release/src/router/dropbear/libtommath/bn_mp_lcm.c

   1 #include <tommath.h>
   2 #ifdef BN_MP_LCM_C
   3 /* LibTomMath, multiple-precision integer library -- Tom St Denis
   4  *
   5  * LibTomMath is a library that provides multiple-precision
   6  * integer arithmetic as well as number theoretic functionality.
   7  *
   8  * The library was designed directly after the MPI library by
   9  * Michael Fromberger but has been written from scratch with
  10  * additional optimizations in place.
  11  *
  12  * The library is free for all purposes without any express
  13  * guarantee it works.
  14  *
  15  * Tom St Denis, tomstdenis@gmail.com, http://math.libtomcrypt.com
  16  */
  17
  18 /* computes least common multiple as |a*b|/(a, b) */
  19 int mp_lcm (mp_int * a, mp_int * b, mp_int * c)
  20 {
  21   int     res;
  22   mp_int  t1, t2;
  23
  24
  25   if ((res = mp_init_multi (&t1, &t2, NULL)) != MP_OKAY) {
  26     return res;
  27   }
  28
  29   /* t1 = get the GCD of the two inputs */
  30   if ((res = mp_gcd (a, b, &t1)) != MP_OKAY) {
  31     goto LBL_T;
  32   }
  33
  34   /* divide the smallest by the GCD */
  35   if (mp_cmp_mag(a, b) == MP_LT) {
  36      /* store quotient in t2 such that t2 * b is the LCM */
  37      if ((res = mp_div(a, &t1, &t2, NULL)) != MP_OKAY) {
  38         goto LBL_T;
  39      }
  40      res = mp_mul(b, &t2, c);
  41   } else {
  42      /* store quotient in t2 such that t2 * a is the LCM */
  43      if ((res = mp_div(b, &t1, &t2, NULL)) != MP_OKAY) {
  44         goto LBL_T;
  45      }
  46      res = mp_mul(a, &t2, c);
  47   }
  48
  49   /* fix the sign to positive */
  50   c->sign = MP_ZPOS;
  51
  52 LBL_T:
  53   mp_clear_multi (&t1, &t2, NULL);
  54   return res;
  55 }
  56 #endif
  57
  58 /* $Source: /cvs/libtom/libtommath/bn_mp_lcm.c,v $ */
  59 /* $Revision: 1.3 $ */
  60 /* $Date: 2006/03/31 14:18:44 $ */