tommath/bn_mp_count_bits.c

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#include <tommath_private.h>
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#ifdef BN_MP_COUNT_BITS_C
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/* LibTomMath, multiple-precision integer library -- Tom St Denis
*
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* LibTomMath is a library that provides multiple-precision
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* integer arithmetic as well as number theoretic functionality.
*
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* The library was designed directly after the MPI library by
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* 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.
*
* Tom St Denis, tstdenis82@gmail.com, http://libtom.org
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*/
/* returns the number of bits in an int */
int mp_count_bits(const mp_int *a)
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{
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int r;
mp_digit q;
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/* shortcut */
if (a->used == 0) {
return 0;
}
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/* get number of digits and add that */
r = (a->used - 1) * DIGIT_BIT;
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/* take the last digit and count the bits in it */
q = a->dp[a->used - 1];
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while (q > (mp_digit)0) {
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++r;
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q >>= (mp_digit)1;
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}
return r;
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}
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#endif
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/* ref: $Format:%D$ */
/* git commit: $Format:%H$ */
/* commit time: $Format:%ai$ */