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/* mpi-add.c - MPI functions
* Copyright (C) 1994, 1996, 1998, 2001, 2002,
* 2003 Free Software Foundation, Inc.
*
* This file is part of Libgcrypt.
*
* 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.
*/
#include "mpi-internal.h"
int mpi_add(MPI w, MPI u, MPI v)
{
mpi_ptr_t wp, up, vp;
mpi_size_t usize, vsize, wsize;
int usign, vsign, wsign;
int err;
if (u->nlimbs < v->nlimbs) { /* Swap U and V. */
usize = v->nlimbs;
usign = v->sign;
vsize = u->nlimbs;
vsign = u->sign;
wsize = usize + 1;
err = RESIZE_IF_NEEDED(w, wsize);
if (err)
return err;
/* 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;
err = RESIZE_IF_NEEDED(w, wsize);
if (err)
return err;
/* 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;
return 0;
}
EXPORT_SYMBOL_GPL(mpi_add);
int mpi_sub(MPI w, MPI u, MPI v)
{
int err;
MPI vv;
vv = mpi_copy(v);
if (!vv)
return -ENOMEM;
vv->sign = !vv->sign;
err = mpi_add(w, u, vv);
mpi_free(vv);
return err;
}
EXPORT_SYMBOL_GPL(mpi_sub);
int mpi_addm(MPI w, MPI u, MPI v, MPI m)
{
return mpi_add(w, u, v) ?:
mpi_mod(w, w, m);
}
EXPORT_SYMBOL_GPL(mpi_addm);
int mpi_subm(MPI w, MPI u, MPI v, MPI m)
{
return mpi_sub(w, u, v) ?:
mpi_mod(w, w, m);
}
EXPORT_SYMBOL_GPL(mpi_subm);
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