bn_mp_signed_rsh.c

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Author : Daniel Mendler
Date : 2019-05-20 19:11:25
Hash : 1af0de1f
Message : deprecate mp_tc_(and|or|xor) in favor of mp_(and|or|xor) * same behavior for positive numbers * generalisation for negative numbers, treating them as two complement * improve algorithm, iterate once over the digits, manually perform two complement * simplify mp_add_d, mp_sub_d * functions are safe in case of a==c or b==c * renamed mp_tc_div_2d to mp_signed_rsh (signed right shift)

bn_mp_signed_rsh.c

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

/* shift right by a certain bit count with sign extension */
mp_err mp_signed_rsh(const mp_int *a, int b, mp_int *c)
{
   mp_err res;
   if (a->sign == MP_ZPOS) {
      return mp_div_2d(a, b, c, NULL);
   }

   res = mp_add_d(a, 1uL, c);
   if (res != MP_OKAY) {
      return res;
   }

   res = mp_div_2d(c, b, c, NULL);
   return (res == MP_OKAY) ? mp_sub_d(c, 1uL, c) : res;
}
#endif

kc3-lang/libtommath/bn_mp_signed_rsh.c

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