1  /* mpq_add, mpq_sub -- add or subtract rational numbers.
       2  
       3  Copyright 1991, 1994-1997, 2000, 2001, 2004, 2005 Free Software Foundation,
       4  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  static void __gmpq_aors (REGPARM_3_1 (mpq_ptr, mpq_srcptr, mpq_srcptr, void (*) (mpz_ptr, mpz_srcptr, mpz_srcptr))) REGPARM_ATTR (1);
      36  #define mpq_aors(w,x,y,fun)  __gmpq_aors (REGPARM_3_1 (w, x, y, fun))
      37  
      38  REGPARM_ATTR (1) static void
      39  mpq_aors (mpq_ptr rop, mpq_srcptr op1, mpq_srcptr op2,
      40            void (*fun) (mpz_ptr, mpz_srcptr, mpz_srcptr))
      41  {
      42    mpz_t gcd;
      43    mpz_t tmp1, tmp2;
      44    mp_size_t op1_num_size = ABSIZ(NUM(op1));
      45    mp_size_t op1_den_size =   SIZ(DEN(op1));
      46    mp_size_t op2_num_size = ABSIZ(NUM(op2));
      47    mp_size_t op2_den_size =   SIZ(DEN(op2));
      48    TMP_DECL;
      49  
      50    TMP_MARK;
      51    MPZ_TMP_INIT (gcd, MIN (op1_den_size, op2_den_size));
      52    MPZ_TMP_INIT (tmp1, op1_num_size + op2_den_size);
      53    MPZ_TMP_INIT (tmp2, op2_num_size + op1_den_size);
      54  
      55    /* ROP might be identical to either operand, so don't store the
      56       result there until we are finished with the input operands.  We
      57       dare to overwrite the numerator of ROP when we are finished
      58       with the numerators of OP1 and OP2.  */
      59  
      60    mpz_gcd (gcd, DEN(op1), DEN(op2));
      61    if (! MPZ_EQUAL_1_P (gcd))
      62      {
      63        mpz_t t;
      64  
      65        MPZ_TMP_INIT (t, MAX (op1_num_size + op2_den_size,
      66  	     op2_num_size + op1_den_size) + 2 - SIZ(gcd));
      67  
      68        mpz_divexact_gcd (t, DEN(op2), gcd);
      69        mpz_divexact_gcd (tmp2, DEN(op1), gcd);
      70  
      71        mpz_mul (tmp1, NUM(op1), t);
      72        mpz_mul (t, NUM(op2), tmp2);
      73  
      74        (*fun) (t, tmp1, t);
      75  
      76        mpz_gcd (gcd, t, gcd);
      77        if (MPZ_EQUAL_1_P (gcd))
      78          {
      79            mpz_set (NUM(rop), t);
      80            mpz_mul (DEN(rop), DEN(op2), tmp2);
      81          }
      82        else
      83          {
      84            mpz_divexact_gcd (NUM(rop), t, gcd);
      85            mpz_divexact_gcd (tmp1, DEN(op2), gcd);
      86            mpz_mul (DEN(rop), tmp1, tmp2);
      87          }
      88      }
      89    else
      90      {
      91        /* The common divisor is 1.  This is the case (for random input) with
      92  	 probability 6/(pi**2), which is about 60.8%.  */
      93        mpz_mul (tmp1, NUM(op1), DEN(op2));
      94        mpz_mul (tmp2, NUM(op2), DEN(op1));
      95        (*fun) (NUM(rop), tmp1, tmp2);
      96        mpz_mul (DEN(rop), DEN(op1), DEN(op2));
      97      }
      98    TMP_FREE;
      99  }
     100  
     101  
     102  void
     103  mpq_add (mpq_ptr rop, mpq_srcptr op1, mpq_srcptr op2)
     104  {
     105    mpq_aors (rop, op1, op2, mpz_add);
     106  }
     107  
     108  void
     109  mpq_sub (mpq_ptr rop, mpq_srcptr op1, mpq_srcptr op2)
     110  {
     111    mpq_aors (rop, op1, op2, mpz_sub);
     112  }