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comparison libtomcrypt/src/pk/asn1/der/bit/der_length_bit_string.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_bit_string.c
15 ASN.1 DER, get length of BIT STRING, Tom St Denis
16 */
17
18 #ifdef LTC_DER
19 /**
20 Gets length of DER encoding of BIT STRING
21 @param nbits The number of bits in the string to encode
22 @param outlen [out] The length of the DER encoding for the given string
23 @return CRYPT_OK if successful
24 */
25 int der_length_bit_string(unsigned long nbits, unsigned long *outlen)
26 {
27 unsigned long nbytes;
28 LTC_ARGCHK(outlen != NULL);
29
30 /* get the number of the bytes */
31 nbytes = (nbits >> 3) + ((nbits & 7) ? 1 : 0) + 1;
32
33 if (nbytes < 128) {
34 /* 03 LL PP DD DD DD ... */
35 *outlen = 2 + nbytes;
36 } else if (nbytes < 256) {
37 /* 03 81 LL PP DD DD DD ... */
38 *outlen = 3 + nbytes;
39 } else if (nbytes < 65536) {
40 /* 03 82 LL LL PP DD DD DD ... */
41 *outlen = 4 + nbytes;
42 } else {
43 return CRYPT_INVALID_ARG;
44 }
45
46 return CRYPT_OK;
47 }
48
49 #endif
50
51
52 /* $Source: /cvs/libtom/libtomcrypt/src/pk/asn1/der/bit/der_length_bit_string.c,v $ */
53 /* $Revision: 1.1 $ */
54 /* $Date: 2005/05/16 15:08:11 $ */