/* mpz_divisible_ui_p -- mpz by ulong divisibility test.

Copyright 2000-2002 Free Software Foundation, Inc.

This file is part of the GNU MP Library.

The GNU MP Library is free software; you can redistribute it and/or modify

it under the terms of either:

  * the GNU Lesser General Public License as published by the Free

    Software Foundation; either version 3 of the License, or (at your

    option) any later version.

or

  * 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.

or both in parallel, as here.

The GNU MP Library 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 copies of the GNU General Public License and the

GNU Lesser General Public License along with the GNU MP Library.  If not,

see https://www.gnu.org/licenses/.  */

#include "gmp.h"

#include "gmp-impl.h"

#include "longlong.h"

int

mpz_divisible_ui_p (mpz_srcptr a, unsigned long d)

{

  mp_size_t  asize;

  mp_ptr     ap;

  unsigned   twos;

  asize = SIZ(a);

  if (UNLIKELY (d == 0))

    return (asize == 0);

  if (asize == 0)  /* 0 divisible by any d */

    return 1;

  /* For nails don't try to be clever if d is bigger than a limb, just fake

     up an mpz_t and go to the main mpz_divisible_p.  */

  if (d > GMP_NUMB_MAX)

    {

      mp_limb_t  dlimbs[2];

      mpz_t      dz;

      ALLOC(dz) = 2;

      PTR(dz) = dlimbs;

      mpz_set_ui (dz, d);

      return mpz_divisible_p (a, dz);

    }

  ap = PTR(a);

  asize = ABS(asize);  /* ignore sign of a */

  if (ABOVE_THRESHOLD (asize, BMOD_1_TO_MOD_1_THRESHOLD))

    return mpn_mod_1 (ap, asize, (mp_limb_t) d) == 0;

  if (! (d & 1))

    {

      /* Strip low zero bits to get odd d required by modexact.  If d==e*2^n

	 and a is divisible by 2^n and by e, then it's divisible by d. */

      if ((ap[0] & LOW_ZEROS_MASK (d)) != 0)

	return 0;

      count_trailing_zeros (twos, (mp_limb_t) d);

      d >>= twos;

    }

  return mpn_modexact_1_odd (ap, asize, (mp_limb_t) d) == 0;

}