iv_fd_unregister register, respectively unregister, a file descriptor with the current
threads 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 descriptor,
and a callback function for that event has been specified, that
callback function will be called in the thread that the file descriptor
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
current threads 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
->handler_in member after the file descriptor has been registered, this function
has to be used instead. Conversely, 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
iv_fd_set_handler_err is analogous to
iv_fd_set_handler_out, only it deals with the callback function for error conditions
When a handler function was NULL, and was set to a non-NULL value
iv_fd_set_handler_in, iv_fd_set_handler_out or
iv_fd_set_handler_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 threads 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 transferring 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
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 isnt open or is
will be invoked. If it is not known whether registering the file
descriptor with the kernel will be successful 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 registration error.
iv_fd_register_try disables various internal optimisations, it is recommended to use
iv_fd_register whenever possible.
for programming examples.