Mercurial > dropbear

annotate libtommath/bn_mp_count_bits.c @ 1663:c795520269f9

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Fallback for key gen without hard link support (#89) Add a non-atomic fallback for key generation on platforms where link() is not permitted (such as most stock Android installs) or on filesystems without hard link support (such as FAT).
author Matt Robinson <git@nerdoftheherd.com>
date Sat, 14 Mar 2020 14:37:35 +0000
parents f52919ffd3b1
children 1051e4eea25a
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1 #include "tommath_private.h"
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2 #ifdef BN_MP_COUNT_BITS_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 /* returns the number of bits in an int */
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16 int mp_count_bits(const mp_int *a)
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17 {
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18 int r;
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19 mp_digit q;
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21 /* shortcut */
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22 if (a->used == 0) {
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23 return 0;
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24 }
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26 /* get number of digits and add that */
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27 r = (a->used - 1) * DIGIT_BIT;
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28
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29 /* take the last digit and count the bits in it */
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30 q = a->dp[a->used - 1];
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31 while (q > (mp_digit)0) {
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32 ++r;
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33 q >>= (mp_digit)1;
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34 }
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35 return r;
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36 }
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37 #endif
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39 /* ref: HEAD -> master, tag: v1.1.0 */
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40 /* git commit: 08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */
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41 /* commit time: 2019-01-28 20:32:32 +0100 */