    {-# 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'.
    --
    -- Receiving data from closed socket may lead to undefined behaviour.
    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