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kc3-lang/libtommath/bn_mp_invmod.c

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  • Author : Daniel Mendler
    Date : 2019-04-08 23:48:39
    Hash : 8c1b296e
    Message : add feature detection macro MP_HAS

  • bn_mp_invmod.c
  • #include "tommath_private.h"
    #ifdef BN_MP_INVMOD_C
    /* LibTomMath, multiple-precision integer library -- Tom St Denis */
    /* SPDX-License-Identifier: Unlicense */
    
    /* hac 14.61, pp608 */
    mp_err mp_invmod(const mp_int *a, const mp_int *b, mp_int *c)
    {
       /* b cannot be negative and has to be >1 */
       if ((b->sign == MP_NEG) || (mp_cmp_d(b, 1uL) != MP_GT)) {
          return MP_VAL;
       }
    
       /* if the modulus is odd we can use a faster routine instead */
       if (MP_HAS(S_MP_INVMOD_FAST) && MP_IS_ODD(b)) {
          return s_mp_invmod_fast(a, b, c);
       }
    
       return MP_HAS(S_MP_INVMOD_SLOW)
              ? s_mp_invmod_slow(a, b, c)
              : MP_VAL;
    }
    #endif