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Annotation of OpenXM_contrib/gmp/mpz/cong_ui.c, Revision 1.1

1.1     ! ohara       1: /* mpz_congruent_ui_p -- test congruence of mpz and ulong.
        !             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: /* There's some explicit checks for c<d since it seems reasonably likely an
        !            28:    application might use that in a test.
        !            29:
        !            30:    Hopefully the compiler can generate something good for r==(c%d), though
        !            31:    if modexact is being used exclusively then that's not reached.  */
        !            32:
        !            33: int
        !            34: mpz_congruent_ui_p (mpz_srcptr a, unsigned long cu, unsigned long du)
        !            35: {
        !            36:   mp_srcptr  ap;
        !            37:   mp_size_t  asize;
        !            38:   mp_limb_t  c, d, r;
        !            39:
        !            40:   if (du == 0)
        !            41:     DIVIDE_BY_ZERO;
        !            42:
        !            43:   asize = SIZ(a);
        !            44:   if (asize == 0)
        !            45:     {
        !            46:       if (cu < du)
        !            47:         return cu == 0;
        !            48:       else
        !            49:         return (cu % du) == 0;
        !            50:     }
        !            51:
        !            52:   /* For nails don't try to be clever if c or d is bigger than a limb, just
        !            53:      fake up some mpz_t's and go to the main mpz_congruent_p.  */
        !            54:   if (du > GMP_NUMB_MAX || cu > GMP_NUMB_MAX)
        !            55:     {
        !            56:       mp_limb_t  climbs[2], dlimbs[2];
        !            57:       mpz_t      cz, dz;
        !            58:
        !            59:       ALLOC(cz) = 2;
        !            60:       PTR(cz) = climbs;
        !            61:       ALLOC(dz) = 2;
        !            62:       PTR(dz) = dlimbs;
        !            63:
        !            64:       mpz_set_ui (cz, cu);
        !            65:       mpz_set_ui (dz, du);
        !            66:       return mpz_congruent_p (a, cz, dz);
        !            67:     }
        !            68:
        !            69:   /* NEG_MOD works on limbs, so convert ulong to limb */
        !            70:   c = cu;
        !            71:   d = du;
        !            72:
        !            73:   if (asize < 0)
        !            74:     {
        !            75:       asize = -asize;
        !            76:       NEG_MOD (c, c, d);
        !            77:     }
        !            78:
        !            79:   ap = PTR (a);
        !            80:
        !            81:   if (BELOW_THRESHOLD (asize, MODEXACT_1_ODD_THRESHOLD))
        !            82:     {
        !            83:       r = mpn_mod_1 (ap, asize, d);
        !            84:       if (c < d)
        !            85:         return r == c;
        !            86:       else
        !            87:         return r == (c % d);
        !            88:     }
        !            89:
        !            90:   if ((d & 1) == 0)
        !            91:     {
        !            92:       /* Strip low zero bits to get odd d required by modexact.  If
        !            93:          d==e*2^n then a==c mod d if and only if both a==c mod 2^n
        !            94:          and a==c mod e.  */
        !            95:
        !            96:       unsigned  twos;
        !            97:
        !            98:       if ((ap[0]-c) & LOW_ZEROS_MASK (d))
        !            99:         return 0;
        !           100:
        !           101:       count_trailing_zeros (twos, d);
        !           102:       d >>= twos;
        !           103:     }
        !           104:
        !           105:   r = mpn_modexact_1c_odd (ap, asize, d, c);
        !           106:   return r == 0 || r == d;
        !           107: }