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+/* mpi-add.c - MPI functions
+ * Copyright (C) 1998, 1999, 2000, 2001 Free Software Foundation, Inc.
+ * Copyright (C) 1994, 1996 Free Software Foundation, Inc.
+ *
+ * This file is part of GnuPG.
+ *
+ * GnuPG 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.
+ *
+ * GnuPG 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
+ * USA.
+ *
+ * Note: This code is heavily based on the GNU MP Library.
+ * Actually it's the same code with only minor changes in the
+ * way the data is stored; this is to support the abstraction
+ * of an optional secure memory allocation which may be used
+ * to avoid revealing of sensitive data due to paging etc.
+ * The GNU MP Library itself is published under the LGPL;
+ * however I decided to publish this code under the plain GPL.
+ */
+
+#include <config.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "mpi-internal.h"
+
+
+/****************
+ * Add the unsigned integer V to the mpi-integer U and store the
+ * result in W. U and V may be the same.
+ */
+void
+mpi_add_ui(MPI w, MPI u, unsigned long v )
+{
+ mpi_ptr_t wp, up;
+ mpi_size_t usize, wsize;
+ int usign, wsign;
+
+ usize = u->nlimbs;
+ usign = u->sign;
+ wsign = 0;
+
+ /* If not space for W (and possible carry), increase space. */
+ wsize = usize + 1;
+ if( w->alloced < wsize )
+ mpi_resize(w, wsize);
+
+ /* These must be after realloc (U may be the same as W). */
+ up = u->d;
+ wp = w->d;
+
+ if( !usize ) { /* simple */
+ wp[0] = v;
+ wsize = v? 1:0;
+ }
+ else if( !usign ) { /* mpi is not negative */
+ mpi_limb_t cy;
+ cy = mpihelp_add_1(wp, up, usize, v);
+ wp[usize] = cy;
+ wsize = usize + cy;
+ }
+ else { /* The signs are different. Need exact comparison to determine
+ * which operand to subtract from which. */
+ if( usize == 1 && up[0] < v ) {
+ wp[0] = v - up[0];
+ wsize = 1;
+ }
+ else {
+ mpihelp_sub_1(wp, up, usize, v);
+ /* Size can decrease with at most one limb. */
+ wsize = usize - (wp[usize-1]==0);
+ wsign = 1;
+ }
+ }
+
+ w->nlimbs = wsize;
+ w->sign = wsign;
+}
+
+
+void
+mpi_add(MPI w, MPI u, MPI v)
+{
+ mpi_ptr_t wp, up, vp;
+ mpi_size_t usize, vsize, wsize;
+ int usign, vsign, wsign;
+
+ if( u->nlimbs < v->nlimbs ) { /* Swap U and V. */
+ usize = v->nlimbs;
+ usign = v->sign;
+ vsize = u->nlimbs;
+ vsign = u->sign;
+ wsize = usize + 1;
+ RESIZE_IF_NEEDED(w, wsize);
+ /* These must be after realloc (u or v may be the same as w). */
+ up = v->d;
+ vp = u->d;
+ }
+ else {
+ usize = u->nlimbs;
+ usign = u->sign;
+ vsize = v->nlimbs;
+ vsign = v->sign;
+ wsize = usize + 1;
+ RESIZE_IF_NEEDED(w, wsize);
+ /* These must be after realloc (u or v may be the same as w). */
+ up = u->d;
+ vp = v->d;
+ }
+ wp = w->d;
+ wsign = 0;
+
+ if( !vsize ) { /* simple */
+ MPN_COPY(wp, up, usize );
+ wsize = usize;
+ wsign = usign;
+ }
+ else if( usign != vsign ) { /* different sign */
+ /* This test is right since USIZE >= VSIZE */
+ if( usize != vsize ) {
+ mpihelp_sub(wp, up, usize, vp, vsize);
+ wsize = usize;
+ MPN_NORMALIZE(wp, wsize);
+ wsign = usign;
+ }
+ else if( mpihelp_cmp(up, vp, usize) < 0 ) {
+ mpihelp_sub_n(wp, vp, up, usize);
+ wsize = usize;
+ MPN_NORMALIZE(wp, wsize);
+ if( !usign )
+ wsign = 1;
+ }
+ else {
+ mpihelp_sub_n(wp, up, vp, usize);
+ wsize = usize;
+ MPN_NORMALIZE(wp, wsize);
+ if( usign )
+ wsign = 1;
+ }
+ }
+ else { /* U and V have same sign. Add them. */
+ mpi_limb_t cy = mpihelp_add(wp, up, usize, vp, vsize);
+ wp[usize] = cy;
+ wsize = usize + cy;
+ if( usign )
+ wsign = 1;
+ }
+
+ w->nlimbs = wsize;
+ w->sign = wsign;
+}
+
+
+/****************
+ * Subtract the unsigned integer V from the mpi-integer U and store the
+ * result in W.
+ */
+void
+mpi_sub_ui(MPI w, MPI u, unsigned long v )
+{
+ mpi_ptr_t wp, up;
+ mpi_size_t usize, wsize;
+ int usign, wsign;
+
+ usize = u->nlimbs;
+ usign = u->sign;
+ wsign = 0;
+
+ /* If not space for W (and possible carry), increase space. */
+ wsize = usize + 1;
+ if( w->alloced < wsize )
+ mpi_resize(w, wsize);
+
+ /* These must be after realloc (U may be the same as W). */
+ up = u->d;
+ wp = w->d;
+
+ if( !usize ) { /* simple */
+ wp[0] = v;
+ wsize = v? 1:0;
+ wsign = 1;
+ }
+ else if( usign ) { /* mpi and v are negative */
+ mpi_limb_t cy;
+ cy = mpihelp_add_1(wp, up, usize, v);
+ wp[usize] = cy;
+ wsize = usize + cy;
+ }
+ else { /* The signs are different. Need exact comparison to determine
+ * which operand to subtract from which. */
+ if( usize == 1 && up[0] < v ) {
+ wp[0] = v - up[0];
+ wsize = 1;
+ wsign = 1;
+ }
+ else {
+ mpihelp_sub_1(wp, up, usize, v);
+ /* Size can decrease with at most one limb. */
+ wsize = usize - (wp[usize-1]==0);
+ }
+ }
+
+ w->nlimbs = wsize;
+ w->sign = wsign;
+}
+
+void
+mpi_sub(MPI w, MPI u, MPI v)
+{
+ if( w == v ) {
+ MPI vv = mpi_copy(v);
+ vv->sign = !vv->sign;
+ mpi_add( w, u, vv );
+ mpi_free(vv);
+ }
+ else {
+ /* fixme: this is not thread-save (we temp. modify v) */
+ v->sign = !v->sign;
+ mpi_add( w, u, v );
+ v->sign = !v->sign;
+ }
+}
+
+
+void
+mpi_addm( MPI w, MPI u, MPI v, MPI m)
+{
+ mpi_add(w, u, v);
+ mpi_fdiv_r( w, w, m );
+}
+
+void
+mpi_subm( MPI w, MPI u, MPI v, MPI m)
+{
+ mpi_sub(w, u, v);
+ mpi_fdiv_r( w, w, m );
+}
+
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