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kc3-lang/libtommath/bn_mp_prime_is_divisible.c

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  • Author : Tom St Denis
    Date : 2003-07-02 15:39:39
    Hash : 4c1d3f08
    Message : added libtommath-0.22

  • bn_mp_prime_is_divisible.c 
  • /* LibTomMath, multiple-precision integer library -- Tom St Denis
 *
 * LibTomMath is library that provides for multiple-precision
 * integer arithmetic as well as number theoretic functionality.
 *
 * The library is designed directly after the MPI library by
 * Michael Fromberger but has been written from scratch with
 * additional optimizations in place.
 *
 * The library is free for all purposes without any express
 * guarantee it works.
 *
 * Tom St Denis, tomstdenis@iahu.ca, http://math.libtomcrypt.org
 */
#include <tommath.h>

/* determines if an integers is divisible by one 
 * of the first PRIME_SIZE primes or not
 *
 * sets result to 0 if not, 1 if yes
 */
int
mp_prime_is_divisible (mp_int * a, int *result)
{
  int     err, ix;
  mp_digit res;

  /* default to not */
  *result = 0;

  for (ix = 0; ix < PRIME_SIZE; ix++) {
    /* what is a mod __prime_tab[ix] */
    if ((err = mp_mod_d (a, __prime_tab[ix], &res)) != MP_OKAY) {
      return err;
    }

    /* is the residue zero? */
    if (res == 0) {
      *result = 1;
      return MP_OKAY;
    }
  }

  return MP_OKAY;
}