text: /* 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://libtom.org
   */
  #include "tomcrypt.h"
  
  /**
    @file der_decode_object_identifier.c
    ASN.1 DER, Decode Object Identifier, Tom St Denis
  */
  
  #ifdef LTC_DER
  /**
    Decode OID data and store the array of integers in words
    @param in      The OID DER encoded data
    @param inlen   The length of the OID data
    @param words   [out] The destination of the OID words
    @param outlen  [in/out] The number of OID words
    @return CRYPT_OK if successful
  */
  int der_decode_object_identifier(const unsigned char *in,    unsigned long  inlen,
                                         unsigned long *words, unsigned long *outlen)
  {
     unsigned long x, y, t, len;
  
     LTC_ARGCHK(in     != NULL);
     LTC_ARGCHK(words  != NULL);
     LTC_ARGCHK(outlen != NULL);
  
     /* header is at least 3 bytes */
     if (inlen < 3) {
        return CRYPT_INVALID_PACKET;
     }
  
     /* must be room for at least two words */
     if (*outlen < 2) {
        return CRYPT_BUFFER_OVERFLOW;
     }
  
     /* decode the packet header */
     x = 0;
     if ((in[x++] & 0x1F) != 0x06) {
        return CRYPT_INVALID_PACKET;
     }
     
     /* get the length */
     if (in[x] < 128) {
        len = in[x++]; 
     } else {
         if (in[x] < 0x81 || in[x] > 0x82) {
            return CRYPT_INVALID_PACKET;
         }
         y   = in[x++] & 0x7F;
         len = 0;
         while (y--) {
            len = (len << 8) | (unsigned long)in[x++];
         }
     }
  
     if (len < 1 || (len + x) > inlen) {
        return CRYPT_INVALID_PACKET;
     }
  
     /* decode words */
     y = 0;
     t = 0;
     while (len--) {
         t = (t << 7) | (in[x] & 0x7F);
         if (!(in[x++] & 0x80)) {
             /* store t */
             if (y >= *outlen) {
                return CRYPT_BUFFER_OVERFLOW;
             }
        if (y == 0) {
           words[0] = t / 40;
           words[1] = t % 40;
           y = 2;
        } else {
                words[y++] = t;
        }
             t          = 0;
         }
     }
         
     *outlen = y;
     return CRYPT_OK;
  }
  
  #endif
  
  /* $Source: /cvs/libtom/libtomcrypt/src/pk/asn1/der/object_identifier/der_decode_object_identifier.c,v $ */
  /* $Revision: 1.6 $ */
  /* $Date: 2006/12/28 01:27:24 $ */
  