1 {-# OPTIONS_GHC -fno-implicit-prelude -#include "HsBase.h" #-}
6 -----------------------------------------------------------------------------
9 -- Copyright : (c) The University of Glasgow, 1994-2001
10 -- License : see libraries/base/LICENSE
12 -- Maintainer : libraries@haskell.org
13 -- Stability : internal
14 -- Portability : non-portable
16 -- This module defines the basic operations on I\/O \"handles\".
18 -----------------------------------------------------------------------------
22 withHandle, withHandle', withHandle_,
23 wantWritableHandle, wantReadableHandle, wantSeekableHandle,
25 newEmptyBuffer, allocateBuffer, readCharFromBuffer, writeCharIntoBuffer,
26 flushWriteBufferOnly, flushWriteBuffer, flushReadBuffer,
27 fillReadBuffer, fillReadBufferWithoutBlocking,
28 readRawBuffer, readRawBufferPtr,
29 writeRawBuffer, writeRawBufferPtr,
31 #ifndef mingw32_HOST_OS
35 ioe_closedHandle, ioe_EOF, ioe_notReadable, ioe_notWritable,
37 stdin, stdout, stderr,
38 IOMode(..), openFile, openBinaryFile, openTempFile, openBinaryTempFile, openFd, fdToHandle,
39 hFileSize, hSetFileSize, hIsEOF, isEOF, hLookAhead, hSetBuffering, hSetBinaryMode,
40 hFlush, hDuplicate, hDuplicateTo,
44 HandlePosition, HandlePosn(..), hGetPosn, hSetPosn,
45 SeekMode(..), hSeek, hTell,
47 hIsOpen, hIsClosed, hIsReadable, hIsWritable, hGetBuffering, hIsSeekable,
48 hSetEcho, hGetEcho, hIsTerminalDevice,
58 import System.Directory.Internals
64 import System.IO.Error
65 import System.Posix.Internals
71 import GHC.Read ( Read )
76 import GHC.Num ( Integer(..), Num(..) )
78 import GHC.Real ( toInteger )
79 #if defined(DEBUG_DUMP)
85 -- -----------------------------------------------------------------------------
88 -- hWaitForInput blocks (should use a timeout)
90 -- unbuffered hGetLine is a bit dodgy
92 -- hSetBuffering: can't change buffering on a stream,
93 -- when the read buffer is non-empty? (no way to flush the buffer)
95 -- ---------------------------------------------------------------------------
96 -- Are files opened by default in text or binary mode, if the user doesn't
99 dEFAULT_OPEN_IN_BINARY_MODE = False :: Bool
101 -- ---------------------------------------------------------------------------
102 -- Creating a new handle
104 newFileHandle :: FilePath -> (MVar Handle__ -> IO ()) -> Handle__ -> IO Handle
105 newFileHandle filepath finalizer hc = do
107 addMVarFinalizer m (finalizer m)
108 return (FileHandle filepath m)
110 -- ---------------------------------------------------------------------------
111 -- Working with Handles
114 In the concurrent world, handles are locked during use. This is done
115 by wrapping an MVar around the handle which acts as a mutex over
116 operations on the handle.
118 To avoid races, we use the following bracketing operations. The idea
119 is to obtain the lock, do some operation and replace the lock again,
120 whether the operation succeeded or failed. We also want to handle the
121 case where the thread receives an exception while processing the IO
122 operation: in these cases we also want to relinquish the lock.
124 There are three versions of @withHandle@: corresponding to the three
125 possible combinations of:
127 - the operation may side-effect the handle
128 - the operation may return a result
130 If the operation generates an error or an exception is raised, the
131 original handle is always replaced [ this is the case at the moment,
132 but we might want to revisit this in the future --SDM ].
135 {-# INLINE withHandle #-}
136 withHandle :: String -> Handle -> (Handle__ -> IO (Handle__,a)) -> IO a
137 withHandle fun h@(FileHandle _ m) act = withHandle' fun h m act
138 withHandle fun h@(DuplexHandle _ m _) act = withHandle' fun h m act
140 withHandle' :: String -> Handle -> MVar Handle__
141 -> (Handle__ -> IO (Handle__,a)) -> IO a
142 withHandle' fun h m act =
145 checkBufferInvariants h_
146 (h',v) <- catchException (act h_)
147 (\ err -> putMVar m h_ >>
149 IOException ex -> ioError (augmentIOError ex fun h)
151 checkBufferInvariants h'
155 {-# INLINE withHandle_ #-}
156 withHandle_ :: String -> Handle -> (Handle__ -> IO a) -> IO a
157 withHandle_ fun h@(FileHandle _ m) act = withHandle_' fun h m act
158 withHandle_ fun h@(DuplexHandle _ m _) act = withHandle_' fun h m act
160 withHandle_' :: String -> Handle -> MVar Handle__ -> (Handle__ -> IO a) -> IO a
161 withHandle_' fun h m act =
164 checkBufferInvariants h_
165 v <- catchException (act h_)
166 (\ err -> putMVar m h_ >>
168 IOException ex -> ioError (augmentIOError ex fun h)
170 checkBufferInvariants h_
174 withAllHandles__ :: String -> Handle -> (Handle__ -> IO Handle__) -> IO ()
175 withAllHandles__ fun h@(FileHandle _ m) act = withHandle__' fun h m act
176 withAllHandles__ fun h@(DuplexHandle _ r w) act = do
177 withHandle__' fun h r act
178 withHandle__' fun h w act
180 withHandle__' fun h m act =
183 checkBufferInvariants h_
184 h' <- catchException (act h_)
185 (\ err -> putMVar m h_ >>
187 IOException ex -> ioError (augmentIOError ex fun h)
189 checkBufferInvariants h'
193 augmentIOError (IOError _ iot _ str fp) fun h
194 = IOError (Just h) iot fun str filepath
197 | otherwise = case h of
198 FileHandle fp _ -> Just fp
199 DuplexHandle fp _ _ -> Just fp
201 -- ---------------------------------------------------------------------------
202 -- Wrapper for write operations.
204 wantWritableHandle :: String -> Handle -> (Handle__ -> IO a) -> IO a
205 wantWritableHandle fun h@(FileHandle _ m) act
206 = wantWritableHandle' fun h m act
207 wantWritableHandle fun h@(DuplexHandle _ _ m) act
208 = wantWritableHandle' fun h m act
209 -- ToDo: in the Duplex case, we don't need to checkWritableHandle
212 :: String -> Handle -> MVar Handle__
213 -> (Handle__ -> IO a) -> IO a
214 wantWritableHandle' fun h m act
215 = withHandle_' fun h m (checkWritableHandle act)
217 checkWritableHandle act handle_
218 = case haType handle_ of
219 ClosedHandle -> ioe_closedHandle
220 SemiClosedHandle -> ioe_closedHandle
221 ReadHandle -> ioe_notWritable
222 ReadWriteHandle -> do
223 let ref = haBuffer handle_
226 if not (bufferIsWritable buf)
227 then do b <- flushReadBuffer (haFD handle_) buf
228 return b{ bufState=WriteBuffer }
230 writeIORef ref new_buf
232 _other -> act handle_
234 -- ---------------------------------------------------------------------------
235 -- Wrapper for read operations.
237 wantReadableHandle :: String -> Handle -> (Handle__ -> IO a) -> IO a
238 wantReadableHandle fun h@(FileHandle _ m) act
239 = wantReadableHandle' fun h m act
240 wantReadableHandle fun h@(DuplexHandle _ m _) act
241 = wantReadableHandle' fun h m act
242 -- ToDo: in the Duplex case, we don't need to checkReadableHandle
245 :: String -> Handle -> MVar Handle__
246 -> (Handle__ -> IO a) -> IO a
247 wantReadableHandle' fun h m act
248 = withHandle_' fun h m (checkReadableHandle act)
250 checkReadableHandle act handle_ =
251 case haType handle_ of
252 ClosedHandle -> ioe_closedHandle
253 SemiClosedHandle -> ioe_closedHandle
254 AppendHandle -> ioe_notReadable
255 WriteHandle -> ioe_notReadable
256 ReadWriteHandle -> do
257 let ref = haBuffer handle_
259 when (bufferIsWritable buf) $ do
260 new_buf <- flushWriteBuffer (haFD handle_) (haIsStream handle_) buf
261 writeIORef ref new_buf{ bufState=ReadBuffer }
263 _other -> act handle_
265 -- ---------------------------------------------------------------------------
266 -- Wrapper for seek operations.
268 wantSeekableHandle :: String -> Handle -> (Handle__ -> IO a) -> IO a
269 wantSeekableHandle fun h@(DuplexHandle _ _ _) _act =
270 ioException (IOError (Just h) IllegalOperation fun
271 "handle is not seekable" Nothing)
272 wantSeekableHandle fun h@(FileHandle _ m) act =
273 withHandle_' fun h m (checkSeekableHandle act)
275 checkSeekableHandle act handle_ =
276 case haType handle_ of
277 ClosedHandle -> ioe_closedHandle
278 SemiClosedHandle -> ioe_closedHandle
279 AppendHandle -> ioe_notSeekable
280 _ | haIsBin handle_ || tEXT_MODE_SEEK_ALLOWED -> act handle_
281 | otherwise -> ioe_notSeekable_notBin
283 -- -----------------------------------------------------------------------------
286 ioe_closedHandle, ioe_EOF,
287 ioe_notReadable, ioe_notWritable,
288 ioe_notSeekable, ioe_notSeekable_notBin :: IO a
290 ioe_closedHandle = ioException
291 (IOError Nothing IllegalOperation ""
292 "handle is closed" Nothing)
293 ioe_EOF = ioException
294 (IOError Nothing EOF "" "" Nothing)
295 ioe_notReadable = ioException
296 (IOError Nothing IllegalOperation ""
297 "handle is not open for reading" Nothing)
298 ioe_notWritable = ioException
299 (IOError Nothing IllegalOperation ""
300 "handle is not open for writing" Nothing)
301 ioe_notSeekable = ioException
302 (IOError Nothing IllegalOperation ""
303 "handle is not seekable" Nothing)
304 ioe_notSeekable_notBin = ioException
305 (IOError Nothing IllegalOperation ""
306 "seek operations on text-mode handles are not allowed on this platform"
309 ioe_finalizedHandle fp = throw (IOException
310 (IOError Nothing IllegalOperation ""
311 "handle is finalized" (Just fp)))
313 ioe_bufsiz :: Int -> IO a
314 ioe_bufsiz n = ioException
315 (IOError Nothing InvalidArgument "hSetBuffering"
316 ("illegal buffer size " ++ showsPrec 9 n []) Nothing)
317 -- 9 => should be parens'ified.
319 -- -----------------------------------------------------------------------------
322 -- For a duplex handle, we arrange that the read side points to the write side
323 -- (and hence keeps it alive if the read side is alive). This is done by
324 -- having the haOtherSide field of the read side point to the read side.
325 -- The finalizer is then placed on the write side, and the handle only gets
326 -- finalized once, when both sides are no longer required.
328 -- NOTE about finalized handles: It's possible that a handle can be
329 -- finalized and then we try to use it later, for example if the
330 -- handle is referenced from another finalizer, or from a thread that
331 -- has become unreferenced and then resurrected (arguably in the
332 -- latter case we shouldn't finalize the Handle...). Anyway,
333 -- we try to emit a helpful message which is better than nothing.
335 stdHandleFinalizer :: FilePath -> MVar Handle__ -> IO ()
336 stdHandleFinalizer fp m = do
338 flushWriteBufferOnly h_
339 putMVar m (ioe_finalizedHandle fp)
341 handleFinalizer :: FilePath -> MVar Handle__ -> IO ()
342 handleFinalizer fp m = do
343 handle_ <- takeMVar m
344 case haType handle_ of
345 ClosedHandle -> return ()
346 _ -> do flushWriteBufferOnly handle_ `catchException` \_ -> return ()
347 -- ignore errors and async exceptions, and close the
348 -- descriptor anyway...
349 hClose_handle_ handle_
351 putMVar m (ioe_finalizedHandle fp)
353 -- ---------------------------------------------------------------------------
354 -- Grimy buffer operations
357 checkBufferInvariants h_ = do
358 let ref = haBuffer h_
359 Buffer{ bufWPtr=w, bufRPtr=r, bufSize=size, bufState=state } <- readIORef ref
364 && ( r /= w || (r == 0 && w == 0) )
365 && ( state /= WriteBuffer || r == 0 )
366 && ( state /= WriteBuffer || w < size ) -- write buffer is never full
368 then error "buffer invariant violation"
371 checkBufferInvariants h_ = return ()
374 newEmptyBuffer :: RawBuffer -> BufferState -> Int -> Buffer
375 newEmptyBuffer b state size
376 = Buffer{ bufBuf=b, bufRPtr=0, bufWPtr=0, bufSize=size, bufState=state }
378 allocateBuffer :: Int -> BufferState -> IO Buffer
379 allocateBuffer sz@(I# size) state = IO $ \s ->
380 #ifdef mingw32_HOST_OS
381 -- To implement asynchronous I/O under Win32, we have to pass
382 -- buffer references to external threads that handles the
383 -- filling/emptying of their contents. Hence, the buffer cannot
384 -- be moved around by the GC.
385 case newPinnedByteArray# size s of { (# s, b #) ->
387 case newByteArray# size s of { (# s, b #) ->
389 (# s, newEmptyBuffer b state sz #) }
391 writeCharIntoBuffer :: RawBuffer -> Int -> Char -> IO Int
392 writeCharIntoBuffer slab (I# off) (C# c)
393 = IO $ \s -> case writeCharArray# slab off c s of
394 s -> (# s, I# (off +# 1#) #)
396 readCharFromBuffer :: RawBuffer -> Int -> IO (Char, Int)
397 readCharFromBuffer slab (I# off)
398 = IO $ \s -> case readCharArray# slab off s of
399 (# s, c #) -> (# s, (C# c, I# (off +# 1#)) #)
401 getBuffer :: FD -> BufferState -> IO (IORef Buffer, BufferMode)
402 getBuffer fd state = do
403 buffer <- allocateBuffer dEFAULT_BUFFER_SIZE state
404 ioref <- newIORef buffer
408 | is_tty = LineBuffering
409 | otherwise = BlockBuffering Nothing
411 return (ioref, buffer_mode)
413 mkUnBuffer :: IO (IORef Buffer)
415 buffer <- allocateBuffer 1 ReadBuffer
418 -- flushWriteBufferOnly flushes the buffer iff it contains pending write data.
419 flushWriteBufferOnly :: Handle__ -> IO ()
420 flushWriteBufferOnly h_ = do
424 new_buf <- if bufferIsWritable buf
425 then flushWriteBuffer fd (haIsStream h_) buf
427 writeIORef ref new_buf
429 -- flushBuffer syncs the file with the buffer, including moving the
430 -- file pointer backwards in the case of a read buffer.
431 flushBuffer :: Handle__ -> IO ()
433 let ref = haBuffer h_
438 ReadBuffer -> flushReadBuffer (haFD h_) buf
439 WriteBuffer -> flushWriteBuffer (haFD h_) (haIsStream h_) buf
441 writeIORef ref flushed_buf
443 -- When flushing a read buffer, we seek backwards by the number of
444 -- characters in the buffer. The file descriptor must therefore be
445 -- seekable: attempting to flush the read buffer on an unseekable
446 -- handle is not allowed.
448 flushReadBuffer :: FD -> Buffer -> IO Buffer
449 flushReadBuffer fd buf
450 | bufferEmpty buf = return buf
452 let off = negate (bufWPtr buf - bufRPtr buf)
454 puts ("flushReadBuffer: new file offset = " ++ show off ++ "\n")
456 throwErrnoIfMinus1Retry "flushReadBuffer"
457 (c_lseek fd (fromIntegral off) sEEK_CUR)
458 return buf{ bufWPtr=0, bufRPtr=0 }
460 flushWriteBuffer :: FD -> Bool -> Buffer -> IO Buffer
461 flushWriteBuffer fd is_stream buf@Buffer{ bufBuf=b, bufRPtr=r, bufWPtr=w } =
462 seq fd $ do -- strictness hack
465 puts ("flushWriteBuffer, fd=" ++ show fd ++ ", bytes=" ++ show bytes ++ "\n")
468 then return (buf{ bufRPtr=0, bufWPtr=0 })
470 res <- writeRawBuffer "flushWriteBuffer" fd is_stream b
471 (fromIntegral r) (fromIntegral bytes)
472 let res' = fromIntegral res
474 then flushWriteBuffer fd is_stream (buf{ bufRPtr = r + res' })
475 else return buf{ bufRPtr=0, bufWPtr=0 }
477 fillReadBuffer :: FD -> Bool -> Bool -> Buffer -> IO Buffer
478 fillReadBuffer fd is_line is_stream
479 buf@Buffer{ bufBuf=b, bufRPtr=r, bufWPtr=w, bufSize=size } =
480 -- buffer better be empty:
481 assert (r == 0 && w == 0) $ do
482 fillReadBufferLoop fd is_line is_stream buf b w size
484 -- For a line buffer, we just get the first chunk of data to arrive,
485 -- and don't wait for the whole buffer to be full (but we *do* wait
486 -- until some data arrives). This isn't really line buffering, but it
487 -- appears to be what GHC has done for a long time, and I suspect it
488 -- is more useful than line buffering in most cases.
490 fillReadBufferLoop fd is_line is_stream buf b w size = do
492 if bytes == 0 -- buffer full?
493 then return buf{ bufRPtr=0, bufWPtr=w }
496 puts ("fillReadBufferLoop: bytes = " ++ show bytes ++ "\n")
498 res <- readRawBuffer "fillReadBuffer" fd is_stream b
499 (fromIntegral w) (fromIntegral bytes)
500 let res' = fromIntegral res
502 puts ("fillReadBufferLoop: res' = " ++ show res' ++ "\n")
507 else return buf{ bufRPtr=0, bufWPtr=w }
508 else if res' < bytes && not is_line
509 then fillReadBufferLoop fd is_line is_stream buf b (w+res') size
510 else return buf{ bufRPtr=0, bufWPtr=w+res' }
513 fillReadBufferWithoutBlocking :: FD -> Bool -> Buffer -> IO Buffer
514 fillReadBufferWithoutBlocking fd is_stream
515 buf@Buffer{ bufBuf=b, bufRPtr=r, bufWPtr=w, bufSize=size } =
516 -- buffer better be empty:
517 assert (r == 0 && w == 0) $ do
519 puts ("fillReadBufferLoopNoBlock: bytes = " ++ show size ++ "\n")
521 res <- readRawBufferNoBlock "fillReadBuffer" fd is_stream b
522 0 (fromIntegral size)
523 let res' = fromIntegral res
525 puts ("fillReadBufferLoopNoBlock: res' = " ++ show res' ++ "\n")
527 return buf{ bufRPtr=0, bufWPtr=res' }
529 -- Low level routines for reading/writing to (raw)buffers:
531 #ifndef mingw32_HOST_OS
536 Unix has broken semantics when it comes to non-blocking I/O: you can
537 set the O_NONBLOCK flag on an FD, but it applies to the all other FDs
538 attached to the same underlying file, pipe or TTY; there's no way to
539 have private non-blocking behaviour for an FD. See bug #724.
541 We fix this by only setting O_NONBLOCK on FDs that we create; FDs that
542 come from external sources or are exposed externally are left in
543 blocking mode. This solution has some problems though. We can't
544 completely simulate a non-blocking read without O_NONBLOCK: several
545 cases are wrong here. The cases that are wrong:
547 * reading/writing to a blocking FD in non-threaded mode.
548 In threaded mode, we just make a safe call to read().
549 In non-threaded mode we call select() before attempting to read,
550 but that leaves a small race window where the data can be read
551 from the file descriptor before we issue our blocking read().
552 * readRawBufferNoBlock for a blocking FD
555 readRawBuffer :: String -> FD -> Bool -> RawBuffer -> Int -> CInt -> IO CInt
556 readRawBuffer loc fd is_nonblock buf off len
557 | is_nonblock = unsafe_read
558 | threaded = safe_read
559 | otherwise = do r <- throwErrnoIfMinus1 loc
560 (fdReady (fromIntegral fd) 0 0 False)
563 else do threadWaitRead (fromIntegral fd); unsafe_read
565 unsafe_read = throwErrnoIfMinus1RetryMayBlock loc
566 (read_rawBuffer fd buf off len)
567 (threadWaitRead (fromIntegral fd))
568 safe_read = throwErrnoIfMinus1Retry loc
569 (safe_read_rawBuffer fd buf off len)
571 readRawBufferPtr :: String -> FD -> Bool -> Ptr CChar -> Int -> CInt -> IO CInt
572 readRawBufferPtr loc fd is_nonblock buf off len
573 | is_nonblock = unsafe_read
574 | threaded = safe_read
575 | otherwise = do r <- throwErrnoIfMinus1 loc
576 (fdReady (fromIntegral fd) 0 0 False)
579 else do threadWaitRead (fromIntegral fd); unsafe_read
581 unsafe_read = throwErrnoIfMinus1RetryMayBlock loc
582 (read_off fd buf off len)
583 (threadWaitRead (fromIntegral fd))
584 safe_read = throwErrnoIfMinus1Retry loc
585 (safe_read_off fd buf off len)
587 readRawBufferNoBlock :: String -> FD -> Bool -> RawBuffer -> Int -> CInt -> IO CInt
588 readRawBufferNoBlock loc fd is_nonblock buf off len
589 | is_nonblock = unsafe_read
590 | otherwise = do r <- fdReady (fromIntegral fd) 0 0 False
591 if r /= 0 then safe_read
593 -- XXX see note [nonblock]
595 unsafe_read = throwErrnoIfMinus1RetryOnBlock loc
596 (read_rawBuffer fd buf off len)
598 safe_read = throwErrnoIfMinus1Retry loc
599 (safe_read_rawBuffer fd buf off len)
601 writeRawBuffer :: String -> FD -> Bool -> RawBuffer -> Int -> CInt -> IO CInt
602 writeRawBuffer loc fd is_nonblock buf off len
603 | is_nonblock = unsafe_write
604 | threaded = safe_write
605 | otherwise = do r <- fdReady (fromIntegral fd) 1 0 False
606 if r /= 0 then safe_write
609 unsafe_write = throwErrnoIfMinus1RetryMayBlock loc
610 (write_rawBuffer fd buf off len)
611 (threadWaitWrite (fromIntegral fd))
612 safe_write = throwErrnoIfMinus1Retry loc
613 (safe_write_rawBuffer (fromIntegral fd) buf off len)
615 writeRawBufferPtr :: String -> FD -> Bool -> Ptr CChar -> Int -> CInt -> IO CInt
616 writeRawBufferPtr loc fd is_nonblock buf off len
617 | is_nonblock = unsafe_write
618 | threaded = safe_write
619 | otherwise = do r <- fdReady (fromIntegral fd) 1 0 False
620 if r /= 0 then safe_write
623 unsafe_write = throwErrnoIfMinus1RetryMayBlock loc
624 (write_off fd buf off len)
625 (threadWaitWrite (fromIntegral fd))
626 safe_write = throwErrnoIfMinus1Retry loc
627 (safe_write_off (fromIntegral fd) buf off len)
629 foreign import ccall unsafe "__hscore_PrelHandle_read"
630 read_rawBuffer :: CInt -> RawBuffer -> Int -> CInt -> IO CInt
632 foreign import ccall unsafe "__hscore_PrelHandle_read"
633 read_off :: CInt -> Ptr CChar -> Int -> CInt -> IO CInt
635 foreign import ccall unsafe "__hscore_PrelHandle_write"
636 write_rawBuffer :: CInt -> RawBuffer -> Int -> CInt -> IO CInt
638 foreign import ccall unsafe "__hscore_PrelHandle_write"
639 write_off :: CInt -> Ptr CChar -> Int -> CInt -> IO CInt
641 foreign import ccall safe "fdReady"
642 fdReady :: CInt -> CInt -> CInt -> Bool -> IO CInt
644 #else /* mingw32_HOST_OS.... */
646 readRawBuffer :: String -> FD -> Bool -> RawBuffer -> Int -> CInt -> IO CInt
647 readRawBuffer loc fd is_stream buf off len
648 | threaded = blockingReadRawBuffer loc fd is_stream buf off len
649 | otherwise = asyncReadRawBuffer loc fd is_stream buf off len
651 readRawBufferPtr :: String -> FD -> Bool -> Ptr CChar -> Int -> CInt -> IO CInt
652 readRawBufferPtr loc fd is_stream buf off len
653 | threaded = blockingReadRawBufferPtr loc fd is_stream buf off len
654 | otherwise = asyncReadRawBufferPtr loc fd is_stream buf off len
656 writeRawBuffer :: String -> FD -> Bool -> RawBuffer -> Int -> CInt -> IO CInt
657 writeRawBuffer loc fd is_stream buf off len
658 | threaded = blockingWriteRawBuffer loc fd is_stream buf off len
659 | otherwise = asyncWriteRawBuffer loc fd is_stream buf off len
661 writeRawBufferPtr :: String -> FD -> Bool -> Ptr CChar -> Int -> CInt -> IO CInt
662 writeRawBufferPtr loc fd is_stream buf off len
663 | threaded = blockingWriteRawBufferPtr loc fd is_stream buf off len
664 | otherwise = asyncWriteRawBufferPtr loc fd is_stream buf off len
666 -- ToDo: we don't have a non-blocking primitve read on Win32
667 readRawBufferNoBlock :: String -> FD -> Bool -> RawBuffer -> Int -> CInt -> IO CInt
668 readRawBufferNoBlock = readRawBuffer
670 -- Async versions of the read/write primitives, for the non-threaded RTS
672 asyncReadRawBuffer loc fd is_stream buf off len = do
673 (l, rc) <- asyncReadBA (fromIntegral fd) (if is_stream then 1 else 0)
674 (fromIntegral len) off buf
677 ioError (errnoToIOError loc (Errno (fromIntegral rc)) Nothing Nothing)
678 else return (fromIntegral l)
680 asyncReadRawBufferPtr loc fd is_stream buf off len = do
681 (l, rc) <- asyncRead (fromIntegral fd) (if is_stream then 1 else 0)
682 (fromIntegral len) (buf `plusPtr` off)
685 ioError (errnoToIOError loc (Errno (fromIntegral rc)) Nothing Nothing)
686 else return (fromIntegral l)
688 asyncWriteRawBuffer loc fd is_stream buf off len = do
689 (l, rc) <- asyncWriteBA (fromIntegral fd) (if is_stream then 1 else 0)
690 (fromIntegral len) off buf
693 ioError (errnoToIOError loc (Errno (fromIntegral rc)) Nothing Nothing)
694 else return (fromIntegral l)
696 asyncWriteRawBufferPtr loc fd is_stream buf off len = do
697 (l, rc) <- asyncWrite (fromIntegral fd) (if is_stream then 1 else 0)
698 (fromIntegral len) (buf `plusPtr` off)
701 ioError (errnoToIOError loc (Errno (fromIntegral rc)) Nothing Nothing)
702 else return (fromIntegral l)
704 -- Blocking versions of the read/write primitives, for the threaded RTS
706 blockingReadRawBuffer loc fd True buf off len =
707 throwErrnoIfMinus1Retry loc $
708 safe_recv_rawBuffer fd buf off len
709 blockingReadRawBuffer loc fd False buf off len =
710 throwErrnoIfMinus1Retry loc $
711 safe_read_rawBuffer fd buf off len
713 blockingReadRawBufferPtr loc fd True buf off len =
714 throwErrnoIfMinus1Retry loc $
715 safe_recv_off fd buf off len
716 blockingReadRawBufferPtr loc fd False buf off len =
717 throwErrnoIfMinus1Retry loc $
718 safe_read_off fd buf off len
720 blockingWriteRawBuffer loc fd True buf off len =
721 throwErrnoIfMinus1Retry loc $
722 safe_send_rawBuffer fd buf off len
723 blockingWriteRawBuffer loc fd False buf off len =
724 throwErrnoIfMinus1Retry loc $
725 safe_write_rawBuffer fd buf off len
727 blockingWriteRawBufferPtr loc fd True buf off len =
728 throwErrnoIfMinus1Retry loc $
729 safe_send_off fd buf off len
730 blockingWriteRawBufferPtr loc fd False buf off len =
731 throwErrnoIfMinus1Retry loc $
732 safe_write_off fd buf off len
734 -- NOTE: "safe" versions of the read/write calls for use by the threaded RTS.
735 -- These calls may block, but that's ok.
737 foreign import ccall safe "__hscore_PrelHandle_recv"
738 safe_recv_rawBuffer :: CInt -> RawBuffer -> Int -> CInt -> IO CInt
740 foreign import ccall safe "__hscore_PrelHandle_recv"
741 safe_recv_off :: CInt -> Ptr CChar -> Int -> CInt -> IO CInt
743 foreign import ccall safe "__hscore_PrelHandle_send"
744 safe_send_rawBuffer :: CInt -> RawBuffer -> Int -> CInt -> IO CInt
746 foreign import ccall safe "__hscore_PrelHandle_send"
747 safe_send_off :: CInt -> Ptr CChar -> Int -> CInt -> IO CInt
751 foreign import ccall "rtsSupportsBoundThreads" threaded :: Bool
753 foreign import ccall safe "__hscore_PrelHandle_read"
754 safe_read_rawBuffer :: FD -> RawBuffer -> Int -> CInt -> IO CInt
756 foreign import ccall safe "__hscore_PrelHandle_read"
757 safe_read_off :: FD -> Ptr CChar -> Int -> CInt -> IO CInt
759 foreign import ccall safe "__hscore_PrelHandle_write"
760 safe_write_rawBuffer :: CInt -> RawBuffer -> Int -> CInt -> IO CInt
762 foreign import ccall safe "__hscore_PrelHandle_write"
763 safe_write_off :: CInt -> Ptr CChar -> Int -> CInt -> IO CInt
765 -- ---------------------------------------------------------------------------
768 -- Three handles are allocated during program initialisation. The first
769 -- two manage input or output from the Haskell program's standard input
770 -- or output channel respectively. The third manages output to the
771 -- standard error channel. These handles are initially open.
777 -- | A handle managing input from the Haskell program's standard input channel.
779 stdin = unsafePerformIO $ do
780 -- ToDo: acquire lock
781 -- We don't set non-blocking mode on standard handles, because it may
782 -- confuse other applications attached to the same TTY/pipe
783 -- see Note [nonblock]
784 (buf, bmode) <- getBuffer fd_stdin ReadBuffer
785 mkStdHandle fd_stdin "<stdin>" ReadHandle buf bmode
787 -- | A handle managing output to the Haskell program's standard output channel.
789 stdout = unsafePerformIO $ do
790 -- ToDo: acquire lock
791 -- We don't set non-blocking mode on standard handles, because it may
792 -- confuse other applications attached to the same TTY/pipe
793 -- see Note [nonblock]
794 (buf, bmode) <- getBuffer fd_stdout WriteBuffer
795 mkStdHandle fd_stdout "<stdout>" WriteHandle buf bmode
797 -- | A handle managing output to the Haskell program's standard error channel.
799 stderr = unsafePerformIO $ do
800 -- ToDo: acquire lock
801 -- We don't set non-blocking mode on standard handles, because it may
802 -- confuse other applications attached to the same TTY/pipe
803 -- see Note [nonblock]
805 mkStdHandle fd_stderr "<stderr>" WriteHandle buf NoBuffering
807 -- ---------------------------------------------------------------------------
808 -- Opening and Closing Files
810 addFilePathToIOError fun fp (IOError h iot _ str _)
811 = IOError h iot fun str (Just fp)
813 -- | Computation 'openFile' @file mode@ allocates and returns a new, open
814 -- handle to manage the file @file@. It manages input if @mode@
815 -- is 'ReadMode', output if @mode@ is 'WriteMode' or 'AppendMode',
816 -- and both input and output if mode is 'ReadWriteMode'.
818 -- If the file does not exist and it is opened for output, it should be
819 -- created as a new file. If @mode@ is 'WriteMode' and the file
820 -- already exists, then it should be truncated to zero length.
821 -- Some operating systems delete empty files, so there is no guarantee
822 -- that the file will exist following an 'openFile' with @mode@
823 -- 'WriteMode' unless it is subsequently written to successfully.
824 -- The handle is positioned at the end of the file if @mode@ is
825 -- 'AppendMode', and otherwise at the beginning (in which case its
826 -- internal position is 0).
827 -- The initial buffer mode is implementation-dependent.
829 -- This operation may fail with:
831 -- * 'isAlreadyInUseError' if the file is already open and cannot be reopened;
833 -- * 'isDoesNotExistError' if the file does not exist; or
835 -- * 'isPermissionError' if the user does not have permission to open the file.
837 -- Note: if you will be working with files containing binary data, you'll want to
838 -- be using 'openBinaryFile'.
839 openFile :: FilePath -> IOMode -> IO Handle
842 (openFile' fp im dEFAULT_OPEN_IN_BINARY_MODE)
843 (\e -> ioError (addFilePathToIOError "openFile" fp e))
845 -- | Like 'openFile', but open the file in binary mode.
846 -- On Windows, reading a file in text mode (which is the default)
847 -- will translate CRLF to LF, and writing will translate LF to CRLF.
848 -- This is usually what you want with text files. With binary files
849 -- this is undesirable; also, as usual under Microsoft operating systems,
850 -- text mode treats control-Z as EOF. Binary mode turns off all special
851 -- treatment of end-of-line and end-of-file characters.
852 -- (See also 'hSetBinaryMode'.)
854 openBinaryFile :: FilePath -> IOMode -> IO Handle
855 openBinaryFile fp m =
857 (openFile' fp m True)
858 (\e -> ioError (addFilePathToIOError "openBinaryFile" fp e))
860 openFile' filepath mode binary =
861 withCString filepath $ \ f ->
864 oflags1 = case mode of
865 ReadMode -> read_flags
866 #ifdef mingw32_HOST_OS
867 WriteMode -> write_flags .|. o_TRUNC
869 WriteMode -> write_flags
871 ReadWriteMode -> rw_flags
872 AppendMode -> append_flags
878 oflags = oflags1 .|. binary_flags
881 -- the old implementation had a complicated series of three opens,
882 -- which is perhaps because we have to be careful not to open
883 -- directories. However, the man pages I've read say that open()
884 -- always returns EISDIR if the file is a directory and was opened
885 -- for writing, so I think we're ok with a single open() here...
886 fd <- throwErrnoIfMinus1Retry "openFile"
887 (c_open f (fromIntegral oflags) 0o666)
891 h <- openFd fd (Just fd_type) False filepath mode binary
892 `catchException` \e -> do c_close fd; throw e
893 -- NB. don't forget to close the FD if openFd fails, otherwise
895 -- ASSERT: if we just created the file, then openFd won't fail
896 -- (so we don't need to worry about removing the newly created file
897 -- in the event of an error).
899 #ifndef mingw32_HOST_OS
900 -- we want to truncate() if this is an open in WriteMode, but only
901 -- if the target is a RegularFile. ftruncate() fails on special files
903 if mode == WriteMode && fd_type == RegularFile
904 then throwErrnoIf (/=0) "openFile"
911 -- | The function creates a temporary file in ReadWrite mode.
912 -- The created file isn\'t deleted automatically, so you need to delete it manually.
913 openTempFile :: FilePath -- ^ Directory in which to create the file
914 -> String -- ^ File name template. If the template is \"foo.ext\" then
915 -- the create file will be \"fooXXX.ext\" where XXX is some
917 -> IO (FilePath, Handle)
918 openTempFile tmp_dir template = openTempFile' "openTempFile" tmp_dir template dEFAULT_OPEN_IN_BINARY_MODE
920 -- | Like 'openTempFile', but opens the file in binary mode. See 'openBinaryFile' for more comments.
921 openBinaryTempFile :: FilePath -> String -> IO (FilePath, Handle)
922 openBinaryTempFile tmp_dir template = openTempFile' "openBinaryTempFile" tmp_dir template True
924 openTempFile' :: String -> FilePath -> String -> Bool -> IO (FilePath, Handle)
925 openTempFile' loc tmp_dir template binary = do
929 (prefix,suffix) = break (=='.') template
931 oflags1 = rw_flags .|. o_EXCL
937 oflags = oflags1 .|. binary_flags
940 fd <- withCString filepath $ \ f ->
941 c_open f oflags 0o666
946 then findTempName (x+1)
947 else ioError (errnoToIOError loc errno Nothing (Just tmp_dir))
949 h <- openFd fd Nothing False filepath ReadWriteMode True
950 `catchException` \e -> do c_close fd; throw e
953 filename = prefix ++ show x ++ suffix
954 filepath = tmp_dir `joinFileName` filename
957 std_flags = o_NONBLOCK .|. o_NOCTTY
958 output_flags = std_flags .|. o_CREAT
959 read_flags = std_flags .|. o_RDONLY
960 write_flags = output_flags .|. o_WRONLY
961 rw_flags = output_flags .|. o_RDWR
962 append_flags = write_flags .|. o_APPEND
964 -- ---------------------------------------------------------------------------
967 openFd :: FD -> Maybe FDType -> Bool -> FilePath -> IOMode -> Bool -> IO Handle
968 openFd fd mb_fd_type is_socket filepath mode binary = do
969 -- turn on non-blocking mode
972 #ifdef mingw32_HOST_OS
973 -- On Windows, the is_stream flag indicates that the Handle is a socket
974 let is_stream = is_socket
976 -- On Unix, the is_stream flag indicates that the FD is non-blocking
980 let (ha_type, write) =
982 ReadMode -> ( ReadHandle, False )
983 WriteMode -> ( WriteHandle, True )
984 ReadWriteMode -> ( ReadWriteHandle, True )
985 AppendMode -> ( AppendHandle, True )
987 -- open() won't tell us if it was a directory if we only opened for
988 -- reading, so check again.
996 ioException (IOError Nothing InappropriateType "openFile"
997 "is a directory" Nothing)
999 -- regular files need to be locked
1001 #ifndef mingw32_HOST_OS
1002 r <- lockFile fd (fromBool write) 1{-exclusive-}
1004 ioException (IOError Nothing ResourceBusy "openFile"
1005 "file is locked" Nothing)
1007 mkFileHandle fd is_stream filepath ha_type binary
1010 -- only *Streams* can be DuplexHandles. Other read/write
1011 -- Handles must share a buffer.
1012 | ReadWriteHandle <- ha_type ->
1013 mkDuplexHandle fd is_stream filepath binary
1015 mkFileHandle fd is_stream filepath ha_type binary
1018 mkFileHandle fd is_stream filepath ha_type binary
1020 fdToHandle :: FD -> IO Handle
1022 mode <- fdGetMode fd
1023 let fd_str = "<file descriptor: " ++ show fd ++ ">"
1024 openFd fd Nothing False{-XXX!-} fd_str mode True{-bin mode-}
1027 #ifndef mingw32_HOST_OS
1028 foreign import ccall unsafe "lockFile"
1029 lockFile :: CInt -> CInt -> CInt -> IO CInt
1031 foreign import ccall unsafe "unlockFile"
1032 unlockFile :: CInt -> IO CInt
1035 mkStdHandle :: FD -> FilePath -> HandleType -> IORef Buffer -> BufferMode
1037 mkStdHandle fd filepath ha_type buf bmode = do
1038 spares <- newIORef BufferListNil
1039 newFileHandle filepath (stdHandleFinalizer filepath)
1040 (Handle__ { haFD = fd,
1042 haIsBin = dEFAULT_OPEN_IN_BINARY_MODE,
1043 haIsStream = False, -- means FD is blocking on Unix
1044 haBufferMode = bmode,
1047 haOtherSide = Nothing
1050 mkFileHandle :: FD -> Bool -> FilePath -> HandleType -> Bool -> IO Handle
1051 mkFileHandle fd is_stream filepath ha_type binary = do
1052 (buf, bmode) <- getBuffer fd (initBufferState ha_type)
1054 #ifdef mingw32_HOST_OS
1055 -- On Windows, if this is a read/write handle and we are in text mode,
1056 -- turn off buffering. We don't correctly handle the case of switching
1057 -- from read mode to write mode on a buffered text-mode handle, see bug
1059 bmode <- case ha_type of
1060 ReadWriteHandle | not binary -> return NoBuffering
1061 _other -> return bmode
1064 spares <- newIORef BufferListNil
1065 newFileHandle filepath (handleFinalizer filepath)
1066 (Handle__ { haFD = fd,
1069 haIsStream = is_stream,
1070 haBufferMode = bmode,
1073 haOtherSide = Nothing
1076 mkDuplexHandle :: FD -> Bool -> FilePath -> Bool -> IO Handle
1077 mkDuplexHandle fd is_stream filepath binary = do
1078 (w_buf, w_bmode) <- getBuffer fd WriteBuffer
1079 w_spares <- newIORef BufferListNil
1081 Handle__ { haFD = fd,
1082 haType = WriteHandle,
1084 haIsStream = is_stream,
1085 haBufferMode = w_bmode,
1087 haBuffers = w_spares,
1088 haOtherSide = Nothing
1090 write_side <- newMVar w_handle_
1092 (r_buf, r_bmode) <- getBuffer fd ReadBuffer
1093 r_spares <- newIORef BufferListNil
1095 Handle__ { haFD = fd,
1096 haType = ReadHandle,
1098 haIsStream = is_stream,
1099 haBufferMode = r_bmode,
1101 haBuffers = r_spares,
1102 haOtherSide = Just write_side
1104 read_side <- newMVar r_handle_
1106 addMVarFinalizer write_side (handleFinalizer filepath write_side)
1107 return (DuplexHandle filepath read_side write_side)
1110 initBufferState ReadHandle = ReadBuffer
1111 initBufferState _ = WriteBuffer
1113 -- ---------------------------------------------------------------------------
1116 -- | Computation 'hClose' @hdl@ makes handle @hdl@ closed. Before the
1117 -- computation finishes, if @hdl@ is writable its buffer is flushed as
1119 -- Performing 'hClose' on a handle that has already been closed has no effect;
1120 -- doing so not an error. All other operations on a closed handle will fail.
1121 -- If 'hClose' fails for any reason, any further operations (apart from
1122 -- 'hClose') on the handle will still fail as if @hdl@ had been successfully
1125 hClose :: Handle -> IO ()
1126 hClose h@(FileHandle _ m) = hClose' h m
1127 hClose h@(DuplexHandle _ r w) = hClose' h w >> hClose' h r
1129 hClose' h m = withHandle__' "hClose" h m $ hClose_help
1131 -- hClose_help is also called by lazyRead (in PrelIO) when EOF is read
1132 -- or an IO error occurs on a lazy stream. The semi-closed Handle is
1133 -- then closed immediately. We have to be careful with DuplexHandles
1134 -- though: we have to leave the closing to the finalizer in that case,
1135 -- because the write side may still be in use.
1136 hClose_help :: Handle__ -> IO Handle__
1137 hClose_help handle_ =
1138 case haType handle_ of
1139 ClosedHandle -> return handle_
1140 _ -> do flushWriteBufferOnly handle_ -- interruptible
1141 hClose_handle_ handle_
1143 hClose_handle_ handle_ = do
1144 let fd = haFD handle_
1146 -- close the file descriptor, but not when this is the read
1147 -- side of a duplex handle.
1148 case haOtherSide handle_ of
1150 throwErrnoIfMinus1Retry_ "hClose"
1151 #ifdef mingw32_HOST_OS
1152 (closeFd (haIsStream handle_) fd)
1158 -- free the spare buffers
1159 writeIORef (haBuffers handle_) BufferListNil
1161 #ifndef mingw32_HOST_OS
1166 -- we must set the fd to -1, because the finalizer is going
1167 -- to run eventually and try to close/unlock it.
1168 return (handle_{ haFD = -1,
1169 haType = ClosedHandle
1172 -----------------------------------------------------------------------------
1173 -- Detecting and changing the size of a file
1175 -- | For a handle @hdl@ which attached to a physical file,
1176 -- 'hFileSize' @hdl@ returns the size of that file in 8-bit bytes.
1178 hFileSize :: Handle -> IO Integer
1180 withHandle_ "hFileSize" handle $ \ handle_ -> do
1181 case haType handle_ of
1182 ClosedHandle -> ioe_closedHandle
1183 SemiClosedHandle -> ioe_closedHandle
1184 _ -> do flushWriteBufferOnly handle_
1185 r <- fdFileSize (haFD handle_)
1188 else ioException (IOError Nothing InappropriateType "hFileSize"
1189 "not a regular file" Nothing)
1192 -- | 'hSetFileSize' @hdl@ @size@ truncates the physical file with handle @hdl@ to @size@ bytes.
1194 hSetFileSize :: Handle -> Integer -> IO ()
1195 hSetFileSize handle size =
1196 withHandle_ "hSetFileSize" handle $ \ handle_ -> do
1197 case haType handle_ of
1198 ClosedHandle -> ioe_closedHandle
1199 SemiClosedHandle -> ioe_closedHandle
1200 _ -> do flushWriteBufferOnly handle_
1201 throwErrnoIf (/=0) "hSetFileSize"
1202 (c_ftruncate (haFD handle_) (fromIntegral size))
1205 -- ---------------------------------------------------------------------------
1206 -- Detecting the End of Input
1208 -- | For a readable handle @hdl@, 'hIsEOF' @hdl@ returns
1209 -- 'True' if no further input can be taken from @hdl@ or for a
1210 -- physical file, if the current I\/O position is equal to the length of
1211 -- the file. Otherwise, it returns 'False'.
1213 hIsEOF :: Handle -> IO Bool
1216 (do hLookAhead handle; return False)
1217 (\e -> if isEOFError e then return True else ioError e)
1219 -- | The computation 'isEOF' is identical to 'hIsEOF',
1220 -- except that it works only on 'stdin'.
1223 isEOF = hIsEOF stdin
1225 -- ---------------------------------------------------------------------------
1228 -- | Computation 'hLookAhead' returns the next character from the handle
1229 -- without removing it from the input buffer, blocking until a character
1232 -- This operation may fail with:
1234 -- * 'isEOFError' if the end of file has been reached.
1236 hLookAhead :: Handle -> IO Char
1237 hLookAhead handle = do
1238 wantReadableHandle "hLookAhead" handle $ \handle_ -> do
1239 let ref = haBuffer handle_
1241 is_line = haBufferMode handle_ == LineBuffering
1242 buf <- readIORef ref
1244 -- fill up the read buffer if necessary
1245 new_buf <- if bufferEmpty buf
1246 then fillReadBuffer fd True (haIsStream handle_) buf
1249 writeIORef ref new_buf
1251 (c,_) <- readCharFromBuffer (bufBuf buf) (bufRPtr buf)
1254 -- ---------------------------------------------------------------------------
1255 -- Buffering Operations
1257 -- Three kinds of buffering are supported: line-buffering,
1258 -- block-buffering or no-buffering. See GHC.IOBase for definition and
1259 -- further explanation of what the type represent.
1261 -- | Computation 'hSetBuffering' @hdl mode@ sets the mode of buffering for
1262 -- handle @hdl@ on subsequent reads and writes.
1264 -- If the buffer mode is changed from 'BlockBuffering' or
1265 -- 'LineBuffering' to 'NoBuffering', then
1267 -- * if @hdl@ is writable, the buffer is flushed as for 'hFlush';
1269 -- * if @hdl@ is not writable, the contents of the buffer is discarded.
1271 -- This operation may fail with:
1273 -- * 'isPermissionError' if the handle has already been used for reading
1274 -- or writing and the implementation does not allow the buffering mode
1277 hSetBuffering :: Handle -> BufferMode -> IO ()
1278 hSetBuffering handle mode =
1279 withAllHandles__ "hSetBuffering" handle $ \ handle_ -> do
1280 case haType handle_ of
1281 ClosedHandle -> ioe_closedHandle
1284 - we flush the old buffer regardless of whether
1285 the new buffer could fit the contents of the old buffer
1287 - allow a handle's buffering to change even if IO has
1288 occurred (ANSI C spec. does not allow this, nor did
1289 the previous implementation of IO.hSetBuffering).
1290 - a non-standard extension is to allow the buffering
1291 of semi-closed handles to change [sof 6/98]
1295 let state = initBufferState (haType handle_)
1298 -- we always have a 1-character read buffer for
1299 -- unbuffered handles: it's needed to
1300 -- support hLookAhead.
1301 NoBuffering -> allocateBuffer 1 ReadBuffer
1302 LineBuffering -> allocateBuffer dEFAULT_BUFFER_SIZE state
1303 BlockBuffering Nothing -> allocateBuffer dEFAULT_BUFFER_SIZE state
1304 BlockBuffering (Just n) | n <= 0 -> ioe_bufsiz n
1305 | otherwise -> allocateBuffer n state
1306 writeIORef (haBuffer handle_) new_buf
1308 -- for input terminals we need to put the terminal into
1309 -- cooked or raw mode depending on the type of buffering.
1310 is_tty <- fdIsTTY (haFD handle_)
1311 when (is_tty && isReadableHandleType (haType handle_)) $
1313 #ifndef mingw32_HOST_OS
1314 -- 'raw' mode under win32 is a bit too specialised (and troublesome
1315 -- for most common uses), so simply disable its use here.
1316 NoBuffering -> setCooked (haFD handle_) False
1318 NoBuffering -> return ()
1320 _ -> setCooked (haFD handle_) True
1322 -- throw away spare buffers, they might be the wrong size
1323 writeIORef (haBuffers handle_) BufferListNil
1325 return (handle_{ haBufferMode = mode })
1327 -- -----------------------------------------------------------------------------
1330 -- | The action 'hFlush' @hdl@ causes any items buffered for output
1331 -- in handle @hdl@ to be sent immediately to the operating system.
1333 -- This operation may fail with:
1335 -- * 'isFullError' if the device is full;
1337 -- * 'isPermissionError' if a system resource limit would be exceeded.
1338 -- It is unspecified whether the characters in the buffer are discarded
1339 -- or retained under these circumstances.
1341 hFlush :: Handle -> IO ()
1343 wantWritableHandle "hFlush" handle $ \ handle_ -> do
1344 buf <- readIORef (haBuffer handle_)
1345 if bufferIsWritable buf && not (bufferEmpty buf)
1346 then do flushed_buf <- flushWriteBuffer (haFD handle_) (haIsStream handle_) buf
1347 writeIORef (haBuffer handle_) flushed_buf
1351 -- -----------------------------------------------------------------------------
1352 -- Repositioning Handles
1354 data HandlePosn = HandlePosn Handle HandlePosition
1356 instance Eq HandlePosn where
1357 (HandlePosn h1 p1) == (HandlePosn h2 p2) = p1==p2 && h1==h2
1359 instance Show HandlePosn where
1360 showsPrec p (HandlePosn h pos) =
1361 showsPrec p h . showString " at position " . shows pos
1363 -- HandlePosition is the Haskell equivalent of POSIX' off_t.
1364 -- We represent it as an Integer on the Haskell side, but
1365 -- cheat slightly in that hGetPosn calls upon a C helper
1366 -- that reports the position back via (merely) an Int.
1367 type HandlePosition = Integer
1369 -- | Computation 'hGetPosn' @hdl@ returns the current I\/O position of
1370 -- @hdl@ as a value of the abstract type 'HandlePosn'.
1372 hGetPosn :: Handle -> IO HandlePosn
1373 hGetPosn handle = do
1374 posn <- hTell handle
1375 return (HandlePosn handle posn)
1377 -- | If a call to 'hGetPosn' @hdl@ returns a position @p@,
1378 -- then computation 'hSetPosn' @p@ sets the position of @hdl@
1379 -- to the position it held at the time of the call to 'hGetPosn'.
1381 -- This operation may fail with:
1383 -- * 'isPermissionError' if a system resource limit would be exceeded.
1385 hSetPosn :: HandlePosn -> IO ()
1386 hSetPosn (HandlePosn h i) = hSeek h AbsoluteSeek i
1388 -- ---------------------------------------------------------------------------
1391 -- | A mode that determines the effect of 'hSeek' @hdl mode i@, as follows:
1393 = AbsoluteSeek -- ^ the position of @hdl@ is set to @i@.
1394 | RelativeSeek -- ^ the position of @hdl@ is set to offset @i@
1395 -- from the current position.
1396 | SeekFromEnd -- ^ the position of @hdl@ is set to offset @i@
1397 -- from the end of the file.
1398 deriving (Eq, Ord, Ix, Enum, Read, Show)
1401 - when seeking using `SeekFromEnd', positive offsets (>=0) means
1402 seeking at or past EOF.
1404 - we possibly deviate from the report on the issue of seeking within
1405 the buffer and whether to flush it or not. The report isn't exactly
1409 -- | Computation 'hSeek' @hdl mode i@ sets the position of handle
1410 -- @hdl@ depending on @mode@.
1411 -- The offset @i@ is given in terms of 8-bit bytes.
1413 -- If @hdl@ is block- or line-buffered, then seeking to a position which is not
1414 -- in the current buffer will first cause any items in the output buffer to be
1415 -- written to the device, and then cause the input buffer to be discarded.
1416 -- Some handles may not be seekable (see 'hIsSeekable'), or only support a
1417 -- subset of the possible positioning operations (for instance, it may only
1418 -- be possible to seek to the end of a tape, or to a positive offset from
1419 -- the beginning or current position).
1420 -- It is not possible to set a negative I\/O position, or for
1421 -- a physical file, an I\/O position beyond the current end-of-file.
1423 -- This operation may fail with:
1425 -- * 'isPermissionError' if a system resource limit would be exceeded.
1427 hSeek :: Handle -> SeekMode -> Integer -> IO ()
1428 hSeek handle mode offset =
1429 wantSeekableHandle "hSeek" handle $ \ handle_ -> do
1431 puts ("hSeek " ++ show (mode,offset) ++ "\n")
1433 let ref = haBuffer handle_
1434 buf <- readIORef ref
1440 throwErrnoIfMinus1Retry_ "hSeek"
1441 (c_lseek (haFD handle_) (fromIntegral offset) whence)
1444 whence = case mode of
1445 AbsoluteSeek -> sEEK_SET
1446 RelativeSeek -> sEEK_CUR
1447 SeekFromEnd -> sEEK_END
1449 if bufferIsWritable buf
1450 then do new_buf <- flushWriteBuffer fd (haIsStream handle_) buf
1451 writeIORef ref new_buf
1455 if mode == RelativeSeek && offset >= 0 && offset < fromIntegral (w - r)
1456 then writeIORef ref buf{ bufRPtr = r + fromIntegral offset }
1459 new_buf <- flushReadBuffer (haFD handle_) buf
1460 writeIORef ref new_buf
1464 hTell :: Handle -> IO Integer
1466 wantSeekableHandle "hGetPosn" handle $ \ handle_ -> do
1468 #if defined(mingw32_HOST_OS)
1469 -- urgh, on Windows we have to worry about \n -> \r\n translation,
1470 -- so we can't easily calculate the file position using the
1471 -- current buffer size. Just flush instead.
1474 let fd = haFD handle_
1475 posn <- fromIntegral `liftM`
1476 throwErrnoIfMinus1Retry "hGetPosn"
1477 (c_lseek fd 0 sEEK_CUR)
1479 let ref = haBuffer handle_
1480 buf <- readIORef ref
1483 | bufferIsWritable buf = posn + fromIntegral (bufWPtr buf)
1484 | otherwise = posn - fromIntegral (bufWPtr buf - bufRPtr buf)
1486 puts ("\nhGetPosn: (fd, posn, real_posn) = " ++ show (fd, posn, real_posn) ++ "\n")
1487 puts (" (bufWPtr, bufRPtr) = " ++ show (bufWPtr buf, bufRPtr buf) ++ "\n")
1491 -- -----------------------------------------------------------------------------
1492 -- Handle Properties
1494 -- A number of operations return information about the properties of a
1495 -- handle. Each of these operations returns `True' if the handle has
1496 -- the specified property, and `False' otherwise.
1498 hIsOpen :: Handle -> IO Bool
1500 withHandle_ "hIsOpen" handle $ \ handle_ -> do
1501 case haType handle_ of
1502 ClosedHandle -> return False
1503 SemiClosedHandle -> return False
1506 hIsClosed :: Handle -> IO Bool
1508 withHandle_ "hIsClosed" handle $ \ handle_ -> do
1509 case haType handle_ of
1510 ClosedHandle -> return True
1513 {- not defined, nor exported, but mentioned
1514 here for documentation purposes:
1516 hSemiClosed :: Handle -> IO Bool
1520 return (not (ho || hc))
1523 hIsReadable :: Handle -> IO Bool
1524 hIsReadable (DuplexHandle _ _ _) = return True
1525 hIsReadable handle =
1526 withHandle_ "hIsReadable" handle $ \ handle_ -> do
1527 case haType handle_ of
1528 ClosedHandle -> ioe_closedHandle
1529 SemiClosedHandle -> ioe_closedHandle
1530 htype -> return (isReadableHandleType htype)
1532 hIsWritable :: Handle -> IO Bool
1533 hIsWritable (DuplexHandle _ _ _) = return True
1534 hIsWritable handle =
1535 withHandle_ "hIsWritable" handle $ \ handle_ -> do
1536 case haType handle_ of
1537 ClosedHandle -> ioe_closedHandle
1538 SemiClosedHandle -> ioe_closedHandle
1539 htype -> return (isWritableHandleType htype)
1541 -- | Computation 'hGetBuffering' @hdl@ returns the current buffering mode
1544 hGetBuffering :: Handle -> IO BufferMode
1545 hGetBuffering handle =
1546 withHandle_ "hGetBuffering" handle $ \ handle_ -> do
1547 case haType handle_ of
1548 ClosedHandle -> ioe_closedHandle
1550 -- We're being non-standard here, and allow the buffering
1551 -- of a semi-closed handle to be queried. -- sof 6/98
1552 return (haBufferMode handle_) -- could be stricter..
1554 hIsSeekable :: Handle -> IO Bool
1555 hIsSeekable handle =
1556 withHandle_ "hIsSeekable" handle $ \ handle_ -> do
1557 case haType handle_ of
1558 ClosedHandle -> ioe_closedHandle
1559 SemiClosedHandle -> ioe_closedHandle
1560 AppendHandle -> return False
1561 _ -> do t <- fdType (haFD handle_)
1562 return ((t == RegularFile || t == RawDevice)
1563 && (haIsBin handle_ || tEXT_MODE_SEEK_ALLOWED))
1565 -- -----------------------------------------------------------------------------
1566 -- Changing echo status (Non-standard GHC extensions)
1568 -- | Set the echoing status of a handle connected to a terminal.
1570 hSetEcho :: Handle -> Bool -> IO ()
1571 hSetEcho handle on = do
1572 isT <- hIsTerminalDevice handle
1576 withHandle_ "hSetEcho" handle $ \ handle_ -> do
1577 case haType handle_ of
1578 ClosedHandle -> ioe_closedHandle
1579 _ -> setEcho (haFD handle_) on
1581 -- | Get the echoing status of a handle connected to a terminal.
1583 hGetEcho :: Handle -> IO Bool
1584 hGetEcho handle = do
1585 isT <- hIsTerminalDevice handle
1589 withHandle_ "hGetEcho" handle $ \ handle_ -> do
1590 case haType handle_ of
1591 ClosedHandle -> ioe_closedHandle
1592 _ -> getEcho (haFD handle_)
1594 -- | Is the handle connected to a terminal?
1596 hIsTerminalDevice :: Handle -> IO Bool
1597 hIsTerminalDevice handle = do
1598 withHandle_ "hIsTerminalDevice" handle $ \ handle_ -> do
1599 case haType handle_ of
1600 ClosedHandle -> ioe_closedHandle
1601 _ -> fdIsTTY (haFD handle_)
1603 -- -----------------------------------------------------------------------------
1606 -- | Select binary mode ('True') or text mode ('False') on a open handle.
1607 -- (See also 'openBinaryFile'.)
1609 hSetBinaryMode :: Handle -> Bool -> IO ()
1610 hSetBinaryMode handle bin =
1611 withAllHandles__ "hSetBinaryMode" handle $ \ handle_ ->
1612 do throwErrnoIfMinus1_ "hSetBinaryMode"
1613 (setmode (haFD handle_) bin)
1614 return handle_{haIsBin=bin}
1616 foreign import ccall unsafe "__hscore_setmode"
1617 setmode :: CInt -> Bool -> IO CInt
1619 -- -----------------------------------------------------------------------------
1620 -- Duplicating a Handle
1622 -- | Returns a duplicate of the original handle, with its own buffer.
1623 -- The two Handles will share a file pointer, however. The original
1624 -- handle's buffer is flushed, including discarding any input data,
1625 -- before the handle is duplicated.
1627 hDuplicate :: Handle -> IO Handle
1628 hDuplicate h@(FileHandle path m) = do
1629 new_h_ <- withHandle' "hDuplicate" h m (dupHandle h Nothing)
1630 newFileHandle path (handleFinalizer path) new_h_
1631 hDuplicate h@(DuplexHandle path r w) = do
1632 new_w_ <- withHandle' "hDuplicate" h w (dupHandle h Nothing)
1633 new_w <- newMVar new_w_
1634 new_r_ <- withHandle' "hDuplicate" h r (dupHandle h (Just new_w))
1635 new_r <- newMVar new_r_
1636 addMVarFinalizer new_w (handleFinalizer path new_w)
1637 return (DuplexHandle path new_r new_w)
1639 dupHandle :: Handle -> Maybe (MVar Handle__) -> Handle__
1640 -> IO (Handle__, Handle__)
1641 dupHandle h other_side h_ = do
1642 -- flush the buffer first, so we don't have to copy its contents
1644 new_fd <- case other_side of
1645 Nothing -> throwErrnoIfMinus1 "dupHandle" $ c_dup (haFD h_)
1646 Just r -> withHandle_' "dupHandle" h r (return . haFD)
1647 dupHandle_ other_side h_ new_fd
1649 dupHandleTo other_side hto_ h_ = do
1651 -- Windows' dup2 does not return the new descriptor, unlike Unix
1652 throwErrnoIfMinus1 "dupHandleTo" $
1653 c_dup2 (haFD h_) (haFD hto_)
1654 dupHandle_ other_side h_ (haFD hto_)
1656 dupHandle_ :: Maybe (MVar Handle__) -> Handle__ -> FD
1657 -> IO (Handle__, Handle__)
1658 dupHandle_ other_side h_ new_fd = do
1659 buffer <- allocateBuffer dEFAULT_BUFFER_SIZE (initBufferState (haType h_))
1660 ioref <- newIORef buffer
1661 ioref_buffers <- newIORef BufferListNil
1663 let new_handle_ = h_{ haFD = new_fd,
1665 haBuffers = ioref_buffers,
1666 haOtherSide = other_side }
1667 return (h_, new_handle_)
1669 -- -----------------------------------------------------------------------------
1670 -- Replacing a Handle
1673 Makes the second handle a duplicate of the first handle. The second
1674 handle will be closed first, if it is not already.
1676 This can be used to retarget the standard Handles, for example:
1678 > do h <- openFile "mystdout" WriteMode
1679 > hDuplicateTo h stdout
1682 hDuplicateTo :: Handle -> Handle -> IO ()
1683 hDuplicateTo h1@(FileHandle _ m1) h2@(FileHandle _ m2) = do
1684 withHandle__' "hDuplicateTo" h2 m2 $ \h2_ -> do
1685 _ <- hClose_help h2_
1686 withHandle' "hDuplicateTo" h1 m1 (dupHandleTo Nothing h2_)
1687 hDuplicateTo h1@(DuplexHandle _ r1 w1) h2@(DuplexHandle _ r2 w2) = do
1688 withHandle__' "hDuplicateTo" h2 w2 $ \w2_ -> do
1689 _ <- hClose_help w2_
1690 withHandle' "hDuplicateTo" h1 r1 (dupHandleTo Nothing w2_)
1691 withHandle__' "hDuplicateTo" h2 r2 $ \r2_ -> do
1692 _ <- hClose_help r2_
1693 withHandle' "hDuplicateTo" h1 r1 (dupHandleTo (Just w1) r2_)
1695 ioException (IOError (Just h1) IllegalOperation "hDuplicateTo"
1696 "handles are incompatible" Nothing)
1698 -- ---------------------------------------------------------------------------
1701 -- | 'hShow' is in the 'IO' monad, and gives more comprehensive output
1702 -- than the (pure) instance of 'Show' for 'Handle'.
1704 hShow :: Handle -> IO String
1705 hShow h@(FileHandle path _) = showHandle' path False h
1706 hShow h@(DuplexHandle path _ _) = showHandle' path True h
1708 showHandle' filepath is_duplex h =
1709 withHandle_ "showHandle" h $ \hdl_ ->
1711 showType | is_duplex = showString "duplex (read-write)"
1712 | otherwise = shows (haType hdl_)
1716 showHdl (haType hdl_)
1717 (showString "loc=" . showString filepath . showChar ',' .
1718 showString "type=" . showType . showChar ',' .
1719 showString "binary=" . shows (haIsBin hdl_) . showChar ',' .
1720 showString "buffering=" . showBufMode (unsafePerformIO (readIORef (haBuffer hdl_))) (haBufferMode hdl_) . showString "}" )
1724 showHdl :: HandleType -> ShowS -> ShowS
1727 ClosedHandle -> shows ht . showString "}"
1730 showBufMode :: Buffer -> BufferMode -> ShowS
1731 showBufMode buf bmo =
1733 NoBuffering -> showString "none"
1734 LineBuffering -> showString "line"
1735 BlockBuffering (Just n) -> showString "block " . showParen True (shows n)
1736 BlockBuffering Nothing -> showString "block " . showParen True (shows def)
1741 -- ---------------------------------------------------------------------------
1744 #if defined(DEBUG_DUMP)
1745 puts :: String -> IO ()
1746 puts s = do write_rawBuffer 1 (unsafeCoerce# (packCString# s)) 0 (fromIntegral (length s))
1750 -- -----------------------------------------------------------------------------
1753 throwErrnoIfMinus1RetryOnBlock :: String -> IO CInt -> IO CInt -> IO CInt
1754 throwErrnoIfMinus1RetryOnBlock loc f on_block =
1757 if (res :: CInt) == -1
1761 then throwErrnoIfMinus1RetryOnBlock loc f on_block
1762 else if err == eWOULDBLOCK || err == eAGAIN
1767 -- -----------------------------------------------------------------------------
1768 -- wrappers to platform-specific constants:
1770 foreign import ccall unsafe "__hscore_supportsTextMode"
1771 tEXT_MODE_SEEK_ALLOWED :: Bool
1773 foreign import ccall unsafe "__hscore_bufsiz" dEFAULT_BUFFER_SIZE :: Int
1774 foreign import ccall unsafe "__hscore_seek_cur" sEEK_CUR :: CInt
1775 foreign import ccall unsafe "__hscore_seek_set" sEEK_SET :: CInt
1776 foreign import ccall unsafe "__hscore_seek_end" sEEK_END :: CInt