-%
-% (c) The AQUA Project, Glasgow University, 1994-1996
+% ------------------------------------------------------------------------------
+% $Id: PrelIOBase.lhs,v 1.30 2001/01/10 16:28:15 qrczak Exp $
+%
+% (c) The University of Glasgow, 1994-2000
%
\section[PrelIOBase]{Module @PrelIOBase@}
concretely; the @IO@ module itself exports abstractly.
\begin{code}
-{-# OPTIONS -fno-implicit-prelude #-}
-#include "error.h"
+{-# OPTIONS -fno-implicit-prelude -#include "cbits/stgio.h" #-}
+#include "config.h"
+#include "cbits/stgerror.h"
+#ifndef __HUGS__ /* Hugs just includes this in PreludeBuiltin so no header needed */
module PrelIOBase where
import {-# SOURCE #-} PrelErr ( error )
+
import PrelST
-import PrelTup
-import PrelMaybe
-import PrelAddr
-import PrelPack ( unpackCString )
import PrelBase
-import PrelArr ( ByteArray(..), MutableVar(..) )
-import PrelGHC
+import PrelNum ( fromInteger ) -- Integer literals
+import PrelMaybe ( Maybe(..) )
+import PrelAddr ( Addr(..), nullAddr )
+import PrelShow
+import PrelList
+import PrelDynamic
+import PrelPack ( unpackCString )
+
+#if !defined(__CONCURRENT_HASKELL__)
+import PrelArr ( MutableVar, readVar )
+#endif
+#endif
+#ifdef __HUGS__
+#define __CONCURRENT_HASKELL__
+#define stToIO id
+#define unpackCString primUnpackString
+#endif
+
+#ifndef __PARALLEL_HASKELL__
+#define FILE_OBJECT ForeignObj
+#else
+#define FILE_OBJECT Addr
+#endif
\end{code}
%*********************************************************
%* *
%*********************************************************
-IO is no longer built on top of PrimIO (which used to be a specialised
-version of the ST monad), instead it is now has its own type. This is
-purely for efficiency purposes, since we get to remove several levels
-of lifting in the type of the monad.
+The IO Monad is just an instance of the ST monad, where the state is
+the real world. We use the exception mechanism (in PrelException) to
+implement IO exceptions.
+
+NOTE: The IO representation is deeply wired in to various parts of the
+system. The following list may or may not be exhaustive:
+
+Compiler - types of various primitives in PrimOp.lhs
+
+RTS - forceIO (StgMiscClosures.hc)
+ - catchzh_fast, (un)?blockAsyncExceptionszh_fast, raisezh_fast
+ (Exceptions.hc)
+ - raiseAsync (Schedule.c)
+
+Prelude - PrelIOBase.lhs, and several other places including
+ PrelException.lhs.
+
+Libraries - parts of hslibs/lang.
+
+--SDM
\begin{code}
-newtype IO a = IO (State# RealWorld -> IOResult a)
+#ifndef __HUGS__
+newtype IO a = IO (State# RealWorld -> (# State# RealWorld, a #))
-{-# INLINE unIO #-}
+unIO :: IO a -> (State# RealWorld -> (# State# RealWorld, a #))
unIO (IO a) = a
-data IOResult a = IOok (State# RealWorld) a
- | IOfail (State# RealWorld) IOError
-
instance Functor IO where
- map f x = x >>= (return . f)
+ fmap f x = x >>= (return . f)
instance Monad IO where
{-# INLINE return #-}
{-# INLINE (>>) #-}
{-# INLINE (>>=) #-}
m >> k = m >>= \ _ -> k
- return x = IO $ \ s -> IOok s x
+ return x = returnIO x
- (IO m) >>= k =
- IO $ \s ->
- case m s of
- IOfail new_s err -> IOfail new_s err
- IOok new_s a -> unIO (k a) new_s
+ m >>= k = bindIO m k
+ fail s = ioError (userError s)
-fixIO :: (a -> IO a) -> IO a
- -- not required but worth having around
+liftIO :: IO a -> State# RealWorld -> STret RealWorld a
+liftIO (IO m) = \s -> case m s of (# s', r #) -> STret s' r
-fixIO k = IO $ \ s ->
- let
- (IO k_loop) = k loop
- result = k_loop s
- IOok _ loop = result
- in
- result
-
-fail :: IOError -> IO a
-fail err = IO $ \ s -> IOfail s err
-
-userError :: String -> IOError
-userError str = IOError Nothing UserError str
-
-catch :: IO a -> (IOError -> IO a) -> IO a
-catch (IO m) k = IO $ \ s ->
- case m s of
- IOok new_s a -> IOok new_s a
- IOfail new_s e -> unIO (k e) new_s
+bindIO :: IO a -> (a -> IO b) -> IO b
+bindIO (IO m) k = IO ( \ s ->
+ case m s of
+ (# new_s, a #) -> unIO (k a) new_s
+ )
-instance Show (IO a) where
- showsPrec p f = showString "<<IO action>>"
- showList = showList__ (showsPrec 0)
+returnIO :: a -> IO a
+returnIO x = IO (\ s -> (# s, x #))
+#endif
\end{code}
%*********************************************************
%*********************************************************
\begin{code}
-stToIO :: ST RealWorld a -> IO a
-stToIO (ST m) = IO $ \ s -> case (m s) of STret new_s r -> IOok new_s r
-
-ioToST :: IO a -> ST RealWorld a
-ioToST (IO io) = ST $ \ s ->
- case (io s) of
- IOok new_s a -> STret new_s a
- IOfail new_s e -> error ("I/O Error (ioToST): " ++ showsPrec 0 e "\n")
+#ifdef __HUGS__
+/* Hugs doesn't distinguish these types so no coercion required) */
+#else
+stToIO :: ST RealWorld a -> IO a
+stToIO (ST m) = (IO m)
+
+ioToST :: IO a -> ST RealWorld a
+ioToST (IO m) = (ST m)
+#endif
\end{code}
%*********************************************************
%* *
-\subsection{Utility functions}
+\subsection{Unsafe @IO@ operations}
%* *
%*********************************************************
-I'm not sure why this little function is here...
-
\begin{code}
-fputs :: Addr{-FILE*-} -> String -> IO Bool
-
-fputs stream [] = return True
+#ifndef __HUGS__
+{-# NOINLINE unsafePerformIO #-}
+unsafePerformIO :: IO a -> a
+unsafePerformIO (IO m) = case m realWorld# of (# _, r #) -> r
-fputs stream (c : cs)
- = _ccall_ stg_putc c stream >> -- stg_putc expands to putc
- fputs stream cs -- (just does some casting stream)
+unsafeInterleaveIO :: IO a -> IO a
+unsafeInterleaveIO = stToIO . unsafeInterleaveST . ioToST
+#endif
\end{code}
-
%*********************************************************
%* *
-\subsection{Type @IOError@}
+\subsection{Types @Handle@, @Handle__@}
%* *
%*********************************************************
-A value @IOError@ encode errors occurred in the @IO@ monad.
-An @IOError@ records a more specific error type, a descriptive
-string and maybe the handle that was used when the error was
-flagged.
-
-\begin{code}
-data IOError
- = IOError
- (Maybe Handle) -- the handle used by the action flagging the
- -- the error.
- IOErrorType -- what it was.
- String -- error type specific information.
-
-
-data IOErrorType
- = AlreadyExists | HardwareFault
- | IllegalOperation | InappropriateType
- | Interrupted | InvalidArgument
- | NoSuchThing | OtherError
- | PermissionDenied | ProtocolError
- | ResourceBusy | ResourceExhausted
- | ResourceVanished | SystemError
- | TimeExpired | UnsatisfiedConstraints
- | UnsupportedOperation | UserError
- | EOF
- deriving (Eq, Show)
-
-\end{code}
-
-Predicates on IOError; little effort made on these so far...
+The type for @Handle@ is defined rather than in @IOHandle@
+module, as the @IOError@ type uses it..all operations over
+a handles reside in @IOHandle@.
\begin{code}
-isAlreadyExistsError (IOError _ AlreadyExists _) = True
-isAlreadyExistsError _ = False
+#ifndef __HUGS__
+{-
+ Sigh, the MVar ops in ConcBase depend on IO, the IO
+ representation here depend on MVars for handles (when
+ compiling in a concurrent way). Break the cycle by having
+ the definition of MVars go here:
-isAlreadyInUseError (IOError _ ResourceBusy _) = True
-isAlreadyInUseError _ = False
+-}
+data MVar a = MVar (MVar# RealWorld a)
-isFullError (IOError _ ResourceExhausted _) = True
-isFullError _ = False
+-- pull in Eq (Mvar a) too, to avoid PrelConc being an orphan-instance module
+instance Eq (MVar a) where
+ (MVar mvar1#) == (MVar mvar2#) = sameMVar# mvar1# mvar2#
-isEOFError (IOError _ EOF _) = True
-isEOFError _ = True
+{-
+ Double sigh - ForeignObj is needed here too to break a cycle.
+-}
+data ForeignObj = ForeignObj ForeignObj# -- another one
+instance CCallable ForeignObj
-isIllegalOperation (IOError _ IllegalOperation _) = True
-isIllegalOperation _ = False
+eqForeignObj :: ForeignObj -> ForeignObj -> Bool
+eqForeignObj mp1 mp2
+ = unsafePerformIO (primEqForeignObj mp1 mp2) /= (0::Int)
-isPermissionError (IOError _ PermissionDenied _) = True
-isPermissionError _ = False
+foreign import "eqForeignObj" unsafe primEqForeignObj :: ForeignObj -> ForeignObj -> IO Int
-isDoesNotExistError (IOError _ NoSuchThing _) = True
-isDoesNotExistError _ = False
+instance Eq ForeignObj where
+ p == q = eqForeignObj p q
+ p /= q = not (eqForeignObj p q)
+#endif /* ndef __HUGS__ */
-isUserError (IOError _ UserError _) = True
-isUserError _ = False
-\end{code}
+#if defined(__CONCURRENT_HASKELL__)
+newtype Handle = Handle (MVar Handle__)
+#else
+newtype Handle = Handle (MutableVar RealWorld Handle__)
+#endif
-Showing @IOError@s
+instance Eq Handle where
+ (Handle h1) == (Handle h2) = h1 == h2
-\begin{code}
-instance Show IOError where
- showsPrec p (IOError _ UserError s) rs =
- showString s rs
{-
- showsPrec p (IOError _ EOF _) rs =
- showsPrec p EOF rs
+ A Handle is represented by (a reference to) a record
+ containing the state of the I/O port/device. We record
+ the following pieces of info:
+
+ * type (read,write,closed etc.)
+ * pointer to the external file object.
+ * buffering mode
+ * user-friendly name (usually the
+ FilePath used when IO.openFile was called)
+
+Note: when a Handle is garbage collected, we want to flush its buffer
+and close the OS file handle, so as to free up a (precious) resource.
-}
- showsPrec p (IOError _ iot s) rs =
- showsPrec p
- iot
- (case s of {
- "" -> rs;
- _ -> showString ": " $
- showString s rs})
-
-\end{code}
-
-The @String@ part of an @IOError@ is platform-dependent. However, to
-provide a uniform mechanism for distinguishing among errors within
-these broad categories, each platform-specific standard shall specify
-the exact strings to be used for particular errors. For errors not
-explicitly mentioned in the standard, any descriptive string may be
-used.
-
-\begin{change}
-SOF & 4/96 & added argument to indicate function that flagged error
-\end{change}
-% Hmm..does these envs work?!...SOF
-
-\begin{code}
-constructErrorAndFail :: String -> IO a
-constructErrorAndFail call_site
- = constructError call_site >>= \ io_error ->
- fail io_error
-
-\end{code}
+data Handle__
+ = Handle__ {
+ haFO__ :: FILE_OBJECT,
+ haType__ :: Handle__Type,
+ haBufferMode__ :: BufferMode,
+ haFilePath__ :: FilePath,
+ haBuffers__ :: [Addr]
+ }
-This doesn't seem to be documented/spelled out anywhere,
-so here goes: (SOF)
+{-
+ Internally, we classify handles as being one
+ of the following:
+-}
+data Handle__Type
+ = ClosedHandle
+ | SemiClosedHandle
+ | ReadHandle
+ | WriteHandle
+ | AppendHandle
+ | ReadWriteHandle
-The implementation of the IO prelude uses various C stubs
-to do the actual interaction with the OS. The bandwidth
-\tr{C<->Haskell} is somewhat limited, so the general strategy
-for flaggging any errors (apart from possibly using the
-return code of the external call), is to set the @ghc_errtype@
-to a value that is one of the \tr{#define}s in @includes/error.h@.
-@ghc_errstr@ holds a character string providing error-specific
-information.
-\begin{code}
-constructError :: String -> IO IOError
-constructError call_site =
- _casm_ ``%r = ghc_errtype;'' >>= \ (I# errtype#) ->
- _casm_ ``%r = ghc_errstr;'' >>= \ str ->
- let
- iot =
- case errtype# of
- ERR_ALREADYEXISTS# -> AlreadyExists
- ERR_HARDWAREFAULT# -> HardwareFault
- ERR_ILLEGALOPERATION# -> IllegalOperation
- ERR_INAPPROPRIATETYPE# -> InappropriateType
- ERR_INTERRUPTED# -> Interrupted
- ERR_INVALIDARGUMENT# -> InvalidArgument
- ERR_NOSUCHTHING# -> NoSuchThing
- ERR_OTHERERROR# -> OtherError
- ERR_PERMISSIONDENIED# -> PermissionDenied
- ERR_PROTOCOLERROR# -> ProtocolError
- ERR_RESOURCEBUSY# -> ResourceBusy
- ERR_RESOURCEEXHAUSTED# -> ResourceExhausted
- ERR_RESOURCEVANISHED# -> ResourceVanished
- ERR_SYSTEMERROR# -> SystemError
- ERR_TIMEEXPIRED# -> TimeExpired
- ERR_UNSATISFIEDCONSTRAINTS# -> UnsatisfiedConstraints
- ERR_UNSUPPORTEDOPERATION# -> UnsupportedOperation
- ERR_EOF# -> EOF
- _ -> OtherError
+-- File names are specified using @FilePath@, a OS-dependent
+-- string that (hopefully, I guess) maps to an accessible file/object.
- msg =
- call_site ++ ':' : ' ' : unpackCString str ++
- case iot of
- OtherError -> "(error code: " ++ show (I# errtype#) ++ ")"
- _ -> ""
- in
- return (IOError Nothing iot msg)
+type FilePath = String
\end{code}
%*********************************************************
%* *
-\subsection{Types @Handle@, @Handle__@}
+\subsection[Show-Handle]{Show instance for Handles}
%* *
%*********************************************************
-The type for @Handle@ is defined rather than in @IOHandle@
-module, as the @IOError@ type uses it..all operations over
-a handles reside in @IOHandle@.
-
\begin{code}
-
-{-
- Sigh, the MVar ops in ConcBase depend on IO, the IO
- representation here depend on MVars for handles (when
- compiling a concurrent way). Break the cycle by having
- the definition of MVars go here:
-
--}
-data MVar a = MVar (SynchVar# RealWorld a)
-
-{-
- Double sigh - ForeignObj is needed here too to break a cycle.
--}
-data ForeignObj = ForeignObj ForeignObj# -- another one
-
+-- handle types are 'show'ed when printing error msgs, so
+-- we provide a more user-friendly Show instance for it
+-- than the derived one.
+instance Show Handle__Type where
+ showsPrec p t =
+ case t of
+ ClosedHandle -> showString "closed"
+ SemiClosedHandle -> showString "semi-closed"
+ ReadHandle -> showString "readable"
+ WriteHandle -> showString "writeable"
+ AppendHandle -> showString "writeable (append)"
+ ReadWriteHandle -> showString "read-writeable"
+
+instance Show Handle where
+ showsPrec p (Handle h) =
+ let
#if defined(__CONCURRENT_HASKELL__)
-newtype Handle = Handle (MVar Handle__)
+#ifdef __HUGS__
+ hdl_ = unsafePerformIO (primTakeMVar h)
#else
-newtype Handle = Handle (MutableVar RealWorld Handle__)
+ -- (Big) SIGH: unfolded defn of takeMVar to avoid
+ -- an (oh-so) unfortunate module loop with PrelConc.
+ hdl_ = unsafePerformIO (IO $ \ s# ->
+ case h of { MVar h# ->
+ case takeMVar# h# s# of { (# s2# , r #) ->
+ (# s2#, r #) }})
#endif
-
-data Handle__
- = ErrorHandle IOError
- | ClosedHandle
-#ifndef __PARALLEL_HASKELL__
- | SemiClosedHandle ForeignObj (Addr, Int)
- | ReadHandle ForeignObj (Maybe BufferMode) Bool
- | WriteHandle ForeignObj (Maybe BufferMode) Bool
- | AppendHandle ForeignObj (Maybe BufferMode) Bool
- | ReadWriteHandle ForeignObj (Maybe BufferMode) Bool
#else
- | SemiClosedHandle Addr (Addr, Int)
- | ReadHandle Addr (Maybe BufferMode) Bool
- | WriteHandle Addr (Maybe BufferMode) Bool
- | AppendHandle Addr (Maybe BufferMode) Bool
- | ReadWriteHandle Addr (Maybe BufferMode) Bool
+ hdl_ = unsafePerformIO (stToIO (readVar h))
#endif
-
--- Standard Instances as defined by the Report..
--- instance Eq Handle (defined in IO)
--- instance Show Handle ""
-
+ in
+ showChar '{' .
+ showHdl (haType__ hdl_)
+ (showString "loc=" . showString (haFilePath__ hdl_) . showChar ',' .
+ showString "type=" . showsPrec p (haType__ hdl_) . showChar ',' .
+ showString "buffering=" . showBufMode (haFO__ hdl_) (haBufferMode__ hdl_) . showString "}\n" )
+ where
+ showHdl :: Handle__Type -> ShowS -> ShowS
+ showHdl ht cont =
+ case ht of
+ ClosedHandle -> showsPrec p ht . showString "}\n"
+ _ -> cont
+
+ showBufMode :: FILE_OBJECT -> BufferMode -> ShowS
+ showBufMode fo bmo =
+ case bmo of
+ NoBuffering -> showString "none"
+ LineBuffering -> showString "line"
+ BlockBuffering (Just n) -> showString "block " . showParen True (showsPrec p n)
+ BlockBuffering Nothing -> showString "block " . showParen True (showsPrec p def)
+ where
+ def :: Int
+ def = unsafePerformIO (getBufSize fo)
\end{code}
%*********************************************************
the next block of data is read into this buffer.
\item[no-buffering] the next input item is read and returned.
\end{itemize}
+
For most implementations, physical files will normally be block-buffered
-and terminals will normally be line-buffered.
+and terminals will normally be line-buffered. (the IO interface provides
+operations for changing the default buffering of a handle tho.)
\begin{code}
data BufferMode
\end{code}
+Foreign import declarations to helper routines:
+
+\begin{code}
+foreign import "libHS_cbits" "getErrStr__" unsafe getErrStr__ :: IO Addr
+foreign import "libHS_cbits" "getErrNo__" unsafe getErrNo__ :: IO Int
+foreign import "libHS_cbits" "getErrType__" unsafe getErrType__ :: IO Int
+
+malloc :: Int -> IO Addr
+malloc sz = do
+ a <- _malloc sz
+ if (a == nullAddr)
+ then ioException (IOError Nothing ResourceExhausted "malloc" "")
+ else return a
+
+foreign import "malloc" unsafe _malloc :: Int -> IO Addr
+
+foreign import "libHS_cbits" "getBufSize" unsafe
+ getBufSize :: FILE_OBJECT -> IO Int
+foreign import "libHS_cbits" "setBuf" unsafe
+ setBuf :: FILE_OBJECT -> Addr -> Int -> IO ()
+
+\end{code}
+
+%*********************************************************
+%* *
+\subsection{Exception datatype and operations}
+%* *
+%*********************************************************
+
+\begin{code}
+data Exception
+ = IOException IOException -- IO exceptions
+ | ArithException ArithException -- Arithmetic exceptions
+ | ArrayException ArrayException -- Array-related exceptions
+ | ErrorCall String -- Calls to 'error'
+ | NoMethodError String -- A non-existent method was invoked
+ | PatternMatchFail String -- A pattern match / guard failure
+ | RecSelError String -- Selecting a non-existent field
+ | RecConError String -- Field missing in record construction
+ | RecUpdError String -- Record doesn't contain updated field
+ | AssertionFailed String -- Assertions
+ | DynException Dynamic -- Dynamic exceptions
+ | AsyncException AsyncException -- Externally generated errors
+ | PutFullMVar -- Put on a full MVar
+ | BlockedOnDeadMVar -- Blocking on a dead MVar
+ | NonTermination
+ | UserError String
+
+data ArithException
+ = Overflow
+ | Underflow
+ | LossOfPrecision
+ | DivideByZero
+ | Denormal
+ deriving (Eq, Ord)
+
+data AsyncException
+ = StackOverflow
+ | HeapOverflow
+ | ThreadKilled
+ deriving (Eq, Ord)
+
+data ArrayException
+ = IndexOutOfBounds String -- out-of-range array access
+ | UndefinedElement String -- evaluating an undefined element
+ deriving (Eq, Ord)
+
+stackOverflow, heapOverflow :: Exception -- for the RTS
+stackOverflow = AsyncException StackOverflow
+heapOverflow = AsyncException HeapOverflow
+
+instance Show ArithException where
+ showsPrec _ Overflow = showString "arithmetic overflow"
+ showsPrec _ Underflow = showString "arithmetic underflow"
+ showsPrec _ LossOfPrecision = showString "loss of precision"
+ showsPrec _ DivideByZero = showString "divide by zero"
+ showsPrec _ Denormal = showString "denormal"
+
+instance Show AsyncException where
+ showsPrec _ StackOverflow = showString "stack overflow"
+ showsPrec _ HeapOverflow = showString "heap overflow"
+ showsPrec _ ThreadKilled = showString "thread killed"
+
+instance Show ArrayException where
+ showsPrec _ (IndexOutOfBounds s)
+ = showString "array index out of range"
+ . (if not (null s) then showString ": " . showString s
+ else id)
+ showsPrec _ (UndefinedElement s)
+ = showString "undefined array element"
+ . (if not (null s) then showString ": " . showString s
+ else id)
+
+instance Show Exception where
+ showsPrec _ (IOException err) = shows err
+ showsPrec _ (ArithException err) = shows err
+ showsPrec _ (ArrayException err) = shows err
+ showsPrec _ (ErrorCall err) = showString err
+ showsPrec _ (NoMethodError err) = showString err
+ showsPrec _ (PatternMatchFail err) = showString err
+ showsPrec _ (RecSelError err) = showString err
+ showsPrec _ (RecConError err) = showString err
+ showsPrec _ (RecUpdError err) = showString err
+ showsPrec _ (AssertionFailed err) = showString err
+ showsPrec _ (DynException _err) = showString "unknown exception"
+ showsPrec _ (AsyncException e) = shows e
+ showsPrec _ (PutFullMVar) = showString "putMVar: full MVar"
+ showsPrec _ (BlockedOnDeadMVar) = showString "thread blocked indefinitely"
+ showsPrec _ (NonTermination) = showString "<<loop>>"
+ showsPrec _ (UserError err) = showString err
+\end{code}
+
+%*********************************************************
+%* *
+\subsection{Primitive throw}
+%* *
+%*********************************************************
+
+\begin{code}
+throw :: Exception -> a
+throw exception = raise# exception
+
+ioError :: Exception -> IO a
+ioError err = IO $ \s -> throw err s
+
+ioException :: IOException -> IO a
+ioException err = IO $ \s -> throw (IOException err) s
+\end{code}
+
+%*********************************************************
+%* *
+\subsection{Type @IOError@}
+%* *
+%*********************************************************
+
+A value @IOError@ encode errors occurred in the @IO@ monad.
+An @IOError@ records a more specific error type, a descriptive
+string and maybe the handle that was used when the error was
+flagged.
+
\begin{code}
-performGC :: IO ()
-performGC = _ccall_GC_ StgPerformGarbageCollection
+type IOError = Exception
+
+data IOException
+ = IOError
+ (Maybe Handle) -- the handle used by the action flagging the
+ -- the error.
+ IOErrorType -- what it was.
+ String -- location
+ String -- error type specific information.
+
+instance Eq IOException where
+ (IOError h1 e1 loc1 str1) == (IOError h2 e2 loc2 str2) =
+ e1==e2 && str1==str2 && h1==h2 && loc1 == loc2
+
+data IOErrorType
+ = AlreadyExists | HardwareFault
+ | IllegalOperation | InappropriateType
+ | Interrupted | InvalidArgument
+ | NoSuchThing | OtherError
+ | PermissionDenied | ProtocolError
+ | ResourceBusy | ResourceExhausted
+ | ResourceVanished | SystemError
+ | TimeExpired | UnsatisfiedConstraints
+ | UnsupportedOperation
+ | EOF
+#if defined(cygwin32_TARGET_OS) || defined(mingw32_TARGET_OS)
+ | ComError Int -- HRESULT
+#endif
+ deriving (Eq)
+
+instance Show IOErrorType where
+ showsPrec _ e =
+ showString $
+ case e of
+ AlreadyExists -> "already exists"
+ HardwareFault -> "hardware fault"
+ IllegalOperation -> "illegal operation"
+ InappropriateType -> "inappropriate type"
+ Interrupted -> "interrupted"
+ InvalidArgument -> "invalid argument"
+ NoSuchThing -> "does not exist"
+ OtherError -> "failed"
+ PermissionDenied -> "permission denied"
+ ProtocolError -> "protocol error"
+ ResourceBusy -> "resource busy"
+ ResourceExhausted -> "resource exhausted"
+ ResourceVanished -> "resource vanished"
+ SystemError -> "system error"
+ TimeExpired -> "timeout"
+ UnsatisfiedConstraints -> "unsatisified constraints" -- ultra-precise!
+ UnsupportedOperation -> "unsupported operation"
+ EOF -> "end of file"
+#if defined(cygwin32_TARGET_OS) || defined(mingw32_TARGET_OS)
+ ComError _ -> "COM error"
+#endif
+
+
+
+userError :: String -> IOError
+userError str = UserError str
+\end{code}
+
+Predicates on IOError; little effort made on these so far...
+
+\begin{code}
+
+isAlreadyExistsError :: IOError -> Bool
+isAlreadyExistsError (IOException (IOError _ AlreadyExists _ _)) = True
+isAlreadyExistsError _ = False
+
+isAlreadyInUseError :: IOError -> Bool
+isAlreadyInUseError (IOException (IOError _ ResourceBusy _ _)) = True
+isAlreadyInUseError _ = False
+
+isFullError :: IOError -> Bool
+isFullError (IOException (IOError _ ResourceExhausted _ _)) = True
+isFullError _ = False
+
+isEOFError :: IOError -> Bool
+isEOFError (IOException (IOError _ EOF _ _)) = True
+isEOFError _ = False
+
+isIllegalOperation :: IOError -> Bool
+isIllegalOperation (IOException (IOError _ IllegalOperation _ _)) = True
+isIllegalOperation _ = False
+
+isPermissionError :: IOError -> Bool
+isPermissionError (IOException (IOError _ PermissionDenied _ _)) = True
+isPermissionError _ = False
+
+isDoesNotExistError :: IOError -> Bool
+isDoesNotExistError (IOException (IOError _ NoSuchThing _ _)) = True
+isDoesNotExistError _ = False
+
+isUserError :: IOError -> Bool
+isUserError (UserError _) = True
+isUserError _ = False
+\end{code}
+
+Showing @IOError@s
+
+\begin{code}
+#ifdef __HUGS__
+-- For now we give a fairly uninformative error message which just happens to
+-- be like the ones that Hugs used to give.
+instance Show IOException where
+ showsPrec p (IOError hdl iot loc s) = showString s . showChar '\n'
+#else
+instance Show IOException where
+ showsPrec p (IOError hdl iot loc s) =
+ showsPrec p iot .
+ showChar '\n' .
+ (case loc of
+ "" -> id
+ _ -> showString "Action: " . showString loc . showChar '\n') .
+ showHdl .
+ (case s of
+ "" -> id
+ _ -> showString "Reason: " . showString s)
+ where
+ showHdl =
+ case hdl of
+ Nothing -> id
+ Just h -> showString "Handle: " . showsPrec p h
+
+#endif
+\end{code}
+
+The @String@ part of an @IOError@ is platform-dependent. However, to
+provide a uniform mechanism for distinguishing among errors within
+these broad categories, each platform-specific standard shall specify
+the exact strings to be used for particular errors. For errors not
+explicitly mentioned in the standard, any descriptive string may be
+used.
+
+\begin{code}
+constructErrorAndFail :: String -> IO a
+constructErrorAndFail call_site
+ = constructError call_site >>= \ io_error ->
+ ioError (IOException io_error)
+
+constructErrorAndFailWithInfo :: String -> String -> IO a
+constructErrorAndFailWithInfo call_site reason
+ = constructErrorMsg call_site (Just reason) >>= \ io_error ->
+ ioError (IOException io_error)
+
+\end{code}
+
+This doesn't seem to be documented/spelled out anywhere,
+so here goes: (SOF)
+
+The implementation of the IO prelude uses various C stubs
+to do the actual interaction with the OS. The bandwidth
+\tr{C<->Haskell} is somewhat limited, so the general strategy
+for flaggging any errors (apart from possibly using the
+return code of the external call), is to set the @ghc_errtype@
+to a value that is one of the \tr{#define}s in @includes/error.h@.
+@ghc_errstr@ holds a character string providing error-specific
+information. Error constructing functions will then reach out
+and grab these values when generating
+
+\begin{code}
+constructError :: String -> IO IOException
+constructError call_site = constructErrorMsg call_site Nothing
+
+constructErrorMsg :: String -> Maybe String -> IO IOException
+constructErrorMsg call_site reason =
+ getErrType__ >>= \ errtype ->
+ getErrStr__ >>= \ str ->
+ let
+ iot =
+ case (errtype::Int) of
+ ERR_ALREADYEXISTS -> AlreadyExists
+ ERR_HARDWAREFAULT -> HardwareFault
+ ERR_ILLEGALOPERATION -> IllegalOperation
+ ERR_INAPPROPRIATETYPE -> InappropriateType
+ ERR_INTERRUPTED -> Interrupted
+ ERR_INVALIDARGUMENT -> InvalidArgument
+ ERR_NOSUCHTHING -> NoSuchThing
+ ERR_OTHERERROR -> OtherError
+ ERR_PERMISSIONDENIED -> PermissionDenied
+ ERR_PROTOCOLERROR -> ProtocolError
+ ERR_RESOURCEBUSY -> ResourceBusy
+ ERR_RESOURCEEXHAUSTED -> ResourceExhausted
+ ERR_RESOURCEVANISHED -> ResourceVanished
+ ERR_SYSTEMERROR -> SystemError
+ ERR_TIMEEXPIRED -> TimeExpired
+ ERR_UNSATISFIEDCONSTRAINTS -> UnsatisfiedConstraints
+ ERR_UNSUPPORTEDOPERATION -> UnsupportedOperation
+ ERR_EOF -> EOF
+ _ -> OtherError
+
+ msg =
+ unpackCString str ++
+ (case iot of
+ OtherError -> "(error code: " ++ show errtype ++ ")"
+ _ -> "") ++
+ (case reason of
+ Nothing -> ""
+ Just m -> ": "++m)
+ in
+ return (IOError Nothing iot call_site msg)
\end{code}
projects / ghc-hetmet.git / blobdiff