Annotation of OpenXM_contrib/gmp/mpz/divis_ui.c, Revision 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: }
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