1 /* $NetBSD: bn_mp_count_bits.c,v 1.1.1.2 2014/04/24 12:45:31 pettai Exp $ */ 2 3 #include <tommath.h> 4 #ifdef BN_MP_COUNT_BITS_C 5 /* LibTomMath, multiple-precision integer library -- Tom St Denis 6 * 7 * LibTomMath is a library that provides multiple-precision 8 * integer arithmetic as well as number theoretic functionality. 9 * 10 * The library was designed directly after the MPI library by 11 * Michael Fromberger but has been written from scratch with 12 * additional optimizations in place. 13 * 14 * The library is free for all purposes without any express 15 * guarantee it works. 16 * 17 * Tom St Denis, tomstdenis@gmail.com, http://libtom.org 18 */ 19 20 /* returns the number of bits in an int */ 21 int mp_count_bits(mp_int * a)22mp_count_bits (mp_int * a) 23 { 24 int r; 25 mp_digit q; 26 27 /* shortcut */ 28 if (a->used == 0) { 29 return 0; 30 } 31 32 /* get number of digits and add that */ 33 r = (a->used - 1) * DIGIT_BIT; 34 35 /* take the last digit and count the bits in it */ 36 q = a->dp[a->used - 1]; 37 while (q > ((mp_digit) 0)) { 38 ++r; 39 q >>= ((mp_digit) 1); 40 } 41 return r; 42 } 43 #endif 44 45 /* Source: /cvs/libtom/libtommath/bn_mp_count_bits.c,v */ 46 /* Revision: 1.4 */ 47 /* Date: 2006/12/28 01:25:13 */ 48