UnixSocket.hs

{-# LANGUAGE ScopedTypeVariables #-}

-- | This module provides convenience functions for interfacing unix-socket.
--
-- This module is only exported on platforms with
-- <https://en.wikipedia.org/wiki/Unix_domain_socket Unix domain socket> support.
--
-- This module is intended to be imported @qualified@, e.g.:
--
-- @
-- import           "Data.Connection"
-- import qualified "System.IO.Streams.UnixSocket" as UnixSocket
-- import qualified "System.IO.Streams.TCP"        as TCP
-- @
--
-- @since 1.0
--
module System.IO.Streams.UnixSocket
  ( -- * client
    connect
  , connectSocket
    -- * server
  , bindAndListen
  ) where

import qualified Control.Exception         as E
import qualified Network.Socket            as N
import qualified System.IO.Streams.TCP     as TCP

-- | Convenience function for initiating an raw TCP connection to the given
-- unix-socket file.
--
-- Note that sending an end-of-file to the returned 'OutputStream' will not
-- close the underlying Socket connection.
--
connectSocket :: String             -- ^ unix-socket to connect to
              -> IO (N.Socket, N.SockAddr)
connectSocket usock =
    E.bracketOnError (N.socket N.AF_UNIX N.Stream N.defaultProtocol)
                     N.close
                     (\sock -> do let addr = N.SockAddrUnix usock
                                  N.connect sock addr
                                  -- NoDelay causes an error for AF_UNIX, so we don't set
                                  -- default output buffer of unix socket is too small
                                  N.setSocketOption sock N.SendBuffer (TCP.defaultChunkSize * 16)
                                  return (sock, addr)
                     )

-- | Connect to unix-socket.
--
connect :: String             -- ^ unix-socket to connect to
        -> IO TCP.TCPConnection
connect usock = connectSocket usock >>= TCP.socketToConnection TCP.defaultChunkSize

-- | Bind and listen on a unix-socket with a limit on connection count.
--
-- Use 'TCP.accept' / 'TCP.acceptWith'  to accept new unix socket connections.
--
bindAndListen :: Int -> String -> IO N.Socket
bindAndListen maxc usock =
    E.bracketOnError
        (N.socket N.AF_UNIX N.Stream 0)
        N.close
        (\sock -> do N.setSocketOption sock N.SendBuffer (TCP.defaultChunkSize * 16)
                     N.bind sock (N.SockAddrUnix usock)
                     N.listen sock maxc
                     return sock
        )