1  /* mpq_mul -- multiply two rational numbers.
       2  
       3  Copyright 1991, 1994-1996, 2000-2002 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-impl.h"
      32  
      33  
      34  void
      35  mpq_mul (mpq_ptr prod, mpq_srcptr op1, mpq_srcptr op2)
      36  {
      37    mpz_t gcd1, gcd2;
      38    mpz_t tmp1, tmp2;
      39    mp_size_t op1_num_size;
      40    mp_size_t op1_den_size;
      41    mp_size_t op2_num_size;
      42    mp_size_t op2_den_size;
      43    mp_size_t alloc;
      44    TMP_DECL;
      45  
      46    if (op1 == op2)
      47      {
      48        /* No need for any GCDs when squaring. */
      49        mpz_mul (mpq_numref (prod), mpq_numref (op1), mpq_numref (op1));
      50        mpz_mul (mpq_denref (prod), mpq_denref (op1), mpq_denref (op1));
      51        return;
      52      }
      53  
      54    op1_num_size = ABSIZ(NUM(op1));
      55    op1_den_size =   SIZ(DEN(op1));
      56    op2_num_size = ABSIZ(NUM(op2));
      57    op2_den_size =   SIZ(DEN(op2));
      58  
      59    if (op1_num_size == 0 || op2_num_size == 0)
      60      {
      61        /* We special case this to simplify allocation logic; gcd(0,x) = x
      62  	 is a singular case for the allocations.  */
      63        SIZ(NUM(prod)) = 0;
      64        MPZ_NEWALLOC (DEN(prod), 1)[0] = 1;
      65        SIZ(DEN(prod)) = 1;
      66        return;
      67      }
      68  
      69    TMP_MARK;
      70  
      71    alloc = MIN (op1_num_size, op2_den_size);
      72    MPZ_TMP_INIT (gcd1, alloc);
      73  
      74    alloc = MIN (op2_num_size, op1_den_size);
      75    MPZ_TMP_INIT (gcd2, alloc);
      76  
      77    alloc = MAX (op1_num_size, op2_den_size);
      78    MPZ_TMP_INIT (tmp1, alloc);
      79  
      80    alloc = MAX (op2_num_size, op1_den_size);
      81    MPZ_TMP_INIT (tmp2, alloc);
      82  
      83    /* PROD might be identical to either operand, so don't store the result there
      84       until we are finished with the input operands.  We can overwrite the
      85       numerator of PROD when we are finished with the numerators of OP1 and
      86       OP2.  */
      87  
      88    mpz_gcd (gcd1, NUM(op1), DEN(op2));
      89    mpz_gcd (gcd2, NUM(op2), DEN(op1));
      90  
      91    mpz_divexact_gcd (tmp1, NUM(op1), gcd1);
      92    mpz_divexact_gcd (tmp2, NUM(op2), gcd2);
      93  
      94    mpz_mul (NUM(prod), tmp1, tmp2);
      95  
      96    mpz_divexact_gcd (tmp1, DEN(op2), gcd1);
      97    mpz_divexact_gcd (tmp2, DEN(op1), gcd2);
      98  
      99    mpz_mul (DEN(prod), tmp1, tmp2);
     100  
     101    TMP_FREE;
     102  }