Network/Socket/ByteString/Lazy.hs

{-# LANGUAGE CPP #-}

-- |
-- Module : Network.Socket.ByteString.Lazy
-- Copyright : (c) Bryan O'Sullivan 2009
-- License : BSD-style
--
-- Maintainer : bos@serpentine.com
-- Stability : experimental
-- Portability : POSIX, GHC
--
-- This module provides access to the BSD /socket/ interface. This
-- module is generally more efficient than the 'String' based network
-- functions in 'Network.Socket'. For detailed documentation, consult
-- your favorite POSIX socket reference. All functions communicate
-- failures by converting the error number to 'System.IO.IOError'.
--
-- This module is made to be imported with 'Network.Socket' like so:
--
-- > import Network.Socket hiding (send, sendTo, recv, recvFrom)
-- > import Network.Socket.ByteString.Lazy
-- > import Prelude hiding (getContents)
--
module Network.Socket.ByteString.Lazy
 (
 -- * Send data to a socket
 send
 , sendAll
 ,

 -- * Receive data from a socket
 getContents
 , recv
 ) where

import Control.Monad (liftM)
import Data.ByteString.Lazy.Internal (ByteString(..), defaultChunkSize)
import Data.Int (Int64)
import Network.Socket (Socket(..), ShutdownCmd(..), shutdown)
import Prelude hiding (getContents)
import System.IO.Unsafe (unsafeInterleaveIO)

import qualified Data.ByteString as S
import qualified Network.Socket.ByteString as N

#if defined(mingw32_HOST_OS)
import Network.Socket.ByteString.Lazy.Windows (send, sendAll)
#else
import Network.Socket.ByteString.Lazy.Posix (send, sendAll)
#endif

-- -----------------------------------------------------------------------------
-- Receiving

-- | Receive data from the socket. The socket must be in a connected
-- state. Data is received on demand, in chunks; each chunk will be
-- sized to reflect the amount of data received by individual 'recv'
-- calls.
--
-- All remaining data from the socket is consumed. When there is no
-- more data to be received, the receiving side of the socket is shut
-- down. If there is an error and an exception is thrown, the socket
-- is not shut down.
getContents :: Socket -- ^ Connected socket
 -> IO ByteString -- ^ Data received
getContents sock = loop where
 loop = unsafeInterleaveIO $ do
 s <- N.recv sock defaultChunkSize
 if S.null s
 then shutdown sock ShutdownReceive >> return Empty
 else Chunk s `liftM` loop

-- | Receive data from the socket. The socket must be in a connected
-- state. This function may return fewer bytes than specified. If
-- the received data is longer than the specified length, it may be
-- discarded depending on the type of socket. This function may block
-- until a message arrives.
--
-- If there is no more data to be received, returns an empty 'ByteString'.
recv :: Socket -- ^ Connected socket
 -> Int64 -- ^ Maximum number of bytes to receive
 -> IO ByteString -- ^ Data received
recv sock nbytes = chunk `liftM` N.recv sock (fromIntegral nbytes) where
 chunk k
 | S.null k = Empty
 | otherwise = Chunk k Empty