diff 3rdparty/libtommath/bn_mp_mul.c @ 0:2cf249471370

convert mercurial for git
author Takahiro SHIMIZU <anatofuz@cr.ie.u-ryukyu.ac.jp>
date Tue, 08 May 2018 16:09:12 +0900
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--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/3rdparty/libtommath/bn_mp_mul.c	Tue May 08 16:09:12 2018 +0900
@@ -0,0 +1,67 @@
+#include <tommath_private.h>
+#ifdef BN_MP_MUL_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, tstdenis82@gmail.com, http://libtom.org
+ */
+
+/* high level multiplication (handles sign) */
+int mp_mul (mp_int * a, mp_int * b, mp_int * c)
+{
+  int     res, neg;
+  neg = (a->sign == b->sign) ? MP_ZPOS : MP_NEG;
+
+  /* use Toom-Cook? */
+#ifdef BN_MP_TOOM_MUL_C
+  if (MIN (a->used, b->used) >= TOOM_MUL_CUTOFF) {
+    res = mp_toom_mul(a, b, c);
+  } else 
+#endif
+#ifdef BN_MP_KARATSUBA_MUL_C
+  /* use Karatsuba? */
+  if (MIN (a->used, b->used) >= KARATSUBA_MUL_CUTOFF) {
+    res = mp_karatsuba_mul (a, b, c);
+  } else 
+#endif
+  {
+    /* can we use the fast multiplier?
+     *
+     * The fast multiplier can be used if the output will 
+     * have less than MP_WARRAY digits and the number of 
+     * digits won't affect carry propagation
+     */
+    int     digs = a->used + b->used + 1;
+
+#ifdef BN_FAST_S_MP_MUL_DIGS_C
+    if ((digs < MP_WARRAY) &&
+        (MIN(a->used, b->used) <= 
+         (1 << ((CHAR_BIT * sizeof(mp_word)) - (2 * DIGIT_BIT))))) {
+      res = fast_s_mp_mul_digs (a, b, c, digs);
+    } else 
+#endif
+    {
+#ifdef BN_S_MP_MUL_DIGS_C
+      res = s_mp_mul (a, b, c); /* uses s_mp_mul_digs */
+#else
+      res = MP_VAL;
+#endif
+    }
+  }
+  c->sign = (c->used > 0) ? neg : MP_ZPOS;
+  return res;
+}
+#endif
+
+/* $Source$ */
+/* $Revision$ */
+/* $Date$ */