1/* mpz_divexact -- finds quotient when known that quot * den == num && den != 0.
2
3Contributed to the GNU project by Niels M��ller.
4
5Copyright 1991, 1993-1998, 2000-2002, 2005-2007, 2009, 2012 Free Software
6Foundation, Inc.
7
8This file is part of the GNU MP Library.
9
10The GNU MP Library is free software; you can redistribute it and/or modify
11it under the terms of either:
12
13  * the GNU Lesser General Public License as published by the Free
14    Software Foundation; either version 3 of the License, or (at your
15    option) any later version.
16
17or
18
19  * the GNU General Public License as published by the Free Software
20    Foundation; either version 2 of the License, or (at your option) any
21    later version.
22
23or both in parallel, as here.
24
25The GNU MP Library is distributed in the hope that it will be useful, but
26WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
27or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
28for more details.
29
30You should have received copies of the GNU General Public License and the
31GNU Lesser General Public License along with the GNU MP Library.  If not,
32see https://www.gnu.org/licenses/.  */
33
34
35#include "gmp-impl.h"
36
37void
38mpz_divexact (mpz_ptr quot, mpz_srcptr num, mpz_srcptr den)
39{
40  mp_ptr qp;
41  mp_size_t qn;
42  mp_srcptr np, dp;
43  mp_size_t nn, dn;
44  TMP_DECL;
45
46#if WANT_ASSERT
47  {
48    mpz_t  rem;
49    mpz_init (rem);
50    mpz_tdiv_r (rem, num, den);
51    ASSERT (SIZ(rem) == 0);
52    mpz_clear (rem);
53  }
54#endif
55
56  nn = ABSIZ (num);
57  dn = ABSIZ (den);
58
59  if (nn < dn)
60    {
61      /* This special case avoids segfaults below when the function is
62	 incorrectly called with |N| < |D|, N != 0.  It also handles the
63	 well-defined case N = 0.  */
64      SIZ(quot) = 0;
65      return;
66    }
67
68  qn = nn - dn + 1;
69
70  TMP_MARK;
71
72  if (quot == num || quot == den)
73    qp = TMP_ALLOC_LIMBS (qn);
74  else
75    qp = MPZ_NEWALLOC (quot, qn);
76
77  np = PTR(num);
78  dp = PTR(den);
79
80  mpn_divexact (qp, np, nn, dp, dn);
81  MPN_NORMALIZE (qp, qn);
82
83  if (qp != PTR(quot))
84    MPN_COPY (MPZ_NEWALLOC (quot, qn), qp, qn);
85
86  SIZ(quot) = (SIZ(num) ^ SIZ(den)) >= 0 ? qn : -qn;
87
88  TMP_FREE;
89}
90