1*4882a593Smuzhiyun // SPDX-License-Identifier: GPL-2.0-or-later
2*4882a593Smuzhiyun /* mpihelp-mul_2.c - MPI helper functions
3*4882a593Smuzhiyun * Copyright (C) 1994, 1996, 1997, 1998, 2001 Free Software Foundation, Inc.
4*4882a593Smuzhiyun *
5*4882a593Smuzhiyun * This file is part of GnuPG.
6*4882a593Smuzhiyun *
7*4882a593Smuzhiyun * Note: This code is heavily based on the GNU MP Library.
8*4882a593Smuzhiyun * Actually it's the same code with only minor changes in the
9*4882a593Smuzhiyun * way the data is stored; this is to support the abstraction
10*4882a593Smuzhiyun * of an optional secure memory allocation which may be used
11*4882a593Smuzhiyun * to avoid revealing of sensitive data due to paging etc.
12*4882a593Smuzhiyun * The GNU MP Library itself is published under the LGPL;
13*4882a593Smuzhiyun * however I decided to publish this code under the plain GPL.
14*4882a593Smuzhiyun */
15*4882a593Smuzhiyun
16*4882a593Smuzhiyun #include "mpi-internal.h"
17*4882a593Smuzhiyun #include "longlong.h"
18*4882a593Smuzhiyun
19*4882a593Smuzhiyun mpi_limb_t
mpihelp_addmul_1(mpi_ptr_t res_ptr,mpi_ptr_t s1_ptr,mpi_size_t s1_size,mpi_limb_t s2_limb)20*4882a593Smuzhiyun mpihelp_addmul_1(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr,
21*4882a593Smuzhiyun mpi_size_t s1_size, mpi_limb_t s2_limb)
22*4882a593Smuzhiyun {
23*4882a593Smuzhiyun mpi_limb_t cy_limb;
24*4882a593Smuzhiyun mpi_size_t j;
25*4882a593Smuzhiyun mpi_limb_t prod_high, prod_low;
26*4882a593Smuzhiyun mpi_limb_t x;
27*4882a593Smuzhiyun
28*4882a593Smuzhiyun /* The loop counter and index J goes from -SIZE to -1. This way
29*4882a593Smuzhiyun * the loop becomes faster. */
30*4882a593Smuzhiyun j = -s1_size;
31*4882a593Smuzhiyun res_ptr -= j;
32*4882a593Smuzhiyun s1_ptr -= j;
33*4882a593Smuzhiyun
34*4882a593Smuzhiyun cy_limb = 0;
35*4882a593Smuzhiyun do {
36*4882a593Smuzhiyun umul_ppmm(prod_high, prod_low, s1_ptr[j], s2_limb);
37*4882a593Smuzhiyun
38*4882a593Smuzhiyun prod_low += cy_limb;
39*4882a593Smuzhiyun cy_limb = (prod_low < cy_limb ? 1 : 0) + prod_high;
40*4882a593Smuzhiyun
41*4882a593Smuzhiyun x = res_ptr[j];
42*4882a593Smuzhiyun prod_low = x + prod_low;
43*4882a593Smuzhiyun cy_limb += prod_low < x ? 1 : 0;
44*4882a593Smuzhiyun res_ptr[j] = prod_low;
45*4882a593Smuzhiyun } while (++j);
46*4882a593Smuzhiyun return cy_limb;
47*4882a593Smuzhiyun }
48