1 /* mpz_divisible_2exp_p -- mpz by 2^n divisibility test
3 Copyright 2001, 2002 Free Software Foundation, Inc.
5 This file is part of the GNU MP Library.
7 The GNU MP Library is free software; you can redistribute it and/or modify
8 it under the terms of the GNU Lesser General Public License as published by
9 the Free Software Foundation; either version 3 of the License, or (at your
10 option) any later version.
12 The GNU MP Library is distributed in the hope that it will be useful, but
13 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
14 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
15 License for more details.
17 You should have received a copy of the GNU Lesser General Public License
18 along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. */
25 mpz_divisible_2exp_p (mpz_srcptr a, mp_bitcnt_t d) __GMP_NOTHROW
34 dlimbs = d / GMP_NUMB_BITS;
36 /* if d covers the whole of a, then only a==0 is divisible */
40 /* whole limbs must be zero */
42 for (i = 0; i < dlimbs; i++)
46 /* left over bits must be zero */
47 dbits = d % GMP_NUMB_BITS;
48 dmask = (CNST_LIMB(1) << dbits) - 1;
49 return (ap[dlimbs] & dmask) == 0;