1 // SPDX-License-Identifier: GPL-2.0-or-later 1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* mpihelp-mul_3.c - MPI helper functions 2 /* mpihelp-mul_3.c - MPI helper functions
3 * Copyright (C) 1994, 1996, 1997, 1998, 2001 3 * Copyright (C) 1994, 1996, 1997, 1998, 2001 Free Software Foundation, Inc.
4 * 4 *
5 * This file is part of GnuPG. 5 * This file is part of GnuPG.
6 * 6 *
7 * Note: This code is heavily based on the GNU 7 * Note: This code is heavily based on the GNU MP Library.
8 * Actually it's the same code with only 8 * Actually it's the same code with only minor changes in the
9 * way the data is stored; this is to su 9 * way the data is stored; this is to support the abstraction
10 * of an optional secure memory allocati 10 * of an optional secure memory allocation which may be used
11 * to avoid revealing of sensitive data 11 * to avoid revealing of sensitive data due to paging etc.
12 * The GNU MP Library itself is publishe 12 * The GNU MP Library itself is published under the LGPL;
13 * however I decided to publish this cod 13 * however I decided to publish this code under the plain GPL.
14 */ 14 */
15 15
16 #include "mpi-internal.h" 16 #include "mpi-internal.h"
17 #include "longlong.h" 17 #include "longlong.h"
18 18
19 mpi_limb_t 19 mpi_limb_t
20 mpihelp_submul_1(mpi_ptr_t res_ptr, mpi_ptr_t 20 mpihelp_submul_1(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr,
21 mpi_size_t s1_size, mpi_limb_ 21 mpi_size_t s1_size, mpi_limb_t s2_limb)
22 { 22 {
23 mpi_limb_t cy_limb; 23 mpi_limb_t cy_limb;
24 mpi_size_t j; 24 mpi_size_t j;
25 mpi_limb_t prod_high, prod_low; 25 mpi_limb_t prod_high, prod_low;
26 mpi_limb_t x; 26 mpi_limb_t x;
27 27
28 /* The loop counter and index J goes f 28 /* The loop counter and index J goes from -SIZE to -1. This way
29 * the loop becomes faster. */ 29 * the loop becomes faster. */
30 j = -s1_size; 30 j = -s1_size;
31 res_ptr -= j; 31 res_ptr -= j;
32 s1_ptr -= j; 32 s1_ptr -= j;
33 33
34 cy_limb = 0; 34 cy_limb = 0;
35 do { 35 do {
36 umul_ppmm(prod_high, prod_low, 36 umul_ppmm(prod_high, prod_low, s1_ptr[j], s2_limb);
37 37
38 prod_low += cy_limb; 38 prod_low += cy_limb;
39 cy_limb = (prod_low < cy_limb 39 cy_limb = (prod_low < cy_limb ? 1 : 0) + prod_high;
40 40
41 x = res_ptr[j]; 41 x = res_ptr[j];
42 prod_low = x - prod_low; 42 prod_low = x - prod_low;
43 cy_limb += prod_low > x ? 1 : 43 cy_limb += prod_low > x ? 1 : 0;
44 res_ptr[j] = prod_low; 44 res_ptr[j] = prod_low;
45 } while (++j); 45 } while (++j);
46 46
47 return cy_limb; 47 return cy_limb;
48 } 48 }
49 49
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.