/* mpi-mul.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 <linux/export.h>

#include "mpi-internal.h"

int 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;
        int err = 0;

        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);
                        if (!wp)
                                return -ENOMEM;
                        assign_wp = 1;
                } else {
                        err = mpi_resize(w, wsize);
                        if (err)
                                return err;
                        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);
                        if (!up)
                                return -ENOMEM;
                        /* 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);
                        if (!vp)
                                return -ENOMEM;
                        /* Copy to the temporary space.  */
                        MPN_COPY(vp, wp, vsize);
                }
        }

        if (!vsize)
                wsize = 0;
        else {
                err = mpihelp_mul(wp, up, usize, vp, vsize, &cy);
                if (err) {
                        if (assign_wp)
                                mpi_free_limb_space(wp);
                        goto free_tmp_limb;
                }
                wsize -= cy ? 0:1;
        }

        if (assign_wp)
                mpi_assign_limb_space(w, wp, wsize);
        w->nlimbs = wsize;
        w->sign = sign_product;

free_tmp_limb:
        if (tmp_limb)
                mpi_free_limb_space(tmp_limb);
        return err;
}
EXPORT_SYMBOL_GPL(mpi_mul);

int mpi_mulm(MPI w, MPI u, MPI v, MPI m)
{
        return mpi_mul(w, u, v) ?:
               mpi_tdiv_r(w, w, m);
}
EXPORT_SYMBOL_GPL(mpi_mulm);