iv_fd(3)						    ivykis programmer's manual							  iv_fd(3)

NAME

       iv_fd_register,	iv_fd_register_try, iv_fd_unregister, iv_fd_registered, iv_fd_set_handler_in, iv_fd_set_handler_err, iv_fd_set_handler_out
       - deal with ivykis file descriptors

SYNOPSIS

       #include <iv.h>

       struct iv_fd {
	       int	       fd;
	       void	       *cookie;
	       void	       (*handler_in)(void *);
	       void	       (*handler_out)(void *);
	       void	       (*handler_err)(void *);
       };

       void IV_FD_INIT(struct iv_fd *fd);
       void iv_fd_register(struct iv_fd *fd);
       int iv_fd_register_try(struct iv_fd *fd);
       void iv_fd_unregister(struct iv_fd *fd);
       int iv_fd_registered(struct iv_fd *fd);
       void iv_fd_set_handler_in(struct iv_fd *fd, void (*handler)(void *));
       void iv_fd_set_handler_out(struct iv_fd *fd, void (*handler)(void *));
       void iv_fd_set_handler_err(struct iv_fd *fd, void (*handler)(void *));

DESCRIPTION

       The functions iv_fd_register and iv_fd_unregister register, respectively unregister, a file descriptor with  the  current  thread's  ivykis
       event loop.  Calling iv_fd_registered on a file descriptor returns true if that file descriptor is currently registered with ivykis.

       When a file descriptor that is registered with ivykis becomes ready for input or output, or an error condition occurs on that file descrip-
       tor, and a callback function for that event has been specified, that callback function will be called in the thread that the file  descrip-
       tor was registered in.

       And  conversely,  when a file descriptor that is already ready for input or output or already has an error condition set is registered with
       ivykis, and the corresponding callback function pointer is not NULL, the callback function will be called in the next iteration of the cur-
       rent thread's ivykis event loop.

       Before  a file descriptor is registered, it must have been initialised by calling IV_FD_INIT on it, and must have had its ->fd member field
       set to a valid OS file descriptor.  The ->handler_in, ->handler_out and ->handler_err member fields point to callback functions that are to
       be  called  when  the specified file descriptor becomes ready for input or output or an error condition occurs.	If any handler function is
       set to NULL, it indicates that the application is not interested in being notified of the corresponding event.

       An application is not allowed to change the ->fd member while a file descriptor is registered.

       iv_fd_set_handler_in changes the callback function to be called when descriptor fd becomes ready for input.  An application is not  allowed
       to  directly  change  the  ->handler_in	member	after the file descriptor has been registered, this function has to be used instead.  Con-
       versely, it is not allowed to use this function before the file descriptor has been registered.

       iv_fd_set_handler_out is analogous to iv_fd_set_handler_in, only it deals with the callback function for output readiness (->handler_out).

       iv_fd_set_handler_err is analogous to iv_fd_set_handler_in and iv_fd_set_handler_out, only it deals with the callback  function	for  error
       conditions (->handler_err).

       When  a handler function was NULL, and was set to a non-NULL value by calling iv_fd_set_handler_in, iv_fd_set_handler_out or iv_fd_set_han-
       dler_err, and the file descriptor was already ready for input or output, or already had an error condition set, an event is generated,  and
       the  specified callback function will be called in the next iteration of the current thread's event loop.  The application does not need to
       poll the file descriptor to see if a condition was already raised.

       Callback functions are passed a cookie value as their first and sole argument.  If the application wishes to use this facility  for  trans-
       ferring data to the callback function, it should set the ->cookie member of a file descriptor to a value of type void *.  This value can be
       modified directly by the application at any time without calling a helper function.

       When a file descriptor is registered with ivykis, it is transparently set to nonblocking mode, and configured to be closed on exit(3).

       An application is allowed to unregister a file descriptor from within any callback function, including callback functions triggered by that
       file  descriptor  itself,  and even to free the memory corresponding to that file descriptor from any callback function, but a struct iv_fd
       can only be unregistered in the thread that it was registered from.

       It is allowed to register the same underlying OS file descriptor in multiple threads, but a given struct iv_fd can only	be  registered	in
       one thread at a time.

       iv_fd_register does not return errors to the caller, and in case of an error while registering the file descriptor, for example if it isn't
       open or is unpollable, abort(3) will be invoked.  If it is not known whether registering the file descriptor with the kernel will  be  suc-
       cessful	or  not, use iv_fd_register_try instead, which is a variant on iv_fd_register which returns a nonzero value in case of a registra-
       tion error.  Since iv_fd_register_try disables various internal optimisations, it is recommended to use iv_fd_register whenever possible.

       See iv_examples(3) for programming examples.

SEE ALSO

       ivykis(3), iv_examples(3)

ivykis								    2010-08-15								  iv_fd(3)