der_encode_printable_string.c

这是由Rinick编写的加解密函数库。最近找了不少关于加解密的C源码

/* 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, [e-mail], http://libtomcrypt.org
 */
#include "tomcrypt.h"

/**
  @file der_encode_printable_string.c
  ASN.1 DER, encode a printable STRING, Tom St Denis
*/

#ifdef LTC_DER

/**
  Store an printable STRING
  @param in       The array of printable to store (one per char)
  @param inlen    The number of printable to store
  @param out      [out] The destination for the DER encoded printable STRING
  @param outlen   [in/out] The max size and resulting size of the DER printable STRING
  @return CRYPT_OK if successful
*/
int der_encode_printable_string(const unsigned char *in, unsigned long inlen,
                                unsigned char *out, unsigned long *outlen)
{
   unsigned long x, y, len;
   int           err;

   LTC_ARGCHK(in     != NULL);
   LTC_ARGCHK(out    != NULL);
   LTC_ARGCHK(outlen != NULL);

   /* get the size */
   if ((err = der_length_printable_string(in, inlen, &len)) != CRYPT_OK) {
      return err; 
   }

   /* too big? */
   if (len > *outlen) {
      return CRYPT_BUFFER_OVERFLOW;
   }

   /* encode the header+len */
   x = 0;
   out[x++] = 0x13;
   if (inlen < 128) {
      out[x++] = inlen;
   } else if (inlen < 256) {
      out[x++] = 0x81;
      out[x++] = inlen;
   } else if (inlen < 65536UL) {
      out[x++] = 0x82;
      out[x++] = (inlen>>8)&255;
      out[x++] = inlen&255;
   } else if (inlen < 16777216UL) {
      out[x++] = 0x83;
      out[x++] = (inlen>>16)&255;
      out[x++] = (inlen>>8)&255;
      out[x++] = inlen&255;
   } else {
      return CRYPT_INVALID_ARG;
   }

   /* store octets */
   for (y = 0; y < inlen; y++) {
       out[x++] = der_printable_char_encode(in[y]);
   }

   /* retun length */
   *outlen = x;

   return CRYPT_OK;
}

#endif

/* $Source: /cvs/libtom/libtomcrypt/src/pk/asn1/der/printable_string/der_encode_printable_string.c,v $ */
/* $Revision: 1.1 $ */
/* $Date: 2005/05/21 02:29:54 $ */