1 // SPDX-License-Identifier: GPL-2.0-or-later 1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* mpihelp-mul_1.c - MPI helper functions 2 /* mpihelp-mul_1.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_mul_1(mpi_ptr_t res_ptr, mpi_ptr_t s1_ 20 mpihelp_mul_1(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr, mpi_size_t s1_size,
21 mpi_limb_t s2_limb) 21 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 26
27 /* The loop counter and index J goes f 27 /* The loop counter and index J goes from -S1_SIZE to -1. This way
28 * the loop becomes faster. */ 28 * the loop becomes faster. */
29 j = -s1_size; 29 j = -s1_size;
30 30
31 /* Offset the base pointers to compens 31 /* Offset the base pointers to compensate for the negative indices. */
32 s1_ptr -= j; 32 s1_ptr -= j;
33 res_ptr -= j; 33 res_ptr -= j;
34 34
35 cy_limb = 0; 35 cy_limb = 0;
36 do { 36 do {
37 umul_ppmm(prod_high, prod_low, 37 umul_ppmm(prod_high, prod_low, s1_ptr[j], s2_limb);
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 res_ptr[j] = prod_low; 40 res_ptr[j] = prod_low;
41 } while (++j); 41 } while (++j);
42 42
43 return cy_limb; 43 return cy_limb;
44 } 44 }
45 45
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