contrib/gmp/mpz/tdiv_r_ui.c

   1 /* mpz_tdiv_r_ui(rem, dividend, divisor_limb)
   2    -- Set REM to DIVDEND mod DIVISOR_LIMB.
   3
   4 Copyright 1991, 1993, 1994, 1996, 1998, 2001, 2002, 2004, 2005 Free Software
   5 Foundation, Inc.
   6
   7 This file is part of the GNU MP Library.
   8
   9 The GNU MP Library is free software; you can redistribute it and/or modify
  10 it under the terms of the GNU Lesser General Public License as published by
  11 the Free Software Foundation; either version 3 of the License, or (at your
  12 option) any later version.
  13
  14 The GNU MP Library is distributed in the hope that it will be useful, but
  15 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  16 or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
  17 License for more details.
  18
  19 You should have received a copy of the GNU Lesser General Public License
  20 along with the GNU MP Library.  If not, see http://www.gnu.org/licenses/.  */
  21
  22 #include "gmp.h"
  23 #include "gmp-impl.h"
  24
  25 unsigned long int
  26 mpz_tdiv_r_ui (mpz_ptr rem, mpz_srcptr dividend, unsigned long int divisor)
  27 {
  28   mp_size_t ns, nn;
  29   mp_ptr np;
  30   mp_limb_t rl;
  31
  32   if (divisor == 0)
  33     DIVIDE_BY_ZERO;
  34
  35   ns = SIZ(dividend);
  36   if (ns == 0)
  37     {
  38       SIZ(rem) = 0;
  39       return 0;
  40     }
  41
  42   nn = ABS(ns);
  43   np = PTR(dividend);
  44 #if BITS_PER_ULONG > GMP_NUMB_BITS  /* avoid warnings about shift amount */
  45   if (divisor > GMP_NUMB_MAX)
  46     {
  47       mp_limb_t dp[2];
  48       mp_ptr rp, qp;
  49       mp_size_t rn;
  50       TMP_DECL;
  51
  52       if (nn == 1)              /* tdiv_qr requirements; tested above for 0 */
  53         {
  54           rl = np[0];
  55           SIZ(rem) = ns >= 0 ? 1 : -1;
  56           PTR(rem)[0] = rl;
  57           return rl;
  58         }
  59
  60       MPZ_REALLOC (rem, 2);
  61       rp = PTR(rem);
  62
  63       TMP_MARK;
  64       dp[0] = divisor & GMP_NUMB_MASK;
  65       dp[1] = divisor >> GMP_NUMB_BITS;
  66       qp = TMP_ALLOC_LIMBS (nn - 2 + 1);
  67       mpn_tdiv_qr (qp, rp, (mp_size_t) 0, np, nn, dp, (mp_size_t) 2);
  68       TMP_FREE;
  69       rl = rp[0] + (rp[1] << GMP_NUMB_BITS);
  70       rn = 2 - (rp[1] == 0);  rn -= (rp[rn - 1] == 0);
  71       SIZ(rem) = ns >= 0 ? rn : -rn;
  72     }
  73   else
  74 #endif
  75     {
  76       rl = mpn_mod_1 (np, nn, (mp_limb_t) divisor);
  77       if (rl == 0)
  78         SIZ(rem) = 0;
  79       else
  80         {
  81           /* Store the single-limb remainder.  We don't check if there's space
  82              for just one limb, since no function ever makes zero space.  */
  83           SIZ(rem) = ns >= 0 ? 1 : -1;
  84           PTR(rem)[0] = rl;
  85         }
  86     }
  87
  88   return rl;
  89 }