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      1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
      2  *
      3  * LibTomCrypt is a library that provides various cryptographic
      4  * algorithms in a highly modular and flexible manner.
      5  *
      6  * The library is free for all purposes without any express
      7  * guarantee it works.
      8  *
      9  * Tom St Denis, tomstdenis (at) gmail.com, http://libtomcrypt.com
     10  */
     11 #include "tomcrypt.h"
     12 
     13 /**
     14   @file der_length_octet_string.c
     15   ASN.1 DER, get length of OCTET STRING, Tom St Denis
     16 */
     17 
     18 #ifdef LTC_DER
     19 /**
     20   Gets length of DER encoding of OCTET STRING
     21   @param noctets  The number of octets in the string to encode
     22   @param outlen   [out] The length of the DER encoding for the given string
     23   @return CRYPT_OK if successful
     24 */
     25 int der_length_octet_string(unsigned long noctets, unsigned long *outlen)
     26 {
     27    LTC_ARGCHK(outlen != NULL);
     28 
     29    if (noctets < 128) {
     30       /* 04 LL DD DD DD ... */
     31       *outlen = 2 + noctets;
     32    } else if (noctets < 256) {
     33       /* 04 81 LL DD DD DD ... */
     34       *outlen = 3 + noctets;
     35    } else if (noctets < 65536UL) {
     36       /* 04 82 LL LL DD DD DD ... */
     37       *outlen = 4 + noctets;
     38    } else if (noctets < 16777216UL) {
     39       /* 04 83 LL LL LL DD DD DD ... */
     40       *outlen = 5 + noctets;
     41    } else {
     42       return CRYPT_INVALID_ARG;
     43    }
     44 
     45    return CRYPT_OK;
     46 }
     47 
     48 #endif
     49 
     50 
     51 /* $Source: /cvs/libtom/libtomcrypt/src/pk/asn1/der/octet/der_length_octet_string.c,v $ */
     52 /* $Revision: 1.2 $ */
     53 /* $Date: 2006/03/31 14:15:35 $ */
     54