diff options
Diffstat (limited to 'libtomcrypt/src/pk/asn1/der/bit/der_length_bit_string.c')
-rw-r--r-- | libtomcrypt/src/pk/asn1/der/bit/der_length_bit_string.c | 54 |
1 files changed, 54 insertions, 0 deletions
diff --git a/libtomcrypt/src/pk/asn1/der/bit/der_length_bit_string.c b/libtomcrypt/src/pk/asn1/der/bit/der_length_bit_string.c new file mode 100644 index 0000000..dd6ea6d --- /dev/null +++ b/libtomcrypt/src/pk/asn1/der/bit/der_length_bit_string.c @@ -0,0 +1,54 @@ +/* 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_bit_string.c + ASN.1 DER, get length of BIT STRING, Tom St Denis +*/ + +#ifdef LTC_DER +/** + Gets length of DER encoding of BIT STRING + @param nbits The number of bits in the string to encode + @param outlen [out] The length of the DER encoding for the given string + @return CRYPT_OK if successful +*/ +int der_length_bit_string(unsigned long nbits, unsigned long *outlen) +{ + unsigned long nbytes; + LTC_ARGCHK(outlen != NULL); + + /* get the number of the bytes */ + nbytes = (nbits >> 3) + ((nbits & 7) ? 1 : 0) + 1; + + if (nbytes < 128) { + /* 03 LL PP DD DD DD ... */ + *outlen = 2 + nbytes; + } else if (nbytes < 256) { + /* 03 81 LL PP DD DD DD ... */ + *outlen = 3 + nbytes; + } else if (nbytes < 65536) { + /* 03 82 LL LL PP DD DD DD ... */ + *outlen = 4 + nbytes; + } else { + return CRYPT_INVALID_ARG; + } + + return CRYPT_OK; +} + +#endif + + +/* $Source: /cvs/libtom/libtomcrypt/src/pk/asn1/der/bit/der_length_bit_string.c,v $ */ +/* $Revision: 1.1 $ */ +/* $Date: 2005/05/16 15:08:11 $ */ |