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comparison libtomcrypt/src/pk/asn1/der/bit/der_encode_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_encode_bit_string.c
15 ASN.1 DER, encode a BIT STRING, Tom St Denis
16 */
17
18
19 #ifdef LTC_DER
20
21 /**
22 Store a BIT STRING
23 @param in The array of bits to store (one per char)
24 @param inlen The number of bits tostore
25 @param out [out] The destination for the DER encoded BIT STRING
26 @param outlen [in/out] The max size and resulting size of the DER BIT STRING
27 @return CRYPT_OK if successful
28 */
29 int der_encode_bit_string(const unsigned char *in, unsigned long inlen,
30 unsigned char *out, unsigned long *outlen)
31 {
32 unsigned long len, x, y;
33 unsigned char buf;
34 int err;
35
36 LTC_ARGCHK(in != NULL);
37 LTC_ARGCHK(out != NULL);
38 LTC_ARGCHK(outlen != NULL);
39
40 /* avoid overflows */
41 if ((err = der_length_bit_string(inlen, &len)) != CRYPT_OK) {
42 return err;
43 }
44
45 if (len > *outlen) {
46 *outlen = len;
47 return CRYPT_BUFFER_OVERFLOW;
48 }
49
50 /* store header (include bit padding count in length) */
51 x = 0;
52 y = (inlen >> 3) + ((inlen&7) ? 1 : 0) + 1;
53
54 out[x++] = 0x03;
55 if (y < 128) {
56 out[x++] = (unsigned char)y;
57 } else if (y < 256) {
58 out[x++] = 0x81;
59 out[x++] = (unsigned char)y;
60 } else if (y < 65536) {
61 out[x++] = 0x82;
62 out[x++] = (unsigned char)((y>>8)&255);
63 out[x++] = (unsigned char)(y&255);
64 }
65
66 /* store number of zero padding bits */
67 out[x++] = (unsigned char)((8 - inlen) & 7);
68
69 /* store the bits in big endian format */
70 for (y = buf = 0; y < inlen; y++) {
71 buf |= (in[y] ? 1 : 0) << (7 - (y & 7));
72 if ((y & 7) == 7) {
73 out[x++] = buf;
74 buf = 0;
75 }
76 }
77 /* store last byte */
78 if (inlen & 7) {
79 out[x++] = buf;
80 }
81 *outlen = x;
82 return CRYPT_OK;
83 }
84
85 #endif
86
87 /* $Source: /cvs/libtom/libtomcrypt/src/pk/asn1/der/bit/der_encode_bit_string.c,v $ */
88 /* $Revision: 1.4 $ */
89 /* $Date: 2006/12/04 21:34:03 $ */