elexscanner.h

用于词法分析的词法分析器

/*
  $Id: ElexScanner.h,v 1.9 1997/03/19 12:16:02 matt Exp $

  Default Elex scanner class.

  (c) Matt Phillips 1996.
  */

#ifndef _ELEX_SCAN_H
#define _ELEX_SCAN_H

#include <std/string.h>
#include <compiler/ErrorMessage.h>
#include <contain/CircularQueue.h>

#include "XInputStream.h"
#include "ElexScannerBase.h"

class ElexScanner : public ElexScannerBase
{
public:

  ElexScanner (ElexScannerData &d, XInputStream &i, int lookahead = 1);

  XInputStream &getInput () {return input;}

  virtual int getNext ();

  virtual string &getText () {return text;}
  virtual const string &getText () const {return text;}

  int getTextLine () const {return symbolLine;}
  int getTextColumn () const {return symbolColumn;}

  virtual void error (const string &message);
  virtual void warning (const string &message);

  const ErrorMessageList &getErrors () const {return errors;}

protected:

  // mark used to allow scanner to backtrack.
  class BacktrackMark
  {
  public:

    BacktrackMark () {}

    // place mark at current point in s.
    void mark (const ElexScanner &s);

    // sets stream to be at this mark.
    void jump (ElexScanner &s) const;

    int isValid (const ElexScanner &s) const
    {
      return streamMark.isValid (s.input);
    }

  protected:

    XInputStream::BacktrackMark streamMark;
    const ElexState *state;
    int symbolCount;
  };

  // mark used to mark the start/end of symbols in the stream.
  class SymbolMark
  {
  public:

    int production;
    XInputStream::BacktrackMark mark;
    int markCount;

    int operator > (const SymbolMark &m) const {return mark > m.mark;}
  };

  // used to store frozen symbols.
  class Symbol
  {
  public:
    string text;
    int production;
    int line, column;
  };

  typedef CircularQueue<SymbolMark> SymbolMarkStack;
  typedef CircularQueue<BacktrackMark> BacktrackMarkStack;
  typedef CircularQueue<Symbol> SymbolStack;

  const ElexState *state;
  XInputStream &input;
  ErrorMessageList errors;
  string text;
  int symbolLine, symbolColumn;

  int lookahead;
  BacktrackMarkStack marks;	// backtrack marks
  SymbolMarkStack symbolMarks;	// currently matched symbols
  SymbolMarkStack bestMatch;	// the best match so far
  SymbolStack symbols;		// frozen symbols

  static const ElexState eofState; // used to reprsent EOF condition

  void reset ();
  void primeSymbols ();

  void handleNoAccept ();

  void mark ();
  void freeze (SymbolMarkStack &symbolMarkStack);
  void makeCurrent (const Symbol &sym);
  int backtrack ();
  void match (int production);

  virtual int invokeProduction (int i) = 0;

  friend class ElexScanner::BacktrackMark;
};

#endif