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comparison libtommath/bn_mp_count_bits.c @ 285:1b9e69c058d2

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propagate from branch 'au.asn.ucc.matt.ltc.dropbear' (head 20dccfc09627970a312d77fb41dc2970b62689c3) to branch 'au.asn.ucc.matt.dropbear' (head fdf4a7a3b97ae5046139915de7e40399cceb2c01)
author Matt Johnston <matt@ucc.asn.au>
date Wed, 08 Mar 2006 13:23:58 +0000
parents eed26cff980b
children 5ff8218bcee9
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281:997e6f7dc01e 285:1b9e69c058d2
1 #include <tommath.h>
2 #ifdef BN_MP_COUNT_BITS_C
3 /* LibTomMath, multiple-precision integer library -- Tom St Denis
4 *
5 * LibTomMath is a library that provides multiple-precision
6 * integer arithmetic as well as number theoretic functionality.
7 *
8 * The library was designed directly after the MPI library by
9 * Michael Fromberger but has been written from scratch with
10 * additional optimizations in place.
11 *
12 * The library is free for all purposes without any express
13 * guarantee it works.
14 *
15 * Tom St Denis, [email protected], http://math.libtomcrypt.org
16 */
17
18 /* returns the number of bits in an int */
19 int
20 mp_count_bits (mp_int * a)
21 {
22 int r;
23 mp_digit q;
24
25 /* shortcut */
26 if (a->used == 0) {
27 return 0;
28 }
29
30 /* get number of digits and add that */
31 r = (a->used - 1) * DIGIT_BIT;
32
33 /* take the last digit and count the bits in it */
34 q = a->dp[a->used - 1];
35 while (q > ((mp_digit) 0)) {
36 ++r;
37 q >>= ((mp_digit) 1);
38 }
39 return r;
40 }
41 #endif