function isDigit( ch )
  {
    if ( (ch >= '0') && (ch <= '9') ) return true;
    else return false;
  }


  function isAlpha( ch )
  {
    if ( ((ch >= 'a') && (ch <= 'z')) || ((ch >= 'A') && (ch <= 'Z')) ) return true;
    else return false;
  }


  function isAlnum( ch )
  {
    if ( isAlpha( ch ) || isDigit( ch ) ) return true;
    else return false;
  }


  function notIn( str1, str2 )
  {
    var i = 0;
    var j = str2.length;
    for( ; i<j; i++ )
    {
      var str3 =  str2.charAt(i);
      if( str1.indexOf( str3 ) != -1 ) return false;
    }
    return true;
  }


  function checkUsername( username, mustBeQuoted )
  {
    var i = 0;
    var j = username.length;
    if ( username.charAt(0) != '"' )
    {
      if ( (username.charAt(0) <  ' ') || (username.charAt(0) >  '~')
            || !notIn( mustBeQuoted, username.charAt(0) ) )
        return false;
      for( i=1; i<j; i++ )
      {
        if ( ( (username.charAt(i) < ' ') || (username.charAt(i) >  '~')
              || !notIn ( mustBeQuoted, username.charAt(i) ) )
             && ( username.charAt(i-1) != '\\' ) )
          return false;
      }
    }
    else
    {
      if ( username.charAt( j-1 ) != '"' ) return false;
      for( i=1; i<j-1; i++ )
      {
        if ( ( (username.charAt(i) == '\n') || (username.charAt(i) == '\r')
              || (username.charAt(i) == '\"') )
            && (username.charAt(i-1) != '\\') )
          return false;
      }

    }
    return true;
  }


  function checkNr ( nr )
  {
    var i=0;
    var j=nr.length;

    if( j < 1 ) return false;

    for( ; i<j; i++ )
      if( ( nr.charAt(i) < '0' ) || ( nr.charAt(i) > '9' ) ) return false;

    return true;
  }


  function checkIpnr( ipnr )
  {
    var iL=0;
    var iC=0;
    var i=0;
    var sNr = "";

    for( ; i< ipnr.length; i++ )
    {
      if ( ipnr.charAt(i) == '.' )
      {
        if ( !iL || (iL> 3) || parseInt( sNr,10 ) > 255 ) return false;
        iC++;
        iL = 0;
        sNr = "";
        continue;
      }
      if ( isDigit ( ipnr.charAt(i) ) )
      {
        iL++;
        sNr = sNr + ipnr.charAt(i);
        continue;
      }
      return false;
    }

    if ( parseInt( sNr,10 ) > 255 ) return false;
    if ( ( (iC==3) && (iL>=1) && (iL<=3) ) || ( (iC==4) && (!iL) )  ) return true;
    else return false;
  }


  function checkFqdn( fqdn )
  {
    var iL=0;
    var iC=0;
    var i=fqdn.length-1;

    if ( (fqdn.charAt(0) == '.') || (fqdn.charAt(0) == '-') ) return false;
    if ( fqdn.charAt(i) == '.' ) i=i-1;

    for( ; i>=0; i-- )
    {
      if ( fqdn.charAt(i) == '.' )
      {
        if ( iL < 2 && iC < 2 ) return false;
        if ( fqdn.charAt(i-1) == '-' ) return false;
        iC++;
        iL = 0;
        continue;
      }
      if ( isAlnum ( fqdn.charAt(i) ) )
      {
        iL++;
        continue;
      }
      if ( fqdn.charAt(i) == '-' )
      {
        if ( !iL ) return false;
        iL++;
        continue;
      }
      return false;
    }

    if ( !iC || ( iL == 1 && iC < 2 ) || ( !iL && iC==1 ) ) return false;

    return true;
  }


  function checkHostname( hostname )
  {
    if ( hostname.charAt(0) == '[' )
    {
      if ( hostname.charAt(hostname.length-1) != ']' ) return false;
      var ipnr = hostname.substring( 1, hostname.length -1 );
      return checkIpnr( ipnr );
    }

    if ( hostname.charAt(0) == '#' )
    {
      var nr = hostname.substring( 1, hostname.length );
      return checkNr( nr );
    }

    return checkFqdn( hostname );
  }


  function checkEmailAdr( address )
  {
    var status = true;
    var username = "";
    var hostname = "";

    if ( address.length < 8 ) return false;

    var seperate = address.lastIndexOf("@");
    if ( seperate == -1 ) return false;

    username = address.substring(0, seperate );
    if ( ! checkUsername( username, "<>()[],;:@\" " ) ) return false;

    hostname = address.substring(seperate+1, address.length );
    if ( ! checkHostname( hostname ) ) return false;

    return true;
  }


  function checkEmail( email, allowFullname )
  {
    var existFullname = false;
    var status = true;
    var fullname = "";
    var adress = "";
    if ( email.length < 8 ) return false;
    var emailBegin = email.indexOf("<");
    var emailEnd = email.lastIndexOf(">");

    if ( (emailBegin == -1) && (emailEnd == -1) ) return checkEmailAdr( email );

    if ( ( (emailBegin == -1) && (emailEnd != -1) )
        || ( (emailBegin != -1) && (emailEnd == -1) ) ) return false;

    adress = email.substring( emailBegin+1, emailEnd );

    if ( ! checkEmailAdr( adress ) ) return false;

    if ( email.length == adress.length + 2 ) return true;
    else if ( ! allowFullname ) return false;

    if ( emailEnd == email.length - 1 )
    {
      if ( emailBegin == 0 ) return true;
      if ( email.charAt( emailBegin -1 ) != ' ' ) return false;
      fullname = email.substring( 0, emailBegin-1 );
      return checkUsername ( fullname, "<>()[],;:@\"" );
    }
    return false ;
  }
//-->