### diff libtommath/bn_mp_lcm.c @ 284:eed26cff980b

author Matt Johnston Wed, 08 Mar 2006 13:23:49 +0000 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```