37d78e6427dc54735d2d36c953ef79018d450db4
[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
66 import GHC.Real
67
68 import GHC.Arr
69 import GHC.Base
70 import GHC.Read ( Read )
71 import GHC.List
72 import GHC.IOBase
73 import GHC.Exception
74 import GHC.Enum
75 import GHC.Num ( Integer(..), Num(..) )
76 import GHC.Show
77 import GHC.Real ( toInteger )
78 #if defined(DEBUG_DUMP)
79 import GHC.Pack
80 #endif
81
82 import GHC.Conc
83
84 -- -----------------------------------------------------------------------------
85 -- TODO:
86
87 -- hWaitForInput blocks (should use a timeout)
88
89 -- unbuffered hGetLine is a bit dodgy
90
91 -- hSetBuffering: can't change buffering on a stream,
92 -- when the read buffer is non-empty? (no way to flush the buffer)
93
94 -- ---------------------------------------------------------------------------
95 -- Are files opened by default in text or binary mode, if the user doesn't
96 -- specify?
97
98 dEFAULT_OPEN_IN_BINARY_MODE = False :: Bool
99
100 -- ---------------------------------------------------------------------------
101 -- Creating a new handle
102
103 newFileHandle :: FilePath -> (MVar Handle__ -> IO ()) -> Handle__ -> IO Handle
104 newFileHandle filepath finalizer hc = do
105 m <- newMVar hc
106 addMVarFinalizer m (finalizer m)
107 return (FileHandle filepath m)
108
109 -- ---------------------------------------------------------------------------
110 -- Working with Handles
111
112 {-
113 In the concurrent world, handles are locked during use. This is done
114 by wrapping an MVar around the handle which acts as a mutex over
115 operations on the handle.
116
117 To avoid races, we use the following bracketing operations. The idea
118 is to obtain the lock, do some operation and replace the lock again,
119 whether the operation succeeded or failed. We also want to handle the
120 case where the thread receives an exception while processing the IO
121 operation: in these cases we also want to relinquish the lock.
122
123 There are three versions of @withHandle@: corresponding to the three
124 possible combinations of:
125
126 - the operation may side-effect the handle
127 - the operation may return a result
128
129 If the operation generates an error or an exception is raised, the
130 original handle is always replaced [ this is the case at the moment,
131 but we might want to revisit this in the future --SDM ].
132 -}
133
134 {-# INLINE withHandle #-}
135 withHandle :: String -> Handle -> (Handle__ -> IO (Handle__,a)) -> IO a
136 withHandle fun h@(FileHandle _ m) act = withHandle' fun h m act
137 withHandle fun h@(DuplexHandle _ m _) act = withHandle' fun h m act
138
139 withHandle' :: String -> Handle -> MVar Handle__
140 -> (Handle__ -> IO (Handle__,a)) -> IO a
141 withHandle' fun h m act =
142 block $ do
143 h_ <- takeMVar m
144 checkBufferInvariants h_
145 (h',v) <- catchException (act h_)
146 (\ err -> putMVar m h_ >>
147 case err of
148 IOException ex -> ioError (augmentIOError ex fun h)
149 _ -> throw err)
150 checkBufferInvariants h'
151 putMVar m h'
152 return v
153
154 {-# INLINE withHandle_ #-}
155 withHandle_ :: String -> Handle -> (Handle__ -> IO a) -> IO a
156 withHandle_ fun h@(FileHandle _ m) act = withHandle_' fun h m act
157 withHandle_ fun h@(DuplexHandle _ m _) act = withHandle_' fun h m act
158
159 withHandle_' :: String -> Handle -> MVar Handle__ -> (Handle__ -> IO a) -> IO a
160 withHandle_' fun h m act =
161 block $ do
162 h_ <- takeMVar m
163 checkBufferInvariants h_
164 v <- catchException (act h_)
165 (\ err -> putMVar m h_ >>
166 case err of
167 IOException ex -> ioError (augmentIOError ex fun h)
168 _ -> throw err)
169 checkBufferInvariants h_
170 putMVar m h_
171 return v
172
173 withAllHandles__ :: String -> Handle -> (Handle__ -> IO Handle__) -> IO ()
174 withAllHandles__ fun h@(FileHandle _ m) act = withHandle__' fun h m act
175 withAllHandles__ fun h@(DuplexHandle _ r w) act = do
176 withHandle__' fun h r act
177 withHandle__' fun h w act
178
179 withHandle__' fun h m act =
180 block $ do
181 h_ <- takeMVar m
182 checkBufferInvariants h_
183 h' <- catchException (act h_)
184 (\ err -> putMVar m h_ >>
185 case err of
186 IOException ex -> ioError (augmentIOError ex fun h)
187 _ -> throw err)
188 checkBufferInvariants h'
189 putMVar m h'
190 return ()
191
192 augmentIOError (IOError _ iot _ str fp) fun h
193 = IOError (Just h) iot fun str filepath
194 where filepath
195 | Just _ <- fp = fp
196 | otherwise = case h of
197 FileHandle fp _ -> Just fp
198 DuplexHandle fp _ _ -> Just fp
199
200 -- ---------------------------------------------------------------------------
201 -- Wrapper for write operations.
202
203 wantWritableHandle :: String -> Handle -> (Handle__ -> IO a) -> IO a
204 wantWritableHandle fun h@(FileHandle _ m) act
205 = wantWritableHandle' fun h m act
206 wantWritableHandle fun h@(DuplexHandle _ _ m) act
207 = wantWritableHandle' fun h m act
208 -- ToDo: in the Duplex case, we don't need to checkWritableHandle
209
210 wantWritableHandle'
211 :: String -> Handle -> MVar Handle__
212 -> (Handle__ -> IO a) -> IO a
213 wantWritableHandle' fun h m act
214 = withHandle_' fun h m (checkWritableHandle act)
215
216 checkWritableHandle act handle_
217 = case haType handle_ of
218 ClosedHandle -> ioe_closedHandle
219 SemiClosedHandle -> ioe_closedHandle
220 ReadHandle -> ioe_notWritable
221 ReadWriteHandle -> do
222 let ref = haBuffer handle_
223 buf <- readIORef ref
224 new_buf <-
225 if not (bufferIsWritable buf)
226 then do b <- flushReadBuffer (haFD handle_) buf
227 return b{ bufState=WriteBuffer }
228 else return buf
229 writeIORef ref new_buf
230 act handle_
231 _other -> act handle_
232
233 -- ---------------------------------------------------------------------------
234 -- Wrapper for read operations.
235
236 wantReadableHandle :: String -> Handle -> (Handle__ -> IO a) -> IO a
237 wantReadableHandle fun h@(FileHandle _ m) act
238 = wantReadableHandle' fun h m act
239 wantReadableHandle fun h@(DuplexHandle _ m _) act
240 = wantReadableHandle' fun h m act
241 -- ToDo: in the Duplex case, we don't need to checkReadableHandle
242
243 wantReadableHandle'
244 :: String -> Handle -> MVar Handle__
245 -> (Handle__ -> IO a) -> IO a
246 wantReadableHandle' fun h m act
247 = withHandle_' fun h m (checkReadableHandle act)
248
249 checkReadableHandle act handle_ =
250 case haType handle_ of
251 ClosedHandle -> ioe_closedHandle
252 SemiClosedHandle -> ioe_closedHandle
253 AppendHandle -> ioe_notReadable
254 WriteHandle -> ioe_notReadable
255 ReadWriteHandle -> do
256 let ref = haBuffer handle_
257 buf <- readIORef ref
258 when (bufferIsWritable buf) $ do
259 new_buf <- flushWriteBuffer (haFD handle_) (haIsStream handle_) buf
260 writeIORef ref new_buf{ bufState=ReadBuffer }
261 act handle_
262 _other -> act handle_
263
264 -- ---------------------------------------------------------------------------
265 -- Wrapper for seek operations.
266
267 wantSeekableHandle :: String -> Handle -> (Handle__ -> IO a) -> IO a
268 wantSeekableHandle fun h@(DuplexHandle _ _ _) _act =
269 ioException (IOError (Just h) IllegalOperation fun
270 "handle is not seekable" Nothing)
271 wantSeekableHandle fun h@(FileHandle _ m) act =
272 withHandle_' fun h m (checkSeekableHandle act)
273
274 checkSeekableHandle act handle_ =
275 case haType handle_ of
276 ClosedHandle -> ioe_closedHandle
277 SemiClosedHandle -> ioe_closedHandle
278 AppendHandle -> ioe_notSeekable
279 _ | haIsBin handle_ || tEXT_MODE_SEEK_ALLOWED -> act handle_
280 | otherwise -> ioe_notSeekable_notBin
281
282 -- -----------------------------------------------------------------------------
283 -- Handy IOErrors
284
285 ioe_closedHandle, ioe_EOF,
286 ioe_notReadable, ioe_notWritable,
287 ioe_notSeekable, ioe_notSeekable_notBin :: IO a
288
289 ioe_closedHandle = ioException
290 (IOError Nothing IllegalOperation ""
291 "handle is closed" Nothing)
292 ioe_EOF = ioException
293 (IOError Nothing EOF "" "" Nothing)
294 ioe_notReadable = ioException
295 (IOError Nothing IllegalOperation ""
296 "handle is not open for reading" Nothing)
297 ioe_notWritable = ioException
298 (IOError Nothing IllegalOperation ""
299 "handle is not open for writing" Nothing)
300 ioe_notSeekable = ioException
301 (IOError Nothing IllegalOperation ""
302 "handle is not seekable" Nothing)
303 ioe_notSeekable_notBin = ioException
304 (IOError Nothing IllegalOperation ""
305 "seek operations on text-mode handles are not allowed on this platform"
306 Nothing)
307
308 ioe_finalizedHandle fp = throw (IOException
309 (IOError Nothing IllegalOperation ""
310 "handle is finalized" (Just fp)))
311
312 ioe_bufsiz :: Int -> IO a
313 ioe_bufsiz n = ioException
314 (IOError Nothing InvalidArgument "hSetBuffering"
315 ("illegal buffer size " ++ showsPrec 9 n []) Nothing)
316 -- 9 => should be parens'ified.
317
318 -- -----------------------------------------------------------------------------
319 -- Handle Finalizers
320
321 -- For a duplex handle, we arrange that the read side points to the write side
322 -- (and hence keeps it alive if the read side is alive). This is done by
323 -- having the haOtherSide field of the read side point to the read side.
324 -- The finalizer is then placed on the write side, and the handle only gets
325 -- finalized once, when both sides are no longer required.
326
327 -- NOTE about finalized handles: It's possible that a handle can be
328 -- finalized and then we try to use it later, for example if the
329 -- handle is referenced from another finalizer, or from a thread that
330 -- has become unreferenced and then resurrected (arguably in the
331 -- latter case we shouldn't finalize the Handle...). Anyway,
332 -- we try to emit a helpful message which is better than nothing.
333
334 stdHandleFinalizer :: FilePath -> MVar Handle__ -> IO ()
335 stdHandleFinalizer fp m = do
336 h_ <- takeMVar m
337 flushWriteBufferOnly h_
338 putMVar m (ioe_finalizedHandle fp)
339
340 handleFinalizer :: FilePath -> MVar Handle__ -> IO ()
341 handleFinalizer fp m = do
342 handle_ <- takeMVar m
343 case haType handle_ of
344 ClosedHandle -> return ()
345 _ -> do flushWriteBufferOnly handle_ `catchException` \_ -> return ()
346 -- ignore errors and async exceptions, and close the
347 -- descriptor anyway...
348 hClose_handle_ handle_
349 return ()
350 putMVar m (ioe_finalizedHandle fp)
351
352 -- ---------------------------------------------------------------------------
353 -- Grimy buffer operations
354
355 #ifdef DEBUG
356 checkBufferInvariants h_ = do
357 let ref = haBuffer h_
358 Buffer{ bufWPtr=w, bufRPtr=r, bufSize=size, bufState=state } <- readIORef ref
359 if not (
360 size > 0
361 && r <= w
362 && w <= size
363 && ( r /= w || (r == 0 && w == 0) )
364 && ( state /= WriteBuffer || r == 0 )
365 && ( state /= WriteBuffer || w < size ) -- write buffer is never full
366 )
367 then error "buffer invariant violation"
368 else return ()
369 #else
370 checkBufferInvariants h_ = return ()
371 #endif
372
373 newEmptyBuffer :: RawBuffer -> BufferState -> Int -> Buffer
374 newEmptyBuffer b state size
375 = Buffer{ bufBuf=b, bufRPtr=0, bufWPtr=0, bufSize=size, bufState=state }
376
377 allocateBuffer :: Int -> BufferState -> IO Buffer
378 allocateBuffer sz@(I# size) state = IO $ \s ->
379 -- We sometimes need to pass the address of this buffer to
380 -- a "safe" foreign call, hence it must be immovable.
381 case newPinnedByteArray# size s of { (# s, b #) ->
382 (# s, newEmptyBuffer b state sz #) }
383
384 writeCharIntoBuffer :: RawBuffer -> Int -> Char -> IO Int
385 writeCharIntoBuffer slab (I# off) (C# c)
386 = IO $ \s -> case writeCharArray# slab off c s of
387 s -> (# s, I# (off +# 1#) #)
388
389 readCharFromBuffer :: RawBuffer -> Int -> IO (Char, Int)
390 readCharFromBuffer slab (I# off)
391 = IO $ \s -> case readCharArray# slab off s of
392 (# s, c #) -> (# s, (C# c, I# (off +# 1#)) #)
393
394 getBuffer :: FD -> BufferState -> IO (IORef Buffer, BufferMode)
395 getBuffer fd state = do
396 buffer <- allocateBuffer dEFAULT_BUFFER_SIZE state
397 ioref <- newIORef buffer
398 is_tty <- fdIsTTY fd
399
400 let buffer_mode
401 | is_tty = LineBuffering
402 | otherwise = BlockBuffering Nothing
403
404 return (ioref, buffer_mode)
405
406 mkUnBuffer :: IO (IORef Buffer)
407 mkUnBuffer = do
408 buffer <- allocateBuffer 1 ReadBuffer
409 newIORef buffer
410
411 -- flushWriteBufferOnly flushes the buffer iff it contains pending write data.
412 flushWriteBufferOnly :: Handle__ -> IO ()
413 flushWriteBufferOnly h_ = do
414 let fd = haFD h_
415 ref = haBuffer h_
416 buf <- readIORef ref
417 new_buf <- if bufferIsWritable buf
418 then flushWriteBuffer fd (haIsStream h_) buf
419 else return buf
420 writeIORef ref new_buf
421
422 -- flushBuffer syncs the file with the buffer, including moving the
423 -- file pointer backwards in the case of a read buffer.
424 flushBuffer :: Handle__ -> IO ()
425 flushBuffer h_ = do
426 let ref = haBuffer h_
427 buf <- readIORef ref
428
429 flushed_buf <-
430 case bufState buf of
431 ReadBuffer -> flushReadBuffer (haFD h_) buf
432 WriteBuffer -> flushWriteBuffer (haFD h_) (haIsStream h_) buf
433
434 writeIORef ref flushed_buf
435
436 -- When flushing a read buffer, we seek backwards by the number of
437 -- characters in the buffer. The file descriptor must therefore be
438 -- seekable: attempting to flush the read buffer on an unseekable
439 -- handle is not allowed.
440
441 flushReadBuffer :: FD -> Buffer -> IO Buffer
442 flushReadBuffer fd buf
443 | bufferEmpty buf = return buf
444 | otherwise = do
445 let off = negate (bufWPtr buf - bufRPtr buf)
446 # ifdef DEBUG_DUMP
447 puts ("flushReadBuffer: new file offset = " ++ show off ++ "\n")
448 # endif
449 throwErrnoIfMinus1Retry "flushReadBuffer"
450 (c_lseek fd (fromIntegral off) sEEK_CUR)
451 return buf{ bufWPtr=0, bufRPtr=0 }
452
453 flushWriteBuffer :: FD -> Bool -> Buffer -> IO Buffer
454 flushWriteBuffer fd is_stream buf@Buffer{ bufBuf=b, bufRPtr=r, bufWPtr=w } =
455 seq fd $ do -- strictness hack
456 let bytes = w - r
457 #ifdef DEBUG_DUMP
458 puts ("flushWriteBuffer, fd=" ++ show fd ++ ", bytes=" ++ show bytes ++ "\n")
459 #endif
460 if bytes == 0
461 then return (buf{ bufRPtr=0, bufWPtr=0 })
462 else do
463 res <- writeRawBuffer "flushWriteBuffer" fd is_stream b
464 (fromIntegral r) (fromIntegral bytes)
465 let res' = fromIntegral res
466 if res' < bytes
467 then flushWriteBuffer fd is_stream (buf{ bufRPtr = r + res' })
468 else return buf{ bufRPtr=0, bufWPtr=0 }
469
470 fillReadBuffer :: FD -> Bool -> Bool -> Buffer -> IO Buffer
471 fillReadBuffer fd is_line is_stream
472 buf@Buffer{ bufBuf=b, bufRPtr=r, bufWPtr=w, bufSize=size } =
473 -- buffer better be empty:
474 assert (r == 0 && w == 0) $ do
475 fillReadBufferLoop fd is_line is_stream buf b w size
476
477 -- For a line buffer, we just get the first chunk of data to arrive,
478 -- and don't wait for the whole buffer to be full (but we *do* wait
479 -- until some data arrives). This isn't really line buffering, but it
480 -- appears to be what GHC has done for a long time, and I suspect it
481 -- is more useful than line buffering in most cases.
482
483 fillReadBufferLoop fd is_line is_stream buf b w size = do
484 let bytes = size - w
485 if bytes == 0 -- buffer full?
486 then return buf{ bufRPtr=0, bufWPtr=w }
487 else do
488 #ifdef DEBUG_DUMP
489 puts ("fillReadBufferLoop: bytes = " ++ show bytes ++ "\n")
490 #endif
491 res <- readRawBuffer "fillReadBuffer" fd is_stream b
492 (fromIntegral w) (fromIntegral bytes)
493 let res' = fromIntegral res
494 #ifdef DEBUG_DUMP
495 puts ("fillReadBufferLoop: res' = " ++ show res' ++ "\n")
496 #endif
497 if res' == 0
498 then if w == 0
499 then ioe_EOF
500 else return buf{ bufRPtr=0, bufWPtr=w }
501 else if res' < bytes && not is_line
502 then fillReadBufferLoop fd is_line is_stream buf b (w+res') size
503 else return buf{ bufRPtr=0, bufWPtr=w+res' }
504
505
506 fillReadBufferWithoutBlocking :: FD -> Bool -> Buffer -> IO Buffer
507 fillReadBufferWithoutBlocking fd is_stream
508 buf@Buffer{ bufBuf=b, bufRPtr=r, bufWPtr=w, bufSize=size } =
509 -- buffer better be empty:
510 assert (r == 0 && w == 0) $ do
511 #ifdef DEBUG_DUMP
512 puts ("fillReadBufferLoopNoBlock: bytes = " ++ show size ++ "\n")
513 #endif
514 res <- readRawBufferNoBlock "fillReadBuffer" fd is_stream b
515 0 (fromIntegral size)
516 let res' = fromIntegral res
517 #ifdef DEBUG_DUMP
518 puts ("fillReadBufferLoopNoBlock: res' = " ++ show res' ++ "\n")
519 #endif
520 return buf{ bufRPtr=0, bufWPtr=res' }
521
522 -- Low level routines for reading/writing to (raw)buffers:
523
524 #ifndef mingw32_HOST_OS
525
526 {-
527 NOTE [nonblock]:
528
529 Unix has broken semantics when it comes to non-blocking I/O: you can
530 set the O_NONBLOCK flag on an FD, but it applies to the all other FDs
531 attached to the same underlying file, pipe or TTY; there's no way to
532 have private non-blocking behaviour for an FD. See bug #724.
533
534 We fix this by only setting O_NONBLOCK on FDs that we create; FDs that
535 come from external sources or are exposed externally are left in
536 blocking mode. This solution has some problems though. We can't
537 completely simulate a non-blocking read without O_NONBLOCK: several
538 cases are wrong here. The cases that are wrong:
539
540 * reading/writing to a blocking FD in non-threaded mode.
541 In threaded mode, we just make a safe call to read().
542 In non-threaded mode we call select() before attempting to read,
543 but that leaves a small race window where the data can be read
544 from the file descriptor before we issue our blocking read().
545 * readRawBufferNoBlock for a blocking FD
546 -}
547
548 readRawBuffer :: String -> FD -> Bool -> RawBuffer -> Int -> CInt -> IO CInt
549 readRawBuffer loc fd is_nonblock buf off len
550 | is_nonblock = unsafe_read
551 | threaded = safe_read
552 | otherwise = do r <- throwErrnoIfMinus1 loc
553 (fdReady (fromIntegral fd) 0 0 False)
554 if r /= 0
555 then unsafe_read
556 else do threadWaitRead (fromIntegral fd); unsafe_read
557 where
558 do_read call = throwErrnoIfMinus1RetryMayBlock loc call
559 (threadWaitRead (fromIntegral fd))
560 unsafe_read = do_read (read_rawBuffer fd buf off len)
561 safe_read = do_read (safe_read_rawBuffer fd buf off len)
562
563 readRawBufferPtr :: String -> FD -> Bool -> Ptr CChar -> Int -> CInt -> IO CInt
564 readRawBufferPtr loc fd is_nonblock buf off len
565 | is_nonblock = unsafe_read
566 | threaded = safe_read
567 | otherwise = do r <- throwErrnoIfMinus1 loc
568 (fdReady (fromIntegral fd) 0 0 False)
569 if r /= 0
570 then unsafe_read
571 else do threadWaitRead (fromIntegral fd); unsafe_read
572 where
573 do_read call = throwErrnoIfMinus1RetryMayBlock loc call
574 (threadWaitRead (fromIntegral fd))
575 unsafe_read = do_read (read_off fd buf off len)
576 safe_read = do_read (safe_read_off fd buf off len)
577
578 readRawBufferNoBlock :: String -> FD -> Bool -> RawBuffer -> Int -> CInt -> IO CInt
579 readRawBufferNoBlock loc fd is_nonblock buf off len
580 | is_nonblock = unsafe_read
581 | otherwise = do r <- fdReady (fromIntegral fd) 0 0 False
582 if r /= 0 then safe_read
583 else return 0
584 -- XXX see note [nonblock]
585 where
586 do_read call = throwErrnoIfMinus1RetryOnBlock loc call (return 0)
587 unsafe_read = do_read (read_rawBuffer fd buf off len)
588 safe_read = do_read (safe_read_rawBuffer fd buf off len)
589
590 writeRawBuffer :: String -> FD -> Bool -> RawBuffer -> Int -> CInt -> IO CInt
591 writeRawBuffer loc fd is_nonblock buf off len
592 | is_nonblock = unsafe_write
593 | threaded = safe_write
594 | otherwise = do r <- fdReady (fromIntegral fd) 1 0 False
595 if r /= 0
596 then safe_write
597 else do threadWaitWrite (fromIntegral fd); unsafe_write
598 where
599 do_write call = throwErrnoIfMinus1RetryMayBlock loc call
600 (threadWaitWrite (fromIntegral fd))
601 unsafe_write = do_write (write_rawBuffer fd buf off len)
602 safe_write = do_write (safe_write_rawBuffer (fromIntegral fd) buf off len)
603
604 writeRawBufferPtr :: String -> FD -> Bool -> Ptr CChar -> Int -> CInt -> IO CInt
605 writeRawBufferPtr loc fd is_nonblock buf off len
606 | is_nonblock = unsafe_write
607 | threaded = safe_write
608 | otherwise = do r <- fdReady (fromIntegral fd) 1 0 False
609 if r /= 0
610 then safe_write
611 else do threadWaitWrite (fromIntegral fd); unsafe_write
612 where
613 do_write call = throwErrnoIfMinus1RetryMayBlock loc call
614 (threadWaitWrite (fromIntegral fd))
615 unsafe_write = do_write (write_off fd buf off len)
616 safe_write = do_write (safe_write_off (fromIntegral fd) buf off len)
617
618 foreign import ccall unsafe "__hscore_PrelHandle_read"
619 read_rawBuffer :: CInt -> RawBuffer -> Int -> CInt -> IO CInt
620
621 foreign import ccall unsafe "__hscore_PrelHandle_read"
622 read_off :: CInt -> Ptr CChar -> Int -> CInt -> IO CInt
623
624 foreign import ccall unsafe "__hscore_PrelHandle_write"
625 write_rawBuffer :: CInt -> RawBuffer -> Int -> CInt -> IO CInt
626
627 foreign import ccall unsafe "__hscore_PrelHandle_write"
628 write_off :: CInt -> Ptr CChar -> Int -> CInt -> IO CInt
629
630 foreign import ccall safe "fdReady"
631 fdReady :: CInt -> CInt -> CInt -> Bool -> IO CInt
632
633 #else /* mingw32_HOST_OS.... */
634
635 readRawBuffer :: String -> FD -> Bool -> RawBuffer -> Int -> CInt -> IO CInt
636 readRawBuffer loc fd is_stream buf off len
637 | threaded = blockingReadRawBuffer loc fd is_stream buf off len
638 | otherwise = asyncReadRawBuffer loc fd is_stream buf off len
639
640 readRawBufferPtr :: String -> FD -> Bool -> Ptr CChar -> Int -> CInt -> IO CInt
641 readRawBufferPtr loc fd is_stream buf off len
642 | threaded = blockingReadRawBufferPtr loc fd is_stream buf off len
643 | otherwise = asyncReadRawBufferPtr loc fd is_stream buf off len
644
645 writeRawBuffer :: String -> FD -> Bool -> RawBuffer -> Int -> CInt -> IO CInt
646 writeRawBuffer loc fd is_stream buf off len
647 | threaded = blockingWriteRawBuffer loc fd is_stream buf off len
648 | otherwise = asyncWriteRawBuffer loc fd is_stream buf off len
649
650 writeRawBufferPtr :: String -> FD -> Bool -> Ptr CChar -> Int -> CInt -> IO CInt
651 writeRawBufferPtr loc fd is_stream buf off len
652 | threaded = blockingWriteRawBufferPtr loc fd is_stream buf off len
653 | otherwise = asyncWriteRawBufferPtr loc fd is_stream buf off len
654
655 -- ToDo: we don't have a non-blocking primitve read on Win32
656 readRawBufferNoBlock :: String -> FD -> Bool -> RawBuffer -> Int -> CInt -> IO CInt
657 readRawBufferNoBlock = readRawBuffer
658
659 -- Async versions of the read/write primitives, for the non-threaded RTS
660
661 asyncReadRawBuffer loc fd is_stream buf off len = do
662 (l, rc) <- asyncReadBA (fromIntegral fd) (if is_stream then 1 else 0)
663 (fromIntegral len) off buf
664 if l == (-1)
665 then
666 ioError (errnoToIOError loc (Errno (fromIntegral rc)) Nothing Nothing)
667 else return (fromIntegral l)
668
669 asyncReadRawBufferPtr loc fd is_stream buf off len = do
670 (l, rc) <- asyncRead (fromIntegral fd) (if is_stream then 1 else 0)
671 (fromIntegral len) (buf `plusPtr` off)
672 if l == (-1)
673 then
674 ioError (errnoToIOError loc (Errno (fromIntegral rc)) Nothing Nothing)
675 else return (fromIntegral l)
676
677 asyncWriteRawBuffer loc fd is_stream buf off len = do
678 (l, rc) <- asyncWriteBA (fromIntegral fd) (if is_stream then 1 else 0)
679 (fromIntegral len) off buf
680 if l == (-1)
681 then
682 ioError (errnoToIOError loc (Errno (fromIntegral rc)) Nothing Nothing)
683 else return (fromIntegral l)
684
685 asyncWriteRawBufferPtr loc fd is_stream buf off len = do
686 (l, rc) <- asyncWrite (fromIntegral fd) (if is_stream then 1 else 0)
687 (fromIntegral len) (buf `plusPtr` off)
688 if l == (-1)
689 then
690 ioError (errnoToIOError loc (Errno (fromIntegral rc)) Nothing Nothing)
691 else return (fromIntegral l)
692
693 -- Blocking versions of the read/write primitives, for the threaded RTS
694
695 blockingReadRawBuffer loc fd True buf off len =
696 throwErrnoIfMinus1Retry loc $
697 safe_recv_rawBuffer fd buf off len
698 blockingReadRawBuffer loc fd False buf off len =
699 throwErrnoIfMinus1Retry loc $
700 safe_read_rawBuffer fd buf off len
701
702 blockingReadRawBufferPtr loc fd True buf off len =
703 throwErrnoIfMinus1Retry loc $
704 safe_recv_off fd buf off len
705 blockingReadRawBufferPtr loc fd False buf off len =
706 throwErrnoIfMinus1Retry loc $
707 safe_read_off fd buf off len
708
709 blockingWriteRawBuffer loc fd True buf off len =
710 throwErrnoIfMinus1Retry loc $
711 safe_send_rawBuffer fd buf off len
712 blockingWriteRawBuffer loc fd False buf off len =
713 throwErrnoIfMinus1Retry loc $
714 safe_write_rawBuffer fd buf off len
715
716 blockingWriteRawBufferPtr loc fd True buf off len =
717 throwErrnoIfMinus1Retry loc $
718 safe_send_off fd buf off len
719 blockingWriteRawBufferPtr loc fd False buf off len =
720 throwErrnoIfMinus1Retry loc $
721 safe_write_off fd buf off len
722
723 -- NOTE: "safe" versions of the read/write calls for use by the threaded RTS.
724 -- These calls may block, but that's ok.
725
726 foreign import ccall safe "__hscore_PrelHandle_recv"
727 safe_recv_rawBuffer :: CInt -> RawBuffer -> Int -> CInt -> IO CInt
728
729 foreign import ccall safe "__hscore_PrelHandle_recv"
730 safe_recv_off :: CInt -> Ptr CChar -> Int -> CInt -> IO CInt
731
732 foreign import ccall safe "__hscore_PrelHandle_send"
733 safe_send_rawBuffer :: CInt -> RawBuffer -> Int -> CInt -> IO CInt
734
735 foreign import ccall safe "__hscore_PrelHandle_send"
736 safe_send_off :: CInt -> Ptr CChar -> Int -> CInt -> IO CInt
737
738 #endif
739
740 foreign import ccall "rtsSupportsBoundThreads" threaded :: Bool
741
742 foreign import ccall safe "__hscore_PrelHandle_read"
743 safe_read_rawBuffer :: FD -> RawBuffer -> Int -> CInt -> IO CInt
744
745 foreign import ccall safe "__hscore_PrelHandle_read"
746 safe_read_off :: FD -> Ptr CChar -> Int -> CInt -> IO CInt
747
748 foreign import ccall safe "__hscore_PrelHandle_write"
749 safe_write_rawBuffer :: CInt -> RawBuffer -> Int -> CInt -> IO CInt
750
751 foreign import ccall safe "__hscore_PrelHandle_write"
752 safe_write_off :: CInt -> Ptr CChar -> Int -> CInt -> IO CInt
753
754 -- ---------------------------------------------------------------------------
755 -- Standard Handles
756
757 -- Three handles are allocated during program initialisation. The first
758 -- two manage input or output from the Haskell program's standard input
759 -- or output channel respectively. The third manages output to the
760 -- standard error channel. These handles are initially open.
761
762 fd_stdin = 0 :: FD
763 fd_stdout = 1 :: FD
764 fd_stderr = 2 :: FD
765
766 -- | A handle managing input from the Haskell program's standard input channel.
767 stdin :: Handle
768 stdin = unsafePerformIO $ do
769 -- ToDo: acquire lock
770 -- We don't set non-blocking mode on standard handles, because it may
771 -- confuse other applications attached to the same TTY/pipe
772 -- see Note [nonblock]
773 (buf, bmode) <- getBuffer fd_stdin ReadBuffer
774 mkStdHandle fd_stdin "<stdin>" ReadHandle buf bmode
775
776 -- | A handle managing output to the Haskell program's standard output channel.
777 stdout :: Handle
778 stdout = unsafePerformIO $ do
779 -- ToDo: acquire lock
780 -- We don't set non-blocking mode on standard handles, because it may
781 -- confuse other applications attached to the same TTY/pipe
782 -- see Note [nonblock]
783 (buf, bmode) <- getBuffer fd_stdout WriteBuffer
784 mkStdHandle fd_stdout "<stdout>" WriteHandle buf bmode
785
786 -- | A handle managing output to the Haskell program's standard error channel.
787 stderr :: Handle
788 stderr = unsafePerformIO $ do
789 -- ToDo: acquire lock
790 -- We don't set non-blocking mode on standard handles, because it may
791 -- confuse other applications attached to the same TTY/pipe
792 -- see Note [nonblock]
793 buf <- mkUnBuffer
794 mkStdHandle fd_stderr "<stderr>" WriteHandle buf NoBuffering
795
796 -- ---------------------------------------------------------------------------
797 -- Opening and Closing Files
798
799 addFilePathToIOError fun fp (IOError h iot _ str _)
800 = IOError h iot fun str (Just fp)
801
802 -- | Computation 'openFile' @file mode@ allocates and returns a new, open
803 -- handle to manage the file @file@. It manages input if @mode@
804 -- is 'ReadMode', output if @mode@ is 'WriteMode' or 'AppendMode',
805 -- and both input and output if mode is 'ReadWriteMode'.
806 --
807 -- If the file does not exist and it is opened for output, it should be
808 -- created as a new file. If @mode@ is 'WriteMode' and the file
809 -- already exists, then it should be truncated to zero length.
810 -- Some operating systems delete empty files, so there is no guarantee
811 -- that the file will exist following an 'openFile' with @mode@
812 -- 'WriteMode' unless it is subsequently written to successfully.
813 -- The handle is positioned at the end of the file if @mode@ is
814 -- 'AppendMode', and otherwise at the beginning (in which case its
815 -- internal position is 0).
816 -- The initial buffer mode is implementation-dependent.
817 --
818 -- This operation may fail with:
819 --
820 -- * 'isAlreadyInUseError' if the file is already open and cannot be reopened;
821 --
822 -- * 'isDoesNotExistError' if the file does not exist; or
823 --
824 -- * 'isPermissionError' if the user does not have permission to open the file.
825 --
826 -- Note: if you will be working with files containing binary data, you'll want to
827 -- be using 'openBinaryFile'.
828 openFile :: FilePath -> IOMode -> IO Handle
829 openFile fp im =
830 catch
831 (openFile' fp im dEFAULT_OPEN_IN_BINARY_MODE)
832 (\e -> ioError (addFilePathToIOError "openFile" fp e))
833
834 -- | Like 'openFile', but open the file in binary mode.
835 -- On Windows, reading a file in text mode (which is the default)
836 -- will translate CRLF to LF, and writing will translate LF to CRLF.
837 -- This is usually what you want with text files. With binary files
838 -- this is undesirable; also, as usual under Microsoft operating systems,
839 -- text mode treats control-Z as EOF. Binary mode turns off all special
840 -- treatment of end-of-line and end-of-file characters.
841 -- (See also 'hSetBinaryMode'.)
842
843 openBinaryFile :: FilePath -> IOMode -> IO Handle
844 openBinaryFile fp m =
845 catch
846 (openFile' fp m True)
847 (\e -> ioError (addFilePathToIOError "openBinaryFile" fp e))
848
849 openFile' filepath mode binary =
850 withCString filepath $ \ f ->
851
852 let
853 oflags1 = case mode of
854 ReadMode -> read_flags
855 #ifdef mingw32_HOST_OS
856 WriteMode -> write_flags .|. o_TRUNC
857 #else
858 WriteMode -> write_flags
859 #endif
860 ReadWriteMode -> rw_flags
861 AppendMode -> append_flags
862
863 binary_flags
864 | binary = o_BINARY
865 | otherwise = 0
866
867 oflags = oflags1 .|. binary_flags
868 in do
869
870 -- the old implementation had a complicated series of three opens,
871 -- which is perhaps because we have to be careful not to open
872 -- directories. However, the man pages I've read say that open()
873 -- always returns EISDIR if the file is a directory and was opened
874 -- for writing, so I think we're ok with a single open() here...
875 fd <- throwErrnoIfMinus1Retry "openFile"
876 (c_open f (fromIntegral oflags) 0o666)
877
878 fd_type <- fdType fd
879
880 h <- fdToHandle' fd (Just fd_type) False filepath mode binary
881 `catchException` \e -> do c_close fd; throw e
882 -- NB. don't forget to close the FD if fdToHandle' fails, otherwise
883 -- this FD leaks.
884 -- ASSERT: if we just created the file, then fdToHandle' won't fail
885 -- (so we don't need to worry about removing the newly created file
886 -- in the event of an error).
887
888 #ifndef mingw32_HOST_OS
889 -- we want to truncate() if this is an open in WriteMode, but only
890 -- if the target is a RegularFile. ftruncate() fails on special files
891 -- like /dev/null.
892 if mode == WriteMode && fd_type == RegularFile
893 then throwErrnoIf (/=0) "openFile"
894 (c_ftruncate fd 0)
895 else return 0
896 #endif
897 return h
898
899
900 std_flags = o_NONBLOCK .|. o_NOCTTY
901 output_flags = std_flags .|. o_CREAT
902 read_flags = std_flags .|. o_RDONLY
903 write_flags = output_flags .|. o_WRONLY
904 rw_flags = output_flags .|. o_RDWR
905 append_flags = write_flags .|. o_APPEND
906
907 -- ---------------------------------------------------------------------------
908 -- fdToHandle'
909
910 fdToHandle' :: FD -> Maybe FDType -> Bool -> FilePath -> IOMode -> Bool -> IO Handle
911 fdToHandle' fd mb_fd_type is_socket filepath mode binary = do
912 -- turn on non-blocking mode
913 setNonBlockingFD fd
914
915 #ifdef mingw32_HOST_OS
916 -- On Windows, the is_stream flag indicates that the Handle is a socket
917 let is_stream = is_socket
918 #else
919 -- On Unix, the is_stream flag indicates that the FD is non-blocking
920 let is_stream = True
921 #endif
922
923 let (ha_type, write) =
924 case mode of
925 ReadMode -> ( ReadHandle, False )
926 WriteMode -> ( WriteHandle, True )
927 ReadWriteMode -> ( ReadWriteHandle, True )
928 AppendMode -> ( AppendHandle, True )
929
930 -- open() won't tell us if it was a directory if we only opened for
931 -- reading, so check again.
932 fd_type <-
933 case mb_fd_type of
934 Just x -> return x
935 Nothing -> fdType fd
936
937 case fd_type of
938 Directory ->
939 ioException (IOError Nothing InappropriateType "openFile"
940 "is a directory" Nothing)
941
942 -- regular files need to be locked
943 RegularFile -> do
944 #ifndef mingw32_HOST_OS
945 r <- lockFile fd (fromBool write) 1{-exclusive-}
946 when (r == -1) $
947 ioException (IOError Nothing ResourceBusy "openFile"
948 "file is locked" Nothing)
949 #endif
950 mkFileHandle fd is_stream filepath ha_type binary
951
952 Stream
953 -- only *Streams* can be DuplexHandles. Other read/write
954 -- Handles must share a buffer.
955 | ReadWriteHandle <- ha_type ->
956 mkDuplexHandle fd is_stream filepath binary
957 | otherwise ->
958 mkFileHandle fd is_stream filepath ha_type binary
959
960 RawDevice ->
961 mkFileHandle fd is_stream filepath ha_type binary
962
963 fdToHandle :: FD -> IO Handle
964 fdToHandle fd = do
965 mode <- fdGetMode fd
966 let fd_str = "<file descriptor: " ++ show fd ++ ">"
967 fdToHandle' fd Nothing False{-XXX!-} fd_str mode True{-bin mode-}
968
969
970 #ifndef mingw32_HOST_OS
971 foreign import ccall unsafe "lockFile"
972 lockFile :: CInt -> CInt -> CInt -> IO CInt
973
974 foreign import ccall unsafe "unlockFile"
975 unlockFile :: CInt -> IO CInt
976 #endif
977
978 mkStdHandle :: FD -> FilePath -> HandleType -> IORef Buffer -> BufferMode
979 -> IO Handle
980 mkStdHandle fd filepath ha_type buf bmode = do
981 spares <- newIORef BufferListNil
982 newFileHandle filepath (stdHandleFinalizer filepath)
983 (Handle__ { haFD = fd,
984 haType = ha_type,
985 haIsBin = dEFAULT_OPEN_IN_BINARY_MODE,
986 haIsStream = False, -- means FD is blocking on Unix
987 haBufferMode = bmode,
988 haBuffer = buf,
989 haBuffers = spares,
990 haOtherSide = Nothing
991 })
992
993 mkFileHandle :: FD -> Bool -> FilePath -> HandleType -> Bool -> IO Handle
994 mkFileHandle fd is_stream filepath ha_type binary = do
995 (buf, bmode) <- getBuffer fd (initBufferState ha_type)
996
997 #ifdef mingw32_HOST_OS
998 -- On Windows, if this is a read/write handle and we are in text mode,
999 -- turn off buffering. We don't correctly handle the case of switching
1000 -- from read mode to write mode on a buffered text-mode handle, see bug
1001 -- \#679.
1002 bmode <- case ha_type of
1003 ReadWriteHandle | not binary -> return NoBuffering
1004 _other -> return bmode
1005 #endif
1006
1007 spares <- newIORef BufferListNil
1008 newFileHandle filepath (handleFinalizer filepath)
1009 (Handle__ { haFD = fd,
1010 haType = ha_type,
1011 haIsBin = binary,
1012 haIsStream = is_stream,
1013 haBufferMode = bmode,
1014 haBuffer = buf,
1015 haBuffers = spares,
1016 haOtherSide = Nothing
1017 })
1018
1019 mkDuplexHandle :: FD -> Bool -> FilePath -> Bool -> IO Handle
1020 mkDuplexHandle fd is_stream filepath binary = do
1021 (w_buf, w_bmode) <- getBuffer fd WriteBuffer
1022 w_spares <- newIORef BufferListNil
1023 let w_handle_ =
1024 Handle__ { haFD = fd,
1025 haType = WriteHandle,
1026 haIsBin = binary,
1027 haIsStream = is_stream,
1028 haBufferMode = w_bmode,
1029 haBuffer = w_buf,
1030 haBuffers = w_spares,
1031 haOtherSide = Nothing
1032 }
1033 write_side <- newMVar w_handle_
1034
1035 (r_buf, r_bmode) <- getBuffer fd ReadBuffer
1036 r_spares <- newIORef BufferListNil
1037 let r_handle_ =
1038 Handle__ { haFD = fd,
1039 haType = ReadHandle,
1040 haIsBin = binary,
1041 haIsStream = is_stream,
1042 haBufferMode = r_bmode,
1043 haBuffer = r_buf,
1044 haBuffers = r_spares,
1045 haOtherSide = Just write_side
1046 }
1047 read_side <- newMVar r_handle_
1048
1049 addMVarFinalizer write_side (handleFinalizer filepath write_side)
1050 return (DuplexHandle filepath read_side write_side)
1051
1052
1053 initBufferState ReadHandle = ReadBuffer
1054 initBufferState _ = WriteBuffer
1055
1056 -- ---------------------------------------------------------------------------
1057 -- Closing a handle
1058
1059 -- | Computation 'hClose' @hdl@ makes handle @hdl@ closed. Before the
1060 -- computation finishes, if @hdl@ is writable its buffer is flushed as
1061 -- for 'hFlush'.
1062 -- Performing 'hClose' on a handle that has already been closed has no effect;
1063 -- doing so not an error. All other operations on a closed handle will fail.
1064 -- If 'hClose' fails for any reason, any further operations (apart from
1065 -- 'hClose') on the handle will still fail as if @hdl@ had been successfully
1066 -- closed.
1067
1068 hClose :: Handle -> IO ()
1069 hClose h@(FileHandle _ m) = hClose' h m
1070 hClose h@(DuplexHandle _ r w) = hClose' h w >> hClose' h r
1071
1072 hClose' h m = withHandle__' "hClose" h m $ hClose_help
1073
1074 -- hClose_help is also called by lazyRead (in PrelIO) when EOF is read
1075 -- or an IO error occurs on a lazy stream. The semi-closed Handle is
1076 -- then closed immediately. We have to be careful with DuplexHandles
1077 -- though: we have to leave the closing to the finalizer in that case,
1078 -- because the write side may still be in use.
1079 hClose_help :: Handle__ -> IO Handle__
1080 hClose_help handle_ =
1081 case haType handle_ of
1082 ClosedHandle -> return handle_
1083 _ -> do flushWriteBufferOnly handle_ -- interruptible
1084 hClose_handle_ handle_
1085
1086 hClose_handle_ handle_ = do
1087 let fd = haFD handle_
1088
1089 -- close the file descriptor, but not when this is the read
1090 -- side of a duplex handle.
1091 case haOtherSide handle_ of
1092 Nothing ->
1093 throwErrnoIfMinus1Retry_ "hClose"
1094 #ifdef mingw32_HOST_OS
1095 (closeFd (haIsStream handle_) fd)
1096 #else
1097 (c_close fd)
1098 #endif
1099 Just _ -> return ()
1100
1101 -- free the spare buffers
1102 writeIORef (haBuffers handle_) BufferListNil
1103 writeIORef (haBuffer handle_) noBuffer
1104
1105 #ifndef mingw32_HOST_OS
1106 -- unlock it
1107 unlockFile fd
1108 #endif
1109
1110 -- we must set the fd to -1, because the finalizer is going
1111 -- to run eventually and try to close/unlock it.
1112 return (handle_{ haFD = -1,
1113 haType = ClosedHandle
1114 })
1115
1116 {-# NOINLINE noBuffer #-}
1117 noBuffer = unsafePerformIO $ allocateBuffer 1 ReadBuffer
1118
1119 -----------------------------------------------------------------------------
1120 -- Detecting and changing the size of a file
1121
1122 -- | For a handle @hdl@ which attached to a physical file,
1123 -- 'hFileSize' @hdl@ returns the size of that file in 8-bit bytes.
1124
1125 hFileSize :: Handle -> IO Integer
1126 hFileSize handle =
1127 withHandle_ "hFileSize" handle $ \ handle_ -> do
1128 case haType handle_ of
1129 ClosedHandle -> ioe_closedHandle
1130 SemiClosedHandle -> ioe_closedHandle
1131 _ -> do flushWriteBufferOnly handle_
1132 r <- fdFileSize (haFD handle_)
1133 if r /= -1
1134 then return r
1135 else ioException (IOError Nothing InappropriateType "hFileSize"
1136 "not a regular file" Nothing)
1137
1138
1139 -- | 'hSetFileSize' @hdl@ @size@ truncates the physical file with handle @hdl@ to @size@ bytes.
1140
1141 hSetFileSize :: Handle -> Integer -> IO ()
1142 hSetFileSize handle size =
1143 withHandle_ "hSetFileSize" handle $ \ handle_ -> do
1144 case haType handle_ of
1145 ClosedHandle -> ioe_closedHandle
1146 SemiClosedHandle -> ioe_closedHandle
1147 _ -> do flushWriteBufferOnly handle_
1148 throwErrnoIf (/=0) "hSetFileSize"
1149 (c_ftruncate (haFD handle_) (fromIntegral size))
1150 return ()
1151
1152 -- ---------------------------------------------------------------------------
1153 -- Detecting the End of Input
1154
1155 -- | For a readable handle @hdl@, 'hIsEOF' @hdl@ returns
1156 -- 'True' if no further input can be taken from @hdl@ or for a
1157 -- physical file, if the current I\/O position is equal to the length of
1158 -- the file. Otherwise, it returns 'False'.
1159
1160 hIsEOF :: Handle -> IO Bool
1161 hIsEOF handle =
1162 catch
1163 (do hLookAhead handle; return False)
1164 (\e -> if isEOFError e then return True else ioError e)
1165
1166 -- | The computation 'isEOF' is identical to 'hIsEOF',
1167 -- except that it works only on 'stdin'.
1168
1169 isEOF :: IO Bool
1170 isEOF = hIsEOF stdin
1171
1172 -- ---------------------------------------------------------------------------
1173 -- Looking ahead
1174
1175 -- | Computation 'hLookAhead' returns the next character from the handle
1176 -- without removing it from the input buffer, blocking until a character
1177 -- is available.
1178 --
1179 -- This operation may fail with:
1180 --
1181 -- * 'isEOFError' if the end of file has been reached.
1182
1183 hLookAhead :: Handle -> IO Char
1184 hLookAhead handle = do
1185 wantReadableHandle "hLookAhead" handle $ \handle_ -> do
1186 let ref = haBuffer handle_
1187 fd = haFD handle_
1188 is_line = haBufferMode handle_ == LineBuffering
1189 buf <- readIORef ref
1190
1191 -- fill up the read buffer if necessary
1192 new_buf <- if bufferEmpty buf
1193 then fillReadBuffer fd True (haIsStream handle_) buf
1194 else return buf
1195
1196 writeIORef ref new_buf
1197
1198 (c,_) <- readCharFromBuffer (bufBuf buf) (bufRPtr buf)
1199 return c
1200
1201 -- ---------------------------------------------------------------------------
1202 -- Buffering Operations
1203
1204 -- Three kinds of buffering are supported: line-buffering,
1205 -- block-buffering or no-buffering. See GHC.IOBase for definition and
1206 -- further explanation of what the type represent.
1207
1208 -- | Computation 'hSetBuffering' @hdl mode@ sets the mode of buffering for
1209 -- handle @hdl@ on subsequent reads and writes.
1210 --
1211 -- If the buffer mode is changed from 'BlockBuffering' or
1212 -- 'LineBuffering' to 'NoBuffering', then
1213 --
1214 -- * if @hdl@ is writable, the buffer is flushed as for 'hFlush';
1215 --
1216 -- * if @hdl@ is not writable, the contents of the buffer is discarded.
1217 --
1218 -- This operation may fail with:
1219 --
1220 -- * 'isPermissionError' if the handle has already been used for reading
1221 -- or writing and the implementation does not allow the buffering mode
1222 -- to be changed.
1223
1224 hSetBuffering :: Handle -> BufferMode -> IO ()
1225 hSetBuffering handle mode =
1226 withAllHandles__ "hSetBuffering" handle $ \ handle_ -> do
1227 case haType handle_ of
1228 ClosedHandle -> ioe_closedHandle
1229 _ -> do
1230 {- Note:
1231 - we flush the old buffer regardless of whether
1232 the new buffer could fit the contents of the old buffer
1233 or not.
1234 - allow a handle's buffering to change even if IO has
1235 occurred (ANSI C spec. does not allow this, nor did
1236 the previous implementation of IO.hSetBuffering).
1237 - a non-standard extension is to allow the buffering
1238 of semi-closed handles to change [sof 6/98]
1239 -}
1240 flushBuffer handle_
1241
1242 let state = initBufferState (haType handle_)
1243 new_buf <-
1244 case mode of
1245 -- we always have a 1-character read buffer for
1246 -- unbuffered handles: it's needed to
1247 -- support hLookAhead.
1248 NoBuffering -> allocateBuffer 1 ReadBuffer
1249 LineBuffering -> allocateBuffer dEFAULT_BUFFER_SIZE state
1250 BlockBuffering Nothing -> allocateBuffer dEFAULT_BUFFER_SIZE state
1251 BlockBuffering (Just n) | n <= 0 -> ioe_bufsiz n
1252 | otherwise -> allocateBuffer n state
1253 writeIORef (haBuffer handle_) new_buf
1254
1255 -- for input terminals we need to put the terminal into
1256 -- cooked or raw mode depending on the type of buffering.
1257 is_tty <- fdIsTTY (haFD handle_)
1258 when (is_tty && isReadableHandleType (haType handle_)) $
1259 case mode of
1260 #ifndef mingw32_HOST_OS
1261 -- 'raw' mode under win32 is a bit too specialised (and troublesome
1262 -- for most common uses), so simply disable its use here.
1263 NoBuffering -> setCooked (haFD handle_) False
1264 #else
1265 NoBuffering -> return ()
1266 #endif
1267 _ -> setCooked (haFD handle_) True
1268
1269 -- throw away spare buffers, they might be the wrong size
1270 writeIORef (haBuffers handle_) BufferListNil
1271
1272 return (handle_{ haBufferMode = mode })
1273
1274 -- -----------------------------------------------------------------------------
1275 -- hFlush
1276
1277 -- | The action 'hFlush' @hdl@ causes any items buffered for output
1278 -- in handle @hdl@ to be sent immediately to the operating system.
1279 --
1280 -- This operation may fail with:
1281 --
1282 -- * 'isFullError' if the device is full;
1283 --
1284 -- * 'isPermissionError' if a system resource limit would be exceeded.
1285 -- It is unspecified whether the characters in the buffer are discarded
1286 -- or retained under these circumstances.
1287
1288 hFlush :: Handle -> IO ()
1289 hFlush handle =
1290 wantWritableHandle "hFlush" handle $ \ handle_ -> do
1291 buf <- readIORef (haBuffer handle_)
1292 if bufferIsWritable buf && not (bufferEmpty buf)
1293 then do flushed_buf <- flushWriteBuffer (haFD handle_) (haIsStream handle_) buf
1294 writeIORef (haBuffer handle_) flushed_buf
1295 else return ()
1296
1297
1298 -- -----------------------------------------------------------------------------
1299 -- Repositioning Handles
1300
1301 data HandlePosn = HandlePosn Handle HandlePosition
1302
1303 instance Eq HandlePosn where
1304 (HandlePosn h1 p1) == (HandlePosn h2 p2) = p1==p2 && h1==h2
1305
1306 instance Show HandlePosn where
1307 showsPrec p (HandlePosn h pos) =
1308 showsPrec p h . showString " at position " . shows pos
1309
1310 -- HandlePosition is the Haskell equivalent of POSIX' off_t.
1311 -- We represent it as an Integer on the Haskell side, but
1312 -- cheat slightly in that hGetPosn calls upon a C helper
1313 -- that reports the position back via (merely) an Int.
1314 type HandlePosition = Integer
1315
1316 -- | Computation 'hGetPosn' @hdl@ returns the current I\/O position of
1317 -- @hdl@ as a value of the abstract type 'HandlePosn'.
1318
1319 hGetPosn :: Handle -> IO HandlePosn
1320 hGetPosn handle = do
1321 posn <- hTell handle
1322 return (HandlePosn handle posn)
1323
1324 -- | If a call to 'hGetPosn' @hdl@ returns a position @p@,
1325 -- then computation 'hSetPosn' @p@ sets the position of @hdl@
1326 -- to the position it held at the time of the call to 'hGetPosn'.
1327 --
1328 -- This operation may fail with:
1329 --
1330 -- * 'isPermissionError' if a system resource limit would be exceeded.
1331
1332 hSetPosn :: HandlePosn -> IO ()
1333 hSetPosn (HandlePosn h i) = hSeek h AbsoluteSeek i
1334
1335 -- ---------------------------------------------------------------------------
1336 -- hSeek
1337
1338 -- | A mode that determines the effect of 'hSeek' @hdl mode i@, as follows:
1339 data SeekMode
1340 = AbsoluteSeek -- ^ the position of @hdl@ is set to @i@.
1341 | RelativeSeek -- ^ the position of @hdl@ is set to offset @i@
1342 -- from the current position.
1343 | SeekFromEnd -- ^ the position of @hdl@ is set to offset @i@
1344 -- from the end of the file.
1345 deriving (Eq, Ord, Ix, Enum, Read, Show)
1346
1347 {- Note:
1348 - when seeking using `SeekFromEnd', positive offsets (>=0) means
1349 seeking at or past EOF.
1350
1351 - we possibly deviate from the report on the issue of seeking within
1352 the buffer and whether to flush it or not. The report isn't exactly
1353 clear here.
1354 -}
1355
1356 -- | Computation 'hSeek' @hdl mode i@ sets the position of handle
1357 -- @hdl@ depending on @mode@.
1358 -- The offset @i@ is given in terms of 8-bit bytes.
1359 --
1360 -- If @hdl@ is block- or line-buffered, then seeking to a position which is not
1361 -- in the current buffer will first cause any items in the output buffer to be
1362 -- written to the device, and then cause the input buffer to be discarded.
1363 -- Some handles may not be seekable (see 'hIsSeekable'), or only support a
1364 -- subset of the possible positioning operations (for instance, it may only
1365 -- be possible to seek to the end of a tape, or to a positive offset from
1366 -- the beginning or current position).
1367 -- It is not possible to set a negative I\/O position, or for
1368 -- a physical file, an I\/O position beyond the current end-of-file.
1369 --
1370 -- This operation may fail with:
1371 --
1372 -- * 'isPermissionError' if a system resource limit would be exceeded.
1373
1374 hSeek :: Handle -> SeekMode -> Integer -> IO ()
1375 hSeek handle mode offset =
1376 wantSeekableHandle "hSeek" handle $ \ handle_ -> do
1377 # ifdef DEBUG_DUMP
1378 puts ("hSeek " ++ show (mode,offset) ++ "\n")
1379 # endif
1380 let ref = haBuffer handle_
1381 buf <- readIORef ref
1382 let r = bufRPtr buf
1383 w = bufWPtr buf
1384 fd = haFD handle_
1385
1386 let do_seek =
1387 throwErrnoIfMinus1Retry_ "hSeek"
1388 (c_lseek (haFD handle_) (fromIntegral offset) whence)
1389
1390 whence :: CInt
1391 whence = case mode of
1392 AbsoluteSeek -> sEEK_SET
1393 RelativeSeek -> sEEK_CUR
1394 SeekFromEnd -> sEEK_END
1395
1396 if bufferIsWritable buf
1397 then do new_buf <- flushWriteBuffer fd (haIsStream handle_) buf
1398 writeIORef ref new_buf
1399 do_seek
1400 else do
1401
1402 if mode == RelativeSeek && offset >= 0 && offset < fromIntegral (w - r)
1403 then writeIORef ref buf{ bufRPtr = r + fromIntegral offset }
1404 else do
1405
1406 new_buf <- flushReadBuffer (haFD handle_) buf
1407 writeIORef ref new_buf
1408 do_seek
1409
1410
1411 hTell :: Handle -> IO Integer
1412 hTell handle =
1413 wantSeekableHandle "hGetPosn" handle $ \ handle_ -> do
1414
1415 #if defined(mingw32_HOST_OS)
1416 -- urgh, on Windows we have to worry about \n -> \r\n translation,
1417 -- so we can't easily calculate the file position using the
1418 -- current buffer size. Just flush instead.
1419 flushBuffer handle_
1420 #endif
1421 let fd = haFD handle_
1422 posn <- fromIntegral `liftM`
1423 throwErrnoIfMinus1Retry "hGetPosn"
1424 (c_lseek fd 0 sEEK_CUR)
1425
1426 let ref = haBuffer handle_
1427 buf <- readIORef ref
1428
1429 let real_posn
1430 | bufferIsWritable buf = posn + fromIntegral (bufWPtr buf)
1431 | otherwise = posn - fromIntegral (bufWPtr buf - bufRPtr buf)
1432 # ifdef DEBUG_DUMP
1433 puts ("\nhGetPosn: (fd, posn, real_posn) = " ++ show (fd, posn, real_posn) ++ "\n")
1434 puts (" (bufWPtr, bufRPtr) = " ++ show (bufWPtr buf, bufRPtr buf) ++ "\n")
1435 # endif
1436 return real_posn
1437
1438 -- -----------------------------------------------------------------------------
1439 -- Handle Properties
1440
1441 -- A number of operations return information about the properties of a
1442 -- handle. Each of these operations returns `True' if the handle has
1443 -- the specified property, and `False' otherwise.
1444
1445 hIsOpen :: Handle -> IO Bool
1446 hIsOpen handle =
1447 withHandle_ "hIsOpen" handle $ \ handle_ -> do
1448 case haType handle_ of
1449 ClosedHandle -> return False
1450 SemiClosedHandle -> return False
1451 _ -> return True
1452
1453 hIsClosed :: Handle -> IO Bool
1454 hIsClosed handle =
1455 withHandle_ "hIsClosed" handle $ \ handle_ -> do
1456 case haType handle_ of
1457 ClosedHandle -> return True
1458 _ -> return False
1459
1460 {- not defined, nor exported, but mentioned
1461 here for documentation purposes:
1462
1463 hSemiClosed :: Handle -> IO Bool
1464 hSemiClosed h = do
1465 ho <- hIsOpen h
1466 hc <- hIsClosed h
1467 return (not (ho || hc))
1468 -}
1469
1470 hIsReadable :: Handle -> IO Bool
1471 hIsReadable (DuplexHandle _ _ _) = return True
1472 hIsReadable handle =
1473 withHandle_ "hIsReadable" handle $ \ handle_ -> do
1474 case haType handle_ of
1475 ClosedHandle -> ioe_closedHandle
1476 SemiClosedHandle -> ioe_closedHandle
1477 htype -> return (isReadableHandleType htype)
1478
1479 hIsWritable :: Handle -> IO Bool
1480 hIsWritable (DuplexHandle _ _ _) = return True
1481 hIsWritable handle =
1482 withHandle_ "hIsWritable" handle $ \ handle_ -> do
1483 case haType handle_ of
1484 ClosedHandle -> ioe_closedHandle
1485 SemiClosedHandle -> ioe_closedHandle
1486 htype -> return (isWritableHandleType htype)
1487
1488 -- | Computation 'hGetBuffering' @hdl@ returns the current buffering mode
1489 -- for @hdl@.
1490
1491 hGetBuffering :: Handle -> IO BufferMode
1492 hGetBuffering handle =
1493 withHandle_ "hGetBuffering" handle $ \ handle_ -> do
1494 case haType handle_ of
1495 ClosedHandle -> ioe_closedHandle
1496 _ ->
1497 -- We're being non-standard here, and allow the buffering
1498 -- of a semi-closed handle to be queried. -- sof 6/98
1499 return (haBufferMode handle_) -- could be stricter..
1500
1501 hIsSeekable :: Handle -> IO Bool
1502 hIsSeekable handle =
1503 withHandle_ "hIsSeekable" handle $ \ handle_ -> do
1504 case haType handle_ of
1505 ClosedHandle -> ioe_closedHandle
1506 SemiClosedHandle -> ioe_closedHandle
1507 AppendHandle -> return False
1508 _ -> do t <- fdType (haFD handle_)
1509 return ((t == RegularFile || t == RawDevice)
1510 && (haIsBin handle_ || tEXT_MODE_SEEK_ALLOWED))
1511
1512 -- -----------------------------------------------------------------------------
1513 -- Changing echo status (Non-standard GHC extensions)
1514
1515 -- | Set the echoing status of a handle connected to a terminal.
1516
1517 hSetEcho :: Handle -> Bool -> IO ()
1518 hSetEcho handle on = do
1519 isT <- hIsTerminalDevice handle
1520 if not isT
1521 then return ()
1522 else
1523 withHandle_ "hSetEcho" handle $ \ handle_ -> do
1524 case haType handle_ of
1525 ClosedHandle -> ioe_closedHandle
1526 _ -> setEcho (haFD handle_) on
1527
1528 -- | Get the echoing status of a handle connected to a terminal.
1529
1530 hGetEcho :: Handle -> IO Bool
1531 hGetEcho handle = do
1532 isT <- hIsTerminalDevice handle
1533 if not isT
1534 then return False
1535 else
1536 withHandle_ "hGetEcho" handle $ \ handle_ -> do
1537 case haType handle_ of
1538 ClosedHandle -> ioe_closedHandle
1539 _ -> getEcho (haFD handle_)
1540
1541 -- | Is the handle connected to a terminal?
1542
1543 hIsTerminalDevice :: Handle -> IO Bool
1544 hIsTerminalDevice handle = do
1545 withHandle_ "hIsTerminalDevice" handle $ \ handle_ -> do
1546 case haType handle_ of
1547 ClosedHandle -> ioe_closedHandle
1548 _ -> fdIsTTY (haFD handle_)
1549
1550 -- -----------------------------------------------------------------------------
1551 -- hSetBinaryMode
1552
1553 -- | Select binary mode ('True') or text mode ('False') on a open handle.
1554 -- (See also 'openBinaryFile'.)
1555
1556 hSetBinaryMode :: Handle -> Bool -> IO ()
1557 hSetBinaryMode handle bin =
1558 withAllHandles__ "hSetBinaryMode" handle $ \ handle_ ->
1559 do throwErrnoIfMinus1_ "hSetBinaryMode"
1560 (setmode (haFD handle_) bin)
1561 return handle_{haIsBin=bin}
1562
1563 foreign import ccall unsafe "__hscore_setmode"
1564 setmode :: CInt -> Bool -> IO CInt
1565
1566 -- -----------------------------------------------------------------------------
1567 -- Duplicating a Handle
1568
1569 -- | Returns a duplicate of the original handle, with its own buffer.
1570 -- The two Handles will share a file pointer, however. The original
1571 -- handle's buffer is flushed, including discarding any input data,
1572 -- before the handle is duplicated.
1573
1574 hDuplicate :: Handle -> IO Handle
1575 hDuplicate h@(FileHandle path m) = do
1576 new_h_ <- withHandle' "hDuplicate" h m (dupHandle h Nothing)
1577 newFileHandle path (handleFinalizer path) new_h_
1578 hDuplicate h@(DuplexHandle path r w) = do
1579 new_w_ <- withHandle' "hDuplicate" h w (dupHandle h Nothing)
1580 new_w <- newMVar new_w_
1581 new_r_ <- withHandle' "hDuplicate" h r (dupHandle h (Just new_w))
1582 new_r <- newMVar new_r_
1583 addMVarFinalizer new_w (handleFinalizer path new_w)
1584 return (DuplexHandle path new_r new_w)
1585
1586 dupHandle :: Handle -> Maybe (MVar Handle__) -> Handle__
1587 -> IO (Handle__, Handle__)
1588 dupHandle h other_side h_ = do
1589 -- flush the buffer first, so we don't have to copy its contents
1590 flushBuffer h_
1591 new_fd <- case other_side of
1592 Nothing -> throwErrnoIfMinus1 "dupHandle" $ c_dup (haFD h_)
1593 Just r -> withHandle_' "dupHandle" h r (return . haFD)
1594 dupHandle_ other_side h_ new_fd
1595
1596 dupHandleTo other_side hto_ h_ = do
1597 flushBuffer h_
1598 -- Windows' dup2 does not return the new descriptor, unlike Unix
1599 throwErrnoIfMinus1 "dupHandleTo" $
1600 c_dup2 (haFD h_) (haFD hto_)
1601 dupHandle_ other_side h_ (haFD hto_)
1602
1603 dupHandle_ :: Maybe (MVar Handle__) -> Handle__ -> FD
1604 -> IO (Handle__, Handle__)
1605 dupHandle_ other_side h_ new_fd = do
1606 buffer <- allocateBuffer dEFAULT_BUFFER_SIZE (initBufferState (haType h_))
1607 ioref <- newIORef buffer
1608 ioref_buffers <- newIORef BufferListNil
1609
1610 let new_handle_ = h_{ haFD = new_fd,
1611 haBuffer = ioref,
1612 haBuffers = ioref_buffers,
1613 haOtherSide = other_side }
1614 return (h_, new_handle_)
1615
1616 -- -----------------------------------------------------------------------------
1617 -- Replacing a Handle
1618
1619 {- |
1620 Makes the second handle a duplicate of the first handle. The second
1621 handle will be closed first, if it is not already.
1622
1623 This can be used to retarget the standard Handles, for example:
1624
1625 > do h <- openFile "mystdout" WriteMode
1626 > hDuplicateTo h stdout
1627 -}
1628
1629 hDuplicateTo :: Handle -> Handle -> IO ()
1630 hDuplicateTo h1@(FileHandle _ m1) h2@(FileHandle _ m2) = do
1631 withHandle__' "hDuplicateTo" h2 m2 $ \h2_ -> do
1632 _ <- hClose_help h2_
1633 withHandle' "hDuplicateTo" h1 m1 (dupHandleTo Nothing h2_)
1634 hDuplicateTo h1@(DuplexHandle _ r1 w1) h2@(DuplexHandle _ r2 w2) = do
1635 withHandle__' "hDuplicateTo" h2 w2 $ \w2_ -> do
1636 _ <- hClose_help w2_
1637 withHandle' "hDuplicateTo" h1 r1 (dupHandleTo Nothing w2_)
1638 withHandle__' "hDuplicateTo" h2 r2 $ \r2_ -> do
1639 _ <- hClose_help r2_
1640 withHandle' "hDuplicateTo" h1 r1 (dupHandleTo (Just w1) r2_)
1641 hDuplicateTo h1 _ =
1642 ioException (IOError (Just h1) IllegalOperation "hDuplicateTo"
1643 "handles are incompatible" Nothing)
1644
1645 -- ---------------------------------------------------------------------------
1646 -- showing Handles.
1647 --
1648 -- | 'hShow' is in the 'IO' monad, and gives more comprehensive output
1649 -- than the (pure) instance of 'Show' for 'Handle'.
1650
1651 hShow :: Handle -> IO String
1652 hShow h@(FileHandle path _) = showHandle' path False h
1653 hShow h@(DuplexHandle path _ _) = showHandle' path True h
1654
1655 showHandle' filepath is_duplex h =
1656 withHandle_ "showHandle" h $ \hdl_ ->
1657 let
1658 showType | is_duplex = showString "duplex (read-write)"
1659 | otherwise = shows (haType hdl_)
1660 in
1661 return
1662 (( showChar '{' .
1663 showHdl (haType hdl_)
1664 (showString "loc=" . showString filepath . showChar ',' .
1665 showString "type=" . showType . showChar ',' .
1666 showString "binary=" . shows (haIsBin hdl_) . showChar ',' .
1667 showString "buffering=" . showBufMode (unsafePerformIO (readIORef (haBuffer hdl_))) (haBufferMode hdl_) . showString "}" )
1668 ) "")
1669 where
1670
1671 showHdl :: HandleType -> ShowS -> ShowS
1672 showHdl ht cont =
1673 case ht of
1674 ClosedHandle -> shows ht . showString "}"
1675 _ -> cont
1676
1677 showBufMode :: Buffer -> BufferMode -> ShowS
1678 showBufMode buf bmo =
1679 case bmo of
1680 NoBuffering -> showString "none"
1681 LineBuffering -> showString "line"
1682 BlockBuffering (Just n) -> showString "block " . showParen True (shows n)
1683 BlockBuffering Nothing -> showString "block " . showParen True (shows def)
1684 where
1685 def :: Int
1686 def = bufSize buf
1687
1688 -- ---------------------------------------------------------------------------
1689 -- debugging
1690
1691 #if defined(DEBUG_DUMP)
1692 puts :: String -> IO ()
1693 puts s = do write_rawBuffer 1 (unsafeCoerce# (packCString# s)) 0 (fromIntegral (length s))
1694 return ()
1695 #endif
1696
1697 -- -----------------------------------------------------------------------------
1698 -- utils
1699
1700 throwErrnoIfMinus1RetryOnBlock :: String -> IO CInt -> IO CInt -> IO CInt
1701 throwErrnoIfMinus1RetryOnBlock loc f on_block =
1702 do
1703 res <- f
1704 if (res :: CInt) == -1
1705 then do
1706 err <- getErrno
1707 if err == eINTR
1708 then throwErrnoIfMinus1RetryOnBlock loc f on_block
1709 else if err == eWOULDBLOCK || err == eAGAIN
1710 then do on_block
1711 else throwErrno loc
1712 else return res
1713
1714 -- -----------------------------------------------------------------------------
1715 -- wrappers to platform-specific constants:
1716
1717 foreign import ccall unsafe "__hscore_supportsTextMode"
1718 tEXT_MODE_SEEK_ALLOWED :: Bool
1719
1720 foreign import ccall unsafe "__hscore_bufsiz" dEFAULT_BUFFER_SIZE :: Int
1721 foreign import ccall unsafe "__hscore_seek_cur" sEEK_CUR :: CInt
1722 foreign import ccall unsafe "__hscore_seek_set" sEEK_SET :: CInt
1723 foreign import ccall unsafe "__hscore_seek_end" sEEK_END :: CInt