{-# LANGUAGE ForeignFunctionInterface #-}
-- | FreeBSD system-dependent code for 'sendfile'.
module System.SendFile.FreeBSD (sendFile) where

import Data.Int
import Foreign.C.Error (eAGAIN, eINTR, getErrno, throwErrno)
import Foreign.C.Types (CInt, CSize)
import Foreign.Marshal.Alloc (alloca)
import Foreign.Ptr (Ptr, nullPtr)
import Foreign.Storable (peek)
import System.Posix.Types (COff, Fd)

sendFile :: Fd -> Fd -> Int64 -> Int64 -> IO Int64
sendFile out_fd in_fd off count
  | count == 0 = return 0
  | otherwise  = alloca $ \pbytes -> do
        sbytes <- sendfile out_fd in_fd (fromIntegral off)
                                        (fromIntegral count) pbytes
        return $ fromIntegral sbytes

sendfile :: Fd -> Fd -> COff -> CSize -> Ptr COff -> IO COff
sendfile out_fd in_fd off count pbytes =
    do threadWaitWrite out_fd
       res <- c_sendfile_freebsd in_fd out_fd off count nullPtr pbytes 0
       nsent <- peek pbytes
       if (res == 0)
          then return nsent
          else do errno <- getErrno
                  if (errno == eAGAIN) || (errno == eINTR)
                   then return nsent
                   else throwErrno "System.SendFile.FreeBSD.sendfile"

-- max num of bytes in one send
maxBytes :: CSize
maxBytes = maxBound :: CSize

foreign import ccall unsafe "sys/uio.h sendfile" c_sendfile_freebsd
    :: Fd -> Fd -> COff -> CSize -> Ptr () -> Ptr COff -> CInt -> IO CInt