docs: function getrange(key, start, end, req) {
    var val = this.getKey(key, req);
    if(!val) return '';
    start = parseInt(start);
    end = parseInt(end);
    if(start < 0) start = val.length + start;
    if(end < 0) end = val.length + end;
    // TODO: buffer compat
    return (val + '').substr(start, end + 1);
  }