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tdiv_qr_ui.c revision 1.1.1.1.8.1 
      1 /* mpz_tdiv_qr_ui(quot,rem,dividend,short_divisor) --
      2    Set QUOT to DIVIDEND / SHORT_DIVISOR
      3    and REM to DIVIDEND mod SHORT_DIVISOR.
      4 
      5 Copyright 1991, 1993, 1994, 1996, 1998, 2001, 2002, 2004, 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 the GNU Lesser General Public License as published by
     12 the Free Software Foundation; either version 3 of the License, or (at your
     13 option) any later version.
     14 
     15 The GNU MP Library is distributed in the hope that it will be useful, but
     16 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
     17 or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
     18 License for more details.
     19 
     20 You should have received a copy of the GNU Lesser General Public License
     21 along with the GNU MP Library.  If not, see http://www.gnu.org/licenses/.  */
     22 
     23 #include "gmp.h"
     24 #include "gmp-impl.h"
     25 
     26 unsigned long int
     27 mpz_tdiv_qr_ui (mpz_ptr quot, mpz_ptr rem, mpz_srcptr dividend, unsigned long int divisor)
     28 {
     29   mp_size_t ns, nn, qn;
     30   mp_ptr np, qp;
     31   mp_limb_t rl;
     32 
     33   if (UNLIKELY (divisor == 0))
     34     DIVIDE_BY_ZERO;
     35 
     36   ns = SIZ(dividend);
     37   if (ns == 0)
     38     {
     39       SIZ(quot) = 0;
     40       SIZ(rem) = 0;
     41       return 0;
     42     }
     43 
     44   nn = ABS(ns);
     45   qp = MPZ_REALLOC (quot, nn);
     46   np = PTR(dividend);
     47 
     48 #if BITS_PER_ULONG > GMP_NUMB_BITS  /* avoid warnings about shift amount */
     49   if (divisor > GMP_NUMB_MAX)
     50     {
     51       mp_limb_t dp[2];
     52       mp_ptr rp;
     53       mp_size_t rn;
     54 
     55       if (nn == 1)		/* tdiv_qr requirements; tested above for 0 */
     56 	{
     57 	  SIZ(quot) = 0;
     58 	  rl = np[0];
     59 	  SIZ(rem) = ns >= 0 ? 1 : -1;
     60 	  PTR(rem)[0] = rl;
     61 	  return rl;
     62 	}
     63 
     64       rp = MPZ_REALLOC (rem, 2);
     65 
     66       dp[0] = divisor & GMP_NUMB_MASK;
     67       dp[1] = divisor >> GMP_NUMB_BITS;
     68       mpn_tdiv_qr (qp, rp, (mp_size_t) 0, np, nn, dp, (mp_size_t) 2);
     69       rl = rp[0] + (rp[1] << GMP_NUMB_BITS);
     70       qn = nn - 2 + 1; qn -= qp[qn - 1] == 0; qn -= qn != 0 && qp[qn - 1] == 0;
     71       rn = 2 - (rp[1] == 0);  rn -= (rp[rn - 1] == 0);
     72       SIZ(rem) = ns >= 0 ? rn : -rn;
     73     }
     74   else
     75 #endif
     76     {
     77       rl = mpn_divrem_1 (qp, (mp_size_t) 0, np, nn, (mp_limb_t) divisor);
     78       if (rl == 0)
     79 	SIZ(rem) = 0;
     80       else
     81 	{
     82 	  /* Store the single-limb remainder.  We don't check if there's space
     83 	     for just one limb, since no function ever makes zero space.  */
     84 	  SIZ(rem) = ns >= 0 ? 1 : -1;
     85 	  PTR(rem)[0] = rl;
     86 	}
     87       qn = nn - (qp[nn - 1] == 0);
     88     }
     89 
     90   SIZ(quot) = ns >= 0 ? qn : -qn;
     91   return rl;
     92 }
     93