/* mpn_sec_tabselect.

Copyright 2007-2009, 2011, 2013 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 either:

  * 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.

or

  * the GNU General Public License as published by the Free Software

    Foundation; either version 2 of the License, or (at your option) any

    later version.

or both in parallel, as here.

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 General Public License

for more details.

You should have received copies of the GNU General Public License and the

GNU Lesser General Public License along with the GNU MP Library.  If not,

see https://www.gnu.org/licenses/.  */

#include "gmp.h"

#include "gmp-impl.h"

/* Select entry `which' from table `tab', which has nents entries, each `n'

   limbs.  Store the selected entry at rp.  Reads entire table to avoid

   side-channel information leaks.  O(n*nents).  */

void

mpn_sec_tabselect (volatile mp_limb_t *rp, volatile const mp_limb_t *tab,

		   mp_size_t n, mp_size_t nents, mp_size_t which)

{

  mp_size_t k, i;

  mp_limb_t mask;

  volatile const mp_limb_t *tp;

  for (k = 0; k < nents; k++)

    {

      mask = -(mp_limb_t) (which == k);

      tp = tab + n * k;

      for (i = 0; i < n; i++)

	{

	  rp[i] = (rp[i] & ~mask) | (tp[i] & mask);

	}

    }

}