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 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