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222 lines
5.0 KiB
C
222 lines
5.0 KiB
C
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/* mpi-add.c - MPI functions
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* Copyright (c) 1997 by Werner Koch (dd9jn)
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*
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* This file is part of G10.
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*
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* G10 is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* G10 is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
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*/
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#include <config.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include "mpi-internal.h"
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/****************
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* Add the unsigned integer V to the mpi-integer U and store the
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* result in W. U and V may be the same.
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*/
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void
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mpi_add_ui(MPI w, MPI u, unsigned long v )
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{
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mpi_ptr_t wp, up;
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mpi_size_t usize, wsize;
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int usign, wsign;
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usize = u->nlimbs;
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usign = u->sign;
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wsign = 0;
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/* If not space for W (and possible carry), increase space. */
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wsize = usize + 1;
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if( w->alloced < wsize )
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mpi_resize(w, wsize);
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/* These must be after realloc (U may be the same as W). */
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up = u->d;
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wp = w->d;
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if( !usize ) { /* simple */
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wp[0] = v;
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wsize = v? 1:0;
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}
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else if( !usign ) { /* mpi is not negative */
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mpi_limb_t cy;
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cy = mpihelp_add_1(wp, up, usize, v);
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wp[usize] = cy;
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wsize = usize + cy;
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}
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else { /* The signs are different. Need exact comparison to determine
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* which operand to subtract from which. */
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if( usize == 1 && up[0] < v ) {
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wp[0] = v - up[0];
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wsize = 1;
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}
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else {
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mpihelp_sub_1(wp, up, usize, v);
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/* Size can decrease with at most one limb. */
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wsize = (usize - (wp[usize-1]? 0:1));
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wsign = 1;
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}
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}
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w->nlimbs = wsize;
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w->sign = wsign;
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}
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void
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mpi_add(MPI w, MPI u, MPI v)
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{
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mpi_ptr_t wp, up, vp;
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mpi_size_t usize, vsize, wsize;
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int usign, vsign, wsign;
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usize = u->nlimbs;
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vsize = v->nlimbs;
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usign = u->sign;
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vsign = v->sign;
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if( usize < vsize ) { /* Swap U and V. */
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{ MPI t; t = u; u = v; v = t; }
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{ mpi_size_t t = usize; usize = vsize; vsize = t; }
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{ int t = usign; usign = vsign; vsign = t; }
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}
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/* If not space for w (and possible carry), increase space. */
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wsize = usize + 1;
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if( w->alloced < wsize )
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mpi_resize(w, wsize);
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wsign = 0;
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/* These must be after realloc (u or v may be the same as w). */
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up = u->d;
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vp = v->d;
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wp = w->d;
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if( !vsize ) { /* simple */
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MPN_COPY(wp, up, usize );
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wsize = usize;
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wsign = usign;
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}
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else if( usign != vsign ) { /* different sign */
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/* This test is right since USIZE >= VSIZE */
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if( usize != vsize ) {
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mpihelp_sub(wp, up, usize, vp, vsize);
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wsize = usize;
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MPN_NORMALIZE(wp, wsize);
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wsign = usign;
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}
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else if( mpihelp_cmp(up, vp, usize) < 0 ) {
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mpihelp_sub_n(wp, vp, up, usize);
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wsize = usize;
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MPN_NORMALIZE(wp, wsize);
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if( !usign )
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wsign = 1;
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}
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else {
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mpihelp_sub_n(wp, up, vp, usize);
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wsize = usize;
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MPN_NORMALIZE(wp, wsize);
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if( usign )
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wsign = 1;
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}
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}
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else { /* U and V have same sign. Add them. */
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mpi_limb_t cy = mpihelp_add(wp, up, usize, vp, vsize);
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wp[usize] = cy;
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wsize = usize + cy;
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if( usign )
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wsize = 1;
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}
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w->nlimbs = wsize;
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w->sign = wsign;
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}
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/****************
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* Subtract the unsigned integer V from the mpi-integer U and store the
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* result in W.
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*/
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void
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mpi_sub_ui(MPI w, MPI u, unsigned long v )
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{
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mpi_ptr_t wp, up;
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mpi_size_t usize, wsize;
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int usign, wsign;
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usize = u->nlimbs;
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usign = u->sign;
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wsign = 0;
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/* If not space for W (and possible carry), increase space. */
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wsize = usize + 1;
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if( w->alloced < wsize )
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mpi_resize(w, wsize);
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/* These must be after realloc (U may be the same as W). */
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up = u->d;
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wp = w->d;
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if( !usize ) { /* simple */
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wp[0] = v;
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wsize = v? 1:0;
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wsign = 1;
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}
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else if( usign ) { /* mpi and v are negative */
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mpi_limb_t cy;
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cy = mpihelp_add_1(wp, up, usize, v);
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wp[usize] = cy;
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wsize = usize + cy;
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}
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else { /* The signs are different. Need exact comparison to determine
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* which operand to subtract from which. */
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if( usize == 1 && up[0] < v ) {
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wp[0] = v - up[0];
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wsize = 1;
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wsign = 1;
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}
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else {
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mpihelp_sub_1(wp, up, usize, v);
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/* Size can decrease with at most one limb. */
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wsize = (usize - (wp[usize-1]? 1:0));
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}
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}
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w->nlimbs = wsize;
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w->sign = wsign;
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}
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void
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mpi_sub(MPI w, MPI u, MPI v)
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{
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if( w == v ) {
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MPI vv = mpi_copy(v);
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vv->sign = !vv->sign;
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mpi_add( w, u, vv );
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m_free(vv);
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}
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else {
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/* fixme: this is not thread-save (we temp. modify v) */
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v->sign = !v->sign;
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mpi_add( w, u, v );
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v->sign = !v->sign;
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}
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}
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