view libtommath/bn_mp_count_bits.c @ 1702:8f93f37c01de

Allow DH to be completely disabled (#97) Reduces binary size by ~2kB by default and by 21kB with no other libtommath functions users, ex. with curve25519 kex and ed25519 key only.
author Vladislav Grishenko <themiron@users.noreply.github.com>
date Thu, 28 May 2020 20:01:48 +0500
parents 1051e4eea25a
children
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#include "tommath_private.h"
#ifdef BN_MP_COUNT_BITS_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis */
/* 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 (MP_IS_ZERO(a)) {
      return 0;
   }

   /* get number of digits and add that */
   r = (a->used - 1) * MP_DIGIT_BIT;

   /* take the last digit and count the bits in it */
   q = a->dp[a->used - 1];
   while (q > 0u) {
      ++r;
      q >>= 1u;
   }
   return r;
}
#endif