Move file locking into the RTS, fixing #629, #1109
[packages/base.git] / GHC / Handle.hs
1 {-# OPTIONS_GHC -fno-implicit-prelude -#include "HsBase.h" #-}
2
3 #undef DEBUG_DUMP
4 #undef DEBUG
5
6 -----------------------------------------------------------------------------
7 -- |
8 -- Module : GHC.Handle
9 -- Copyright : (c) The University of Glasgow, 1994-2001
10 -- License : see libraries/base/LICENSE
11 --
12 -- Maintainer : libraries@haskell.org
13 -- Stability : internal
14 -- Portability : non-portable
15 --
16 -- This module defines the basic operations on I\/O \"handles\".
17 --
18 -----------------------------------------------------------------------------
19
20 -- #hide
21 module GHC.Handle (
22 withHandle, withHandle', withHandle_,
23 wantWritableHandle, wantReadableHandle, wantSeekableHandle,
24
25 newEmptyBuffer, allocateBuffer, readCharFromBuffer, writeCharIntoBuffer,
26 flushWriteBufferOnly, flushWriteBuffer, flushReadBuffer,
27 fillReadBuffer, fillReadBufferWithoutBlocking,
28 readRawBuffer, readRawBufferPtr,
29 writeRawBuffer, writeRawBufferPtr,
30
31 #ifndef mingw32_HOST_OS
32 unlockFile,
33 #endif
34
35 ioe_closedHandle, ioe_EOF, ioe_notReadable, ioe_notWritable,
36
37 stdin, stdout, stderr,
38 IOMode(..), openFile, openBinaryFile, fdToHandle', fdToHandle,
39 hFileSize, hSetFileSize, hIsEOF, isEOF, hLookAhead, hSetBuffering, hSetBinaryMode,
40 hFlush, hDuplicate, hDuplicateTo,
41
42 hClose, hClose_help,
43
44 HandlePosition, HandlePosn(..), hGetPosn, hSetPosn,
45 SeekMode(..), hSeek, hTell,
46
47 hIsOpen, hIsClosed, hIsReadable, hIsWritable, hGetBuffering, hIsSeekable,
48 hSetEcho, hGetEcho, hIsTerminalDevice,
49
50 hShow,
51
52 #ifdef DEBUG_DUMP
53 puts,
54 #endif
55
56 ) where
57
58 import Control.Monad
59 import Data.Bits
60 import Data.Maybe
61 import Foreign
62 import Foreign.C
63 import System.IO.Error
64 import System.Posix.Internals
65 import System.Posix.Types
66
67 import GHC.Real
68
69 import GHC.Arr
70 import GHC.Base
71 import GHC.Read ( Read )
72 import GHC.List
73 import GHC.IOBase
74 import GHC.Exception
75 import GHC.Enum
76 import GHC.Num ( Integer(..), Num(..) )
77 import GHC.Show
78 import GHC.Real ( toInteger )
79 #if defined(DEBUG_DUMP)
80 import GHC.Pack
81 #endif
82
83 import GHC.Conc
84
85 -- -----------------------------------------------------------------------------
86 -- TODO:
87
88 -- hWaitForInput blocks (should use a timeout)
89
90 -- unbuffered hGetLine is a bit dodgy
91
92 -- hSetBuffering: can't change buffering on a stream,
93 -- when the read buffer is non-empty? (no way to flush the buffer)
94
95 -- ---------------------------------------------------------------------------
96 -- Are files opened by default in text or binary mode, if the user doesn't
97 -- specify?
98
99 dEFAULT_OPEN_IN_BINARY_MODE = False :: Bool
100
101 -- ---------------------------------------------------------------------------
102 -- Creating a new handle
103
104 newFileHandle :: FilePath -> (MVar Handle__ -> IO ()) -> Handle__ -> IO Handle
105 newFileHandle filepath finalizer hc = do
106 m <- newMVar hc
107 addMVarFinalizer m (finalizer m)
108 return (FileHandle filepath m)
109
110 -- ---------------------------------------------------------------------------
111 -- Working with Handles
112
113 {-
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.
117
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.
123
124 There are three versions of @withHandle@: corresponding to the three
125 possible combinations of:
126
127 - the operation may side-effect the handle
128 - the operation may return a result
129
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 ].
133 -}
134
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
139
140 withHandle' :: String -> Handle -> MVar Handle__
141 -> (Handle__ -> IO (Handle__,a)) -> IO a
142 withHandle' fun h m act =
143 block $ do
144 h_ <- takeMVar m
145 checkBufferInvariants h_
146 (h',v) <- catchException (act h_)
147 (\ err -> putMVar m h_ >>
148 case err of
149 IOException ex -> ioError (augmentIOError ex fun h)
150 _ -> throw err)
151 checkBufferInvariants h'
152 putMVar m h'
153 return v
154
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
159
160 withHandle_' :: String -> Handle -> MVar Handle__ -> (Handle__ -> IO a) -> IO a
161 withHandle_' fun h m act =
162 block $ do
163 h_ <- takeMVar m
164 checkBufferInvariants h_
165 v <- catchException (act h_)
166 (\ err -> putMVar m h_ >>
167 case err of
168 IOException ex -> ioError (augmentIOError ex fun h)
169 _ -> throw err)
170 checkBufferInvariants h_
171 putMVar m h_
172 return v
173
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
179
180 withHandle__' fun h m act =
181 block $ do
182 h_ <- takeMVar m
183 checkBufferInvariants h_
184 h' <- catchException (act h_)
185 (\ err -> putMVar m h_ >>
186 case err of
187 IOException ex -> ioError (augmentIOError ex fun h)
188 _ -> throw err)
189 checkBufferInvariants h'
190 putMVar m h'
191 return ()
192
193 augmentIOError (IOError _ iot _ str fp) fun h
194 = IOError (Just h) iot fun str filepath
195 where filepath
196 | Just _ <- fp = fp
197 | otherwise = case h of
198 FileHandle fp _ -> Just fp
199 DuplexHandle fp _ _ -> Just fp
200
201 -- ---------------------------------------------------------------------------
202 -- Wrapper for write operations.
203
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
210
211 wantWritableHandle'
212 :: String -> Handle -> MVar Handle__
213 -> (Handle__ -> IO a) -> IO a
214 wantWritableHandle' fun h m act
215 = withHandle_' fun h m (checkWritableHandle act)
216
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_
224 buf <- readIORef ref
225 new_buf <-
226 if not (bufferIsWritable buf)
227 then do b <- flushReadBuffer (haFD handle_) buf
228 return b{ bufState=WriteBuffer }
229 else return buf
230 writeIORef ref new_buf
231 act handle_
232 _other -> act handle_
233
234 -- ---------------------------------------------------------------------------
235 -- Wrapper for read operations.
236
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
243
244 wantReadableHandle'
245 :: String -> Handle -> MVar Handle__
246 -> (Handle__ -> IO a) -> IO a
247 wantReadableHandle' fun h m act
248 = withHandle_' fun h m (checkReadableHandle act)
249
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_
258 buf <- readIORef ref
259 when (bufferIsWritable buf) $ do
260 new_buf <- flushWriteBuffer (haFD handle_) (haIsStream handle_) buf
261 writeIORef ref new_buf{ bufState=ReadBuffer }
262 act handle_
263 _other -> act handle_
264
265 -- ---------------------------------------------------------------------------
266 -- Wrapper for seek operations.
267
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)
274
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
282
283 -- -----------------------------------------------------------------------------
284 -- Handy IOErrors
285
286 ioe_closedHandle, ioe_EOF,
287 ioe_notReadable, ioe_notWritable,
288 ioe_notSeekable, ioe_notSeekable_notBin :: IO a
289
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"
307 Nothing)
308
309 ioe_finalizedHandle fp = throw (IOException
310 (IOError Nothing IllegalOperation ""
311 "handle is finalized" (Just fp)))
312
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.
318
319 -- -----------------------------------------------------------------------------
320 -- Handle Finalizers
321
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.
327
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.
334
335 stdHandleFinalizer :: FilePath -> MVar Handle__ -> IO ()
336 stdHandleFinalizer fp m = do
337 h_ <- takeMVar m
338 flushWriteBufferOnly h_
339 putMVar m (ioe_finalizedHandle fp)
340
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_
350 return ()
351 putMVar m (ioe_finalizedHandle fp)
352
353 -- ---------------------------------------------------------------------------
354 -- Grimy buffer operations
355
356 #ifdef DEBUG
357 checkBufferInvariants h_ = do
358 let ref = haBuffer h_
359 Buffer{ bufWPtr=w, bufRPtr=r, bufSize=size, bufState=state } <- readIORef ref
360 if not (
361 size > 0
362 && r <= w
363 && w <= size
364 && ( r /= w || (r == 0 && w == 0) )
365 && ( state /= WriteBuffer || r == 0 )
366 && ( state /= WriteBuffer || w < size ) -- write buffer is never full
367 )
368 then error "buffer invariant violation"
369 else return ()
370 #else
371 checkBufferInvariants h_ = return ()
372 #endif
373
374 newEmptyBuffer :: RawBuffer -> BufferState -> Int -> Buffer
375 newEmptyBuffer b state size
376 = Buffer{ bufBuf=b, bufRPtr=0, bufWPtr=0, bufSize=size, bufState=state }
377
378 allocateBuffer :: Int -> BufferState -> IO Buffer
379 allocateBuffer sz@(I# size) state = IO $ \s ->
380 -- We sometimes need to pass the address of this buffer to
381 -- a "safe" foreign call, hence it must be immovable.
382 case newPinnedByteArray# size s of { (# s, b #) ->
383 (# s, newEmptyBuffer b state sz #) }
384
385 writeCharIntoBuffer :: RawBuffer -> Int -> Char -> IO Int
386 writeCharIntoBuffer slab (I# off) (C# c)
387 = IO $ \s -> case writeCharArray# slab off c s of
388 s -> (# s, I# (off +# 1#) #)
389
390 readCharFromBuffer :: RawBuffer -> Int -> IO (Char, Int)
391 readCharFromBuffer slab (I# off)
392 = IO $ \s -> case readCharArray# slab off s of
393 (# s, c #) -> (# s, (C# c, I# (off +# 1#)) #)
394
395 getBuffer :: FD -> BufferState -> IO (IORef Buffer, BufferMode)
396 getBuffer fd state = do
397 buffer <- allocateBuffer dEFAULT_BUFFER_SIZE state
398 ioref <- newIORef buffer
399 is_tty <- fdIsTTY fd
400
401 let buffer_mode
402 | is_tty = LineBuffering
403 | otherwise = BlockBuffering Nothing
404
405 return (ioref, buffer_mode)
406
407 mkUnBuffer :: IO (IORef Buffer)
408 mkUnBuffer = do
409 buffer <- allocateBuffer 1 ReadBuffer
410 newIORef buffer
411
412 -- flushWriteBufferOnly flushes the buffer iff it contains pending write data.
413 flushWriteBufferOnly :: Handle__ -> IO ()
414 flushWriteBufferOnly h_ = do
415 let fd = haFD h_
416 ref = haBuffer h_
417 buf <- readIORef ref
418 new_buf <- if bufferIsWritable buf
419 then flushWriteBuffer fd (haIsStream h_) buf
420 else return buf
421 writeIORef ref new_buf
422
423 -- flushBuffer syncs the file with the buffer, including moving the
424 -- file pointer backwards in the case of a read buffer.
425 flushBuffer :: Handle__ -> IO ()
426 flushBuffer h_ = do
427 let ref = haBuffer h_
428 buf <- readIORef ref
429
430 flushed_buf <-
431 case bufState buf of
432 ReadBuffer -> flushReadBuffer (haFD h_) buf
433 WriteBuffer -> flushWriteBuffer (haFD h_) (haIsStream h_) buf
434
435 writeIORef ref flushed_buf
436
437 -- When flushing a read buffer, we seek backwards by the number of
438 -- characters in the buffer. The file descriptor must therefore be
439 -- seekable: attempting to flush the read buffer on an unseekable
440 -- handle is not allowed.
441
442 flushReadBuffer :: FD -> Buffer -> IO Buffer
443 flushReadBuffer fd buf
444 | bufferEmpty buf = return buf
445 | otherwise = do
446 let off = negate (bufWPtr buf - bufRPtr buf)
447 # ifdef DEBUG_DUMP
448 puts ("flushReadBuffer: new file offset = " ++ show off ++ "\n")
449 # endif
450 throwErrnoIfMinus1Retry "flushReadBuffer"
451 (c_lseek fd (fromIntegral off) sEEK_CUR)
452 return buf{ bufWPtr=0, bufRPtr=0 }
453
454 flushWriteBuffer :: FD -> Bool -> Buffer -> IO Buffer
455 flushWriteBuffer fd is_stream buf@Buffer{ bufBuf=b, bufRPtr=r, bufWPtr=w } =
456 seq fd $ do -- strictness hack
457 let bytes = w - r
458 #ifdef DEBUG_DUMP
459 puts ("flushWriteBuffer, fd=" ++ show fd ++ ", bytes=" ++ show bytes ++ "\n")
460 #endif
461 if bytes == 0
462 then return (buf{ bufRPtr=0, bufWPtr=0 })
463 else do
464 res <- writeRawBuffer "flushWriteBuffer" fd is_stream b
465 (fromIntegral r) (fromIntegral bytes)
466 let res' = fromIntegral res
467 if res' < bytes
468 then flushWriteBuffer fd is_stream (buf{ bufRPtr = r + res' })
469 else return buf{ bufRPtr=0, bufWPtr=0 }
470
471 fillReadBuffer :: FD -> Bool -> Bool -> Buffer -> IO Buffer
472 fillReadBuffer fd is_line is_stream
473 buf@Buffer{ bufBuf=b, bufRPtr=r, bufWPtr=w, bufSize=size } =
474 -- buffer better be empty:
475 assert (r == 0 && w == 0) $ do
476 fillReadBufferLoop fd is_line is_stream buf b w size
477
478 -- For a line buffer, we just get the first chunk of data to arrive,
479 -- and don't wait for the whole buffer to be full (but we *do* wait
480 -- until some data arrives). This isn't really line buffering, but it
481 -- appears to be what GHC has done for a long time, and I suspect it
482 -- is more useful than line buffering in most cases.
483
484 fillReadBufferLoop fd is_line is_stream buf b w size = do
485 let bytes = size - w
486 if bytes == 0 -- buffer full?
487 then return buf{ bufRPtr=0, bufWPtr=w }
488 else do
489 #ifdef DEBUG_DUMP
490 puts ("fillReadBufferLoop: bytes = " ++ show bytes ++ "\n")
491 #endif
492 res <- readRawBuffer "fillReadBuffer" fd is_stream b
493 (fromIntegral w) (fromIntegral bytes)
494 let res' = fromIntegral res
495 #ifdef DEBUG_DUMP
496 puts ("fillReadBufferLoop: res' = " ++ show res' ++ "\n")
497 #endif
498 if res' == 0
499 then if w == 0
500 then ioe_EOF
501 else return buf{ bufRPtr=0, bufWPtr=w }
502 else if res' < bytes && not is_line
503 then fillReadBufferLoop fd is_line is_stream buf b (w+res') size
504 else return buf{ bufRPtr=0, bufWPtr=w+res' }
505
506
507 fillReadBufferWithoutBlocking :: FD -> Bool -> Buffer -> IO Buffer
508 fillReadBufferWithoutBlocking fd is_stream
509 buf@Buffer{ bufBuf=b, bufRPtr=r, bufWPtr=w, bufSize=size } =
510 -- buffer better be empty:
511 assert (r == 0 && w == 0) $ do
512 #ifdef DEBUG_DUMP
513 puts ("fillReadBufferLoopNoBlock: bytes = " ++ show size ++ "\n")
514 #endif
515 res <- readRawBufferNoBlock "fillReadBuffer" fd is_stream b
516 0 (fromIntegral size)
517 let res' = fromIntegral res
518 #ifdef DEBUG_DUMP
519 puts ("fillReadBufferLoopNoBlock: res' = " ++ show res' ++ "\n")
520 #endif
521 return buf{ bufRPtr=0, bufWPtr=res' }
522
523 -- Low level routines for reading/writing to (raw)buffers:
524
525 #ifndef mingw32_HOST_OS
526
527 {-
528 NOTE [nonblock]:
529
530 Unix has broken semantics when it comes to non-blocking I/O: you can
531 set the O_NONBLOCK flag on an FD, but it applies to the all other FDs
532 attached to the same underlying file, pipe or TTY; there's no way to
533 have private non-blocking behaviour for an FD. See bug #724.
534
535 We fix this by only setting O_NONBLOCK on FDs that we create; FDs that
536 come from external sources or are exposed externally are left in
537 blocking mode. This solution has some problems though. We can't
538 completely simulate a non-blocking read without O_NONBLOCK: several
539 cases are wrong here. The cases that are wrong:
540
541 * reading/writing to a blocking FD in non-threaded mode.
542 In threaded mode, we just make a safe call to read().
543 In non-threaded mode we call select() before attempting to read,
544 but that leaves a small race window where the data can be read
545 from the file descriptor before we issue our blocking read().
546 * readRawBufferNoBlock for a blocking FD
547 -}
548
549 readRawBuffer :: String -> FD -> Bool -> RawBuffer -> Int -> CInt -> IO CInt
550 readRawBuffer loc fd is_nonblock buf off len
551 | is_nonblock = unsafe_read
552 | threaded = safe_read
553 | otherwise = do r <- throwErrnoIfMinus1 loc
554 (fdReady (fromIntegral fd) 0 0 False)
555 if r /= 0
556 then unsafe_read
557 else do threadWaitRead (fromIntegral fd); unsafe_read
558 where
559 do_read call = throwErrnoIfMinus1RetryMayBlock loc call
560 (threadWaitRead (fromIntegral fd))
561 unsafe_read = do_read (read_rawBuffer fd buf off len)
562 safe_read = do_read (safe_read_rawBuffer fd buf off len)
563
564 readRawBufferPtr :: String -> FD -> Bool -> Ptr CChar -> Int -> CInt -> IO CInt
565 readRawBufferPtr loc fd is_nonblock buf off len
566 | is_nonblock = unsafe_read
567 | threaded = safe_read
568 | otherwise = do r <- throwErrnoIfMinus1 loc
569 (fdReady (fromIntegral fd) 0 0 False)
570 if r /= 0
571 then unsafe_read
572 else do threadWaitRead (fromIntegral fd); unsafe_read
573 where
574 do_read call = throwErrnoIfMinus1RetryMayBlock loc call
575 (threadWaitRead (fromIntegral fd))
576 unsafe_read = do_read (read_off fd buf off len)
577 safe_read = do_read (safe_read_off fd buf off len)
578
579 readRawBufferNoBlock :: String -> FD -> Bool -> RawBuffer -> Int -> CInt -> IO CInt
580 readRawBufferNoBlock loc fd is_nonblock buf off len
581 | is_nonblock = unsafe_read
582 | otherwise = do r <- fdReady (fromIntegral fd) 0 0 False
583 if r /= 0 then safe_read
584 else return 0
585 -- XXX see note [nonblock]
586 where
587 do_read call = throwErrnoIfMinus1RetryOnBlock loc call (return 0)
588 unsafe_read = do_read (read_rawBuffer fd buf off len)
589 safe_read = do_read (safe_read_rawBuffer fd buf off len)
590
591 writeRawBuffer :: String -> FD -> Bool -> RawBuffer -> Int -> CInt -> IO CInt
592 writeRawBuffer loc fd is_nonblock buf off len
593 | is_nonblock = unsafe_write
594 | threaded = safe_write
595 | otherwise = do r <- fdReady (fromIntegral fd) 1 0 False
596 if r /= 0
597 then safe_write
598 else do threadWaitWrite (fromIntegral fd); unsafe_write
599 where
600 do_write call = throwErrnoIfMinus1RetryMayBlock loc call
601 (threadWaitWrite (fromIntegral fd))
602 unsafe_write = do_write (write_rawBuffer fd buf off len)
603 safe_write = do_write (safe_write_rawBuffer (fromIntegral fd) buf off len)
604
605 writeRawBufferPtr :: String -> FD -> Bool -> Ptr CChar -> Int -> CInt -> IO CInt
606 writeRawBufferPtr loc fd is_nonblock buf off len
607 | is_nonblock = unsafe_write
608 | threaded = safe_write
609 | otherwise = do r <- fdReady (fromIntegral fd) 1 0 False
610 if r /= 0
611 then safe_write
612 else do threadWaitWrite (fromIntegral fd); unsafe_write
613 where
614 do_write call = throwErrnoIfMinus1RetryMayBlock loc call
615 (threadWaitWrite (fromIntegral fd))
616 unsafe_write = do_write (write_off fd buf off len)
617 safe_write = do_write (safe_write_off (fromIntegral fd) buf off len)
618
619 foreign import ccall unsafe "__hscore_PrelHandle_read"
620 read_rawBuffer :: CInt -> RawBuffer -> Int -> CInt -> IO CInt
621
622 foreign import ccall unsafe "__hscore_PrelHandle_read"
623 read_off :: CInt -> Ptr CChar -> Int -> CInt -> IO CInt
624
625 foreign import ccall unsafe "__hscore_PrelHandle_write"
626 write_rawBuffer :: CInt -> RawBuffer -> Int -> CInt -> IO CInt
627
628 foreign import ccall unsafe "__hscore_PrelHandle_write"
629 write_off :: CInt -> Ptr CChar -> Int -> CInt -> IO CInt
630
631 foreign import ccall safe "fdReady"
632 fdReady :: CInt -> CInt -> CInt -> Bool -> IO CInt
633
634 #else /* mingw32_HOST_OS.... */
635
636 readRawBuffer :: String -> FD -> Bool -> RawBuffer -> Int -> CInt -> IO CInt
637 readRawBuffer loc fd is_stream buf off len
638 | threaded = blockingReadRawBuffer loc fd is_stream buf off len
639 | otherwise = asyncReadRawBuffer loc fd is_stream buf off len
640
641 readRawBufferPtr :: String -> FD -> Bool -> Ptr CChar -> Int -> CInt -> IO CInt
642 readRawBufferPtr loc fd is_stream buf off len
643 | threaded = blockingReadRawBufferPtr loc fd is_stream buf off len
644 | otherwise = asyncReadRawBufferPtr loc fd is_stream buf off len
645
646 writeRawBuffer :: String -> FD -> Bool -> RawBuffer -> Int -> CInt -> IO CInt
647 writeRawBuffer loc fd is_stream buf off len
648 | threaded = blockingWriteRawBuffer loc fd is_stream buf off len
649 | otherwise = asyncWriteRawBuffer loc fd is_stream buf off len
650
651 writeRawBufferPtr :: String -> FD -> Bool -> Ptr CChar -> Int -> CInt -> IO CInt
652 writeRawBufferPtr loc fd is_stream buf off len
653 | threaded = blockingWriteRawBufferPtr loc fd is_stream buf off len
654 | otherwise = asyncWriteRawBufferPtr loc fd is_stream buf off len
655
656 -- ToDo: we don't have a non-blocking primitve read on Win32
657 readRawBufferNoBlock :: String -> FD -> Bool -> RawBuffer -> Int -> CInt -> IO CInt
658 readRawBufferNoBlock = readRawBuffer
659
660 -- Async versions of the read/write primitives, for the non-threaded RTS
661
662 asyncReadRawBuffer loc fd is_stream buf off len = do
663 (l, rc) <- asyncReadBA (fromIntegral fd) (if is_stream then 1 else 0)
664 (fromIntegral len) off buf
665 if l == (-1)
666 then
667 ioError (errnoToIOError loc (Errno (fromIntegral rc)) Nothing Nothing)
668 else return (fromIntegral l)
669
670 asyncReadRawBufferPtr loc fd is_stream buf off len = do
671 (l, rc) <- asyncRead (fromIntegral fd) (if is_stream then 1 else 0)
672 (fromIntegral len) (buf `plusPtr` off)
673 if l == (-1)
674 then
675 ioError (errnoToIOError loc (Errno (fromIntegral rc)) Nothing Nothing)
676 else return (fromIntegral l)
677
678 asyncWriteRawBuffer loc fd is_stream buf off len = do
679 (l, rc) <- asyncWriteBA (fromIntegral fd) (if is_stream then 1 else 0)
680 (fromIntegral len) off buf
681 if l == (-1)
682 then
683 ioError (errnoToIOError loc (Errno (fromIntegral rc)) Nothing Nothing)
684 else return (fromIntegral l)
685
686 asyncWriteRawBufferPtr loc fd is_stream buf off len = do
687 (l, rc) <- asyncWrite (fromIntegral fd) (if is_stream then 1 else 0)
688 (fromIntegral len) (buf `plusPtr` off)
689 if l == (-1)
690 then
691 ioError (errnoToIOError loc (Errno (fromIntegral rc)) Nothing Nothing)
692 else return (fromIntegral l)
693
694 -- Blocking versions of the read/write primitives, for the threaded RTS
695
696 blockingReadRawBuffer loc fd True buf off len =
697 throwErrnoIfMinus1Retry loc $
698 safe_recv_rawBuffer fd buf off len
699 blockingReadRawBuffer loc fd False buf off len =
700 throwErrnoIfMinus1Retry loc $
701 safe_read_rawBuffer fd buf off len
702
703 blockingReadRawBufferPtr loc fd True buf off len =
704 throwErrnoIfMinus1Retry loc $
705 safe_recv_off fd buf off len
706 blockingReadRawBufferPtr loc fd False buf off len =
707 throwErrnoIfMinus1Retry loc $
708 safe_read_off fd buf off len
709
710 blockingWriteRawBuffer loc fd True buf off len =
711 throwErrnoIfMinus1Retry loc $
712 safe_send_rawBuffer fd buf off len
713 blockingWriteRawBuffer loc fd False buf off len =
714 throwErrnoIfMinus1Retry loc $
715 safe_write_rawBuffer fd buf off len
716
717 blockingWriteRawBufferPtr loc fd True buf off len =
718 throwErrnoIfMinus1Retry loc $
719 safe_send_off fd buf off len
720 blockingWriteRawBufferPtr loc fd False buf off len =
721 throwErrnoIfMinus1Retry loc $
722 safe_write_off fd buf off len
723
724 -- NOTE: "safe" versions of the read/write calls for use by the threaded RTS.
725 -- These calls may block, but that's ok.
726
727 foreign import ccall safe "__hscore_PrelHandle_recv"
728 safe_recv_rawBuffer :: CInt -> RawBuffer -> Int -> CInt -> IO CInt
729
730 foreign import ccall safe "__hscore_PrelHandle_recv"
731 safe_recv_off :: CInt -> Ptr CChar -> Int -> CInt -> IO CInt
732
733 foreign import ccall safe "__hscore_PrelHandle_send"
734 safe_send_rawBuffer :: CInt -> RawBuffer -> Int -> CInt -> IO CInt
735
736 foreign import ccall safe "__hscore_PrelHandle_send"
737 safe_send_off :: CInt -> Ptr CChar -> Int -> CInt -> IO CInt
738
739 #endif
740
741 foreign import ccall "rtsSupportsBoundThreads" threaded :: Bool
742
743 foreign import ccall safe "__hscore_PrelHandle_read"
744 safe_read_rawBuffer :: FD -> RawBuffer -> Int -> CInt -> IO CInt
745
746 foreign import ccall safe "__hscore_PrelHandle_read"
747 safe_read_off :: FD -> Ptr CChar -> Int -> CInt -> IO CInt
748
749 foreign import ccall safe "__hscore_PrelHandle_write"
750 safe_write_rawBuffer :: CInt -> RawBuffer -> Int -> CInt -> IO CInt
751
752 foreign import ccall safe "__hscore_PrelHandle_write"
753 safe_write_off :: CInt -> Ptr CChar -> Int -> CInt -> IO CInt
754
755 -- ---------------------------------------------------------------------------
756 -- Standard Handles
757
758 -- Three handles are allocated during program initialisation. The first
759 -- two manage input or output from the Haskell program's standard input
760 -- or output channel respectively. The third manages output to the
761 -- standard error channel. These handles are initially open.
762
763 fd_stdin = 0 :: FD
764 fd_stdout = 1 :: FD
765 fd_stderr = 2 :: FD
766
767 -- | A handle managing input from the Haskell program's standard input channel.
768 stdin :: Handle
769 stdin = unsafePerformIO $ do
770 -- ToDo: acquire lock
771 -- We don't set non-blocking mode on standard handles, because it may
772 -- confuse other applications attached to the same TTY/pipe
773 -- see Note [nonblock]
774 (buf, bmode) <- getBuffer fd_stdin ReadBuffer
775 mkStdHandle fd_stdin "<stdin>" ReadHandle buf bmode
776
777 -- | A handle managing output to the Haskell program's standard output channel.
778 stdout :: Handle
779 stdout = 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_stdout WriteBuffer
785 mkStdHandle fd_stdout "<stdout>" WriteHandle buf bmode
786
787 -- | A handle managing output to the Haskell program's standard error channel.
788 stderr :: Handle
789 stderr = 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 <- mkUnBuffer
795 mkStdHandle fd_stderr "<stderr>" WriteHandle buf NoBuffering
796
797 -- ---------------------------------------------------------------------------
798 -- Opening and Closing Files
799
800 addFilePathToIOError fun fp (IOError h iot _ str _)
801 = IOError h iot fun str (Just fp)
802
803 -- | Computation 'openFile' @file mode@ allocates and returns a new, open
804 -- handle to manage the file @file@. It manages input if @mode@
805 -- is 'ReadMode', output if @mode@ is 'WriteMode' or 'AppendMode',
806 -- and both input and output if mode is 'ReadWriteMode'.
807 --
808 -- If the file does not exist and it is opened for output, it should be
809 -- created as a new file. If @mode@ is 'WriteMode' and the file
810 -- already exists, then it should be truncated to zero length.
811 -- Some operating systems delete empty files, so there is no guarantee
812 -- that the file will exist following an 'openFile' with @mode@
813 -- 'WriteMode' unless it is subsequently written to successfully.
814 -- The handle is positioned at the end of the file if @mode@ is
815 -- 'AppendMode', and otherwise at the beginning (in which case its
816 -- internal position is 0).
817 -- The initial buffer mode is implementation-dependent.
818 --
819 -- This operation may fail with:
820 --
821 -- * 'isAlreadyInUseError' if the file is already open and cannot be reopened;
822 --
823 -- * 'isDoesNotExistError' if the file does not exist; or
824 --
825 -- * 'isPermissionError' if the user does not have permission to open the file.
826 --
827 -- Note: if you will be working with files containing binary data, you'll want to
828 -- be using 'openBinaryFile'.
829 openFile :: FilePath -> IOMode -> IO Handle
830 openFile fp im =
831 catch
832 (openFile' fp im dEFAULT_OPEN_IN_BINARY_MODE)
833 (\e -> ioError (addFilePathToIOError "openFile" fp e))
834
835 -- | Like 'openFile', but open the file in binary mode.
836 -- On Windows, reading a file in text mode (which is the default)
837 -- will translate CRLF to LF, and writing will translate LF to CRLF.
838 -- This is usually what you want with text files. With binary files
839 -- this is undesirable; also, as usual under Microsoft operating systems,
840 -- text mode treats control-Z as EOF. Binary mode turns off all special
841 -- treatment of end-of-line and end-of-file characters.
842 -- (See also 'hSetBinaryMode'.)
843
844 openBinaryFile :: FilePath -> IOMode -> IO Handle
845 openBinaryFile fp m =
846 catch
847 (openFile' fp m True)
848 (\e -> ioError (addFilePathToIOError "openBinaryFile" fp e))
849
850 openFile' filepath mode binary =
851 withCString filepath $ \ f ->
852
853 let
854 oflags1 = case mode of
855 ReadMode -> read_flags
856 #ifdef mingw32_HOST_OS
857 WriteMode -> write_flags .|. o_TRUNC
858 #else
859 WriteMode -> write_flags
860 #endif
861 ReadWriteMode -> rw_flags
862 AppendMode -> append_flags
863
864 binary_flags
865 | binary = o_BINARY
866 | otherwise = 0
867
868 oflags = oflags1 .|. binary_flags
869 in do
870
871 -- the old implementation had a complicated series of three opens,
872 -- which is perhaps because we have to be careful not to open
873 -- directories. However, the man pages I've read say that open()
874 -- always returns EISDIR if the file is a directory and was opened
875 -- for writing, so I think we're ok with a single open() here...
876 fd <- throwErrnoIfMinus1Retry "openFile"
877 (c_open f (fromIntegral oflags) 0o666)
878
879 stat@(fd_type,_,_) <- fdStat fd
880
881 h <- fdToHandle' fd (Just stat) False filepath mode binary
882 `catchException` \e -> do c_close fd; throw e
883 -- NB. don't forget to close the FD if fdToHandle' fails, otherwise
884 -- this FD leaks.
885 -- ASSERT: if we just created the file, then fdToHandle' won't fail
886 -- (so we don't need to worry about removing the newly created file
887 -- in the event of an error).
888
889 #ifndef mingw32_HOST_OS
890 -- we want to truncate() if this is an open in WriteMode, but only
891 -- if the target is a RegularFile. ftruncate() fails on special files
892 -- like /dev/null.
893 if mode == WriteMode && fd_type == RegularFile
894 then throwErrnoIf (/=0) "openFile"
895 (c_ftruncate fd 0)
896 else return 0
897 #endif
898 return h
899
900
901 std_flags = o_NONBLOCK .|. o_NOCTTY
902 output_flags = std_flags .|. o_CREAT
903 read_flags = std_flags .|. o_RDONLY
904 write_flags = output_flags .|. o_WRONLY
905 rw_flags = output_flags .|. o_RDWR
906 append_flags = write_flags .|. o_APPEND
907
908 -- ---------------------------------------------------------------------------
909 -- fdToHandle'
910
911 fdToHandle' :: FD
912 -> Maybe (FDType, CDev, CIno)
913 -> Bool
914 -> FilePath
915 -> IOMode
916 -> Bool
917 -> IO Handle
918
919 fdToHandle' fd mb_stat is_socket filepath mode binary = do
920 -- turn on non-blocking mode
921 setNonBlockingFD fd
922
923 #ifdef mingw32_HOST_OS
924 -- On Windows, the is_stream flag indicates that the Handle is a socket
925 let is_stream = is_socket
926 #else
927 -- On Unix, the is_stream flag indicates that the FD is non-blocking
928 let is_stream = True
929 #endif
930
931 let (ha_type, write) =
932 case mode of
933 ReadMode -> ( ReadHandle, False )
934 WriteMode -> ( WriteHandle, True )
935 ReadWriteMode -> ( ReadWriteHandle, True )
936 AppendMode -> ( AppendHandle, True )
937
938 -- open() won't tell us if it was a directory if we only opened for
939 -- reading, so check again.
940 (fd_type,dev,ino) <-
941 case mb_stat of
942 Just x -> return x
943 Nothing -> fdStat fd
944
945 case fd_type of
946 Directory ->
947 ioException (IOError Nothing InappropriateType "openFile"
948 "is a directory" Nothing)
949
950 -- regular files need to be locked
951 RegularFile -> do
952 #ifndef mingw32_HOST_OS
953 r <- lockFile fd dev ino (fromBool write)
954 when (r == -1) $
955 ioException (IOError Nothing ResourceBusy "openFile"
956 "file is locked" Nothing)
957 #endif
958 mkFileHandle fd is_stream filepath ha_type binary
959
960 Stream
961 -- only *Streams* can be DuplexHandles. Other read/write
962 -- Handles must share a buffer.
963 | ReadWriteHandle <- ha_type ->
964 mkDuplexHandle fd is_stream filepath binary
965 | otherwise ->
966 mkFileHandle fd is_stream filepath ha_type binary
967
968 RawDevice ->
969 mkFileHandle fd is_stream filepath ha_type binary
970
971 fdToHandle :: FD -> IO Handle
972 fdToHandle fd = do
973 mode <- fdGetMode fd
974 let fd_str = "<file descriptor: " ++ show fd ++ ">"
975 fdToHandle' fd Nothing False{-XXX!-} fd_str mode True{-bin mode-}
976
977
978 #ifndef mingw32_HOST_OS
979 foreign import ccall unsafe "lockFile"
980 lockFile :: CInt -> CDev -> CIno -> CInt -> IO CInt
981
982 foreign import ccall unsafe "unlockFile"
983 unlockFile :: CInt -> IO CInt
984 #endif
985
986 mkStdHandle :: FD -> FilePath -> HandleType -> IORef Buffer -> BufferMode
987 -> IO Handle
988 mkStdHandle fd filepath ha_type buf bmode = do
989 spares <- newIORef BufferListNil
990 newFileHandle filepath (stdHandleFinalizer filepath)
991 (Handle__ { haFD = fd,
992 haType = ha_type,
993 haIsBin = dEFAULT_OPEN_IN_BINARY_MODE,
994 haIsStream = False, -- means FD is blocking on Unix
995 haBufferMode = bmode,
996 haBuffer = buf,
997 haBuffers = spares,
998 haOtherSide = Nothing
999 })
1000
1001 mkFileHandle :: FD -> Bool -> FilePath -> HandleType -> Bool -> IO Handle
1002 mkFileHandle fd is_stream filepath ha_type binary = do
1003 (buf, bmode) <- getBuffer fd (initBufferState ha_type)
1004
1005 #ifdef mingw32_HOST_OS
1006 -- On Windows, if this is a read/write handle and we are in text mode,
1007 -- turn off buffering. We don't correctly handle the case of switching
1008 -- from read mode to write mode on a buffered text-mode handle, see bug
1009 -- \#679.
1010 bmode <- case ha_type of
1011 ReadWriteHandle | not binary -> return NoBuffering
1012 _other -> return bmode
1013 #endif
1014
1015 spares <- newIORef BufferListNil
1016 newFileHandle filepath (handleFinalizer filepath)
1017 (Handle__ { haFD = fd,
1018 haType = ha_type,
1019 haIsBin = binary,
1020 haIsStream = is_stream,
1021 haBufferMode = bmode,
1022 haBuffer = buf,
1023 haBuffers = spares,
1024 haOtherSide = Nothing
1025 })
1026
1027 mkDuplexHandle :: FD -> Bool -> FilePath -> Bool -> IO Handle
1028 mkDuplexHandle fd is_stream filepath binary = do
1029 (w_buf, w_bmode) <- getBuffer fd WriteBuffer
1030 w_spares <- newIORef BufferListNil
1031 let w_handle_ =
1032 Handle__ { haFD = fd,
1033 haType = WriteHandle,
1034 haIsBin = binary,
1035 haIsStream = is_stream,
1036 haBufferMode = w_bmode,
1037 haBuffer = w_buf,
1038 haBuffers = w_spares,
1039 haOtherSide = Nothing
1040 }
1041 write_side <- newMVar w_handle_
1042
1043 (r_buf, r_bmode) <- getBuffer fd ReadBuffer
1044 r_spares <- newIORef BufferListNil
1045 let r_handle_ =
1046 Handle__ { haFD = fd,
1047 haType = ReadHandle,
1048 haIsBin = binary,
1049 haIsStream = is_stream,
1050 haBufferMode = r_bmode,
1051 haBuffer = r_buf,
1052 haBuffers = r_spares,
1053 haOtherSide = Just write_side
1054 }
1055 read_side <- newMVar r_handle_
1056
1057 addMVarFinalizer write_side (handleFinalizer filepath write_side)
1058 return (DuplexHandle filepath read_side write_side)
1059
1060
1061 initBufferState ReadHandle = ReadBuffer
1062 initBufferState _ = WriteBuffer
1063
1064 -- ---------------------------------------------------------------------------
1065 -- Closing a handle
1066
1067 -- | Computation 'hClose' @hdl@ makes handle @hdl@ closed. Before the
1068 -- computation finishes, if @hdl@ is writable its buffer is flushed as
1069 -- for 'hFlush'.
1070 -- Performing 'hClose' on a handle that has already been closed has no effect;
1071 -- doing so not an error. All other operations on a closed handle will fail.
1072 -- If 'hClose' fails for any reason, any further operations (apart from
1073 -- 'hClose') on the handle will still fail as if @hdl@ had been successfully
1074 -- closed.
1075
1076 hClose :: Handle -> IO ()
1077 hClose h@(FileHandle _ m) = hClose' h m
1078 hClose h@(DuplexHandle _ r w) = hClose' h w >> hClose' h r
1079
1080 hClose' h m = withHandle__' "hClose" h m $ hClose_help
1081
1082 -- hClose_help is also called by lazyRead (in PrelIO) when EOF is read
1083 -- or an IO error occurs on a lazy stream. The semi-closed Handle is
1084 -- then closed immediately. We have to be careful with DuplexHandles
1085 -- though: we have to leave the closing to the finalizer in that case,
1086 -- because the write side may still be in use.
1087 hClose_help :: Handle__ -> IO Handle__
1088 hClose_help handle_ =
1089 case haType handle_ of
1090 ClosedHandle -> return handle_
1091 _ -> do flushWriteBufferOnly handle_ -- interruptible
1092 hClose_handle_ handle_
1093
1094 hClose_handle_ handle_ = do
1095 let fd = haFD handle_
1096
1097 -- close the file descriptor, but not when this is the read
1098 -- side of a duplex handle.
1099 case haOtherSide handle_ of
1100 Nothing ->
1101 throwErrnoIfMinus1Retry_ "hClose"
1102 #ifdef mingw32_HOST_OS
1103 (closeFd (haIsStream handle_) fd)
1104 #else
1105 (c_close fd)
1106 #endif
1107 Just _ -> return ()
1108
1109 -- free the spare buffers
1110 writeIORef (haBuffers handle_) BufferListNil
1111 writeIORef (haBuffer handle_) noBuffer
1112
1113 #ifndef mingw32_HOST_OS
1114 -- unlock it
1115 unlockFile fd
1116 #endif
1117
1118 -- we must set the fd to -1, because the finalizer is going
1119 -- to run eventually and try to close/unlock it.
1120 return (handle_{ haFD = -1,
1121 haType = ClosedHandle
1122 })
1123
1124 {-# NOINLINE noBuffer #-}
1125 noBuffer = unsafePerformIO $ allocateBuffer 1 ReadBuffer
1126
1127 -----------------------------------------------------------------------------
1128 -- Detecting and changing the size of a file
1129
1130 -- | For a handle @hdl@ which attached to a physical file,
1131 -- 'hFileSize' @hdl@ returns the size of that file in 8-bit bytes.
1132
1133 hFileSize :: Handle -> IO Integer
1134 hFileSize handle =
1135 withHandle_ "hFileSize" handle $ \ handle_ -> do
1136 case haType handle_ of
1137 ClosedHandle -> ioe_closedHandle
1138 SemiClosedHandle -> ioe_closedHandle
1139 _ -> do flushWriteBufferOnly handle_
1140 r <- fdFileSize (haFD handle_)
1141 if r /= -1
1142 then return r
1143 else ioException (IOError Nothing InappropriateType "hFileSize"
1144 "not a regular file" Nothing)
1145
1146
1147 -- | 'hSetFileSize' @hdl@ @size@ truncates the physical file with handle @hdl@ to @size@ bytes.
1148
1149 hSetFileSize :: Handle -> Integer -> IO ()
1150 hSetFileSize handle size =
1151 withHandle_ "hSetFileSize" handle $ \ handle_ -> do
1152 case haType handle_ of
1153 ClosedHandle -> ioe_closedHandle
1154 SemiClosedHandle -> ioe_closedHandle
1155 _ -> do flushWriteBufferOnly handle_
1156 throwErrnoIf (/=0) "hSetFileSize"
1157 (c_ftruncate (haFD handle_) (fromIntegral size))
1158 return ()
1159
1160 -- ---------------------------------------------------------------------------
1161 -- Detecting the End of Input
1162
1163 -- | For a readable handle @hdl@, 'hIsEOF' @hdl@ returns
1164 -- 'True' if no further input can be taken from @hdl@ or for a
1165 -- physical file, if the current I\/O position is equal to the length of
1166 -- the file. Otherwise, it returns 'False'.
1167
1168 hIsEOF :: Handle -> IO Bool
1169 hIsEOF handle =
1170 catch
1171 (do hLookAhead handle; return False)
1172 (\e -> if isEOFError e then return True else ioError e)
1173
1174 -- | The computation 'isEOF' is identical to 'hIsEOF',
1175 -- except that it works only on 'stdin'.
1176
1177 isEOF :: IO Bool
1178 isEOF = hIsEOF stdin
1179
1180 -- ---------------------------------------------------------------------------
1181 -- Looking ahead
1182
1183 -- | Computation 'hLookAhead' returns the next character from the handle
1184 -- without removing it from the input buffer, blocking until a character
1185 -- is available.
1186 --
1187 -- This operation may fail with:
1188 --
1189 -- * 'isEOFError' if the end of file has been reached.
1190
1191 hLookAhead :: Handle -> IO Char
1192 hLookAhead handle = do
1193 wantReadableHandle "hLookAhead" handle $ \handle_ -> do
1194 let ref = haBuffer handle_
1195 fd = haFD handle_
1196 is_line = haBufferMode handle_ == LineBuffering
1197 buf <- readIORef ref
1198
1199 -- fill up the read buffer if necessary
1200 new_buf <- if bufferEmpty buf
1201 then fillReadBuffer fd True (haIsStream handle_) buf
1202 else return buf
1203
1204 writeIORef ref new_buf
1205
1206 (c,_) <- readCharFromBuffer (bufBuf buf) (bufRPtr buf)
1207 return c
1208
1209 -- ---------------------------------------------------------------------------
1210 -- Buffering Operations
1211
1212 -- Three kinds of buffering are supported: line-buffering,
1213 -- block-buffering or no-buffering. See GHC.IOBase for definition and
1214 -- further explanation of what the type represent.
1215
1216 -- | Computation 'hSetBuffering' @hdl mode@ sets the mode of buffering for
1217 -- handle @hdl@ on subsequent reads and writes.
1218 --
1219 -- If the buffer mode is changed from 'BlockBuffering' or
1220 -- 'LineBuffering' to 'NoBuffering', then
1221 --
1222 -- * if @hdl@ is writable, the buffer is flushed as for 'hFlush';
1223 --
1224 -- * if @hdl@ is not writable, the contents of the buffer is discarded.
1225 --
1226 -- This operation may fail with:
1227 --
1228 -- * 'isPermissionError' if the handle has already been used for reading
1229 -- or writing and the implementation does not allow the buffering mode
1230 -- to be changed.
1231
1232 hSetBuffering :: Handle -> BufferMode -> IO ()
1233 hSetBuffering handle mode =
1234 withAllHandles__ "hSetBuffering" handle $ \ handle_ -> do
1235 case haType handle_ of
1236 ClosedHandle -> ioe_closedHandle
1237 _ -> do
1238 {- Note:
1239 - we flush the old buffer regardless of whether
1240 the new buffer could fit the contents of the old buffer
1241 or not.
1242 - allow a handle's buffering to change even if IO has
1243 occurred (ANSI C spec. does not allow this, nor did
1244 the previous implementation of IO.hSetBuffering).
1245 - a non-standard extension is to allow the buffering
1246 of semi-closed handles to change [sof 6/98]
1247 -}
1248 flushBuffer handle_
1249
1250 let state = initBufferState (haType handle_)
1251 new_buf <-
1252 case mode of
1253 -- we always have a 1-character read buffer for
1254 -- unbuffered handles: it's needed to
1255 -- support hLookAhead.
1256 NoBuffering -> allocateBuffer 1 ReadBuffer
1257 LineBuffering -> allocateBuffer dEFAULT_BUFFER_SIZE state
1258 BlockBuffering Nothing -> allocateBuffer dEFAULT_BUFFER_SIZE state
1259 BlockBuffering (Just n) | n <= 0 -> ioe_bufsiz n
1260 | otherwise -> allocateBuffer n state
1261 writeIORef (haBuffer handle_) new_buf
1262
1263 -- for input terminals we need to put the terminal into
1264 -- cooked or raw mode depending on the type of buffering.
1265 is_tty <- fdIsTTY (haFD handle_)
1266 when (is_tty && isReadableHandleType (haType handle_)) $
1267 case mode of
1268 #ifndef mingw32_HOST_OS
1269 -- 'raw' mode under win32 is a bit too specialised (and troublesome
1270 -- for most common uses), so simply disable its use here.
1271 NoBuffering -> setCooked (haFD handle_) False
1272 #else
1273 NoBuffering -> return ()
1274 #endif
1275 _ -> setCooked (haFD handle_) True
1276
1277 -- throw away spare buffers, they might be the wrong size
1278 writeIORef (haBuffers handle_) BufferListNil
1279
1280 return (handle_{ haBufferMode = mode })
1281
1282 -- -----------------------------------------------------------------------------
1283 -- hFlush
1284
1285 -- | The action 'hFlush' @hdl@ causes any items buffered for output
1286 -- in handle @hdl@ to be sent immediately to the operating system.
1287 --
1288 -- This operation may fail with:
1289 --
1290 -- * 'isFullError' if the device is full;
1291 --
1292 -- * 'isPermissionError' if a system resource limit would be exceeded.
1293 -- It is unspecified whether the characters in the buffer are discarded
1294 -- or retained under these circumstances.
1295
1296 hFlush :: Handle -> IO ()
1297 hFlush handle =
1298 wantWritableHandle "hFlush" handle $ \ handle_ -> do
1299 buf <- readIORef (haBuffer handle_)
1300 if bufferIsWritable buf && not (bufferEmpty buf)
1301 then do flushed_buf <- flushWriteBuffer (haFD handle_) (haIsStream handle_) buf
1302 writeIORef (haBuffer handle_) flushed_buf
1303 else return ()
1304
1305
1306 -- -----------------------------------------------------------------------------
1307 -- Repositioning Handles
1308
1309 data HandlePosn = HandlePosn Handle HandlePosition
1310
1311 instance Eq HandlePosn where
1312 (HandlePosn h1 p1) == (HandlePosn h2 p2) = p1==p2 && h1==h2
1313
1314 instance Show HandlePosn where
1315 showsPrec p (HandlePosn h pos) =
1316 showsPrec p h . showString " at position " . shows pos
1317
1318 -- HandlePosition is the Haskell equivalent of POSIX' off_t.
1319 -- We represent it as an Integer on the Haskell side, but
1320 -- cheat slightly in that hGetPosn calls upon a C helper
1321 -- that reports the position back via (merely) an Int.
1322 type HandlePosition = Integer
1323
1324 -- | Computation 'hGetPosn' @hdl@ returns the current I\/O position of
1325 -- @hdl@ as a value of the abstract type 'HandlePosn'.
1326
1327 hGetPosn :: Handle -> IO HandlePosn
1328 hGetPosn handle = do
1329 posn <- hTell handle
1330 return (HandlePosn handle posn)
1331
1332 -- | If a call to 'hGetPosn' @hdl@ returns a position @p@,
1333 -- then computation 'hSetPosn' @p@ sets the position of @hdl@
1334 -- to the position it held at the time of the call to 'hGetPosn'.
1335 --
1336 -- This operation may fail with:
1337 --
1338 -- * 'isPermissionError' if a system resource limit would be exceeded.
1339
1340 hSetPosn :: HandlePosn -> IO ()
1341 hSetPosn (HandlePosn h i) = hSeek h AbsoluteSeek i
1342
1343 -- ---------------------------------------------------------------------------
1344 -- hSeek
1345
1346 -- | A mode that determines the effect of 'hSeek' @hdl mode i@, as follows:
1347 data SeekMode
1348 = AbsoluteSeek -- ^ the position of @hdl@ is set to @i@.
1349 | RelativeSeek -- ^ the position of @hdl@ is set to offset @i@
1350 -- from the current position.
1351 | SeekFromEnd -- ^ the position of @hdl@ is set to offset @i@
1352 -- from the end of the file.
1353 deriving (Eq, Ord, Ix, Enum, Read, Show)
1354
1355 {- Note:
1356 - when seeking using `SeekFromEnd', positive offsets (>=0) means
1357 seeking at or past EOF.
1358
1359 - we possibly deviate from the report on the issue of seeking within
1360 the buffer and whether to flush it or not. The report isn't exactly
1361 clear here.
1362 -}
1363
1364 -- | Computation 'hSeek' @hdl mode i@ sets the position of handle
1365 -- @hdl@ depending on @mode@.
1366 -- The offset @i@ is given in terms of 8-bit bytes.
1367 --
1368 -- If @hdl@ is block- or line-buffered, then seeking to a position which is not
1369 -- in the current buffer will first cause any items in the output buffer to be
1370 -- written to the device, and then cause the input buffer to be discarded.
1371 -- Some handles may not be seekable (see 'hIsSeekable'), or only support a
1372 -- subset of the possible positioning operations (for instance, it may only
1373 -- be possible to seek to the end of a tape, or to a positive offset from
1374 -- the beginning or current position).
1375 -- It is not possible to set a negative I\/O position, or for
1376 -- a physical file, an I\/O position beyond the current end-of-file.
1377 --
1378 -- This operation may fail with:
1379 --
1380 -- * 'isPermissionError' if a system resource limit would be exceeded.
1381
1382 hSeek :: Handle -> SeekMode -> Integer -> IO ()
1383 hSeek handle mode offset =
1384 wantSeekableHandle "hSeek" handle $ \ handle_ -> do
1385 # ifdef DEBUG_DUMP
1386 puts ("hSeek " ++ show (mode,offset) ++ "\n")
1387 # endif
1388 let ref = haBuffer handle_
1389 buf <- readIORef ref
1390 let r = bufRPtr buf
1391 w = bufWPtr buf
1392 fd = haFD handle_
1393
1394 let do_seek =
1395 throwErrnoIfMinus1Retry_ "hSeek"
1396 (c_lseek (haFD handle_) (fromIntegral offset) whence)
1397
1398 whence :: CInt
1399 whence = case mode of
1400 AbsoluteSeek -> sEEK_SET
1401 RelativeSeek -> sEEK_CUR
1402 SeekFromEnd -> sEEK_END
1403
1404 if bufferIsWritable buf
1405 then do new_buf <- flushWriteBuffer fd (haIsStream handle_) buf
1406 writeIORef ref new_buf
1407 do_seek
1408 else do
1409
1410 if mode == RelativeSeek && offset >= 0 && offset < fromIntegral (w - r)
1411 then writeIORef ref buf{ bufRPtr = r + fromIntegral offset }
1412 else do
1413
1414 new_buf <- flushReadBuffer (haFD handle_) buf
1415 writeIORef ref new_buf
1416 do_seek
1417
1418
1419 hTell :: Handle -> IO Integer
1420 hTell handle =
1421 wantSeekableHandle "hGetPosn" handle $ \ handle_ -> do
1422
1423 #if defined(mingw32_HOST_OS)
1424 -- urgh, on Windows we have to worry about \n -> \r\n translation,
1425 -- so we can't easily calculate the file position using the
1426 -- current buffer size. Just flush instead.
1427 flushBuffer handle_
1428 #endif
1429 let fd = haFD handle_
1430 posn <- fromIntegral `liftM`
1431 throwErrnoIfMinus1Retry "hGetPosn"
1432 (c_lseek fd 0 sEEK_CUR)
1433
1434 let ref = haBuffer handle_
1435 buf <- readIORef ref
1436
1437 let real_posn
1438 | bufferIsWritable buf = posn + fromIntegral (bufWPtr buf)
1439 | otherwise = posn - fromIntegral (bufWPtr buf - bufRPtr buf)
1440 # ifdef DEBUG_DUMP
1441 puts ("\nhGetPosn: (fd, posn, real_posn) = " ++ show (fd, posn, real_posn) ++ "\n")
1442 puts (" (bufWPtr, bufRPtr) = " ++ show (bufWPtr buf, bufRPtr buf) ++ "\n")
1443 # endif
1444 return real_posn
1445
1446 -- -----------------------------------------------------------------------------
1447 -- Handle Properties
1448
1449 -- A number of operations return information about the properties of a
1450 -- handle. Each of these operations returns `True' if the handle has
1451 -- the specified property, and `False' otherwise.
1452
1453 hIsOpen :: Handle -> IO Bool
1454 hIsOpen handle =
1455 withHandle_ "hIsOpen" handle $ \ handle_ -> do
1456 case haType handle_ of
1457 ClosedHandle -> return False
1458 SemiClosedHandle -> return False
1459 _ -> return True
1460
1461 hIsClosed :: Handle -> IO Bool
1462 hIsClosed handle =
1463 withHandle_ "hIsClosed" handle $ \ handle_ -> do
1464 case haType handle_ of
1465 ClosedHandle -> return True
1466 _ -> return False
1467
1468 {- not defined, nor exported, but mentioned
1469 here for documentation purposes:
1470
1471 hSemiClosed :: Handle -> IO Bool
1472 hSemiClosed h = do
1473 ho <- hIsOpen h
1474 hc <- hIsClosed h
1475 return (not (ho || hc))
1476 -}
1477
1478 hIsReadable :: Handle -> IO Bool
1479 hIsReadable (DuplexHandle _ _ _) = return True
1480 hIsReadable handle =
1481 withHandle_ "hIsReadable" handle $ \ handle_ -> do
1482 case haType handle_ of
1483 ClosedHandle -> ioe_closedHandle
1484 SemiClosedHandle -> ioe_closedHandle
1485 htype -> return (isReadableHandleType htype)
1486
1487 hIsWritable :: Handle -> IO Bool
1488 hIsWritable (DuplexHandle _ _ _) = return True
1489 hIsWritable handle =
1490 withHandle_ "hIsWritable" handle $ \ handle_ -> do
1491 case haType handle_ of
1492 ClosedHandle -> ioe_closedHandle
1493 SemiClosedHandle -> ioe_closedHandle
1494 htype -> return (isWritableHandleType htype)
1495
1496 -- | Computation 'hGetBuffering' @hdl@ returns the current buffering mode
1497 -- for @hdl@.
1498
1499 hGetBuffering :: Handle -> IO BufferMode
1500 hGetBuffering handle =
1501 withHandle_ "hGetBuffering" handle $ \ handle_ -> do
1502 case haType handle_ of
1503 ClosedHandle -> ioe_closedHandle
1504 _ ->
1505 -- We're being non-standard here, and allow the buffering
1506 -- of a semi-closed handle to be queried. -- sof 6/98
1507 return (haBufferMode handle_) -- could be stricter..
1508
1509 hIsSeekable :: Handle -> IO Bool
1510 hIsSeekable handle =
1511 withHandle_ "hIsSeekable" handle $ \ handle_ -> do
1512 case haType handle_ of
1513 ClosedHandle -> ioe_closedHandle
1514 SemiClosedHandle -> ioe_closedHandle
1515 AppendHandle -> return False
1516 _ -> do t <- fdType (haFD handle_)
1517 return ((t == RegularFile || t == RawDevice)
1518 && (haIsBin handle_ || tEXT_MODE_SEEK_ALLOWED))
1519
1520 -- -----------------------------------------------------------------------------
1521 -- Changing echo status (Non-standard GHC extensions)
1522
1523 -- | Set the echoing status of a handle connected to a terminal.
1524
1525 hSetEcho :: Handle -> Bool -> IO ()
1526 hSetEcho handle on = do
1527 isT <- hIsTerminalDevice handle
1528 if not isT
1529 then return ()
1530 else
1531 withHandle_ "hSetEcho" handle $ \ handle_ -> do
1532 case haType handle_ of
1533 ClosedHandle -> ioe_closedHandle
1534 _ -> setEcho (haFD handle_) on
1535
1536 -- | Get the echoing status of a handle connected to a terminal.
1537
1538 hGetEcho :: Handle -> IO Bool
1539 hGetEcho handle = do
1540 isT <- hIsTerminalDevice handle
1541 if not isT
1542 then return False
1543 else
1544 withHandle_ "hGetEcho" handle $ \ handle_ -> do
1545 case haType handle_ of
1546 ClosedHandle -> ioe_closedHandle
1547 _ -> getEcho (haFD handle_)
1548
1549 -- | Is the handle connected to a terminal?
1550
1551 hIsTerminalDevice :: Handle -> IO Bool
1552 hIsTerminalDevice handle = do
1553 withHandle_ "hIsTerminalDevice" handle $ \ handle_ -> do
1554 case haType handle_ of
1555 ClosedHandle -> ioe_closedHandle
1556 _ -> fdIsTTY (haFD handle_)
1557
1558 -- -----------------------------------------------------------------------------
1559 -- hSetBinaryMode
1560
1561 -- | Select binary mode ('True') or text mode ('False') on a open handle.
1562 -- (See also 'openBinaryFile'.)
1563
1564 hSetBinaryMode :: Handle -> Bool -> IO ()
1565 hSetBinaryMode handle bin =
1566 withAllHandles__ "hSetBinaryMode" handle $ \ handle_ ->
1567 do throwErrnoIfMinus1_ "hSetBinaryMode"
1568 (setmode (haFD handle_) bin)
1569 return handle_{haIsBin=bin}
1570
1571 foreign import ccall unsafe "__hscore_setmode"
1572 setmode :: CInt -> Bool -> IO CInt
1573
1574 -- -----------------------------------------------------------------------------
1575 -- Duplicating a Handle
1576
1577 -- | Returns a duplicate of the original handle, with its own buffer.
1578 -- The two Handles will share a file pointer, however. The original
1579 -- handle's buffer is flushed, including discarding any input data,
1580 -- before the handle is duplicated.
1581
1582 hDuplicate :: Handle -> IO Handle
1583 hDuplicate h@(FileHandle path m) = do
1584 new_h_ <- withHandle' "hDuplicate" h m (dupHandle h Nothing)
1585 newFileHandle path (handleFinalizer path) new_h_
1586 hDuplicate h@(DuplexHandle path r w) = do
1587 new_w_ <- withHandle' "hDuplicate" h w (dupHandle h Nothing)
1588 new_w <- newMVar new_w_
1589 new_r_ <- withHandle' "hDuplicate" h r (dupHandle h (Just new_w))
1590 new_r <- newMVar new_r_
1591 addMVarFinalizer new_w (handleFinalizer path new_w)
1592 return (DuplexHandle path new_r new_w)
1593
1594 dupHandle :: Handle -> Maybe (MVar Handle__) -> Handle__
1595 -> IO (Handle__, Handle__)
1596 dupHandle h other_side h_ = do
1597 -- flush the buffer first, so we don't have to copy its contents
1598 flushBuffer h_
1599 new_fd <- case other_side of
1600 Nothing -> throwErrnoIfMinus1 "dupHandle" $ c_dup (haFD h_)
1601 Just r -> withHandle_' "dupHandle" h r (return . haFD)
1602 dupHandle_ other_side h_ new_fd
1603
1604 dupHandleTo other_side hto_ h_ = do
1605 flushBuffer h_
1606 -- Windows' dup2 does not return the new descriptor, unlike Unix
1607 throwErrnoIfMinus1 "dupHandleTo" $
1608 c_dup2 (haFD h_) (haFD hto_)
1609 dupHandle_ other_side h_ (haFD hto_)
1610
1611 dupHandle_ :: Maybe (MVar Handle__) -> Handle__ -> FD
1612 -> IO (Handle__, Handle__)
1613 dupHandle_ other_side h_ new_fd = do
1614 buffer <- allocateBuffer dEFAULT_BUFFER_SIZE (initBufferState (haType h_))
1615 ioref <- newIORef buffer
1616 ioref_buffers <- newIORef BufferListNil
1617
1618 let new_handle_ = h_{ haFD = new_fd,
1619 haBuffer = ioref,
1620 haBuffers = ioref_buffers,
1621 haOtherSide = other_side }
1622 return (h_, new_handle_)
1623
1624 -- -----------------------------------------------------------------------------
1625 -- Replacing a Handle
1626
1627 {- |
1628 Makes the second handle a duplicate of the first handle. The second
1629 handle will be closed first, if it is not already.
1630
1631 This can be used to retarget the standard Handles, for example:
1632
1633 > do h <- openFile "mystdout" WriteMode
1634 > hDuplicateTo h stdout
1635 -}
1636
1637 hDuplicateTo :: Handle -> Handle -> IO ()
1638 hDuplicateTo h1@(FileHandle _ m1) h2@(FileHandle _ m2) = do
1639 withHandle__' "hDuplicateTo" h2 m2 $ \h2_ -> do
1640 _ <- hClose_help h2_
1641 withHandle' "hDuplicateTo" h1 m1 (dupHandleTo Nothing h2_)
1642 hDuplicateTo h1@(DuplexHandle _ r1 w1) h2@(DuplexHandle _ r2 w2) = do
1643 withHandle__' "hDuplicateTo" h2 w2 $ \w2_ -> do
1644 _ <- hClose_help w2_
1645 withHandle' "hDuplicateTo" h1 r1 (dupHandleTo Nothing w2_)
1646 withHandle__' "hDuplicateTo" h2 r2 $ \r2_ -> do
1647 _ <- hClose_help r2_
1648 withHandle' "hDuplicateTo" h1 r1 (dupHandleTo (Just w1) r2_)
1649 hDuplicateTo h1 _ =
1650 ioException (IOError (Just h1) IllegalOperation "hDuplicateTo"
1651 "handles are incompatible" Nothing)
1652
1653 -- ---------------------------------------------------------------------------
1654 -- showing Handles.
1655 --
1656 -- | 'hShow' is in the 'IO' monad, and gives more comprehensive output
1657 -- than the (pure) instance of 'Show' for 'Handle'.
1658
1659 hShow :: Handle -> IO String
1660 hShow h@(FileHandle path _) = showHandle' path False h
1661 hShow h@(DuplexHandle path _ _) = showHandle' path True h
1662
1663 showHandle' filepath is_duplex h =
1664 withHandle_ "showHandle" h $ \hdl_ ->
1665 let
1666 showType | is_duplex = showString "duplex (read-write)"
1667 | otherwise = shows (haType hdl_)
1668 in
1669 return
1670 (( showChar '{' .
1671 showHdl (haType hdl_)
1672 (showString "loc=" . showString filepath . showChar ',' .
1673 showString "type=" . showType . showChar ',' .
1674 showString "binary=" . shows (haIsBin hdl_) . showChar ',' .
1675 showString "buffering=" . showBufMode (unsafePerformIO (readIORef (haBuffer hdl_))) (haBufferMode hdl_) . showString "}" )
1676 ) "")
1677 where
1678
1679 showHdl :: HandleType -> ShowS -> ShowS
1680 showHdl ht cont =
1681 case ht of
1682 ClosedHandle -> shows ht . showString "}"
1683 _ -> cont
1684
1685 showBufMode :: Buffer -> BufferMode -> ShowS
1686 showBufMode buf bmo =
1687 case bmo of
1688 NoBuffering -> showString "none"
1689 LineBuffering -> showString "line"
1690 BlockBuffering (Just n) -> showString "block " . showParen True (shows n)
1691 BlockBuffering Nothing -> showString "block " . showParen True (shows def)
1692 where
1693 def :: Int
1694 def = bufSize buf
1695
1696 -- ---------------------------------------------------------------------------
1697 -- debugging
1698
1699 #if defined(DEBUG_DUMP)
1700 puts :: String -> IO ()
1701 puts s = do write_rawBuffer 1 (unsafeCoerce# (packCString# s)) 0 (fromIntegral (length s))
1702 return ()
1703 #endif
1704
1705 -- -----------------------------------------------------------------------------
1706 -- utils
1707
1708 throwErrnoIfMinus1RetryOnBlock :: String -> IO CInt -> IO CInt -> IO CInt
1709 throwErrnoIfMinus1RetryOnBlock loc f on_block =
1710 do
1711 res <- f
1712 if (res :: CInt) == -1
1713 then do
1714 err <- getErrno
1715 if err == eINTR
1716 then throwErrnoIfMinus1RetryOnBlock loc f on_block
1717 else if err == eWOULDBLOCK || err == eAGAIN
1718 then do on_block
1719 else throwErrno loc
1720 else return res
1721
1722 -- -----------------------------------------------------------------------------
1723 -- wrappers to platform-specific constants:
1724
1725 foreign import ccall unsafe "__hscore_supportsTextMode"
1726 tEXT_MODE_SEEK_ALLOWED :: Bool
1727
1728 foreign import ccall unsafe "__hscore_bufsiz" dEFAULT_BUFFER_SIZE :: Int
1729 foreign import ccall unsafe "__hscore_seek_cur" sEEK_CUR :: CInt
1730 foreign import ccall unsafe "__hscore_seek_set" sEEK_SET :: CInt
1731 foreign import ccall unsafe "__hscore_seek_end" sEEK_END :: CInt