mp_signed_rsh.c

   1 #include "tommath_private.h"
   2 #ifdef MP_SIGNED_RSH_C
   3 /* LibTomMath, multiple-precision integer library -- Tom St Denis */
   4 /* SPDX-License-Identifier: Unlicense */
   5
   6 /* shift right by a certain bit count with sign extension */
   7 mp_err mp_signed_rsh(const mp_int *a, int b, mp_int *c)
   8 {
   9    mp_err err;
  10    if (!mp_isneg(a)) {
  11       return mp_div_2d(a, b, c, NULL);
  12    }
  13
  14    if ((err = mp_add_d(a, 1uL, c)) != MP_OKAY) {
  15       return err;
  16    }
  17
  18    err = mp_div_2d(c, b, c, NULL);
  19    return (err == MP_OKAY) ? mp_sub_d(c, 1uL, c) : err;
  20 }
  21 #endif