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, tomstdenis (at) gmail.com, http://math.libtomcrypt.com 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 42 43 /* $Source: /cvs/libtom/libtommath/bn_mp_count_bits.c,v $ */ 44 /* $Revision: 1.3 $ */ 45 /* $Date: 2006/03/31 14:18:44 $ */ 46
