xref: /src/external/lgpl3/gmp/dist/mpz/tdiv_qr_ui.c

/* mpz_tdiv_qr_ui(quot,rem,dividend,short_divisor) --
   Set QUOT to DIVIDEND / SHORT_DIVISOR
   and REM to DIVIDEND mod SHORT_DIVISOR.

Copyright 1991, 1993, 1994, 1996, 1998, 2001, 2002, 2004, 2012 Free Software
Foundation, Inc.

This file is part of the GNU MP Library.

The GNU MP Library is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 3 of the License, or (at your
option) any later version.

The GNU MP Library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
License for more details.

You should have received a copy of the GNU Lesser General Public License
along with the GNU MP Library.  If not, see http://www.gnu.org/licenses/.  */

#include "gmp.h"
#include "gmp-impl.h"

unsigned long int
mpz_tdiv_qr_ui (mpz_ptr quot, mpz_ptr rem, mpz_srcptr dividend, unsigned long int divisor)
{
  mp_size_t ns, nn, qn;
  mp_ptr np, qp;
  mp_limb_t rl;

  if (UNLIKELY (divisor == 0))
    DIVIDE_BY_ZERO;

  ns = SIZ(dividend);
  if (ns == 0)
    {
      SIZ(quot) = 0;
      SIZ(rem) = 0;
      return 0;
    }

  nn = ABS(ns);
  qp = MPZ_REALLOC (quot, nn);
  np = PTR(dividend);

#if BITS_PER_ULONG > GMP_NUMB_BITS  /* avoid warnings about shift amount */
  if (divisor > GMP_NUMB_MAX)
    {
      mp_limb_t dp[2];
      mp_ptr rp;
      mp_size_t rn;

      if (nn == 1)		/* tdiv_qr requirements; tested above for 0 */
	{
	  SIZ(quot) = 0;
	  rl = np[0];
	  SIZ(rem) = ns >= 0 ? 1 : -1;
	  PTR(rem)[0] = rl;
	  return rl;
	}

      rp = MPZ_REALLOC (rem, 2);

      dp[0] = divisor & GMP_NUMB_MASK;
      dp[1] = divisor >> GMP_NUMB_BITS;
      mpn_tdiv_qr (qp, rp, (mp_size_t) 0, np, nn, dp, (mp_size_t) 2);
      rl = rp[0] + (rp[1] << GMP_NUMB_BITS);
      qn = nn - 2 + 1; qn -= qp[qn - 1] == 0; qn -= qn != 0 && qp[qn - 1] == 0;
      rn = 2 - (rp[1] == 0);  rn -= (rp[rn - 1] == 0);
      SIZ(rem) = ns >= 0 ? rn : -rn;
    }
  else
#endif
    {
      rl = mpn_divrem_1 (qp, (mp_size_t) 0, np, nn, (mp_limb_t) divisor);
      if (rl == 0)
	SIZ(rem) = 0;
      else
	{
	  /* Store the single-limb remainder.  We don't check if there's space
	     for just one limb, since no function ever makes zero space.  */
	  SIZ(rem) = ns >= 0 ? 1 : -1;
	  PTR(rem)[0] = rl;
	}
      qn = nn - (qp[nn - 1] == 0);
    }

  SIZ(quot) = ns >= 0 ? qn : -qn;
  return rl;
}