Manage ivykis objects for event notification
#include <iv_event_raw.h>
struct iv_event_raw {
void *cookie;
void (*handler)(void *);
};
void IV_EVENT_RAW_INIT(struct iv_event_raw *this);
int iv_event_raw_register(struct iv_event_raw *this);
void iv_event_raw_unregister(struct iv_event_raw *this);
void iv_event_raw_post(struct iv_event_raw *this);
iv_event_raw provides a way for delivering events to ivykis(3) recipients across thread and process boundaries.
The intended event recipient calls IV_EVENT_RAW_INIT on a struct iv_event_raw object, fills in ->cookie and ->handler, and then calls iv_event_raw_register on the object.
To generate an event, call iv_event_raw_post on the previously initialized struct iv_event_raw object. This will cause the callback specified by ->handler to be called in the thread that the struct iv_event_raw object was registered in, with ->cookie as its sole argument.
To deinitialize a struct iv_event_raw object, call iv_event_raw_unregister from the same thread that iv_event_raw_register was called from on that object.
It is permitted to unregister a struct iv_event_raw object from any ivykis callback function in the thread it was registered in, including from a callback function triggered by this object, and it is permitted to free the memory corresponding to an unregistered object from its own callback function.
iv_event_raw_post can be called from the same thread that iv_event_raw_register was called from, from a different thread in the same process, or even from a different process, and can safely be called from signal handlers.
If posting an event only ever needs to be done from within the same process, see iv_event(3) for a lighter-weight alternative to iv_event_raw.
Internally, iv_event_raw is implemented by registering a file descriptor (a struct iv_fd(3)) with the recipient thread's ivykis event loop, and by causing that file descriptor to become readable upon a call to iv_event_raw_post.
If eventfd(2) is available, it will be used to procure the abovementioned file descriptor. If not, iv_event_raw will fall back to pipe(2) as the source of its file descriptors. eventfd(2) is preferred as it requires only one file descriptor table entry (while pipe(2) requires two), and has much less kernel overhead than pipe(2) has.