diff src/encauth/ocb/ocb_ntz.c @ 191:1c15b283127b libtomcrypt-orig

Import of libtomcrypt 1.02 with manual path rename rearrangement etc
author Matt Johnston <matt@ucc.asn.au>
date Fri, 06 May 2005 13:23:02 +0000
parents
children 39d5d58461d6
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--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/encauth/ocb/ocb_ntz.c	Fri May 06 13:23:02 2005 +0000
@@ -0,0 +1,38 @@
+/* LibTomCrypt, modular cryptographic library -- Tom St Denis
+ *
+ * LibTomCrypt is a library that provides various cryptographic
+ * algorithms in a highly modular and flexible manner.
+ *
+ * The library is free for all purposes without any express
+ * guarantee it works.
+ *
+ * Tom St Denis, [email protected], http://libtomcrypt.org
+ */
+
+/**
+   @file ocb_ntz.c
+   OCB implementation, internal function, by Tom St Denis
+*/
+
+#include "tomcrypt.h"
+
+#ifdef OCB_MODE
+
+/**
+   Returns the number of leading zero bits [from lsb up]
+   @param x  The 32-bit value to observe
+   @return   The number of bits [from the lsb up] that are zero
+*/
+int ocb_ntz(unsigned long x)
+{
+   int c;
+   x &= 0xFFFFFFFFUL;
+   c = 0;
+   while ((x & 1) == 0) {
+      ++c;
+      x >>= 1;
+   }
+   return c;
+}
+
+#endif