/usr/lib/hugs/packages/base/System/IO.hs is in libhugs-base-bundled 98.200609.21-5.3ubuntu1.
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-----------------------------------------------------------------------------
-- |
-- 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 ()
hPutBuf, -- :: Handle -> Ptr a -> Int -> IO ()
hGetBuf, -- :: Handle -> Ptr a -> Int -> IO Int
-- * Temporary files
) where
import Hugs.IO
import Hugs.IOExts
import Hugs.IORef
import Hugs.Prelude ( throw, Exception(NonTermination) )
import System.IO.Unsafe ( unsafeInterleaveIO )
-- -----------------------------------------------------------------------------
-- 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
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