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comparison bn_mp_count_bits.c @ 1:22d5cf7d4b1a libtommath

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Renaming branch
author Matt Johnston <matt@ucc.asn.au>
date Mon, 31 May 2004 18:23:46 +0000
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-1:000000000000 1:22d5cf7d4b1a
1 /* LibTomMath, multiple-precision integer library -- Tom St Denis
2 *
3 * LibTomMath is a library that provides multiple-precision
4 * integer arithmetic as well as number theoretic functionality.
5 *
6 * The library was designed directly after the MPI library by
7 * Michael Fromberger but has been written from scratch with
8 * additional optimizations in place.
9 *
10 * The library is free for all purposes without any express
11 * guarantee it works.
12 *
13 * Tom St Denis, [email protected], http://math.libtomcrypt.org
14 */
15 #include <tommath.h>
16
17 /* returns the number of bits in an int */
18 int
19 mp_count_bits (mp_int * a)
20 {
21 int r;
22 mp_digit q;
23
24 /* shortcut */
25 if (a->used == 0) {
26 return 0;
27 }
28
29 /* get number of digits and add that */
30 r = (a->used - 1) * DIGIT_BIT;
31
32 /* take the last digit and count the bits in it */
33 q = a->dp[a->used - 1];
34 while (q > ((mp_digit) 0)) {
35 ++r;
36 q >>= ((mp_digit) 1);
37 }
38 return r;
39 }