1 {-# OPTIONS -fno-implicit-prelude -#include "PrelIOUtils.h" #-}
6 -- -----------------------------------------------------------------------------
7 -- $Id: PrelHandle.hs,v 1.4 2001/11/26 20:04:00 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_) (haIsStream 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 haOtherSide field of the read side point to the read side.
296 -- The finalizer is then placed on the write side, and the handle only gets
297 -- finalized once, when both sides are no longer required.
299 stdHandleFinalizer :: MVar Handle__ -> IO ()
300 stdHandleFinalizer m = do
302 flushWriteBufferOnly h_
304 handleFinalizer :: MVar Handle__ -> IO ()
305 handleFinalizer m = do
307 flushWriteBufferOnly h_
308 let fd = fromIntegral (haFD h_)
310 -- ToDo: closesocket() for a WINSOCK socket?
312 #ifdef mingw32_TARGET_OS
313 (c_close fd >> return ())
315 (closeFd (haIsStream handle_ 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 (haIsStream h_) 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_) (haIsStream 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 -> Bool -> Buffer -> IO Buffer
419 flushWriteBuffer fd is_stream 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) is_stream b (fromIntegral r)
429 (fromIntegral bytes))
431 let res' = fromIntegral res
433 then flushWriteBuffer fd is_stream (buf{ bufRPtr = r + res' })
434 else return buf{ bufRPtr=0, bufWPtr=0 }
436 foreign import "prel_PrelHandle_write" unsafe
437 write_off :: CInt -> Bool -> RawBuffer -> Int -> CInt -> IO CInt
440 fillReadBuffer :: FD -> Bool -> Bool -> Buffer -> IO Buffer
441 fillReadBuffer fd is_line is_stream
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 is_stream 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 is_stream 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 is_stream 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 is_stream 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 -> Bool -> 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 mkStdHandle fd_stdin "<stdin>" ReadHandle buf bmode
499 stdout = unsafePerformIO $ do
500 -- ToDo: acquire lock
501 -- We don't set non-blocking mode on stdout or sterr, because
502 -- some shells don't recover properly.
503 -- setNonBlockingFD fd_stdout
504 (buf, bmode) <- getBuffer fd_stdout WriteBuffer
505 mkStdHandle fd_stdout "<stdout>" WriteHandle buf bmode
508 stderr = 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_stderr
514 mkStdHandle fd_stderr "<stderr>" WriteHandle buf NoBuffering
516 -- ---------------------------------------------------------------------------
517 -- Opening and Closing Files
520 Computation `openFile file mode' allocates and returns a new, open
521 handle to manage the file `file'. It manages input if `mode'
522 is `ReadMode', output if `mode' is `WriteMode' or `AppendMode',
523 and both input and output if mode is `ReadWriteMode'.
525 If the file does not exist and it is opened for output, it should be
526 created as a new file. If `mode' is `WriteMode' and the file
527 already exists, then it should be truncated to zero length. The
528 handle is positioned at the end of the file if `mode' is
529 `AppendMode', and otherwise at the beginning (in which case its
530 internal position is 0).
532 Implementations should enforce, locally to the Haskell process,
533 multiple-reader single-writer locking on files, which is to say that
534 there may either be many handles on the same file which manage input,
535 or just one handle on the file which manages output. If any open or
536 semi-closed handle is managing a file for output, no new handle can be
537 allocated for that file. If any open or semi-closed handle is
538 managing a file for input, new handles can only be allocated if they
539 do not manage output.
541 Two files are the same if they have the same absolute name. An
542 implementation is free to impose stricter conditions.
545 data IOMode = ReadMode | WriteMode | AppendMode | ReadWriteMode
546 deriving (Eq, Ord, Ix, Enum, Read, Show)
551 deriving (Eq, Read, Show)
553 addFilePathToIOError fun fp (IOException (IOError h iot _ str _))
554 = IOException (IOError h iot fun str (Just fp))
555 addFilePathToIOError _ _ other_exception
558 openFile :: FilePath -> IOMode -> IO Handle
561 (openFile' fp (if dEFAULT_OPEN_IN_BINARY_MODE
564 (\e -> throw (addFilePathToIOError "openFile" fp e))
566 openFileEx :: FilePath -> IOModeEx -> IO Handle
570 (\e -> throw (addFilePathToIOError "openFileEx" fp e))
573 openFile' filepath ex_mode =
574 withCString filepath $ \ f ->
579 BinaryMode bmo -> (bmo, True)
580 TextMode tmo -> (tmo, False)
582 oflags1 = case mode of
583 ReadMode -> read_flags
584 WriteMode -> write_flags
585 ReadWriteMode -> rw_flags
586 AppendMode -> append_flags
588 truncate | WriteMode <- mode = True
592 | binary = PrelHandle.o_BINARY -- is '0' if not supported.
595 oflags = oflags1 .|. binary_flags
598 -- the old implementation had a complicated series of three opens,
599 -- which is perhaps because we have to be careful not to open
600 -- directories. However, the man pages I've read say that open()
601 -- always returns EISDIR if the file is a directory and was opened
602 -- for writing, so I think we're ok with a single open() here...
603 fd <- fromIntegral `liftM`
604 throwErrnoIfMinus1Retry "openFile"
605 (c_open f (fromIntegral oflags) 0o666)
607 openFd fd Nothing filepath mode binary truncate
608 -- ASSERT: if we just created the file, then openFd won't fail
609 -- (so we don't need to worry about removing the newly created file
610 -- in the event of an error).
613 std_flags = o_NONBLOCK .|. o_NOCTTY
614 output_flags = std_flags .|. o_CREAT
615 read_flags = std_flags .|. o_RDONLY
616 write_flags = output_flags .|. o_WRONLY
617 rw_flags = output_flags .|. o_RDWR
618 append_flags = write_flags .|. o_APPEND
620 -- ---------------------------------------------------------------------------
623 openFd :: FD -> Maybe FDType -> FilePath -> IOMode -> Bool -> Bool -> IO Handle
624 openFd fd mb_fd_type filepath mode binary truncate = do
625 -- turn on non-blocking mode
628 let (ha_type, write) =
630 ReadMode -> ( ReadHandle, False )
631 WriteMode -> ( WriteHandle, True )
632 ReadWriteMode -> ( ReadWriteHandle, True )
633 AppendMode -> ( AppendHandle, True )
635 -- open() won't tell us if it was a directory if we only opened for
636 -- reading, so check again.
641 let is_stream = fd_type == Stream
644 ioException (IOError Nothing InappropriateType "openFile"
645 "is a directory" Nothing)
648 | ReadWriteHandle <- ha_type -> mkDuplexHandle fd is_stream filepath binary
649 | otherwise -> mkFileHandle fd is_stream filepath ha_type binary
651 -- regular files need to be locked
653 r <- lockFile (fromIntegral fd) (fromBool write) 1{-exclusive-}
655 ioException (IOError Nothing ResourceBusy "openFile"
656 "file is locked" Nothing)
658 -- truncate the file if necessary
659 when truncate (fileTruncate filepath)
661 mkFileHandle fd is_stream filepath ha_type binary
664 foreign import "lockFile" unsafe
665 lockFile :: CInt -> CInt -> CInt -> IO CInt
667 foreign import "unlockFile" unsafe
668 unlockFile :: CInt -> IO CInt
670 mkStdHandle :: FD -> FilePath -> HandleType -> IORef Buffer -> BufferMode
672 mkStdHandle fd filepath ha_type buf bmode = do
673 spares <- newIORef BufferListNil
674 newFileHandle stdHandleFinalizer
675 (Handle__ { haFD = fd,
677 haIsBin = dEFAULT_OPEN_IN_BINARY_MODE,
679 haBufferMode = bmode,
680 haFilePath = filepath,
683 haOtherSide = Nothing
686 mkFileHandle :: FD -> Bool -> FilePath -> HandleType -> Bool -> IO Handle
687 mkFileHandle fd is_stream filepath ha_type binary = do
688 (buf, bmode) <- getBuffer fd (initBufferState ha_type)
689 spares <- newIORef BufferListNil
690 newFileHandle handleFinalizer
691 (Handle__ { haFD = fd,
694 haIsStream = is_stream,
695 haBufferMode = bmode,
696 haFilePath = filepath,
699 haOtherSide = Nothing
702 mkDuplexHandle :: FD -> Bool -> FilePath -> Bool -> IO Handle
703 mkDuplexHandle fd is_stream filepath binary = do
704 (w_buf, w_bmode) <- getBuffer fd WriteBuffer
705 w_spares <- newIORef BufferListNil
707 Handle__ { haFD = fd,
708 haType = WriteHandle,
710 haIsStream = is_stream,
711 haBufferMode = w_bmode,
712 haFilePath = filepath,
714 haBuffers = w_spares,
715 haOtherSide = Nothing
717 write_side <- newMVar w_handle_
719 (r_buf, r_bmode) <- getBuffer fd ReadBuffer
720 r_spares <- newIORef BufferListNil
722 Handle__ { haFD = fd,
725 haIsStream = is_stream,
726 haBufferMode = r_bmode,
727 haFilePath = filepath,
729 haBuffers = r_spares,
730 haOtherSide = Just write_side
732 read_side <- newMVar r_handle_
734 addMVarFinalizer read_side (handleFinalizer read_side)
735 return (DuplexHandle read_side write_side)
738 initBufferState ReadHandle = ReadBuffer
739 initBufferState _ = WriteBuffer
741 -- ---------------------------------------------------------------------------
744 -- Computation `hClose hdl' makes handle `hdl' closed. Before the
745 -- computation finishes, any items buffered for output and not already
746 -- sent to the operating system are flushed as for `hFlush'.
748 -- For a duplex handle, we close&flush the write side, and just close
751 hClose :: Handle -> IO ()
752 hClose h@(FileHandle m) = hClose' h m
753 hClose h@(DuplexHandle r w) = hClose' h w >> hClose' h r
755 hClose' h m = withHandle__' "hClose" h m $ hClose_help
757 -- hClose_help is also called by lazyRead (in PrelIO) when EOF is read
758 -- or an IO error occurs on a lazy stream. The semi-closed Handle is
759 -- then closed immediately. We have to be careful with DuplexHandles
760 -- though: we have to leave the closing to the finalizer in that case,
761 -- because the write side may still be in use.
762 hClose_help handle_ =
763 case haType handle_ of
764 ClosedHandle -> return handle_
766 let fd = fromIntegral (haFD handle_)
767 flushWriteBufferOnly handle_
769 -- close the file descriptor, but not when this is the read side
770 -- of a duplex handle.
771 case haOtherSide handle_ of
772 Nothing -> throwErrnoIfMinus1Retry_ "hClose" (closeFd (haIsStream handle_) fd)
775 -- free the spare buffers
776 writeIORef (haBuffers handle_) BufferListNil
781 -- we must set the fd to -1, because the finalizer is going
782 -- to run eventually and try to close/unlock it.
783 return (handle_{ haFD = -1,
784 haType = ClosedHandle
787 -----------------------------------------------------------------------------
788 -- Detecting the size of a file
790 -- For a handle `hdl' which attached to a physical file, `hFileSize
791 -- hdl' returns the size of `hdl' in terms of the number of items
792 -- which can be read from `hdl'.
794 hFileSize :: Handle -> IO Integer
796 withHandle_ "hFileSize" handle $ \ handle_ -> do
797 case haType handle_ of
798 ClosedHandle -> ioe_closedHandle
799 SemiClosedHandle -> ioe_closedHandle
800 _ -> do flushWriteBufferOnly handle_
801 r <- fdFileSize (haFD handle_)
804 else ioException (IOError Nothing InappropriateType "hFileSize"
805 "not a regular file" Nothing)
807 -- ---------------------------------------------------------------------------
808 -- Detecting the End of Input
810 -- For a readable handle `hdl', `hIsEOF hdl' returns
811 -- `True' if no further input can be taken from `hdl' or for a
812 -- physical file, if the current I/O position is equal to the length of
813 -- the file. Otherwise, it returns `False'.
815 hIsEOF :: Handle -> IO Bool
818 (do hLookAhead handle; return False)
819 (\e -> if isEOFError e then return True else throw e)
824 -- ---------------------------------------------------------------------------
827 -- hLookahead returns the next character from the handle without
828 -- removing it from the input buffer, blocking until a character is
831 hLookAhead :: Handle -> IO Char
832 hLookAhead handle = do
833 wantReadableHandle "hLookAhead" handle $ \handle_ -> do
834 let ref = haBuffer handle_
836 is_line = haBufferMode handle_ == LineBuffering
839 -- fill up the read buffer if necessary
840 new_buf <- if bufferEmpty buf
841 then fillReadBuffer fd is_line (haIsStream handle_) buf
844 writeIORef ref new_buf
846 (c,_) <- readCharFromBuffer (bufBuf buf) (bufRPtr buf)
849 -- ---------------------------------------------------------------------------
850 -- Buffering Operations
852 -- Three kinds of buffering are supported: line-buffering,
853 -- block-buffering or no-buffering. See PrelIOBase for definition and
854 -- further explanation of what the type represent.
856 -- Computation `hSetBuffering hdl mode' sets the mode of buffering for
857 -- handle hdl on subsequent reads and writes.
859 -- * If mode is LineBuffering, line-buffering should be enabled if possible.
861 -- * If mode is `BlockBuffering size', then block-buffering
862 -- should be enabled if possible. The size of the buffer is n items
863 -- if size is `Just n' and is otherwise implementation-dependent.
865 -- * If mode is NoBuffering, then buffering is disabled if possible.
867 -- If the buffer mode is changed from BlockBuffering or
868 -- LineBuffering to NoBuffering, then any items in the output
869 -- buffer are written to the device, and any items in the input buffer
870 -- are discarded. The default buffering mode when a handle is opened
871 -- is implementation-dependent and may depend on the object which is
872 -- attached to that handle.
874 hSetBuffering :: Handle -> BufferMode -> IO ()
875 hSetBuffering handle mode =
876 withAllHandles__ "hSetBuffering" handle $ \ handle_ -> do
877 case haType handle_ of
878 ClosedHandle -> ioe_closedHandle
881 - we flush the old buffer regardless of whether
882 the new buffer could fit the contents of the old buffer
884 - allow a handle's buffering to change even if IO has
885 occurred (ANSI C spec. does not allow this, nor did
886 the previous implementation of IO.hSetBuffering).
887 - a non-standard extension is to allow the buffering
888 of semi-closed handles to change [sof 6/98]
892 let state = initBufferState (haType handle_)
895 -- we always have a 1-character read buffer for
896 -- unbuffered handles: it's needed to
897 -- support hLookAhead.
898 NoBuffering -> allocateBuffer 1 ReadBuffer
899 LineBuffering -> allocateBuffer dEFAULT_BUFFER_SIZE state
900 BlockBuffering Nothing -> allocateBuffer dEFAULT_BUFFER_SIZE state
901 BlockBuffering (Just n) | n <= 0 -> ioe_bufsiz n
902 | otherwise -> allocateBuffer n state
903 writeIORef (haBuffer handle_) new_buf
905 -- for input terminals we need to put the terminal into
906 -- cooked or raw mode depending on the type of buffering.
907 is_tty <- fdIsTTY (haFD handle_)
908 when (is_tty && isReadableHandleType (haType handle_)) $
910 NoBuffering -> setCooked (haFD handle_) False
911 _ -> setCooked (haFD handle_) True
913 -- throw away spare buffers, they might be the wrong size
914 writeIORef (haBuffers handle_) BufferListNil
916 return (handle_{ haBufferMode = mode })
918 -- -----------------------------------------------------------------------------
921 -- The action `hFlush hdl' causes any items buffered for output
922 -- in handle `hdl' to be sent immediately to the operating
925 hFlush :: Handle -> IO ()
927 wantWritableHandle "hFlush" handle $ \ handle_ -> do
928 buf <- readIORef (haBuffer handle_)
929 if bufferIsWritable buf && not (bufferEmpty buf)
930 then do flushed_buf <- flushWriteBuffer (haFD handle_) (haIsStream handle_) buf
931 writeIORef (haBuffer handle_) flushed_buf
935 -- -----------------------------------------------------------------------------
936 -- Repositioning Handles
938 data HandlePosn = HandlePosn Handle HandlePosition
940 instance Eq HandlePosn where
941 (HandlePosn h1 p1) == (HandlePosn h2 p2) = p1==p2 && h1==h2
943 instance Show HandlePosn where
944 showsPrec p (HandlePosn h pos) =
945 showsPrec p h . showString " at position " . shows pos
947 -- HandlePosition is the Haskell equivalent of POSIX' off_t.
948 -- We represent it as an Integer on the Haskell side, but
949 -- cheat slightly in that hGetPosn calls upon a C helper
950 -- that reports the position back via (merely) an Int.
951 type HandlePosition = Integer
953 -- Computation `hGetPosn hdl' returns the current I/O position of
954 -- `hdl' as an abstract position. Computation `hSetPosn p' sets the
955 -- position of `hdl' to a previously obtained position `p'.
957 hGetPosn :: Handle -> IO HandlePosn
959 wantSeekableHandle "hGetPosn" handle $ \ handle_ -> do
961 #if defined(mingw32_TARGET_OS)
962 -- urgh, on Windows we have to worry about \n -> \r\n translation,
963 -- so we can't easily calculate the file position using the
964 -- current buffer size. Just flush instead.
967 let fd = fromIntegral (haFD handle_)
968 posn <- fromIntegral `liftM`
969 throwErrnoIfMinus1Retry "hGetPosn"
970 (c_lseek fd 0 sEEK_CUR)
972 let ref = haBuffer handle_
976 | bufferIsWritable buf = posn + fromIntegral (bufWPtr buf)
977 | otherwise = posn - fromIntegral (bufWPtr buf - bufRPtr buf)
979 puts ("\nhGetPosn: (fd, posn, real_posn) = " ++ show (fd, posn, real_posn) ++ "\n")
980 puts (" (bufWPtr, bufRPtr) = " ++ show (bufWPtr buf, bufRPtr buf) ++ "\n")
982 return (HandlePosn handle real_posn)
985 hSetPosn :: HandlePosn -> IO ()
986 hSetPosn (HandlePosn h i) = hSeek h AbsoluteSeek i
988 -- ---------------------------------------------------------------------------
992 The action `hSeek hdl mode i' sets the position of handle
993 `hdl' depending on `mode'. If `mode' is
995 * AbsoluteSeek - The position of `hdl' is set to `i'.
996 * RelativeSeek - The position of `hdl' is set to offset `i' from
997 the current position.
998 * SeekFromEnd - The position of `hdl' is set to offset `i' from
1001 Some handles may not be seekable (see `hIsSeekable'), or only
1002 support a subset of the possible positioning operations (e.g. it may
1003 only be possible to seek to the end of a tape, or to a positive
1004 offset from the beginning or current position).
1006 It is not possible to set a negative I/O position, or for a physical
1007 file, an I/O position beyond the current end-of-file.
1010 - when seeking using `SeekFromEnd', positive offsets (>=0) means
1011 seeking at or past EOF.
1013 - we possibly deviate from the report on the issue of seeking within
1014 the buffer and whether to flush it or not. The report isn't exactly
1018 data SeekMode = AbsoluteSeek | RelativeSeek | SeekFromEnd
1019 deriving (Eq, Ord, Ix, Enum, Read, Show)
1021 hSeek :: Handle -> SeekMode -> Integer -> IO ()
1022 hSeek handle mode offset =
1023 wantSeekableHandle "hSeek" handle $ \ handle_ -> do
1025 puts ("hSeek " ++ show (mode,offset) ++ "\n")
1027 let ref = haBuffer handle_
1028 buf <- readIORef ref
1034 throwErrnoIfMinus1Retry_ "hSeek"
1035 (c_lseek (fromIntegral (haFD handle_)) (fromIntegral offset) whence)
1038 whence = case mode of
1039 AbsoluteSeek -> sEEK_SET
1040 RelativeSeek -> sEEK_CUR
1041 SeekFromEnd -> sEEK_END
1043 if bufferIsWritable buf
1044 then do new_buf <- flushWriteBuffer fd (haIsStream handle_) buf
1045 writeIORef ref new_buf
1049 if mode == RelativeSeek && offset >= 0 && offset < fromIntegral (w - r)
1050 then writeIORef ref buf{ bufRPtr = r + fromIntegral offset }
1053 new_buf <- flushReadBuffer (haFD handle_) buf
1054 writeIORef ref new_buf
1057 -- -----------------------------------------------------------------------------
1058 -- Handle Properties
1060 -- A number of operations return information about the properties of a
1061 -- handle. Each of these operations returns `True' if the handle has
1062 -- the specified property, and `False' otherwise.
1064 hIsOpen :: Handle -> IO Bool
1066 withHandle_ "hIsOpen" handle $ \ handle_ -> do
1067 case haType handle_ of
1068 ClosedHandle -> return False
1069 SemiClosedHandle -> return False
1072 hIsClosed :: Handle -> IO Bool
1074 withHandle_ "hIsClosed" handle $ \ handle_ -> do
1075 case haType handle_ of
1076 ClosedHandle -> return True
1079 {- not defined, nor exported, but mentioned
1080 here for documentation purposes:
1082 hSemiClosed :: Handle -> IO Bool
1086 return (not (ho || hc))
1089 hIsReadable :: Handle -> IO Bool
1090 hIsReadable (DuplexHandle _ _) = return True
1091 hIsReadable handle =
1092 withHandle_ "hIsReadable" handle $ \ handle_ -> do
1093 case haType handle_ of
1094 ClosedHandle -> ioe_closedHandle
1095 SemiClosedHandle -> ioe_closedHandle
1096 htype -> return (isReadableHandleType htype)
1098 hIsWritable :: Handle -> IO Bool
1099 hIsWritable (DuplexHandle _ _) = return False
1100 hIsWritable handle =
1101 withHandle_ "hIsWritable" handle $ \ handle_ -> do
1102 case haType handle_ of
1103 ClosedHandle -> ioe_closedHandle
1104 SemiClosedHandle -> ioe_closedHandle
1105 htype -> return (isWritableHandleType htype)
1107 -- Querying how a handle buffers its data:
1109 hGetBuffering :: Handle -> IO BufferMode
1110 hGetBuffering handle =
1111 withHandle_ "hGetBuffering" handle $ \ handle_ -> do
1112 case haType handle_ of
1113 ClosedHandle -> ioe_closedHandle
1115 -- We're being non-standard here, and allow the buffering
1116 -- of a semi-closed handle to be queried. -- sof 6/98
1117 return (haBufferMode handle_) -- could be stricter..
1119 hIsSeekable :: Handle -> IO Bool
1120 hIsSeekable handle =
1121 withHandle_ "hIsSeekable" handle $ \ handle_ -> do
1122 case haType handle_ of
1123 ClosedHandle -> ioe_closedHandle
1124 SemiClosedHandle -> ioe_closedHandle
1125 AppendHandle -> return False
1126 _ -> do t <- fdType (haFD handle_)
1127 return (t == RegularFile
1128 && (haIsBin handle_ || tEXT_MODE_SEEK_ALLOWED))
1130 -- -----------------------------------------------------------------------------
1131 -- Changing echo status
1133 -- Non-standard GHC extension is to allow the echoing status
1134 -- of a handles connected to terminals to be reconfigured:
1136 hSetEcho :: Handle -> Bool -> IO ()
1137 hSetEcho handle on = do
1138 isT <- hIsTerminalDevice handle
1142 withHandle_ "hSetEcho" handle $ \ handle_ -> do
1143 case haType handle_ of
1144 ClosedHandle -> ioe_closedHandle
1145 _ -> setEcho (haFD handle_) on
1147 hGetEcho :: Handle -> IO Bool
1148 hGetEcho handle = do
1149 isT <- hIsTerminalDevice handle
1153 withHandle_ "hGetEcho" handle $ \ handle_ -> do
1154 case haType handle_ of
1155 ClosedHandle -> ioe_closedHandle
1156 _ -> getEcho (haFD handle_)
1158 hIsTerminalDevice :: Handle -> IO Bool
1159 hIsTerminalDevice handle = do
1160 withHandle_ "hIsTerminalDevice" handle $ \ handle_ -> do
1161 case haType handle_ of
1162 ClosedHandle -> ioe_closedHandle
1163 _ -> fdIsTTY (haFD handle_)
1165 -- -----------------------------------------------------------------------------
1167 hSetBinaryMode handle bin =
1168 withAllHandles__ "hSetBinaryMode" handle $ \ handle_ ->
1169 do throwErrnoIfMinus1_ "hSetBinaryMode"
1170 (setmode (fromIntegral (haFD handle_)) bin)
1171 return handle_{haIsBin=bin}
1173 foreign import "prel_setmode" setmode :: CInt -> Bool -> IO CInt
1175 -- -----------------------------------------------------------------------------
1178 -- These three functions are meant to get things out of an IOError.
1180 ioeGetFileName :: IOError -> Maybe FilePath
1181 ioeGetErrorString :: IOError -> String
1182 ioeGetHandle :: IOError -> Maybe Handle
1184 ioeGetHandle (IOException (IOError h _ _ _ _)) = h
1185 ioeGetHandle (UserError _) = Nothing
1186 ioeGetHandle _ = error "IO.ioeGetHandle: not an IO error"
1188 ioeGetErrorString (IOException (IOError _ iot _ _ _)) = show iot
1189 ioeGetErrorString (UserError str) = str
1190 ioeGetErrorString _ = error "IO.ioeGetErrorString: not an IO error"
1192 ioeGetFileName (IOException (IOError _ _ _ _ fn)) = fn
1193 ioeGetFileName (UserError _) = Nothing
1194 ioeGetFileName _ = error "IO.ioeGetFileName: not an IO error"
1196 -- ---------------------------------------------------------------------------
1200 puts :: String -> IO ()
1201 puts s = withCString s $ \cstr -> do c_write 1 cstr (fromIntegral (length s))
1205 -- wrappers to platform-specific constants:
1206 foreign import ccall "prel_bufsiz" unsafe dEFAULT_BUFFER_SIZE :: Int
1207 foreign import ccall "prel_seek_cur" unsafe sEEK_CUR :: CInt
1208 foreign import ccall "prel_seek_set" unsafe sEEK_SET :: CInt
1209 foreign import ccall "prel_seek_end" unsafe sEEK_END :: CInt
1210 foreign import ccall "prel_o_binary" unsafe o_BINARY :: CInt