Box

216class Box {217  public $size; // In bytes.218  public $type; // Four characters.219  public $version; // 0 or actual version if this is a full box.220  public $flags; // 0 or actual value if this is a full box.221  public $content_size; // 'size' minus the header size.222 223  /**224   * Reads the box header.225   *226   * @param stream  $handle              The resource the header will be parsed from.227   * @param int     $num_parsed_boxes    The total number of parsed boxes. Prevents timeouts.228   * @param int     $num_remaining_bytes The number of bytes that should be available from the resource.229   * @return Status                      FOUND on success or an error on failure.230   */231  public function parse( $handle, &$num_parsed_boxes, $num_remaining_bytes = MAX_SIZE ) {232    // See ISO/IEC 14496-12:2012(E) 4.2233    $header_size = 8; // box 32b size + 32b type (at least)234    if ( $header_size > $num_remaining_bytes ) {235      return INVALID;236    }237    if ( !( $data = read( $handle, 8 ) ) ) {238      return TRUNCATED;239    }240    $this->size = read_big_endian( $data, 4 );241    $this->type = substr( $data, 4, 4 );242    // 'box->size==1' means 64-bit size should be read after the box type.243    // 'box->size==0' means this box extends to all remaining bytes.244    if ( $this->size == 1 ) {245      $header_size += 8;246      if ( $header_size > $num_remaining_bytes ) {247        return INVALID;248      }249      if ( !( $data = read( $handle, 8 ) ) ) {250        return TRUNCATED;251      }252      // Stop the parsing if any box has a size greater than 4GB.253      if ( read_big_endian( $data, 4 ) != 0 ) {254        return ABORTED;255      }256      // Read the 32 least-significant bits.257      $this->size = read_big_endian( substr( $data, 4, 4 ), 4 );258    } else if ( $this->size == 0 ) {259      // ISO/IEC 14496-12 4.2.2:260      //   if size is 0, then this box shall be in a top-level box261      //   (i.e. not contained in another box)262      // Unfortunately the presence of a parent box is unknown here.263      $this->size = $num_remaining_bytes;264    }265    if ( $this->size < $header_size ) {266      return INVALID;267    }268    if ( $this->size > $num_remaining_bytes ) {269      return INVALID;270    }271 272    // 16 bytes of usertype should be read here if the box type is 'uuid'.273    // 'uuid' boxes are skipped so usertype is part of the skipped body.274 275    $has_fullbox_header = $this->type == 'meta' || $this->type == 'pitm' ||276                          $this->type == 'ipma' || $this->type == 'ispe' ||277                          $this->type == 'pixi' || $this->type == 'iref' ||278                          $this->type == 'auxC';279    if ( $has_fullbox_header ) {280      $header_size += 4;281    }282    if ( $this->size < $header_size ) {283      return INVALID;284    }285    $this->content_size = $this->size - $header_size;286    // Avoid timeouts. The maximum number of parsed boxes is arbitrary.287    ++$num_parsed_boxes;288    if ( $num_parsed_boxes >= MAX_NUM_BOXES ) {289      return ABORTED;290    }291 292    $this->version = 0;293    $this->flags   = 0;294    if ( $has_fullbox_header ) {295      if ( !( $data = read( $handle, 4 ) ) ) {