xref: /dflybsd-src/contrib/gmp/mpz/tdiv_r_2exp.c (revision 86d7f5d305c6adaa56ff4582ece9859d73106103)

/* mpz_tdiv_r_2exp -- Divide a integer by 2**CNT and produce a remainder.

Copyright 1991, 1993, 1994, 1995, 2001, 2002 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"

void
mpz_tdiv_r_2exp (mpz_ptr res, mpz_srcptr in, mp_bitcnt_t cnt)
{
  mp_size_t in_size = ABS (in->_mp_size);
  mp_size_t res_size;
  mp_size_t limb_cnt = cnt / GMP_NUMB_BITS;
  mp_srcptr in_ptr = in->_mp_d;

  if (in_size > limb_cnt)
    {
      /* The input operand is (probably) greater than 2**CNT.  */
      mp_limb_t x;

      x = in_ptr[limb_cnt] & (((mp_limb_t) 1 << cnt % GMP_NUMB_BITS) - 1);
      if (x != 0)
	{
	  res_size = limb_cnt + 1;
	  if (res->_mp_alloc < res_size)
	    _mpz_realloc (res, res_size);

	  res->_mp_d[limb_cnt] = x;
	}
      else
	{
	  res_size = limb_cnt;
	  MPN_NORMALIZE (in_ptr, res_size);

	  if (res->_mp_alloc < res_size)
	    _mpz_realloc (res, res_size);

	  limb_cnt = res_size;
	}
    }
  else
    {
      /* The input operand is smaller than 2**CNT.  We perform a no-op,
	 apart from that we might need to copy IN to RES.  */
      res_size = in_size;
      if (res->_mp_alloc < res_size)
	_mpz_realloc (res, res_size);

      limb_cnt = res_size;
    }

  if (res != in)
    MPN_COPY (res->_mp_d, in->_mp_d, limb_cnt);
  res->_mp_size = in->_mp_size >= 0 ? res_size : -res_size;
}