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module Network.UCSPI where
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module Network.UCSPI
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( UCSPIOptions(..)
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, ucspiClient
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, ucspiServer
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) where
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import Control.Arrow (first)
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import Data.List (stripPrefix)
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import System.IO (Handle, h |
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import System.IO (Handle, hClose, hPutStrLn, stderr)
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import System.Posix.IO (fdToHandle)
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import System.Posix.Types (Fd(..))
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import System.Environment (getEnvironment)
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-- | The @UCSPI@ spec indicates that applications will receive information
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-- about their connection through environment variables. A 'UCSPIOptions'
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-- value will contains all the relevant values filtered out. As most of
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-- these (save for the protocol name) are prefixed with both the protocol
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-- name and either @LOCAL@ or @REMOTE@, those values are stripped before
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-- they are added to the respective lists: for example, if a @UCSPI@
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-- application for the @TCP@ protocol passes in an environment variable
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-- @TCPREMOTEPORT=7777@, then the value of 'ucspiProtocol' will be
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-- @TCP@ and 'ucspiRemoteVars' will contain a pair @(\"PORT\","7777")@.
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data UCSPIOptions = UCSPIOptions
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{ ucspiProtocol :: String
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, ucspiLocalVars :: [(String,String)]
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}
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-- | A @UCSPI@ client is passed an options value, a handle which corresponds
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-- to the reading end of a socket, and a handle which corresponds to the
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-- writing end of a socket. For example, a sample @UCSPI@ client which
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-- connects to a server, writes a line, and reads something back, regardless
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-- of the underlying transport mechanism, would look like
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--
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-- > main :: IO ()
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-- > main = ucspiClient $ \_ rdH wrH -> do
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-- > hPutStrLn wrH "hello"
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-- > ln <- hGetLine rdH
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-- > putStrLn ln
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ucspiClient :: (UCSPIOptions -> Handle -> Handle -> IO ()) -> IO ()
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ucspiClient client = do
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opts <- gatherOptions `fmap` getEnvironment
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rdH <- fdToHandle (Fd 6)
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wrH <- fdToHandle (Fd 7)
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client opts' rdH wrH
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hClose rdH
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hClose wrH
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-- | A @UCSPI@ server is passed only an options value. In order to read from or
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-- write to the connection, it just uses @stdin@ and @stdout@, which means that
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-- a server which reads a single line from a client and echoes it back would
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-- look like
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--
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-- > main :: IO ()
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-- > main = ucspiServer $ \_ -> getLine >>= putStrLn
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ucspiServer :: (UCSPIOptions -> IO ()) -> IO ()
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ucspiServer server = do
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opts <- gatherOptions `fmap` getEnvironment
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