kc3-lang/libtommath/bn_mp_mod_2d.c

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• Hash : e45f75fd
  Author :
  Date : 2019-04-13T08:46:57
  

  deprecate DIGIT_BIT, use MP_DIGIT_BIT

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• bn_mp_mod_2d.c

• #include "tommath_private.h"
  #ifdef BN_MP_MOD_2D_C
  /* LibTomMath, multiple-precision integer library -- Tom St Denis */
  /* SPDX-License-Identifier: Unlicense */
  
  /* calc a value mod 2**b */
  int mp_mod_2d(const mp_int *a, int b, mp_int *c)
  {
     int     x, res;
  
     /* if b is <= 0 then zero the int */
     if (b <= 0) {
        mp_zero(c);
        return MP_OKAY;
     }
  
     /* if the modulus is larger than the value than return */
     if (b >= (a->used * MP_DIGIT_BIT)) {
        res = mp_copy(a, c);
        return res;
     }
  
     /* copy */
     if ((res = mp_copy(a, c)) != MP_OKAY) {
        return res;
     }
  
     /* zero digits above the last digit of the modulus */
     for (x = (b / MP_DIGIT_BIT) + (((b % MP_DIGIT_BIT) == 0) ? 0 : 1); x < c->used; x++) {
        c->dp[x] = 0;
     }
     /* clear the digit that is not completely outside/inside the modulus */
     c->dp[b / MP_DIGIT_BIT] &=
        ((mp_digit)1 << (mp_digit)(b % MP_DIGIT_BIT)) - (mp_digit)1;
     mp_clamp(c);
     return MP_OKAY;
  }
  #endif
  

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