1 /* mpz_fdiv_qr_ui -- Division rounding the quotient towards -infinity.
2 The remainder gets the same sign as the denominator.
3
4 Copyright 1994-1996, 1999, 2001, 2002, 2004, 2012, 2015 Free Software
5 Foundation, Inc.
6
7 This file is part of the GNU MP Library.
8
9 The GNU MP Library is free software; you can redistribute it and/or modify
10 it under the terms of either:
11
12 * the GNU Lesser General Public License as published by the Free
13 Software Foundation; either version 3 of the License, or (at your
14 option) any later version.
15
16 or
17
18 * the GNU General Public License as published by the Free Software
19 Foundation; either version 2 of the License, or (at your option) any
20 later version.
21
22 or both in parallel, as here.
23
24 The GNU MP Library is distributed in the hope that it will be useful, but
25 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
26 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
27 for more details.
28
29 You should have received copies of the GNU General Public License and the
30 GNU Lesser General Public License along with the GNU MP Library. If not,
31 see https://www.gnu.org/licenses/. */
32
33 #include "gmp-impl.h"
34
35 unsigned long int
mpz_fdiv_qr_ui(mpz_ptr quot,mpz_ptr rem,mpz_srcptr dividend,unsigned long int divisor)36 mpz_fdiv_qr_ui (mpz_ptr quot, mpz_ptr rem, mpz_srcptr dividend, unsigned long int divisor)
37 {
38 mp_size_t ns, nn, qn;
39 mp_ptr np, qp;
40 mp_limb_t rl;
41
42 if (UNLIKELY (divisor == 0))
43 DIVIDE_BY_ZERO;
44
45 ns = SIZ(dividend);
46 if (ns == 0)
47 {
48 SIZ(quot) = 0;
49 SIZ(rem) = 0;
50 return 0;
51 }
52
53 nn = ABS(ns);
54 qp = MPZ_REALLOC (quot, nn);
55 np = PTR(dividend);
56
57 #if BITS_PER_ULONG > GMP_NUMB_BITS /* avoid warnings about shift amount */
58 if (divisor > GMP_NUMB_MAX)
59 {
60 mp_limb_t dp[2];
61 mp_ptr rp;
62 mp_size_t rn;
63
64 rp = MPZ_REALLOC (rem, 2);
65
66 if (nn == 1) /* tdiv_qr requirements; tested above for 0 */
67 {
68 qp[0] = 0;
69 qn = 1; /* a white lie, fixed below */
70 rl = np[0];
71 rp[0] = rl;
72 }
73 else
74 {
75 dp[0] = divisor & GMP_NUMB_MASK;
76 dp[1] = divisor >> GMP_NUMB_BITS;
77 mpn_tdiv_qr (qp, rp, (mp_size_t) 0, np, nn, dp, (mp_size_t) 2);
78 rl = rp[0] + (rp[1] << GMP_NUMB_BITS);
79 qn = nn - 2 + 1;
80 }
81
82 if (rl != 0 && ns < 0)
83 {
84 mpn_incr_u (qp, (mp_limb_t) 1);
85 rl = divisor - rl;
86 rp[0] = rl & GMP_NUMB_MASK;
87 rp[1] = rl >> GMP_NUMB_BITS;
88 }
89
90 qn -= qp[qn - 1] == 0; qn -= qn != 0 && qp[qn - 1] == 0;
91 rn = 1 + (rl > GMP_NUMB_MAX); rn -= (rp[rn - 1] == 0);
92 SIZ(rem) = rn;
93 }
94 else
95 #endif
96 {
97 rl = mpn_divrem_1 (qp, (mp_size_t) 0, np, nn, (mp_limb_t) divisor);
98 if (rl == 0)
99 SIZ(rem) = 0;
100 else
101 {
102 if (ns < 0)
103 {
104 mpn_incr_u (qp, (mp_limb_t) 1);
105 rl = divisor - rl;
106 }
107
108 MPZ_NEWALLOC (rem, 1)[0] = rl;
109 SIZ(rem) = rl != 0;
110 }
111 qn = nn - (qp[nn - 1] == 0);
112 }
113
114 SIZ(quot) = ns >= 0 ? qn : -qn;
115 return rl;
116 }
117