protected function readInt32( $pos = 0 ) {
		static $lookups;

		if ( !$lookups ) {
			$lookups = [];
			for ( $i = 1; $i < 256; $i++ ) {
				$lookups[ chr( $i ) ] = $i;
			}
		}

		$buf = $this->read( $pos, 4 );

		$rv = 0;

		if ( $buf[0] !== "\x0" ) {
			$rv = $lookups[ $buf[0] ];
		}
		if ( $buf[1] !== "\x0" ) {
			$rv |= ( $lookups[ $buf[1] ] << 8 );
		}
		if ( $buf[2] !== "\x0" ) {
			$rv |= ( $lookups[ $buf[2] ] << 16 );
		}
		if ( $buf[3] !== "\x0" ) {
			$rv |= ( $lookups[ $buf[3] ] << 24 );
		}

		return $rv;
	}