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

   1 /* mpz_cdiv_ui -- Division rounding the quotient towards +infinity.  The
   2    remainder gets the opposite sign as the denominator.  In order to make it
   3    always fit into the return type, the negative of the true remainder is
   4    returned.
   5
   6 Copyright 1994-1996, 2001, 2002, 2004, 2005, 2012 Free Software Foundation,
   7 Inc.
   8
   9 This file is part of the GNU MP Library.
  10
  11 The GNU MP Library is free software; you can redistribute it and/or modify
  12 it under the terms of either:
  13
  14   * the GNU Lesser General Public License as published by the Free
  15     Software Foundation; either version 3 of the License, or (at your
  16     option) any later version.
  17
  18 or
  19
  20   * the GNU General Public License as published by the Free Software
  21     Foundation; either version 2 of the License, or (at your option) any
  22     later version.
  23
  24 or both in parallel, as here.
  25
  26 The GNU MP Library is distributed in the hope that it will be useful, but
  27 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  28 or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  29 for more details.
  30
  31 You should have received copies of the GNU General Public License and the
  32 GNU Lesser General Public License along with the GNU MP Library.  If not,
  33 see https://www.gnu.org/licenses/.  */
  34
  35 #include "gmp.h"
  36 #include "gmp-impl.h"
  37
  38 unsigned long int
  39 mpz_cdiv_ui (mpz_srcptr dividend, unsigned long int divisor)
  40 {
  41   mp_size_t ns, nn;
  42   mp_ptr np;
  43   mp_limb_t rl;
  44
  45   if (UNLIKELY (divisor == 0))
  46     DIVIDE_BY_ZERO;
  47
  48   ns = SIZ(dividend);
  49   if (ns == 0)
  50     {
  51       return 0;
  52     }
  53
  54   nn = ABS(ns);
  55   np = PTR(dividend);
  56 #if BITS_PER_ULONG > GMP_NUMB_BITS  /* avoid warnings about shift amount */
  57   if (divisor > GMP_NUMB_MAX)
  58     {
  59       mp_limb_t dp[2], rp[2];
  60       mp_ptr qp;
  61       mp_size_t rn;
  62       TMP_DECL;
  63
  64       if (nn == 1)              /* tdiv_qr requirements; tested above for 0 */
  65         {
  66           rl = np[0];
  67           rp[0] = rl;
  68         }
  69       else
  70         {
  71           TMP_MARK;
  72           dp[0] = divisor & GMP_NUMB_MASK;
  73           dp[1] = divisor >> GMP_NUMB_BITS;
  74           qp = TMP_ALLOC_LIMBS (nn - 2 + 1);
  75           mpn_tdiv_qr (qp, rp, (mp_size_t) 0, np, nn, dp, (mp_size_t) 2);
  76           TMP_FREE;
  77           rl = rp[0] + (rp[1] << GMP_NUMB_BITS);
  78         }
  79
  80       if (rl != 0 && ns >= 0)
  81         {
  82           rl = divisor - rl;
  83           rp[0] = rl & GMP_NUMB_MASK;
  84           rp[1] = rl >> GMP_NUMB_BITS;
  85         }
  86
  87       rn = 1 + (rl > GMP_NUMB_MAX);  rn -= (rp[rn - 1] == 0);
  88     }
  89   else
  90 #endif
  91     {
  92       rl = mpn_mod_1 (np, nn, (mp_limb_t) divisor);
  93       if (rl == 0)
  94         ;
  95       else
  96         {
  97           if (ns >= 0)
  98             rl = divisor - rl;
  99         }
 100     }
 101
 102   return rl;
 103 }