blob: 54bd1d9b3578323309e23e19d570f6aed87ef67a (
plain)
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
|
#include "tommath_private.h"
#ifdef BN_MP_2EXPT_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis
*
* LibTomMath is a library that provides multiple-precision
* integer arithmetic as well as number theoretic functionality.
*
* The library was designed directly after the MPI library by
* Michael Fromberger but has been written from scratch with
* additional optimizations in place.
*
* SPDX-License-Identifier: Unlicense
*/
/* computes a = 2**b
*
* Simple algorithm which zeroes the int, grows it then just sets one bit
* as required.
*/
int mp_2expt(mp_int *a, int b)
{
int res;
/* zero a as per default */
mp_zero(a);
/* grow a to accomodate the single bit */
if ((res = mp_grow(a, (b / DIGIT_BIT) + 1)) != MP_OKAY) {
return res;
}
/* set the used count of where the bit will go */
a->used = (b / DIGIT_BIT) + 1;
/* put the single bit in its place */
a->dp[b / DIGIT_BIT] = (mp_digit)1 << (mp_digit)(b % DIGIT_BIT);
return MP_OKAY;
}
#endif
/* ref: HEAD -> master, tag: v1.1.0 */
/* git commit: 08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */
/* commit time: 2019-01-28 20:32:32 +0100 */
|
