1 /* mpz_congruent_ui_p -- test congruence of mpz and ulong.
3 Copyright 2000, 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 /* There's some explicit checks for c<d since it seems reasonably likely an
26 application might use that in a test.
28 Hopefully the compiler can generate something good for r==(c%d), though
29 if modexact is being used exclusively then that's not reached. */
32 mpz_congruent_ui_p (mpz_srcptr a
, unsigned long cu
, unsigned long du
)
38 if (UNLIKELY (du
== 0))
39 return (mpz_cmp_ui (a
, cu
) == 0);
47 return (cu
% du
) == 0;
50 /* For nails don't try to be clever if c or d is bigger than a limb, just
51 fake up some mpz_t's and go to the main mpz_congruent_p. */
52 if (du
> GMP_NUMB_MAX
|| cu
> GMP_NUMB_MAX
)
54 mp_limb_t climbs
[2], dlimbs
[2];
64 return mpz_congruent_p (a
, cz
, dz
);
67 /* NEG_MOD works on limbs, so convert ulong to limb */
79 if (ABOVE_THRESHOLD (asize
, BMOD_1_TO_MOD_1_THRESHOLD
))
81 r
= mpn_mod_1 (ap
, asize
, d
);
90 /* Strip low zero bits to get odd d required by modexact. If
91 d==e*2^n then a==c mod d if and only if both a==c mod 2^n
96 if ((ap
[0]-c
) & LOW_ZEROS_MASK (d
))
99 count_trailing_zeros (twos
, d
);
103 r
= mpn_modexact_1c_odd (ap
, asize
, d
, c
);
104 return r
== 0 || r
== d
;