source/libs/gmp/gmp-src/mpz/divexact.c

   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.h"
  36 #include "gmp-impl.h"
  37 #include "longlong.h"
  38
  39 void
  40 mpz_divexact (mpz_ptr quot, mpz_srcptr num, mpz_srcptr den)
  41 {
  42   mp_ptr qp;
  43   mp_size_t qn;
  44   mp_srcptr np, dp;
  45   mp_size_t nn, dn;
  46   TMP_DECL;
  47
  48 #if WANT_ASSERT
  49   {
  50     mpz_t  rem;
  51     mpz_init (rem);
  52     mpz_tdiv_r (rem, num, den);
  53     ASSERT (SIZ(rem) == 0);
  54     mpz_clear (rem);
  55   }
  56 #endif
  57
  58   nn = ABSIZ (num);
  59   dn = ABSIZ (den);
  60
  61   if (nn < dn)
  62     {
  63       /* This special case avoids segfaults below when the function is
  64          incorrectly called with |N| < |D|, N != 0.  It also handles the
  65          well-defined case N = 0.  */
  66       SIZ(quot) = 0;
  67       return;
  68     }
  69
  70   qn = nn - dn + 1;
  71
  72   TMP_MARK;
  73
  74   if (quot == num || quot == den)
  75     qp = TMP_ALLOC_LIMBS (qn);
  76   else
  77     qp = MPZ_REALLOC (quot, qn);
  78
  79   np = PTR(num);
  80   dp = PTR(den);
  81
  82   mpn_divexact (qp, np, nn, dp, dn);
  83   MPN_NORMALIZE (qp, qn);
  84
  85   if (qp != PTR(quot))
  86     MPN_COPY (MPZ_REALLOC (quot, qn), qp, qn);
  87
  88   SIZ(quot) = (SIZ(num) ^ SIZ(den)) >= 0 ? qn : -qn;
  89
  90   TMP_FREE;
  91 }