randomizer.I

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/**
 * PANDA 3D SOFTWARE
 * Copyright (c) Carnegie Mellon University.  All rights reserved.
 *
 * All use of this software is subject to the terms of the revised BSD
 * license.  You should have received a copy of this license along
 * with this source code in a file named "LICENSE."
 *
 * @file randomizer.I
 * @author drose
 * @date 2007-01-18
 */

/**
 * If seed is nonzero, it is used to define the tables; if it is zero a random
 * seed is generated.
 */
Randomizer::
Randomizer(unsigned long seed) :
  _mersenne(seed != 0 ? seed : get_next_seed())
{
}

/**
 *
 */
Randomizer::
Randomizer(const Randomizer &copy) :
  _mersenne(copy._mersenne)
{
}

/**
 *
 */
void Randomizer::
operator = (const Randomizer &copy) {
  _mersenne = copy._mersenne;
}

/**
 * Returns a random integer in the range [0, range).
 */
INLINE int Randomizer::
random_int(int range) {
  return (int)floor(random_real((double)range));
}

/**
 * Returns a random double in the range [0, range).
 */
INLINE double Randomizer::
random_real(double range) {
  return (range * _mersenne.get_uint31()) / ((double)0x80000000);
}

/**
 * Returns a random double in the range [-0.5, 0.5).
 */
INLINE double Randomizer::
random_real_unit() {
  return random_real(1.0f) - 0.5f;
}

/**
 * Returns a random seed value for the next global Randomizer object.
 */
INLINE unsigned long Randomizer::
get_next_seed() {
  if (!_got_first_seed) {
    _next_seed = Mersenne((unsigned long)time(nullptr));
    _got_first_seed = true;
  }
  return _next_seed.get_uint31();
}

/**
 * Returns a unique seed value based on the seed value passed to this
 * Randomizer object (and on its current state).
 */
INLINE unsigned long Randomizer::
get_seed() {
  return _mersenne.get_uint31();
}