Annotation of OpenXM_contrib/gmp/mpz/divis_ui.c, Revision 1.1.1.1
1.1 ohara 1: /* mpz_divisible_ui_p -- mpz by ulong divisibility test.
2:
3: Copyright 2000, 2001, 2002 Free Software Foundation, Inc.
4:
5: This file is part of the GNU MP Library.
6:
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 2.1 of the License, or (at your
10: option) any later version.
11:
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.
16:
17: You should have received a copy of the GNU Lesser General Public License
18: along with the GNU MP Library; see the file COPYING.LIB. If not, write to
19: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
20: MA 02111-1307, USA. */
21:
22: #include "gmp.h"
23: #include "gmp-impl.h"
24: #include "longlong.h"
25:
26:
27: int
28: mpz_divisible_ui_p (mpz_srcptr a, unsigned long d)
29: {
30: mp_size_t asize;
31: mp_ptr ap;
32: unsigned twos;
33:
34: if (d == 0)
35: DIVIDE_BY_ZERO;
36:
37: asize = SIZ(a);
38: if (asize == 0) /* 0 divisible by any d */
39: return 1;
40:
41: /* For nails don't try to be clever if d is bigger than a limb, just fake
42: up an mpz_t and go to the main mpz_divisible_p. */
43: if (d > GMP_NUMB_MAX)
44: {
45: mp_limb_t dlimbs[2];
46: mpz_t dz;
47: ALLOC(dz) = 2;
48: PTR(dz) = dlimbs;
49: mpz_set_ui (dz, d);
50: return mpz_divisible_p (a, dz);
51: }
52:
53: ap = PTR(a);
54: asize = ABS(asize); /* ignore sign of a */
55:
56: if (BELOW_THRESHOLD (asize, MODEXACT_1_ODD_THRESHOLD))
57: return mpn_mod_1 (ap, asize, (mp_limb_t) d) == 0;
58:
59: if (! (d & 1))
60: {
61: /* Strip low zero bits to get odd d required by modexact. If d==e*2^n
62: and a is divisible by 2^n and by e, then it's divisible by d. */
63:
64: if ((ap[0] & LOW_ZEROS_MASK (d)) != 0)
65: return 0;
66:
67: count_trailing_zeros (twos, (mp_limb_t) d);
68: d >>= twos;
69: }
70:
71: return mpn_modexact_1_odd (ap, asize, (mp_limb_t) d) == 0;
72: }
FreeBSD-CVSweb <freebsd-cvsweb@FreeBSD.org>