| /* 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 $ */ |