System.Posix.Realtime.MQueue

POSIX 1003.1b message queue support.

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

mqOpen

Arguments

:: Name

-> OpenMode

-> Maybe FileMode

Just x => creates the file with the given modes, Nothing => the file must exist.

-> Maybe MQAttributes

-> IO Fd

Open and optionally create this message queue. See Files | for information on how to use the FileMode type. | Note: After referring to several mqueue implementations, it seems that the | POSIX standard doesn't tightly constrain Name's syntax. E.g. one Linux | implementation expects that Name starts with a "/". This is a warning | to the user. The author wasted a fair amount of time on this issue and | and doesn't wish this on others ...

mqClose :: Fd -> IO ()

Close a POSIX mqueue designated by "mqd"

mqUnlink :: String -> IO ()

Unlink (destroy) an existing POSIX mqueue designated by "name"

Sending/receiving data

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

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

Send a message on mqueue designated by "mqd"

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

Retrieve a message from mqueue designated by "mqd"

Getting/Setting mqueue attributes

mqGetAttributes :: Fd -> IO MQAttributes

Get the attributes for an existing POSIX message queue designated by | "mqd"

mqSetAttributes :: Fd -> MQAttributes -> IO MQAttributes

Set the attributes for an existing POSIX mqueue designated by "mqd" and | retrieve old attributes

Notify receipt of message

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

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