        XML_DefaultHandler               defaultcommand;
        /* C func for unparsed entity declaration */
        XML_NotationDeclHandler          notationcommand;
        /* C func for external entity */
        XML_ExternalEntityRefHandler     externalentitycommand;
        /* C func for unknown encoding */
        XML_UnknownEncodingHandler       unknownencodingcommand;
        /* C func for comments */
        XML_CommentHandler               commentCommand;
        /* C func for "not standalone" docs */
        XML_NotStandaloneHandler         notStandaloneCommand;
        /* C func for CDATA section start */
        XML_StartCdataSectionHandler     startCdataSectionCommand;
        /* C func for CDATA section end */
        XML_EndCdataSectionHandler       endCdataSectionCommand;
        /* C func for !ELEMENT decl's */
        XML_ElementDeclHandler           elementDeclCommand;
        /* C func for !ATTLIST decl's */
        XML_AttlistDeclHandler           attlistDeclCommand;
        /* C func for !DOCTYPE decl's */
        XML_StartDoctypeDeclHandler      startDoctypeDeclCommand;
        /* C func for !DOCTYPE decl ends */
        XML_EndDoctypeDeclHandler        endDoctypeDeclCommand;
        /* C func for !ENTITY decls's */
        XML_EntityDeclHandler            entityDeclCommand;
    } CHandlerSet;

The types and the arguments of the event functions (XML_*) are exactly the same like the expat lib handler functions and described in detail in expat.h, see there. The extension has only to provided the handler functions needed; it's perfectly OK to leave unused handler slots as the are (they are initialized to NULL by CHandlerSetCreate).

The name of this structure is used to identify the handler set.

If the flag ignoreWhiteCDATAs is set, element content which contain only whitespace isn't reported with the datacommand.

The userData element points to the handler set specific data. The event handler functions are called with this pointer as userData argument.

resetProc and freeProc must have arguments that match the type

    void (Tcl_Interp *interp, void *userData)

resetProc is called in case the parser is reset with `<parserObj> reset` and should do any necessary cleanup and reinitializing to prepare the C handler set for a new XML document. The freeProc is called, if the parser is deleted and should do memory cleanup etc.

CHandlerSetCreate create a C handler set, gives it the name name and initializes any other element with NULL.

CHandlerSetInstall adds the handlerSet to the parser expatObj. The parser has to be a tDOM Tcl expat parser object in the interpreter interp. The name of the C handler set has to be unique for the parser. Returns 0 in case of success. Returns 1 if expatObj isn't a parser object in the interpreter interp. Returns 2 if this parser has already a C handler set with the handlerSet name.

CHandlerSetRemove removes the C handler set referenced by the handlerSetName from the parser expatObj. The parser has to be a tDOM Tcl expat parser object in the interpreter interp. CHandlerSetRemove calls the freeProc function of the C handler set structure, removes the handler set from the C handler set list and frees the handler structure. Returns 0 in case of success. Returns 1 if expatObj isn't a parser object in the interpreter interp. Returns 2 if this parser hasn't a C handler set named handlerSetName.

CheckExpatParserObj returns 1, if nameObj is a tDOM Tcl expat parser object in the interpreter interp, otherwise it returns 0. Example:

    int
    TclExampleObjCmd(dummy, interp, objc, objv)
         ClientData dummy;
         Tcl_Interp *interp;
         int objc;
         Tcl_Obj *const objv[];
    {
        char          *method;
        CHandlerSet   *handlerSet;
        int            methodIndex, result;
        simpleCounter *counter;

        static char *exampleMethods[] = {
            "enable", "getresult", "remove",
            NULL
        };
        enum exampleMethod {
            m_enable, m_getresult, m_remove
        };

        if (objc != 3) {
            Tcl_WrongNumArgs (interp, 1, objv, example_usage);
            return TCL_ERROR;
        }

        if (!CheckExpatParserObj (interp, objv[1])) {
            Tcl_SetResult (interp, "First argument has to be a expat parser object", NULL);
            return TCL_ERROR;
        }
        /* ... */

CHandlerSetGet returns a pointer to the C handler Set referenced by the name handlerSetName of the parser object expatObj. expatObj has to be an expat parser object in the interpreter interp. Returns NULL in case of error.

CHandlerSetGetUserData returns a pointer to the userData of the C handler set referenced by the name handlerSetName of the parser object expatObj. expatObj has to be an expat parser object in the interpreter interp. Returns NULL in case of error.

GetExpatInfo Is a helper function that returns a pointer to the TclGenExpatInfo structure of the tDOM Tcl expat parser object expatObj. The expatObj has to be a tDOM Tcl expat parser object in the interpreter interp. This is most useful, to set the application status of the parser object.

See the simple but full functionally example in the extensions/example dir or the more complex example tnc in the extensions/tnc dir (a simple DTD validation extension).

## SEE ALSO

expat

## KEYWORDS

C handler set