lex.hpp

//    OpenVPN -- An application to securely tunnel IP networks
//               over a single port, with support for SSL/TLS-based
//               session authentication and key exchange,
//               packet encryption, packet authentication, and
//               packet compression.
//
//    Copyright (C) 2012-2017 OpenVPN Technologies, Inc.
//
//    This program is free software: you can redistribute it and/or modify
//    it under the terms of the GNU General Public License Version 3
//    as published by the Free Software Foundation.
//
//    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 in the COPYING file.
//    If not, see <http://www.gnu.org/licenses/>.

// A set of lexical analyzer classes.  These classes can be combined
// with the methods in split.hpp to create parsers.

#ifndef OPENVPN_COMMON_LEX_H
#define OPENVPN_COMMON_LEX_H

#include <openvpn/common/string.hpp>

namespace openvpn {

  // This class (or others that define an is_space method) is used as a
  // template parameter to methods in split.hpp.
  struct SpaceMatch
  {
    static bool is_space(char c)
    {
      return string::is_space(c);
    }
  };

  // A basic lexical analyzer that understands quoting
  class StandardLex
  {
  public:
    StandardLex() : in_quote_(false), backslash(false), ch(-1) {}

    void put(char c)
    {
      if (backslash)
	{
	  ch = c;
	  backslash = false;
	}
      else if (c == '\\')
	{
	  backslash = true;
	  ch = -1;
	}
      else if (c == '\"')
	{
	  in_quote_ = !in_quote_;
	  ch = -1;
	}
      else
	{
	  ch = c;
	}
    }

    bool available() const { return ch != -1; }
    int get() const { return ch; }
    void reset() { ch = -1; }

    bool in_quote() const { return in_quote_; }

  private:
    bool in_quote_;
    bool backslash;
    int ch;
  };

  // A null lexical analyzer has no special understanding
  // of any particular string character.
  class NullLex
  {
  public:
    NullLex() : ch(-1) {}

    void put(char c) { ch = c; }
    bool available() const { return ch != -1; }
    int get() const { return ch; }
    void reset() { ch = -1; }
    bool in_quote() const { return false; }

  private:
    int ch;
  };

} // namespace openvpn

#endif // OPENVPN_COMMON_LEX_H