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(const 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, respec‐
tively 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 descriptor,
and a callback function for that event has been specified, that call‐
back 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 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. 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 (->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 out‐
put, 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 transfer‐
ring 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 mod‐
ified 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, iv_fatal(2) 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 registration
error. Since iv_fd_register_try disables various internal optimisa‐
tions, it is recommended to use iv_fd_register whenever possible.
See iv_examples(3) for programming examples.
SEE ALSOivykis(3), iv_examples(3)ivykis 2010-08-15 iv_fd(3)
