ioe_closedHandle, ioe_EOF, ioe_notReadable, ioe_notWritable,
stdin, stdout, stderr,
- IOMode(..), IOModeEx(..), openFile, openFileEx, openFd, fdToHandle,
+ IOMode(..), openFile, openBinaryFile, openFd, fdToHandle,
hFileSize, hIsEOF, isEOF, hLookAhead, hSetBuffering, hSetBinaryMode,
hFlush, hDuplicate, hDuplicateTo,
hIsOpen, hIsClosed, hIsReadable, hIsWritable, hGetBuffering, hIsSeekable,
hSetEcho, hGetEcho, hIsTerminalDevice,
+ hShow,
+
#ifdef DEBUG_DUMP
puts,
#endif
-- ---------------------------------------------------------------------------
-- Creating a new handle
-newFileHandle :: (MVar Handle__ -> IO ()) -> Handle__ -> IO Handle
-newFileHandle finalizer hc = do
+newFileHandle :: FilePath -> (MVar Handle__ -> IO ()) -> Handle__ -> IO Handle
+newFileHandle filepath finalizer hc = do
m <- newMVar hc
addMVarFinalizer m (finalizer m)
- return (FileHandle m)
+ return (FileHandle filepath m)
-- ---------------------------------------------------------------------------
-- Working with Handles
{-# INLINE withHandle #-}
withHandle :: String -> Handle -> (Handle__ -> IO (Handle__,a)) -> IO a
-withHandle fun h@(FileHandle m) act = withHandle' fun h m act
-withHandle fun h@(DuplexHandle m _) act = withHandle' fun h m act
+withHandle fun h@(FileHandle _ m) act = withHandle' fun h m act
+withHandle fun h@(DuplexHandle _ m _) act = withHandle' fun h m act
withHandle' :: String -> Handle -> MVar Handle__
-> (Handle__ -> IO (Handle__,a)) -> IO a
(h',v) <- catchException (act h_)
(\ err -> putMVar m h_ >>
case err of
- IOException ex -> ioError (augmentIOError ex fun h h_)
- _ -> throw err)
+ IOException ex -> ioError (augmentIOError ex fun h)
+ _ -> throw err)
checkBufferInvariants h'
putMVar m h'
return v
{-# INLINE withHandle_ #-}
withHandle_ :: String -> Handle -> (Handle__ -> IO a) -> IO a
-withHandle_ fun h@(FileHandle m) act = withHandle_' fun h m act
-withHandle_ fun h@(DuplexHandle m _) act = withHandle_' fun h m act
+withHandle_ fun h@(FileHandle _ m) act = withHandle_' fun h m act
+withHandle_ fun h@(DuplexHandle _ m _) act = withHandle_' fun h m act
withHandle_' fun h m act =
block $ do
v <- catchException (act h_)
(\ err -> putMVar m h_ >>
case err of
- IOException ex -> ioError (augmentIOError ex fun h h_)
- _ -> throw err)
+ IOException ex -> ioError (augmentIOError ex fun h)
+ _ -> throw err)
checkBufferInvariants h_
putMVar m h_
return v
withAllHandles__ :: String -> Handle -> (Handle__ -> IO Handle__) -> IO ()
-withAllHandles__ fun h@(FileHandle m) act = withHandle__' fun h m act
-withAllHandles__ fun h@(DuplexHandle r w) act = do
+withAllHandles__ fun h@(FileHandle _ m) act = withHandle__' fun h m act
+withAllHandles__ fun h@(DuplexHandle _ r w) act = do
withHandle__' fun h r act
withHandle__' fun h w act
h' <- catchException (act h_)
(\ err -> putMVar m h_ >>
case err of
- IOException ex -> ioError (augmentIOError ex fun h h_)
- _ -> throw err)
+ IOException ex -> ioError (augmentIOError ex fun h)
+ _ -> throw err)
checkBufferInvariants h'
putMVar m h'
return ()
-augmentIOError (IOError _ iot _ str fp) fun h h_
+augmentIOError (IOError _ iot _ str fp) fun h
= IOError (Just h) iot fun str filepath
- where filepath | Just _ <- fp = fp
- | otherwise = Just (haFilePath h_)
+ where filepath
+ | Just _ <- fp = fp
+ | otherwise = case h of
+ FileHandle fp _ -> Just fp
+ DuplexHandle fp _ _ -> Just fp
-- ---------------------------------------------------------------------------
-- Wrapper for write operations.
wantWritableHandle :: String -> Handle -> (Handle__ -> IO a) -> IO a
-wantWritableHandle fun h@(FileHandle m) act
+wantWritableHandle fun h@(FileHandle _ m) act
= wantWritableHandle' fun h m act
-wantWritableHandle fun h@(DuplexHandle _ m) act
+wantWritableHandle fun h@(DuplexHandle _ _ m) act
= wantWritableHandle' fun h m act
-- ToDo: in the Duplex case, we don't need to checkWritableHandle
-- Wrapper for read operations.
wantReadableHandle :: String -> Handle -> (Handle__ -> IO a) -> IO a
-wantReadableHandle fun h@(FileHandle m) act
+wantReadableHandle fun h@(FileHandle _ m) act
= wantReadableHandle' fun h m act
-wantReadableHandle fun h@(DuplexHandle m _) act
+wantReadableHandle fun h@(DuplexHandle _ m _) act
= wantReadableHandle' fun h m act
-- ToDo: in the Duplex case, we don't need to checkReadableHandle
-- Wrapper for seek operations.
wantSeekableHandle :: String -> Handle -> (Handle__ -> IO a) -> IO a
-wantSeekableHandle fun h@(DuplexHandle _ _) _act =
+wantSeekableHandle fun h@(DuplexHandle _ _ _) _act =
ioException (IOError (Just h) IllegalOperation fun
"handle is not seekable" Nothing)
-wantSeekableHandle fun h@(FileHandle m) act =
+wantSeekableHandle fun h@(FileHandle _ m) act =
withHandle_' fun h m (checkSeekableHandle act)
checkSeekableHandle act handle_ =
fd_stdout = 1 :: FD
fd_stderr = 2 :: FD
+-- | A handle managing input from the Haskell program's standard input channel.
stdin :: Handle
stdin = unsafePerformIO $ do
-- ToDo: acquire lock
(buf, bmode) <- getBuffer fd_stdin ReadBuffer
mkStdHandle fd_stdin "<stdin>" ReadHandle buf bmode
+-- | A handle managing output to the Haskell program's standard output channel.
stdout :: Handle
stdout = unsafePerformIO $ do
-- ToDo: acquire lock
(buf, bmode) <- getBuffer fd_stdout WriteBuffer
mkStdHandle fd_stdout "<stdout>" WriteHandle buf bmode
+-- | A handle managing output to the Haskell program's standard error channel.
stderr :: Handle
stderr = unsafePerformIO $ do
-- ToDo: acquire lock
-- ---------------------------------------------------------------------------
-- Opening and Closing Files
-{-
-Computation `openFile file mode' allocates and returns a new, open
-handle to manage the file `file'. It manages input if `mode'
-is `ReadMode', output if `mode' is `WriteMode' or `AppendMode',
-and both input and output if mode is `ReadWriteMode'.
-
-If the file does not exist and it is opened for output, it should be
-created as a new file. If `mode' is `WriteMode' and the file
-already exists, then it should be truncated to zero length. The
-handle is positioned at the end of the file if `mode' is
-`AppendMode', and otherwise at the beginning (in which case its
-internal position is 0).
-
-Implementations should enforce, locally to the Haskell process,
-multiple-reader single-writer locking on files, which is to say that
-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.
-
-Two files are the same if they have the same absolute name. An
-implementation is free to impose stricter conditions.
--}
-
-data IOModeEx
- = BinaryMode IOMode
- | TextMode IOMode
- deriving (Eq, Read, Show)
-
addFilePathToIOError fun fp (IOError h iot _ str _)
= IOError h iot fun str (Just fp)
+-- | Computation 'openFile' @file mode@ allocates and returns a new, open
+-- handle to manage the file @file@. It manages input if @mode@
+-- is 'ReadMode', output if @mode@ is 'WriteMode' or 'AppendMode',
+-- and both input and output if mode is 'ReadWriteMode'.
+--
+-- If the file does not exist and it is opened for output, it should be
+-- created as a new file. If @mode@ is 'WriteMode' and the file
+-- already exists, then it should be truncated to zero length.
+-- Some operating systems delete empty files, so there is no guarantee
+-- that the file will exist following an 'openFile' with @mode@
+-- 'WriteMode' unless it is subsequently written to successfully.
+-- The handle is positioned at the end of the file if `mode' is
+-- `AppendMode', and otherwise at the beginning (in which case its
+-- internal position is 0).
+-- The initial buffer mode is implementation-dependent.
+--
+-- This operation may fail with:
+--
+-- * 'isAlreadyInUseError' if the file is already open and cannot be reopened;
+--
+-- * 'isDoesNotExistError' if the file does not exist; or
+--
+-- * 'isPermissionError' if the user does not have permission to open the file.
+
openFile :: FilePath -> IOMode -> IO Handle
openFile fp im =
catch
- (openFile' fp (if dEFAULT_OPEN_IN_BINARY_MODE
- then BinaryMode im
- else TextMode im))
+ (openFile' fp im dEFAULT_OPEN_IN_BINARY_MODE)
(\e -> ioError (addFilePathToIOError "openFile" fp e))
-openFileEx :: FilePath -> IOModeEx -> IO Handle
-openFileEx fp m =
+-- | Like 'openFile', but open the file in binary mode.
+-- On Windows, reading a file in text mode (which is the default)
+-- will translate CRLF to LF, and writing will translate LF to CRLF.
+-- This is usually what you want with text files. With binary files
+-- this is undesirable; also, as usual under Microsoft operating systems,
+-- text mode treats control-Z as EOF. Binary mode turns off all special
+-- treatment of end-of-line and end-of-file characters.
+-- (See also 'hSetBinaryMode'.)
+
+openBinaryFile :: FilePath -> IOMode -> IO Handle
+openBinaryFile fp m =
catch
- (openFile' fp m)
- (\e -> ioError (addFilePathToIOError "openFileEx" fp e))
-
+ (openFile' fp m True)
+ (\e -> ioError (addFilePathToIOError "openBinaryFile" fp e))
-openFile' filepath ex_mode =
+openFile' filepath mode binary =
withCString filepath $ \ f ->
let
- (mode, binary) =
- case ex_mode of
- BinaryMode bmo -> (bmo, True)
- TextMode tmo -> (tmo, False)
-
oflags1 = case mode of
ReadMode -> read_flags
WriteMode -> write_flags
-> IO Handle
mkStdHandle fd filepath ha_type buf bmode = do
spares <- newIORef BufferListNil
- newFileHandle stdHandleFinalizer
+ newFileHandle filepath stdHandleFinalizer
(Handle__ { haFD = fd,
haType = ha_type,
haIsBin = dEFAULT_OPEN_IN_BINARY_MODE,
haIsStream = False,
haBufferMode = bmode,
- haFilePath = filepath,
haBuffer = buf,
haBuffers = spares,
haOtherSide = Nothing
mkFileHandle fd is_stream filepath ha_type binary = do
(buf, bmode) <- getBuffer fd (initBufferState ha_type)
spares <- newIORef BufferListNil
- newFileHandle handleFinalizer
+ newFileHandle filepath handleFinalizer
(Handle__ { haFD = fd,
haType = ha_type,
haIsBin = binary,
haIsStream = is_stream,
haBufferMode = bmode,
- haFilePath = filepath,
haBuffer = buf,
haBuffers = spares,
haOtherSide = Nothing
haIsBin = binary,
haIsStream = is_stream,
haBufferMode = w_bmode,
- haFilePath = filepath,
haBuffer = w_buf,
haBuffers = w_spares,
haOtherSide = Nothing
haIsBin = binary,
haIsStream = is_stream,
haBufferMode = r_bmode,
- haFilePath = filepath,
haBuffer = r_buf,
haBuffers = r_spares,
haOtherSide = Just write_side
read_side <- newMVar r_handle_
addMVarFinalizer write_side (handleFinalizer write_side)
- return (DuplexHandle read_side write_side)
+ return (DuplexHandle filepath read_side write_side)
initBufferState ReadHandle = ReadBuffer
-- ---------------------------------------------------------------------------
-- Closing a handle
--- Computation `hClose hdl' makes handle `hdl' closed. Before the
--- computation finishes, any items buffered for output and not already
--- sent to the operating system are flushed as for `hFlush'.
-
--- For a duplex handle, we close&flush the write side, and just close
--- the read side.
+-- | Computation 'hClose' @hdl@ makes handle @hdl@ closed. Before the
+-- computation finishes, if @hdl@ is writable its buffer is flushed as
+-- for 'hFlush'.
+-- Performing 'hClose' on a handle that has already been closed has no effect;
+-- doing so not an error. All other operations on a closed handle will fail.
+-- If 'hClose' fails for any reason, any further operations (apart from
+-- 'hClose') on the handle will still fail as if @hdl@ had been successfully
+-- closed.
hClose :: Handle -> IO ()
-hClose h@(FileHandle m) = hClose' h m
-hClose h@(DuplexHandle r w) = hClose' h w >> hClose' h r
+hClose h@(FileHandle _ m) = hClose' h m
+hClose h@(DuplexHandle _ r w) = hClose' h w >> hClose' h r
hClose' h m = withHandle__' "hClose" h m $ hClose_help
-----------------------------------------------------------------------------
-- Detecting the size of a file
--- For a handle `hdl' which attached to a physical file, `hFileSize
--- hdl' returns the size of `hdl' in terms of the number of items
--- which can be read from `hdl'.
+-- | For a handle @hdl@ which attached to a physical file,
+-- 'hFileSize' @hdl@ returns the size of that file in 8-bit bytes.
hFileSize :: Handle -> IO Integer
hFileSize handle =
-- ---------------------------------------------------------------------------
-- Detecting the End of Input
--- For a readable handle `hdl', `hIsEOF hdl' returns
--- `True' if no further input can be taken from `hdl' or for a
--- physical file, if the current I/O position is equal to the length of
--- the file. Otherwise, it returns `False'.
+-- | For a readable handle @hdl@, 'hIsEOF' @hdl@ returns
+-- 'True' if no further input can be taken from @hdl@ or for a
+-- physical file, if the current I\/O position is equal to the length of
+-- the file. Otherwise, it returns 'False'.
hIsEOF :: Handle -> IO Bool
hIsEOF handle =
(do hLookAhead handle; return False)
(\e -> if isEOFError e then return True else ioError e)
+-- | The computation 'isEOF' is identical to 'hIsEOF',
+-- except that it works only on 'stdin'.
+
isEOF :: IO Bool
isEOF = hIsEOF stdin
-- ---------------------------------------------------------------------------
-- Looking ahead
--- hLookahead returns the next character from the handle without
--- removing it from the input buffer, blocking until a character is
--- available.
+-- | Computation 'hLookahead' returns the next character from the handle
+-- without removing it from the input buffer, blocking until a character
+-- is available.
+--
+-- This operation may fail with:
+--
+-- * 'isEOFError' if the end of file has been reached.
hLookAhead :: Handle -> IO Char
hLookAhead handle = do
-- block-buffering or no-buffering. See GHC.IOBase for definition and
-- further explanation of what the type represent.
--- Computation `hSetBuffering hdl mode' sets the mode of buffering for
+-- | Computation 'hSetBuffering' @hdl mode@ sets the mode of buffering for
-- handle hdl on subsequent reads and writes.
--
--- * If mode is LineBuffering, line-buffering should be enabled if possible.
+-- If the buffer mode is changed from 'BlockBuffering' or
+-- 'LineBuffering' to 'NoBuffering', then
--
--- * If mode is `BlockBuffering size', then block-buffering
--- should be enabled if possible. The size of the buffer is n items
--- if size is `Just n' and is otherwise implementation-dependent.
+-- * if @hdl@ is writable, the buffer is flushed as for 'hFlush';
--
--- * If mode is NoBuffering, then buffering is disabled if possible.
-
--- If the buffer mode is changed from BlockBuffering or
--- LineBuffering to NoBuffering, then any items in the output
--- buffer are written to the device, and any items in the input buffer
--- are discarded. The default buffering mode when a handle is opened
--- is implementation-dependent and may depend on the object which is
--- attached to that handle.
+-- * if @hdl@ is not writable, the contents of the buffer is discarded.
+--
+-- This operation may fail with:
+--
+-- * 'isPermissionError' if the handle has already been used for reading
+-- or writing and the implementation does not allow the buffering mode
+-- to be changed.
hSetBuffering :: Handle -> BufferMode -> IO ()
hSetBuffering handle mode =
-- -----------------------------------------------------------------------------
-- hFlush
--- The action `hFlush hdl' causes any items buffered for output
--- in handle `hdl' to be sent immediately to the operating
--- system.
+-- | The action 'hFlush' @hdl@ causes any items buffered for output
+-- in handle `hdl' to be sent immediately to the operating system.
+--
+-- This operation may fail with:
+--
+-- * 'isFullError' if the device is full;
+--
+-- * 'isPermissionError' if a system resource limit would be exceeded.
+-- It is unspecified whether the characters in the buffer are discarded
+-- or retained under these circumstances.
hFlush :: Handle -> IO ()
hFlush handle =
-- that reports the position back via (merely) an Int.
type HandlePosition = Integer
--- Computation `hGetPosn hdl' returns the current I/O position of
--- `hdl' as an abstract position. Computation `hSetPosn p' sets the
--- position of `hdl' to a previously obtained position `p'.
+-- | Computation 'hGetPosn' @hdl@ returns the current I\/O position of
+-- @hdl@ as a value of the abstract type 'HandlePosn'.
hGetPosn :: Handle -> IO HandlePosn
hGetPosn handle = do
posn <- hTell handle
return (HandlePosn handle posn)
+-- | If a call to 'hGetPosn' @hdl@ returns a position @p@,
+-- then computation 'hSetPosn' @p@ sets the position of @hdl@
+-- to the position it held at the time of the call to 'hGetPosn'.
+--
+-- This operation may fail with:
+--
+-- * 'isPermissionError' if a system resource limit would be exceeded.
+
hSetPosn :: HandlePosn -> IO ()
hSetPosn (HandlePosn h i) = hSeek h AbsoluteSeek i
-- ---------------------------------------------------------------------------
-- hSeek
-{-
-The action `hSeek hdl mode i' sets the position of handle
-`hdl' depending on `mode'. If `mode' is
-
- * AbsoluteSeek - The position of `hdl' is set to `i'.
- * RelativeSeek - The position of `hdl' is set to offset `i' from
- the current position.
- * SeekFromEnd - The position of `hdl' is set to offset `i' from
- the end of the file.
-
-Some handles may not be seekable (see `hIsSeekable'), or only
-support a subset of the possible positioning operations (e.g. it may
-only be possible to seek to the end of a tape, or to a positive
-offset from the beginning or current position).
-
-It is not possible to set a negative I/O position, or for a physical
-file, an I/O position beyond the current end-of-file.
+-- | A mode that determines the effect of 'hSeek' @hdl mode i@, as follows:
+data SeekMode
+ = AbsoluteSeek -- ^ the position of @hdl@ is set to @i@.
+ | RelativeSeek -- ^ the position of @hdl@ is set to offset @i@
+ -- from the current position.
+ | SeekFromEnd -- ^ the position of @hdl@ is set to offset @i@
+ -- from the end of the file.
+ deriving (Eq, Ord, Ix, Enum, Read, Show)
-Note:
+{- Note:
- when seeking using `SeekFromEnd', positive offsets (>=0) means
seeking at or past EOF.
clear here.
-}
-data SeekMode = AbsoluteSeek | RelativeSeek | SeekFromEnd
- deriving (Eq, Ord, Ix, Enum, Read, Show)
+-- | Computation 'hSeek' @hdl mode i@ sets the position of handle
+-- @hdl@ depending on @mode@.
+-- The offset @i@ is given in terms of 8-bit bytes.
+--
+-- If @hdl@ is block- or line-buffered, then seeking to a position which is not
+-- in the current buffer will first cause any items in the output buffer to be
+-- written to the device, and then cause the input buffer to be discarded.
+-- Some handles may not be seekable (see 'hIsSeekable'), or only support a
+-- subset of the possible positioning operations (for instance, it may only
+-- be possible to seek to the end of a tape, or to a positive offset from
+-- the beginning or current position).
+-- It is not possible to set a negative I\/O position, or for
+-- a physical file, an I\/O position beyond the current end-of-file.
+--
+-- This operation may fail with:
+--
+-- * 'isPermissionError' if a system resource limit would be exceeded.
hSeek :: Handle -> SeekMode -> Integer -> IO ()
hSeek handle mode offset =
-}
hIsReadable :: Handle -> IO Bool
-hIsReadable (DuplexHandle _ _) = return True
+hIsReadable (DuplexHandle _ _ _) = return True
hIsReadable handle =
withHandle_ "hIsReadable" handle $ \ handle_ -> do
case haType handle_ of
htype -> return (isReadableHandleType htype)
hIsWritable :: Handle -> IO Bool
-hIsWritable (DuplexHandle _ _) = return False
+hIsWritable (DuplexHandle _ _ _) = return True
hIsWritable handle =
withHandle_ "hIsWritable" handle $ \ handle_ -> do
case haType handle_ of
SemiClosedHandle -> ioe_closedHandle
htype -> return (isWritableHandleType htype)
--- Querying how a handle buffers its data:
+-- | Computation 'hGetBuffering' @hdl@ returns the current buffering mode
+-- for @hdl@.
hGetBuffering :: Handle -> IO BufferMode
hGetBuffering handle =
|| tEXT_MODE_SEEK_ALLOWED))
-- -----------------------------------------------------------------------------
--- Changing echo status
+-- Changing echo status (Non-standard GHC extensions)
--- Non-standard GHC extension is to allow the echoing status
--- of a handles connected to terminals to be reconfigured:
+-- | Set the echoing status of a handle connected to a terminal (GHC only).
hSetEcho :: Handle -> Bool -> IO ()
hSetEcho handle on = do
ClosedHandle -> ioe_closedHandle
_ -> setEcho (haFD handle_) on
+-- | Get the echoing status of a handle connected to a terminal (GHC only).
+
hGetEcho :: Handle -> IO Bool
hGetEcho handle = do
isT <- hIsTerminalDevice handle
ClosedHandle -> ioe_closedHandle
_ -> getEcho (haFD handle_)
+-- | Is the handle connected to a terminal? (GHC only)
+
hIsTerminalDevice :: Handle -> IO Bool
hIsTerminalDevice handle = do
withHandle_ "hIsTerminalDevice" handle $ \ handle_ -> do
-- -----------------------------------------------------------------------------
-- hSetBinaryMode
--- | On Windows, reading a file in text mode (which is the default) will
--- translate CRLF to LF, and writing will translate LF to CRLF. This
--- is usually what you want with text files. With binary files this is
--- undesirable; also, as usual under Microsoft operating systems, text
--- mode treats control-Z as EOF. Setting binary mode using
--- 'hSetBinaryMode' turns off all special treatment of end-of-line and
--- end-of-file characters.
---
+-- | Select binary mode ('True') or text mode ('False') on a open handle.
+-- (GHC only; see also 'openBinaryFile'.)
+
hSetBinaryMode :: Handle -> Bool -> IO ()
hSetBinaryMode handle bin =
withAllHandles__ "hSetBinaryMode" handle $ \ handle_ ->
-- discarding any input data, before the handle is duplicated.
hDuplicate :: Handle -> IO Handle
-hDuplicate h@(FileHandle m) = do
+hDuplicate h@(FileHandle path m) = do
new_h_ <- withHandle' "hDuplicate" h m (dupHandle_ Nothing)
new_m <- newMVar new_h_
- return (FileHandle new_m)
-hDuplicate h@(DuplexHandle r w) = do
+ return (FileHandle path new_m)
+hDuplicate h@(DuplexHandle path r w) = do
new_w_ <- withHandle' "hDuplicate" h w (dupHandle_ Nothing)
new_w <- newMVar new_w_
new_r_ <- withHandle' "hDuplicate" h r (dupHandle_ (Just new_w))
new_r <- newMVar new_r_
- return (DuplexHandle new_r new_w)
+ return (DuplexHandle path new_r new_w)
dupHandle_ other_side h_ = do
-- flush the buffer first, so we don't have to copy its contents
-}
hDuplicateTo :: Handle -> Handle -> IO ()
-hDuplicateTo h1@(FileHandle m1) h2@(FileHandle m2) = do
+hDuplicateTo h1@(FileHandle _ m1) h2@(FileHandle _ m2) = do
withHandle__' "hDuplicateTo" h2 m2 $ \h2_ -> do
_ <- hClose_help h2_
withHandle' "hDuplicateTo" h1 m1 (dupHandle_ Nothing)
-hDuplicateTo h1@(DuplexHandle r1 w1) h2@(DuplexHandle r2 w2) = do
+hDuplicateTo h1@(DuplexHandle _ r1 w1) h2@(DuplexHandle _ r2 w2) = do
withHandle__' "hDuplicateTo" h2 w2 $ \w2_ -> do
_ <- hClose_help w2_
withHandle' "hDuplicateTo" h1 r1 (dupHandle_ Nothing)
"handles are incompatible" Nothing)
-- ---------------------------------------------------------------------------
+-- showing Handles.
+--
+-- | 'hShow' is in the 'IO' monad, and gives more comprehensive output
+-- than the (pure) instance of 'Show' for 'Handle'.
+
+hShow :: Handle -> IO String
+hShow h@(FileHandle path _) = showHandle' path False h
+hShow h@(DuplexHandle path _ _) = showHandle' path True h
+
+showHandle' filepath is_duplex h =
+ withHandle_ "showHandle" h $ \hdl_ ->
+ let
+ showType | is_duplex = showString "duplex (read-write)"
+ | otherwise = shows (haType hdl_)
+ in
+ return
+ (( showChar '{' .
+ showHdl (haType hdl_)
+ (showString "loc=" . showString filepath . showChar ',' .
+ showString "type=" . showType . showChar ',' .
+ showString "binary=" . shows (haIsBin hdl_) . showChar ',' .
+ showString "buffering=" . showBufMode (unsafePerformIO (readIORef (haBuffer hdl_))) (haBufferMode hdl_) . showString "}" )
+ ) "")
+ where
+
+ showHdl :: HandleType -> ShowS -> ShowS
+ showHdl ht cont =
+ case ht of
+ ClosedHandle -> shows ht . showString "}"
+ _ -> cont
+
+ showBufMode :: Buffer -> BufferMode -> ShowS
+ showBufMode buf bmo =
+ case bmo of
+ NoBuffering -> showString "none"
+ LineBuffering -> showString "line"
+ BlockBuffering (Just n) -> showString "block " . showParen True (shows n)
+ BlockBuffering Nothing -> showString "block " . showParen True (shows def)
+ where
+ def :: Int
+ def = bufSize buf
+
+-- ---------------------------------------------------------------------------
-- debugging
#ifdef DEBUG_DUMP
projects / haskell-directory.git / blobdiff