contrib/gmp/mpz/cdiv_qr_ui.c

   1 /* mpz_cdiv_qr_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, 1995, 1996, 1999, 2001, 2002, 2004 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 the GNU Lesser General Public License as published by
  13 the Free Software Foundation; either version 3 of the License, or (at your
  14 option) any later version.
  15
  16 The GNU MP Library is distributed in the hope that it will be useful, but
  17 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  18 or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
  19 License for more details.
  20
  21 You should have received a copy of the GNU Lesser General Public License
  22 along with the GNU MP Library.  If not, see http://www.gnu.org/licenses/.  */
  23
  24 #include "gmp.h"
  25 #include "gmp-impl.h"
  26
  27 unsigned long int
  28 mpz_cdiv_qr_ui (mpz_ptr quot, mpz_ptr rem, mpz_srcptr dividend, unsigned long int divisor)
  29 {
  30   mp_size_t ns, nn, qn;
  31   mp_ptr np, qp;
  32   mp_limb_t rl;
  33
  34   if (divisor == 0)
  35     DIVIDE_BY_ZERO;
  36
  37   ns = SIZ(dividend);
  38   if (ns == 0)
  39     {
  40       SIZ(quot) = 0;
  41       SIZ(rem) = 0;
  42       return 0;
  43     }
  44
  45   nn = ABS(ns);
  46   MPZ_REALLOC (quot, nn);
  47   qp = PTR(quot);
  48   np = PTR(dividend);
  49
  50 #if BITS_PER_ULONG > GMP_NUMB_BITS  /* avoid warnings about shift amount */
  51   if (divisor > GMP_NUMB_MAX)
  52     {
  53       mp_limb_t dp[2];
  54       mp_ptr rp;
  55       mp_size_t rn;
  56
  57       MPZ_REALLOC (rem, 2);
  58       rp = PTR(rem);
  59
  60       if (nn == 1)              /* tdiv_qr requirements; tested above for 0 */
  61         {
  62           qp[0] = 0;
  63           qn = 1;               /* a white lie, fixed below */
  64           rl = np[0];
  65           rp[0] = rl;
  66         }
  67       else
  68         {
  69           dp[0] = divisor & GMP_NUMB_MASK;
  70           dp[1] = divisor >> GMP_NUMB_BITS;
  71           mpn_tdiv_qr (qp, rp, (mp_size_t) 0, np, nn, dp, (mp_size_t) 2);
  72           rl = rp[0] + (rp[1] << GMP_NUMB_BITS);
  73           qn = nn - 2 + 1;
  74         }
  75
  76       if (rl != 0 && ns >= 0)
  77         {
  78           mpn_incr_u (qp, (mp_limb_t) 1);
  79           rl = divisor - rl;
  80           rp[0] = rl & GMP_NUMB_MASK;
  81           rp[1] = rl >> GMP_NUMB_BITS;
  82         }
  83
  84       qn -= qp[qn - 1] == 0; qn -= qn != 0 && qp[qn - 1] == 0;
  85       rn = 1 + (rl > GMP_NUMB_MAX);  rn -= (rp[rn - 1] == 0);
  86       SIZ(rem) = -rn;
  87     }
  88   else
  89 #endif
  90     {
  91       rl = mpn_divrem_1 (qp, (mp_size_t) 0, np, nn, (mp_limb_t) divisor);
  92       if (rl == 0)
  93         SIZ(rem) = 0;
  94       else
  95         {
  96           if (ns >= 0)
  97             {
  98               mpn_incr_u (qp, (mp_limb_t) 1);
  99               rl = divisor - rl;
 100             }
 101
 102           PTR(rem)[0] = rl;
 103           SIZ(rem) = -(rl != 0);
 104         }
 105       qn = nn - (qp[nn - 1] == 0);
 106     }
 107
 108   SIZ(quot) = ns >= 0 ? qn : -qn;
 109   return rl;
 110 }