double
__call( sv_class, sv_path, sv_input )
	SV * sv_class
	SV * sv_path
	SV * sv_input
	CODE:
		char *class = SvPV( sv_class, PL_na );
		char *path = SvPV( sv_path, PL_na );
		double input = SvNV( sv_input );
		int fd;
		door_arg_t arg;
		double output;

		fd = open(path, O_RDWR);

		arg.data_ptr = (char *) &input;
		arg.data_size = sizeof(double);
		arg.desc_ptr = NULL;
		arg.desc_num = 0;
		arg.rbuf = (char *) &output;
		arg.rsize = sizeof(double);

		if ( door_call(fd, &arg) == 0 ) {
			RETVAL = output;
		} else {
			printf("ERRNO: %d\n",errno);
			RETVAL = -1;
		}
	OUTPUT:
		RETVAL