The EventBase class

Intro

EventBase class represents libevent's event base structure. It holds a set of events and can poll to determine which events are active.

Each event base has a method, or a backend that it uses to determine which events are ready. The recognized methods are: select, poll, epoll, kqueue, devpoll, evport and win32.

To configure event base to use, or avoid specific backend EventConfig class can be used.

Class synopsis

Predefined Constants

EventBase::LOOP_ONCE

Flag used with EventBase::loop method which means: "block until libevent has an active event, then exit once all active events have had their callbacks run".

EventBase::LOOP_NONBLOCK

Flag used with EventBase::loop method which means: "do not block: see which events are ready now, run the callbacks of the highest-priority ones, then exit".

EventBase::NOLOCK

Configuration flag. Do not allocate a lock for the event base, even if we have locking set up".

EventBase::STARTUP_IOCP

Windows-only configuration flag. Enables the IOCP dispatcher at startup.

EventBase::NO_CACHE_TIME

Configuration flag. Instead of checking the current time every time the event loop is ready to run timeout callbacks, check after each timeout callback.

EventBase::EPOLL_USE_CHANGELIST

If we are using the epoll backend, this flag says that it is safe to use Libevent's internal change-list code to batch up adds and deletes in order to try to do as few syscalls as possible.

Setting this flag can make code run faster, but it may trigger a Linux bug: it is not safe to use this flag if one has any fds cloned by dup(), or its variants. Doing so will produce strange and hard-to-diagnose bugs.

This flag can also be activated by setting the EVENT_EPOLL_USE_CHANGELIST environment variable.

This flag has no effect if one winds up using a backend other than epoll.

Eventbase