1 files changed, 32 insertions, 0 deletions
diff --git a/src/libbiguint/bu_mul.c b/src/libbiguint/bu_mul.c
new file mode 100644
index 0000000..184d652
--- /dev/null
+++ b/src/libbiguint/bu_mul.c
@@ -0,0 +1,32 @@
+/* ISC license. */
+
+#include <skalibs/uint32.h>
+#include <skalibs/uint64.h>
+#include <skalibs/biguint.h>
+
+ /* No Karatsuba. Keep it simple, stupid. */
+
+int bu_mul (uint32 *x, unsigned int xn, uint32 const *a, unsigned int an, uint32 const *b, unsigned int bn)
+{
+  unsigned int alen = bu_len(a, an) ;
+  unsigned int blen = bu_len(b, bn) ;
+  uint32 c[alen + blen] ;
+  register unsigned int i = 0 ;
+  bu_zero(c, alen + blen) ;
+  for (; i < alen ; i++)
+  {
+    register uint32 carry = 0 ;
+    register unsigned int j = 0 ;
+    for (; j < blen ; j++)
+    {
+      register uint64 t = a[i] ;
+      t *= b[j] ;
+      t += c[i+j] ;
+      t += carry ;
+      c[i+j] = (uint32)t ;
+      carry = (uint32)(t >> 32) ;
+    }
+    c[i+j] += carry ;
+  }
+  return bu_copy(x, xn, c, alen+blen) ;
+}