/* <!-- 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 --> */
#include "SimpleRandomizer.h"

#include <sys/types.h>
#include <unistd.h>
#include <cstdlib>
#include <cassert>
#include <cstring>

#include "a2time.h"
#include "a2functional.h"

#ifdef HAVE_GETRANDOM_INTERFACE
#  include "getrandom_linux.h"
#endif

namespace aria2 {

std::unique_ptr<SimpleRandomizer> SimpleRandomizer::randomizer_;

const std::unique_ptr<SimpleRandomizer>& SimpleRandomizer::getInstance()
{
  if(!randomizer_) {
    randomizer_.reset(new SimpleRandomizer());
  }
  return randomizer_;
}

SimpleRandomizer::SimpleRandomizer()
{
#ifdef __MINGW32__
  BOOL r = ::CryptAcquireContext(
      &provider_,
      0, 0, PROV_RSA_FULL,
      CRYPT_VERIFYCONTEXT | CRYPT_SILENT);
  assert(r);
#endif
}

SimpleRandomizer::~SimpleRandomizer()
{
#ifdef __MINGW32__
  CryptReleaseContext(provider_, 0);
#endif
}

long int SimpleRandomizer::getRandomNumber(long int to)
{
  assert(to > 0);
  return std::uniform_int_distribution<long int>(0, to - 1)(*this);
}

void SimpleRandomizer::getRandomBytes(unsigned char* buf, size_t len)
{
#ifdef __MINGW32__
  BOOL r = CryptGenRandom(provider_, len, reinterpret_cast<BYTE*>(buf));
  assert(r);
#elif defined(HAVE_GETRANDOM_INTERFACE)
  auto rv = getrandom_linux(buf, len);
  assert(rv >= 0 && (size_t)rv == len);
#else // ! __MINGW32__
  auto ubuf = reinterpret_cast<result_type*>(buf);
  size_t q = len / sizeof(result_type);
  auto gen = std::uniform_int_distribution<result_type>();
  for(; q > 0; --q, ++ubuf) {
    *ubuf = gen(dev_);
  }
  const size_t r = len % sizeof(result_type);
  auto last = gen(dev_);
  memcpy(ubuf, &last, r);
#endif // ! __MINGW32__
}

} // namespace aria2
