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Werner Koch 1997-11-18 14:06:00 +00:00
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mpi/mpi-mul.c Normal file
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/* mpi-mul.c - MPI functions
* Copyright (c) 1997 by Werner Koch (dd9jn)
*
* This file is part of G10.
*
* G10 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 2 of the License, or
* (at your option) any later version.
*
* G10 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, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*/
#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include "mpi-internal.h"
void
mpi_mul_ui( MPI prod, MPI mult, unsigned long small_mult )
{
mpi_size_t size, prod_size;
mpi_ptr_t prod_ptr;
mpi_limb_t cy;
int sign;
size = mult->nlimbs;
sign = mult->sign;
if( !size || !small_mult ) {
prod->nlimbs = 0;
prod->sign = 0;
return;
}
prod_size = size + 1;
if( prod->alloced < prod_size )
mpi_resize( prod, prod_size );
prod_ptr = prod->d;
cy = mpihelp_mul_1( prod_ptr, mult->d, size, (mpi_limb_t)small_mult );
if( cy )
prod_ptr[size++] = cy;
prod->nlimbs = size;
prod->sign = sign;
}
void
mpi_mul_2exp( MPI w, MPI u, unsigned long cnt)
{
mpi_size_t usize, wsize, limb_cnt;
mpi_ptr_t wp;
mpi_limb_t wlimb;
int usign, wsign;
usize = u->nlimbs;
usign = u->sign;
if( !usize ) {
w->nlimbs = 0;
w->sign = 0;
return;
}
limb_cnt = cnt / BITS_PER_MPI_LIMB;
wsize = usize + limb_cnt + 1;
if( w->alloced < wsize )
mpi_resize(w, wsize );
wp = w->d;
wsize = usize + limb_cnt;
wsign = usign;
cnt %= BITS_PER_MPI_LIMB;
if( cnt ) {
wlimb = mpihelp_lshift( wp + limb_cnt, u->d, usize, cnt );
if( wlimb ) {
wp[wsize] = wlimb;
wsize++;
}
}
else {
MPN_COPY_DECR( wp + limb_cnt, u->d, usize );
}
/* Zero all whole limbs at low end. Do it here and not before calling
* mpn_lshift, not to lose for U == W. */
MPN_ZERO( wp, limb_cnt );
w->nlimbs = wsize;
w->sign = wsign;
}
void
mpi_mul( MPI w, MPI u, MPI v)
{
mpi_size_t usize, vsize, wsize;
mpi_ptr_t up, vp, wp;
mpi_limb_t cy;
int usign, vsign, sign_product;
int assign_wp=0;
mpi_ptr_t tmp_limb=NULL;
if( u->nlimbs < v->nlimbs ) { /* Swap U and V. */
usize = v->nlimbs;
usign = v->sign;
up = v->d;
vsize = u->nlimbs;
vsign = u->sign;
vp = u->d;
}
else {
usize = u->nlimbs;
usign = u->sign;
up = u->d;
vsize = v->nlimbs;
vsign = v->sign;
vp = v->d;
}
sign_product = usign ^ vsign;
wp = w->d;
/* Ensure W has space enough to store the result. */
wsize = usize + vsize;
if( w->alloced < wsize ) {
if( wp == up || wp == vp ) {
wp = mpi_alloc_limb_space( wsize );
assign_wp = 1;
}
else {
mpi_resize(w, wsize );
wp = w->d;
}
}
else { /* Make U and V not overlap with W. */
if( wp == up ) {
/* W and U are identical. Allocate temporary space for U. */
up = tmp_limb = mpi_alloc_limb_space( usize );
/* Is V identical too? Keep it identical with U. */
if( wp == vp )
vp = up;
/* Copy to the temporary space. */
MPN_COPY( up, wp, usize );
}
else if( wp == vp ) {
/* W and V are identical. Allocate temporary space for V. */
vp = tmp_limb = mpi_alloc_limb_space( vsize );
/* Copy to the temporary space. */
MPN_COPY( vp, wp, vsize );
}
}
if( !vsize )
wsize = 0;
else {
cy = mpihelp_mul( wp, up, usize, vp, vsize );
wsize -= cy? 0:1;
}
if( assign_wp )
mpi_assign_limb_space( w, wp, wsize );
w->nlimbs = wsize;
w->sign = sign_product;
if( tmp_limb )
mpi_free_limb_space( tmp_limb );
}