156 lines
3.4 KiB
C
156 lines
3.4 KiB
C
/* mpi-add.c - MPI functions
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* Copyright (C) 1994, 1996, 1998, 2001, 2002,
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* 2003 Free Software Foundation, Inc.
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*
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* This file is part of Libgcrypt.
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*
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* Note: This code is heavily based on the GNU MP Library.
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* Actually it's the same code with only minor changes in the
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* way the data is stored; this is to support the abstraction
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* of an optional secure memory allocation which may be used
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* to avoid revealing of sensitive data due to paging etc.
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*/
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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 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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} 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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} else {
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/* The signs are different. Need exact comparison to determine
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* which operand to subtract from which.
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*/
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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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} 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);
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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 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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if (u->nlimbs < v->nlimbs) { /* Swap U and V. */
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usize = v->nlimbs;
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usign = v->sign;
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vsize = u->nlimbs;
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vsign = u->sign;
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wsize = usize + 1;
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RESIZE_IF_NEEDED(w, wsize);
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/* These must be after realloc (u or v may be the same as w). */
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up = v->d;
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vp = u->d;
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} else {
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usize = u->nlimbs;
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usign = u->sign;
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vsize = v->nlimbs;
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vsign = v->sign;
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wsize = usize + 1;
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RESIZE_IF_NEEDED(w, wsize);
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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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}
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wp = w->d;
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wsign = 0;
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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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} 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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} 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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} 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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} 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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wsign = 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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EXPORT_SYMBOL_GPL(mpi_add);
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void mpi_sub(MPI w, MPI u, MPI v)
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{
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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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mpi_free(vv);
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}
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void mpi_addm(MPI w, MPI u, MPI v, MPI m)
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{
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mpi_add(w, u, v);
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mpi_mod(w, w, m);
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}
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EXPORT_SYMBOL_GPL(mpi_addm);
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void mpi_subm(MPI w, MPI u, MPI v, MPI m)
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{
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mpi_sub(w, u, v);
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mpi_mod(w, w, m);
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}
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EXPORT_SYMBOL_GPL(mpi_subm);
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