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/* LibTomCrypt, modular cryptographic library -- Tom St Denis
*
* LibTomCrypt is a library that provides various cryptographic
* algorithms in a highly modular and flexible manner.
*
* The library is free for all purposes without any express
* guarantee it works.
*
* Tom St Denis, tomstdenis@gmail.com, http://libtomcrypt.com
*/
#include "tomcrypt.h"
/**
@file der_encode_bit_string.c
ASN.1 DER, encode a BIT STRING, Tom St Denis
*/
#ifdef LTC_DER
/**
Store a BIT STRING
@param in The array of bits to store (one per char)
@param inlen The number of bits tostore
@param out [out] The destination for the DER encoded BIT STRING
@param outlen [in/out] The max size and resulting size of the DER BIT STRING
@return CRYPT_OK if successful
*/
int der_encode_bit_string(const unsigned char *in, unsigned long inlen,
unsigned char *out, unsigned long *outlen)
{
unsigned long len, x, y, buf;
int err;
LTC_ARGCHK(in != NULL);
LTC_ARGCHK(out != NULL);
LTC_ARGCHK(outlen != NULL);
/* avoid overflows */
if ((err = der_length_bit_string(inlen, &len)) != CRYPT_OK) {
return err;
}
if (len > *outlen) {
*outlen = len;
return CRYPT_BUFFER_OVERFLOW;
}
/* store header (include bit padding count in length) */
x = 0;
y = (inlen >> 3) + ((inlen&7) ? 1 : 0) + 1;
out[x++] = 0x03;
if (y < 128) {
out[x++] = y;
} else if (y < 256) {
out[x++] = 0x81;
out[x++] = y;
} else if (y < 65536) {
out[x++] = 0x82;
out[x++] = (y>>8)&255;
out[x++] = y&255;
}
/* store number of zero padding bits */
out[x++] = (8 - inlen) & 7;
/* store the bits in big endian format */
for (y = buf = 0; y < inlen; y++) {
buf |= (in[y] ? 1 : 0) << (7 - (y & 7));
if ((y & 7) == 7) {
out[x++] = buf;
buf = 0;
}
}
/* store last byte */
if (inlen & 7) {
out[x++] = buf;
}
*outlen = x;
return CRYPT_OK;
}
#endif
/* $Source: /cvs/libtom/libtomcrypt/src/pk/asn1/der/bit/der_encode_bit_string.c,v $ */
/* $Revision: 1.3 $ */
/* $Date: 2006/06/16 21:53:41 $ */
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