diff options
Diffstat (limited to 'libtommath/bn_mp_n_root_ex.c')
| -rw-r--r-- | libtommath/bn_mp_n_root_ex.c | 185 |
1 files changed, 94 insertions, 91 deletions
diff --git a/libtommath/bn_mp_n_root_ex.c b/libtommath/bn_mp_n_root_ex.c index 079b4f3..9546745 100644 --- a/libtommath/bn_mp_n_root_ex.c +++ b/libtommath/bn_mp_n_root_ex.c @@ -25,105 +25,108 @@ * each step involves a fair bit. This is not meant to * find huge roots [square and cube, etc]. */ -int mp_n_root_ex (mp_int * a, mp_digit b, mp_int * c, int fast) +int mp_n_root_ex(mp_int *a, mp_digit b, mp_int *c, int fast) { - mp_int t1, t2, t3; - int res, neg; - - /* input must be positive if b is even */ - if (((b & 1) == 0) && (a->sign == MP_NEG)) { - return MP_VAL; - } - - if ((res = mp_init (&t1)) != MP_OKAY) { - return res; - } - - if ((res = mp_init (&t2)) != MP_OKAY) { - goto LBL_T1; - } - - if ((res = mp_init (&t3)) != MP_OKAY) { - goto LBL_T2; - } - - /* if a is negative fudge the sign but keep track */ - neg = a->sign; - a->sign = MP_ZPOS; - - /* t2 = 2 */ - mp_set (&t2, 2); - - do { - /* t1 = t2 */ - if ((res = mp_copy (&t2, &t1)) != MP_OKAY) { - goto LBL_T3; - } - - /* t2 = t1 - ((t1**b - a) / (b * t1**(b-1))) */ - - /* t3 = t1**(b-1) */ - if ((res = mp_expt_d_ex (&t1, b - 1, &t3, fast)) != MP_OKAY) { - goto LBL_T3; - } - - /* numerator */ - /* t2 = t1**b */ - if ((res = mp_mul (&t3, &t1, &t2)) != MP_OKAY) { - goto LBL_T3; - } - - /* t2 = t1**b - a */ - if ((res = mp_sub (&t2, a, &t2)) != MP_OKAY) { - goto LBL_T3; - } - - /* denominator */ - /* t3 = t1**(b-1) * b */ - if ((res = mp_mul_d (&t3, b, &t3)) != MP_OKAY) { - goto LBL_T3; - } - - /* t3 = (t1**b - a)/(b * t1**(b-1)) */ - if ((res = mp_div (&t2, &t3, &t3, NULL)) != MP_OKAY) { - goto LBL_T3; - } - - if ((res = mp_sub (&t1, &t3, &t2)) != MP_OKAY) { - goto LBL_T3; - } - } while (mp_cmp (&t1, &t2) != MP_EQ); - - /* result can be off by a few so check */ - for (;;) { - if ((res = mp_expt_d_ex (&t1, b, &t2, fast)) != MP_OKAY) { - goto LBL_T3; - } - - if (mp_cmp (&t2, a) == MP_GT) { - if ((res = mp_sub_d (&t1, 1, &t1)) != MP_OKAY) { + mp_int t1, t2, t3; + int res, neg; + + /* input must be positive if b is even */ + if (((b & 1) == 0) && (a->sign == MP_NEG)) { + return MP_VAL; + } + + if ((res = mp_init(&t1)) != MP_OKAY) { + return res; + } + + if ((res = mp_init(&t2)) != MP_OKAY) { + goto LBL_T1; + } + + if ((res = mp_init(&t3)) != MP_OKAY) { + goto LBL_T2; + } + + /* if a is negative fudge the sign but keep track */ + neg = a->sign; + a->sign = MP_ZPOS; + + /* t2 = 2 */ + mp_set(&t2, 2); + + do { + /* t1 = t2 */ + if ((res = mp_copy(&t2, &t1)) != MP_OKAY) { + goto LBL_T3; + } + + /* t2 = t1 - ((t1**b - a) / (b * t1**(b-1))) */ + + /* t3 = t1**(b-1) */ + if ((res = mp_expt_d_ex(&t1, b - 1, &t3, fast)) != MP_OKAY) { + goto LBL_T3; + } + + /* numerator */ + /* t2 = t1**b */ + if ((res = mp_mul(&t3, &t1, &t2)) != MP_OKAY) { goto LBL_T3; } - } else { - break; - } - } - /* reset the sign of a first */ - a->sign = neg; + /* t2 = t1**b - a */ + if ((res = mp_sub(&t2, a, &t2)) != MP_OKAY) { + goto LBL_T3; + } + + /* denominator */ + /* t3 = t1**(b-1) * b */ + if ((res = mp_mul_d(&t3, b, &t3)) != MP_OKAY) { + goto LBL_T3; + } + + /* t3 = (t1**b - a)/(b * t1**(b-1)) */ + if ((res = mp_div(&t2, &t3, &t3, NULL)) != MP_OKAY) { + goto LBL_T3; + } + + if ((res = mp_sub(&t1, &t3, &t2)) != MP_OKAY) { + goto LBL_T3; + } + } while (mp_cmp(&t1, &t2) != MP_EQ); + + /* result can be off by a few so check */ + for (;;) { + if ((res = mp_expt_d_ex(&t1, b, &t2, fast)) != MP_OKAY) { + goto LBL_T3; + } + + if (mp_cmp(&t2, a) == MP_GT) { + if ((res = mp_sub_d(&t1, 1, &t1)) != MP_OKAY) { + goto LBL_T3; + } + } else { + break; + } + } + + /* reset the sign of a first */ + a->sign = neg; - /* set the result */ - mp_exch (&t1, c); + /* set the result */ + mp_exch(&t1, c); - /* set the sign of the result */ - c->sign = neg; + /* set the sign of the result */ + c->sign = neg; - res = MP_OKAY; + res = MP_OKAY; -LBL_T3:mp_clear (&t3); -LBL_T2:mp_clear (&t2); -LBL_T1:mp_clear (&t1); - return res; +LBL_T3: + mp_clear(&t3); +LBL_T2: + mp_clear(&t2); +LBL_T1: + mp_clear(&t1); + return res; } #endif |