X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=System%2FIO.hs;h=0179d8df5e19c531593e35cb4be1e45c1a14b2f3;hb=6b1a36a595eddf1e124529646afdb75c76a9966d;hp=d6bc1eede63f86f052d36cf1e10d6cd30f3d7cc6;hpb=a3e56f82973d7117fe4544e5702d1c0180ae7d79;p=haskell-directory.git diff --git a/System/IO.hs b/System/IO.hs index d6bc1ee..0179d8d 100644 --- a/System/IO.hs +++ b/System/IO.hs @@ -1,4 +1,4 @@ -{-# OPTIONS -fno-implicit-prelude #-} +{-# OPTIONS_GHC -fno-implicit-prelude #-} ----------------------------------------------------------------------------- -- | -- Module : System.IO @@ -6,7 +6,7 @@ -- License : BSD-style (see the file libraries/base/LICENSE) -- -- Maintainer : libraries@haskell.org --- Stability : provisional +-- Stability : stable -- Portability : portable -- -- The standard IO library. @@ -14,64 +14,125 @@ ----------------------------------------------------------------------------- module System.IO ( + -- * The IO monad + + IO, -- instance MonadFix + fixIO, -- :: (a -> IO a) -> IO a + + -- * Files and handles + + FilePath, -- :: String + Handle, -- abstract, instance of: Eq, Show. - HandlePosn(..), -- abstract, instance of: Eq, Show. - IOMode(ReadMode,WriteMode,AppendMode,ReadWriteMode), - BufferMode(NoBuffering,LineBuffering,BlockBuffering), - SeekMode(AbsoluteSeek,RelativeSeek,SeekFromEnd), + -- ** Standard handles + + -- | Three handles are allocated during program initialisation, + -- and are initially open. stdin, stdout, stderr, -- :: Handle + -- * Opening and closing files + + -- ** Opening files + + withFile, openFile, -- :: FilePath -> IOMode -> IO Handle + IOMode(ReadMode,WriteMode,AppendMode,ReadWriteMode), + + -- ** Closing files + hClose, -- :: Handle -> IO () + + -- ** Special cases + + -- | These functions are also exported by the "Prelude". + + readFile, -- :: FilePath -> IO String + writeFile, -- :: FilePath -> String -> IO () + appendFile, -- :: FilePath -> String -> IO () + + -- ** File locking + + -- $locking + + -- * Operations on handles + + -- ** Determining and changing the size of a file + hFileSize, -- :: Handle -> IO Integer +#ifdef __GLASGOW_HASKELL__ + hSetFileSize, -- :: Handle -> Integer -> IO () +#endif + + -- ** Detecting the end of input + hIsEOF, -- :: Handle -> IO Bool isEOF, -- :: IO Bool + -- ** Buffering operations + + BufferMode(NoBuffering,LineBuffering,BlockBuffering), hSetBuffering, -- :: Handle -> BufferMode -> IO () hGetBuffering, -- :: Handle -> IO BufferMode hFlush, -- :: Handle -> IO () + + -- ** Repositioning handles + hGetPosn, -- :: Handle -> IO HandlePosn hSetPosn, -- :: HandlePosn -> IO () + HandlePosn, -- abstract, instance of: Eq, Show. + hSeek, -- :: Handle -> SeekMode -> Integer -> IO () + SeekMode(AbsoluteSeek,RelativeSeek,SeekFromEnd), #if !defined(__NHC__) hTell, -- :: Handle -> IO Integer #endif + + -- ** Handle properties + + hIsOpen, hIsClosed, -- :: Handle -> IO Bool + hIsReadable, hIsWritable, -- :: Handle -> IO Bool + hIsSeekable, -- :: Handle -> IO Bool + + -- ** Terminal operations + +#if !defined(__NHC__) + hIsTerminalDevice, -- :: Handle -> IO Bool + + hSetEcho, -- :: Handle -> Bool -> IO () + hGetEcho, -- :: Handle -> IO Bool +#endif + + -- ** Showing handle state + +#ifdef __GLASGOW_HASKELL__ + hShow, -- :: Handle -> IO String +#endif + + -- * Text input and output + + -- ** Text input + hWaitForInput, -- :: Handle -> Int -> IO Bool hReady, -- :: Handle -> IO Bool hGetChar, -- :: Handle -> IO Char hGetLine, -- :: Handle -> IO [Char] hLookAhead, -- :: Handle -> IO Char hGetContents, -- :: Handle -> IO [Char] + + -- ** Text output + hPutChar, -- :: Handle -> Char -> IO () hPutStr, -- :: Handle -> [Char] -> IO () hPutStrLn, -- :: Handle -> [Char] -> IO () hPrint, -- :: Show a => Handle -> a -> IO () - hIsOpen, hIsClosed, -- :: Handle -> IO Bool - hIsReadable, hIsWritable, -- :: Handle -> IO Bool - hIsSeekable, -- :: Handle -> IO Bool - - isAlreadyExistsError, isDoesNotExistError, -- :: IOError -> Bool - isAlreadyInUseError, isFullError, - isEOFError, isIllegalOperation, - isPermissionError, isUserError, - ioeGetErrorString, -- :: IOError -> String - ioeGetHandle, -- :: IOError -> Maybe Handle - ioeGetFileName, -- :: IOError -> Maybe FilePath + -- ** Special cases for standard input and output - try, -- :: IO a -> IO (Either IOError a) + -- | These functions are also exported by the "Prelude". - -- re-exports of Prelude names - IO, -- instance MonadFix - FilePath, -- :: String - IOError, - ioError, -- :: IOError -> IO a - userError, -- :: String -> IOError - catch, -- :: IO a -> (IOError -> IO a) -> IO a interact, -- :: (String -> String) -> IO () - putChar, -- :: Char -> IO () putStr, -- :: String -> IO () putStrLn, -- :: String -> IO () @@ -79,24 +140,26 @@ module System.IO ( getChar, -- :: IO Char getLine, -- :: IO String getContents, -- :: IO String - readFile, -- :: FilePath -> IO String - writeFile, -- :: FilePath -> String -> IO () - appendFile, -- :: FilePath -> String -> IO () readIO, -- :: Read a => String -> IO a readLn, -- :: Read a => IO a -#if !defined(__HUGS__) && !defined(__NHC__) + -- * Binary input and output + + withBinaryFile, + openBinaryFile, -- :: FilePath -> IOMode -> IO Handle + hSetBinaryMode, -- :: Handle -> Bool -> IO () hPutBuf, -- :: Handle -> Ptr a -> Int -> IO () hGetBuf, -- :: Handle -> Ptr a -> Int -> IO Int +#if !defined(__NHC__) && !defined(__HUGS__) + hPutBufNonBlocking, -- :: Handle -> Ptr a -> Int -> IO Int + hGetBufNonBlocking, -- :: Handle -> Ptr a -> Int -> IO Int #endif - - fixIO, -- :: (a -> IO a) -> IO a -#if !defined(__HUGS__) && !defined(__NHC__) - hSetEcho, -- :: Handle -> Bool -> IO () - hGetEcho, -- :: Handle -> IO Bool + -- * Temporary files (not portable: GHC only) - hIsTerminalDevice, -- :: Handle -> IO Bool +#ifdef __GLASGOW_HASKELL__ + openTempFile, + openBinaryTempFile, #endif ) where @@ -105,7 +168,6 @@ import GHC.Base import GHC.IOBase -- Together these four Prelude modules define import GHC.Handle -- all the stuff exported by IO for the GHC version import GHC.IO -import GHC.ST ( fixST ) import GHC.Exception import GHC.Num import GHC.Read @@ -115,6 +177,10 @@ import GHC.Show #ifdef __HUGS__ import Hugs.IO import Hugs.IOExts +import Hugs.IORef +import Hugs.Prelude ( throw, Exception(NonTermination) ) +import Control.Exception ( bracket ) +import System.IO.Unsafe ( unsafeInterleaveIO ) #endif #ifdef __NHC__ @@ -143,80 +209,119 @@ import IO , hGetContents -- :: Handle -> IO [Char] , hPutChar -- :: Handle -> Char -> IO () , hPutStr -- :: Handle -> [Char] -> IO () + , hPutStrLn -- :: Handle -> [Char] -> IO () + , hPrint -- :: Handle -> [Char] -> IO () + , hReady -- :: Handle -> [Char] -> IO () , hIsOpen, hIsClosed -- :: Handle -> IO Bool , hIsReadable, hIsWritable -- :: Handle -> IO Bool , hIsSeekable -- :: Handle -> IO Bool - , isAlreadyExistsError, isDoesNotExistError -- :: IOError -> Bool - , isAlreadyInUseError, isFullError - , isEOFError, isIllegalOperation - , isPermissionError, isUserError - , ioeGetErrorString -- :: IOError -> String - , ioeGetHandle -- :: IOError -> Maybe Handle - , ioeGetFileName -- :: IOError -> Maybe FilePath + , bracket , IO () , FilePath -- :: String - , IOError - , ioError -- :: IOError -> IO a - , userError -- :: String -> IOError - , catch -- :: IO a -> (IOError -> IO a) -> IO a ) -import NHC.Internal (unsafePerformIO) +import NHC.IOExtras (fixIO, hPutBuf, hGetBuf) +import NHC.FFI (Ptr) #endif -import System.IO.Error - -- ----------------------------------------------------------------------------- -- Standard IO -#ifndef __HUGS__ +#ifdef __GLASGOW_HASKELL__ +-- | Write a character to the standard output device +-- (same as 'hPutChar' 'stdout'). + putChar :: Char -> IO () putChar c = hPutChar stdout c +-- | Write a string to the standard output device +-- (same as 'hPutStr' 'stdout'). + putStr :: String -> IO () putStr s = hPutStr stdout s +-- | The same as 'putStr', but adds a newline character. + putStrLn :: String -> IO () putStrLn s = do putStr s putChar '\n' +-- | The 'print' function outputs a value of any printable type to the +-- standard output device. +-- Printable types are those that are instances of class 'Show'; 'print' +-- converts values to strings for output using the 'show' operation and +-- adds a newline. +-- +-- For example, a program to print the first 20 integers and their +-- powers of 2 could be written as: +-- +-- > main = print ([(n, 2^n) | n <- [0..19]]) + print :: Show a => a -> IO () print x = putStrLn (show x) +-- | Read a character from the standard input device +-- (same as 'hGetChar' 'stdin'). + getChar :: IO Char getChar = hGetChar stdin +-- | Read a line from the standard input device +-- (same as 'hGetLine' 'stdin'). + getLine :: IO String getLine = hGetLine stdin +-- | The 'getContents' operation returns all user input as a single string, +-- which is read lazily as it is needed +-- (same as 'hGetContents' 'stdin'). + getContents :: IO String getContents = hGetContents stdin +-- | The 'interact' function takes a function of type @String->String@ +-- as its argument. The entire input from the standard input device is +-- passed to this function as its argument, and the resulting string is +-- output on the standard output device. + interact :: (String -> String) -> IO () interact f = do s <- getContents putStr (f s) +-- | The 'readFile' function reads a file and +-- returns the contents of the file as a string. +-- The file is read lazily, on demand, as with 'getContents'. + 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 +-- | The computation 'writeFile' @file str@ function writes the string @str@, +-- to the file @file@. +writeFile :: FilePath -> String -> IO () +writeFile f txt = withFile f WriteMode (\ hdl -> hPutStr hdl txt) + +-- | The computation 'appendFile' @file str@ function appends the string @str@, +-- to the file @file@. +-- +-- Note that 'writeFile' and 'appendFile' write a literal string +-- to a file. To write a value of any printable type, as with 'print', +-- use the 'show' function to convert the value to a string first. +-- +-- > main = appendFile "squares" (show [(x,x*x) | x <- [0,0.1..2]]) appendFile :: FilePath -> String -> IO () -appendFile name str = do - hdl <- openFile name AppendMode - hPutStr hdl str - hClose hdl +appendFile f txt = withFile f AppendMode (\ hdl -> hPutStr hdl txt) + +-- | The 'readLn' function combines 'getLine' and 'readIO'. readLn :: Read a => IO a readLn = do l <- getLine r <- readIO l return r --- raises an exception instead of an error +-- | The 'readIO' function is similar to 'read' except that it signals +-- parse failure to the 'IO' monad instead of terminating the program. + readIO :: Read a => String -> IO a readIO s = case (do { (x,t) <- reads s ; ("","") <- lex t ; @@ -224,27 +329,113 @@ readIO s = case (do { (x,t) <- reads s ; [x] -> return x [] -> ioError (userError "Prelude.readIO: no parse") _ -> ioError (userError "Prelude.readIO: ambiguous parse") -#endif /* __HUGS__ */ +#endif /* __GLASGOW_HASKELL__ */ + +#ifndef __NHC__ +-- | Computation 'hReady' @hdl@ indicates whether at least one item is +-- available for input from handle @hdl@. +-- +-- This operation may fail with: +-- +-- * 'System.IO.Error.isEOFError' if the end of file has been reached. hReady :: Handle -> IO Bool hReady h = hWaitForInput h 0 +-- | The same as 'hPutStr', but adds a newline character. + hPutStrLn :: Handle -> String -> IO () hPutStrLn hndl str = do hPutStr hndl str hPutChar hndl '\n' +-- | Computation 'hPrint' @hdl t@ writes the string representation of @t@ +-- given by the 'shows' function to the file or channel managed by @hdl@ +-- and appends a newline. +-- +-- This operation may fail with: +-- +-- * 'System.IO.Error.isFullError' if the device is full; or +-- +-- * 'System.IO.Error.isPermissionError' if another system resource limit would be exceeded. + hPrint :: Show a => Handle -> a -> IO () hPrint hdl = hPutStrLn hdl . show +#endif /* !__NHC__ */ + +-- | @'withFile' name mode act@ opens a file using 'openFile' and passes +-- the resulting handle to the computation @act@. The handle will be +-- closed on exit from 'withFile', whether by normal termination or by +-- raising an exception. +withFile :: FilePath -> IOMode -> (Handle -> IO r) -> IO r +withFile name mode = bracket (openFile name mode) hClose + +-- | @'withBinaryFile' name mode act@ opens a file using 'openBinaryFile' +-- and passes the resulting handle to the computation @act@. The handle +-- will be closed on exit from 'withBinaryFile', whether by normal +-- termination or by raising an exception. +withBinaryFile :: FilePath -> IOMode -> (Handle -> IO r) -> IO r +withBinaryFile name mode = bracket (openBinaryFile name mode) hClose -- --------------------------------------------------------------------------- -- fixIO -#ifdef __GLASGOW_HASKELL__ -fixIO :: (a -> IO a) -> IO a -fixIO m = stToIO (fixST (ioToST . m)) +#if defined(__GLASGOW_HASKELL__) || defined(__HUGS__) +fixIO :: (a -> IO a) -> IO a +fixIO k = do + ref <- newIORef (throw NonTermination) + ans <- unsafeInterleaveIO (readIORef ref) + result <- k ans + writeIORef ref result + return result + +-- NOTE: we do our own explicit black holing here, because GHC's lazy +-- blackholing isn't enough. In an infinite loop, GHC may run the IO +-- computation a few times before it notices the loop, which is wrong. #endif -#ifdef __NHC__ -fixIO :: (a -> IO a) -> IO a -fixIO f = let x = unsafePerformIO (f x) in return x + +#if defined(__NHC__) +-- Assume a unix platform, where text and binary I/O are identical. +openBinaryFile = openFile +hSetBinaryMode _ _ = return () +#endif + +-- $locking +-- Implementations should enforce as far as possible, at least locally to the +-- Haskell process, multiple-reader single-writer locking on files. +-- That is, /there may either be many handles on the same file which manage +-- input, or just one handle on the file which manages output/. If any +-- open or semi-closed handle is managing a file for output, no new +-- handle can be allocated for that file. If any open or semi-closed +-- handle is managing a file for input, new handles can only be allocated +-- if they do not manage output. Whether two files are the same is +-- implementation-dependent, but they should normally be the same if they +-- have the same absolute path name and neither has been renamed, for +-- example. +-- +-- /Warning/: the 'readFile' operation holds a semi-closed handle on +-- the file until the entire contents of the file have been consumed. +-- It follows that an attempt to write to a file (using 'writeFile', for +-- example) that was earlier opened by 'readFile' will usually result in +-- failure with 'System.IO.Error.isAlreadyInUseError'. + +-- ----------------------------------------------------------------------------- +-- Utils + +#ifdef __GLASGOW_HASKELL__ +-- Copied here to avoid recursive dependency with Control.Exception +bracket + :: IO a -- ^ computation to run first (\"acquire resource\") + -> (a -> IO b) -- ^ computation to run last (\"release resource\") + -> (a -> IO c) -- ^ computation to run in-between + -> IO c -- returns the value from the in-between computation +bracket before after thing = + block (do + a <- before + r <- catchException + (unblock (thing a)) + (\e -> do { after a; throw e }) + after a + return r + ) #endif