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authorLaurent Bercot <ska-skaware@skarnet.org>2014-09-18 18:55:44 +0000
committerLaurent Bercot <ska-skaware@skarnet.org>2014-09-18 18:55:44 +0000
commit3534b428629be185e096be99e3bd5fdfe32d5544 (patch)
tree210ef3198ed66bc7f7b7bf6a85e4579f455e5a36 /src/libbiguint/bu_mul.c
downloadskalibs-3534b428629be185e096be99e3bd5fdfe32d5544.tar.xz
initial commit with rc for skalibs-2.0.0.0
Diffstat (limited to 'src/libbiguint/bu_mul.c')
-rw-r--r--src/libbiguint/bu_mul.c32
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) ;
+}