/* BSD 3-Clause License
 *
 * Copyright © 2008-2020, Jice and the libtcod contributors.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * 3. Neither the name of the copyright holder nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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 */
#ifndef LIBTCOD_RANDOM_H_
#define LIBTCOD_RANDOM_H_
#include <stdint.h>

#include "config.h"

#ifdef __cplusplus
extern "C" {
#endif  // __cplusplus
/**
    Return the next random uint64_t from a SplitMix64 generator.

    `state[1]` is a non-NULL pointer to the internal state of the generator.
    There is no initializer function because the first value of `state[1]` is
    itself the seed which can start at any value.
    `state[1]` will be updated by this call.
    \rst
    .. versionadded:: 1.16
    \endrst
 */
TCOD_PUBLIC inline uint64_t TCOD_rng_splitmix64_next(uint64_t* state) {
  // Based on http://xoshiro.di.unimi.it/splitmix64.c
  uint64_t z = (*state += 0x9e3779b97f4a7c15);
  z = (z ^ (z >> 30)) * 0xbf58476d1ce4e5b9;
  z = (z ^ (z >> 27)) * 0x94d049bb133111eb;
  return z ^ (z >> 31);
}
#ifdef __cplusplus
}  // extern "C"
#endif  // __cplusplus
#endif  // LIBTCOD_RANDOM_H_
