lib/hcrypto/libtommath/bn_mp_lcm.c

   1 #include "tommath_private.h"
   2 #ifdef BN_MP_LCM_C
   3 /* LibTomMath, multiple-precision integer library -- Tom St Denis */
   4 /* SPDX-License-Identifier: Unlicense */
   5
   6 /* computes least common multiple as |a*b|/(a, b) */
   7 mp_err mp_lcm(const mp_int *a, const mp_int *b, mp_int *c)
   8 {
   9    mp_err  err;
  10    mp_int  t1, t2;
  11
  12
  13    if ((err = mp_init_multi(&t1, &t2, NULL)) != MP_OKAY) {
  14       return err;
  15    }
  16
  17    /* t1 = get the GCD of the two inputs */
  18    if ((err = mp_gcd(a, b, &t1)) != MP_OKAY) {
  19       goto LBL_T;
  20    }
  21
  22    /* divide the smallest by the GCD */
  23    if (mp_cmp_mag(a, b) == MP_LT) {
  24       /* store quotient in t2 such that t2 * b is the LCM */
  25       if ((err = mp_div(a, &t1, &t2, NULL)) != MP_OKAY) {
  26          goto LBL_T;
  27       }
  28       err = mp_mul(b, &t2, c);
  29    } else {
  30       /* store quotient in t2 such that t2 * a is the LCM */
  31       if ((err = mp_div(b, &t1, &t2, NULL)) != MP_OKAY) {
  32          goto LBL_T;
  33       }
  34       err = mp_mul(a, &t2, c);
  35    }
  36
  37    /* fix the sign to positive */
  38    c->sign = MP_ZPOS;
  39
  40 LBL_T:
  41    mp_clear_multi(&t1, &t2, NULL);
  42    return err;
  43 }
  44 #endif