Function random_bounded_uint64_fill

numpy/random/src/distributions/distributions.c:1508–1567

* Fills an array with cnt random npy_uint64 between off and off + rng * inclusive. The numbers wrap if rng is sufficiently large. */

 * inclusive. The numbers wrap if rng is sufficiently large.
 */
void random_bounded_uint64_fill(bitgen_t *bitgen_state, uint64_t off,
                                uint64_t rng, npy_intp cnt, bool use_masked,
                                uint64_t *out) {
  npy_intp i;

  if (rng == 0) {
    for (i = 0; i < cnt; i++) {
      out[i] = off;
    }
  } else if (rng <= 0xFFFFFFFFUL) {
    /* Call 32-bit generator if range in 32-bit. */

    /*
     * The 32-bit Lemire method does not handle rng=0xFFFFFFFF, so we'll
     * call next_uint32 directly.  This also works when use_masked is True,
     * so we handle both cases here.
     */
    if (rng == 0xFFFFFFFFUL) {
      for (i = 0; i < cnt; i++) {
        out[i] = off + (uint64_t) next_uint32(bitgen_state);
      }
    } else {
      uint32_t buf = 0;
      int bcnt = 0;

      if (use_masked) {
        /* Smallest bit mask >= max */
        uint64_t mask = gen_mask(rng);

        for (i = 0; i < cnt; i++) {
          out[i] = off + buffered_bounded_masked_uint32(bitgen_state, rng, mask,
                                                        &bcnt, &buf);
        }
      } else {
        for (i = 0; i < cnt; i++) {
          out[i] = off +
                   buffered_bounded_lemire_uint32(bitgen_state, rng, &bcnt, &buf);
        }
      }
    }
  } else if (rng == 0xFFFFFFFFFFFFFFFFULL) {
    /* Lemire64 doesn't support rng = 0xFFFFFFFFFFFFFFFF. */
    for (i = 0; i < cnt; i++) {
      out[i] = off + next_uint64(bitgen_state);
    }
  } else {
    if (use_masked) {
      /* Smallest bit mask >= max */
      uint64_t mask = gen_mask(rng);

      for (i = 0; i < cnt; i++) {
        out[i] = off + bounded_masked_uint64(bitgen_state, rng, mask);
      }
    } else {
      for (i = 0; i < cnt; i++) {
        out[i] = off + bounded_lemire_uint64(bitgen_state, rng);
      }
    }