1 {-# OPTIONS -fno-implicit-prelude #-}
5 -- -----------------------------------------------------------------------------
6 -- $Id: PrelIO.hsc,v 1.3 2001/05/22 15:06:47 simonmar Exp $
8 -- (c) The University of Glasgow, 1992-2001
12 -- This module defines all basic IO operations.
13 -- These are needed for the IO operations exported by Prelude,
14 -- but as it happens they also do everything required by library
20 #include "PrelHandle_hsc.h"
25 import PrelMarshalAlloc
26 import PrelMarshalUtils
34 import PrelHandle -- much of the real stuff is in here
41 import PrelMaybe ( Maybe(..) )
44 import PrelException ( ioError, catch, throw )
47 -- -----------------------------------------------------------------------------
50 putChar :: Char -> IO ()
51 putChar c = hPutChar stdout c
53 putStr :: String -> IO ()
54 putStr s = hPutStr stdout s
56 putStrLn :: String -> IO ()
57 putStrLn s = do putStr s
60 print :: Show a => a -> IO ()
61 print x = putStrLn (show x)
64 getChar = hGetChar stdin
67 getLine = hGetLine stdin
69 getContents :: IO String
70 getContents = hGetContents stdin
72 interact :: (String -> String) -> IO ()
73 interact f = do s <- getContents
76 readFile :: FilePath -> IO String
77 readFile name = openFile name ReadMode >>= hGetContents
79 writeFile :: FilePath -> String -> IO ()
80 writeFile name str = do
81 hdl <- openFile name WriteMode
85 appendFile :: FilePath -> String -> IO ()
86 appendFile name str = do
87 hdl <- openFile name AppendMode
91 readLn :: Read a => IO a
92 readLn = do l <- getLine
96 -- raises an exception instead of an error
97 readIO :: Read a => String -> IO a
98 readIO s = case (do { (x,t) <- reads s ;
101 #ifndef NEW_READS_REP
103 [] -> ioError (userError "Prelude.readIO: no parse")
104 _ -> ioError (userError "Prelude.readIO: ambiguous parse")
107 Nothing -> ioError (userError "Prelude.readIO: no parse")
110 -- ---------------------------------------------------------------------------
111 -- Simple input operations
113 -- Computation "hReady hdl" indicates whether at least
114 -- one item is available for input from handle "hdl".
116 -- If hWaitForInput finds anything in the Handle's buffer, it
117 -- immediately returns. If not, it tries to read from the underlying
118 -- OS handle. Notice that for buffered Handles connected to terminals
119 -- this means waiting until a complete line is available.
121 hReady :: Handle -> IO Bool
122 hReady h = hWaitForInput h 0
124 hWaitForInput :: Handle -> Int -> IO Bool
125 hWaitForInput h msecs = do
126 wantReadableHandle "hReady" h $ \ handle_ -> do
127 let ref = haBuffer handle_
130 if not (bufferEmpty buf)
134 r <- throwErrnoIfMinus1Retry "hReady"
135 (inputReady (fromIntegral (haFD handle_)) (fromIntegral msecs))
138 foreign import "inputReady"
139 inputReady :: CInt -> CInt -> IO CInt
141 -- ---------------------------------------------------------------------------
144 -- hGetChar reads the next character from a handle,
145 -- blocking until a character is available.
147 hGetChar :: Handle -> IO Char
149 wantReadableHandle "hGetChar" handle $ \handle_ -> do
151 let fd = haFD handle_
152 ref = haBuffer handle_
155 if not (bufferEmpty buf)
156 then hGetcBuffered fd ref buf
160 case haBufferMode handle_ of
162 new_buf <- fillReadBuffer fd True buf
163 hGetcBuffered fd ref new_buf
164 BlockBuffering _ -> do
165 new_buf <- fillReadBuffer fd False buf
166 hGetcBuffered fd ref new_buf
168 -- make use of the minimal buffer we already have
170 r <- throwErrnoIfMinus1RetryMayBlock "hGetChar"
171 (read_off (fromIntegral fd) raw 0 1)
175 else do (c,_) <- readCharFromBuffer raw 0
178 hGetcBuffered fd ref buf@Buffer{ bufBuf=b, bufRPtr=r, bufWPtr=w }
179 = do (c,r) <- readCharFromBuffer b r
180 let new_buf | r == w = buf{ bufRPtr=0, bufWPtr=0 }
181 | otherwise = buf{ bufRPtr=r }
182 writeIORef ref new_buf
185 -- ---------------------------------------------------------------------------
188 -- If EOF is reached before EOL is encountered, ignore the EOF and
189 -- return the partial line. Next attempt at calling hGetLine on the
190 -- handle will yield an EOF IO exception though.
192 -- ToDo: the unbuffered case is wrong: it doesn't lock the handle for
194 hGetLine :: Handle -> IO String
196 m <- wantReadableHandle "hGetLine" h $ \ handle_ -> do
197 case haBufferMode handle_ of
198 NoBuffering -> return Nothing
200 l <- hGetLineBuffered handle_
202 BlockBuffering _ -> do
203 l <- hGetLineBuffered handle_
206 Nothing -> hGetLineUnBuffered h
210 hGetLineBuffered handle_ = do
211 let ref = haBuffer handle_
213 hGetLineBufferedLoop handle_ ref buf []
216 hGetLineBufferedLoop handle_ ref
217 buf@Buffer{ bufRPtr=r, bufWPtr=w, bufBuf=raw } xss =
219 -- find the end-of-line character, if there is one
221 | r == w = return (False, w)
223 (c,r') <- readCharFromBuffer raw r
225 then return (True, r) -- NB. not r': don't include the '\n'
228 (eol, off) <- loop raw r
231 puts ("hGetLineBufferedLoop: r=" ++ show r ++ ", w=" ++ show w ++ ", off=" ++ show off ++ "\n")
234 xs <- unpack raw r off
236 then do if w == off + 1
237 then writeIORef ref buf{ bufRPtr=0, bufWPtr=0 }
238 else writeIORef ref buf{ bufRPtr = off + 1 }
239 return (concat (reverse (xs:xss)))
241 maybe_buf <- maybeFillReadBuffer (haFD handle_) True
242 buf{ bufWPtr=0, bufRPtr=0 }
244 -- Nothing indicates we caught an EOF, and we may have a
245 -- partial line to return.
246 Nothing -> let str = concat (reverse (xs:xss)) in
251 hGetLineBufferedLoop handle_ ref new_buf (xs:xss)
254 unpack :: RawBuffer -> Int -> Int -> IO [Char]
255 unpack buf r 0 = return ""
256 unpack buf (I## r) (I## len) = IO $ \s -> unpack [] (len -## 1##) s
259 | i <## r = (## s, acc ##)
261 case readCharArray## buf i s of
262 (## s, ch ##) -> unpack (C## ch : acc) (i -## 1##) s
265 hGetLineUnBuffered :: Handle -> IO String
266 hGetLineUnBuffered h = do
279 if isEOFError err then
289 -- -----------------------------------------------------------------------------
292 -- hGetContents returns the list of characters corresponding to the
293 -- unread portion of the channel or file managed by the handle, which
294 -- is made semi-closed.
296 hGetContents :: Handle -> IO String
297 hGetContents handle =
298 -- can't use wantReadableHandle here, because we want to side effect
300 withHandle "hGetContents" handle $ \ handle_ -> do
301 case haType handle_ of
302 ClosedHandle -> ioe_closedHandle
303 SemiClosedHandle -> ioe_closedHandle
304 AppendHandle -> ioException not_readable_error
305 WriteHandle -> ioException not_readable_error
306 _ -> do xs <- lazyRead handle
307 return (handle_{ haType=SemiClosedHandle}, xs )
310 IOError (Just handle) IllegalOperation "hGetContents"
311 "handle is not open for reading" Nothing
313 -- Note that someone may close the semi-closed handle (or change its
314 -- buffering), so each these lazy read functions are pulled on, they
315 -- have to check whether the handle has indeed been closed.
317 lazyRead :: Handle -> IO String
320 withHandle_ "lazyRead" handle $ \ handle_ -> do
321 case haType handle_ of
322 ClosedHandle -> return ""
323 SemiClosedHandle -> lazyRead' handle handle_
325 (IOError (Just handle) IllegalOperation "lazyRead"
326 "illegal handle type" Nothing)
328 lazyRead' h handle_ = do
329 let ref = haBuffer handle_
332 -- even a NoBuffering handle can have a char in the buffer...
335 if not (bufferEmpty buf)
336 then lazyReadBuffered h fd ref buf
339 case haBufferMode handle_ of
341 -- make use of the minimal buffer we already have
344 r <- throwErrnoIfMinus1RetryMayBlock "hGetChar"
345 (read_off (fromIntegral fd) raw 0 1)
349 else do (c,_) <- readCharFromBuffer raw 0
353 LineBuffering -> lazyReadBuffered h fd ref buf
354 BlockBuffering _ -> lazyReadBuffered h fd ref buf
356 -- we never want to block during the read, so we call fillReadBuffer with
357 -- is_line==True, which tells it to "just read what there is".
358 lazyReadBuffered h fd ref buf = do
361 then maybeFillReadBuffer fd True buf
362 else return (Just buf)
363 case maybe_new_buf of
367 writeIORef ref buf{ bufRPtr=0, bufWPtr=0 }
368 unpackAcc (bufBuf buf) (bufRPtr buf) (bufWPtr buf) more
371 maybeFillReadBuffer fd is_line buf
373 (do buf <- fillReadBuffer fd is_line buf
376 (\e -> if isEOFError e
381 unpackAcc :: RawBuffer -> Int -> Int -> [Char] -> IO [Char]
382 unpackAcc buf r 0 acc = return ""
383 unpackAcc buf (I## r) (I## len) acc = IO $ \s -> unpack acc (len -## 1##) s
386 | i <## r = (## s, acc ##)
388 case readCharArray## buf i s of
389 (## s, ch ##) -> unpack (C## ch : acc) (i -## 1##) s
391 -- ---------------------------------------------------------------------------
394 -- `hPutChar hdl ch' writes the character `ch' to the file or channel
395 -- managed by `hdl'. Characters may be buffered if buffering is
396 -- enabled for `hdl'.
398 hPutChar :: Handle -> Char -> IO ()
400 c `seq` do -- must evaluate c before grabbing the handle lock
401 wantWritableHandle "hPutChar" handle $ \ handle_ -> do
402 let fd = haFD handle_
403 case haBufferMode handle_ of
404 LineBuffering -> hPutcBuffered handle_ True c
405 BlockBuffering _ -> hPutcBuffered handle_ False c
407 withObject (castCharToCChar c) $ \buf ->
408 throwErrnoIfMinus1RetryMayBlock_ "hPutChar"
409 (c_write (fromIntegral fd) buf 1)
413 hPutcBuffered handle_ is_line c = do
414 let ref = haBuffer handle_
417 w' <- writeCharIntoBuffer (bufBuf buf) w c
418 let new_buf = buf{ bufWPtr = w' }
419 if bufferFull new_buf || is_line && c == '\n'
421 flushed_buf <- flushWriteBuffer (haFD handle_) new_buf
422 writeIORef ref flushed_buf
424 writeIORef ref new_buf
427 hPutChars :: Handle -> [Char] -> IO ()
428 hPutChars handle [] = return ()
429 hPutChars handle (c:cs) = hPutChar handle c >> hPutChars handle cs
431 -- ---------------------------------------------------------------------------
434 -- `hPutStr hdl s' writes the string `s' to the file or
435 -- hannel managed by `hdl', buffering the output if needs be.
437 -- We go to some trouble to avoid keeping the handle locked while we're
438 -- evaluating the string argument to hPutStr, in case doing so triggers another
439 -- I/O operation on the same handle which would lead to deadlock. The classic
442 -- putStr (trace "hello" "world")
444 -- so the basic scheme is this:
446 -- * copy the string into a fresh buffer,
447 -- * "commit" the buffer to the handle.
449 -- Committing may involve simply copying the contents of the new
450 -- buffer into the handle's buffer, flushing one or both buffers, or
451 -- maybe just swapping the buffers over (if the handle's buffer was
452 -- empty). See commitBuffer below.
454 hPutStr :: Handle -> String -> IO ()
455 hPutStr handle str = do
456 buffer_mode <- wantWritableHandle "hPutStr" handle
457 (\ handle_ -> do getSpareBuffer handle_)
459 (NoBuffering, _) -> do
460 hPutChars handle str -- v. slow, but we don't care
461 (LineBuffering, buf) -> do
462 writeLines handle buf str
463 (BlockBuffering _, buf) -> do
464 writeBlocks handle buf str
467 getSpareBuffer :: Handle__ -> IO (BufferMode, Buffer)
468 getSpareBuffer Handle__{haBuffer=ref,
473 NoBuffering -> return (mode, error "no buffer!")
475 bufs <- readIORef spare_ref
478 BufferListCons b rest -> do
479 writeIORef spare_ref rest
480 return ( mode, newEmptyBuffer b WriteBuffer (bufSize buf))
482 new_buf <- allocateBuffer (bufSize buf) WriteBuffer
483 return (mode, new_buf)
486 writeLines :: Handle -> Buffer -> String -> IO ()
487 writeLines hdl Buffer{ bufBuf=raw, bufSize=len } s =
489 shoveString :: Int -> [Char] -> IO ()
490 -- check n == len first, to ensure that shoveString is strict in n.
491 shoveString n cs | n == len = do
492 new_buf <- commitBuffer hdl raw len n True{-needs flush-} False
493 writeBlocks hdl new_buf cs
494 shoveString n [] = do
495 commitBuffer hdl raw len n False{-no flush-} True{-release-}
497 shoveString n (c:cs) = do
498 n' <- writeCharIntoBuffer raw n c
503 writeBlocks :: Handle -> Buffer -> String -> IO ()
504 writeBlocks hdl Buffer{ bufBuf=raw, bufSize=len } s =
506 shoveString :: Int -> [Char] -> IO ()
507 -- check n == len first, to ensure that shoveString is strict in n.
508 shoveString n cs | n == len = do
509 new_buf <- commitBuffer hdl raw len n True{-needs flush-} False
510 writeBlocks hdl new_buf cs
511 shoveString n [] = do
512 commitBuffer hdl raw len n False{-no flush-} True{-release-}
514 shoveString n (c:cs) = do
515 n' <- writeCharIntoBuffer raw n c
520 -- -----------------------------------------------------------------------------
521 -- commitBuffer handle buf sz count flush release
523 -- Write the contents of the buffer 'buf' ('sz' bytes long, containing
524 -- 'count' bytes of data) to handle (handle must be block or line buffered).
528 -- for block/line buffering,
529 -- 1. If there isn't room in the handle buffer, flush the handle
532 -- 2. If the handle buffer is empty,
534 -- then write buf directly to the device.
535 -- else swap the handle buffer with buf.
537 -- 3. If the handle buffer is non-empty, copy buf into the
538 -- handle buffer. Then, if flush != 0, flush
542 :: Handle -- handle to commit to
543 -> RawBuffer -> Int -- address and size (in bytes) of buffer
544 -> Int -- number of bytes of data in buffer
545 -> Bool -- flush the handle afterward?
546 -> Bool -- release the buffer?
549 commitBuffer hdl raw sz count flush release = do
550 wantWritableHandle "commitAndReleaseBuffer" hdl $
551 \ handle_@Handle__{ haFD=fd, haBuffer=ref, haBuffers=spare_buf_ref } -> do
554 puts ("commitBuffer: sz=" ++ show sz ++ ", count=" ++ show count
555 ++ ", flush=" ++ show flush ++ ", release=" ++ show release ++"\n")
558 old_buf@Buffer{ bufBuf=old_raw, bufRPtr=r, bufWPtr=w, bufSize=size }
562 -- enough room in handle buffer?
563 if (not flush && (size - w > count))
564 -- The > is to be sure that we never exactly fill
565 -- up the buffer, which would require a flush. So
566 -- if copying the new data into the buffer would
567 -- make the buffer full, we just flush the existing
568 -- buffer and the new data immediately, rather than
569 -- copying before flushing.
571 -- not flushing, and there's enough room in the buffer:
572 -- just copy the data in and update bufWPtr.
573 then do memcpy_off old_raw w raw (fromIntegral count)
574 writeIORef ref old_buf{ bufWPtr = w + count }
575 return (newEmptyBuffer raw WriteBuffer sz)
577 -- else, we have to flush
578 else do flushed_buf <- flushWriteBuffer fd old_buf
581 Buffer{ bufBuf=raw, bufState=WriteBuffer,
582 bufRPtr=0, bufWPtr=count, bufSize=sz }
584 -- if: (a) we don't have to flush, and
585 -- (b) size(new buffer) == size(old buffer), and
586 -- (c) new buffer is not full,
587 -- we can just just swap them over...
588 if (not flush && sz == size && count /= sz)
590 writeIORef ref this_buf
593 -- otherwise, we have to flush the new data too,
594 -- and start with a fresh buffer
596 flushWriteBuffer fd this_buf
597 writeIORef ref flushed_buf
598 -- if the sizes were different, then allocate
599 -- a new buffer of the correct size.
601 then return (newEmptyBuffer raw WriteBuffer sz)
602 else allocateBuffer size WriteBuffer
604 -- release the buffer if necessary
605 if release && bufSize buf_ret == size
607 spare_bufs <- readIORef spare_buf_ref
608 writeIORef spare_buf_ref
609 (BufferListCons (bufBuf buf_ret) spare_bufs)
615 foreign import "memcpy_wrap" unsafe
616 memcpy_off :: RawBuffer -> Int -> RawBuffer -> CSize -> IO (Ptr ())
618 void *memcpy_wrap(char *dst, int dst_off, char *src, size_t sz) \
619 { return memcpy(dst+dst_off, src, sz); }
621 -- ---------------------------------------------------------------------------
624 -- Derived action `hPutStrLn hdl str' writes the string `str' to
625 -- the handle `hdl', adding a newline at the end.
627 hPutStrLn :: Handle -> String -> IO ()
628 hPutStrLn hndl str = do
632 -- ---------------------------------------------------------------------------
635 -- Computation `hPrint hdl t' writes the string representation of `t'
636 -- given by the `shows' function to the file or channel managed by `hdl'.
638 hPrint :: Show a => Handle -> a -> IO ()
639 hPrint hdl = hPutStrLn hdl . show