tommath/bn_mp_count_bits.c

43 lines
1023 B
C
Raw Normal View History

#include "tommath_private.h"
2004-10-29 18:07:18 -04:00
#ifdef BN_MP_COUNT_BITS_C
2003-02-28 11:08:34 -05:00
/* LibTomMath, multiple-precision integer library -- Tom St Denis
*
2003-08-04 21:24:44 -04:00
* LibTomMath is a library that provides multiple-precision
2003-02-28 11:08:34 -05:00
* integer arithmetic as well as number theoretic functionality.
*
2003-08-04 21:24:44 -04:00
* The library was designed directly after the MPI library by
2003-02-28 11:08:34 -05:00
* Michael Fromberger but has been written from scratch with
* additional optimizations in place.
*
* The library is free for all purposes without any express
* guarantee it works.
*/
/* returns the number of bits in an int */
int mp_count_bits(const mp_int *a)
2003-02-28 11:08:34 -05:00
{
2017-08-29 16:23:48 -04:00
int r;
mp_digit q;
2003-02-28 11:08:34 -05:00
2017-08-29 16:23:48 -04:00
/* shortcut */
if (a->used == 0) {
return 0;
}
2003-02-28 11:08:34 -05:00
2017-08-29 16:23:48 -04:00
/* get number of digits and add that */
r = (a->used - 1) * DIGIT_BIT;
2017-08-29 23:51:11 -04:00
2017-08-29 16:23:48 -04:00
/* take the last digit and count the bits in it */
q = a->dp[a->used - 1];
2017-10-15 13:58:35 -04:00
while (q > (mp_digit)0) {
2017-08-29 16:23:48 -04:00
++r;
2017-10-15 13:58:35 -04:00
q >>= (mp_digit)1;
2017-08-29 16:23:48 -04:00
}
return r;
2003-02-28 11:08:34 -05:00
}
2004-10-29 18:07:18 -04:00
#endif
2005-08-01 12:37:28 -04:00
2017-08-28 10:27:26 -04:00
/* ref: $Format:%D$ */
/* git commit: $Format:%H$ */
/* commit time: $Format:%ai$ */