1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
|
// SPDX-License-Identifier: GPL-2.0-or-later
/* mpi-sub-ui.c - Subtract an unsigned integer from an MPI.
*
* Copyright 1991, 1993, 1994, 1996, 1999-2002, 2004, 2012, 2013, 2015
* Free Software Foundation, Inc.
*
* This file was based on the GNU MP Library source file:
* https://gmplib.org/repo/gmp-6.2/file/510b83519d1c/mpz/aors_ui.h
*
* The GNU MP Library is free software; you can redistribute it and/or modify
* it under the terms of either:
*
* * the GNU Lesser General Public License as published by the Free
* Software Foundation; either version 3 of the License, or (at your
* option) any later version.
*
* or
*
* * the GNU General Public License as published by the Free Software
* Foundation; either version 2 of the License, or (at your option) any
* later version.
*
* or both in parallel, as here.
*
* The GNU MP Library is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* for more details.
*
* You should have received copies of the GNU General Public License and the
* GNU Lesser General Public License along with the GNU MP Library. If not,
* see https://www.gnu.org/licenses/.
*/
#include "mpi-internal.h"
int mpi_sub_ui(MPI w, MPI u, unsigned long vval)
{
if (u->nlimbs == 0) {
if (mpi_resize(w, 1) < 0)
return -ENOMEM;
w->d[0] = vval;
w->nlimbs = (vval != 0);
w->sign = (vval != 0);
return 0;
}
/* If not space for W (and possible carry), increase space. */
if (mpi_resize(w, u->nlimbs + 1))
return -ENOMEM;
if (u->sign) {
mpi_limb_t cy;
cy = mpihelp_add_1(w->d, u->d, u->nlimbs, (mpi_limb_t) vval);
w->d[u->nlimbs] = cy;
w->nlimbs = u->nlimbs + cy;
w->sign = 1;
} else {
/* The signs are different. Need exact comparison to determine
* which operand to subtract from which.
*/
if (u->nlimbs == 1 && u->d[0] < vval) {
w->d[0] = vval - u->d[0];
w->nlimbs = 1;
w->sign = 1;
} else {
mpihelp_sub_1(w->d, u->d, u->nlimbs, (mpi_limb_t) vval);
/* Size can decrease with at most one limb. */
w->nlimbs = (u->nlimbs - (w->d[u->nlimbs - 1] == 0));
w->sign = 0;
}
}
mpi_normalize(w);
return 0;
}
EXPORT_SYMBOL_GPL(mpi_sub_ui);
|
