1 files changed, 74 insertions, 0 deletions
diff --git a/libtommath/bn_mp_mul_d.c b/libtommath/bn_mp_mul_d.c
new file mode 100644
index 0000000..f936361
--- /dev/null
+++ b/libtommath/bn_mp_mul_d.c
@@ -0,0 +1,74 @@
+#include <tommath.h>
+#ifdef BN_MP_MUL_D_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, tomstdenis@iahu.ca, http://math.libtomcrypt.org
+ */
+
+/* multiply by a digit */
+int
+mp_mul_d (mp_int * a, mp_digit b, mp_int * c)
+{
+  mp_digit u, *tmpa, *tmpc;
+  mp_word  r;
+  int      ix, res, olduse;
+
+  /* make sure c is big enough to hold a*b */
+  if (c->alloc < a->used + 1) {
+    if ((res = mp_grow (c, a->used + 1)) != MP_OKAY) {
+      return res;
+    }
+  }
+
+  /* get the original destinations used count */
+  olduse = c->used;
+
+  /* set the sign */
+  c->sign = a->sign;
+
+  /* alias for a->dp [source] */
+  tmpa = a->dp;
+
+  /* alias for c->dp [dest] */
+  tmpc = c->dp;
+
+  /* zero carry */
+  u = 0;
+
+  /* compute columns */
+  for (ix = 0; ix < a->used; ix++) {
+    /* compute product and carry sum for this term */
+    r       = ((mp_word) u) + ((mp_word)*tmpa++) * ((mp_word)b);
+
+    /* mask off higher bits to get a single digit */
+    *tmpc++ = (mp_digit) (r & ((mp_word) MP_MASK));
+
+    /* send carry into next iteration */
+    u       = (mp_digit) (r >> ((mp_word) DIGIT_BIT));
+  }
+
+  /* store final carry [if any] */
+  *tmpc++ = u;
+
+  /* now zero digits above the top */
+  while (ix++ < olduse) {
+     *tmpc++ = 0;
+  }
+
+  /* set used count */
+  c->used = a->used + 1;
+  mp_clamp(c);
+
+  return MP_OKAY;
+}
+#endif