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/*                                                SGML parse and stream definition for libwww
                               SGML AND STRUCTURED STREAMS
   The SGML parser is a state machine. It is called for every character
   of the input stream. The DTD data structure contains pointers
   to functions which are called to implement the actual effect of the
   text read. When these functions are called, the attribute structures pointed to by the
   DTD are valid, and the function is passed a pointer to the curent tag structure, and an
   "element stack" which represents the state of nesting within SGML elements.
   The following aspects are from Dan Connolly's suggestions:  Binary search, Strcutured
   object scheme basically, SGML content enum type.
   (c) Copyright CERN 1991 - See Copyright.html

#ifndef SGML_H
#define SGML_H

#include "HTUtils.h"
#include "HTStream.h"


SGML content types


typedef enum _SGMLContent{
  SGML_EMPTY,    /* no content */
  SGML_LITTERAL, /* character data. Recognised excat close tag only. litteral
                    Old www server compatibility only! Not SGML */

  SGML_CDATA,    /* character data. recognize </ only */
  SGML_RCDATA,   /* replaceable character data. recognize </ and &ref; */
  SGML_MIXED,    /* elements and parsed character data. recognize all markup */
  SGML_ELEMENT   /* any data found will be returned as an error*/
  } SGMLContent;

typedef struct {
    char *      name;           /* The (constant) name of the attribute */
                                /* Could put type info in here */
} attr;

/*              A tag structure describes an SGML element.
**              -----------------------------------------
**      name            is the string which comes after the tag opener "<".
**      attributes      points to a zero-terminated array
**                      of attribute names.
**      litteral        determines how the SGML engine parses the charaters
**                      within the element. If set, tag openers are ignored
**                      except for that which opens a matching closing tag.

typedef struct _tag HTTag;
struct _tag{
    char *      name;                   /* The name of the tag */
    attr *      attributes;             /* The list of acceptable attributes */
    int         number_of_attributes;   /* Number of possible attributes */
    SGMLContent contents;               /* End only on end tag @@ */
    int *       valid_sub_elements;     /* Necessary to determine implied end
                                           tags. Solves @@ problem. (PYW)*/

    int         valid_sub_elementsCount;/*PYW*/

/*              DTD Information
**              ---------------
** Not the whole DTD, but all this parser usues of it.

typedef struct {
    HTTag *             tags;           /* Must be in strcmp order by name */
    int                 number_of_tags;
    CONST char **       entity_names;   /* Must be in strcmp order by name */
    int                 number_of_entities;
} SGML_dtd;

/*      SGML context passed to parsers

typedef struct _HTSGMLContext *HTSGMLContext;   /* Hidden */



Structured Object definition

   A structured object is something which can reasonably be represented in SGML.  I'll
   rephrase that.  A structured object is am ordered tree-structured arrangement of data
   which is representable as text.The SGML parer outputs to a Structured object. A
   Structured object can output its contents to another Structured Object. It's a kind of
   typed stream. The architecure is largely Dan Conolly's. Elements and entities are
   passed to the sob by number, implying a knowledge of the DTD. Knowledge of the SGML
   syntax is not here, though.
   Superclass: HTStream
   The creation methods will vary on the type of Structured Object.Maybe the callerData is
   enough info to pass along.

typedef struct _HTStructured HTStructured;

typedef struct _HTStructuredClass{

        char*  name;                            /* Just for diagnostics */

        void (*free) PARAMS((
                HTStructured*   me));

        void (*end) PARAMS((                    /*PYW*/
                HTStructured*   me));
        void (*abort) PARAMS((
                HTStructured*   me,
                HTError         e));
        void (*put_character) PARAMS((
                HTStructured*   me,
                char            ch));
        void (*put_string) PARAMS((
                HTStructured*   me,
                CONST char *    str));
        void (*progress) PARAMS((
                HTStructured*   me,
                int             n));
        void (*write) PARAMS((
                HTStructured*   me,
                CONST char *    str,
                int             len));
        void (*start_element) PARAMS((
                HTStructured*   me,
                int             element_number,
                CONST BOOL*     attribute_present,
                CONST char**    attribute_value,
                HTTag*          tagInfo)); /*PYW*/
        void (*end_element) PARAMS((
                HTStructured*   me,
                int             element_number));

        void (*put_entity) PARAMS((
                HTStructured*   me,
                int             entity_number));


Find a Tag by Name

   Returns a pointer to the tag within the DTD.

extern HTTag * SGMLFindTag PARAMS((CONST SGML_dtd* dtd, CONST char * string));


Create an SGML parser


** On entry,
**      dtd             must point to a DTD structure as defined above
**      callbacks       must point to user routines.
**      callData        is returned in callbacks transparently.
** On exit,
**              The default tag starter has been processed.

extern HTStream* SGML_new PARAMS((
        CONST SGML_dtd *                dtd,
        HTStructured *          target));

extern CONST HTStreamClass SGMLParser;

#endif  /* SGML_H */