System.Posix.Realtime.MQueue

POSIX 1003.1b message queue support. See http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/mqueue.h.html.

Message queue attributes data type

data MQAttributes

Constructors

MQAttributes

Fields

flags :: Int

maxMsgNum :: Int

maxMsgSize :: Int

curNumMsgs :: Int

Instances

Show MQAttributes

Storable MQAttributes

MQAttributes Storable used to marshall and unmarshall to ANSI C

Opening/closing/unlinking mqueues

type Name = String

mqOpen

Arguments

:: Name

-> OpenMode

-> Maybe FileMode

Just x creates the queue with the given modes, Nothing then the file must exist.

-> Maybe MQAttributes

Just x creates the queue with given attributes, Nothing with default attributes.

-> IO Fd

Open and optionally create a message queue

Note: The POSIX standard puts some constraints on Name but leaves much as "implementation-defined", meaning that one needs to read the system-specific details on what a conforming name should look like.

mqClose :: Fd -> IO ()

Close a message queue

mqUnlink :: String -> IO ()

Unlink (destroy) an existing message queue

Sending/receiving data

Programmers using the mqSend and mqReceive API should be aware that EAGAIN exceptions may occur for non-blocking IO!

mqSend :: Fd -> ByteString -> ByteCount -> Int -> IO ()

Send a message on a message queue

mqReceive :: Fd -> ByteCount -> Maybe Int -> IO (ByteString, Int)

Retrieve a message from a message queue

Note: mq_timedreceive is not exposed, wrap mqReceive in timeout to get a timed receive.

Getting/Setting mqueue attributes

mqGetAttributes :: Fd -> IO MQAttributes

Get the attributes for an existing message queue

mqSetAttributes :: Fd -> MQAttributes -> IO MQAttributes

Set the attributes for an existing message queue and its retrieve old attributes

Notify receipt of message

mqNotify :: Fd -> Maybe Sigevent -> IO ()

Notify a registered process of the new-message-in-empty-queue event