1 {-# OPTIONS_GHC -fno-implicit-prelude #-}
2 {-# OPTIONS_GHC -XRecordWildCards #-}
3 {-# OPTIONS_GHC -fno-warn-unused-matches #-}
4 -----------------------------------------------------------------------------
6 -- Module : GHC.IO.Handle
7 -- Copyright : (c) The University of Glasgow, 1994-2009
8 -- License : see libraries/base/LICENSE
10 -- Maintainer : libraries@haskell.org
11 -- Stability : provisional
12 -- Portability : non-portable
14 -- External API for GHC's Handle implementation
16 -----------------------------------------------------------------------------
18 module GHC.IO.Handle (
22 mkFileHandle, mkDuplexHandle,
24 hFileSize, hSetFileSize, hIsEOF, hLookAhead,
25 hSetBuffering, hSetBinaryMode, hSetEncoding,
26 hFlush, hDuplicate, hDuplicateTo,
30 HandlePosition, HandlePosn(..), hGetPosn, hSetPosn,
31 SeekMode(..), hSeek, hTell,
33 hIsOpen, hIsClosed, hIsReadable, hIsWritable, hGetBuffering, hIsSeekable,
34 hSetEcho, hGetEcho, hIsTerminalDevice,
36 hSetNewlineMode, Newline(..), NewlineMode(..), nativeNewline,
37 noNewlineTranslation, universalNewlineMode, nativeNewlineMode,
41 hWaitForInput, hGetChar, hGetLine, hGetContents, hPutChar, hPutStr,
43 hGetBuf, hGetBufNonBlocking, hPutBuf, hPutBufNonBlocking
47 import GHC.IO.Exception
48 import GHC.IO.Encoding
50 import GHC.IO.BufferedIO ( BufferedIO )
51 import GHC.IO.Device as IODevice
52 import GHC.IO.Handle.Types
53 import GHC.IO.Handle.Internals
54 import GHC.IO.Handle.Text
55 import System.IO.Error
68 -- ---------------------------------------------------------------------------
71 -- | Computation 'hClose' @hdl@ makes handle @hdl@ closed. Before the
72 -- computation finishes, if @hdl@ is writable its buffer is flushed as
74 -- Performing 'hClose' on a handle that has already been closed has no effect;
75 -- doing so is not an error. All other operations on a closed handle will fail.
76 -- If 'hClose' fails for any reason, any further operations (apart from
77 -- 'hClose') on the handle will still fail as if @hdl@ had been successfully
80 hClose :: Handle -> IO ()
81 hClose h@(FileHandle _ m) = do
83 hClose_maybethrow mb_exc h
84 hClose h@(DuplexHandle _ r w) = do
85 mb_exc1 <- hClose' h w
86 mb_exc2 <- hClose' h r
89 Just e -> hClose_maybethrow mb_exc2 h
91 hClose_maybethrow :: Maybe SomeException -> Handle -> IO ()
92 hClose_maybethrow Nothing h = return ()
93 hClose_maybethrow (Just e) h = hClose_rethrow e h
95 hClose_rethrow :: SomeException -> Handle -> IO ()
97 case fromException e of
98 Just ioe -> ioError (augmentIOError ioe "hClose" h)
101 hClose' :: Handle -> MVar Handle__ -> IO (Maybe SomeException)
102 hClose' h m = withHandle' "hClose" h m $ hClose_help
104 -----------------------------------------------------------------------------
105 -- Detecting and changing the size of a file
107 -- | For a handle @hdl@ which attached to a physical file,
108 -- 'hFileSize' @hdl@ returns the size of that file in 8-bit bytes.
110 hFileSize :: Handle -> IO Integer
112 withHandle_ "hFileSize" handle $ \ handle_@Handle__{haDevice=dev} -> do
113 case haType handle_ of
114 ClosedHandle -> ioe_closedHandle
115 SemiClosedHandle -> ioe_closedHandle
116 _ -> do flushWriteBuffer handle_
117 r <- IODevice.getSize dev
120 else ioException (IOError Nothing InappropriateType "hFileSize"
121 "not a regular file" Nothing Nothing)
124 -- | 'hSetFileSize' @hdl@ @size@ truncates the physical file with handle @hdl@ to @size@ bytes.
126 hSetFileSize :: Handle -> Integer -> IO ()
127 hSetFileSize handle size =
128 withHandle_ "hSetFileSize" handle $ \ handle_@Handle__{haDevice=dev} -> do
129 case haType handle_ of
130 ClosedHandle -> ioe_closedHandle
131 SemiClosedHandle -> ioe_closedHandle
132 _ -> do flushWriteBuffer handle_
133 IODevice.setSize dev size
136 -- ---------------------------------------------------------------------------
137 -- Detecting the End of Input
139 -- | For a readable handle @hdl@, 'hIsEOF' @hdl@ returns
140 -- 'True' if no further input can be taken from @hdl@ or for a
141 -- physical file, if the current I\/O position is equal to the length of
142 -- the file. Otherwise, it returns 'False'.
144 -- NOTE: 'hIsEOF' may block, because it is the same as calling
145 -- 'hLookAhead' and checking for an EOF exception.
147 hIsEOF :: Handle -> IO Bool
150 (do hLookAhead handle; return False)
151 (\e -> if isEOFError e then return True else ioError e)
153 -- ---------------------------------------------------------------------------
156 -- | Computation 'hLookAhead' returns the next character from the handle
157 -- without removing it from the input buffer, blocking until a character
160 -- This operation may fail with:
162 -- * 'isEOFError' if the end of file has been reached.
164 hLookAhead :: Handle -> IO Char
166 wantReadableHandle_ "hLookAhead" handle hLookAhead_
168 -- ---------------------------------------------------------------------------
169 -- Buffering Operations
171 -- Three kinds of buffering are supported: line-buffering,
172 -- block-buffering or no-buffering. See GHC.IO.Handle for definition and
173 -- further explanation of what the type represent.
175 -- | Computation 'hSetBuffering' @hdl mode@ sets the mode of buffering for
176 -- handle @hdl@ on subsequent reads and writes.
178 -- If the buffer mode is changed from 'BlockBuffering' or
179 -- 'LineBuffering' to 'NoBuffering', then
181 -- * if @hdl@ is writable, the buffer is flushed as for 'hFlush';
183 -- * if @hdl@ is not writable, the contents of the buffer is discarded.
185 -- This operation may fail with:
187 -- * 'isPermissionError' if the handle has already been used for reading
188 -- or writing and the implementation does not allow the buffering mode
191 hSetBuffering :: Handle -> BufferMode -> IO ()
192 hSetBuffering handle mode =
193 withAllHandles__ "hSetBuffering" handle $ \ handle_@Handle__{..} -> do
195 ClosedHandle -> ioe_closedHandle
197 if mode == haBufferMode then return handle_ else do
200 - we flush the old buffer regardless of whether
201 the new buffer could fit the contents of the old buffer
203 - allow a handle's buffering to change even if IO has
204 occurred (ANSI C spec. does not allow this, nor did
205 the previous implementation of IO.hSetBuffering).
206 - a non-standard extension is to allow the buffering
207 of semi-closed handles to change [sof 6/98]
209 flushCharBuffer handle_
211 let state = initBufferState haType
212 reading = not (isWritableHandleType haType)
216 -- See [note Buffer Sizing], GHC.IO.Handle.Types
217 NoBuffering | reading -> newCharBuffer dEFAULT_CHAR_BUFFER_SIZE state
218 | otherwise -> newCharBuffer 1 state
219 LineBuffering -> newCharBuffer dEFAULT_CHAR_BUFFER_SIZE state
220 BlockBuffering Nothing -> newCharBuffer dEFAULT_CHAR_BUFFER_SIZE state
221 BlockBuffering (Just n) | n <= 0 -> ioe_bufsiz n
222 | otherwise -> newCharBuffer n state
224 writeIORef haCharBuffer new_buf
226 -- for input terminals we need to put the terminal into
227 -- cooked or raw mode depending on the type of buffering.
228 is_tty <- IODevice.isTerminal haDevice
229 when (is_tty && isReadableHandleType haType) $
231 #ifndef mingw32_HOST_OS
232 -- 'raw' mode under win32 is a bit too specialised (and troublesome
233 -- for most common uses), so simply disable its use here.
234 NoBuffering -> IODevice.setRaw haDevice True
236 NoBuffering -> return ()
238 _ -> IODevice.setRaw haDevice False
240 -- throw away spare buffers, they might be the wrong size
241 writeIORef haBuffers BufferListNil
243 return Handle__{ haBufferMode = mode,.. }
245 -- -----------------------------------------------------------------------------
248 -- | The action 'hSetEncoding' @hdl@ @encoding@ changes the text encoding
249 -- for the handle @hdl@ to @encoding@. Encodings are available from the
250 -- module "GHC.IO.Encoding". The default encoding when a 'Handle' is
251 -- created is 'localeEncoding', namely the default encoding for the current
254 -- To create a 'Handle' with no encoding at all, use 'openBinaryFile'. To
255 -- stop further encoding or decoding on an existing 'Handle', use
258 hSetEncoding :: Handle -> TextEncoding -> IO ()
259 hSetEncoding hdl encoding = do
260 withHandle "hSetEncoding" hdl $ \h_@Handle__{..} -> do
262 (mb_encoder,mb_decoder) <- getEncoding (Just encoding) haType
263 return (Handle__{ haDecoder = mb_decoder, haEncoder = mb_encoder, .. },
266 -- -----------------------------------------------------------------------------
269 -- | The action 'hFlush' @hdl@ causes any items buffered for output
270 -- in handle @hdl@ to be sent immediately to the operating system.
272 -- This operation may fail with:
274 -- * 'isFullError' if the device is full;
276 -- * 'isPermissionError' if a system resource limit would be exceeded.
277 -- It is unspecified whether the characters in the buffer are discarded
278 -- or retained under these circumstances.
280 hFlush :: Handle -> IO ()
281 hFlush handle = wantWritableHandle "hFlush" handle flushWriteBuffer
283 -- -----------------------------------------------------------------------------
284 -- Repositioning Handles
286 data HandlePosn = HandlePosn Handle HandlePosition
288 instance Eq HandlePosn where
289 (HandlePosn h1 p1) == (HandlePosn h2 p2) = p1==p2 && h1==h2
291 instance Show HandlePosn where
292 showsPrec p (HandlePosn h pos) =
293 showsPrec p h . showString " at position " . shows pos
295 -- HandlePosition is the Haskell equivalent of POSIX' off_t.
296 -- We represent it as an Integer on the Haskell side, but
297 -- cheat slightly in that hGetPosn calls upon a C helper
298 -- that reports the position back via (merely) an Int.
299 type HandlePosition = Integer
301 -- | Computation 'hGetPosn' @hdl@ returns the current I\/O position of
302 -- @hdl@ as a value of the abstract type 'HandlePosn'.
304 hGetPosn :: Handle -> IO HandlePosn
307 return (HandlePosn handle posn)
309 -- | If a call to 'hGetPosn' @hdl@ returns a position @p@,
310 -- then computation 'hSetPosn' @p@ sets the position of @hdl@
311 -- to the position it held at the time of the call to 'hGetPosn'.
313 -- This operation may fail with:
315 -- * 'isPermissionError' if a system resource limit would be exceeded.
317 hSetPosn :: HandlePosn -> IO ()
318 hSetPosn (HandlePosn h i) = hSeek h AbsoluteSeek i
320 -- ---------------------------------------------------------------------------
324 - when seeking using `SeekFromEnd', positive offsets (>=0) means
325 seeking at or past EOF.
327 - we possibly deviate from the report on the issue of seeking within
328 the buffer and whether to flush it or not. The report isn't exactly
332 -- | Computation 'hSeek' @hdl mode i@ sets the position of handle
333 -- @hdl@ depending on @mode@.
334 -- The offset @i@ is given in terms of 8-bit bytes.
336 -- If @hdl@ is block- or line-buffered, then seeking to a position which is not
337 -- in the current buffer will first cause any items in the output buffer to be
338 -- written to the device, and then cause the input buffer to be discarded.
339 -- Some handles may not be seekable (see 'hIsSeekable'), or only support a
340 -- subset of the possible positioning operations (for instance, it may only
341 -- be possible to seek to the end of a tape, or to a positive offset from
342 -- the beginning or current position).
343 -- It is not possible to set a negative I\/O position, or for
344 -- a physical file, an I\/O position beyond the current end-of-file.
346 -- This operation may fail with:
348 -- * 'isPermissionError' if a system resource limit would be exceeded.
350 hSeek :: Handle -> SeekMode -> Integer -> IO ()
351 hSeek handle mode offset =
352 wantSeekableHandle "hSeek" handle $ \ handle_@Handle__{..} -> do
353 debugIO ("hSeek " ++ show (mode,offset))
354 buf <- readIORef haCharBuffer
357 then do flushWriteBuffer handle_
358 IODevice.seek haDevice mode offset
361 let r = bufL buf; w = bufR buf
362 if mode == RelativeSeek && isNothing haDecoder &&
363 offset >= 0 && offset < fromIntegral (w - r)
364 then writeIORef haCharBuffer buf{ bufL = r + fromIntegral offset }
367 flushCharReadBuffer handle_
368 flushByteReadBuffer handle_
369 IODevice.seek haDevice mode offset
372 hTell :: Handle -> IO Integer
374 wantSeekableHandle "hGetPosn" handle $ \ handle_@Handle__{..} -> do
376 posn <- IODevice.tell haDevice
378 cbuf <- readIORef haCharBuffer
379 bbuf <- readIORef haByteBuffer
382 | isWriteBuffer cbuf = posn + fromIntegral (bufR cbuf)
383 | otherwise = posn - fromIntegral (bufR cbuf - bufL cbuf)
384 - fromIntegral (bufR bbuf - bufL bbuf)
386 debugIO ("\nhGetPosn: (posn, real_posn) = " ++ show (posn, real_posn))
387 debugIO (" cbuf: " ++ summaryBuffer cbuf ++
388 " bbuf: " ++ summaryBuffer bbuf)
392 -- -----------------------------------------------------------------------------
395 -- A number of operations return information about the properties of a
396 -- handle. Each of these operations returns `True' if the handle has
397 -- the specified property, and `False' otherwise.
399 hIsOpen :: Handle -> IO Bool
401 withHandle_ "hIsOpen" handle $ \ handle_ -> do
402 case haType handle_ of
403 ClosedHandle -> return False
404 SemiClosedHandle -> return False
407 hIsClosed :: Handle -> IO Bool
409 withHandle_ "hIsClosed" handle $ \ handle_ -> do
410 case haType handle_ of
411 ClosedHandle -> return True
414 {- not defined, nor exported, but mentioned
415 here for documentation purposes:
417 hSemiClosed :: Handle -> IO Bool
421 return (not (ho || hc))
424 hIsReadable :: Handle -> IO Bool
425 hIsReadable (DuplexHandle _ _ _) = return True
427 withHandle_ "hIsReadable" handle $ \ handle_ -> do
428 case haType handle_ of
429 ClosedHandle -> ioe_closedHandle
430 SemiClosedHandle -> ioe_closedHandle
431 htype -> return (isReadableHandleType htype)
433 hIsWritable :: Handle -> IO Bool
434 hIsWritable (DuplexHandle _ _ _) = return True
436 withHandle_ "hIsWritable" handle $ \ handle_ -> do
437 case haType handle_ of
438 ClosedHandle -> ioe_closedHandle
439 SemiClosedHandle -> ioe_closedHandle
440 htype -> return (isWritableHandleType htype)
442 -- | Computation 'hGetBuffering' @hdl@ returns the current buffering mode
445 hGetBuffering :: Handle -> IO BufferMode
446 hGetBuffering handle =
447 withHandle_ "hGetBuffering" handle $ \ handle_ -> do
448 case haType handle_ of
449 ClosedHandle -> ioe_closedHandle
451 -- We're being non-standard here, and allow the buffering
452 -- of a semi-closed handle to be queried. -- sof 6/98
453 return (haBufferMode handle_) -- could be stricter..
455 hIsSeekable :: Handle -> IO Bool
457 withHandle_ "hIsSeekable" handle $ \ handle_@Handle__{..} -> do
459 ClosedHandle -> ioe_closedHandle
460 SemiClosedHandle -> ioe_closedHandle
461 AppendHandle -> return False
462 _ -> IODevice.isSeekable haDevice
464 -- -----------------------------------------------------------------------------
465 -- Changing echo status (Non-standard GHC extensions)
467 -- | Set the echoing status of a handle connected to a terminal.
469 hSetEcho :: Handle -> Bool -> IO ()
470 hSetEcho handle on = do
471 isT <- hIsTerminalDevice handle
475 withHandle_ "hSetEcho" handle $ \ Handle__{..} -> do
477 ClosedHandle -> ioe_closedHandle
478 _ -> IODevice.setEcho haDevice on
480 -- | Get the echoing status of a handle connected to a terminal.
482 hGetEcho :: Handle -> IO Bool
484 isT <- hIsTerminalDevice handle
488 withHandle_ "hGetEcho" handle $ \ Handle__{..} -> do
490 ClosedHandle -> ioe_closedHandle
491 _ -> IODevice.getEcho haDevice
493 -- | Is the handle connected to a terminal?
495 hIsTerminalDevice :: Handle -> IO Bool
496 hIsTerminalDevice handle = do
497 withHandle_ "hIsTerminalDevice" handle $ \ Handle__{..} -> do
499 ClosedHandle -> ioe_closedHandle
500 _ -> IODevice.isTerminal haDevice
502 -- -----------------------------------------------------------------------------
505 -- | Select binary mode ('True') or text mode ('False') on a open handle.
506 -- (See also 'openBinaryFile'.)
508 -- This has the same effect as calling 'hSetEncoding' with 'latin1', together
509 -- with 'hSetNewlineMode' with 'noNewlineTranslation'.
511 hSetBinaryMode :: Handle -> Bool -> IO ()
512 hSetBinaryMode handle bin =
513 withAllHandles__ "hSetBinaryMode" handle $ \ h_@Handle__{..} ->
516 let mb_te | bin = Nothing
517 | otherwise = Just localeEncoding
519 -- should match the default newline mode, whatever that is
520 let nl | bin = noNewlineTranslation
521 | otherwise = nativeNewlineMode
523 (mb_encoder, mb_decoder) <- getEncoding mb_te haType
524 return Handle__{ haEncoder = mb_encoder,
525 haDecoder = mb_decoder,
526 haInputNL = inputNL nl,
527 haOutputNL = outputNL nl, .. }
529 -- -----------------------------------------------------------------------------
532 -- | Set the 'NewlineMode' on the specified 'Handle'. All buffered
533 -- data is flushed first.
534 hSetNewlineMode :: Handle -> NewlineMode -> IO ()
535 hSetNewlineMode handle NewlineMode{ inputNL=i, outputNL=o } =
536 withAllHandles__ "hSetNewlineMode" handle $ \h_@Handle__{..} ->
539 return h_{ haInputNL=i, haOutputNL=o }
541 -- -----------------------------------------------------------------------------
542 -- Duplicating a Handle
544 -- | Returns a duplicate of the original handle, with its own buffer.
545 -- The two Handles will share a file pointer, however. The original
546 -- handle's buffer is flushed, including discarding any input data,
547 -- before the handle is duplicated.
549 hDuplicate :: Handle -> IO Handle
550 hDuplicate h@(FileHandle path m) = do
551 withHandle_' "hDuplicate" h m $ \h_ ->
552 dupHandle path h Nothing h_ (Just handleFinalizer)
553 hDuplicate h@(DuplexHandle path r w) = do
554 write_side@(FileHandle _ write_m) <-
555 withHandle_' "hDuplicate" h w $ \h_ ->
556 dupHandle path h Nothing h_ (Just handleFinalizer)
557 read_side@(FileHandle _ read_m) <-
558 withHandle_' "hDuplicate" h r $ \h_ ->
559 dupHandle path h (Just write_m) h_ Nothing
560 return (DuplexHandle path read_m write_m)
562 dupHandle :: FilePath
564 -> Maybe (MVar Handle__)
566 -> Maybe HandleFinalizer
568 dupHandle filepath h other_side h_@Handle__{..} mb_finalizer = do
569 -- flush the buffer first, so we don't have to copy its contents
573 new_dev <- IODevice.dup haDevice
574 dupHandle_ new_dev filepath other_side h_ mb_finalizer
576 withHandle_' "dupHandle" h r $ \Handle__{haDevice=dev} -> do
577 dupHandle_ dev filepath other_side h_ mb_finalizer
579 dupHandle_ :: (IODevice dev, BufferedIO dev, Typeable dev) => dev
581 -> Maybe (MVar Handle__)
583 -> Maybe HandleFinalizer
585 dupHandle_ new_dev filepath other_side h_@Handle__{..} mb_finalizer = do
587 let mb_codec = if isJust haEncoder then Just localeEncoding else Nothing
588 mkHandle new_dev filepath haType True{-buffered-} mb_codec
589 NewlineMode { inputNL = haInputNL, outputNL = haOutputNL }
590 mb_finalizer other_side
592 -- -----------------------------------------------------------------------------
593 -- Replacing a Handle
596 Makes the second handle a duplicate of the first handle. The second
597 handle will be closed first, if it is not already.
599 This can be used to retarget the standard Handles, for example:
601 > do h <- openFile "mystdout" WriteMode
602 > hDuplicateTo h stdout
605 hDuplicateTo :: Handle -> Handle -> IO ()
606 hDuplicateTo h1@(FileHandle path m1) h2@(FileHandle _ m2) = do
607 withHandle__' "hDuplicateTo" h2 m2 $ \h2_ -> do
609 withHandle_' "hDuplicateTo" h1 m1 $ \h1_ -> do
610 dupHandleTo path h1 Nothing h2_ h1_ (Just handleFinalizer)
611 hDuplicateTo h1@(DuplexHandle path r1 w1) h2@(DuplexHandle _ r2 w2) = do
612 withHandle__' "hDuplicateTo" h2 w2 $ \w2_ -> do
614 withHandle_' "hDuplicateTo" h1 w1 $ \w1_ -> do
615 dupHandleTo path h1 Nothing w2_ w1_ (Just handleFinalizer)
616 withHandle__' "hDuplicateTo" h2 r2 $ \r2_ -> do
618 withHandle_' "hDuplicateTo" h1 r1 $ \r1_ -> do
619 dupHandleTo path h1 (Just w1) r2_ r1_ Nothing
621 ioe_dupHandlesNotCompatible h1
624 ioe_dupHandlesNotCompatible :: Handle -> IO a
625 ioe_dupHandlesNotCompatible h =
626 ioException (IOError (Just h) IllegalOperation "hDuplicateTo"
627 "handles are incompatible" Nothing Nothing)
629 dupHandleTo :: FilePath
631 -> Maybe (MVar Handle__)
634 -> Maybe HandleFinalizer
636 dupHandleTo filepath h other_side
637 hto_@Handle__{haDevice=devTo,..}
638 h_@Handle__{haDevice=dev} mb_finalizer = do
641 Nothing -> ioe_dupHandlesNotCompatible h
643 IODevice.dup2 dev dev'
644 FileHandle _ m <- dupHandle_ dev' filepath other_side h_ mb_finalizer
647 -- ---------------------------------------------------------------------------
650 -- | 'hShow' is in the 'IO' monad, and gives more comprehensive output
651 -- than the (pure) instance of 'Show' for 'Handle'.
653 hShow :: Handle -> IO String
654 hShow h@(FileHandle path _) = showHandle' path False h
655 hShow h@(DuplexHandle path _ _) = showHandle' path True h
657 showHandle' :: String -> Bool -> Handle -> IO String
658 showHandle' filepath is_duplex h =
659 withHandle_ "showHandle" h $ \hdl_ ->
661 showType | is_duplex = showString "duplex (read-write)"
662 | otherwise = shows (haType hdl_)
666 showHdl (haType hdl_)
667 (showString "loc=" . showString filepath . showChar ',' .
668 showString "type=" . showType . showChar ',' .
669 showString "buffering=" . showBufMode (unsafePerformIO (readIORef (haCharBuffer hdl_))) (haBufferMode hdl_) . showString "}" )
673 showHdl :: HandleType -> ShowS -> ShowS
676 ClosedHandle -> shows ht . showString "}"
679 showBufMode :: Buffer e -> BufferMode -> ShowS
680 showBufMode buf bmo =
682 NoBuffering -> showString "none"
683 LineBuffering -> showString "line"
684 BlockBuffering (Just n) -> showString "block " . showParen True (shows n)
685 BlockBuffering Nothing -> showString "block " . showParen True (shows def)