Mercurial > dropbear
diff libtommath/bn_mp_lcm.c @ 284:eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
to branch 'au.asn.ucc.matt.dropbear' (head fff0894a0399405a9410ea1c6d118f342cf2aa64)
author | Matt Johnston <matt@ucc.asn.au> |
---|---|
date | Wed, 08 Mar 2006 13:23:49 +0000 |
parents | |
children | 5ff8218bcee9 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/libtommath/bn_mp_lcm.c Wed Mar 08 13:23:49 2006 +0000 @@ -0,0 +1,56 @@ +#include <tommath.h> +#ifdef BN_MP_LCM_C +/* LibTomMath, multiple-precision integer library -- Tom St Denis + * + * LibTomMath is a library that provides multiple-precision + * integer arithmetic as well as number theoretic functionality. + * + * The library was 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, [email protected], http://math.libtomcrypt.org + */ + +/* computes least common multiple as |a*b|/(a, b) */ +int mp_lcm (mp_int * a, mp_int * b, mp_int * c) +{ + int res; + mp_int t1, t2; + + + if ((res = mp_init_multi (&t1, &t2, NULL)) != MP_OKAY) { + return res; + } + + /* t1 = get the GCD of the two inputs */ + if ((res = mp_gcd (a, b, &t1)) != MP_OKAY) { + goto LBL_T; + } + + /* divide the smallest by the GCD */ + if (mp_cmp_mag(a, b) == MP_LT) { + /* store quotient in t2 such that t2 * b is the LCM */ + if ((res = mp_div(a, &t1, &t2, NULL)) != MP_OKAY) { + goto LBL_T; + } + res = mp_mul(b, &t2, c); + } else { + /* store quotient in t2 such that t2 * a is the LCM */ + if ((res = mp_div(b, &t1, &t2, NULL)) != MP_OKAY) { + goto LBL_T; + } + res = mp_mul(a, &t2, c); + } + + /* fix the sign to positive */ + c->sign = MP_ZPOS; + +LBL_T: + mp_clear_multi (&t1, &t2, NULL); + return res; +} +#endif