1 /* mpq_div -- divide two rational numbers.
2
3 Copyright 1991, 1994-1996, 2000, 2001, 2015, 2018 Free Software
4 Foundation, Inc.
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
9 it under the terms of either:
10
11 * the GNU Lesser General Public License as published by the Free
12 Software Foundation; either version 3 of the License, or (at your
13 option) any later version.
14
15 or
16
17 * the GNU General Public License as published by the Free Software
18 Foundation; either version 2 of the License, or (at your option) any
19 later version.
20
21 or both in parallel, as here.
22
23 The GNU MP Library is distributed in the hope that it will be useful, but
24 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
25 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
26 for more details.
27
28 You should have received copies of the GNU General Public License and the
29 GNU Lesser General Public License along with the GNU MP Library. If not,
30 see https://www.gnu.org/licenses/. */
31
32 #include "gmp-impl.h"
33
34
35 void
mpq_div(mpq_ptr quot,mpq_srcptr op1,mpq_srcptr op2)36 mpq_div (mpq_ptr quot, mpq_srcptr op1, mpq_srcptr op2)
37 {
38 mpz_t gcd1, gcd2;
39 mpz_t tmp1, tmp2;
40 mp_size_t op1_size;
41 mp_size_t op2_size;
42 mp_size_t alloc;
43 TMP_DECL;
44
45 op2_size = SIZ(NUM(op2));
46
47 if (UNLIKELY (op2_size == 0))
48 DIVIDE_BY_ZERO;
49
50 if (UNLIKELY (quot == op2))
51 {
52 if (UNLIKELY (op1 == op2))
53 {
54 mpq_set_ui (quot, 1, 1);
55 return;
56 }
57
58 /* We checked for op1 == op2: we are not in the x=x/x case.
59 We compute x=y/x by computing x=inv(x)*y */
60 MPN_PTR_SWAP (PTR(NUM(quot)), ALLOC(NUM(quot)),
61 PTR(DEN(quot)), ALLOC(DEN(quot)));
62 if (op2_size > 0)
63 {
64 SIZ(NUM(quot)) = SIZ(DEN(quot));
65 SIZ(DEN(quot)) = op2_size;
66 }
67 else
68 {
69 SIZ(NUM(quot)) = - SIZ(DEN(quot));
70 SIZ(DEN(quot)) = - op2_size;
71 }
72 mpq_mul (quot, quot, op1);
73 return;
74 }
75
76 op1_size = ABSIZ(NUM(op1));
77
78 if (op1_size == 0)
79 {
80 /* We special case this to simplify allocation logic; gcd(0,x) = x
81 is a singular case for the allocations. */
82 SIZ(NUM(quot)) = 0;
83 MPZ_NEWALLOC (DEN(quot), 1)[0] = 1;
84 SIZ(DEN(quot)) = 1;
85 return;
86 }
87
88 op2_size = ABS(op2_size);
89
90 TMP_MARK;
91
92 alloc = MIN (op1_size, op2_size);
93 MPZ_TMP_INIT (gcd1, alloc);
94
95 alloc = MAX (op1_size, op2_size);
96 MPZ_TMP_INIT (tmp1, alloc);
97
98 op2_size = SIZ(DEN(op2));
99 op1_size = SIZ(DEN(op1));
100
101 alloc = MIN (op1_size, op2_size);
102 MPZ_TMP_INIT (gcd2, alloc);
103
104 alloc = MAX (op1_size, op2_size);
105 MPZ_TMP_INIT (tmp2, alloc);
106
107 /* QUOT might be identical to OP1, so don't store the result there
108 until we are finished with the input operand. We can overwrite
109 the numerator of QUOT when we are finished with the numerator of
110 OP1. */
111
112 mpz_gcd (gcd1, NUM(op1), NUM(op2));
113 mpz_gcd (gcd2, DEN(op2), DEN(op1));
114
115 mpz_divexact_gcd (tmp1, NUM(op1), gcd1);
116 mpz_divexact_gcd (tmp2, DEN(op2), gcd2);
117
118 mpz_mul (NUM(quot), tmp1, tmp2);
119
120 mpz_divexact_gcd (tmp1, NUM(op2), gcd1);
121 mpz_divexact_gcd (tmp2, DEN(op1), gcd2);
122
123 mpz_mul (DEN(quot), tmp1, tmp2);
124
125 /* Keep the denominator positive. */
126 if (SIZ(DEN(quot)) < 0)
127 {
128 SIZ(DEN(quot)) = -SIZ(DEN(quot));
129 SIZ(NUM(quot)) = -SIZ(NUM(quot));
130 }
131
132 TMP_FREE;
133 }
134