endian.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/>.

#ifndef OPENVPN_COMMON_ENDIAN_H
#define OPENVPN_COMMON_ENDIAN_H

#include <openvpn/common/size.hpp>

// test for machine endiannes
#if defined(__BYTE_ORDER__) && defined(__ORDER_BIG_ENDIAN__) && defined(__ORDER_LITTLE_ENDIAN__)
#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
#define OPENVPN_BIG_ENDIAN
#elif __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
#define OPENVPN_LITTLE_ENDIAN
#endif
#elif defined(_WIN32)
#define OPENVPN_LITTLE_ENDIAN // assume that Windows is always little-endian
#endif

namespace openvpn {
  namespace Endian {
#   ifdef OPENVPN_LITTLE_ENDIAN
    inline size_t e16(const size_t v)
    {
      return v;
    }
    inline size_t e16rev(const size_t v)
    {
      return 15-v;
    }
    inline size_t e4(const size_t v)
    {
      return v;
    }
    inline size_t e4rev(const size_t v)
    {
      return 3-v;
    }
    inline size_t e2(const size_t v)
    {
      return v;
    }
    inline size_t e2rev(const size_t v)
    {
      return 1-v;
    }
#   elif OPENVPN_BIG_ENDIAN
    inline size_t e16rev(const size_t v)
    {
      return v;
    }
    inline size_t e16(const size_t v)
    {
      return 15-v;
    }
    inline size_t e4rev(const size_t v)
    {
      return v;
    }
    inline size_t e4(const size_t v)
    {
      return 3-v;
    }
    inline size_t e2rev(const size_t v)
    {
      return v;
    }
    inline size_t e2(const size_t v)
    {
      return 1-v;
    }
#   else
#   error One of OPENVPN_LITTLE_ENDIAN or OPENVPN_BIG_ENDIAN must be defined
#   endif
  }
} // namespace openvpn

#endif // OPENVPN_COMMON_ENDIAN_H