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

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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
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children 39d5d58461d6
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143:5d99163f7e32 191:1c15b283127b
1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
2 *
3 * LibTomCrypt is a library that provides various cryptographic
4 * algorithms in a highly modular and flexible manner.
5 *
6 * The library is free for all purposes without any express
7 * guarantee it works.
8 *
9 * Tom St Denis, [email protected], http://libtomcrypt.org
10 */
11
12 /**
13 @file ocb_ntz.c
14 OCB implementation, internal function, by Tom St Denis
15 */
16
17 #include "tomcrypt.h"
18
19 #ifdef OCB_MODE
20
21 /**
22 Returns the number of leading zero bits [from lsb up]
23 @param x The 32-bit value to observe
24 @return The number of bits [from the lsb up] that are zero
25 */
26 int ocb_ntz(unsigned long x)
27 {
28 int c;
29 x &= 0xFFFFFFFFUL;
30 c = 0;
31 while ((x & 1) == 0) {
32 ++c;
33 x >>= 1;
34 }
35 return c;
36 }
37
38 #endif