PCG32 based floating point random number generation

rand.c

/**
 * Generates a pseudorandom number, in the [0, 1[ interval.
 * @param rng Pointer to the pseudorandom number generator.
 */
static inline float rand_f(pcg32_random_t* rng)
{
  const uint32_t max = 1 << 24;
  uint32_t r = pcg32_random_r(rng);
  r &= max - 1;
  return r * 1.0f / max;
}

/**
 * Generates a pseudorandom number, in the [0, 1[ interval, rounded to the
 *   nearest multiple of 1/2^32.
 * @param rng Pointer to the pseudorandom number generator.
 */
static inline double rand_d32(pcg32_random_t* rng)
{
  union rand_double_t
  {
    uint64_t u;
    double d;
  };
  union rand_double_t u = { 0x3df0000000000000 }; // ldexp(1, -32);

  uint32_t r = pcg32_random_r(rng);

  return (double)r * u.d;
}

/**
 * Generates a pseudorandom number, in the [0, 1[ interval, rounded to the
 *   nearest multiple of 1/2^64.
 * @param rng Pointer to the pseudorandom number generator.
 */
static inline double rand_d64(pcg32_random_t* rng)
{
  union rand_double_t
  {
    uint64_t u;
    double d;
  };
  union rand_double_t u = { 0x3bf0000000000000 }; // ldexp(1, -64);

  uint64_t r = (uint64_t)pcg32_random_r(rng) << 32;
  pcg32_random_t rng_ = *rng;
  pcg32_random_t.inc += 2;
  r |= pcg32_random_r(&rng_);

  return (double)r * u.d;
}