GHC.Event

This module provides scalable event notification for file descriptors and timeouts.

This module should be considered GHC internal.

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Types

data EventManager

The event manager state.

Creation

new :: IO EventManager

Create a new event manager.

getSystemEventManager :: IO (Maybe EventManager)

Retrieve the system event manager.

This function always returns Just the system event manager when using the threaded RTS and Nothing otherwise.

Running

loop :: EventManager -> IO ()

Start handling events. This function loops until told to stop, using shutdown.

Note: This loop can only be run once per EventManager, as it closes all of its control resources when it finishes.

Stepwise running

step :: EventManager -> TimeoutQueue -> IO (Bool, TimeoutQueue)

shutdown :: EventManager -> IO ()

Asynchronously shuts down the event manager, if running.

Registering interest in I/O events

data Event

An I/O event.

Instances

Eq Event

Show Event

Monoid Event

evtRead :: Event

Data is available to be read.

evtWrite :: Event

The file descriptor is ready to accept a write.

type IOCallback = FdKey -> Event -> IO ()

Callback invoked on I/O events.

data FdKey

A file descriptor registration cookie.

Instances

Eq FdKey

Show FdKey

registerFd :: EventManager -> IOCallback -> Fd -> Event -> IO FdKey

registerFd mgr cb fd evs registers interest in the events evs on the file descriptor fd. cb is called for each event that occurs. Returns a cookie that can be handed to unregisterFd.

registerFd_ :: EventManager -> IOCallback -> Fd -> Event -> IO (FdKey, Bool)

Register interest in the given events, without waking the event manager thread. The Bool return value indicates whether the event manager ought to be woken.

unregisterFd :: EventManager -> FdKey -> IO ()

Drop a previous file descriptor registration.

unregisterFd_ :: EventManager -> FdKey -> IO Bool

Drop a previous file descriptor registration, without waking the event manager thread. The return value indicates whether the event manager ought to be woken.

closeFd :: EventManager -> (Fd -> IO ()) -> Fd -> IO ()

Close a file descriptor in a race-safe way.

Registering interest in timeout events

type TimeoutCallback = IO ()

Callback invoked on timeout events.

data TimeoutKey

A timeout registration cookie.

Instances

Eq TimeoutKey

registerTimeout :: EventManager -> Int -> TimeoutCallback -> IO TimeoutKey

Register a timeout in the given number of microseconds. The returned TimeoutKey can be used to later unregister or update the timeout. The timeout is automatically unregistered after the given time has passed.

updateTimeout :: EventManager -> TimeoutKey -> Int -> IO ()

Update an active timeout to fire in the given number of microseconds.

unregisterTimeout :: EventManager -> TimeoutKey -> IO ()

Unregister an active timeout.