aria2/src/SimpleRandomizer.h

/* <!-- copyright */
/*
 * aria2 - The high speed download utility
 *
 * Copyright (C) 2006 Tatsuhiro Tsujikawa
 *
 * 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 *
 * In addition, as a special exception, the copyright holders give
 * permission to link the code of portions of this program with the
 * OpenSSL library under certain conditions as described in each
 * individual source file, and distribute linked combinations
 * including the two.
 * You must obey the GNU General Public License in all respects
 * for all of the code used other than OpenSSL.  If you modify
 * file(s) with this exception, you may extend this exception to your
 * version of the file(s), but you are not obligated to do so.  If you
 * do not wish to do so, delete this exception statement from your
 * version.  If you delete this exception statement from all source
 * files in the program, then also delete it here.
 */
/* copyright --> */
#ifndef D_SIMPLE_RANDOMIZER_H
#define D_SIMPLE_RANDOMIZER_H

#include "Randomizer.h"

#include <memory>
#include <random>

#ifdef __MINGW32__
#include <wincrypt.h>
#endif

namespace aria2 {

class SimpleRandomizer : public Randomizer {
private:
  static std::unique_ptr<SimpleRandomizer> randomizer_;
  SimpleRandomizer();

private:
#ifdef __MINGW32__
  HCRYPTPROV provider_;
#else
  std::mt19937 gen_;
#endif // ! __MINGW32__

public:
  typedef std::mt19937::result_type result_type;

  static const std::unique_ptr<SimpleRandomizer>& getInstance();

  virtual ~SimpleRandomizer();

  /**
   * Returns random number in [0, to).
   */
  virtual long int getRandomNumber(long int to) CXX11_OVERRIDE;

  void getRandomBytes(unsigned char* buf, size_t len);

  long int operator()(long int to) { return getRandomNumber(to); }

  result_type operator()()
  {
    result_type rv;
    getRandomBytes(reinterpret_cast<unsigned char*>(&rv), sizeof(rv));
    return rv;
  }

  static constexpr result_type min()
  {
    return std::numeric_limits<result_type>::min();
  }

  static constexpr result_type max()
  {
    return std::numeric_limits<result_type>::max();
  }

  static double entropy() { return 0.0; }
};

} // namespace aria2

#endif // D_SIMPLE_RANDOMIZER_H