1 files changed, 89 insertions, 0 deletions
diff --git a/libtommath/bn_mp_tc_xor.c b/libtommath/bn_mp_tc_xor.c
new file mode 100644
index 0000000..50fb12d
--- /dev/null
+++ b/libtommath/bn_mp_tc_xor.c
@@ -0,0 +1,89 @@
+#include "tommath_private.h"
+#ifdef BN_MP_TC_XOR_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.
+ */
+
+/* two complement xor */
+int mp_tc_xor(const mp_int *a, const mp_int *b, mp_int *c)
+{
+   int res = MP_OKAY, bits;
+   int as = mp_isneg(a), bs = mp_isneg(b);
+   mp_int *mx = NULL, _mx, acpy, bcpy;
+
+   if ((as != MP_NO) || (bs != MP_NO)) {
+      bits = MAX(mp_count_bits(a), mp_count_bits(b));
+      res = mp_init_set_int(&_mx, 1uL);
+      if (res != MP_OKAY) {
+         goto end;
+      }
+
+      mx = &_mx;
+      res = mp_mul_2d(mx, bits + 1, mx);
+      if (res != MP_OKAY) {
+         goto end;
+      }
+
+      if (as != MP_NO) {
+         res = mp_init(&acpy);
+         if (res != MP_OKAY) {
+            goto end;
+         }
+
+         res = mp_add(mx, a, &acpy);
+         if (res != MP_OKAY) {
+            mp_clear(&acpy);
+            goto end;
+         }
+         a = &acpy;
+      }
+      if (bs != MP_NO) {
+         res = mp_init(&bcpy);
+         if (res != MP_OKAY) {
+            goto end;
+         }
+
+         res = mp_add(mx, b, &bcpy);
+         if (res != MP_OKAY) {
+            mp_clear(&bcpy);
+            goto end;
+         }
+         b = &bcpy;
+      }
+   }
+
+   res = mp_xor(a, b, c);
+
+   if ((as != bs) && (res == MP_OKAY)) {
+      res = mp_sub(c, mx, c);
+   }
+
+end:
+   if (a == &acpy) {
+      mp_clear(&acpy);
+   }
+
+   if (b == &bcpy) {
+      mp_clear(&bcpy);
+   }
+
+   if (mx == &_mx) {
+      mp_clear(mx);
+   }
+
+   return res;
+}
+#endif
+
+/* ref:         $Format:%D$ */
+/* git commit:  $Format:%H$ */
+/* commit time: $Format:%ai$ */