Mercurial > dropbear
diff src/pk/asn1/der/short_integer/der_length_short_integer.c @ 209:39d5d58461d6 libtomcrypt-orig LTC_1.05
Import of libtomcrypt 1.05
author | Matt Johnston <matt@ucc.asn.au> |
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date | Wed, 06 Jul 2005 03:53:40 +0000 |
parents | |
children | d5faf4814ddb |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/pk/asn1/der/short_integer/der_length_short_integer.c Wed Jul 06 03:53:40 2005 +0000 @@ -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, [email protected], 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 $ */