protected function read_file() {
		if ( ! WC_Product_CSV_Importer_Controller::is_file_valid_csv( $this->file ) ) {
			wp_die( esc_html__( 'Invalid file type. The importer supports CSV and TXT file formats.', 'woocommerce' ) );
		}

		$handle = fopen( $this->file, 'r' ); // @codingStandardsIgnoreLine.

		if ( false !== $handle ) {
			$this->raw_keys = version_compare( PHP_VERSION, '5.3', '>=' ) ? array_map( 'trim', fgetcsv( $handle, 0, $this->params['delimiter'], $this->params['enclosure'], $this->params['escape'] ) ) : array_map( 'trim', fgetcsv( $handle, 0, $this->params['delimiter'], $this->params['enclosure'] ) ); // @codingStandardsIgnoreLine

			// Remove BOM signature from the first item.
			if ( isset( $this->raw_keys[0] ) ) {
				$this->raw_keys[0] = $this->remove_utf8_bom( $this->raw_keys[0] );
			}

			if ( 0 !== $this->params['start_pos'] ) {
				fseek( $handle, (int) $this->params['start_pos'] );
			}

			while ( 1 ) {
				$row = version_compare( PHP_VERSION, '5.3', '>=' ) ? fgetcsv( $handle, 0, $this->params['delimiter'], $this->params['enclosure'], $this->params['escape'] ) : fgetcsv( $handle, 0, $this->params['delimiter'], $this->params['enclosure'] ); // @codingStandardsIgnoreLine

				if ( false !== $row ) {
					$this->raw_data[]                                 = $row;
					$this->file_positions[ count( $this->raw_data ) ] = ftell( $handle );

					if ( ( $this->params['end_pos'] > 0 && ftell( $handle ) >= $this->params['end_pos'] ) || 0 === --$this->params['lines'] ) {
						break;
					}
				} else {
					break;
				}
			}

			$this->file_position = ftell( $handle );
		}

		if ( ! empty( $this->params['mapping'] ) ) {
			$this->set_mapped_keys();
		}

		if ( $this->params['parse'] ) {
			$this->set_parsed_data();
		}
	}