Mercurial > dropbear
comparison bn_mp_count_bits.c @ 282:91fbc376f010 libtommath-orig libtommath-0.35
Import of libtommath 0.35
From ltm-0.35.tar.bz2 SHA1 of 3f193dbae9351e92d02530994fa18236f7fde01c
author | Matt Johnston <matt@ucc.asn.au> |
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date | Wed, 08 Mar 2006 13:16:18 +0000 |
parents | |
children | 97db060d0ef5 |
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-1:000000000000 | 282:91fbc376f010 |
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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 |