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comparison libtomcrypt/src/pk/asn1/der/short_integer/der_length_short_integer.c @ 285:1b9e69c058d2

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propagate from branch 'au.asn.ucc.matt.ltc.dropbear' (head 20dccfc09627970a312d77fb41dc2970b62689c3) to branch 'au.asn.ucc.matt.dropbear' (head fdf4a7a3b97ae5046139915de7e40399cceb2c01)
author Matt Johnston <matt@ucc.asn.au>
date Wed, 08 Mar 2006 13:23:58 +0000
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children 0cbe8f6dbf9e
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281:997e6f7dc01e 285:1b9e69c058d2
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 #include "tomcrypt.h"
12
13 /**
14 @file der_length_short_integer.c
15 ASN.1 DER, get length of encoding, Tom St Denis
16 */
17
18
19 #ifdef LTC_DER
20 /**
21 Gets length of DER encoding of num
22 @param num The integer to get the size of
23 @param outlen [out] The length of the DER encoding for the given integer
24 @return CRYPT_OK if successful
25 */
26 int der_length_short_integer(unsigned long num, unsigned long *outlen)
27 {
28 unsigned long z, y, len;
29
30 LTC_ARGCHK(outlen != NULL);
31
32 /* force to 32 bits */
33 num &= 0xFFFFFFFFUL;
34
35 /* get the number of bytes */
36 z = 0;
37 y = num;
38 while (y) {
39 ++z;
40 y >>= 8;
41 }
42
43 /* handle zero */
44 if (z == 0) {
45 z = 1;
46 }
47
48 /* we need a 0x02 to indicate it's INTEGER */
49 len = 1;
50
51 /* length byte */
52 ++len;
53
54 /* bytes in value */
55 len += z;
56
57 /* see if msb is set */
58 len += (num&(1UL<<((z<<3) - 1))) ? 1 : 0;
59
60 /* return length */
61 *outlen = len;
62 return CRYPT_OK;
63 }
64
65 #endif
66
67 /* $Source: /cvs/libtom/libtomcrypt/src/pk/asn1/der/short_integer/der_length_short_integer.c,v $ */
68 /* $Revision: 1.3 $ */
69 /* $Date: 2005/05/23 01:35:38 $ */