bn_mp_2expt.c

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Author : Daniel Mendler
Date : 2019-05-13 00:22:18
Hash : 4534056c
Message : use enums mp_err, mp_ord, mp_bool, mp_sign * MP_USE_ENUMS enables enums * Wc++-compat catches some implicit conversions if MP_USE_ENUMS is defined * 100% backwards compatible API/ABI if MP_USE_ENUMS is not defined

bn_mp_2expt.c

#include "tommath_private.h"
#ifdef BN_MP_2EXPT_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis */
/* SPDX-License-Identifier: Unlicense */

/* computes a = 2**b
 *
 * Simple algorithm which zeroes the int, grows it then just sets one bit
 * as required.
 */
mp_err mp_2expt(mp_int *a, int b)
{
   mp_err    res;

   /* zero a as per default */
   mp_zero(a);

   /* grow a to accomodate the single bit */
   if ((res = mp_grow(a, (b / MP_DIGIT_BIT) + 1)) != MP_OKAY) {
      return res;
   }

   /* set the used count of where the bit will go */
   a->used = (b / MP_DIGIT_BIT) + 1;

   /* put the single bit in its place */
   a->dp[b / MP_DIGIT_BIT] = (mp_digit)1 << (mp_digit)(b % MP_DIGIT_BIT);

   return MP_OKAY;
}
#endif

kc3-lang/libtommath/bn_mp_2expt.c

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