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|
{-# OPTIONS -fglasgow-exts -cpp #-}
-----------------------------------------------------------------------------
-- |
-- Module : System.Sendfile
-- Copyright : (c) Volker Stolz 2003
-- License : BSD-style (see the file libraries/core/LICENSE)
--
-- Maintainer : libraries@haskell.org
-- Stability : provisional
-- Portability : fallback NYI
--
-- "System.Sendfile.sendfile" is a low-level method for efficently passing
-- data from one file descriptor to another.
-- The intended audience includes for example web server authors. Please
-- note that this function is highly platform dependent.
--
-----------------------------------------------------------------------------
module System.Sendfile (sendfile) where
#include "config.h"
#include "HsUnix.h"
import Foreign
import Foreign.C
import System.IO (Handle)
import System.Posix.IO (handleToFd)
import System.Posix.Types (Fd, COff)
-- |'sendfile' transmits the contents of an open file to a stream socket
-- opened for writing with as little overhead as possible. This function
-- is not defined by any standard!
-- Notice that passing 0 as 'count' may result in undefined behaviour and
-- should be avoided. On Linux, nothing is transmitted while on FreeBSD
-- the entire file will be sent.
sendfile :: Handle -- Input
-> Handle -- Output
-> Int -- Offset
-> Int -- Nr. of bytes to transmit
-> IO ()
sendfile inH outH startpos count = do
#ifdef HAVE_LINUX_SENDFILE
inFd <- handleToFd inH
outFd <- handleToFd outH
offsetptr <- malloc
poke offsetptr (fromIntegral startpos)
throwErrnoIfMinus1_ "sendfile" $ c_sendfile outFd inFd offsetptr (fromIntegral count)
free offsetptr
return ()
foreign import ccall unsafe "sendfile"
c_sendfile :: Fd -> Fd -> Ptr COff -> CSize -> IO CSize
#else /* Linux */
# ifdef HAVE_BSD_SENDFILE
inFd <- handleToFd inH
outFd <- handleToFd outH
offsetptr <- malloc
rc <- sendfileLoop inFd outFd (fromIntegral startpos) (fromIntegral count) offsetptr
free offsetptr
return ()
where
sendfileLoop :: Fd -> Fd -> COff -> CSize -> Ptr COff -> IO CInt
sendfileLoop inFd outFd start c offsetptr = do
rc <- c_sendfile inFd outFd start c nullPtr offsetptr 0
if rc == -1
then do
err <- getErrno
case err of
eAGAIN -> do
offset <- peek offsetptr -- now contains # of bytes written
sendfileLoop inFd outFd (start+offset) (c-(fromIntegral offset)) offsetptr
otherwise -> throwErrno "sendfile"
else
return rc
foreign import ccall unsafe "sendfile"
c_sendfile :: Fd -> Fd -> COff -> CSize -> Ptr a -> Ptr COff -> CInt -> IO CInt
# else /* BSD */
error "Sorry, sendfile(2) is not supported on your platform and currently no fallback is available"
# endif /* ERROR */
#endif
|
