System.Linux.Epoll.Buffer

Buffer layer above epoll. Implemented using EventLoops. The general usage is that first an instance of Runtime is obtained, then one creates as many buffers as needed. Once done with a buffer, it has to be closed and finally the runtime should be shutdown, which kills the event loop, e.g.

 do r <- createRuntime (fromJust . toSize $ 4096)
    withIBuffer r stdInput $ \b ->
        readBuffer b >>= mapM_ print . take 10 . lines
    shutdownRuntime r

Please note that one has to close all buffers before calling shutdown on the runtime.

Documentation

data Runtime

Abstract data type for buffer runtime support.

createRuntime :: Size -> IO Runtime

Creates a runtime instance where size denotes the epoll device size (cf. create).

shutdownRuntime :: Runtime -> IO ()

Stops event processing and closes this runtime (and the underlying epoll device).

class BufElem a where

Buffer Element type class. Any instance of this class can be used as a buffer element.

Methods

beZero :: a

Zero element, e.g. empty string.

beConcat :: [a] -> a

Concatenates multiple elements.

beLength :: a -> Int

The length of one element.

beDrop :: Int -> a -> a

Returns element minus integer.

beWrite :: Fd -> a -> IO Int

Writes element to Fd, returns written length.

beRead :: Fd -> Int -> IO (a, Int)

Reads element of given length, returns element and actual length.

Instances

BufElem String

data IBuffer a

Buffer for reading after inEvent.

createIBuffer :: BufElem a => Runtime -> Fd -> IO (IBuffer a)

Create buffer for inEvents.

closeIBuffer :: BufElem a => Runtime -> IBuffer a -> IO ()

Close an IBuffer. Must not be called after shutdownRuntime has been invoked.

withIBuffer :: BufElem a => Runtime -> Fd -> (IBuffer a -> IO b) -> IO b

Exception safe wrapper which creates an IBuffer, passes it to the provided function and closes it afterwards.

data OBuffer a

Buffer for writing after outEvent.

createOBuffer :: BufElem a => Runtime -> Fd -> IO (OBuffer a)

Create Buffer for outEvents.

closeOBuffer :: BufElem a => Runtime -> OBuffer a -> IO ()

Close an OBuffer. Must not be called after shutdownRuntime has been invoked.

withOBuffer :: BufElem a => Runtime -> Fd -> (OBuffer a -> IO b) -> IO b

Exception safe wrapper which creates an OBuffer, passes it to the provided function and flushes and closes it afterwards.

readBuffer :: BufElem a => IBuffer a -> IO a

Blocking read. Lazily returns all available contents from IBuffer.

readAvail :: BufElem a => IBuffer a -> IO (Maybe a)

Non-Blocking read. Returns one chunk if available.

readChunk :: BufElem a => IBuffer a -> IO a

Blocking read. Returns one chunk from IBuffer.

writeBuffer :: BufElem a => OBuffer a -> a -> IO ()

Non-Blocking write. Writes value to buffer which will asynchronously be written to file descriptor.

flushBuffer :: OBuffer a -> IO ()

Blocks until buffer is emptied.