The EventBase class

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- The EventBase class

# The EventBase class

(PECL event >= 1.2.6-beta)

## Introduction

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.

Warning

Do NOT destroy the EventBase object as long as resources of the associated `Event` objects are not released. Otherwise, it will lead to unpredictable results!

## Class synopsis

final class EventBase {
/* Constants */
const int LOOP_ONCE = 1;
const int LOOP_NONBLOCK = 2;
const int NOLOCK = 1;
const int STARTUP_IOCP = 4;
const int NO_CACHE_TIME = 8;
const int EPOLL_USE_CHANGELIST = 16;
/* Methods */
public __construct( EventConfig `$cfg` = ?)
public dispatch(): void
public exit( float `$timeout` = ?): bool
public free(): void
public getFeatures(): int
public getMethod(): string
public getTimeOfDayCached(): float
public gotExit(): bool
public gotStop(): bool
public loop( int `$flags` = ?): bool
public priorityInit( int `$n_priorities` ): bool
public reInit(): bool
public stop(): bool
}

## 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 settnig the `EVENT_EPOLL_USE_CHANGELIST` environment variable.

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

## Table of Contents

- EventBase::__construct — Constructs EventBase object
- EventBase::dispatch — Dispatch pending events
- EventBase::exit — Stop dispatching events
- EventBase::free — Free resources allocated for this event base
- EventBase::getFeatures — Returns bitmask of features supported
- EventBase::getMethod — Returns event method in use
- EventBase::getTimeOfDayCached — Returns the current event base time
- EventBase::gotExit — Checks if the event loop was told to exit
- EventBase::gotStop — Checks if the event loop was told to exit
- EventBase::loop — Dispatch pending events
- EventBase::priorityInit — Sets number of priorities per event base
- EventBase::reInit — Re-initialize event base(after a fork)
- EventBase::stop — Tells event_base to stop dispatching events