1 /* mpz_divexact -- finds quotient when known that quot * den == num && den != 0.
3 Copyright (C) 1991, 1993, 1994, 1995 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 Library General Public License as published by
9 the Free Software Foundation; either version 2 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 Library General Public
15 License for more details.
17 You should have received a copy of the GNU Library 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. */
22 /* Ken Weber (kweber@mat.ufrgs.br, kweber@mcs.kent.edu)
24 Funding for this work has been partially provided by Conselho Nacional
25 de Desenvolvimento Cienti'fico e Tecnolo'gico (CNPq) do Brazil, Grant
26 301314194-2, and was done while I was a visiting reseacher in the Instituto
27 de Matema'tica at Universidade Federal do Rio Grande do Sul (UFRGS).
30 T. Jebelean, An algorithm for exact division, Journal of Symbolic
31 Computation, v. 15, 1993, pp. 169-180. */
39 mpz_divexact (mpz_ptr quot, mpz_srcptr num, mpz_srcptr den)
41 mpz_divexact (quot, num, den)
48 mp_size_t qsize, tsize;
50 mp_srcptr np = num->_mp_d;
51 mp_srcptr dp = den->_mp_d;
52 mp_size_t nsize = ABS (num->_mp_size);
53 mp_size_t dsize = ABS (den->_mp_size);
56 /* Generate divide-by-zero error if dsize == 0. */
59 quot->_mp_size = 1 / dsize;
69 qsize = nsize - dsize + 1;
70 if (quot->_mp_alloc < qsize)
71 _mpz_realloc (quot, qsize);
76 /* QUOT <-- NUM/2^r, T <-- DEN/2^r where = r number of twos in DEN. */
78 np += 1, nsize -= 1, dp += 1, dsize -= 1;
79 tsize = MIN (qsize, dsize);
83 MPN_COPY (qp, np, qsize);
84 if (qp == dp) /* QUOT and DEN overlap. */
86 tp = (mp_ptr) TMP_ALLOC (sizeof (mp_limb_t) * tsize);
87 MPN_COPY (tp, dp, tsize);
95 tp = (mp_ptr) TMP_ALLOC (sizeof (mp_limb_t) * tsize);
96 count_trailing_zeros (r, dp[0]);
97 mpn_rshift (tp, dp, tsize, r);
99 tp[tsize-1] |= dp[tsize] << (BITS_PER_MP_LIMB - r);
100 mpn_rshift (qp, np, qsize, r);
102 qp[qsize-1] |= np[qsize] << (BITS_PER_MP_LIMB - r);
105 /* Now QUOT <-- QUOT/T. */
106 mpn_bdivmod (qp, qp, qsize, tp, tsize, qsize * BITS_PER_MP_LIMB);
107 MPN_NORMALIZE (qp, qsize);
109 quot->_mp_size = (num->_mp_size < 0) == (den->_mp_size < 0) ? qsize : -qsize;