Import code from previous AssetBuilder version

thirdparty/libtommath/bn_mp_gcd.c

@@ -0,0 +1,104 @@
+#include "tommath_private.h"
+#ifdef BN_MP_GCD_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.
+ *
+ * SPDX-License-Identifier: Unlicense
+ */
+
+/* Greatest Common Divisor using the binary method */
+int mp_gcd(const mp_int *a, const mp_int *b, mp_int *c)
+{
+   mp_int  u, v;
+   int     k, u_lsb, v_lsb, res;
+
+   /* either zero than gcd is the largest */
+   if (mp_iszero(a) == MP_YES) {
+      return mp_abs(b, c);
+   }
+   if (mp_iszero(b) == MP_YES) {
+      return mp_abs(a, c);
+   }
+
+   /* get copies of a and b we can modify */
+   if ((res = mp_init_copy(&u, a)) != MP_OKAY) {
+      return res;
+   }
+
+   if ((res = mp_init_copy(&v, b)) != MP_OKAY) {
+      goto LBL_U;
+   }
+
+   /* must be positive for the remainder of the algorithm */
+   u.sign = v.sign = MP_ZPOS;
+
+   /* B1.  Find the common power of two for u and v */
+   u_lsb = mp_cnt_lsb(&u);
+   v_lsb = mp_cnt_lsb(&v);
+   k     = MIN(u_lsb, v_lsb);
+
+   if (k > 0) {
+      /* divide the power of two out */
+      if ((res = mp_div_2d(&u, k, &u, NULL)) != MP_OKAY) {
+         goto LBL_V;
+      }
+
+      if ((res = mp_div_2d(&v, k, &v, NULL)) != MP_OKAY) {
+         goto LBL_V;
+      }
+   }
+
+   /* divide any remaining factors of two out */
+   if (u_lsb != k) {
+      if ((res = mp_div_2d(&u, u_lsb - k, &u, NULL)) != MP_OKAY) {
+         goto LBL_V;
+      }
+   }
+
+   if (v_lsb != k) {
+      if ((res = mp_div_2d(&v, v_lsb - k, &v, NULL)) != MP_OKAY) {
+         goto LBL_V;
+      }
+   }
+
+   while (mp_iszero(&v) == MP_NO) {
+      /* make sure v is the largest */
+      if (mp_cmp_mag(&u, &v) == MP_GT) {
+         /* swap u and v to make sure v is >= u */
+         mp_exch(&u, &v);
+      }
+
+      /* subtract smallest from largest */
+      if ((res = s_mp_sub(&v, &u, &v)) != MP_OKAY) {
+         goto LBL_V;
+      }
+
+      /* Divide out all factors of two */
+      if ((res = mp_div_2d(&v, mp_cnt_lsb(&v), &v, NULL)) != MP_OKAY) {
+         goto LBL_V;
+      }
+   }
+
+   /* multiply by 2**k which we divided out at the beginning */
+   if ((res = mp_mul_2d(&u, k, c)) != MP_OKAY) {
+      goto LBL_V;
+   }
+   c->sign = MP_ZPOS;
+   res = MP_OKAY;
+LBL_V:
+   mp_clear(&u);
+LBL_U:
+   mp_clear(&v);
+   return res;
+}
+#endif
+
+/* ref:         HEAD -> master, tag: v1.1.0 */
+/* git commit:  08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */
+/* commit time: 2019-01-28 20:32:32 +0100 */