source/libs/gmp/gmp-src/mpq/div.c

   1 /* mpq_div -- divide two rational numbers.
   2
   3 Copyright 1991, 1994-1996, 2000, 2001, 2015 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 either:
   9
  10   * the GNU Lesser General Public License as published by the Free
  11     Software Foundation; either version 3 of the License, or (at your
  12     option) any later version.
  13
  14 or
  15
  16   * the GNU General Public License as published by the Free Software
  17     Foundation; either version 2 of the License, or (at your option) any
  18     later version.
  19
  20 or both in parallel, as here.
  21
  22 The GNU MP Library is distributed in the hope that it will be useful, but
  23 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  24 or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  25 for more details.
  26
  27 You should have received copies of the GNU General Public License and the
  28 GNU Lesser General Public License along with the GNU MP Library.  If not,
  29 see https://www.gnu.org/licenses/.  */
  30
  31 #include "gmp.h"
  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 (op1 == op2)
  53         {
  54           PTR(NUM(quot))[0] = 1;
  55           SIZ(NUM(quot)) = 1;
  56           PTR(DEN(quot))[0] = 1;
  57           SIZ(DEN(quot)) = 1;
  58           return;
  59         }
  60
  61       /* We checked for op1 == op2: we are not in the x=x/x case.
  62          We compute x=y/x by computing x=inv(x)*y */
  63       MPN_PTR_SWAP (PTR(NUM(quot)), ALLOC(NUM(quot)),
  64                     PTR(DEN(quot)), ALLOC(DEN(quot)));
  65       if (op2_size > 0)
  66         {
  67           SIZ(NUM(quot)) = SIZ(DEN(quot));
  68           SIZ(DEN(quot)) = op2_size;
  69         }
  70       else
  71         {
  72           SIZ(NUM(quot)) = - SIZ(DEN(quot));
  73           SIZ(DEN(quot)) = - op2_size;
  74         }
  75       mpq_mul (quot, quot, op1);
  76       return;
  77     }
  78
  79   op1_size = ABSIZ(NUM(op1));
  80
  81   if (op1_size == 0)
  82     {
  83       /* We special case this to simplify allocation logic; gcd(0,x) = x
  84          is a singular case for the allocations.  */
  85       SIZ(NUM(quot)) = 0;
  86       PTR(DEN(quot))[0] = 1;
  87       SIZ(DEN(quot)) = 1;
  88       return;
  89     }
  90
  91   op2_size = ABS(op2_size);
  92
  93   TMP_MARK;
  94
  95   alloc = MIN (op1_size, op2_size);
  96   MPZ_TMP_INIT (gcd1, alloc);
  97
  98   alloc = MAX (op1_size, op2_size);
  99   MPZ_TMP_INIT (tmp1, alloc);
 100
 101   op2_size = SIZ(DEN(op2));
 102   op1_size = SIZ(DEN(op1));
 103
 104   alloc = MIN (op1_size, op2_size);
 105   MPZ_TMP_INIT (gcd2, alloc);
 106
 107   alloc = MAX (op1_size, op2_size);
 108   MPZ_TMP_INIT (tmp2, alloc);
 109
 110   /* QUOT might be identical to OP1, so don't store the result there
 111      until we are finished with the input operand.  We can overwrite
 112      the numerator of QUOT when we are finished with the numerator of
 113      OP1. */
 114
 115   mpz_gcd (gcd1, NUM(op1), NUM(op2));
 116   mpz_gcd (gcd2, DEN(op2), DEN(op1));
 117
 118   mpz_divexact_gcd (tmp1, NUM(op1), gcd1);
 119   mpz_divexact_gcd (tmp2, DEN(op2), gcd2);
 120
 121   mpz_mul (NUM(quot), tmp1, tmp2);
 122
 123   mpz_divexact_gcd (tmp1, NUM(op2), gcd1);
 124   mpz_divexact_gcd (tmp2, DEN(op1), gcd2);
 125
 126   mpz_mul (DEN(quot), tmp1, tmp2);
 127
 128   /* Keep the denominator positive.  */
 129   if (SIZ(DEN(quot)) < 0)
 130     {
 131       SIZ(DEN(quot)) = -SIZ(DEN(quot));
 132       SIZ(NUM(quot)) = -SIZ(NUM(quot));
 133     }
 134
 135   TMP_FREE;
 136 }