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ch1_mpi                 1 /* mpihelp-add_2.c  -  MPI helper functions
ch1_mpi                 2  * Modified by No Such Labs. (C) 2015. See README.
ch1_mpi                 3  *
ch1_mpi                 4  * This file was originally part of Gnu Privacy Guard (GPG), ver. 1.4.10,
ch1_mpi                 5  * SHA256(gnupg-1.4.10.tar.gz):
ch1_mpi                 6  *        0bfd74660a2f6cedcf7d8256db4a63c996ffebbcdc2cf54397bfb72878c5a85a
ch1_mpi                 7  * (C) 1994-2005 Free Software Foundation, Inc.
ch1_mpi                 8  *
ch1_mpi                 9  * This program is free software: you can redistribute it and/or modify
ch1_mpi                10  * it under the terms of the GNU General Public License as published by
ch1_mpi                11  * the Free Software Foundation, either version 3 of the License, or
ch1_mpi                12  * (at your option) any later version.
ch1_mpi                13  *
ch1_mpi                14  * This program is distributed in the hope that it will be useful,
ch1_mpi                15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
ch1_mpi                16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
ch1_mpi                17  * GNU General Public License for more details.
ch1_mpi                18  *
ch1_mpi                19  * You should have received a copy of the GNU General Public License
ch1_mpi                20  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
ch1_mpi                21  */
ch1_mpi                22 
ch1_mpi                23 #include <stdio.h>
ch1_mpi                24 #include <stdlib.h>
ch1_mpi                25 
ch1_mpi                26 #include "knobs.h"
ch1_mpi                27 #include "mpi-internal.h"
ch1_mpi                28 #include "longlong.h"
ch1_mpi                29 
ch1_mpi                30 mpi_limb_t
ch1_mpi                31 mpihelp_sub_n( mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr,
ch1_mpi                32 				  mpi_ptr_t s2_ptr, mpi_size_t size)
ch1_mpi                33 {
ch1_mpi                34     mpi_limb_t x, y, cy;
ch1_mpi                35     mpi_size_t j;
ch1_mpi                36 
ch1_mpi                37     /* The loop counter and index J goes from -SIZE to -1.  This way
ch1_mpi                38        the loop becomes faster.  */
ch1_mpi                39     j = -size;
ch1_mpi                40 
ch1_mpi                41     /* Offset the base pointers to compensate for the negative indices.  */
ch1_mpi                42     s1_ptr -= j;
ch1_mpi                43     s2_ptr -= j;
ch1_mpi                44     res_ptr -= j;
ch1_mpi                45 
ch1_mpi                46     cy = 0;
ch1_mpi                47     do {
ch1_mpi                48 	y = s2_ptr[j];
ch1_mpi                49 	x = s1_ptr[j];
ch1_mpi                50 	y += cy;		  /* add previous carry to subtrahend */
ch1_mpi                51 	cy = y < cy;		  /* get out carry from that addition */
ch1_mpi                52 	y = x - y;		  /* main subtract */
ch1_mpi                53 	cy += y > x;		  /* get out carry from the subtract, combine */
ch1_mpi                54 	res_ptr[j] = y;
ch1_mpi                55     } while( ++j );
ch1_mpi                56 
ch1_mpi                57     return cy;
ch1_mpi                58 }
ch1_mpi                59 
ch1_mpi                60