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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_length_short_integer.c
ASN.1 DER, get length of encoding, Tom St Denis
*/
#ifdef LTC_DER
/**
Gets length of DER encoding of num
@param num The integer to get the size of
@param outlen [out] The length of the DER encoding for the given integer
@return CRYPT_OK if successful
*/
int der_length_short_integer(unsigned long num, unsigned long *outlen)
{
unsigned long z, y, len;
LTC_ARGCHK(outlen != NULL);
/* force to 32 bits */
num &= 0xFFFFFFFFUL;
/* get the number of bytes */
z = 0;
y = num;
while (y) {
++z;
y >>= 8;
}
/* handle zero */
if (z == 0) {
z = 1;
}
/* we need a 0x02 to indicate it's INTEGER */
len = 1;
/* length byte */
++len;
/* bytes in value */
len += z;
/* see if msb is set */
len += (num&(1UL<<((z<<3) - 1))) ? 1 : 0;
/* return length */
*outlen = len;
return CRYPT_OK;
}
#endif
/* $Source: /cvs/libtom/libtomcrypt/src/pk/asn1/der/short_integer/der_length_short_integer.c,v $ */
/* $Revision: 1.5 $ */
/* $Date: 2006/03/31 14:15:35 $ */
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