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annotate libtommath/bn_mp_2expt.c @ 1684:d5d25ce2a2ed

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cast to fix warning
author Matt Johnston <matt@ucc.asn.au>
date Tue, 26 May 2020 19:57:28 +0800
parents f52919ffd3b1
children 1051e4eea25a
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f52919ffd3b1 update ltm to 1.1.0 and enable FIPS 186.4 compliant key-generation (#79)
Steffen Jaeckel <s_jaeckel@gmx.de>
parents: 1470
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1 #include "tommath_private.h"
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2 #ifdef BN_MP_2EXPT_C
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3 /* LibTomMath, multiple-precision integer library -- Tom St Denis
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4 *
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5 * LibTomMath is a library that provides multiple-precision
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6 * integer arithmetic as well as number theoretic functionality.
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7 *
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8 * The library was designed directly after the MPI library by
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9 * Michael Fromberger but has been written from scratch with
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10 * additional optimizations in place.
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11 *
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12 * SPDX-License-Identifier: Unlicense
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13 */
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14
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15 /* computes a = 2**b
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16 *
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17 * Simple algorithm which zeroes the int, grows it then just sets one bit
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18 * as required.
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19 */
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20 int mp_2expt(mp_int *a, int b)
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21 {
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22 int res;
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23
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24 /* zero a as per default */
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25 mp_zero(a);
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27 /* grow a to accomodate the single bit */
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28 if ((res = mp_grow(a, (b / DIGIT_BIT) + 1)) != MP_OKAY) {
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29 return res;
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30 }
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32 /* set the used count of where the bit will go */
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33 a->used = (b / DIGIT_BIT) + 1;
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35 /* put the single bit in its place */
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36 a->dp[b / DIGIT_BIT] = (mp_digit)1 << (mp_digit)(b % DIGIT_BIT);
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38 return MP_OKAY;
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39 }
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40 #endif
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42 /* ref: HEAD -> master, tag: v1.1.0 */
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43 /* git commit: 08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */
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44 /* commit time: 2019-01-28 20:32:32 +0100 */