diff options
Diffstat (limited to 'libtomcrypt/src/pk/asn1/der/short_integer/der_length_short_integer.c')
-rw-r--r-- | libtomcrypt/src/pk/asn1/der/short_integer/der_length_short_integer.c | 69 |
1 files changed, 69 insertions, 0 deletions
diff --git a/libtomcrypt/src/pk/asn1/der/short_integer/der_length_short_integer.c b/libtomcrypt/src/pk/asn1/der/short_integer/der_length_short_integer.c new file mode 100644 index 0000000..7324b4a --- /dev/null +++ b/libtomcrypt/src/pk/asn1/der/short_integer/der_length_short_integer.c @@ -0,0 +1,69 @@ +/* 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.org + */ +#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: 1.3 $ */ +/* $Date: 2005/05/23 01:35:38 $ */ |