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comparison libtomcrypt/src/pk/asn1/der/bit/der_length_bit_string.c @ 399:a707e6148060

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merge of '5fdf69ca60d1683cdd9f4c2595134bed26394834' and '6b61c50f4cf888bea302ac8fcf5dbb573b443251'
author Matt Johnston <matt@ucc.asn.au>
date Sat, 03 Feb 2007 08:20:34 +0000
parents 0cbe8f6dbf9e
children f849a5ca2efc
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394:17d097fc111c 399:a707e6148060
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.com
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: 1.2 $ */
54 /* $Date: 2006/03/31 14:15:35 $ */