Socket.hsc

{-# LANGUAGE CPP #-}
-----------------------------------------------------------------------------
-- |
-- Module      :  Network.Socket
-- Copyright   :  (c) The University of Glasgow 2001
-- License     :  BSD-style (see the file libraries/network/LICENSE)
-- 
-- Maintainer  :  libraries@haskell.org
-- Stability   :  provisional
-- Portability :  portable
--
-- The "Network.Socket" module is for when you want full control over
-- sockets.  Essentially the entire C socket API is exposed through
-- this module; in general the operations follow the behaviour of the C
-- functions of the same name (consult your favourite Unix networking book).
--
-- A higher level interface to networking operations is provided
-- through the module "Network".
--
-----------------------------------------------------------------------------

#include "HsNet.h"

-- NOTE: ##, we want this interpreted when compiling the .hs, not by hsc2hs.
##include "Typeable.h"

-- In order to process this file, you need to have CALLCONV defined.

module Network.Socket
    (
    -- * Types
      Socket(..)
    , Family(..)         
    , SocketType(..)
    , SockAddr(..)
    , SocketStatus(..)
    , HostAddress
#if defined(IPV6_SOCKET_SUPPORT)
    , HostAddress6
    , FlowInfo
    , ScopeID
#endif
    , ShutdownCmd(..)
    , ProtocolNumber
    , defaultProtocol
    , PortNumber(..)
    -- PortNumber is used non-abstractly in Network.BSD.  ToDo: remove
    -- this use and make the type abstract.

    -- * Address operations

    , HostName
    , ServiceName

#if defined(IPV6_SOCKET_SUPPORT)
    , AddrInfo(..)

    , AddrInfoFlag(..)
    , addrInfoFlagImplemented

    , defaultHints

    , getAddrInfo

    , NameInfoFlag(..)

    , getNameInfo
#endif

    -- * Socket operations
    , socket
#if defined(DOMAIN_SOCKET_SUPPORT)
    , socketPair
#endif
    , connect
    , bindSocket
    , listen
    , accept
    , getPeerName
    , getSocketName

#ifdef HAVE_STRUCT_UCRED
    -- get the credentials of our domain socket peer.
    , getPeerCred
#endif

    , socketPort

    , socketToHandle

    -- ** Sending and receiving data
    -- $sendrecv
    , sendTo
    , sendBufTo

    , recvFrom
    , recvBufFrom
    
    , send
    , recv
    , recvLen

    , inet_addr
    , inet_ntoa

    , shutdown
    , sClose

    -- ** Predicates on sockets
    , sIsConnected
    , sIsBound
    , sIsListening
    , sIsReadable
    , sIsWritable

    -- * Socket options
    , SocketOption(..)
    , getSocketOption
    , setSocketOption

    -- * File descriptor transmission
#ifdef DOMAIN_SOCKET_SUPPORT
    , sendFd
    , recvFd

    -- Note: these two will disappear shortly
    , sendAncillary
    , recvAncillary

#endif

    -- * Special constants
    , aNY_PORT
    , iNADDR_ANY
#if defined(IPV6_SOCKET_SUPPORT)
    , iN6ADDR_ANY
#endif
    , sOMAXCONN
    , sOL_SOCKET
#ifdef SCM_RIGHTS
    , sCM_RIGHTS
#endif
    , maxListenQueue

    -- * Initialisation
    , withSocketsDo
    
    -- * Very low level operations
    -- in case you ever want to get at the underlying file descriptor..
    , fdSocket
    , mkSocket

    -- * Internal

    -- | The following are exported ONLY for use in the BSD module and
    -- should not be used anywhere else.

    , packFamily
    , unpackFamily
    , packSocketType
    , throwSocketErrorIfMinus1_
    ) where

#ifdef __HUGS__
import Hugs.Prelude ( IOException(..), IOErrorType(..) )
import Hugs.IO ( openFd )

{-# CFILES cbits/HsNet.c #-}
# if HAVE_STRUCT_MSGHDR_MSG_CONTROL || HAVE_STRUCT_MSGHDR_MSG_ACCRIGHTS
{-# CFILES cbits/ancilData.c #-}
# endif
# if defined(HAVE_WINSOCK2_H) && !defined(__CYGWIN__)
{-# CFILES cbits/initWinSock.c cbits/winSockErr.c #-}
# endif
#endif

import Data.Bits
import Data.List (foldl')
import Data.Word (Word8, Word16, Word32)
import Foreign.Ptr (Ptr, castPtr, nullPtr, plusPtr)
import Foreign.Storable (Storable(..))
import Foreign.C.Error
import Foreign.C.String (CString, withCString, peekCString, peekCStringLen,
                        castCharToCChar)
import Foreign.C.Types (CUInt, CChar)
#if __GLASGOW_HASKELL__ >= 703
import Foreign.C.Types (CInt(..), CSize(..))
#else
import Foreign.C.Types (CInt, CSize)
#endif
import Foreign.Marshal.Alloc ( alloca, allocaBytes )
import Foreign.Marshal.Array ( peekArray, pokeArray, pokeArray0 )
import Foreign.Marshal.Utils ( maybeWith, with )

import System.IO
import Control.Monad (liftM, when)
import Data.Ratio ((%))

import qualified Control.Exception
import Control.Concurrent.MVar
import Data.Typeable
import System.IO.Error

#ifdef __GLASGOW_HASKELL__
import GHC.Conc (threadWaitRead, threadWaitWrite)
##if MIN_VERSION_base(4,3,1)
import GHC.Conc (closeFdWith)
##endif
# if defined(mingw32_HOST_OS)
import GHC.Conc (asyncDoProc)
import Foreign (FunPtr)
# endif
# if __GLASGOW_HASKELL__ >= 611
import qualified GHC.IO.Device
import GHC.IO.Handle.FD
import GHC.IO.Exception
import GHC.IO
# else
import GHC.IOBase
import GHC.Handle
# endif
import qualified System.Posix.Internals
#else
import System.IO.Unsafe (unsafePerformIO)
#endif

# if __GLASGOW_HASKELL__ >= 611
import GHC.IO.FD
#endif

import Network.Socket.Internal

-- | Either a host name e.g., @\"haskell.org\"@ or a numeric host
-- address string consisting of a dotted decimal IPv4 address or an
-- IPv6 address e.g., @\"192.168.0.1\"@.
type HostName       = String
type ServiceName    = String

-- ----------------------------------------------------------------------------
-- On Windows, our sockets are not put in non-blocking mode (non-blocking
-- is not supported for regular file descriptors on Windows, and it would
-- be a pain to support it only for sockets).  So there are two cases:
--
--  - the threaded RTS uses safe calls for socket operations to get
--    non-blocking I/O, just like the rest of the I/O library
--
--  - with the non-threaded RTS, only some operations on sockets will be
--    non-blocking.  Reads and writes go through the normal async I/O
--    system.  accept() uses asyncDoProc so is non-blocking.  A handful
--    of others (recvFrom, sendFd, recvFd) will block all threads - if this
--    is a problem, -threaded is the workaround.
--
##if defined(mingw32_HOST_OS)
##define SAFE_ON_WIN safe
##else
##define SAFE_ON_WIN unsafe
##endif

-----------------------------------------------------------------------------
-- Socket types

-- There are a few possible ways to do this.  The first is convert the
-- structs used in the C library into an equivalent Haskell type. An
-- other possible implementation is to keep all the internals in the C
-- code and use an Int## and a status flag. The second method is used
-- here since a lot of the C structures are not required to be
-- manipulated.

-- Originally the status was non-mutable so we had to return a new
-- socket each time we changed the status.  This version now uses
-- mutable variables to avoid the need to do this.  The result is a
-- cleaner interface and better security since the application
-- programmer now can't circumvent the status information to perform
-- invalid operations on sockets.

data SocketStatus
  -- Returned Status    Function called
  = NotConnected        -- socket
  | Bound               -- bindSocket
  | Listening           -- listen
  | Connected           -- connect/accept
  | ConvertedToHandle   -- is now a Handle, don't touch
  | Closed              -- sClose 
    deriving (Eq, Show, Typeable)

data Socket
  = MkSocket
            CInt                 -- File Descriptor
            Family                                
            SocketType                            
            ProtocolNumber       -- Protocol Number
            (MVar SocketStatus)  -- Status Flag
  deriving Typeable

#if __GLASGOW_HASKELL__ >= 611 && defined(mingw32_HOST_OS)
socket2FD  (MkSocket fd _ _ _ _) = 
  -- HACK, 1 means True 
  FD{fdFD = fd,fdIsSocket_ = 1} 
#endif

mkSocket :: CInt
         -> Family
         -> SocketType
         -> ProtocolNumber
         -> SocketStatus
         -> IO Socket
mkSocket fd fam sType pNum stat = do
   mStat <- newMVar stat
   return (MkSocket fd fam sType pNum mStat)

instance Eq Socket where
  (MkSocket _ _ _ _ m1) == (MkSocket _ _ _ _ m2) = m1 == m2

instance Show Socket where
  showsPrec n (MkSocket fd _ _ _ _) = 
        showString "<socket: " . shows fd . showString ">"


fdSocket :: Socket -> CInt
fdSocket (MkSocket fd _ _ _ _) = fd

type ProtocolNumber = CInt

-- | This is the default protocol for a given service.
defaultProtocol :: ProtocolNumber
defaultProtocol = 0

----------------------------------------------------------------------------
-- Port Numbers

instance Show PortNumber where
  showsPrec p pn = showsPrec p (portNumberToInt pn)

intToPortNumber :: Int -> PortNumber
intToPortNumber v = PortNum (htons (fromIntegral v))

portNumberToInt :: PortNumber -> Int
portNumberToInt (PortNum po) = fromIntegral (ntohs po)

foreign import CALLCONV unsafe "ntohs" ntohs :: Word16 -> Word16
foreign import CALLCONV unsafe "htons" htons :: Word16 -> Word16
--foreign import CALLCONV unsafe "ntohl" ntohl :: Word32 -> Word32
foreign import CALLCONV unsafe "htonl" htonl :: Word32 -> Word32

instance Enum PortNumber where
    toEnum   = intToPortNumber
    fromEnum = portNumberToInt

instance Num PortNumber where
   fromInteger i = intToPortNumber (fromInteger i)
    -- for completeness.
   (+) x y   = intToPortNumber (portNumberToInt x + portNumberToInt y)
   (-) x y   = intToPortNumber (portNumberToInt x - portNumberToInt y)
   negate x  = intToPortNumber (-portNumberToInt x)
   (*) x y   = intToPortNumber (portNumberToInt x * portNumberToInt y)
   abs n     = intToPortNumber (abs (portNumberToInt n))
   signum n  = intToPortNumber (signum (portNumberToInt n))

instance Real PortNumber where
    toRational x = toInteger x % 1

instance Integral PortNumber where
    quotRem a b = let (c,d) = quotRem (portNumberToInt a) (portNumberToInt b) in
                  (intToPortNumber c, intToPortNumber d)
    toInteger a = toInteger (portNumberToInt a)

instance Storable PortNumber where
   sizeOf    _ = sizeOf    (undefined :: Word16)
   alignment _ = alignment (undefined :: Word16)
   poke p (PortNum po) = poke (castPtr p) po
   peek p = PortNum `liftM` peek (castPtr p)

-----------------------------------------------------------------------------
-- SockAddr

instance Show SockAddr where
#if defined(DOMAIN_SOCKET_SUPPORT)
  showsPrec _ (SockAddrUnix str) = showString str
#endif
  showsPrec _ (SockAddrInet port ha)
   = showString (unsafePerformIO (inet_ntoa ha)) 
   . showString ":"
   . shows port
#if defined(IPV6_SOCKET_SUPPORT)
  showsPrec _ addr@(SockAddrInet6 port _ _ _)
   = showChar '['
   . showString (unsafePerformIO $
                 fst `liftM` getNameInfo [NI_NUMERICHOST] True False addr >>=
                 maybe (fail "showsPrec: impossible internal error") return)
   . showString "]:"
   . shows port
#endif

-----------------------------------------------------------------------------
-- Connection Functions

-- In the following connection and binding primitives.  The names of
-- the equivalent C functions have been preserved where possible. It
-- should be noted that some of these names used in the C library,
-- \tr{bind} in particular, have a different meaning to many Haskell
-- programmers and have thus been renamed by appending the prefix
-- Socket.

-- | Create a new socket using the given address family, socket type
-- and protocol number.  The address family is usually 'AF_INET',
-- 'AF_INET6', or 'AF_UNIX'.  The socket type is usually 'Stream' or
-- 'Datagram'.  The protocol number is usually 'defaultProtocol'.
-- If 'AF_INET6' is used, the 'IPv6Only' socket option is set to 0
-- so that both IPv4 and IPv6 can be handled with one socket.
socket :: Family         -- Family Name (usually AF_INET)
       -> SocketType     -- Socket Type (usually Stream)
       -> ProtocolNumber -- Protocol Number (getProtocolByName to find value)
       -> IO Socket      -- Unconnected Socket
socket family stype protocol = do
    fd <- throwSocketErrorIfMinus1Retry "socket" $
                c_socket (packFamily family) (packSocketType stype) protocol
#if !defined(__HUGS__)
# if __GLASGOW_HASKELL__ < 611
    System.Posix.Internals.setNonBlockingFD fd
# else
    System.Posix.Internals.setNonBlockingFD fd True
# endif
#endif
    socket_status <- newMVar NotConnected
    let sock = MkSocket fd family stype protocol socket_status
#if HAVE_DECL_IPV6_V6ONLY
    when (family == AF_INET6) $ setSocketOption sock IPv6Only 0
#endif
    return sock

-- | Build a pair of connected socket objects using the given address
-- family, socket type, and protocol number.  Address family, socket
-- type, and protocol number are as for the 'socket' function above.
-- Availability: Unix.
#if defined(DOMAIN_SOCKET_SUPPORT)
socketPair :: Family              -- Family Name (usually AF_INET or AF_INET6)
           -> SocketType          -- Socket Type (usually Stream)
           -> ProtocolNumber      -- Protocol Number
           -> IO (Socket, Socket) -- unnamed and connected.
socketPair family stype protocol = do
    allocaBytes (2 * sizeOf (1 :: CInt)) $ \ fdArr -> do
    rc <- throwSocketErrorIfMinus1Retry "socketpair" $
                c_socketpair (packFamily family)
                             (packSocketType stype)
                             protocol fdArr
    [fd1,fd2] <- peekArray 2 fdArr 
    s1 <- mkSocket fd1
    s2 <- mkSocket fd2
    return (s1,s2)
  where
    mkSocket fd = do
#if !defined(__HUGS__)
# if __GLASGOW_HASKELL__ < 611
       System.Posix.Internals.setNonBlockingFD fd
# else
       System.Posix.Internals.setNonBlockingFD fd True
# endif
#endif
       stat <- newMVar Connected
       return (MkSocket fd family stype protocol stat)

foreign import ccall unsafe "socketpair"
  c_socketpair :: CInt -> CInt -> CInt -> Ptr CInt -> IO CInt
#endif

-----------------------------------------------------------------------------
-- Binding a socket

-- | Bind the socket to an address. The socket must not already be
-- bound.  The 'Family' passed to @bindSocket@ must be the
-- same as that passed to 'socket'.  If the special port number
-- 'aNY_PORT' is passed then the system assigns the next available
-- use port.
bindSocket :: Socket    -- Unconnected Socket
           -> SockAddr  -- Address to Bind to
           -> IO ()
bindSocket (MkSocket s _family _stype _protocol socketStatus) addr = do
 modifyMVar_ socketStatus $ \ status -> do
 if status /= NotConnected 
  then
   ioError (userError ("bindSocket: can't peform bind on socket in status " ++
         show status))
  else do
   withSockAddr addr $ \p_addr sz -> do
   status <- throwSocketErrorIfMinus1Retry "bind" $ c_bind s p_addr (fromIntegral sz)
   return Bound

-----------------------------------------------------------------------------
-- Connecting a socket

-- | Connect to a remote socket at address.
connect :: Socket    -- Unconnected Socket
        -> SockAddr  -- Socket address stuff
        -> IO ()
connect sock@(MkSocket s _family _stype _protocol socketStatus) addr = do
 modifyMVar_ socketStatus $ \currentStatus -> do
 if currentStatus /= NotConnected && currentStatus /= Bound
  then
    ioError (userError ("connect: can't peform connect on socket in status " ++
        show currentStatus))
  else do
    withSockAddr addr $ \p_addr sz -> do

    let connectLoop = do
           r <- c_connect s p_addr (fromIntegral sz)
           if r == -1
               then do 
#if !(defined(HAVE_WINSOCK2_H) && !defined(cygwin32_HOST_OS))
                   err <- getErrno
                   case () of
                     _ | err == eINTR       -> connectLoop
                     _ | err == eINPROGRESS -> connectBlocked
--                   _ | err == eAGAIN      -> connectBlocked
                     otherwise              -> throwSocketError "connect"
#else
                   rc <- c_getLastError
                   case rc of
                     10093 -> do -- WSANOTINITIALISED
                       withSocketsDo (return ())
                       r <- c_connect s p_addr (fromIntegral sz)
                       if r == -1
                         then throwSocketError "connect"
                         else return r
                     _ -> throwSocketError "connect"
#endif
               else return r

        connectBlocked = do 
#if !defined(__HUGS__)
           threadWaitWrite (fromIntegral s)
#endif
           err <- getSocketOption sock SoError
           if (err == 0)
                then return 0
                else do ioError (errnoToIOError "connect" 
                                (Errno (fromIntegral err))
                                Nothing Nothing)

    connectLoop
    return Connected

-----------------------------------------------------------------------------
-- Listen

-- | Listen for connections made to the socket.  The second argument
-- specifies the maximum number of queued connections and should be at
-- least 1; the maximum value is system-dependent (usually 5).
listen :: Socket  -- Connected & Bound Socket
       -> Int     -- Queue Length
       -> IO ()
listen (MkSocket s _family _stype _protocol socketStatus) backlog = do
 modifyMVar_ socketStatus $ \ status -> do
 if status /= Bound 
   then
     ioError (userError ("listen: can't peform listen on socket in status " ++
         show status))
   else do
     throwSocketErrorIfMinus1Retry "listen" (c_listen s (fromIntegral backlog))
     return Listening

-----------------------------------------------------------------------------
-- Accept
--
-- A call to `accept' only returns when data is available on the given
-- socket, unless the socket has been set to non-blocking.  It will
-- return a new socket which should be used to read the incoming data and
-- should then be closed. Using the socket returned by `accept' allows
-- incoming requests to be queued on the original socket.

-- | Accept a connection.  The socket must be bound to an address and
-- listening for connections.  The return value is a pair @(conn,
-- address)@ where @conn@ is a new socket object usable to send and
-- receive data on the connection, and @address@ is the address bound
-- to the socket on the other end of the connection.
accept :: Socket                        -- Queue Socket
       -> IO (Socket,                   -- Readable Socket
              SockAddr)                 -- Peer details

accept sock@(MkSocket s family stype protocol status) = do
 currentStatus <- readMVar status
 okay <- sIsAcceptable sock
 if not okay
   then
     ioError (userError ("accept: can't perform accept on socket (" ++ (show (family,stype,protocol)) ++") in status " ++
         show currentStatus))
   else do
     let sz = sizeOfSockAddrByFamily family
     allocaBytes sz $ \ sockaddr -> do
#if defined(mingw32_HOST_OS) && defined(__GLASGOW_HASKELL__)
     new_sock <-
        if threaded 
           then with (fromIntegral sz) $ \ ptr_len ->
                  throwErrnoIfMinus1Retry "Network.Socket.accept" $
                    c_accept_safe s sockaddr ptr_len
           else do
                paramData <- c_newAcceptParams s (fromIntegral sz) sockaddr
                rc        <- asyncDoProc c_acceptDoProc paramData
                new_sock  <- c_acceptNewSock    paramData
                c_free paramData
                when (rc /= 0)
                     (ioError (errnoToIOError "Network.Socket.accept" (Errno (fromIntegral rc)) Nothing Nothing))
                return new_sock
#else 
     with (fromIntegral sz) $ \ ptr_len -> do
     new_sock <- 
# if !defined(__HUGS__)
                 throwSocketErrorIfMinus1RetryMayBlock "accept"
                        (threadWaitRead (fromIntegral s))
# endif
                        (c_accept s sockaddr ptr_len)
# if !defined(__HUGS__)
#  if __GLASGOW_HASKELL__ < 611
     System.Posix.Internals.setNonBlockingFD new_sock
#  else
     System.Posix.Internals.setNonBlockingFD new_sock True
#  endif
# endif
#endif
     addr <- peekSockAddr sockaddr
     new_status <- newMVar Connected
     return ((MkSocket new_sock family stype protocol new_status), addr)

#if defined(mingw32_HOST_OS) && !defined(__HUGS__)
foreign import ccall unsafe "HsNet.h acceptNewSock"
  c_acceptNewSock :: Ptr () -> IO CInt
foreign import ccall unsafe "HsNet.h newAcceptParams"
  c_newAcceptParams :: CInt -> CInt -> Ptr a -> IO (Ptr ())
foreign import ccall unsafe "HsNet.h &acceptDoProc"
  c_acceptDoProc :: FunPtr (Ptr () -> IO Int)
foreign import ccall unsafe "free"
  c_free:: Ptr a -> IO ()
#endif

-----------------------------------------------------------------------------
-- ** Sending and reciving data

-- $sendrecv
--
-- Do not use the @send@ and @recv@ functions defined in this module
-- in new code, as they incorrectly represent binary data as a Unicode
-- string.  As a result, these functions are inefficient and may lead
-- to bugs in the program.  Instead use the @send@ and @recv@
-- functions defined in the 'Network.Socket.ByteString' module.

-----------------------------------------------------------------------------
-- sendTo & recvFrom

-- | Send data to the socket.  The recipient can be specified
-- explicitly, so the socket need not be in a connected state.
-- Returns the number of bytes sent.  Applications are responsible for
-- ensuring that all data has been sent.
--
-- NOTE: blocking on Windows unless you compile with -threaded (see
-- GHC ticket #1129)
sendTo :: Socket        -- (possibly) bound/connected Socket
       -> String        -- Data to send
       -> SockAddr
       -> IO Int        -- Number of Bytes sent
sendTo sock xs addr = do
 withCString xs $ \str -> do
   sendBufTo sock str (length xs) addr

-- | Send data to the socket.  The recipient can be specified
-- explicitly, so the socket need not be in a connected state.
-- Returns the number of bytes sent.  Applications are responsible for
-- ensuring that all data has been sent.
sendBufTo :: Socket            -- (possibly) bound/connected Socket
          -> Ptr a -> Int  -- Data to send
          -> SockAddr
          -> IO Int            -- Number of Bytes sent
sendBufTo (MkSocket s _family _stype _protocol status) ptr nbytes addr = do
 withSockAddr addr $ \p_addr sz -> do
   liftM fromIntegral $
#if !defined(__HUGS__)
     throwSocketErrorIfMinus1RetryMayBlock "sendTo"
        (threadWaitWrite (fromIntegral s)) $
#endif
        c_sendto s ptr (fromIntegral $ nbytes) 0{-flags-} 
                        p_addr (fromIntegral sz)

-- | Receive data from the socket. The socket need not be in a
-- connected state. Returns @(bytes, nbytes, address)@ where @bytes@
-- is a @String@ of length @nbytes@ representing the data received and
-- @address@ is a 'SockAddr' representing the address of the sending
-- socket.
--
-- NOTE: blocking on Windows unless you compile with -threaded (see
-- GHC ticket #1129)
recvFrom :: Socket -> Int -> IO (String, Int, SockAddr)
recvFrom sock nbytes =
  allocaBytes nbytes $ \ptr -> do
    (len, sockaddr) <- recvBufFrom sock ptr nbytes
    str <- peekCStringLen (ptr, len)
    return (str, len, sockaddr)

-- | Receive data from the socket, writing it into buffer instead of
-- creating a new string.  The socket need not be in a connected
-- state. Returns @(nbytes, address)@ where @nbytes@ is the number of
-- bytes received and @address@ is a 'SockAddr' representing the
-- address of the sending socket.
--
-- NOTE: blocking on Windows unless you compile with -threaded (see
-- GHC ticket #1129)
recvBufFrom :: Socket -> Ptr a -> Int -> IO (Int, SockAddr)
recvBufFrom sock@(MkSocket s family _stype _protocol status) ptr nbytes
 | nbytes <= 0 = ioError (mkInvalidRecvArgError "Network.Socket.recvFrom")
 | otherwise   = 
    withNewSockAddr family $ \ptr_addr sz -> do
      alloca $ \ptr_len -> do
        poke ptr_len (fromIntegral sz)
        len <- 
#if !defined(__HUGS__)
               throwSocketErrorIfMinus1RetryMayBlock "recvFrom"
                   (threadWaitRead (fromIntegral s)) $
#endif
                   c_recvfrom s ptr (fromIntegral nbytes) 0{-flags-} 
                                ptr_addr ptr_len
        let len' = fromIntegral len
        if len' == 0
         then ioError (mkEOFError "Network.Socket.recvFrom")
         else do
           flg <- sIsConnected sock
             -- For at least one implementation (WinSock 2), recvfrom() ignores
             -- filling in the sockaddr for connected TCP sockets. Cope with 
             -- this by using getPeerName instead.
           sockaddr <- 
                if flg then
                   getPeerName sock
                else
                   peekSockAddr ptr_addr 
           return (len', sockaddr)

-----------------------------------------------------------------------------
-- send & recv

-- | Send data to the socket. The socket must be connected to a remote
-- socket. Returns the number of bytes sent.  Applications are
-- responsible for ensuring that all data has been sent.
send :: Socket  -- Bound/Connected Socket
     -> String  -- Data to send
     -> IO Int  -- Number of Bytes sent
send sock@(MkSocket s _family _stype _protocol status) xs = do
 let len = length xs
 withCString xs $ \str -> do
   liftM fromIntegral $
#if defined(__GLASGOW_HASKELL__) && defined(mingw32_HOST_OS)
# if __GLASGOW_HASKELL__ >= 611    
    writeRawBufferPtr 
      "Network.Socket.send" 
      (socket2FD sock)
      (castPtr str)
      0
      (fromIntegral len)
#else      
      writeRawBufferPtr 
        "Network.Socket.send" 
        (fromIntegral s) 
        True 
        str 
        0 
       (fromIntegral len)
#endif    
    
#else
# if !defined(__HUGS__)
     throwSocketErrorIfMinus1RetryMayBlock "send"
        (threadWaitWrite (fromIntegral s)) $
# endif
        c_send s str (fromIntegral len) 0{-flags-} 
#endif

-- | Receive data from the socket.  The socket must be in a connected
-- state. This function may return fewer bytes than specified.  If the
-- message is longer than the specified length, it may be discarded
-- depending on the type of socket.  This function may block until a
-- message arrives.
--
-- Considering hardware and network realities, the maximum number of
-- bytes to receive should be a small power of 2, e.g., 4096.
--
-- For TCP sockets, a zero length return value means the peer has
-- closed its half side of the connection.
recv :: Socket -> Int -> IO String
recv sock l = recvLen sock l >>= \ (s,_) -> return s

recvLen :: Socket -> Int -> IO (String, Int)
recvLen sock@(MkSocket s _family _stype _protocol status) nbytes 
 | nbytes <= 0 = ioError (mkInvalidRecvArgError "Network.Socket.recv")
 | otherwise   = do
     allocaBytes nbytes $ \ptr -> do
        len <- 
#if defined(__GLASGOW_HASKELL__) && defined(mingw32_HOST_OS)
# if __GLASGOW_HASKELL__ >= 611    
          readRawBufferPtr "Network.Socket.recvLen" (socket2FD sock) ptr 0
                 (fromIntegral nbytes)
#else          
          readRawBufferPtr "Network.Socket.recvLen" (fromIntegral s) True ptr 0
                 (fromIntegral nbytes)
#endif
#else
# if !defined(__HUGS__)
               throwSocketErrorIfMinus1RetryMayBlock "recv"
                   (threadWaitRead (fromIntegral s)) $
# endif
                   c_recv s ptr (fromIntegral nbytes) 0{-flags-} 
#endif
        let len' = fromIntegral len
        if len' == 0
         then ioError (mkEOFError "Network.Socket.recv")
         else do
           s <- peekCStringLen (castPtr ptr,len')
           return (s, len')

-- ---------------------------------------------------------------------------
-- socketPort
--
-- The port number the given socket is currently connected to can be
-- determined by calling $port$, is generally only useful when bind
-- was given $aNY\_PORT$.

socketPort :: Socket            -- Connected & Bound Socket
           -> IO PortNumber     -- Port Number of Socket
socketPort sock@(MkSocket _ AF_INET _ _ _) = do
    (SockAddrInet port _) <- getSocketName sock
    return port
#if defined(IPV6_SOCKET_SUPPORT)
socketPort sock@(MkSocket _ AF_INET6 _ _ _) = do
    (SockAddrInet6 port _ _ _) <- getSocketName sock
    return port
#endif
socketPort (MkSocket _ family _ _ _) =
    ioError (userError ("socketPort: not supported for Family " ++ show family))


-- ---------------------------------------------------------------------------
-- getPeerName

-- Calling $getPeerName$ returns the address details of the machine,
-- other than the local one, which is connected to the socket. This is
-- used in programs such as FTP to determine where to send the
-- returning data.  The corresponding call to get the details of the
-- local machine is $getSocketName$.

getPeerName   :: Socket -> IO SockAddr
getPeerName (MkSocket s family _ _ _) = do
 withNewSockAddr family $ \ptr sz -> do
   with (fromIntegral sz) $ \int_star -> do
   throwSocketErrorIfMinus1Retry "getPeerName" $ c_getpeername s ptr int_star
   sz <- peek int_star
   peekSockAddr ptr
    
getSocketName :: Socket -> IO SockAddr
getSocketName (MkSocket s family _ _ _) = do
 withNewSockAddr family $ \ptr sz -> do
   with (fromIntegral sz) $ \int_star -> do
   throwSocketErrorIfMinus1Retry "getSocketName" $ c_getsockname s ptr int_star
   peekSockAddr ptr

-----------------------------------------------------------------------------
-- Socket Properties

data SocketOption
    = DummySocketOption__
#ifdef SO_DEBUG
    | Debug         {- SO_DEBUG     -}
#endif
#ifdef SO_REUSEADDR
    | ReuseAddr     {- SO_REUSEADDR -}
#endif
#ifdef SO_TYPE
    | Type          {- SO_TYPE      -}
#endif
#ifdef SO_ERROR
    | SoError       {- SO_ERROR     -}
#endif
#ifdef SO_DONTROUTE
    | DontRoute     {- SO_DONTROUTE -}
#endif
#ifdef SO_BROADCAST
    | Broadcast     {- SO_BROADCAST -}
#endif
#ifdef SO_SNDBUF
    | SendBuffer    {- SO_SNDBUF    -}
#endif
#ifdef SO_RCVBUF
    | RecvBuffer    {- SO_RCVBUF    -}
#endif
#ifdef SO_KEEPALIVE
    | KeepAlive     {- SO_KEEPALIVE -}
#endif
#ifdef SO_OOBINLINE
    | OOBInline     {- SO_OOBINLINE -}
#endif
#ifdef IP_TTL
    | TimeToLive    {- IP_TTL       -}
#endif
#ifdef TCP_MAXSEG
    | MaxSegment    {- TCP_MAXSEG   -}
#endif
#ifdef TCP_NODELAY
    | NoDelay       {- TCP_NODELAY  -}
#endif
#ifdef SO_LINGER
    | Linger        {- SO_LINGER    -}
#endif
#ifdef SO_REUSEPORT
    | ReusePort     {- SO_REUSEPORT -}
#endif
#ifdef SO_RCVLOWAT
    | RecvLowWater  {- SO_RCVLOWAT  -}
#endif
#ifdef SO_SNDLOWAT
    | SendLowWater  {- SO_SNDLOWAT  -}
#endif
#ifdef SO_RCVTIMEO
    | RecvTimeOut   {- SO_RCVTIMEO  -}
#endif
#ifdef SO_SNDTIMEO
    | SendTimeOut   {- SO_SNDTIMEO  -}
#endif
#ifdef SO_USELOOPBACK
    | UseLoopBack   {- SO_USELOOPBACK -}
#endif
#if HAVE_DECL_IPV6_V6ONLY
    | IPv6Only      {- IPV6_V6ONLY -}
#endif
    deriving Typeable

socketOptLevel :: SocketOption -> CInt
socketOptLevel so = 
  case so of
#ifdef IP_TTL
    TimeToLive   -> #const IPPROTO_IP
#endif
#ifdef TCP_MAXSEG
    MaxSegment   -> #const IPPROTO_TCP
#endif
#ifdef TCP_NODELAY
    NoDelay      -> #const IPPROTO_TCP
#endif
#if HAVE_DECL_IPV6_V6ONLY
    IPv6Only     -> #const IPPROTO_IPV6
#endif
    _            -> #const SOL_SOCKET

packSocketOption :: SocketOption -> CInt
packSocketOption so =
  case so of
#ifdef SO_DEBUG
    Debug         -> #const SO_DEBUG
#endif
#ifdef SO_REUSEADDR
    ReuseAddr     -> #const SO_REUSEADDR
#endif
#ifdef SO_TYPE
    Type          -> #const SO_TYPE
#endif
#ifdef SO_ERROR
    SoError       -> #const SO_ERROR
#endif
#ifdef SO_DONTROUTE
    DontRoute     -> #const SO_DONTROUTE
#endif
#ifdef SO_BROADCAST
    Broadcast     -> #const SO_BROADCAST
#endif
#ifdef SO_SNDBUF
    SendBuffer    -> #const SO_SNDBUF
#endif
#ifdef SO_RCVBUF
    RecvBuffer    -> #const SO_RCVBUF
#endif
#ifdef SO_KEEPALIVE
    KeepAlive     -> #const SO_KEEPALIVE
#endif
#ifdef SO_OOBINLINE
    OOBInline     -> #const SO_OOBINLINE
#endif
#ifdef IP_TTL
    TimeToLive    -> #const IP_TTL
#endif
#ifdef TCP_MAXSEG
    MaxSegment    -> #const TCP_MAXSEG
#endif
#ifdef TCP_NODELAY
    NoDelay       -> #const TCP_NODELAY
#endif
#ifdef SO_LINGER
    Linger        -> #const SO_LINGER
#endif
#ifdef SO_REUSEPORT
    ReusePort     -> #const SO_REUSEPORT
#endif
#ifdef SO_RCVLOWAT
    RecvLowWater  -> #const SO_RCVLOWAT
#endif
#ifdef SO_SNDLOWAT
    SendLowWater  -> #const SO_SNDLOWAT
#endif
#ifdef SO_RCVTIMEO
    RecvTimeOut   -> #const SO_RCVTIMEO
#endif
#ifdef SO_SNDTIMEO
    SendTimeOut   -> #const SO_SNDTIMEO
#endif
#ifdef SO_USELOOPBACK
    UseLoopBack   -> #const SO_USELOOPBACK
#endif
#if HAVE_DECL_IPV6_V6ONLY
    IPv6Only      -> #const IPV6_V6ONLY
#endif

setSocketOption :: Socket 
                -> SocketOption -- Option Name
                -> Int          -- Option Value
                -> IO ()
setSocketOption (MkSocket s _ _ _ _) so v = do
   with (fromIntegral v) $ \ptr_v -> do
   throwErrnoIfMinus1_ "setSocketOption" $
       c_setsockopt s (socketOptLevel so) (packSocketOption so) ptr_v 
          (fromIntegral (sizeOf (undefined :: CInt)))
   return ()


getSocketOption :: Socket
                -> SocketOption  -- Option Name
                -> IO Int        -- Option Value
getSocketOption (MkSocket s _ _ _ _) so = do
   alloca $ \ptr_v ->
     with (fromIntegral (sizeOf (undefined :: CInt))) $ \ptr_sz -> do
       throwErrnoIfMinus1 "getSocketOption" $
         c_getsockopt s (socketOptLevel so) (packSocketOption so) ptr_v ptr_sz
       fromIntegral `liftM` peek ptr_v


#ifdef HAVE_STRUCT_UCRED
-- | Returns the processID, userID and groupID of the socket's peer.
--
-- Only available on platforms that support SO_PEERCRED on domain sockets.
getPeerCred :: Socket -> IO (CUInt, CUInt, CUInt)
getPeerCred sock = do
  let fd = fdSocket sock
  let sz = (fromIntegral (#const sizeof(struct ucred)))
  with sz $ \ ptr_cr -> 
   alloca       $ \ ptr_sz -> do
     poke ptr_sz sz
     throwErrnoIfMinus1 "getPeerCred" $
       c_getsockopt fd (#const SOL_SOCKET) (#const SO_PEERCRED) ptr_cr ptr_sz
     pid <- (#peek struct ucred, pid) ptr_cr
     uid <- (#peek struct ucred, uid) ptr_cr
     gid <- (#peek struct ucred, gid) ptr_cr
     return (pid, uid, gid)
#endif

##if !(MIN_VERSION_base(4,3,1))
closeFdWith closer fd = closer fd
##endif

#if defined(DOMAIN_SOCKET_SUPPORT)
-- sending/receiving ancillary socket data; low-level mechanism
-- for transmitting file descriptors, mainly.
sendFd :: Socket -> CInt -> IO ()
sendFd sock outfd = do
  let fd = fdSocket sock
#if !defined(__HUGS__)
  throwSocketErrorIfMinus1RetryMayBlock "sendFd"
     (threadWaitWrite (fromIntegral fd)) $
     c_sendFd fd outfd
#else
  c_sendFd fd outfd
#endif
   -- Note: If Winsock supported FD-passing, thi would have been 
   -- incorrect (since socket FDs need to be closed via closesocket().)
  close outfd
  
recvFd :: Socket -> IO CInt
recvFd sock = do
  let fd = fdSocket sock
  theFd <- 
#if !defined(__HUGS__)
    throwSocketErrorIfMinus1RetryMayBlock "recvFd" 
        (threadWaitRead (fromIntegral fd)) $
#endif
         c_recvFd fd
  return theFd


sendAncillary :: Socket
              -> Int
              -> Int
              -> Int
              -> Ptr a
              -> Int
              -> IO ()
sendAncillary sock level ty flags datum len = do
  let fd = fdSocket sock
  _ <-
#if !defined(__HUGS__)
   throwSocketErrorIfMinus1RetryMayBlock "sendAncillary"
     (threadWaitWrite (fromIntegral fd)) $
#endif
     c_sendAncillary fd (fromIntegral level) (fromIntegral ty)
                        (fromIntegral flags) datum (fromIntegral len)
  return ()

recvAncillary :: Socket
              -> Int
              -> Int
              -> IO (Int,Int,Ptr a,Int)
recvAncillary sock flags len = do
  let fd = fdSocket sock
  alloca      $ \ ptr_len   ->
   alloca      $ \ ptr_lev   ->
    alloca      $ \ ptr_ty    ->
     alloca      $ \ ptr_pData -> do
      poke ptr_len (fromIntegral len)
      _ <- 
#if !defined(__HUGS__)
        throwSocketErrorIfMinus1RetryMayBlock "recvAncillary" 
            (threadWaitRead (fromIntegral fd)) $
#endif
            c_recvAncillary fd ptr_lev ptr_ty (fromIntegral flags) ptr_pData ptr_len
      len <- fromIntegral `liftM` peek ptr_len
      lev <- fromIntegral `liftM` peek ptr_lev
      ty  <- fromIntegral `liftM` peek ptr_ty
      pD  <- peek ptr_pData
      return (lev,ty,pD, len)
foreign import ccall SAFE_ON_WIN "sendAncillary"
  c_sendAncillary :: CInt -> CInt -> CInt -> CInt -> Ptr a -> CInt -> IO CInt

foreign import ccall SAFE_ON_WIN "recvAncillary"
  c_recvAncillary :: CInt -> Ptr CInt -> Ptr CInt -> CInt -> Ptr (Ptr a) -> Ptr CInt -> IO CInt

foreign import ccall SAFE_ON_WIN "sendFd" c_sendFd :: CInt -> CInt -> IO CInt
foreign import ccall SAFE_ON_WIN "recvFd" c_recvFd :: CInt -> IO CInt

#endif


{-
A calling sequence table for the main functions is shown in the table below.

\begin{figure}[h]
\begin{center}
\begin{tabular}{|l|c|c|c|c|c|c|c|}d
\hline
{\bf A Call to} & socket & connect & bindSocket & listen & accept & read & write \\
\hline
{\bf Precedes} & & & & & & & \\
\hline 
socket &        &         &            &        &        &      & \\
\hline
connect & +     &         &            &        &        &      & \\
\hline
bindSocket & +  &         &            &        &        &      & \\
\hline
listen &        &         & +          &        &        &      & \\
\hline
accept &        &         &            &  +     &        &      & \\
\hline
read   &        &   +     &            &  +     &  +     &  +   & + \\
\hline
write  &        &   +     &            &  +     &  +     &  +   & + \\
\hline
\end{tabular}
\caption{Sequence Table for Major functions of Socket}
\label{tab:api-seq}
\end{center}
\end{figure}
-}

-- ---------------------------------------------------------------------------
-- OS Dependent Definitions
    
unpackFamily    :: CInt -> Family
packFamily      :: Family -> CInt

packSocketType  :: SocketType -> CInt
unpackSocketType:: CInt -> SocketType

------ ------
                        
packFamily f = case f of
        AF_UNSPEC -> #const AF_UNSPEC
#ifdef AF_UNIX
        AF_UNIX -> #const AF_UNIX
#endif
#ifdef AF_INET
        AF_INET -> #const AF_INET
#endif
#ifdef AF_INET6
        AF_INET6 -> #const AF_INET6
#endif
#ifdef AF_IMPLINK
        AF_IMPLINK -> #const AF_IMPLINK
#endif
#ifdef AF_PUP
        AF_PUP -> #const AF_PUP
#endif
#ifdef AF_CHAOS
        AF_CHAOS -> #const AF_CHAOS
#endif
#ifdef AF_NS
        AF_NS -> #const AF_NS
#endif
#ifdef AF_NBS
        AF_NBS -> #const AF_NBS
#endif
#ifdef AF_ECMA
        AF_ECMA -> #const AF_ECMA
#endif
#ifdef AF_DATAKIT
        AF_DATAKIT -> #const AF_DATAKIT
#endif
#ifdef AF_CCITT
        AF_CCITT -> #const AF_CCITT
#endif
#ifdef AF_SNA
        AF_SNA -> #const AF_SNA
#endif
#ifdef AF_DECnet
        AF_DECnet -> #const AF_DECnet
#endif
#ifdef AF_DLI
        AF_DLI -> #const AF_DLI
#endif
#ifdef AF_LAT
        AF_LAT -> #const AF_LAT
#endif
#ifdef AF_HYLINK
        AF_HYLINK -> #const AF_HYLINK
#endif
#ifdef AF_APPLETALK
        AF_APPLETALK -> #const AF_APPLETALK
#endif
#ifdef AF_ROUTE
        AF_ROUTE -> #const AF_ROUTE
#endif
#ifdef AF_NETBIOS
        AF_NETBIOS -> #const AF_NETBIOS
#endif
#ifdef AF_NIT
        AF_NIT -> #const AF_NIT
#endif
#ifdef AF_802
        AF_802 -> #const AF_802
#endif
#ifdef AF_ISO
        AF_ISO -> #const AF_ISO
#endif
#ifdef AF_OSI
        AF_OSI -> #const AF_OSI
#endif
#ifdef AF_NETMAN
        AF_NETMAN -> #const AF_NETMAN
#endif
#ifdef AF_X25
        AF_X25 -> #const AF_X25
#endif
#ifdef AF_AX25
        AF_AX25 -> #const AF_AX25
#endif
#ifdef AF_OSINET
        AF_OSINET -> #const AF_OSINET
#endif
#ifdef AF_GOSSIP
        AF_GOSSIP -> #const AF_GOSSIP
#endif
#ifdef AF_IPX
        AF_IPX -> #const AF_IPX
#endif
#ifdef Pseudo_AF_XTP
        Pseudo_AF_XTP -> #const Pseudo_AF_XTP
#endif
#ifdef AF_CTF
        AF_CTF -> #const AF_CTF
#endif
#ifdef AF_WAN
        AF_WAN -> #const AF_WAN
#endif
#ifdef AF_SDL
        AF_SDL -> #const AF_SDL
#endif
#ifdef AF_NETWARE
        AF_NETWARE -> #const AF_NETWARE 
#endif
#ifdef AF_NDD
        AF_NDD -> #const AF_NDD         
#endif
#ifdef AF_INTF
        AF_INTF -> #const AF_INTF
#endif
#ifdef AF_COIP
        AF_COIP -> #const AF_COIP
#endif
#ifdef AF_CNT
        AF_CNT -> #const AF_CNT
#endif
#ifdef Pseudo_AF_RTIP
        Pseudo_AF_RTIP -> #const Pseudo_AF_RTIP
#endif
#ifdef Pseudo_AF_PIP
        Pseudo_AF_PIP -> #const Pseudo_AF_PIP
#endif
#ifdef AF_SIP
        AF_SIP -> #const AF_SIP
#endif
#ifdef AF_ISDN
        AF_ISDN -> #const AF_ISDN
#endif
#ifdef Pseudo_AF_KEY
        Pseudo_AF_KEY -> #const Pseudo_AF_KEY
#endif
#ifdef AF_NATM
        AF_NATM -> #const AF_NATM
#endif
#ifdef AF_ARP
        AF_ARP -> #const AF_ARP
#endif
#ifdef Pseudo_AF_HDRCMPLT
        Pseudo_AF_HDRCMPLT -> #const Pseudo_AF_HDRCMPLT
#endif
#ifdef AF_ENCAP
        AF_ENCAP -> #const AF_ENCAP 
#endif
#ifdef AF_LINK
        AF_LINK -> #const AF_LINK
#endif
#ifdef AF_RAW
        AF_RAW -> #const AF_RAW
#endif
#ifdef AF_RIF
        AF_RIF -> #const AF_RIF
#endif
#ifdef AF_NETROM
        AF_NETROM -> #const AF_NETROM
#endif
#ifdef AF_BRIDGE
        AF_BRIDGE -> #const AF_BRIDGE
#endif
#ifdef AF_ATMPVC
        AF_ATMPVC -> #const AF_ATMPVC
#endif
#ifdef AF_ROSE
        AF_ROSE -> #const AF_ROSE
#endif
#ifdef AF_NETBEUI
        AF_NETBEUI -> #const AF_NETBEUI
#endif
#ifdef AF_SECURITY
        AF_SECURITY -> #const AF_SECURITY
#endif
#ifdef AF_PACKET
        AF_PACKET -> #const AF_PACKET
#endif
#ifdef AF_ASH
        AF_ASH -> #const AF_ASH
#endif
#ifdef AF_ECONET
        AF_ECONET -> #const AF_ECONET
#endif
#ifdef AF_ATMSVC
        AF_ATMSVC -> #const AF_ATMSVC
#endif
#ifdef AF_IRDA
        AF_IRDA -> #const AF_IRDA
#endif
#ifdef AF_PPPOX
        AF_PPPOX -> #const AF_PPPOX
#endif
#ifdef AF_WANPIPE
        AF_WANPIPE -> #const AF_WANPIPE
#endif
#ifdef AF_BLUETOOTH
        AF_BLUETOOTH -> #const AF_BLUETOOTH
#endif

--------- ----------

unpackFamily f = case f of
        (#const AF_UNSPEC) -> AF_UNSPEC
#ifdef AF_UNIX
        (#const AF_UNIX) -> AF_UNIX
#endif
#ifdef AF_INET
        (#const AF_INET) -> AF_INET
#endif
#ifdef AF_INET6
        (#const AF_INET6) -> AF_INET6
#endif
#ifdef AF_IMPLINK
        (#const AF_IMPLINK) -> AF_IMPLINK
#endif
#ifdef AF_PUP
        (#const AF_PUP) -> AF_PUP
#endif
#ifdef AF_CHAOS
        (#const AF_CHAOS) -> AF_CHAOS
#endif
#ifdef AF_NS
        (#const AF_NS) -> AF_NS
#endif
#ifdef AF_NBS
        (#const AF_NBS) -> AF_NBS
#endif
#ifdef AF_ECMA
        (#const AF_ECMA) -> AF_ECMA
#endif
#ifdef AF_DATAKIT
        (#const AF_DATAKIT) -> AF_DATAKIT
#endif
#ifdef AF_CCITT
        (#const AF_CCITT) -> AF_CCITT
#endif
#ifdef AF_SNA
        (#const AF_SNA) -> AF_SNA
#endif
#ifdef AF_DECnet
        (#const AF_DECnet) -> AF_DECnet
#endif
#ifdef AF_DLI
        (#const AF_DLI) -> AF_DLI
#endif
#ifdef AF_LAT
        (#const AF_LAT) -> AF_LAT
#endif
#ifdef AF_HYLINK
        (#const AF_HYLINK) -> AF_HYLINK
#endif
#ifdef AF_APPLETALK
        (#const AF_APPLETALK) -> AF_APPLETALK
#endif
#ifdef AF_ROUTE
        (#const AF_ROUTE) -> AF_ROUTE
#endif
#ifdef AF_NETBIOS
        (#const AF_NETBIOS) -> AF_NETBIOS
#endif
#ifdef AF_NIT
        (#const AF_NIT) -> AF_NIT
#endif
#ifdef AF_802
        (#const AF_802) -> AF_802
#endif
#ifdef AF_ISO
        (#const AF_ISO) -> AF_ISO
#endif
#ifdef AF_OSI
# if (!defined(AF_ISO)) || (defined(AF_ISO) && (AF_ISO != AF_OSI))
        (#const AF_OSI) -> AF_OSI
# endif
#endif
#ifdef AF_NETMAN
        (#const AF_NETMAN) -> AF_NETMAN
#endif
#ifdef AF_X25
        (#const AF_X25) -> AF_X25
#endif
#ifdef AF_AX25
        (#const AF_AX25) -> AF_AX25
#endif
#ifdef AF_OSINET
        (#const AF_OSINET) -> AF_OSINET
#endif
#ifdef AF_GOSSIP
        (#const AF_GOSSIP) -> AF_GOSSIP
#endif
#if defined(AF_IPX) && (!defined(AF_NS) || AF_NS != AF_IPX)
        (#const AF_IPX) -> AF_IPX
#endif
#ifdef Pseudo_AF_XTP
        (#const Pseudo_AF_XTP) -> Pseudo_AF_XTP
#endif
#ifdef AF_CTF
        (#const AF_CTF) -> AF_CTF
#endif
#ifdef AF_WAN
        (#const AF_WAN) -> AF_WAN
#endif
#ifdef AF_SDL
        (#const AF_SDL) -> AF_SDL
#endif
#ifdef AF_NETWARE
        (#const AF_NETWARE) -> AF_NETWARE       
#endif
#ifdef AF_NDD
        (#const AF_NDD) -> AF_NDD               
#endif
#ifdef AF_INTF
        (#const AF_INTF) -> AF_INTF
#endif
#ifdef AF_COIP
        (#const AF_COIP) -> AF_COIP
#endif
#ifdef AF_CNT
        (#const AF_CNT) -> AF_CNT
#endif
#ifdef Pseudo_AF_RTIP
        (#const Pseudo_AF_RTIP) -> Pseudo_AF_RTIP
#endif
#ifdef Pseudo_AF_PIP
        (#const Pseudo_AF_PIP) -> Pseudo_AF_PIP
#endif
#ifdef AF_SIP
        (#const AF_SIP) -> AF_SIP
#endif
#ifdef AF_ISDN
        (#const AF_ISDN) -> AF_ISDN
#endif
#ifdef Pseudo_AF_KEY
        (#const Pseudo_AF_KEY) -> Pseudo_AF_KEY
#endif
#ifdef AF_NATM
        (#const AF_NATM) -> AF_NATM
#endif
#ifdef AF_ARP
        (#const AF_ARP) -> AF_ARP
#endif
#ifdef Pseudo_AF_HDRCMPLT
        (#const Pseudo_AF_HDRCMPLT) -> Pseudo_AF_HDRCMPLT
#endif
#ifdef AF_ENCAP
        (#const AF_ENCAP) -> AF_ENCAP 
#endif
#ifdef AF_LINK
        (#const AF_LINK) -> AF_LINK
#endif
#ifdef AF_RAW
        (#const AF_RAW) -> AF_RAW
#endif
#ifdef AF_RIF
        (#const AF_RIF) -> AF_RIF
#endif
#ifdef AF_NETROM
        (#const AF_NETROM) -> AF_NETROM
#endif
#ifdef AF_BRIDGE
        (#const AF_BRIDGE) -> AF_BRIDGE
#endif
#ifdef AF_ATMPVC
        (#const AF_ATMPVC) -> AF_ATMPVC
#endif
#ifdef AF_ROSE
        (#const AF_ROSE) -> AF_ROSE
#endif
#ifdef AF_NETBEUI
        (#const AF_NETBEUI) -> AF_NETBEUI
#endif
#ifdef AF_SECURITY
        (#const AF_SECURITY) -> AF_SECURITY
#endif
#ifdef AF_PACKET
        (#const AF_PACKET) -> AF_PACKET
#endif
#ifdef AF_ASH
        (#const AF_ASH) -> AF_ASH
#endif
#ifdef AF_ECONET
        (#const AF_ECONET) -> AF_ECONET
#endif
#ifdef AF_ATMSVC
        (#const AF_ATMSVC) -> AF_ATMSVC
#endif
#ifdef AF_IRDA
        (#const AF_IRDA) -> AF_IRDA
#endif
#ifdef AF_PPPOX
        (#const AF_PPPOX) -> AF_PPPOX
#endif
#ifdef AF_WANPIPE
        (#const AF_WANPIPE) -> AF_WANPIPE
#endif
#ifdef AF_BLUETOOTH
        (#const AF_BLUETOOTH) -> AF_BLUETOOTH
#endif
        unknown -> error ("Network.Socket.unpackFamily: unknown address " ++
                          "family " ++ show unknown)

-- Socket Types.

-- | Socket Types.
--
-- This data type might have different constructors depending on what is
-- supported by the operating system.
data SocketType
        = NoSocketType
#ifdef SOCK_STREAM
        | Stream 
#endif
#ifdef SOCK_DGRAM
        | Datagram
#endif
#ifdef SOCK_RAW
        | Raw 
#endif
#ifdef SOCK_RDM
        | RDM 
#endif
#ifdef SOCK_SEQPACKET
        | SeqPacket
#endif
        deriving (Eq, Ord, Read, Show, Typeable)

packSocketType stype = case stype of
        NoSocketType -> 0
#ifdef SOCK_STREAM
        Stream -> #const SOCK_STREAM
#endif
#ifdef SOCK_DGRAM
        Datagram -> #const SOCK_DGRAM
#endif
#ifdef SOCK_RAW
        Raw -> #const SOCK_RAW
#endif
#ifdef SOCK_RDM
        RDM -> #const SOCK_RDM
#endif
#ifdef SOCK_SEQPACKET
        SeqPacket -> #const SOCK_SEQPACKET
#endif

unpackSocketType t = case t of
        0 -> NoSocketType
#ifdef SOCK_STREAM
        (#const SOCK_STREAM) -> Stream
#endif
#ifdef SOCK_DGRAM
        (#const SOCK_DGRAM) -> Datagram
#endif
#ifdef SOCK_RAW
        (#const SOCK_RAW) -> Raw
#endif
#ifdef SOCK_RDM
        (#const SOCK_RDM) -> RDM
#endif
#ifdef SOCK_SEQPACKET
        (#const SOCK_SEQPACKET) -> SeqPacket
#endif

-- ---------------------------------------------------------------------------
-- Utility Functions

aNY_PORT :: PortNumber 
aNY_PORT = 0

-- | The IPv4 wild card address.

iNADDR_ANY :: HostAddress
iNADDR_ANY = htonl (#const INADDR_ANY)

#if defined(IPV6_SOCKET_SUPPORT)
-- | The IPv6 wild card address.

iN6ADDR_ANY :: HostAddress6
iN6ADDR_ANY = (0, 0, 0, 0)
#endif

sOMAXCONN :: Int
sOMAXCONN = #const SOMAXCONN

sOL_SOCKET :: Int
sOL_SOCKET = #const SOL_SOCKET

#ifdef SCM_RIGHTS
sCM_RIGHTS :: Int
sCM_RIGHTS = #const SCM_RIGHTS
#endif

maxListenQueue :: Int
maxListenQueue = sOMAXCONN

-- -----------------------------------------------------------------------------

data ShutdownCmd 
 = ShutdownReceive
 | ShutdownSend
 | ShutdownBoth
 deriving Typeable

sdownCmdToInt :: ShutdownCmd -> CInt
sdownCmdToInt ShutdownReceive = 0
sdownCmdToInt ShutdownSend    = 1
sdownCmdToInt ShutdownBoth    = 2

-- | Shut down one or both halves of the connection, depending on the
-- second argument to the function.  If the second argument is
-- 'ShutdownReceive', further receives are disallowed.  If it is
-- 'ShutdownSend', further sends are disallowed.  If it is
-- 'ShutdownBoth', further sends and receives are disallowed.
shutdown :: Socket -> ShutdownCmd -> IO ()
shutdown (MkSocket s _ _ _ _) stype = do
  throwSocketErrorIfMinus1Retry "shutdown" (c_shutdown s (sdownCmdToInt stype))
  return ()

-- -----------------------------------------------------------------------------

-- | Close the socket.  All future operations on the socket object
-- will fail.  The remote end will receive no more data (after queued
-- data is flushed).
sClose   :: Socket -> IO ()
sClose (MkSocket s _ _ _ socketStatus) = do 
 modifyMVar_ socketStatus $ \ status ->
   case status of
     ConvertedToHandle ->
         ioError (userError ("sClose: converted to a Handle, use hClose instead"))
     Closed ->
         return status
     _ -> closeFdWith (close . fromIntegral) (fromIntegral s) >> return Closed

-- -----------------------------------------------------------------------------

sIsConnected :: Socket -> IO Bool
sIsConnected (MkSocket _ _ _ _ status) = do
    value <- readMVar status
    return (value == Connected) 

-- -----------------------------------------------------------------------------
-- Socket Predicates

sIsBound :: Socket -> IO Bool
sIsBound (MkSocket _ _ _ _ status) = do
    value <- readMVar status
    return (value == Bound)     

sIsListening :: Socket -> IO Bool
sIsListening (MkSocket _ _ _  _ status) = do
    value <- readMVar status
    return (value == Listening) 

sIsReadable  :: Socket -> IO Bool
sIsReadable (MkSocket _ _ _ _ status) = do
    value <- readMVar status
    return (value == Listening || value == Connected)

sIsWritable  :: Socket -> IO Bool
sIsWritable = sIsReadable -- sort of.

sIsAcceptable :: Socket -> IO Bool
#if defined(DOMAIN_SOCKET_SUPPORT)
sIsAcceptable (MkSocket _ AF_UNIX x _ status)
    | x == Stream || x == SeqPacket = do
        value <- readMVar status
        return (value == Connected || value == Bound || value == Listening)
sIsAcceptable (MkSocket _ AF_UNIX _ _ _) = return False
#endif
sIsAcceptable (MkSocket _ _ _ _ status) = do
    value <- readMVar status
    return (value == Connected || value == Listening)
    
-- -----------------------------------------------------------------------------
-- Internet address manipulation routines:

inet_addr :: String -> IO HostAddress
inet_addr ipstr = do
   withCString ipstr $ \str -> do
   had <- c_inet_addr str
   if had == -1
    then ioError (userError ("inet_addr: Malformed address: " ++ ipstr))
    else return had  -- network byte order

inet_ntoa :: HostAddress -> IO String
inet_ntoa haddr = do
  pstr <- c_inet_ntoa haddr
  peekCString pstr

-- | Turns a Socket into an 'Handle'. By default, the new handle is
-- unbuffered. Use 'System.IO.hSetBuffering' to change the buffering.
--
-- Note that since a 'Handle' is automatically closed by a finalizer
-- when it is no longer referenced, you should avoid doing any more
-- operations on the 'Socket' after calling 'socketToHandle'.  To
-- close the 'Socket' after 'socketToHandle', call 'System.IO.hClose'
-- on the 'Handle'.

#ifndef __PARALLEL_HASKELL__
socketToHandle :: Socket -> IOMode -> IO Handle
socketToHandle s@(MkSocket fd _ _ _ socketStatus) mode = do
 modifyMVar socketStatus $ \ status ->
    if status == ConvertedToHandle
        then ioError (userError ("socketToHandle: already a Handle"))
        else do
# if __GLASGOW_HASKELL__ >= 611
    h <- fdToHandle' (fromIntegral fd) (Just GHC.IO.Device.Stream) True (show s) mode True{-bin-}
# elif __GLASGOW_HASKELL__ >= 608
    h <- fdToHandle' (fromIntegral fd) (Just System.Posix.Internals.Stream) True (show s) mode True{-bin-}
# elif __GLASGOW_HASKELL__ && __GLASGOW_HASKELL__ < 608
    h <- openFd (fromIntegral fd) (Just System.Posix.Internals.Stream) True (show s) mode True{-bin-}
# elif defined(__HUGS__)
    h <- openFd (fromIntegral fd) True{-is a socket-} mode True{-bin-}
# endif
    return (ConvertedToHandle, h)
#else
socketToHandle (MkSocket s family stype protocol status) m =
  error "socketToHandle not implemented in a parallel setup"
#endif

-- | Pack a list of values into a bitmask.  The possible mappings from
-- value to bit-to-set are given as the first argument.  We assume
-- that each value can cause exactly one bit to be set; unpackBits will
-- break if this property is not true.

packBits :: (Eq a, Bits b) => [(a, b)] -> [a] -> b

packBits mapping xs = foldl' pack 0 mapping
    where pack acc (k, v) | k `elem` xs = acc .|. v
                          | otherwise   = acc

-- | Unpack a bitmask into a list of values.

unpackBits :: Bits b => [(a, b)] -> b -> [a]

-- Be permissive and ignore unknown bit values. At least on OS X,
-- getaddrinfo returns an ai_flags field with bits set that have no
-- entry in <netdb.h>.
unpackBits [] _    = []
unpackBits ((k,v):xs) r
    | r .&. v /= 0 = k : unpackBits xs (r .&. complement v)
    | otherwise    = unpackBits xs r

-----------------------------------------------------------------------------
-- Address and service lookups

#if defined(IPV6_SOCKET_SUPPORT)

-- | Flags that control the querying behaviour of 'getAddrInfo'.
data AddrInfoFlag
    = AI_ADDRCONFIG
    | AI_ALL
    | AI_CANONNAME
    | AI_NUMERICHOST
    | AI_NUMERICSERV
    | AI_PASSIVE
    | AI_V4MAPPED
    deriving (Eq, Read, Show, Typeable)

aiFlagMapping :: [(AddrInfoFlag, CInt)]

aiFlagMapping =
    [
#if HAVE_DECL_AI_ADDRCONFIG
     (AI_ADDRCONFIG, #const AI_ADDRCONFIG),
#else
     (AI_ADDRCONFIG, 0),
#endif
#if HAVE_DECL_AI_ALL
     (AI_ALL, #const AI_ALL),
#else
     (AI_ALL, 0),
#endif
     (AI_CANONNAME, #const AI_CANONNAME),
     (AI_NUMERICHOST, #const AI_NUMERICHOST),
#if HAVE_DECL_AI_NUMERICSERV
     (AI_NUMERICSERV, #const AI_NUMERICSERV),
#else
     (AI_NUMERICSERV, 0),
#endif
     (AI_PASSIVE, #const AI_PASSIVE),
#if HAVE_DECL_AI_V4MAPPED
     (AI_V4MAPPED, #const AI_V4MAPPED)
#else
     (AI_V4MAPPED, 0)
#endif
    ]

-- | Indicate whether the given 'AddrInfoFlag' will have any effect on
-- this system.
addrInfoFlagImplemented :: AddrInfoFlag -> Bool
addrInfoFlagImplemented f = packBits aiFlagMapping [f] /= 0

data AddrInfo =
    AddrInfo {
        addrFlags :: [AddrInfoFlag],
        addrFamily :: Family,
        addrSocketType :: SocketType,
        addrProtocol :: ProtocolNumber,
        addrAddress :: SockAddr,
        addrCanonName :: Maybe String
        }
    deriving (Eq, Show, Typeable)

instance Storable AddrInfo where
    sizeOf    _ = #const sizeof(struct addrinfo)
    alignment _ = alignment (undefined :: CInt)

    peek p = do
        ai_flags <- (#peek struct addrinfo, ai_flags) p
        ai_family <- (#peek struct addrinfo, ai_family) p
        ai_socktype <- (#peek struct addrinfo, ai_socktype) p
        ai_protocol <- (#peek struct addrinfo, ai_protocol) p
        ai_addr <- (#peek struct addrinfo, ai_addr) p >>= peekSockAddr
        ai_canonname_ptr <- (#peek struct addrinfo, ai_canonname) p

        ai_canonname <- if ai_canonname_ptr == nullPtr
                        then return Nothing
                        else liftM Just $ peekCString ai_canonname_ptr
                             
        return (AddrInfo
                {
                 addrFlags = unpackBits aiFlagMapping ai_flags,
                 addrFamily = unpackFamily ai_family,
                 addrSocketType = unpackSocketType ai_socktype,
                 addrProtocol = ai_protocol,
                 addrAddress = ai_addr,
                 addrCanonName = ai_canonname
                })

    poke p (AddrInfo flags family socketType protocol _ _) = do
        (#poke struct addrinfo, ai_flags) p (packBits aiFlagMapping flags)
        (#poke struct addrinfo, ai_family) p (packFamily family)
        (#poke struct addrinfo, ai_socktype) p (packSocketType socketType)
        (#poke struct addrinfo, ai_protocol) p protocol

        -- stuff below is probably not needed, but let's zero it for safety

        (#poke struct addrinfo, ai_addrlen) p (0::CSize)
        (#poke struct addrinfo, ai_addr) p nullPtr
        (#poke struct addrinfo, ai_canonname) p nullPtr
        (#poke struct addrinfo, ai_next) p nullPtr

data NameInfoFlag
    = NI_DGRAM
    | NI_NAMEREQD
    | NI_NOFQDN
    | NI_NUMERICHOST
    | NI_NUMERICSERV
    deriving (Eq, Read, Show, Typeable)

niFlagMapping :: [(NameInfoFlag, CInt)]

niFlagMapping = [(NI_DGRAM, #const NI_DGRAM),
                 (NI_NAMEREQD, #const NI_NAMEREQD),
                 (NI_NOFQDN, #const NI_NOFQDN),
                 (NI_NUMERICHOST, #const NI_NUMERICHOST),
                 (NI_NUMERICSERV, #const NI_NUMERICSERV)]

-- | Default hints for address lookup with 'getAddrInfo'.  The values
-- of the 'addrAddress' and 'addrCanonName' fields are 'undefined',
-- and are never inspected by 'getAddrInfo'.

defaultHints :: AddrInfo

defaultHints = AddrInfo {
                         addrFlags = [],
                         addrFamily = AF_UNSPEC,
                         addrSocketType = NoSocketType,
                         addrProtocol = defaultProtocol,
                         addrAddress = undefined,
                         addrCanonName = undefined
                        }

-- | Resolve a host or service name to one or more addresses.
-- The 'AddrInfo' values that this function returns contain 'SockAddr'
-- values that you can pass directly to 'connect' or
-- 'bindSocket'.
--
-- This function is protocol independent.  It can return both IPv4 and
-- IPv6 address information.
--
-- The 'AddrInfo' argument specifies the preferred query behaviour,
-- socket options, or protocol.  You can override these conveniently
-- using Haskell's record update syntax on 'defaultHints', for example
-- as follows:
--
-- @
--   myHints = defaultHints { addrFlags = [AI_ADDRCONFIG, AI_CANONNAME] }
-- @
--
-- Values for 'addrFlags' control query behaviour.  The supported
-- flags are as follows:
--
--   [@AI_PASSIVE@] If no 'HostName' value is provided, the network
--     address in each 'SockAddr'
--     will be left as a "wild card", i.e. as either 'iNADDR_ANY'
--     or 'iN6ADDR_ANY'.  This is useful for server applications that
--     will accept connections from any client.
--
--   [@AI_CANONNAME@] The 'addrCanonName' field of the first returned
--     'AddrInfo' will contain the "canonical name" of the host.
--
--   [@AI_NUMERICHOST@] The 'HostName' argument /must/ be a numeric
--     address in string form, and network name lookups will not be
--     attempted.
-- 
-- /Note/: Although the following flags are required by RFC 3493, they
-- may not have an effect on all platforms, because the underlying
-- network stack may not support them.  To see whether a flag from the
-- list below will have any effect, call 'addrInfoFlagImplemented'.
--
--   [@AI_NUMERICSERV@] The 'ServiceName' argument /must/ be a port
--     number in string form, and service name lookups will not be
--     attempted.
--
--   [@AI_ADDRCONFIG@] The list of returned 'AddrInfo' values will
--     only contain IPv4 addresses if the local system has at least
--     one IPv4 interface configured, and likewise for IPv6.
--
--   [@AI_V4MAPPED@] If an IPv6 lookup is performed, and no IPv6
--     addresses are found, IPv6-mapped IPv4 addresses will be
--     returned.
--
--   [@AI_ALL@] If 'AI_ALL' is specified, return all matching IPv6 and
--     IPv4 addresses.  Otherwise, this flag has no effect.
--     
-- You must provide a 'Just' value for at least one of the 'HostName'
-- or 'ServiceName' arguments.  'HostName' can be either a numeric
-- network address (dotted quad for IPv4, colon-separated hex for
-- IPv6) or a hostname.  In the latter case, its addresses will be
-- looked up unless 'AI_NUMERICHOST' is specified as a hint.  If you
-- do not provide a 'HostName' value /and/ do not set 'AI_PASSIVE' as
-- a hint, network addresses in the result will contain the address of
-- the loopback interface.
--
-- If the query fails, this function throws an IO exception instead of
-- returning an empty list.  Otherwise, it returns a non-empty list
-- of 'AddrInfo' values.
--
-- There are several reasons why a query might result in several
-- values.  For example, the queried-for host could be multihomed, or
-- the service might be available via several protocols.
--
-- Note: the order of arguments is slightly different to that defined
-- for @getaddrinfo@ in RFC 2553.  The 'AddrInfo' parameter comes first
-- to make partial application easier.
--
-- Example:
-- @
--   let hints = defaultHints { addrFlags = [AI_ADDRCONFIG, AI_CANONNAME] }
--   addrs <- getAddrInfo (Just hints) (Just "www.haskell.org") (Just "http")
--   let addr = head addrs
--   sock <- socket (addrFamily addr) (addrSocketType addr) (addrProtocol addr)
--   connect sock (addrAddress addr)
-- @

getAddrInfo :: Maybe AddrInfo -- ^ preferred socket type or protocol
            -> Maybe HostName -- ^ host name to look up
            -> Maybe ServiceName -- ^ service name to look up
            -> IO [AddrInfo] -- ^ resolved addresses, with "best" first

getAddrInfo hints node service =
  maybeWith withCString node $ \c_node ->
    maybeWith withCString service $ \c_service ->
      maybeWith with hints $ \c_hints ->
        alloca $ \ptr_ptr_addrs -> do
          ret <- c_getaddrinfo c_node c_service c_hints ptr_ptr_addrs
          case ret of
            0 -> do ptr_addrs <- peek ptr_ptr_addrs
                    ais <- followAddrInfo ptr_addrs
                    c_freeaddrinfo ptr_addrs
                    return ais
            _ -> do err <- gai_strerror ret
                    ioError (ioeSetErrorString
                             (mkIOError NoSuchThing "getAddrInfo" Nothing
                              Nothing) err)

followAddrInfo :: Ptr AddrInfo -> IO [AddrInfo]

followAddrInfo ptr_ai | ptr_ai == nullPtr = return []
                      | otherwise = do
    a <- peek ptr_ai
    as <- (#peek struct addrinfo, ai_next) ptr_ai >>= followAddrInfo
    return (a:as)

foreign import ccall safe "hsnet_getaddrinfo"
    c_getaddrinfo :: CString -> CString -> Ptr AddrInfo -> Ptr (Ptr AddrInfo)
                  -> IO CInt

foreign import ccall safe "hsnet_freeaddrinfo"
    c_freeaddrinfo :: Ptr AddrInfo -> IO ()

gai_strerror :: CInt -> IO String

#ifdef HAVE_GAI_STRERROR
gai_strerror n = c_gai_strerror n >>= peekCString

foreign import ccall safe "gai_strerror"
    c_gai_strerror :: CInt -> IO CString
#else
gai_strerror n = return ("error " ++ show n)
#endif

withCStringIf :: Bool -> Int -> (CSize -> CString -> IO a) -> IO a
withCStringIf False _ f = f 0 nullPtr
withCStringIf True n f = allocaBytes n (f (fromIntegral n))
                    
-- | Resolve an address to a host or service name.
-- This function is protocol independent.
--
-- The list of 'NameInfoFlag' values controls query behaviour.  The
-- supported flags are as follows:
--
--   [@NI_NOFQDN@] If a host is local, return only the
--     hostname part of the FQDN.
--
--   [@NI_NUMERICHOST@] The name of the host is not
--     looked up.  Instead, a numeric representation of the host's
--     address is returned.  For an IPv4 address, this will be a
--     dotted-quad string.  For IPv6, it will be colon-separated
--     hexadecimal.
--
--   [@NI_NUMERICSERV@] The name of the service is not
--     looked up.  Instead, a numeric representation of the
--     service is returned.
--
--   [@NI_NAMEREQD@] If the hostname cannot be looked up, an IO error
--     is thrown.
--
--   [@NI_DGRAM@] Resolve a datagram-based service name.  This is
--     required only for the few protocols that have different port
--     numbers for their datagram-based versions than for their
--     stream-based versions.
--
-- Hostname and service name lookups can be expensive.  You can
-- specify which lookups to perform via the two 'Bool' arguments.  If
-- one of these is 'False', the corresponding value in the returned
-- tuple will be 'Nothing', and no lookup will be performed.
--
-- If a host or service's name cannot be looked up, then the numeric
-- form of the address or service will be returned.
--
-- If the query fails, this function throws an IO exception.
--
-- Example:
-- @
--   (hostName, _) <- getNameInfo [] True False myAddress
-- @

getNameInfo :: [NameInfoFlag] -- ^ flags to control lookup behaviour
            -> Bool -- ^ whether to look up a hostname
            -> Bool -- ^ whether to look up a service name
            -> SockAddr -- ^ the address to look up
            -> IO (Maybe HostName, Maybe ServiceName)

getNameInfo flags doHost doService addr =
  withCStringIf doHost (#const NI_MAXHOST) $ \c_hostlen c_host ->
    withCStringIf doService (#const NI_MAXSERV) $ \c_servlen c_serv -> do
      withSockAddr addr $ \ptr_addr sz -> do
        ret <- c_getnameinfo ptr_addr (fromIntegral sz) c_host c_hostlen
                             c_serv c_servlen (packBits niFlagMapping flags)
        case ret of
          0 -> do
            let peekIf doIf c_val = if doIf
                                     then liftM Just $ peekCString c_val
                                     else return Nothing
            host <- peekIf doHost c_host
            serv <- peekIf doService c_serv
            return (host, serv)
          _ -> do err <- gai_strerror ret
                  ioError (ioeSetErrorString
                           (mkIOError NoSuchThing "getNameInfo" Nothing 
                            Nothing) err)

foreign import ccall safe "hsnet_getnameinfo"
    c_getnameinfo :: Ptr SockAddr -> CInt{-CSockLen???-} -> CString -> CSize -> CString
                  -> CSize -> CInt -> IO CInt
#endif

mkInvalidRecvArgError :: String -> IOError
mkInvalidRecvArgError loc = ioeSetErrorString (mkIOError
#ifdef __GLASGOW_HASKELL__
                                    InvalidArgument
#else
                                    IllegalOperation
#endif
                                    loc Nothing Nothing) "non-positive length"

mkEOFError :: String -> IOError
mkEOFError loc = ioeSetErrorString (mkIOError EOF loc Nothing Nothing) "end of file"

-- ---------------------------------------------------------------------------
-- foreign imports from the C library

foreign import ccall unsafe "my_inet_ntoa"
  c_inet_ntoa :: HostAddress -> IO (Ptr CChar)

foreign import CALLCONV unsafe "inet_addr"
  c_inet_addr :: Ptr CChar -> IO HostAddress

foreign import CALLCONV unsafe "shutdown"
  c_shutdown :: CInt -> CInt -> IO CInt 

close :: CInt -> IO ()
close fd = throwErrnoIfMinus1Retry_ "Network.Socket.close" $ c_close fd

#if !defined(WITH_WINSOCK)
foreign import ccall unsafe "close"
  c_close :: CInt -> IO CInt
#else
foreign import stdcall unsafe "closesocket"
  c_close :: CInt -> IO CInt
#endif

foreign import CALLCONV unsafe "socket"
  c_socket :: CInt -> CInt -> CInt -> IO CInt
foreign import CALLCONV unsafe "bind"
  c_bind :: CInt -> Ptr SockAddr -> CInt{-CSockLen???-} -> IO CInt
foreign import CALLCONV unsafe "connect"
  c_connect :: CInt -> Ptr SockAddr -> CInt{-CSockLen???-} -> IO CInt
foreign import CALLCONV unsafe "accept"
  c_accept :: CInt -> Ptr SockAddr -> Ptr CInt{-CSockLen???-} -> IO CInt
foreign import CALLCONV safe "accept"
  c_accept_safe :: CInt -> Ptr SockAddr -> Ptr CInt{-CSockLen???-} -> IO CInt
foreign import CALLCONV unsafe "listen"
  c_listen :: CInt -> CInt -> IO CInt

#ifdef __GLASGOW_HASKELL__
foreign import ccall "rtsSupportsBoundThreads" threaded :: Bool
#endif

foreign import CALLCONV unsafe "send"
  c_send :: CInt -> Ptr a -> CSize -> CInt -> IO CInt
foreign import CALLCONV SAFE_ON_WIN "sendto"
  c_sendto :: CInt -> Ptr a -> CSize -> CInt -> Ptr SockAddr -> CInt -> IO CInt
foreign import CALLCONV unsafe "recv"
  c_recv :: CInt -> Ptr CChar -> CSize -> CInt -> IO CInt
foreign import CALLCONV SAFE_ON_WIN "recvfrom"
  c_recvfrom :: CInt -> Ptr a -> CSize -> CInt -> Ptr SockAddr -> Ptr CInt -> IO CInt
foreign import CALLCONV unsafe "getpeername"
  c_getpeername :: CInt -> Ptr SockAddr -> Ptr CInt -> IO CInt
foreign import CALLCONV unsafe "getsockname"
  c_getsockname :: CInt -> Ptr SockAddr -> Ptr CInt -> IO CInt

foreign import CALLCONV unsafe "getsockopt"
  c_getsockopt :: CInt -> CInt -> CInt -> Ptr CInt -> Ptr CInt -> IO CInt
foreign import CALLCONV unsafe "setsockopt"
  c_setsockopt :: CInt -> CInt -> CInt -> Ptr CInt -> CInt -> IO CInt