+%
+% (c) The GRAP/AQUA Project, Glasgow University, 1992-1996
+%
+\section[PrelIO]{Module @PrelIO@}
+
+This module defines all basic IO operations.
+These are needed for the IO operations exported by Prelude,
+but as it happens they also do everything required by library
+module IO.
+
+
+\begin{code}
+{-# OPTIONS -fno-implicit-prelude -#include "cbits/stgio.h" #-}
+
+module PrelIO where
+
+import PrelBase
+
+import PrelIOBase
+import PrelHandle -- much of the real stuff is in here
+
+import PrelRead ( readParen, Read(..), reads, lex,
+ readIO
+ )
+import PrelShow
+import PrelMaybe ( Either(..), Maybe(..) )
+import PrelAddr ( Addr(..), nullAddr )
+import PrelByteArr ( ByteArray )
+import PrelPack ( unpackNBytesAccST )
+import PrelException ( ioError, catch )
+import PrelConc
+\end{code}
+
+
+
+%*********************************************************
+%* *
+\subsection{Standard IO}
+%* *
+%*********************************************************
+
+The Prelude has from Day 1 provided a collection of common
+IO functions. We define these here, but let the Prelude
+export them.
+
+\begin{code}
+putChar :: Char -> IO ()
+putChar c = hPutChar stdout c
+
+putStr :: String -> IO ()
+putStr s = hPutStr stdout s
+
+putStrLn :: String -> IO ()
+putStrLn s = do putStr s
+ putChar '\n'
+
+print :: Show a => a -> IO ()
+print x = putStrLn (show x)
+
+getChar :: IO Char
+getChar = hGetChar stdin
+
+getLine :: IO String
+getLine = hGetLine stdin
+
+getContents :: IO String
+getContents = hGetContents stdin
+
+interact :: (String -> String) -> IO ()
+interact f = do s <- getContents
+ putStr (f s)
+
+readFile :: FilePath -> IO String
+readFile name = openFile name ReadMode >>= hGetContents
+
+writeFile :: FilePath -> String -> IO ()
+writeFile name str = do
+ hdl <- openFile name WriteMode
+ hPutStr hdl str
+ hClose hdl
+
+appendFile :: FilePath -> String -> IO ()
+appendFile name str = do
+ hdl <- openFile name AppendMode
+ hPutStr hdl str
+ hClose hdl
+
+readLn :: Read a => IO a
+readLn = do l <- getLine
+ r <- readIO l
+ return r
+\end{code}
+
+
+%*********************************************************
+%* *
+\subsection{Simple input operations}
+%* *
+%*********************************************************
+
+Computation @hReady hdl@ indicates whether at least
+one item is available for input from handle {\em hdl}.
+
+@hWaitForInput@ is the generalisation, wait for \tr{n} milliseconds
+before deciding whether the Handle has run dry or not.
+
+If @hWaitForInput@ finds anything in the Handle's buffer, it immediately returns.
+If not, it tries to read from the underlying OS handle. Notice that
+for buffered Handles connected to terminals this means waiting until a complete
+line is available.
+
+\begin{code}
+hReady :: Handle -> IO Bool
+hReady h = hWaitForInput h 0
+
+hWaitForInput :: Handle -> Int -> IO Bool
+hWaitForInput handle msecs =
+ wantReadableHandle "hWaitForInput" handle $ \ handle_ -> do
+ rc <- inputReady (haFO__ handle_) (msecs::Int) -- ConcHask: SAFE, won't block
+ case (rc::Int) of
+ 0 -> return False
+ 1 -> return True
+ _ -> constructErrorAndFail "hWaitForInput"
+\end{code}
+
+@hGetChar hdl@ reads the next character from handle @hdl@,
+blocking until a character is available.
+
+\begin{code}
+hGetChar :: Handle -> IO Char
+hGetChar handle = do
+ c <- mayBlockRead "hGetChar" handle fileGetc
+ return (chr c)
+
+{-
+ If EOF is reached before EOL is encountered, ignore the
+ EOF and return the partial line. Next attempt at calling
+ hGetLine on the handle will yield an EOF IO exception though.
+-}
+hGetLine :: Handle -> IO String
+hGetLine h = do
+ c <- hGetChar h
+ if c == '\n' then
+ return ""
+ else do
+ l <- getRest
+ return (c:l)
+ where
+ getRest = do
+ c <-
+ catch
+ (hGetChar h)
+ (\ err -> do
+ if isEOFError err then
+ return '\n'
+ else
+ ioError err)
+ if c == '\n' then
+ return ""
+ else do
+ s <- getRest
+ return (c:s)
+
+\end{code}
+
+@hLookahead hdl@ returns the next character from handle @hdl@
+without removing it from the input buffer, blocking until a
+character is available.
+
+\begin{code}
+hLookAhead :: Handle -> IO Char
+hLookAhead handle = do
+ rc <- mayBlockRead "hLookAhead" handle fileLookAhead
+ return (chr rc)
+\end{code}
+
+
+%*********************************************************
+%* *
+\subsection{Getting the entire contents of a handle}
+%* *
+%*********************************************************
+
+@hGetContents hdl@ returns the list of characters corresponding
+to the unread portion of the channel or file managed by @hdl@,
+which is made semi-closed.
+
+\begin{code}
+hGetContents :: Handle -> IO String
+hGetContents handle =
+ -- can't use wantReadableHandle here, because we want to side effect
+ -- the handle.
+ withHandle handle $ \ handle_ -> do
+ case haType__ handle_ of
+ ErrorHandle theError -> ioError theError
+ ClosedHandle -> ioe_closedHandle "hGetContents" handle
+ SemiClosedHandle -> ioe_closedHandle "hGetContents" handle
+ AppendHandle -> ioError not_readable_error
+ WriteHandle -> ioError not_readable_error
+ _ -> do
+ {-
+ To avoid introducing an extra layer of buffering here,
+ we provide three lazy read methods, based on character,
+ line, and block buffering.
+ -}
+ let handle_' = handle_{ haType__ = SemiClosedHandle }
+ case (haBufferMode__ handle_) of
+ LineBuffering -> do
+ str <- unsafeInterleaveIO (lazyReadLine handle (haFO__ handle_))
+ return (handle_', str)
+ BlockBuffering _ -> do
+ str <- unsafeInterleaveIO (lazyReadBlock handle (haFO__ handle_))
+ return (handle_', str)
+ NoBuffering -> do
+ str <- unsafeInterleaveIO (lazyReadChar handle (haFO__ handle_))
+ return (handle_', str)
+ where
+ not_readable_error =
+ IOError (Just handle) IllegalOperation "hGetContents"
+ ("handle is not open for reading")
+\end{code}
+
+Note that someone may close the semi-closed handle (or change its buffering),
+so each these lazy read functions are pulled on, they have to check whether
+the handle has indeed been closed.
+
+\begin{code}
+#ifndef __PARALLEL_HASKELL__
+lazyReadBlock :: Handle -> ForeignObj -> IO String
+lazyReadLine :: Handle -> ForeignObj -> IO String
+lazyReadChar :: Handle -> ForeignObj -> IO String
+#else
+lazyReadBlock :: Handle -> Addr -> IO String
+lazyReadLine :: Handle -> Addr -> IO String
+lazyReadChar :: Handle -> Addr -> IO String
+#endif
+
+lazyReadBlock handle fo = do
+ buf <- getBufStart fo 0
+ bytes <- mayBlock fo (readBlock fo) -- ConcHask: UNSAFE, may block.
+ case (bytes::Int) of
+ -3 -> -- buffering has been turned off, use lazyReadChar instead
+ lazyReadChar handle fo
+ -2 -> return ""
+ -1 -> -- an error occurred, close the handle
+ withHandle handle $ \ handle_ -> do
+ closeFile (haFO__ handle_) 0{-don't bother flushing-} -- ConcHask: SAFE, won't block.
+ return (handle_ { haType__ = ClosedHandle,
+ haFO__ = nullFile__ },
+ "")
+ _ -> do
+ more <- unsafeInterleaveIO (lazyReadBlock handle fo)
+ stToIO (unpackNBytesAccST buf bytes more)
+
+lazyReadLine handle fo = do
+ bytes <- mayBlock fo (readLine fo) -- ConcHask: UNSAFE, may block.
+ case (bytes::Int) of
+ -3 -> -- buffering has been turned off, use lazyReadChar instead
+ lazyReadChar handle fo
+ -2 -> return "" -- handle closed by someone else, stop reading.
+ -1 -> -- an error occurred, close the handle
+ withHandle handle $ \ handle_ -> do
+ closeFile (haFO__ handle_) 0{- don't bother flushing-} -- ConcHask: SAFE, won't block
+ return (handle_ { haType__ = ClosedHandle,
+ haFO__ = nullFile__ },
+ "")
+ _ -> do
+ more <- unsafeInterleaveIO (lazyReadLine handle fo)
+ buf <- getBufStart fo bytes -- ConcHask: won't block
+ stToIO (unpackNBytesAccST buf bytes more)
+
+lazyReadChar handle fo = do
+ char <- mayBlock fo (readChar fo) -- ConcHask: UNSAFE, may block.
+ case (char::Int) of
+ -4 -> -- buffering is now block-buffered, use lazyReadBlock instead
+ lazyReadBlock handle fo
+
+ -3 -> -- buffering is now line-buffered, use lazyReadLine instead
+ lazyReadLine handle fo
+ -2 -> return ""
+ -1 -> -- error, silently close handle.
+ withHandle handle $ \ handle_ -> do
+ closeFile (haFO__ handle_) 0{-don't bother flusing-} -- ConcHask: SAFE, won't block
+ return (handle_{ haType__ = ClosedHandle,
+ haFO__ = nullFile__ },
+ "")
+ _ -> do
+ more <- unsafeInterleaveIO (lazyReadChar handle fo)
+ return (chr char : more)
+
+\end{code}
+
+
+%*********************************************************
+%* *
+\subsection{Simple output functions}
+%* *
+%*********************************************************
+
+@hPutChar hdl ch@ writes the character @ch@ to the file
+or channel managed by @hdl@. Characters may be buffered if
+buffering is enabled for @hdl@
+
+\begin{code}
+hPutChar :: Handle -> Char -> IO ()
+hPutChar handle c =
+ wantWriteableHandle "hPutChar" handle $ \ handle_ -> do
+ let fo = haFO__ handle_
+ flushConnectedBuf fo
+ rc <- mayBlock fo (filePutc fo c) -- ConcHask: UNSAFE, may block.
+ if rc == 0
+ then return ()
+ else constructErrorAndFail "hPutChar"
+
+\end{code}
+
+@hPutStr hdl s@ writes the string @s@ to the file or
+channel managed by @hdl@, buffering the output if needs be.
+
+\begin{code}
+hPutStr :: Handle -> String -> IO ()
+hPutStr handle str =
+ wantWriteableHandle "hPutStr" handle $ \ handle_ -> do
+ let fo = haFO__ handle_
+ flushConnectedBuf fo
+ case haBufferMode__ handle_ of
+ LineBuffering -> do
+ buf <- getWriteableBuf fo
+ pos <- getBufWPtr fo
+ bsz <- getBufSize fo
+ writeLines fo buf bsz pos str
+ BlockBuffering _ -> do
+ buf <- getWriteableBuf fo
+ pos <- getBufWPtr fo
+ bsz <- getBufSize fo
+ writeBlocks fo buf bsz pos str
+ NoBuffering -> do
+ writeChars fo str
+\end{code}
+
+Going across the border between Haskell and C is relatively costly,
+so for block writes we pack the character strings on the Haskell-side
+before passing the external write routine a pointer to the buffer.
+
+\begin{code}
+#ifdef __HUGS__
+
+#ifdef __CONCURRENT_HASKELL__
+/* See comment in shoveString below for explanation */
+#warning delayed update of buffer disnae work with killThread
+#endif
+
+#ifndef __PARALLEL_HASKELL__
+writeLines :: ForeignObj -> Addr -> Int -> Int -> String -> IO ()
+#else
+writeLines :: Addr -> Addr -> Int -> Int -> String -> IO ()
+#endif
+writeLines obj buf bufLen initPos s =
+ let
+ shoveString :: Int -> [Char] -> IO ()
+ shoveString n ls =
+ case ls of
+ [] ->
+ {-
+ At the end of a buffer write, update the buffer position
+ in the underlying file object, so that if the handle
+ is subsequently dropped by the program, the whole
+ buffer will be properly flushed.
+
+ There's one case where this delayed up-date of the buffer
+ position can go wrong: if a thread is killed, it might be
+ in the middle of filling up a buffer, with the result that
+ the partial buffer update is lost upon finalisation. Not
+ that killing of threads is supported at the moment.
+
+ -}
+ setBufWPtr obj n
+
+ (x:xs) -> do
+ primWriteCharOffAddr buf n x
+ {- Flushing on buffer exhaustion or newlines (even if it isn't the last one) -}
+ if n == bufLen || x == '\n'
+ then do
+ rc <- mayBlock obj (writeFileObject obj (n + 1)) -- ConcHask: UNSAFE, may block.
+ if rc == 0
+ then shoveString 0 xs
+ else constructErrorAndFail "writeLines"
+ else
+ shoveString (n + 1) xs
+ in
+ shoveString initPos s
+#else /* ndef __HUGS__ */
+#ifndef __PARALLEL_HASKELL__
+writeLines :: ForeignObj -> Addr -> Int -> Int -> String -> IO ()
+#else
+writeLines :: Addr -> Addr -> Int -> Int -> String -> IO ()
+#endif
+writeLines obj buf (I# bufLen) (I# initPos#) s =
+ let
+ write_char :: Addr -> Int# -> Char# -> IO ()
+ write_char (A# buf#) n# c# =
+ IO $ \ s# ->
+ case (writeCharOffAddr# buf# n# c# s#) of s2# -> (# s2#, () #)
+
+ shoveString :: Int# -> [Char] -> IO ()
+ shoveString n ls =
+ case ls of
+ [] ->
+ {-
+ At the end of a buffer write, update the buffer position
+ in the underlying file object, so that if the handle
+ is subsequently dropped by the program, the whole
+ buffer will be properly flushed.
+
+ There's one case where this delayed up-date of the buffer
+ position can go wrong: if a thread is killed, it might be
+ in the middle of filling up a buffer, with the result that
+ the partial buffer update is lost upon finalisation. Not
+ that killing of threads is supported at the moment.
+
+ -}
+ setBufWPtr obj (I# n)
+
+ ((C# x):xs) -> do
+ write_char buf n x
+ {- Flushing on buffer exhaustion or newlines (even if it isn't the last one) -}
+ if n ==# bufLen || x `eqChar#` '\n'#
+ then do
+ rc <- mayBlock obj (writeFileObject obj (I# (n +# 1#))) -- ConcHask: UNSAFE, may block.
+ if rc == 0
+ then shoveString 0# xs
+ else constructErrorAndFail "writeLines"
+ else
+ shoveString (n +# 1#) xs
+ in
+ shoveString initPos# s
+#endif /* ndef __HUGS__ */
+
+#ifdef __HUGS__
+#ifndef __PARALLEL_HASKELL__
+writeBlocks :: ForeignObj -> Addr -> Int -> Int -> String -> IO ()
+#else
+writeBlocks :: Addr -> Addr -> Int -> Int -> String -> IO ()
+#endif
+writeBlocks obj buf bufLen initPos s =
+ let
+ shoveString :: Int -> [Char] -> IO ()
+ shoveString n ls =
+ case ls of
+ [] ->
+ {-
+ At the end of a buffer write, update the buffer position
+ in the underlying file object, so that if the handle
+ is subsequently dropped by the program, the whole
+ buffer will be properly flushed.
+
+ There's one case where this delayed up-date of the buffer
+ position can go wrong: if a thread is killed, it might be
+ in the middle of filling up a buffer, with the result that
+ the partial buffer update is lost upon finalisation. However,
+ by the time killThread is supported, Haskell finalisers are also
+ likely to be in, which means the 'IOFileObject' hack can go
+ alltogether.
+
+ -}
+ setBufWPtr obj n
+
+ (x:xs) -> do
+ primWriteCharOffAddr buf n x
+ if n == bufLen
+ then do
+ rc <- mayBlock obj (writeFileObject obj (n + 1)) -- ConcHask: UNSAFE, may block.
+ if rc == 0
+ then shoveString 0 xs
+ else constructErrorAndFail "writeChunks"
+ else
+ shoveString (n + 1) xs
+ in
+ shoveString initPos s
+#else /* ndef __HUGS__ */
+#ifndef __PARALLEL_HASKELL__
+writeBlocks :: ForeignObj -> Addr -> Int -> Int -> String -> IO ()
+#else
+writeBlocks :: Addr -> Addr -> Int -> Int -> String -> IO ()
+#endif
+writeBlocks obj buf (I# bufLen) (I# initPos#) s =
+ let
+ write_char :: Addr -> Int# -> Char# -> IO ()
+ write_char (A# buf#) n# c# =
+ IO $ \ s# ->
+ case (writeCharOffAddr# buf# n# c# s#) of s2# -> (# s2#, () #)
+
+ shoveString :: Int# -> [Char] -> IO ()
+ shoveString n ls =
+ case ls of
+ [] ->
+ {-
+ At the end of a buffer write, update the buffer position
+ in the underlying file object, so that if the handle
+ is subsequently dropped by the program, the whole
+ buffer will be properly flushed.
+
+ There's one case where this delayed up-date of the buffer
+ position can go wrong: if a thread is killed, it might be
+ in the middle of filling up a buffer, with the result that
+ the partial buffer update is lost upon finalisation. However,
+ by the time killThread is supported, Haskell finalisers are also
+ likely to be in, which means the 'IOFileObject' hack can go
+ alltogether.
+
+ -}
+ setBufWPtr obj (I# n)
+
+ ((C# x):xs) -> do
+ write_char buf n x
+ if n ==# bufLen
+ then do
+ rc <- mayBlock obj (writeFileObject obj (I# (n +# 1#))) -- ConcHask: UNSAFE, may block.
+ if rc == 0
+ then shoveString 0# xs
+ else constructErrorAndFail "writeChunks"
+ else
+ shoveString (n +# 1#) xs
+ in
+ shoveString initPos# s
+#endif /* ndef __HUGS__ */
+
+#ifndef __PARALLEL_HASKELL__
+writeChars :: ForeignObj -> String -> IO ()
+#else
+writeChars :: Addr -> String -> IO ()
+#endif
+writeChars _fo "" = return ()
+writeChars fo (c:cs) = do
+ rc <- mayBlock fo (filePutc fo c) -- ConcHask: UNSAFE, may block.
+ if rc == 0
+ then writeChars fo cs
+ else constructErrorAndFail "writeChars"
+
+\end{code}
+
+Computation @hPrint hdl t@ writes the string representation of {\em t}
+given by the @shows@ function to the file or channel managed by {\em
+hdl}.
+
+[ Seem to have disappeared from the 1.4 interface - SOF 2/97 ]
+
+\begin{code}
+hPrint :: Show a => Handle -> a -> IO ()
+hPrint hdl = hPutStrLn hdl . show
+\end{code}
+
+Derived action @hPutStrLn hdl str@ writes the string \tr{str} to
+the handle \tr{hdl}, adding a newline at the end.
+
+\begin{code}
+hPutStrLn :: Handle -> String -> IO ()
+hPutStrLn hndl str = do
+ hPutStr hndl str
+ hPutChar hndl '\n'
+\end{code}