//    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) 2012-2020 OpenVPN Inc.
//
//    This program is free software: you can redistribute it and/or modify
//    it under the terms of the GNU Affero 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 Affero General Public License for more details.
//
//    You should have received a copy of the GNU Affero General Public License
//    along with this program in the COPYING file.
//    If not, see <http://www.gnu.org/licenses/>.

#ifndef OPENVPN_RANDOM_RANDBYTESTORE_H
#define OPENVPN_RANDOM_RANDBYTESTORE_H

#include <openvpn/common/size.hpp>

namespace openvpn {

  template <typename RAND_TYPE>
  class RandomByteStore
  {
  public:
    static constexpr size_t SIZE = sizeof(typename RAND_TYPE::result_type);

    unsigned char get_byte(RAND_TYPE& rng)
    {
      if (n_bytes == 0)
	{
	  res.rt = rng();
	  n_bytes = SIZE;
	}
      unsigned char ret = res.bytes[0];
      res.rt >>= 8;
      --n_bytes;
      return ret;
    }

    template <typename T>
    void fill(T& obj, RAND_TYPE& rng)
    {
      unsigned char *data = reinterpret_cast<unsigned char *>(&obj);
      for (size_t i = 0; i < sizeof(obj); ++i)
	data[i] = get_byte(rng);
    }

  private:
    union Result {
      unsigned char bytes[SIZE];
      typename RAND_TYPE::result_type rt;
    };

    Result res;
    unsigned int n_bytes = 0;
  };

}
#endif