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annotate libtommath/bn_mp_count_bits.c @ 289:497fddd4a94e

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code was untested and wrong.
author Matt Johnston <matt@ucc.asn.au>
date Wed, 08 Mar 2006 15:46:24 +0000
parents eed26cff980b
children 5ff8218bcee9
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284
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1 #include <tommath.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 * The library is free for all purposes without any express
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13 * guarantee it works.
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14 *
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15 * Tom St Denis, [email protected], http://math.libtomcrypt.org
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16 */
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17
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18 /* returns the number of bits in an int */
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19 int
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20 mp_count_bits (mp_int * a)
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21 {
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22 int r;
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23 mp_digit q;
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24
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25 /* shortcut */
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26 if (a->used == 0) {
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27 return 0;
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28 }
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29
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30 /* get number of digits and add that */
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31 r = (a->used - 1) * DIGIT_BIT;
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32
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33 /* take the last digit and count the bits in it */
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34 q = a->dp[a->used - 1];
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35 while (q > ((mp_digit) 0)) {
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36 ++r;
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37 q >>= ((mp_digit) 1);
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38 }
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39 return r;
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40 }
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41 #endif