Avifinfo

Parser::parse_iref │ private │ WP 1.0

Parses an "iref" box.

The "dimg" boxes contain links between tiles and their parent items, which can be used to infer bit depth and number of channels for the primary item when the latter does not have these properties.

Method of the class: Parser{}

No Hooks.

Returns

Status. FOUND on success or an error on failure.

Usage

// private - for code of main (parent) class only
$result = $this->parse_iref( $num_remaining_bytes );

$num_remaining_bytes(int) (required)

The number of bytes that should be available from the resource.

Parser::parse_iref() Parser::parse iref code ^{WP 6.9.1}

private function parse_iref( $num_remaining_bytes ) {
  do {
    $box    = new Box();
    $status = $box->parse( $this->handle, $this->num_parsed_boxes, $num_remaining_bytes );
    if ( $status != FOUND ) {
      return $status;
    }

    if ( $box->type == 'dimg' ) {
      // See ISO/IEC 14496-12:2015(E) 8.11.12.2
      $num_bytes_per_id = ( $box->version == 0 ) ? 2 : 4;
      $num_read_bytes   = $num_bytes_per_id + 2;
      if ( $box->content_size < $num_read_bytes ) {
        return INVALID;
      }
      if ( !( $data = read( $this->handle, $num_read_bytes ) ) ) {
        return TRUNCATED;
      }
      $from_item_id    = read_big_endian( $data, $num_bytes_per_id );
      $reference_count = read_big_endian( substr( $data, $num_bytes_per_id, 2 ), 2 );

      for ( $i = 0; $i < $reference_count; ++$i ) {
        if ( $i >= MAX_TILES ) {
          $this->data_was_skipped = true;
          break;
        }
        $num_read_bytes += $num_bytes_per_id;
        if ( $box->content_size < $num_read_bytes ) {
          return INVALID;
        }
        if ( !( $data = read( $this->handle, $num_bytes_per_id ) ) ) {
          return TRUNCATED;
        }
        $to_item_id = read_big_endian( $data, $num_bytes_per_id );
        $tile_count = count( $this->features->tiles );
        if ( $from_item_id <= MAX_VALUE && $to_item_id <= MAX_VALUE &&
             $tile_count < MAX_TILES ) {
          $this->features->tiles[$tile_count]                 = new Tile();
          $this->features->tiles[$tile_count]->tile_item_id   = $to_item_id;
          $this->features->tiles[$tile_count]->parent_item_id = $from_item_id;
        } else {
          $this->data_was_skipped = true;
        }
      }

      // If all features are available now, do not look further.
      $status = $this->features->get_primary_item_features();
      if ( $status != NOT_FOUND ) {
        return $status;
      }

      // Mostly if 'data_was_skipped'.
      if ( !skip( $this->handle, $box->content_size - $num_read_bytes ) ) {
        return TRUNCATED;
      }
    } else {
      if ( !skip( $this->handle, $box->content_size ) ) {
        return TRUNCATED;
      }
    }
    $num_remaining_bytes -= $box->size;
  } while ( $num_remaining_bytes > 0 );
  return NOT_FOUND;
}