1  /* mpz_divexact -- finds quotient when known that quot * den == num && den != 0.
       2  
       3  Contributed to the GNU project by Niels Möller.
       4  
       5  Copyright 1991, 1993-1998, 2000-2002, 2005-2007, 2009, 2012 Free Software
       6  Foundation, Inc.
       7  
       8  This file is part of the GNU MP Library.
       9  
      10  The GNU MP Library is free software; you can redistribute it and/or modify
      11  it under the terms of either:
      12  
      13    * the GNU Lesser General Public License as published by the Free
      14      Software Foundation; either version 3 of the License, or (at your
      15      option) any later version.
      16  
      17  or
      18  
      19    * the GNU General Public License as published by the Free Software
      20      Foundation; either version 2 of the License, or (at your option) any
      21      later version.
      22  
      23  or both in parallel, as here.
      24  
      25  The GNU MP Library is distributed in the hope that it will be useful, but
      26  WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
      27  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
      28  for more details.
      29  
      30  You should have received copies of the GNU General Public License and the
      31  GNU Lesser General Public License along with the GNU MP Library.  If not,
      32  see https://www.gnu.org/licenses/.  */
      33  
      34  
      35  #include "gmp-impl.h"
      36  
      37  void
      38  mpz_divexact (mpz_ptr quot, mpz_srcptr num, mpz_srcptr den)
      39  {
      40    mp_ptr qp;
      41    mp_size_t qn;
      42    mp_srcptr np, dp;
      43    mp_size_t nn, dn;
      44    TMP_DECL;
      45  
      46  #if WANT_ASSERT
      47    {
      48      mpz_t  rem;
      49      mpz_init (rem);
      50      mpz_tdiv_r (rem, num, den);
      51      ASSERT (SIZ(rem) == 0);
      52      mpz_clear (rem);
      53    }
      54  #endif
      55  
      56    nn = ABSIZ (num);
      57    dn = ABSIZ (den);
      58  
      59    if (nn < dn)
      60      {
      61        /* This special case avoids segfaults below when the function is
      62  	 incorrectly called with |N| < |D|, N != 0.  It also handles the
      63  	 well-defined case N = 0.  */
      64        SIZ(quot) = 0;
      65        return;
      66      }
      67  
      68    qn = nn - dn + 1;
      69  
      70    TMP_MARK;
      71  
      72    if (quot == num || quot == den)
      73      qp = TMP_ALLOC_LIMBS (qn);
      74    else
      75      qp = MPZ_NEWALLOC (quot, qn);
      76  
      77    np = PTR(num);
      78    dp = PTR(den);
      79  
      80    mpn_divexact (qp, np, nn, dp, dn);
      81    MPN_NORMALIZE (qp, qn);
      82  
      83    if (qp != PTR(quot))
      84      MPN_COPY (MPZ_NEWALLOC (quot, qn), qp, qn);
      85  
      86    SIZ(quot) = (SIZ(num) ^ SIZ(den)) >= 0 ? qn : -qn;
      87  
      88    TMP_FREE;
      89  }