Diff: math/mul/fp_mul_2d.c

Revision:

4:cbaf466d717d

Parent:

0:35aa5be3b78d

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/math/mul/fp_mul_2d.c	Tue Jun 10 14:23:09 2014 +0000
@@ -0,0 +1,47 @@
+/* TomsFastMath, a fast ISO C bignum library.
+ * 
+ * This project is meant to fill in where LibTomMath
+ * falls short.  That is speed ;-)
+ *
+ * This project is public domain and free for all purposes.
+ * 
+ * Tom St Denis, tomstdenis@gmail.com
+ */
+#include <tfm.h>
+
+/* c = a * 2**d */
+void fp_mul_2d(fp_int *a, int b, fp_int *c)
+{
+   fp_digit carry, carrytmp, shift;
+   int x;
+
+   /* copy it */
+   fp_copy(a, c);
+
+   /* handle whole digits */
+   if (b >= DIGIT_BIT) {
+      fp_lshd(c, b/DIGIT_BIT);
+   }
+   b %= DIGIT_BIT;
+
+   /* shift the digits */
+   if (b != 0) {
+      carry = 0;   
+      shift = DIGIT_BIT - b;
+      for (x = 0; x < c->used; x++) {
+          carrytmp = c->dp[x] >> shift;
+          c->dp[x] = (c->dp[x] << b) + carry;
+          carry = carrytmp;
+      }
+      /* store last carry if room */
+      if (carry && x < FP_SIZE) {
+         c->dp[c->used++] = carry;
+      }
+   }
+   fp_clamp(c);
+}
+
+
+/* $Source: /cvs/libtom/tomsfastmath/src/mul/fp_mul_2d.c,v $ */
+/* $Revision: 1.1 $ */
+/* $Date: 2006/12/31 21:25:53 $ */