NAME¶

tevent_context - Chapter 1: Tevent context

Tevent context¶

Tevent context is an essential logical unit of tevent library. For working with events at least one such context has to be created - allocated, initialized. Then, events which are meant to be caught and handled have to be registered within this specific context. Reason for subordinating events to a tevent context structure rises from the fact that several context can be created and each of them is processed at different time. So, there can be 1 context containing just file descriptor events, another one taking care of signal and time events and the third one which keeps information about the rest.

Tevent loops are the part of the library which represents the mechanism where noticing events and triggering handlers actually happens. They accept just one argument - tevent context structure. Therefore if theoretically an infinity loop (tevent_loop_wait) was called, only those arguments which belong to the passed tevent context structure can be caught and invoked within this call. Although some more signal events were registered (but within some other context) they will not be noticed.

TALLOC_CTX *mem_ctx = talloc_new(NULL);
if (mem_ctx == NULL) {


    // error handling
}
struct tevent_context *ev_ctx = tevent_context_init(mem_ctx);
if(ev_ctx == NULL) {


    // error handling
}

Tevent loops¶

Tevent loops are the dispatcher for events. They catch them and trigger the handlers. In the case of longer processes, the program spends most of its time at this point waiting for events, invoking handlers and waiting for another event again. There are 2 types of loop available for use in tevent library:

• int tevent_loop_wait()
• int tevent_loop_once()

Both of functions accept just one parameter (tevent context) and the only difference lies in the fact that the first loop can theoretically last for ever but the second one will wait just for a single one event to catch and then the loop breaks and the program continue.