Mercurial > dropbear
view libtommath/bn_mp_count_bits.c @ 1664:871484eac157
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author | Matt Johnston <matt@ucc.asn.au> |
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date | Sat, 14 Mar 2020 23:33:30 +0800 |
parents | f52919ffd3b1 |
children | 1051e4eea25a |
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#include "tommath_private.h" #ifdef BN_MP_COUNT_BITS_C /* LibTomMath, multiple-precision integer library -- Tom St Denis * * LibTomMath is a library that provides multiple-precision * integer arithmetic as well as number theoretic functionality. * * The library was designed directly after the MPI library by * Michael Fromberger but has been written from scratch with * additional optimizations in place. * * SPDX-License-Identifier: Unlicense */ /* returns the number of bits in an int */ int mp_count_bits(const mp_int *a) { int r; mp_digit q; /* shortcut */ if (a->used == 0) { return 0; } /* get number of digits and add that */ r = (a->used - 1) * DIGIT_BIT; /* take the last digit and count the bits in it */ q = a->dp[a->used - 1]; while (q > (mp_digit)0) { ++r; q >>= (mp_digit)1; } return r; } #endif /* ref: HEAD -> master, tag: v1.1.0 */ /* git commit: 08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */ /* commit time: 2019-01-28 20:32:32 +0100 */