/* mpihelp-add_1.c  -  MPI helper functions
 * Modified by No Such Labs. (C) 2015. See README.
 *
 * This file was originally part of Gnu Privacy Guard (GPG), ver. 1.4.10,
 * SHA256(gnupg-1.4.10.tar.gz):
 *        0bfd74660a2f6cedcf7d8256db4a63c996ffebbcdc2cf54397bfb72878c5a85a
 * (C) 1994-2005 Free Software Foundation, Inc.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program 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 a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <stdio.h>
#include <stdlib.h>

#include "knobs.h"
#include "mpi-internal.h"
#include "longlong.h"

mpi_limb_t
mpihelp_add_n( mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr,
	       mpi_ptr_t s2_ptr, mpi_size_t size)
{
    mpi_limb_t x, y, cy;
    mpi_size_t j;

    /* The loop counter and index J goes from -SIZE to -1.  This way
       the loop becomes faster.  */
    j = -size;

    /* Offset the base pointers to compensate for the negative indices. */
    s1_ptr -= j;
    s2_ptr -= j;
    res_ptr -= j;

    cy = 0;
    do {
	y = s2_ptr[j];
	x = s1_ptr[j];
	y += cy;		  /* add previous carry to one addend */
	cy = y < cy;		  /* get out carry from that addition */
	y += x; 		  /* add other addend */
	cy += y < x;		  /* get out carry from that add, combine */
	res_ptr[j] = y;
    } while( ++j );

    return cy;
}