XML_Parser.h

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#ifndef __XML_PARSER_H__
#define __XML_PARSER_H__

#if !defined(CHAR_SIZE)
#    define CHAR_SIZE 8
#endif

#if (CHAR_SIZE!=8)
#   error EST can only handle 8 bit characters
#endif

#include "EST_String.h"
#include "EST_Regex.h"
#include "EST_TKVL.h"
#include "EST_THash.h"
#include "EST_TDeque.h"
#include "EST_TList.h"
#include "rxp/rxp.h"

// We only use types and functions from rxp.h, so we can throw away
// some of the macros which cause problems.

#undef get


/**@name XML Parser
  * Recursive descent parsing skeleton with hooks for processing.
  * A C++ wrapper around the rxp parser.
  * 
  * @author Richard Caley <rjc@cstr.ed.ac.uk>
  * @version $Id: XML_Parser.h,v 1.3 2004/05/04 00:00:17 awb Exp $
  */
//@{

class XML_Parser;
class XML_Parser_Class;

/// Nice name for list of attribute-value pairs.
typedef EST_TStringHash<EST_String> XML_Attribute_List;

/** A Class of parsers, All parsers share callbacks and a
  * list of known public IDs.
  */
class XML_Parser_Class {

private:

  /** Map PUBLIC and SYSTEM IDs to places on the local system.
    */
  EST_TKVL<EST_Regex, EST_String> known_ids;

protected:
  /** Do any necessary remappings and open a stream which reads the given
    * entity.
    */
  static InputSource open_entity(Entity ent, void *arg);
  

  /**@name The callbacks.
    * 
    * These methods can be overridden in a subclass to create a class
    * of parsers to do whatever you want.
    */
  //@{

  /** Called when starting a document.
    */
  virtual void document_open(XML_Parser_Class &c,
            XML_Parser &p,
            void *data);

  /** Called at the end of a document.
    */
  virtual void document_close(XML_Parser_Class &c,
             XML_Parser &p,
             void *data);
  
  /** Called when an element starts.
    */
  virtual void element_open(XML_Parser_Class &c,
               XML_Parser &p,
               void *data,
               const char *name,
               XML_Attribute_List &attributes);

  /** Called when an element ends.
    */
  virtual void element_close(XML_Parser_Class &c,
            XML_Parser &p,
            void *data,
            const char *name);

  /** Called for empty elements.
    *
    * Defaults to element_open(...) followed by element_closed(...).
    */
  virtual void element(XML_Parser_Class &c,
          XML_Parser &p,
          void *data,
          const char *name,
          XML_Attribute_List &attributes);

  /** Called for parsed character data sequences.
    */
  virtual void pcdata(XML_Parser_Class &c,
         XML_Parser &p,
         void *data,
         const char *chars);
  /** Called for unparsed character data sequences.
    */
  virtual void cdata(XML_Parser_Class &c,
        XML_Parser &p,
        void *data,
        const char *chars);

  /** Called for processing directives.
    */
  virtual void processing(XML_Parser_Class &c,
             XML_Parser &p,
             void *data,
             const char *instruction);

  /** Called when there is an error in parsing.
    */
  virtual void error(XML_Parser_Class &c,
        XML_Parser &p,
        void *data);
  //@}

  /** This can be called from any of the callbacks to present "message"
    * as an error through the error callback, thus getting filename and
    * line information into the message.
    */
  void error(XML_Parser_Class &c,
         XML_Parser &p,
         void *data,
         EST_String message);

  /// Get the error message for the last error.
  const char *get_error(XML_Parser &p);

public:

  /** Create an object representing the class of parsers. 
    */
  XML_Parser_Class();

  virtual ~XML_Parser_Class() { }

  /** Add a mapping from entity ID (SYSTEM or PUBLIC) to filename.
    * 
    * The string can contain escapes like \2 which are replaced by
    * the text matching the Nth bracketed part of the regular expression.
    */
  void register_id(EST_Regex id_pattern, EST_String directory);

  /** Fill in the list with the known entity ID mappings.
    */

  void registered_ids(EST_TList<EST_String> &list);

  /**@name Creating a parser
    * 
    * Each of these methods creates a one-shot parser which will run over the
    * indicated text.
    */
  //@{

  /// Create a parser for the RXP InputSource.
  XML_Parser *make_parser(InputSource source, void *data);

  /// Create a parser for the RXP InputSource.
  XML_Parser *make_parser(InputSource source, Entity initial_entity, void *data);

  /// Create a parser for a stdio input stream.
  XML_Parser *make_parser(FILE *input, void *data);

  /** Create a parser for a stdio input stream, giving  a description for
    * use in errors.
    */
  XML_Parser *make_parser(FILE *input, const EST_String desc, void *data);

  // Create a parser for the named file.
  XML_Parser *make_parser(const EST_String filename, void *data);

  //@}

  /** Utility which tries to open an entity called ID at places
    * specified in the mapping of this parser class.
    */

  InputSource try_and_open(Entity ent);
  
  /** XML_Parser defines the behaviour of an individual one-shot
    * parser.
    */
  friend class XML_Parser;
};

/** An actual parser. Each such instance parses just one stream which is
  * given when the parser is created. 
  *
  * The behaviour of the parser is given by the class to which it belongs.
  */

class XML_Parser {

private:
  /// Last error message from the parser.
  EST_String p_error_message;

  /// Set true when context is being remembered.
  bool p_track_context;

  /// Set true when contents is being remembered. (not yet implemented)
  bool p_track_contents;

protected:
  /** The class to which this parser belongs. Defines the behaviour of
    * the parser.
    */
  XML_Parser_Class *pclass;

  /// The piece of markup being processed.
  XBit current_bit;

  /// Where we are reading from.
  InputSource source;

  /** The entity we started from. May need to be freed at the end of the
    * parse.
    */
  Entity initial_entity;

  /// Arbitrary data which can be used by callbacks.
  void *data;

  /// The RXP parser object.
  Parser p;

  /// If context is being tracked, this is a stack of element names.
  EST_TDeque<EST_String> p_context;


  /// Creator used by XML_Parser_Class::make_parser()
  XML_Parser(XML_Parser_Class &parent, 
         InputSource source, 
         Entity initial_entity,
         void *data);

  /// Open. Asks the parser class to do the work.
  InputSource open(Entity ent);

  /// Get the error message for the last error.
  const char *get_error();

public:

  /// Destructor, may close input if required.
  ~XML_Parser();

  /** Request that parser keep track of the currently open elements.
    * 
    * These are recorded on a atsck. Use context() to access the information.
    */
  void track_context(bool flag);
  /** Keep track of the content of open elements.
    *
    * Not yet implemented.
    */
  void track_contents(bool flag);

  /** Get the name of the nth enclosing element.
    * 
    * context(0) is the element we are directly inside.
    */
  EST_String context(int n);

  /// Run the parser. 
  void go();

  friend class XML_Parser_Class;
};

//@}

#endif