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Annotation of OpenXM_contrib/gmp/mpz/divexact.c, Revision 1.1.1.2

1.1       maekawa     1: /* mpz_divexact -- finds quotient when known that quot * den == num && den != 0.
                      2:
1.1.1.2 ! maekawa     3: Copyright (C) 1991, 1993, 1994, 1995, 1996, 1997, 1998, 2000 Free Software
        !             4: Foundation, Inc.
1.1       maekawa     5:
                      6: This file is part of the GNU MP Library.
                      7:
                      8: The GNU MP Library is free software; you can redistribute it and/or modify
1.1.1.2 ! maekawa     9: it under the terms of the GNU Lesser General Public License as published by
        !            10: the Free Software Foundation; either version 2.1 of the License, or (at your
1.1       maekawa    11: option) any later version.
                     12:
                     13: The GNU MP Library is distributed in the hope that it will be useful, but
                     14: WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
1.1.1.2 ! maekawa    15: or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
1.1       maekawa    16: License for more details.
                     17:
1.1.1.2 ! maekawa    18: You should have received a copy of the GNU Lesser General Public License
1.1       maekawa    19: along with the GNU MP Library; see the file COPYING.LIB.  If not, write to
                     20: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
                     21: MA 02111-1307, USA.  */
                     22:
                     23: /*  Ken Weber (kweber@mat.ufrgs.br, kweber@mcs.kent.edu)
                     24:
                     25:     Funding for this work has been partially provided by Conselho Nacional
                     26:     de Desenvolvimento Cienti'fico e Tecnolo'gico (CNPq) do Brazil, Grant
                     27:     301314194-2, and was done while I was a visiting reseacher in the Instituto
                     28:     de Matema'tica at Universidade Federal do Rio Grande do Sul (UFRGS).
                     29:
                     30:     References:
1.1.1.2 ! maekawa    31:        T. Jebelean, An algorithm for exact division, Journal of Symbolic
        !            32:        Computation, v. 15, 1993, pp. 169-180.  */
1.1       maekawa    33:
                     34: #include "gmp.h"
                     35: #include "gmp-impl.h"
                     36: #include "longlong.h"
                     37:
                     38: void
                     39: #if __STDC__
                     40: mpz_divexact (mpz_ptr quot, mpz_srcptr num, mpz_srcptr den)
                     41: #else
                     42: mpz_divexact (quot, num, den)
                     43:      mpz_ptr quot;
                     44:      mpz_srcptr num;
                     45:      mpz_srcptr den;
                     46: #endif
                     47: {
                     48:   mp_ptr qp, tp;
                     49:   mp_size_t qsize, tsize;
1.1.1.2 ! maekawa    50:   mp_srcptr np, dp;
        !            51:   mp_size_t nsize, dsize;
1.1       maekawa    52:   TMP_DECL (marker);
                     53:
1.1.1.2 ! maekawa    54:   nsize = ABS (num->_mp_size);
        !            55:   dsize = ABS (den->_mp_size);
        !            56:
        !            57:   qsize = nsize - dsize + 1;
        !            58:   if (quot->_mp_alloc < qsize)
        !            59:     _mpz_realloc (quot, qsize);
        !            60:
        !            61:   np = num->_mp_d;
        !            62:   dp = den->_mp_d;
        !            63:   qp = quot->_mp_d;
1.1       maekawa    64:
                     65:   if (nsize == 0)
                     66:     {
1.1.1.2 ! maekawa    67:       if (dsize == 0)
        !            68:        DIVIDE_BY_ZERO;
1.1       maekawa    69:       quot->_mp_size = 0;
                     70:       return;
                     71:     }
                     72:
1.1.1.2 ! maekawa    73:   if (dsize <= 1)
        !            74:     {
        !            75:       if (dsize == 1)
        !            76:        {
        !            77:          mpn_divmod_1 (qp, np, nsize, dp[0]);
        !            78:          qsize -= qp[qsize - 1] == 0;
        !            79:          quot->_mp_size = (num->_mp_size ^ den->_mp_size) >= 0 ? qsize : -qsize;
        !            80:          return;
        !            81:        }
        !            82:
        !            83:       /*  Generate divide-by-zero error since dsize == 0.  */
        !            84:       DIVIDE_BY_ZERO;
        !            85:     }
1.1       maekawa    86:
                     87:   TMP_MARK (marker);
                     88:
                     89:   /*  QUOT <-- NUM/2^r, T <-- DEN/2^r where = r number of twos in DEN.  */
                     90:   while (dp[0] == 0)
                     91:     np += 1, nsize -= 1, dp += 1, dsize -= 1;
                     92:   tsize = MIN (qsize, dsize);
1.1.1.2 ! maekawa    93:   if ((dp[0] & 1) != 0)
1.1       maekawa    94:     {
1.1.1.2 ! maekawa    95:       if (quot == den)         /*  QUOT and DEN overlap.  */
1.1       maekawa    96:        {
1.1.1.2 ! maekawa    97:          tp = (mp_ptr) TMP_ALLOC (tsize * BYTES_PER_MP_LIMB);
1.1       maekawa    98:          MPN_COPY (tp, dp, tsize);
                     99:        }
                    100:       else
                    101:        tp = (mp_ptr) dp;
1.1.1.2 ! maekawa   102:       if (qp != np)
        !           103:        MPN_COPY_INCR (qp, np, qsize);
1.1       maekawa   104:     }
                    105:   else
                    106:     {
1.1.1.2 ! maekawa   107:       unsigned int r;
        !           108:       tp = (mp_ptr) TMP_ALLOC (tsize * BYTES_PER_MP_LIMB);
1.1       maekawa   109:       count_trailing_zeros (r, dp[0]);
                    110:       mpn_rshift (tp, dp, tsize, r);
                    111:       if (dsize > tsize)
1.1.1.2 ! maekawa   112:        tp[tsize - 1] |= dp[tsize] << (BITS_PER_MP_LIMB - r);
1.1       maekawa   113:       mpn_rshift (qp, np, qsize, r);
                    114:       if (nsize > qsize)
1.1.1.2 ! maekawa   115:        qp[qsize - 1] |= np[qsize] << (BITS_PER_MP_LIMB - r);
1.1       maekawa   116:     }
                    117:
                    118:   /*  Now QUOT <-- QUOT/T.  */
                    119:   mpn_bdivmod (qp, qp, qsize, tp, tsize, qsize * BITS_PER_MP_LIMB);
                    120:   MPN_NORMALIZE (qp, qsize);
                    121:
1.1.1.2 ! maekawa   122:   quot->_mp_size = (num->_mp_size ^ den->_mp_size) >= 0 ? qsize : -qsize;
1.1       maekawa   123:
                    124:   TMP_FREE (marker);
                    125: }