parser.hh

2007年机器人足球世界杯3D仿真组亚军

/*
 *  Little Green BATS (2006)
 *
 *  Authors: 	Martin Klomp ([e-mail])
 *		Mart van de Sanden ([e-mail])
 *		Sander van Dijk ([e-mail])
 *		A. Bram Neijt ([e-mail])
 *		Matthijs Platje ([e-mail])
 *
 *  Date: 	September 14, 2006
 *
 *  Website:	http://www.littlegreenbats.nl
 *
 *  Comment:	Please feel free to contact us if you have any 
 *		problems or questions about the code.
 *
 *
 *  License: 	This program is free software; you can redistribute 
 *		it and/or modify it under the terms of the GNU General
 *		Public License as published by the Free Software 
 *		Foundation; either version 2 of the License, or (at 
 *		your option) any later version.
 *
 *   		This program is distributed in the hope that it will
 *		be useful, but WITHOUT ANY WARRANTY; without even the
 *		implied warranty of MERCHANTABILITY or FITNESS FOR A
 *		PARTICULAR PURPOSE.  See the GNU General Public
 *		License for more details.
 *
 *   		You should have received a copy of the GNU General
 *		Public License along with this program; if not, write
 *		to the Free Software Foundation, Inc., 59 Temple Place - 
 *		Suite 330, Boston, MA  02111-1307, USA.
 *
 */







#ifndef __INC_RCP_PARSER_HH_
#define __INC_RCP_PARSER_HH_

#include <string>
#include <stack>
#include "predicate.hh"

namespace bats {

  /**\brief Communication parser
         * 
   *  The parser...
   *
   *  \todo Issues:
   *  - The parser uses a recursive algorithm, that means that if
   *    a suficiently large message is parsed it might trigger
   *    a stack overload. How much do we trust the soccer server?
   *
   *  The parser is used to parse the communication messages (the lisp like language)
   *  to a Predicate (tree like structure @see Predicate).
   *
   */
  class Parser {

    Parser(Parser const &); // NI
    Parser &operator=(Parser const &); // NI

    /// The token type.
    struct Token {

      enum Type {
        none = 0,    ///< Not a token.
        error = 1,   ///< Error token.
        lparent = 2, ///< '('
        rparent = 3, ///< ')'
        ws = 4,      ///< White space
        id = 5,      ///< Everything that is not a ' ','(' or ')' (or: identifier).
        end_of_line = 6 ///< The end of the line.
      };

      Type type;
      std::string value;
      
    };

    /// Lexer Table element.
    struct LexTable {
      unsigned state0;
      char r0;
      char r1;
      unsigned state1;
    };

    /// Token table element.
    struct TokenTable {
      unsigned state;
      Token::Type token;
    };

    // The lexerTable contains all the fsa state changes.
    static LexTable lexerTable[];

    // The tokenTable contains all the end states with token type.
    static TokenTable tokenTable[];

    // returns state <- state when chr
    unsigned lexerNextState(unsigned state, char chr);

    // if the current state is an end state it
    // return the token associated with it (@see tokenTable)
    // otherwise it returns a token with type Token::none.
    Token::Type isEndState(unsigned state);

    // The lex stack keeps the pushBacks.
    std::stack<Token> lex_stack;

    // This is the string that is currently being lexed.
    std::string lex_source;

    // The iterator over the lex_source string.
    std::string::iterator lex_iter;

    // The current lexer state.
    unsigned lex_state;

    // Initializes the lexer src is the string to be lexed.
    void initLex(std::string src);

    // Gives the next token (it ignores whitespaces (' '|'\t').
    Token lex();

    // Pushes one token back unto the lex stack. The
    // lex() method will return that token the next time
    // it is called.
    void lexPushBack(Token const &_t)
    { lex_stack.push(_t); }

    // De predicate parser method.
    rPredicate parsePred();

  public:

    Parser();

    /**
     *  Parses _msg into a Predicate.
     *  @returns the parsed message.
     *  @throws parser_error (@see global.hh)
     */
    rPredicate parse(std::string const &_msg);

    /**
     *  Generates a lisp like expression of
     *  the message, which can be send to the
     *  simulation server.
     */
    std::string generate(rPredicate const &_pred);

  };

};

#endif // __INC_RBATS_PARSER_HH_