{-# OPTIONS_GHC -fno-implicit-prelude #-} ----------------------------------------------------------------------------- -- | -- Module : System.IO -- Copyright : (c) The University of Glasgow 2001 -- License : BSD-style (see the file libraries/base/LICENSE) -- -- Maintainer : libraries@haskell.org -- Stability : stable -- Portability : portable -- -- The standard IO library. -- ----------------------------------------------------------------------------- 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. -- ** Standard handles -- | Three handles are allocated during program initialisation, -- and are initially open. stdin, stdout, stderr, -- :: Handle -- * Opening and closing files -- ** Opening files 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 -- ** 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), hTell, -- :: Handle -> IO Integer -- ** Handle properties hIsOpen, hIsClosed, -- :: Handle -> IO Bool hIsReadable, hIsWritable, -- :: Handle -> IO Bool hIsSeekable, -- :: Handle -> IO Bool -- ** Terminal operations --hIsTerminalDevice, -- :: Handle -> IO Bool hSetEcho, -- :: Handle -> Bool -> IO () hGetEcho, -- :: Handle -> IO Bool -- ** Showing handle state -- * 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 () -- ** Special cases for standard input and output -- | These functions are also exported by the "Prelude". interact, -- :: (String -> String) -> IO () putChar, -- :: Char -> IO () putStr, -- :: String -> IO () putStrLn, -- :: String -> IO () print, -- :: Show a => a -> IO () getChar, -- :: IO Char getLine, -- :: IO String getContents, -- :: IO String readIO, -- :: Read a => String -> IO a readLn, -- :: Read a => IO a -- * Binary input and output openBinaryFile, -- :: FilePath -> IOMode -> IO Handle hSetBinaryMode, -- :: Handle -> Bool -> IO () withBinaryFile, hPutBuf, -- :: Handle -> Ptr a -> Int -> IO () hGetBuf, -- :: Handle -> Ptr a -> Int -> IO Int -- * Temporary files TextEncoding, utf8, mkTextEncoding ) where import Hugs.IO import Hugs.IOExts import Hugs.IORef import Hugs.Prelude ( throw, Exception(NonTermination) ) import System.IO.Unsafe ( unsafeInterleaveIO ) import Control.Exception(bracket) -- ----------------------------------------------------------------------------- -- Standard IO -- | 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 -- --------------------------------------------------------------------------- -- fixIO 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. -- $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 ---- withBinaryFile :: FilePath -> IOMode -> (Handle -> IO r) -> IO r withBinaryFile name mode = bracket (openBinaryFile name mode) hClose data TextEncoding utf8 :: TextEncoding utf8 = undefined mkTextEncoding = undefined :: String -> IO TextEncoding
(HTML for this module was generated on 2013-11-21. About the conversion tool.)