1 {-# OPTIONS_GHC -XNoImplicitPrelude -XRecordWildCards #-}
2 {-# OPTIONS_GHC -fno-warn-unused-matches #-}
3 -----------------------------------------------------------------------------
5 -- Module : GHC.IO.Handle
6 -- Copyright : (c) The University of Glasgow, 1994-2009
7 -- License : see libraries/base/LICENSE
9 -- Maintainer : libraries@haskell.org
10 -- Stability : provisional
11 -- Portability : non-portable
13 -- External API for GHC's Handle implementation
15 -----------------------------------------------------------------------------
17 module GHC.IO.Handle (
21 mkFileHandle, mkDuplexHandle,
23 hFileSize, hSetFileSize, hIsEOF, hLookAhead,
24 hSetBuffering, hSetBinaryMode, hSetEncoding, hGetEncoding,
25 hFlush, hFlushAll, hDuplicate, hDuplicateTo,
29 HandlePosition, HandlePosn(..), hGetPosn, hSetPosn,
30 SeekMode(..), hSeek, hTell,
32 hIsOpen, hIsClosed, hIsReadable, hIsWritable, hGetBuffering, hIsSeekable,
33 hSetEcho, hGetEcho, hIsTerminalDevice,
35 hSetNewlineMode, Newline(..), NewlineMode(..), nativeNewline,
36 noNewlineTranslation, universalNewlineMode, nativeNewlineMode,
40 hWaitForInput, hGetChar, hGetLine, hGetContents, hPutChar, hPutStr,
42 hGetBuf, hGetBufNonBlocking, hPutBuf, hPutBufNonBlocking
46 import GHC.IO.Exception
47 import GHC.IO.Encoding
49 import GHC.IO.BufferedIO ( BufferedIO )
50 import GHC.IO.Device as IODevice
51 import GHC.IO.Handle.Types
52 import GHC.IO.Handle.Internals
53 import GHC.IO.Handle.Text
54 import qualified GHC.IO.BufferedIO as Buffered
67 -- ---------------------------------------------------------------------------
70 -- | Computation 'hClose' @hdl@ makes handle @hdl@ closed. Before the
71 -- computation finishes, if @hdl@ is writable its buffer is flushed as
73 -- Performing 'hClose' on a handle that has already been closed has no effect;
74 -- doing so is not an error. All other operations on a closed handle will fail.
75 -- If 'hClose' fails for any reason, any further operations (apart from
76 -- 'hClose') on the handle will still fail as if @hdl@ had been successfully
79 hClose :: Handle -> IO ()
80 hClose h@(FileHandle _ m) = do
82 hClose_maybethrow mb_exc h
83 hClose h@(DuplexHandle _ r w) = do
84 mb_exc1 <- hClose' h w
85 mb_exc2 <- hClose' h r
88 Just e -> hClose_maybethrow mb_exc2 h
90 hClose_maybethrow :: Maybe SomeException -> Handle -> IO ()
91 hClose_maybethrow Nothing h = return ()
92 hClose_maybethrow (Just e) h = hClose_rethrow e h
94 hClose_rethrow :: SomeException -> Handle -> IO ()
96 case fromException e of
97 Just ioe -> ioError (augmentIOError ioe "hClose" h)
100 hClose' :: Handle -> MVar Handle__ -> IO (Maybe SomeException)
101 hClose' h m = withHandle' "hClose" h m $ hClose_help
103 -----------------------------------------------------------------------------
104 -- Detecting and changing the size of a file
106 -- | For a handle @hdl@ which attached to a physical file,
107 -- 'hFileSize' @hdl@ returns the size of that file in 8-bit bytes.
109 hFileSize :: Handle -> IO Integer
111 withHandle_ "hFileSize" handle $ \ handle_@Handle__{haDevice=dev} -> do
112 case haType handle_ of
113 ClosedHandle -> ioe_closedHandle
114 SemiClosedHandle -> ioe_closedHandle
115 _ -> do flushWriteBuffer handle_
116 r <- IODevice.getSize dev
119 else ioException (IOError Nothing InappropriateType "hFileSize"
120 "not a regular file" Nothing Nothing)
123 -- | 'hSetFileSize' @hdl@ @size@ truncates the physical file with handle @hdl@ to @size@ bytes.
125 hSetFileSize :: Handle -> Integer -> IO ()
126 hSetFileSize handle size =
127 withHandle_ "hSetFileSize" handle $ \ handle_@Handle__{haDevice=dev} -> do
128 case haType handle_ of
129 ClosedHandle -> ioe_closedHandle
130 SemiClosedHandle -> ioe_closedHandle
131 _ -> do flushWriteBuffer handle_
132 IODevice.setSize dev size
135 -- ---------------------------------------------------------------------------
136 -- Detecting the End of Input
138 -- | For a readable handle @hdl@, 'hIsEOF' @hdl@ returns
139 -- 'True' if no further input can be taken from @hdl@ or for a
140 -- physical file, if the current I\/O position is equal to the length of
141 -- the file. Otherwise, it returns 'False'.
143 -- NOTE: 'hIsEOF' may block, because it has to attempt to read from
144 -- the stream to determine whether there is any more data to be read.
146 hIsEOF :: Handle -> IO Bool
147 hIsEOF handle = wantReadableHandle_ "hIsEOF" handle $ \Handle__{..} -> do
149 cbuf <- readIORef haCharBuffer
150 if not (isEmptyBuffer cbuf) then return False else do
152 bbuf <- readIORef haByteBuffer
153 if not (isEmptyBuffer bbuf) then return False else do
155 -- NB. do no decoding, just fill the byte buffer; see #3808
156 (r,bbuf') <- Buffered.fillReadBuffer haDevice bbuf
159 else do writeIORef haByteBuffer bbuf'
162 -- ---------------------------------------------------------------------------
165 -- | Computation 'hLookAhead' returns the next character from the handle
166 -- without removing it from the input buffer, blocking until a character
169 -- This operation may fail with:
171 -- * 'isEOFError' if the end of file has been reached.
173 hLookAhead :: Handle -> IO Char
175 wantReadableHandle_ "hLookAhead" handle hLookAhead_
177 -- ---------------------------------------------------------------------------
178 -- Buffering Operations
180 -- Three kinds of buffering are supported: line-buffering,
181 -- block-buffering or no-buffering. See GHC.IO.Handle for definition and
182 -- further explanation of what the type represent.
184 -- | Computation 'hSetBuffering' @hdl mode@ sets the mode of buffering for
185 -- handle @hdl@ on subsequent reads and writes.
187 -- If the buffer mode is changed from 'BlockBuffering' or
188 -- 'LineBuffering' to 'NoBuffering', then
190 -- * if @hdl@ is writable, the buffer is flushed as for 'hFlush';
192 -- * if @hdl@ is not writable, the contents of the buffer is discarded.
194 -- This operation may fail with:
196 -- * 'isPermissionError' if the handle has already been used for reading
197 -- or writing and the implementation does not allow the buffering mode
200 hSetBuffering :: Handle -> BufferMode -> IO ()
201 hSetBuffering handle mode =
202 withAllHandles__ "hSetBuffering" handle $ \ handle_@Handle__{..} -> do
204 ClosedHandle -> ioe_closedHandle
206 if mode == haBufferMode then return handle_ else do
209 - we flush the old buffer regardless of whether
210 the new buffer could fit the contents of the old buffer
212 - allow a handle's buffering to change even if IO has
213 occurred (ANSI C spec. does not allow this, nor did
214 the previous implementation of IO.hSetBuffering).
215 - a non-standard extension is to allow the buffering
216 of semi-closed handles to change [sof 6/98]
218 flushCharBuffer handle_
220 let state = initBufferState haType
221 reading = not (isWritableHandleType haType)
225 -- See [note Buffer Sizing], GHC.IO.Handle.Types
226 NoBuffering | reading -> newCharBuffer dEFAULT_CHAR_BUFFER_SIZE state
227 | otherwise -> newCharBuffer 1 state
228 LineBuffering -> newCharBuffer dEFAULT_CHAR_BUFFER_SIZE state
229 BlockBuffering Nothing -> newCharBuffer dEFAULT_CHAR_BUFFER_SIZE state
230 BlockBuffering (Just n) | n <= 0 -> ioe_bufsiz n
231 | otherwise -> newCharBuffer n state
233 writeIORef haCharBuffer new_buf
235 -- for input terminals we need to put the terminal into
236 -- cooked or raw mode depending on the type of buffering.
237 is_tty <- IODevice.isTerminal haDevice
238 when (is_tty && isReadableHandleType haType) $
240 #ifndef mingw32_HOST_OS
241 -- 'raw' mode under win32 is a bit too specialised (and troublesome
242 -- for most common uses), so simply disable its use here.
243 NoBuffering -> IODevice.setRaw haDevice True
245 NoBuffering -> return ()
247 _ -> IODevice.setRaw haDevice False
249 -- throw away spare buffers, they might be the wrong size
250 writeIORef haBuffers BufferListNil
252 return Handle__{ haBufferMode = mode,.. }
254 -- -----------------------------------------------------------------------------
257 -- | The action 'hSetEncoding' @hdl@ @encoding@ changes the text encoding
258 -- for the handle @hdl@ to @encoding@. The default encoding when a 'Handle' is
259 -- created is 'localeEncoding', namely the default encoding for the current
262 -- To create a 'Handle' with no encoding at all, use 'openBinaryFile'. To
263 -- stop further encoding or decoding on an existing 'Handle', use
266 -- 'hSetEncoding' may need to flush buffered data in order to change
269 hSetEncoding :: Handle -> TextEncoding -> IO ()
270 hSetEncoding hdl encoding = do
271 withAllHandles__ "hSetEncoding" hdl $ \h_@Handle__{..} -> do
273 openTextEncoding (Just encoding) haType $ \ mb_encoder mb_decoder -> do
274 bbuf <- readIORef haByteBuffer
275 ref <- newIORef (error "last_decode")
276 return (Handle__{ haLastDecode = ref,
277 haDecoder = mb_decoder,
278 haEncoder = mb_encoder,
279 haCodec = Just encoding, .. })
281 -- | Return the current 'TextEncoding' for the specified 'Handle', or
282 -- 'Nothing' if the 'Handle' is in binary mode.
284 -- Note that the 'TextEncoding' remembers nothing about the state of
285 -- the encoder/decoder in use on this 'Handle'. For example, if the
286 -- encoding in use is UTF-16, then using 'hGetEncoding' and
287 -- 'hSetEncoding' to save and restore the encoding may result in an
288 -- extra byte-order-mark being written to the file.
290 hGetEncoding :: Handle -> IO (Maybe TextEncoding)
292 withHandle_ "hGetEncoding" hdl $ \h_@Handle__{..} -> return haCodec
294 -- -----------------------------------------------------------------------------
297 -- | The action 'hFlush' @hdl@ causes any items buffered for output
298 -- in handle @hdl@ to be sent immediately to the operating system.
300 -- This operation may fail with:
302 -- * 'isFullError' if the device is full;
304 -- * 'isPermissionError' if a system resource limit would be exceeded.
305 -- It is unspecified whether the characters in the buffer are discarded
306 -- or retained under these circumstances.
308 hFlush :: Handle -> IO ()
309 hFlush handle = wantWritableHandle "hFlush" handle flushWriteBuffer
311 -- | The action 'hFlushAll' @hdl@ flushes all buffered data in @hdl@,
312 -- including any buffered read data. Buffered read data is flushed
313 -- by seeking the file position back to the point before the bufferred
314 -- data was read, and hence only works if @hdl@ is seekable (see
317 -- This operation may fail with:
319 -- * 'isFullError' if the device is full;
321 -- * 'isPermissionError' if a system resource limit would be exceeded.
322 -- It is unspecified whether the characters in the buffer are discarded
323 -- or retained under these circumstances;
325 -- * 'isIllegalOperation' if @hdl@ has buffered read data, and is not
328 hFlushAll :: Handle -> IO ()
329 hFlushAll handle = withHandle_ "hFlushAll" handle flushBuffer
331 -- -----------------------------------------------------------------------------
332 -- Repositioning Handles
334 data HandlePosn = HandlePosn Handle HandlePosition
336 instance Eq HandlePosn where
337 (HandlePosn h1 p1) == (HandlePosn h2 p2) = p1==p2 && h1==h2
339 instance Show HandlePosn where
340 showsPrec p (HandlePosn h pos) =
341 showsPrec p h . showString " at position " . shows pos
343 -- HandlePosition is the Haskell equivalent of POSIX' off_t.
344 -- We represent it as an Integer on the Haskell side, but
345 -- cheat slightly in that hGetPosn calls upon a C helper
346 -- that reports the position back via (merely) an Int.
347 type HandlePosition = Integer
349 -- | Computation 'hGetPosn' @hdl@ returns the current I\/O position of
350 -- @hdl@ as a value of the abstract type 'HandlePosn'.
352 hGetPosn :: Handle -> IO HandlePosn
355 return (HandlePosn handle posn)
357 -- | If a call to 'hGetPosn' @hdl@ returns a position @p@,
358 -- then computation 'hSetPosn' @p@ sets the position of @hdl@
359 -- to the position it held at the time of the call to 'hGetPosn'.
361 -- This operation may fail with:
363 -- * 'isPermissionError' if a system resource limit would be exceeded.
365 hSetPosn :: HandlePosn -> IO ()
366 hSetPosn (HandlePosn h i) = hSeek h AbsoluteSeek i
368 -- ---------------------------------------------------------------------------
372 - when seeking using `SeekFromEnd', positive offsets (>=0) means
373 seeking at or past EOF.
375 - we possibly deviate from the report on the issue of seeking within
376 the buffer and whether to flush it or not. The report isn't exactly
380 -- | Computation 'hSeek' @hdl mode i@ sets the position of handle
381 -- @hdl@ depending on @mode@.
382 -- The offset @i@ is given in terms of 8-bit bytes.
384 -- If @hdl@ is block- or line-buffered, then seeking to a position which is not
385 -- in the current buffer will first cause any items in the output buffer to be
386 -- written to the device, and then cause the input buffer to be discarded.
387 -- Some handles may not be seekable (see 'hIsSeekable'), or only support a
388 -- subset of the possible positioning operations (for instance, it may only
389 -- be possible to seek to the end of a tape, or to a positive offset from
390 -- the beginning or current position).
391 -- It is not possible to set a negative I\/O position, or for
392 -- a physical file, an I\/O position beyond the current end-of-file.
394 -- This operation may fail with:
396 -- * 'isPermissionError' if a system resource limit would be exceeded.
398 hSeek :: Handle -> SeekMode -> Integer -> IO ()
399 hSeek handle mode offset =
400 wantSeekableHandle "hSeek" handle $ \ handle_@Handle__{..} -> do
401 debugIO ("hSeek " ++ show (mode,offset))
402 buf <- readIORef haCharBuffer
405 then do flushWriteBuffer handle_
406 IODevice.seek haDevice mode offset
409 let r = bufL buf; w = bufR buf
410 if mode == RelativeSeek && isNothing haDecoder &&
411 offset >= 0 && offset < fromIntegral (w - r)
412 then writeIORef haCharBuffer buf{ bufL = r + fromIntegral offset }
415 flushCharReadBuffer handle_
416 flushByteReadBuffer handle_
417 IODevice.seek haDevice mode offset
420 hTell :: Handle -> IO Integer
422 wantSeekableHandle "hGetPosn" handle $ \ handle_@Handle__{..} -> do
424 posn <- IODevice.tell haDevice
426 cbuf <- readIORef haCharBuffer
427 bbuf <- readIORef haByteBuffer
430 | isWriteBuffer cbuf = posn + fromIntegral (bufR cbuf)
431 | otherwise = posn - fromIntegral (bufR cbuf - bufL cbuf)
432 - fromIntegral (bufR bbuf - bufL bbuf)
434 debugIO ("\nhGetPosn: (posn, real_posn) = " ++ show (posn, real_posn))
435 debugIO (" cbuf: " ++ summaryBuffer cbuf ++
436 " bbuf: " ++ summaryBuffer bbuf)
440 -- -----------------------------------------------------------------------------
443 -- A number of operations return information about the properties of a
444 -- handle. Each of these operations returns `True' if the handle has
445 -- the specified property, and `False' otherwise.
447 hIsOpen :: Handle -> IO Bool
449 withHandle_ "hIsOpen" handle $ \ handle_ -> do
450 case haType handle_ of
451 ClosedHandle -> return False
452 SemiClosedHandle -> return False
455 hIsClosed :: Handle -> IO Bool
457 withHandle_ "hIsClosed" handle $ \ handle_ -> do
458 case haType handle_ of
459 ClosedHandle -> return True
462 {- not defined, nor exported, but mentioned
463 here for documentation purposes:
465 hSemiClosed :: Handle -> IO Bool
469 return (not (ho || hc))
472 hIsReadable :: Handle -> IO Bool
473 hIsReadable (DuplexHandle _ _ _) = return True
475 withHandle_ "hIsReadable" handle $ \ handle_ -> do
476 case haType handle_ of
477 ClosedHandle -> ioe_closedHandle
478 SemiClosedHandle -> ioe_closedHandle
479 htype -> return (isReadableHandleType htype)
481 hIsWritable :: Handle -> IO Bool
482 hIsWritable (DuplexHandle _ _ _) = return True
484 withHandle_ "hIsWritable" handle $ \ handle_ -> do
485 case haType handle_ of
486 ClosedHandle -> ioe_closedHandle
487 SemiClosedHandle -> ioe_closedHandle
488 htype -> return (isWritableHandleType htype)
490 -- | Computation 'hGetBuffering' @hdl@ returns the current buffering mode
493 hGetBuffering :: Handle -> IO BufferMode
494 hGetBuffering handle =
495 withHandle_ "hGetBuffering" handle $ \ handle_ -> do
496 case haType handle_ of
497 ClosedHandle -> ioe_closedHandle
499 -- We're being non-standard here, and allow the buffering
500 -- of a semi-closed handle to be queried. -- sof 6/98
501 return (haBufferMode handle_) -- could be stricter..
503 hIsSeekable :: Handle -> IO Bool
505 withHandle_ "hIsSeekable" handle $ \ handle_@Handle__{..} -> do
507 ClosedHandle -> ioe_closedHandle
508 SemiClosedHandle -> ioe_closedHandle
509 AppendHandle -> return False
510 _ -> IODevice.isSeekable haDevice
512 -- -----------------------------------------------------------------------------
513 -- Changing echo status (Non-standard GHC extensions)
515 -- | Set the echoing status of a handle connected to a terminal.
517 hSetEcho :: Handle -> Bool -> IO ()
518 hSetEcho handle on = do
519 isT <- hIsTerminalDevice handle
523 withHandle_ "hSetEcho" handle $ \ Handle__{..} -> do
525 ClosedHandle -> ioe_closedHandle
526 _ -> IODevice.setEcho haDevice on
528 -- | Get the echoing status of a handle connected to a terminal.
530 hGetEcho :: Handle -> IO Bool
532 isT <- hIsTerminalDevice handle
536 withHandle_ "hGetEcho" handle $ \ Handle__{..} -> do
538 ClosedHandle -> ioe_closedHandle
539 _ -> IODevice.getEcho haDevice
541 -- | Is the handle connected to a terminal?
543 hIsTerminalDevice :: Handle -> IO Bool
544 hIsTerminalDevice handle = do
545 withHandle_ "hIsTerminalDevice" handle $ \ Handle__{..} -> do
547 ClosedHandle -> ioe_closedHandle
548 _ -> IODevice.isTerminal haDevice
550 -- -----------------------------------------------------------------------------
553 -- | Select binary mode ('True') or text mode ('False') on a open handle.
554 -- (See also 'openBinaryFile'.)
556 -- This has the same effect as calling 'hSetEncoding' with 'latin1', together
557 -- with 'hSetNewlineMode' with 'noNewlineTranslation'.
559 hSetBinaryMode :: Handle -> Bool -> IO ()
560 hSetBinaryMode handle bin =
561 withAllHandles__ "hSetBinaryMode" handle $ \ h_@Handle__{..} ->
565 let mb_te | bin = Nothing
566 | otherwise = Just localeEncoding
568 openTextEncoding mb_te haType $ \ mb_encoder mb_decoder -> do
570 -- should match the default newline mode, whatever that is
571 let nl | bin = noNewlineTranslation
572 | otherwise = nativeNewlineMode
574 bbuf <- readIORef haByteBuffer
575 ref <- newIORef (error "codec_state", bbuf)
577 return Handle__{ haLastDecode = ref,
578 haEncoder = mb_encoder,
579 haDecoder = mb_decoder,
581 haInputNL = inputNL nl,
582 haOutputNL = outputNL nl, .. }
584 -- -----------------------------------------------------------------------------
587 -- | Set the 'NewlineMode' on the specified 'Handle'. All buffered
588 -- data is flushed first.
589 hSetNewlineMode :: Handle -> NewlineMode -> IO ()
590 hSetNewlineMode handle NewlineMode{ inputNL=i, outputNL=o } =
591 withAllHandles__ "hSetNewlineMode" handle $ \h_@Handle__{..} ->
594 return h_{ haInputNL=i, haOutputNL=o }
596 -- -----------------------------------------------------------------------------
597 -- Duplicating a Handle
599 -- | Returns a duplicate of the original handle, with its own buffer.
600 -- The two Handles will share a file pointer, however. The original
601 -- handle's buffer is flushed, including discarding any input data,
602 -- before the handle is duplicated.
604 hDuplicate :: Handle -> IO Handle
605 hDuplicate h@(FileHandle path m) = do
606 withHandle_' "hDuplicate" h m $ \h_ ->
607 dupHandle path h Nothing h_ (Just handleFinalizer)
608 hDuplicate h@(DuplexHandle path r w) = do
609 write_side@(FileHandle _ write_m) <-
610 withHandle_' "hDuplicate" h w $ \h_ ->
611 dupHandle path h Nothing h_ (Just handleFinalizer)
612 read_side@(FileHandle _ read_m) <-
613 withHandle_' "hDuplicate" h r $ \h_ ->
614 dupHandle path h (Just write_m) h_ Nothing
615 return (DuplexHandle path read_m write_m)
617 dupHandle :: FilePath
619 -> Maybe (MVar Handle__)
621 -> Maybe HandleFinalizer
623 dupHandle filepath h other_side h_@Handle__{..} mb_finalizer = do
624 -- flush the buffer first, so we don't have to copy its contents
628 new_dev <- IODevice.dup haDevice
629 dupHandle_ new_dev filepath other_side h_ mb_finalizer
631 withHandle_' "dupHandle" h r $ \Handle__{haDevice=dev} -> do
632 dupHandle_ dev filepath other_side h_ mb_finalizer
634 dupHandle_ :: (IODevice dev, BufferedIO dev, Typeable dev) => dev
636 -> Maybe (MVar Handle__)
638 -> Maybe HandleFinalizer
640 dupHandle_ new_dev filepath other_side h_@Handle__{..} mb_finalizer = do
642 let mb_codec = if isJust haEncoder then Just localeEncoding else Nothing
643 mkHandle new_dev filepath haType True{-buffered-} mb_codec
644 NewlineMode { inputNL = haInputNL, outputNL = haOutputNL }
645 mb_finalizer other_side
647 -- -----------------------------------------------------------------------------
648 -- Replacing a Handle
651 Makes the second handle a duplicate of the first handle. The second
652 handle will be closed first, if it is not already.
654 This can be used to retarget the standard Handles, for example:
656 > do h <- openFile "mystdout" WriteMode
657 > hDuplicateTo h stdout
660 hDuplicateTo :: Handle -> Handle -> IO ()
661 hDuplicateTo h1@(FileHandle path m1) h2@(FileHandle _ m2) = do
662 withHandle__' "hDuplicateTo" h2 m2 $ \h2_ -> do
664 withHandle_' "hDuplicateTo" h1 m1 $ \h1_ -> do
665 dupHandleTo path h1 Nothing h2_ h1_ (Just handleFinalizer)
666 hDuplicateTo h1@(DuplexHandle path r1 w1) h2@(DuplexHandle _ r2 w2) = do
667 withHandle__' "hDuplicateTo" h2 w2 $ \w2_ -> do
669 withHandle_' "hDuplicateTo" h1 w1 $ \w1_ -> do
670 dupHandleTo path h1 Nothing w2_ w1_ (Just handleFinalizer)
671 withHandle__' "hDuplicateTo" h2 r2 $ \r2_ -> do
673 withHandle_' "hDuplicateTo" h1 r1 $ \r1_ -> do
674 dupHandleTo path h1 (Just w1) r2_ r1_ Nothing
676 ioe_dupHandlesNotCompatible h1
679 ioe_dupHandlesNotCompatible :: Handle -> IO a
680 ioe_dupHandlesNotCompatible h =
681 ioException (IOError (Just h) IllegalOperation "hDuplicateTo"
682 "handles are incompatible" Nothing Nothing)
684 dupHandleTo :: FilePath
686 -> Maybe (MVar Handle__)
689 -> Maybe HandleFinalizer
691 dupHandleTo filepath h other_side
692 hto_@Handle__{haDevice=devTo,..}
693 h_@Handle__{haDevice=dev} mb_finalizer = do
696 Nothing -> ioe_dupHandlesNotCompatible h
698 _ <- IODevice.dup2 dev dev'
699 FileHandle _ m <- dupHandle_ dev' filepath other_side h_ mb_finalizer
702 -- ---------------------------------------------------------------------------
705 -- | 'hShow' is in the 'IO' monad, and gives more comprehensive output
706 -- than the (pure) instance of 'Show' for 'Handle'.
708 hShow :: Handle -> IO String
709 hShow h@(FileHandle path _) = showHandle' path False h
710 hShow h@(DuplexHandle path _ _) = showHandle' path True h
712 showHandle' :: String -> Bool -> Handle -> IO String
713 showHandle' filepath is_duplex h =
714 withHandle_ "showHandle" h $ \hdl_ ->
716 showType | is_duplex = showString "duplex (read-write)"
717 | otherwise = shows (haType hdl_)
721 showHdl (haType hdl_)
722 (showString "loc=" . showString filepath . showChar ',' .
723 showString "type=" . showType . showChar ',' .
724 showString "buffering=" . showBufMode (unsafePerformIO (readIORef (haCharBuffer hdl_))) (haBufferMode hdl_) . showString "}" )
728 showHdl :: HandleType -> ShowS -> ShowS
731 ClosedHandle -> shows ht . showString "}"
734 showBufMode :: Buffer e -> BufferMode -> ShowS
735 showBufMode buf bmo =
737 NoBuffering -> showString "none"
738 LineBuffering -> showString "line"
739 BlockBuffering (Just n) -> showString "block " . showParen True (shows n)
740 BlockBuffering Nothing -> showString "block " . showParen True (shows def)