view libtomcrypt/src/encauth/ocb3/ocb3_int_ntz.c @ 1622:e11ed628708b

- Add adaptive authentication failure delay - Rework monotonic_now/gettime_wrapper and use clock_gettime on more platforms
author Matt Johnston <matt@ucc.asn.au>
date Mon, 05 Nov 2018 23:36:34 +0800
parents 6dba84798cd5
children
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/* 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.
 */

/**
   @file ocb3_int_ntz.c
   OCB implementation, INTERNAL ONLY helper, by Tom St Denis
*/
#include "tomcrypt.h"

#ifdef LTC_OCB3_MODE

/**
   Returns the number of leading zero bits [from lsb up] (internal function)
   @param x  The 32-bit value to observe
   @return The number of bits [from the lsb up] that are zero
*/
int ocb3_int_ntz(unsigned long x)
{
   int c;
   x &= 0xFFFFFFFFUL;
   c = 0;
   while ((x & 1) == 0) {
      ++c;
      x >>= 1;
   }
   return c;
}

#endif

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