Listing 1.4
Level 2 and Level 1 Decoding

int L2_Decode( uchar *dst,     /* Decoded name target buffer.   */
               uchar *src,     /* Encoded name source buffer.   */
               int    srcpos,  /* Start position of name.       */
               int    srcmax ) /* Size of source buffer.        */
  {
  int len;
  int pos;
  int next;

  /* Be safe. */
  dst[0] = '\0';
  
  /* Get encoded string length (doesn't include root label). */
  len = strlen( (char *)&(src[srcpos]) );

  /* If length is zero, return the empty string. */
  if( 0 == len )
    return( 0 );

  /* Make sure name does not exceed source buffer length. */
  if( len >= (srcmax - srcpos) )
    return( -1 );

  /* Copy source to destination skipping the first label length byte
   * (but including the terminating nul label length).
   */
  (void)memcpy( dst, &(src[srcpos+1]), len );

  /* Find remaining label length bytes and convert them to dots.  */
  for( pos = src[srcpos];         /* Read the first label length. */
       '\0' != (next = dst[pos]); /* While label length is > 0... */
       pos += next + 1 )          /* Move one byte beyond label.  */
    {
    dst[pos] = '.';
    }

  return( --len );  /* Return string length. */
  } /* L2_Decode */


int L1_Decode( uchar *name,    /* Target.  Minimum 16 bytes. */
               uchar *src,     /* Message buffer.            */
               int    srcpos,  /* Start position of name.    */
               int    srcmax ) /* Size of source buffer.     */
  {
  int    i;
  int    suffix;
  uchar *p = &src[srcpos];

  /* Make sure we have 32 bytes worth of message to read.    */
  if( (srcmax - srcpos) < 32 )
    {
    name[0] = '\0';
    return( -1 );
    }

  /* Convert each source pair to their original octet value. */
  for( i = 0; i < 32; i++ )
    name[i/2] = ( (( (int)(p[i]) - 'A' ) << 4)
                +  ( (int)(p[++i]) - 'A' ) );

  /* Copy out suffix byte and replace with nul terminator.   */
  suffix = name[15];
  name[15] = '\0';

  /* Trim off trailing spaces, if any. */
  for( i = 14; (i >= 0) && (' ' == name[i]); i-- )
    name[i] = '\0';

  return( suffix );   /* Return the suffix value as an int.  */
  } /* L1_Decode */

$Revision: 1.15 $ $Date: 2003/02/18 21:43:58 $

Copyright © 1999-2003 Christopher R. Hertel  Released under the terms of the LGPL