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-rw-r--r--libtommath/bn_mp_n_root.c118
1 files changed, 10 insertions, 108 deletions
diff --git a/libtommath/bn_mp_n_root.c b/libtommath/bn_mp_n_root.c
index b2700a8..a14ee67 100644
--- a/libtommath/bn_mp_n_root.c
+++ b/libtommath/bn_mp_n_root.c
@@ -1,4 +1,4 @@
-#include <tommath.h>
+#include <tommath_private.h>
#ifdef BN_MP_N_ROOT_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis
*
@@ -12,117 +12,19 @@
* The library is free for all purposes without any express
* guarantee it works.
*
- * Tom St Denis, tomstdenis@gmail.com, http://math.libtomcrypt.com
+ * Tom St Denis, tstdenis82@gmail.com, http://libtom.org
*/
-/* find the n'th root of an integer
- *
- * Result found such that (c)**b <= a and (c+1)**b > a
- *
- * This algorithm uses Newton's approximation
- * x[i+1] = x[i] - f(x[i])/f'(x[i])
- * which will find the root in log(N) time where
- * each step involves a fair bit. This is not meant to
- * find huge roots [square and cube, etc].
+/* wrapper function for mp_n_root_ex()
+ * computes c = (a)**(1/b) such that (c)**b <= a and (c+1)**b > a
*/
int mp_n_root (mp_int * a, mp_digit b, mp_int * c)
{
- 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 (&t1, b - 1, &t3)) != 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 (&t1, b, &t2)) != 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 sign of the result */
- c->sign = neg;
-
- res = MP_OKAY;
-
-LBL_T3:mp_clear (&t3);
-LBL_T2:mp_clear (&t2);
-LBL_T1:mp_clear (&t1);
- return res;
+ return mp_n_root_ex(a, b, c, 0);
}
+
#endif
+
+/* $Source$ */
+/* $Revision$ */
+/* $Date$ */