Annotation of OpenXM/src/kan96xx/gmp-2.0.2-ssh-2/mpz/divexact.c, Revision 1.1.1.1
1.1 takayama 1: /* mpz_divexact -- finds quotient when known that quot * den == num && den != 0.
2:
3: Copyright (C) 1991, 1993, 1994, 1995 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 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.
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 Library General Public
15: License for more details.
16:
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. */
21:
22: /* Ken Weber (kweber@mat.ufrgs.br, kweber@mcs.kent.edu)
23:
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).
28:
29: References:
30: T. Jebelean, An algorithm for exact division, Journal of Symbolic
31: Computation, v. 15, 1993, pp. 169-180. */
32:
33: #include "gmp.h"
34: #include "gmp-impl.h"
35: #include "longlong.h"
36:
37: void
38: #if __STDC__
39: mpz_divexact (mpz_ptr quot, mpz_srcptr num, mpz_srcptr den)
40: #else
41: mpz_divexact (quot, num, den)
42: mpz_ptr quot;
43: mpz_srcptr num;
44: mpz_srcptr den;
45: #endif
46: {
47: mp_ptr qp, tp;
48: mp_size_t qsize, tsize;
49:
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);
54: TMP_DECL (marker);
55:
56: /* Generate divide-by-zero error if dsize == 0. */
57: if (dsize == 0)
58: {
59: quot->_mp_size = 1 / dsize;
60: return;
61: }
62:
63: if (nsize == 0)
64: {
65: quot->_mp_size = 0;
66: return;
67: }
68:
69: qsize = nsize - dsize + 1;
70: if (quot->_mp_alloc < qsize)
71: _mpz_realloc (quot, qsize);
72: qp = quot->_mp_d;
73:
74: TMP_MARK (marker);
75:
76: /* QUOT <-- NUM/2^r, T <-- DEN/2^r where = r number of twos in DEN. */
77: while (dp[0] == 0)
78: np += 1, nsize -= 1, dp += 1, dsize -= 1;
79: tsize = MIN (qsize, dsize);
80: if (dp[0] & 1)
81: {
82: if (qp != dp)
83: MPN_COPY (qp, np, qsize);
84: if (qp == dp) /* QUOT and DEN overlap. */
85: {
86: tp = (mp_ptr) TMP_ALLOC (sizeof (mp_limb_t) * tsize);
87: MPN_COPY (tp, dp, tsize);
88: }
89: else
90: tp = (mp_ptr) dp;
91: }
92: else
93: {
94: unsigned long int r;
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);
98: if (dsize > tsize)
99: tp[tsize-1] |= dp[tsize] << (BITS_PER_MP_LIMB - r);
100: mpn_rshift (qp, np, qsize, r);
101: if (nsize > qsize)
102: qp[qsize-1] |= np[qsize] << (BITS_PER_MP_LIMB - r);
103: }
104:
105: /* Now QUOT <-- QUOT/T. */
106: mpn_bdivmod (qp, qp, qsize, tp, tsize, qsize * BITS_PER_MP_LIMB);
107: MPN_NORMALIZE (qp, qsize);
108:
109: quot->_mp_size = (num->_mp_size < 0) == (den->_mp_size < 0) ? qsize : -qsize;
110:
111: TMP_FREE (marker);
112: }
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