1 {-# OPTIONS -fno-implicit-prelude -#include "PrelIOUtils.h" #-}
6 -- -----------------------------------------------------------------------------
7 -- $Id: PrelHandle.hs,v 1.2 2001/11/07 19:36:11 sof Exp $
9 -- (c) The University of Glasgow, 1994-2001
11 -- This module defines the basic operations on I/O "handles".
14 withHandle, withHandle', withHandle_,
15 wantWritableHandle, wantReadableHandle, wantSeekableHandle,
17 newEmptyBuffer, allocateBuffer, readCharFromBuffer, writeCharIntoBuffer,
18 flushWriteBufferOnly, flushWriteBuffer, flushReadBuffer, fillReadBuffer,
21 ioe_closedHandle, ioe_EOF, ioe_notReadable, ioe_notWritable,
23 stdin, stdout, stderr,
24 IOMode(..), IOModeEx(..), openFile, openFileEx, openFd,
25 hFileSize, hIsEOF, isEOF, hLookAhead, hSetBuffering, hSetBinaryMode,
30 HandlePosn(..), hGetPosn, hSetPosn,
33 hIsOpen, hIsClosed, hIsReadable, hIsWritable, hGetBuffering, hIsSeekable,
34 hSetEcho, hGetEcho, hIsTerminalDevice,
35 ioeGetFileName, ioeGetErrorString, ioeGetHandle,
49 import PrelMarshalUtils
58 import PrelRead ( Read )
61 import PrelMaybe ( Maybe(..) )
64 import PrelNum ( Integer(..), Num(..) )
66 import PrelReal ( toInteger )
70 -- -----------------------------------------------------------------------------
73 -- hWaitForInput blocks (should use a timeout)
75 -- unbuffered hGetLine is a bit dodgy
77 -- hSetBuffering: can't change buffering on a stream,
78 -- when the read buffer is non-empty? (no way to flush the buffer)
80 -- ---------------------------------------------------------------------------
81 -- Are files opened by default in text or binary mode, if the user doesn't
83 dEFAULT_OPEN_IN_BINARY_MODE :: Bool
84 dEFAULT_OPEN_IN_BINARY_MODE = False
86 -- Is seeking on text-mode handles allowed, or not?
87 foreign import ccall "prel_supportsTextMode" unsafe tEXT_MODE_SEEK_ALLOWED :: Bool
89 -- ---------------------------------------------------------------------------
90 -- Creating a new handle
92 newFileHandle :: (MVar Handle__ -> IO ()) -> Handle__ -> IO Handle
93 newFileHandle finalizer hc = do
95 addMVarFinalizer m (finalizer m)
98 -- ---------------------------------------------------------------------------
99 -- Working with Handles
102 In the concurrent world, handles are locked during use. This is done
103 by wrapping an MVar around the handle which acts as a mutex over
104 operations on the handle.
106 To avoid races, we use the following bracketing operations. The idea
107 is to obtain the lock, do some operation and replace the lock again,
108 whether the operation succeeded or failed. We also want to handle the
109 case where the thread receives an exception while processing the IO
110 operation: in these cases we also want to relinquish the lock.
112 There are three versions of @withHandle@: corresponding to the three
113 possible combinations of:
115 - the operation may side-effect the handle
116 - the operation may return a result
118 If the operation generates an error or an exception is raised, the
119 original handle is always replaced [ this is the case at the moment,
120 but we might want to revisit this in the future --SDM ].
123 {-# INLINE withHandle #-}
124 withHandle :: String -> Handle -> (Handle__ -> IO (Handle__,a)) -> IO a
125 withHandle fun h@(FileHandle m) act = withHandle' fun h m act
126 withHandle fun h@(DuplexHandle m _) act = withHandle' fun h m act
128 withHandle' fun h m act =
131 checkBufferInvariants h_
132 (h',v) <- catchException (act h_)
133 (\ ex -> putMVar m h_ >> throw (augmentIOError ex fun h h_))
134 checkBufferInvariants h'
138 {-# INLINE withHandle_ #-}
139 withHandle_ :: String -> Handle -> (Handle__ -> IO a) -> IO a
140 withHandle_ fun h@(FileHandle m) act = withHandle_' fun h m act
141 withHandle_ fun h@(DuplexHandle m _) act = withHandle_' fun h m act
143 withHandle_' fun h m act =
146 checkBufferInvariants h_
147 v <- catchException (act h_)
148 (\ ex -> putMVar m h_ >> throw (augmentIOError ex fun h h_))
149 checkBufferInvariants h_
153 withAllHandles__ :: String -> Handle -> (Handle__ -> IO Handle__) -> IO ()
154 withAllHandles__ fun h@(FileHandle m) act = withHandle__' fun h m act
155 withAllHandles__ fun h@(DuplexHandle r w) act = do
156 withHandle__' fun h r act
157 withHandle__' fun h w act
159 withHandle__' fun h m act =
162 checkBufferInvariants h_
163 h' <- catchException (act h_)
164 (\ ex -> putMVar m h_ >> throw (augmentIOError ex fun h h_))
165 checkBufferInvariants h'
169 augmentIOError (IOException (IOError _ iot _ str fp)) fun h h_
170 = IOException (IOError (Just h) iot fun str filepath)
171 where filepath | Just _ <- fp = fp
172 | otherwise = Just (haFilePath h_)
173 augmentIOError other_exception _ _ _
176 -- ---------------------------------------------------------------------------
177 -- Wrapper for write operations.
179 wantWritableHandle :: String -> Handle -> (Handle__ -> IO a) -> IO a
180 wantWritableHandle fun h@(FileHandle m) act
181 = wantWritableHandle' fun h m act
182 wantWritableHandle fun h@(DuplexHandle _ m) act
183 = wantWritableHandle' fun h m act
184 -- ToDo: in the Duplex case, we don't need to checkWritableHandle
187 :: String -> Handle -> MVar Handle__
188 -> (Handle__ -> IO a) -> IO a
189 wantWritableHandle' fun h m act
190 = withHandle_' fun h m (checkWritableHandle act)
192 checkWritableHandle act handle_
193 = case haType handle_ of
194 ClosedHandle -> ioe_closedHandle
195 SemiClosedHandle -> ioe_closedHandle
196 ReadHandle -> ioe_notWritable
197 ReadWriteHandle -> do
198 let ref = haBuffer handle_
201 if not (bufferIsWritable buf)
202 then do b <- flushReadBuffer (haFD handle_) buf
203 return b{ bufState=WriteBuffer }
205 writeIORef ref new_buf
207 _other -> act handle_
209 -- ---------------------------------------------------------------------------
210 -- Wrapper for read operations.
212 wantReadableHandle :: String -> Handle -> (Handle__ -> IO a) -> IO a
213 wantReadableHandle fun h@(FileHandle m) act
214 = wantReadableHandle' fun h m act
215 wantReadableHandle fun h@(DuplexHandle m _) act
216 = wantReadableHandle' fun h m act
217 -- ToDo: in the Duplex case, we don't need to checkReadableHandle
220 :: String -> Handle -> MVar Handle__
221 -> (Handle__ -> IO a) -> IO a
222 wantReadableHandle' fun h m act
223 = withHandle_' fun h m (checkReadableHandle act)
225 checkReadableHandle act handle_ =
226 case haType handle_ of
227 ClosedHandle -> ioe_closedHandle
228 SemiClosedHandle -> ioe_closedHandle
229 AppendHandle -> ioe_notReadable
230 WriteHandle -> ioe_notReadable
231 ReadWriteHandle -> do
232 let ref = haBuffer handle_
234 when (bufferIsWritable buf) $ do
235 new_buf <- flushWriteBuffer (haFD handle_) buf
236 writeIORef ref new_buf{ bufState=ReadBuffer }
238 _other -> act handle_
240 -- ---------------------------------------------------------------------------
241 -- Wrapper for seek operations.
243 wantSeekableHandle :: String -> Handle -> (Handle__ -> IO a) -> IO a
244 wantSeekableHandle fun h@(DuplexHandle _ _) _act =
245 ioException (IOError (Just h) IllegalOperation fun
246 "handle is not seekable" Nothing)
247 wantSeekableHandle fun h@(FileHandle m) act =
248 withHandle_' fun h m (checkSeekableHandle act)
250 checkSeekableHandle act handle_ =
251 case haType handle_ of
252 ClosedHandle -> ioe_closedHandle
253 SemiClosedHandle -> ioe_closedHandle
254 AppendHandle -> ioe_notSeekable
255 _ | haIsBin handle_ || tEXT_MODE_SEEK_ALLOWED -> act handle_
256 | otherwise -> ioe_notSeekable_notBin
258 -- -----------------------------------------------------------------------------
261 ioe_closedHandle, ioe_EOF,
262 ioe_notReadable, ioe_notWritable,
263 ioe_notSeekable, ioe_notSeekable_notBin :: IO a
265 ioe_closedHandle = ioException
266 (IOError Nothing IllegalOperation ""
267 "handle is closed" Nothing)
268 ioe_EOF = ioException
269 (IOError Nothing EOF "" "" Nothing)
270 ioe_notReadable = ioException
271 (IOError Nothing IllegalOperation ""
272 "handle is not open for reading" Nothing)
273 ioe_notWritable = ioException
274 (IOError Nothing IllegalOperation ""
275 "handle is not open for writing" Nothing)
276 ioe_notSeekable = ioException
277 (IOError Nothing IllegalOperation ""
278 "handle is not seekable" Nothing)
279 ioe_notSeekable_notBin = ioException
280 (IOError Nothing IllegalOperation ""
281 "seek operations on text-mode handles are not allowed on this platform"
284 ioe_bufsiz :: Int -> IO a
285 ioe_bufsiz n = ioException
286 (IOError Nothing InvalidArgument "hSetBuffering"
287 ("illegal buffer size " ++ showsPrec 9 n []) Nothing)
288 -- 9 => should be parens'ified.
290 -- -----------------------------------------------------------------------------
293 -- For a duplex handle, we arrange that the read side points to the write side
294 -- (and hence keeps it alive if the read side is alive). This is done by
295 -- having the haType field of the read side be ReadSideHandle with a pointer
296 -- to the write side. The finalizer is then placed on the write side, and
297 -- the handle only gets finalized once, when both sides are no longer
300 addFinalizer :: Handle -> IO ()
301 addFinalizer (FileHandle m) = addMVarFinalizer m (handleFinalizer m)
302 addFinalizer (DuplexHandle _ w) = addMVarFinalizer w (handleFinalizer w)
304 stdHandleFinalizer :: MVar Handle__ -> IO ()
305 stdHandleFinalizer m = do
307 flushWriteBufferOnly h_
309 handleFinalizer :: MVar Handle__ -> IO ()
310 handleFinalizer m = do
312 flushWriteBufferOnly h_
313 let fd = fromIntegral (haFD h_)
315 -- ToDo: closesocket() for a WINSOCK socket?
316 when (fd /= -1) (c_close fd >> return ())
319 -- ---------------------------------------------------------------------------
320 -- Grimy buffer operations
323 checkBufferInvariants h_ = do
324 let ref = haBuffer h_
325 Buffer{ bufWPtr=w, bufRPtr=r, bufSize=size, bufState=state } <- readIORef ref
330 && ( r /= w || (r == 0 && w == 0) )
331 && ( state /= WriteBuffer || r == 0 )
332 && ( state /= WriteBuffer || w < size ) -- write buffer is never full
334 then error "buffer invariant violation"
337 checkBufferInvariants h_ = return ()
340 newEmptyBuffer :: RawBuffer -> BufferState -> Int -> Buffer
341 newEmptyBuffer b state size
342 = Buffer{ bufBuf=b, bufRPtr=0, bufWPtr=0, bufSize=size, bufState=state }
344 allocateBuffer :: Int -> BufferState -> IO Buffer
345 allocateBuffer sz@(I# size) state = IO $ \s ->
346 case newByteArray# size s of { (# s, b #) ->
347 (# s, newEmptyBuffer b state sz #) }
349 writeCharIntoBuffer :: RawBuffer -> Int -> Char -> IO Int
350 writeCharIntoBuffer slab (I# off) (C# c)
351 = IO $ \s -> case writeCharArray# slab off c s of
352 s -> (# s, I# (off +# 1#) #)
354 readCharFromBuffer :: RawBuffer -> Int -> IO (Char, Int)
355 readCharFromBuffer slab (I# off)
356 = IO $ \s -> case readCharArray# slab off s of
357 (# s, c #) -> (# s, (C# c, I# (off +# 1#)) #)
359 getBuffer :: FD -> BufferState -> IO (IORef Buffer, BufferMode)
360 getBuffer fd state = do
361 buffer <- allocateBuffer dEFAULT_BUFFER_SIZE state
362 ioref <- newIORef buffer
366 | is_tty = LineBuffering
367 | otherwise = BlockBuffering Nothing
369 return (ioref, buffer_mode)
371 mkUnBuffer :: IO (IORef Buffer)
373 buffer <- allocateBuffer 1 ReadBuffer
376 -- flushWriteBufferOnly flushes the buffer iff it contains pending write data.
377 flushWriteBufferOnly :: Handle__ -> IO ()
378 flushWriteBufferOnly h_ = do
382 new_buf <- if bufferIsWritable buf
383 then flushWriteBuffer fd buf
385 writeIORef ref new_buf
387 -- flushBuffer syncs the file with the buffer, including moving the
388 -- file pointer backwards in the case of a read buffer.
389 flushBuffer :: Handle__ -> IO ()
391 let ref = haBuffer h_
396 ReadBuffer -> flushReadBuffer (haFD h_) buf
397 WriteBuffer -> flushWriteBuffer (haFD h_) buf
399 writeIORef ref flushed_buf
401 -- When flushing a read buffer, we seek backwards by the number of
402 -- characters in the buffer. The file descriptor must therefore be
403 -- seekable: attempting to flush the read buffer on an unseekable
404 -- handle is not allowed.
406 flushReadBuffer :: FD -> Buffer -> IO Buffer
407 flushReadBuffer fd buf
408 | bufferEmpty buf = return buf
410 let off = negate (bufWPtr buf - bufRPtr buf)
412 puts ("flushReadBuffer: new file offset = " ++ show off ++ "\n")
414 throwErrnoIfMinus1Retry "flushReadBuffer"
415 (c_lseek (fromIntegral fd) (fromIntegral off) sEEK_CUR)
416 return buf{ bufWPtr=0, bufRPtr=0 }
418 flushWriteBuffer :: FD -> Buffer -> IO Buffer
419 flushWriteBuffer fd buf@Buffer{ bufBuf=b, bufRPtr=r, bufWPtr=w } = do
422 puts ("flushWriteBuffer, fd=" ++ show fd ++ ", bytes=" ++ show bytes ++ "\n")
425 then return (buf{ bufRPtr=0, bufWPtr=0 })
427 res <- throwErrnoIfMinus1RetryMayBlock "flushWriteBuffer"
428 (write_off (fromIntegral fd) b (fromIntegral r)
429 (fromIntegral bytes))
431 let res' = fromIntegral res
433 then flushWriteBuffer fd (buf{ bufRPtr = r + res' })
434 else return buf{ bufRPtr=0, bufWPtr=0 }
436 foreign import "prel_PrelHandle_write" unsafe
437 write_off :: CInt -> RawBuffer -> Int -> CInt -> IO CInt
440 fillReadBuffer :: FD -> Bool -> Buffer -> IO Buffer
441 fillReadBuffer fd is_line
442 buf@Buffer{ bufBuf=b, bufRPtr=r, bufWPtr=w, bufSize=size } =
443 -- buffer better be empty:
444 assert (r == 0 && w == 0) $ do
445 fillReadBufferLoop fd is_line buf b w size
447 -- For a line buffer, we just get the first chunk of data to arrive,
448 -- and don't wait for the whole buffer to be full (but we *do* wait
449 -- until some data arrives). This isn't really line buffering, but it
450 -- appears to be what GHC has done for a long time, and I suspect it
451 -- is more useful than line buffering in most cases.
453 fillReadBufferLoop fd is_line buf b w size = do
455 if bytes == 0 -- buffer full?
456 then return buf{ bufRPtr=0, bufWPtr=w }
459 puts ("fillReadBufferLoop: bytes = " ++ show bytes ++ "\n")
461 res <- throwErrnoIfMinus1RetryMayBlock "fillReadBuffer"
462 (read_off fd b (fromIntegral w) (fromIntegral bytes))
464 let res' = fromIntegral res
466 puts ("fillReadBufferLoop: res' = " ++ show res' ++ "\n")
471 else return buf{ bufRPtr=0, bufWPtr=w }
472 else if res' < bytes && not is_line
473 then fillReadBufferLoop fd is_line buf b (w+res') size
474 else return buf{ bufRPtr=0, bufWPtr=w+res' }
476 foreign import "prel_PrelHandle_read" unsafe
477 read_off :: FD -> RawBuffer -> Int -> CInt -> IO CInt
479 -- ---------------------------------------------------------------------------
482 -- Three handles are allocated during program initialisation. The first
483 -- two manage input or output from the Haskell program's standard input
484 -- or output channel respectively. The third manages output to the
485 -- standard error channel. These handles are initially open.
492 stdin = unsafePerformIO $ do
493 -- ToDo: acquire lock
494 setNonBlockingFD fd_stdin
495 (buf, bmode) <- getBuffer fd_stdin ReadBuffer
496 spares <- newIORef BufferListNil
497 newFileHandle stdHandleFinalizer
498 (Handle__ { haFD = fd_stdin,
500 haIsBin = dEFAULT_OPEN_IN_BINARY_MODE,
501 haBufferMode = bmode,
502 haFilePath = "<stdin>",
508 stdout = unsafePerformIO $ do
509 -- ToDo: acquire lock
510 -- We don't set non-blocking mode on stdout or sterr, because
511 -- some shells don't recover properly.
512 -- setNonBlockingFD fd_stdout
513 (buf, bmode) <- getBuffer fd_stdout WriteBuffer
514 spares <- newIORef BufferListNil
515 newFileHandle stdHandleFinalizer
516 (Handle__ { haFD = fd_stdout,
517 haType = WriteHandle,
518 haIsBin = dEFAULT_OPEN_IN_BINARY_MODE,
519 haBufferMode = bmode,
520 haFilePath = "<stdout>",
526 stderr = unsafePerformIO $ do
527 -- ToDo: acquire lock
528 -- We don't set non-blocking mode on stdout or sterr, because
529 -- some shells don't recover properly.
530 -- setNonBlockingFD fd_stderr
532 spares <- newIORef BufferListNil
533 newFileHandle stdHandleFinalizer
534 (Handle__ { haFD = fd_stderr,
535 haType = WriteHandle,
536 haIsBin = dEFAULT_OPEN_IN_BINARY_MODE,
537 haBufferMode = NoBuffering,
538 haFilePath = "<stderr>",
543 -- ---------------------------------------------------------------------------
544 -- Opening and Closing Files
547 Computation `openFile file mode' allocates and returns a new, open
548 handle to manage the file `file'. It manages input if `mode'
549 is `ReadMode', output if `mode' is `WriteMode' or `AppendMode',
550 and both input and output if mode is `ReadWriteMode'.
552 If the file does not exist and it is opened for output, it should be
553 created as a new file. If `mode' is `WriteMode' and the file
554 already exists, then it should be truncated to zero length. The
555 handle is positioned at the end of the file if `mode' is
556 `AppendMode', and otherwise at the beginning (in which case its
557 internal position is 0).
559 Implementations should enforce, locally to the Haskell process,
560 multiple-reader single-writer locking on files, which is to say that
561 there may either be many handles on the same file which manage input,
562 or just one handle on the file which manages output. If any open or
563 semi-closed handle is managing a file for output, no new handle can be
564 allocated for that file. If any open or semi-closed handle is
565 managing a file for input, new handles can only be allocated if they
566 do not manage output.
568 Two files are the same if they have the same absolute name. An
569 implementation is free to impose stricter conditions.
572 data IOMode = ReadMode | WriteMode | AppendMode | ReadWriteMode
573 deriving (Eq, Ord, Ix, Enum, Read, Show)
578 deriving (Eq, Read, Show)
580 addFilePathToIOError fun fp (IOException (IOError h iot _ str _))
581 = IOException (IOError h iot fun str (Just fp))
582 addFilePathToIOError _ _ other_exception
585 openFile :: FilePath -> IOMode -> IO Handle
588 (openFile' fp (if dEFAULT_OPEN_IN_BINARY_MODE
591 (\e -> throw (addFilePathToIOError "openFile" fp e))
593 openFileEx :: FilePath -> IOModeEx -> IO Handle
597 (\e -> throw (addFilePathToIOError "openFileEx" fp e))
600 openFile' filepath ex_mode =
601 withCString filepath $ \ f ->
606 BinaryMode bmo -> (bmo, True)
607 TextMode tmo -> (tmo, False)
609 oflags1 = case mode of
610 ReadMode -> read_flags
611 WriteMode -> write_flags
612 ReadWriteMode -> rw_flags
613 AppendMode -> append_flags
615 truncate | WriteMode <- mode = True
619 | binary = PrelHandle.o_BINARY -- is '0' if not supported.
622 oflags = oflags1 .|. binary_flags
625 -- the old implementation had a complicated series of three opens,
626 -- which is perhaps because we have to be careful not to open
627 -- directories. However, the man pages I've read say that open()
628 -- always returns EISDIR if the file is a directory and was opened
629 -- for writing, so I think we're ok with a single open() here...
630 fd <- fromIntegral `liftM`
631 throwErrnoIfMinus1Retry "openFile"
632 (c_open f (fromIntegral oflags) 0o666)
634 openFd fd filepath mode binary truncate
635 -- ASSERT: if we just created the file, then openFd won't fail
636 -- (so we don't need to worry about removing the newly created file
637 -- in the event of an error).
640 std_flags = o_NONBLOCK .|. o_NOCTTY
641 output_flags = std_flags .|. o_CREAT
642 read_flags = std_flags .|. o_RDONLY
643 write_flags = output_flags .|. o_WRONLY
644 rw_flags = output_flags .|. o_RDWR
645 append_flags = write_flags .|. o_APPEND
647 -- ---------------------------------------------------------------------------
650 openFd :: FD -> FilePath -> IOMode -> Bool -> Bool -> IO Handle
651 openFd fd filepath mode binary truncate = do
652 -- turn on non-blocking mode
655 let (ha_type, write) =
657 ReadMode -> ( ReadHandle, False )
658 WriteMode -> ( WriteHandle, True )
659 ReadWriteMode -> ( ReadWriteHandle, True )
660 AppendMode -> ( AppendHandle, True )
662 -- open() won't tell us if it was a directory if we only opened for
663 -- reading, so check again.
667 ioException (IOError Nothing InappropriateType "openFile"
668 "is a directory" Nothing)
671 | ReadWriteHandle <- ha_type -> mkDuplexHandle fd filepath binary
672 | otherwise -> mkFileHandle fd filepath ha_type binary
674 -- regular files need to be locked
676 r <- lockFile (fromIntegral fd) (fromBool write) 1{-exclusive-}
678 ioException (IOError Nothing ResourceBusy "openFile"
679 "file is locked" Nothing)
681 -- truncate the file if necessary
682 when truncate (fileTruncate filepath)
684 mkFileHandle fd filepath ha_type binary
687 foreign import "lockFile" unsafe
688 lockFile :: CInt -> CInt -> CInt -> IO CInt
690 foreign import "unlockFile" unsafe
691 unlockFile :: CInt -> IO CInt
693 mkFileHandle :: FD -> FilePath -> HandleType -> Bool -> IO Handle
694 mkFileHandle fd filepath ha_type binary = do
695 (buf, bmode) <- getBuffer fd (initBufferState ha_type)
696 spares <- newIORef BufferListNil
697 newFileHandle handleFinalizer
698 (Handle__ { haFD = fd,
701 haBufferMode = bmode,
702 haFilePath = filepath,
707 mkDuplexHandle :: FD -> FilePath -> Bool -> IO Handle
708 mkDuplexHandle fd filepath binary = do
709 (w_buf, w_bmode) <- getBuffer fd WriteBuffer
710 w_spares <- newIORef BufferListNil
712 Handle__ { haFD = fd,
713 haType = WriteHandle,
715 haBufferMode = w_bmode,
716 haFilePath = filepath,
720 write_side <- newMVar w_handle_
722 (r_buf, r_bmode) <- getBuffer fd ReadBuffer
723 r_spares <- newIORef BufferListNil
725 Handle__ { haFD = fd,
726 haType = ReadSideHandle write_side,
728 haBufferMode = r_bmode,
729 haFilePath = filepath,
733 read_side <- newMVar r_handle_
735 addMVarFinalizer write_side (handleFinalizer write_side)
736 return (DuplexHandle read_side write_side)
739 initBufferState ReadHandle = ReadBuffer
740 initBufferState _ = WriteBuffer
742 -- ---------------------------------------------------------------------------
745 -- Computation `hClose hdl' makes handle `hdl' closed. Before the
746 -- computation finishes, any items buffered for output and not already
747 -- sent to the operating system are flushed as for `hFlush'.
749 -- For a duplex handle, we close&flush the write side, and just close
752 hClose :: Handle -> IO ()
753 hClose h@(FileHandle m) = hClose' h m
754 hClose h@(DuplexHandle r w) = do
756 withHandle__' "hClose" h r $ \ handle_ -> do
757 return handle_{ haFD = -1,
758 haType = ClosedHandle
761 hClose' h m = withHandle__' "hClose" h m $ hClose_help
763 hClose_help handle_ =
764 case haType handle_ of
765 ClosedHandle -> return handle_
767 let fd = fromIntegral (haFD handle_)
768 flushWriteBufferOnly handle_
769 throwErrnoIfMinus1Retry_ "hClose" (c_close fd)
771 -- free the spare buffers
772 writeIORef (haBuffers handle_) BufferListNil
777 -- we must set the fd to -1, because the finalizer is going
778 -- to run eventually and try to close/unlock it.
779 return (handle_{ haFD = -1,
780 haType = ClosedHandle
783 -----------------------------------------------------------------------------
784 -- Detecting the size of a file
786 -- For a handle `hdl' which attached to a physical file, `hFileSize
787 -- hdl' returns the size of `hdl' in terms of the number of items
788 -- which can be read from `hdl'.
790 hFileSize :: Handle -> IO Integer
792 withHandle_ "hFileSize" handle $ \ handle_ -> do
793 case haType handle_ of
794 ClosedHandle -> ioe_closedHandle
795 SemiClosedHandle -> ioe_closedHandle
796 _ -> do flushWriteBufferOnly handle_
797 r <- fdFileSize (haFD handle_)
800 else ioException (IOError Nothing InappropriateType "hFileSize"
801 "not a regular file" Nothing)
803 -- ---------------------------------------------------------------------------
804 -- Detecting the End of Input
806 -- For a readable handle `hdl', `hIsEOF hdl' returns
807 -- `True' if no further input can be taken from `hdl' or for a
808 -- physical file, if the current I/O position is equal to the length of
809 -- the file. Otherwise, it returns `False'.
811 hIsEOF :: Handle -> IO Bool
814 (do hLookAhead handle; return False)
815 (\e -> if isEOFError e then return True else throw e)
820 -- ---------------------------------------------------------------------------
823 -- hLookahead returns the next character from the handle without
824 -- removing it from the input buffer, blocking until a character is
827 hLookAhead :: Handle -> IO Char
828 hLookAhead handle = do
829 wantReadableHandle "hLookAhead" handle $ \handle_ -> do
830 let ref = haBuffer handle_
832 is_line = haBufferMode handle_ == LineBuffering
835 -- fill up the read buffer if necessary
836 new_buf <- if bufferEmpty buf
837 then fillReadBuffer fd is_line buf
840 writeIORef ref new_buf
842 (c,_) <- readCharFromBuffer (bufBuf buf) (bufRPtr buf)
845 -- ---------------------------------------------------------------------------
846 -- Buffering Operations
848 -- Three kinds of buffering are supported: line-buffering,
849 -- block-buffering or no-buffering. See PrelIOBase for definition and
850 -- further explanation of what the type represent.
852 -- Computation `hSetBuffering hdl mode' sets the mode of buffering for
853 -- handle hdl on subsequent reads and writes.
855 -- * If mode is LineBuffering, line-buffering should be enabled if possible.
857 -- * If mode is `BlockBuffering size', then block-buffering
858 -- should be enabled if possible. The size of the buffer is n items
859 -- if size is `Just n' and is otherwise implementation-dependent.
861 -- * If mode is NoBuffering, then buffering is disabled if possible.
863 -- If the buffer mode is changed from BlockBuffering or
864 -- LineBuffering to NoBuffering, then any items in the output
865 -- buffer are written to the device, and any items in the input buffer
866 -- are discarded. The default buffering mode when a handle is opened
867 -- is implementation-dependent and may depend on the object which is
868 -- attached to that handle.
870 hSetBuffering :: Handle -> BufferMode -> IO ()
871 hSetBuffering handle mode =
872 withAllHandles__ "hSetBuffering" handle $ \ handle_ -> do
873 case haType handle_ of
874 ClosedHandle -> ioe_closedHandle
877 - we flush the old buffer regardless of whether
878 the new buffer could fit the contents of the old buffer
880 - allow a handle's buffering to change even if IO has
881 occurred (ANSI C spec. does not allow this, nor did
882 the previous implementation of IO.hSetBuffering).
883 - a non-standard extension is to allow the buffering
884 of semi-closed handles to change [sof 6/98]
888 let state = initBufferState (haType handle_)
891 -- we always have a 1-character read buffer for
892 -- unbuffered handles: it's needed to
893 -- support hLookAhead.
894 NoBuffering -> allocateBuffer 1 ReadBuffer
895 LineBuffering -> allocateBuffer dEFAULT_BUFFER_SIZE state
896 BlockBuffering Nothing -> allocateBuffer dEFAULT_BUFFER_SIZE state
897 BlockBuffering (Just n) | n <= 0 -> ioe_bufsiz n
898 | otherwise -> allocateBuffer n state
899 writeIORef (haBuffer handle_) new_buf
901 -- for input terminals we need to put the terminal into
902 -- cooked or raw mode depending on the type of buffering.
903 is_tty <- fdIsTTY (haFD handle_)
904 when (is_tty && isReadableHandleType (haType handle_)) $
906 NoBuffering -> setCooked (haFD handle_) False
907 _ -> setCooked (haFD handle_) True
909 -- throw away spare buffers, they might be the wrong size
910 writeIORef (haBuffers handle_) BufferListNil
912 return (handle_{ haBufferMode = mode })
914 -- -----------------------------------------------------------------------------
917 -- The action `hFlush hdl' causes any items buffered for output
918 -- in handle `hdl' to be sent immediately to the operating
921 hFlush :: Handle -> IO ()
923 wantWritableHandle "hFlush" handle $ \ handle_ -> do
924 buf <- readIORef (haBuffer handle_)
925 if bufferIsWritable buf && not (bufferEmpty buf)
926 then do flushed_buf <- flushWriteBuffer (haFD handle_) buf
927 writeIORef (haBuffer handle_) flushed_buf
931 -- -----------------------------------------------------------------------------
932 -- Repositioning Handles
934 data HandlePosn = HandlePosn Handle HandlePosition
936 instance Eq HandlePosn where
937 (HandlePosn h1 p1) == (HandlePosn h2 p2) = p1==p2 && h1==h2
939 instance Show HandlePosn where
940 showsPrec p (HandlePosn h pos) =
941 showsPrec p h . showString " at position " . shows pos
943 -- HandlePosition is the Haskell equivalent of POSIX' off_t.
944 -- We represent it as an Integer on the Haskell side, but
945 -- cheat slightly in that hGetPosn calls upon a C helper
946 -- that reports the position back via (merely) an Int.
947 type HandlePosition = Integer
949 -- Computation `hGetPosn hdl' returns the current I/O position of
950 -- `hdl' as an abstract position. Computation `hSetPosn p' sets the
951 -- position of `hdl' to a previously obtained position `p'.
953 hGetPosn :: Handle -> IO HandlePosn
955 wantSeekableHandle "hGetPosn" handle $ \ handle_ -> do
957 #if defined(mingw32_TARGET_OS)
958 -- urgh, on Windows we have to worry about \n -> \r\n translation,
959 -- so we can't easily calculate the file position using the
960 -- current buffer size. Just flush instead.
963 let fd = fromIntegral (haFD handle_)
964 posn <- fromIntegral `liftM`
965 throwErrnoIfMinus1Retry "hGetPosn"
966 (c_lseek fd 0 sEEK_CUR)
968 let ref = haBuffer handle_
972 | bufferIsWritable buf = posn + fromIntegral (bufWPtr buf)
973 | otherwise = posn - fromIntegral (bufWPtr buf - bufRPtr buf)
975 puts ("\nhGetPosn: (fd, posn, real_posn) = " ++ show (fd, posn, real_posn) ++ "\n")
976 puts (" (bufWPtr, bufRPtr) = " ++ show (bufWPtr buf, bufRPtr buf) ++ "\n")
978 return (HandlePosn handle real_posn)
981 hSetPosn :: HandlePosn -> IO ()
982 hSetPosn (HandlePosn h i) = hSeek h AbsoluteSeek i
984 -- ---------------------------------------------------------------------------
988 The action `hSeek hdl mode i' sets the position of handle
989 `hdl' depending on `mode'. If `mode' is
991 * AbsoluteSeek - The position of `hdl' is set to `i'.
992 * RelativeSeek - The position of `hdl' is set to offset `i' from
993 the current position.
994 * SeekFromEnd - The position of `hdl' is set to offset `i' from
997 Some handles may not be seekable (see `hIsSeekable'), or only
998 support a subset of the possible positioning operations (e.g. it may
999 only be possible to seek to the end of a tape, or to a positive
1000 offset from the beginning or current position).
1002 It is not possible to set a negative I/O position, or for a physical
1003 file, an I/O position beyond the current end-of-file.
1006 - when seeking using `SeekFromEnd', positive offsets (>=0) means
1007 seeking at or past EOF.
1009 - we possibly deviate from the report on the issue of seeking within
1010 the buffer and whether to flush it or not. The report isn't exactly
1014 data SeekMode = AbsoluteSeek | RelativeSeek | SeekFromEnd
1015 deriving (Eq, Ord, Ix, Enum, Read, Show)
1017 hSeek :: Handle -> SeekMode -> Integer -> IO ()
1018 hSeek handle mode offset =
1019 wantSeekableHandle "hSeek" handle $ \ handle_ -> do
1021 puts ("hSeek " ++ show (mode,offset) ++ "\n")
1023 let ref = haBuffer handle_
1024 buf <- readIORef ref
1030 throwErrnoIfMinus1Retry_ "hSeek"
1031 (c_lseek (fromIntegral (haFD handle_)) (fromIntegral offset) whence)
1034 whence = case mode of
1035 AbsoluteSeek -> sEEK_SET
1036 RelativeSeek -> sEEK_CUR
1037 SeekFromEnd -> sEEK_END
1039 if bufferIsWritable buf
1040 then do new_buf <- flushWriteBuffer fd buf
1041 writeIORef ref new_buf
1045 if mode == RelativeSeek && offset >= 0 && offset < fromIntegral (w - r)
1046 then writeIORef ref buf{ bufRPtr = r + fromIntegral offset }
1049 new_buf <- flushReadBuffer (haFD handle_) buf
1050 writeIORef ref new_buf
1053 -- -----------------------------------------------------------------------------
1054 -- Handle Properties
1056 -- A number of operations return information about the properties of a
1057 -- handle. Each of these operations returns `True' if the handle has
1058 -- the specified property, and `False' otherwise.
1060 hIsOpen :: Handle -> IO Bool
1062 withHandle_ "hIsOpen" handle $ \ handle_ -> do
1063 case haType handle_ of
1064 ClosedHandle -> return False
1065 SemiClosedHandle -> return False
1068 hIsClosed :: Handle -> IO Bool
1070 withHandle_ "hIsClosed" handle $ \ handle_ -> do
1071 case haType handle_ of
1072 ClosedHandle -> return True
1075 {- not defined, nor exported, but mentioned
1076 here for documentation purposes:
1078 hSemiClosed :: Handle -> IO Bool
1082 return (not (ho || hc))
1085 hIsReadable :: Handle -> IO Bool
1086 hIsReadable (DuplexHandle _ _) = return True
1087 hIsReadable handle =
1088 withHandle_ "hIsReadable" handle $ \ handle_ -> do
1089 case haType handle_ of
1090 ClosedHandle -> ioe_closedHandle
1091 SemiClosedHandle -> ioe_closedHandle
1092 htype -> return (isReadableHandleType htype)
1094 hIsWritable :: Handle -> IO Bool
1095 hIsWritable (DuplexHandle _ _) = return False
1096 hIsWritable handle =
1097 withHandle_ "hIsWritable" handle $ \ handle_ -> do
1098 case haType handle_ of
1099 ClosedHandle -> ioe_closedHandle
1100 SemiClosedHandle -> ioe_closedHandle
1101 htype -> return (isWritableHandleType htype)
1103 -- Querying how a handle buffers its data:
1105 hGetBuffering :: Handle -> IO BufferMode
1106 hGetBuffering handle =
1107 withHandle_ "hGetBuffering" handle $ \ handle_ -> do
1108 case haType handle_ of
1109 ClosedHandle -> ioe_closedHandle
1111 -- We're being non-standard here, and allow the buffering
1112 -- of a semi-closed handle to be queried. -- sof 6/98
1113 return (haBufferMode handle_) -- could be stricter..
1115 hIsSeekable :: Handle -> IO Bool
1116 hIsSeekable handle =
1117 withHandle_ "hIsSeekable" handle $ \ handle_ -> do
1118 case haType handle_ of
1119 ClosedHandle -> ioe_closedHandle
1120 SemiClosedHandle -> ioe_closedHandle
1121 AppendHandle -> return False
1122 _ -> do t <- fdType (haFD handle_)
1123 return (t == RegularFile
1124 && (haIsBin handle_ || tEXT_MODE_SEEK_ALLOWED))
1126 -- -----------------------------------------------------------------------------
1127 -- Changing echo status
1129 -- Non-standard GHC extension is to allow the echoing status
1130 -- of a handles connected to terminals to be reconfigured:
1132 hSetEcho :: Handle -> Bool -> IO ()
1133 hSetEcho handle on = do
1134 isT <- hIsTerminalDevice handle
1138 withHandle_ "hSetEcho" handle $ \ handle_ -> do
1139 case haType handle_ of
1140 ClosedHandle -> ioe_closedHandle
1141 _ -> setEcho (haFD handle_) on
1143 hGetEcho :: Handle -> IO Bool
1144 hGetEcho handle = do
1145 isT <- hIsTerminalDevice handle
1149 withHandle_ "hGetEcho" handle $ \ handle_ -> do
1150 case haType handle_ of
1151 ClosedHandle -> ioe_closedHandle
1152 _ -> getEcho (haFD handle_)
1154 hIsTerminalDevice :: Handle -> IO Bool
1155 hIsTerminalDevice handle = do
1156 withHandle_ "hIsTerminalDevice" handle $ \ handle_ -> do
1157 case haType handle_ of
1158 ClosedHandle -> ioe_closedHandle
1159 _ -> fdIsTTY (haFD handle_)
1161 -- -----------------------------------------------------------------------------
1163 hSetBinaryMode handle bin =
1164 withAllHandles__ "hSetBinaryMode" handle $ \ handle_ ->
1165 do throwErrnoIfMinus1_ "hSetBinaryMode"
1166 (setmode (fromIntegral (haFD handle_)) bin)
1167 return handle_{haIsBin=bin}
1169 foreign import "prel_setmode" setmode :: CInt -> Bool -> IO CInt
1171 -- -----------------------------------------------------------------------------
1174 -- These three functions are meant to get things out of an IOError.
1176 ioeGetFileName :: IOError -> Maybe FilePath
1177 ioeGetErrorString :: IOError -> String
1178 ioeGetHandle :: IOError -> Maybe Handle
1180 ioeGetHandle (IOException (IOError h _ _ _ _)) = h
1181 ioeGetHandle (UserError _) = Nothing
1182 ioeGetHandle _ = error "IO.ioeGetHandle: not an IO error"
1184 ioeGetErrorString (IOException (IOError _ iot _ _ _)) = show iot
1185 ioeGetErrorString (UserError str) = str
1186 ioeGetErrorString _ = error "IO.ioeGetErrorString: not an IO error"
1188 ioeGetFileName (IOException (IOError _ _ _ _ fn)) = fn
1189 ioeGetFileName (UserError _) = Nothing
1190 ioeGetFileName _ = error "IO.ioeGetFileName: not an IO error"
1192 -- ---------------------------------------------------------------------------
1196 puts :: String -> IO ()
1197 puts s = withCString s $ \cstr -> do c_write 1 cstr (fromIntegral (length s))
1201 -- wrappers to platform-specific constants:
1202 foreign import ccall "prel_bufsiz" unsafe dEFAULT_BUFFER_SIZE :: Int
1203 foreign import ccall "prel_seek_cur" unsafe sEEK_CUR :: CInt
1204 foreign import ccall "prel_seek_set" unsafe sEEK_SET :: CInt
1205 foreign import ccall "prel_seek_end" unsafe sEEK_END :: CInt
1206 foreign import ccall "prel_o_binary" unsafe o_BINARY :: CInt