% ------------------------------------------------------------------------------
-% $Id: PrelIOBase.lhs,v 1.27 2000/07/08 18:17:40 panne Exp $
+% $Id: PrelIOBase.lhs,v 1.38 2001/05/18 16:54:05 simonmar Exp $
%
-% (c) The University of Glasgow, 1994-2000
+% (c) The University of Glasgow, 1994-2001
%
-\section[PrelIOBase]{Module @PrelIOBase@}
-
-Definitions for the @IO@ monad and its friends. Everything is exported
-concretely; the @IO@ module itself exports abstractly.
+% Definitions for the @IO@ monad and its friends. Everything is exported
+% concretely; the @IO@ module itself exports abstractly.
\begin{code}
-{-# OPTIONS -fno-implicit-prelude -#include "cbits/stgio.h" #-}
+{-# OPTIONS -fno-implicit-prelude #-}
#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 PrelArr
import PrelBase
+import PrelNum -- To get fromInteger etc, needed because of -fno-implicit-prelude
import PrelMaybe ( Maybe(..) )
-import PrelAddr ( Addr(..) )
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}
-
-%*********************************************************
-%* *
-\subsection{The @IO@ monad}
-%* *
-%*********************************************************
+-- ---------------------------------------------------------------------------
+-- The IO 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.
Libraries - parts of hslibs/lang.
--SDM
+-}
-\begin{code}
-#ifndef __HUGS__
newtype IO a = IO (State# RealWorld -> (# State# RealWorld, a #))
unIO :: IO a -> (State# RealWorld -> (# State# RealWorld, a #))
return x = returnIO x
m >>= k = bindIO m k
- fail s = error s -- not ioError?
+ fail s = failIO s
+
+failIO :: String -> IO a
+failIO s = ioError (userError s)
liftIO :: IO a -> State# RealWorld -> STret RealWorld a
liftIO (IO m) = \s -> case m s of (# s', r #) -> STret s' r
returnIO :: a -> IO a
returnIO x = IO (\ s -> (# s, x #))
-#endif
-\end{code}
-%*********************************************************
-%* *
-\subsection{Coercions to @ST@}
-%* *
-%*********************************************************
+-- ---------------------------------------------------------------------------
+-- Coercions between IO and ST
-\begin{code}
-#ifdef __HUGS__
-/* Hugs doesn't distinguish these types so no coercion required) */
-#else
+--stToIO :: (forall s. ST s a) -> IO a
stToIO :: ST RealWorld a -> IO a
-stToIO (ST m) = (IO m)
+stToIO (ST m) = IO m
ioToST :: IO a -> ST RealWorld a
ioToST (IO m) = (ST m)
-#endif
-\end{code}
-%*********************************************************
-%* *
-\subsection{Unsafe @IO@ operations}
-%* *
-%*********************************************************
+-- ---------------------------------------------------------------------------
+-- Unsafe IO operations
-\begin{code}
-#ifndef __HUGS__
{-# NOINLINE unsafePerformIO #-}
unsafePerformIO :: IO a -> a
unsafePerformIO (IO m) = case m realWorld# of (# _, r #) -> r
+{-# NOINLINE unsafeInterleaveIO #-}
unsafeInterleaveIO :: IO a -> IO a
-unsafeInterleaveIO = stToIO . unsafeInterleaveST . ioToST
-#endif
-\end{code}
+unsafeInterleaveIO (IO m)
+ = IO ( \ s -> let
+ r = case m s of (# _, res #) -> res
+ in
+ (# s, r #))
-%*********************************************************
-%* *
-\subsection{Types @Handle@, @Handle__@}
-%* *
-%*********************************************************
-
-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}
+-- ---------------------------------------------------------------------------
+-- Handle type
-#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:
-
--}
data MVar a = MVar (MVar# RealWorld a)
-- 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#
-{-
- Double sigh - ForeignObj is needed here too to break a cycle.
--}
-data ForeignObj = ForeignObj ForeignObj# -- another one
-instance CCallable ForeignObj
+-- 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:
-eqForeignObj :: ForeignObj -> ForeignObj -> Bool
-eqForeignObj mp1 mp2
- = unsafePerformIO (primEqForeignObj mp1 mp2) /= (0::Int)
+-- * type (read,write,closed etc.)
+-- * the underlying file descriptor
+-- * buffering mode
+-- * buffer, and spare buffers
+-- * user-friendly name (usually the
+-- FilePath used when IO.openFile was called)
-foreign import "eqForeignObj" unsafe primEqForeignObj :: ForeignObj -> ForeignObj -> IO Int
+-- 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.
-instance Eq ForeignObj where
- p == q = eqForeignObj p q
- p /= q = not (eqForeignObj p q)
-#endif /* ndef __HUGS__ */
+data Handle
+ = FileHandle -- A normal handle to a file
+ !(MVar Handle__)
-#if defined(__CONCURRENT_HASKELL__)
-newtype Handle = Handle (MVar Handle__)
-#else
-newtype Handle = Handle (MutableVar RealWorld Handle__)
-#endif
+ | DuplexHandle -- A handle to a read/write stream
+ !(MVar Handle__) -- The read side
+ !(MVar Handle__) -- The write side
+
+-- NOTES:
+-- * A 'FileHandle' is seekable. A 'DuplexHandle' may or may not be
+-- seekable.
instance Eq Handle where
- (Handle h1) == (Handle h2) = h1 == h2
+ (FileHandle h1) == (FileHandle h2) = h1 == h2
+ (DuplexHandle h1 _) == (DuplexHandle h2 _) = h1 == h2
+ _ == _ = False
+
+type FD = Int -- XXX ToDo: should be CInt
-{-
- 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.
--}
data Handle__
= Handle__ {
- haFO__ :: FILE_OBJECT,
- haType__ :: Handle__Type,
- haBufferMode__ :: BufferMode,
- haFilePath__ :: FilePath,
- haBuffers__ :: [Addr]
+ haFD :: !FD,
+ haType :: HandleType,
+ haBufferMode :: BufferMode,
+ haFilePath :: FilePath,
+ haBuffer :: !(IORef Buffer),
+ haBuffers :: !(IORef BufferList)
}
-{-
- Internally, we classify handles as being one
- of the following:
--}
-data Handle__Type
- = ErrorHandle IOException
- | ClosedHandle
+-- ---------------------------------------------------------------------------
+-- Buffers
+
+-- The buffer is represented by a mutable variable containing a
+-- record, where the record contains the raw buffer and the start/end
+-- points of the filled portion. We use a mutable variable so that
+-- the common operation of writing (or reading) some data from (to)
+-- the buffer doesn't need to modify, and hence copy, the handle
+-- itself, it just updates the buffer.
+
+-- There will be some allocation involved in a simple hPutChar in
+-- order to create the new Buffer structure (below), but this is
+-- relatively small, and this only has to be done once per write
+-- operation.
+
+-- The buffer contains its size - we could also get the size by
+-- calling sizeOfMutableByteArray# on the raw buffer, but that tends
+-- to be rounded up to the nearest Word.
+
+type RawBuffer = MutableByteArray# RealWorld
+
+-- INVARIANTS on a Buffer:
+--
+-- * A handle *always* has a buffer, even if it is only 1 character long
+-- (an unbuffered handle needs a 1 character buffer in order to support
+-- hLookAhead and hIsEOF).
+-- * r <= w
+-- * if r == w, then r == 0 && w == 0
+-- * if state == WriteBuffer, then r == 0
+-- * a write buffer is never full. If an operation
+-- fills up the buffer, it will always flush it before
+-- returning.
+-- * a read buffer may be full as a result of hLookAhead. In normal
+-- operation, a read buffer always has at least one character of space.
+
+data Buffer
+ = Buffer {
+ bufBuf :: RawBuffer,
+ bufRPtr :: !Int,
+ bufWPtr :: !Int,
+ bufSize :: !Int,
+ bufState :: BufferState
+ }
+
+data BufferState = ReadBuffer | WriteBuffer deriving (Eq)
+
+-- we keep a few spare buffers around in a handle to avoid allocating
+-- a new one for each hPutStr. These buffers are *guaranteed* to be the
+-- same size as the main buffer.
+data BufferList
+ = BufferListNil
+ | BufferListCons RawBuffer BufferList
+
+
+bufferIsWritable :: Buffer -> Bool
+bufferIsWritable Buffer{ bufState=WriteBuffer } = True
+bufferIsWritable _other = False
+
+bufferEmpty :: Buffer -> Bool
+bufferEmpty Buffer{ bufRPtr=r, bufWPtr=w } | r == w = True
+bufferEmpty _other = False
+
+-- only makes sense for a write buffer
+bufferFull :: Buffer -> Bool
+bufferFull b@Buffer{ bufWPtr=w } = w >= bufSize b
+
+-- Internally, we classify handles as being one
+-- of the following:
+
+data HandleType
+ = ClosedHandle
| SemiClosedHandle
| ReadHandle
| WriteHandle
| AppendHandle
| ReadWriteHandle
-
+ | ReadSideHandle !(MVar Handle__) -- read side of a duplex handle
-- File names are specified using @FilePath@, a OS-dependent
-- string that (hopefully, I guess) maps to an accessible file/object.
type FilePath = String
-\end{code}
-%*********************************************************
-%* *
-\subsection[Show-Handle]{Show instance for Handles}
-%* *
-%*********************************************************
+-- ---------------------------------------------------------------------------
+-- Buffering modes
+
+-- Three kinds of buffering are supported: line-buffering,
+-- block-buffering or no-buffering. These modes have the following
+-- effects. For output, items are written out from the internal
+-- buffer according to the buffer mode:
+--
+-- * line-buffering the entire output buffer is written
+-- out whenever a newline is output, the output buffer overflows,
+-- a flush is issued, or the handle is closed.
+--
+-- * block-buffering the entire output buffer is written out whenever
+-- it overflows, a flush is issued, or the handle
+-- is closed.
+--
+-- * no-buffering output is written immediately, and never stored
+-- in the output buffer.
+--
+-- The output buffer is emptied as soon as it has been written out.
+
+-- Similarly, input occurs according to the buffer mode for handle {\em hdl}.
+
+-- * line-buffering when the input buffer for the handle is not empty,
+-- the next item is obtained from the buffer;
+-- otherwise, when the input buffer is empty,
+-- characters up to and including the next newline
+-- character are read into the buffer. No characters
+-- are available until the newline character is
+-- available.
+--
+-- * block-buffering when the input buffer for the handle becomes empty,
+-- the next block of data is read into this buffer.
+--
+-- * no-buffering the next input item is read and returned.
+
+-- For most implementations, physical files will normally be block-buffered
+-- and terminals will normally be line-buffered. (the IO interface provides
+-- operations for changing the default buffering of a handle tho.)
-\begin{code}
--- handle types are 'show'ed when printing error msgs, so
+data BufferMode
+ = NoBuffering | LineBuffering | BlockBuffering (Maybe Int)
+ deriving (Eq, Ord, Show)
+ {- Read instance defined in IO. -}
+
+-- ---------------------------------------------------------------------------
+-- IORefs
+
+newtype IORef a = IORef (STRef RealWorld a) deriving Eq
+
+newIORef :: a -> IO (IORef a)
+newIORef v = stToIO (newSTRef v) >>= \ var -> return (IORef var)
+
+readIORef :: IORef a -> IO a
+readIORef (IORef var) = stToIO (readSTRef var)
+
+writeIORef :: IORef a -> a -> IO ()
+writeIORef (IORef var) v = stToIO (writeSTRef var v)
+
+modifyIORef :: IORef a -> (a -> a) -> IO ()
+modifyIORef ref f = readIORef ref >>= \x -> writeIORef ref (f x)
+
+-- deprecated, use modifyIORef
+updateIORef :: IORef a -> (a -> a) -> IO ()
+updateIORef = modifyIORef
+
+-- ---------------------------------------------------------------------------
+-- Show instance for Handles
+
+-- handle types are 'show'n when printing error msgs, so
-- we provide a more user-friendly Show instance for it
-- than the derived one.
-instance Show Handle__Type where
+
+instance Show HandleType where
showsPrec p t =
case t of
- ErrorHandle iot -> showString "error " . showsPrec p iot
ClosedHandle -> showString "closed"
SemiClosedHandle -> showString "semi-closed"
ReadHandle -> showString "readable"
- WriteHandle -> showString "writeable"
- AppendHandle -> showString "writeable (append)"
- ReadWriteHandle -> showString "read-writeable"
+ WriteHandle -> showString "writable"
+ AppendHandle -> showString "writable (append)"
+ ReadWriteHandle -> showString "read-writable"
+ ReadSideHandle _ -> showString "read-writable (duplex)"
instance Show Handle where
- showsPrec p (Handle h) =
+ showsPrec p (FileHandle h) = showHandle p h
+ showsPrec p (DuplexHandle h _) = showHandle p h
+
+showHandle p h =
let
-#if defined(__CONCURRENT_HASKELL__)
-#ifdef __HUGS__
- hdl_ = unsafePerformIO (primTakeMVar h)
-#else
-- (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
-#else
- hdl_ = unsafePerformIO (stToIO (readVar h))
-#endif
+ case h of { MVar h# ->
+ case takeMVar# h# s# of { (# s2# , r #) ->
+ case putMVar# h# r s2# of { s3# ->
+ (# s3#, r #) }}})
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" )
+ showHdl (haType hdl_)
+ (showString "loc=" . showString (haFilePath hdl_) . showChar ',' .
+ showString "type=" . showsPrec p (haType hdl_) . showChar ',' .
+ showString "buffering=" . showBufMode (unsafePerformIO (readIORef (haBuffer hdl_))) (haBufferMode hdl_) . showString "}" )
where
- showHdl :: Handle__Type -> ShowS -> ShowS
+ showHdl :: HandleType -> ShowS -> ShowS
showHdl ht cont =
case ht of
- ClosedHandle -> showsPrec p ht . showString "}\n"
- ErrorHandle _ -> showsPrec p ht . showString "}\n"
+ ClosedHandle -> showsPrec p ht . showString "}"
_ -> cont
- showBufMode :: FILE_OBJECT -> BufferMode -> ShowS
- showBufMode fo bmo =
+ showBufMode :: Buffer -> BufferMode -> ShowS
+ showBufMode buf bmo =
case bmo of
NoBuffering -> showString "none"
LineBuffering -> showString "line"
BlockBuffering Nothing -> showString "block " . showParen True (showsPrec p def)
where
def :: Int
- def = unsafePerformIO (getBufSize fo)
-\end{code}
+ def = bufSize buf
-%*********************************************************
-%* *
-\subsection[BufferMode]{Buffering modes}
-%* *
-%*********************************************************
-
-Three kinds of buffering are supported: line-buffering,
-block-buffering or no-buffering. These modes have the following
-effects. For output, items are written out from the internal
-buffer according to the buffer mode:
-
-\begin{itemize}
-\item[line-buffering] the entire output buffer is written
-out whenever a newline is output, the output buffer overflows,
-a flush is issued, or the handle is closed.
-
-\item[block-buffering] the entire output buffer is written out whenever
-it overflows, a flush is issued, or the handle
-is closed.
-
-\item[no-buffering] output is written immediately, and never stored
-in the output buffer.
-\end{itemize}
-
-The output buffer is emptied as soon as it has been written out.
-
-Similarly, input occurs according to the buffer mode for handle {\em hdl}.
-\begin{itemize}
-\item[line-buffering] when the input buffer for {\em hdl} is not empty,
-the next item is obtained from the buffer;
-otherwise, when the input buffer is empty,
-characters up to and including the next newline
-character are read into the buffer. No characters
-are available until the newline character is
-available.
-\item[block-buffering] when the input buffer for {\em hdl} becomes empty,
-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. (the IO interface provides
-operations for changing the default buffering of a handle tho.)
+-- ------------------------------------------------------------------------
+-- Exception datatype and operations
-\begin{code}
-data BufferMode
- = NoBuffering | LineBuffering | BlockBuffering (Maybe Int)
- deriving (Eq, Ord, Show)
- {- Read instance defined in IO. -}
-
-\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
-
-foreign import "libHS_cbits" "allocMemory__" unsafe
- allocMemory__ :: 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
| 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
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}
-%* *
-%*********************************************************
+-- --------------------------------------------------------------------------
+-- Primitive throw
-\begin{code}
throw :: Exception -> a
throw exception = raise# exception
ioException :: IOException -> IO a
ioException err = IO $ \s -> throw (IOException err) s
-\end{code}
-%*********************************************************
-%* *
-\subsection{Type @IOError@}
-%* *
-%*********************************************************
+-- ---------------------------------------------------------------------------
+-- IOError type
-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.
+-- 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}
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.
+ (Maybe Handle) -- the handle used by the action flagging the
+ -- the error.
+ IOErrorType -- what it was.
+ String -- location.
+ String -- error type specific information.
+ (Maybe FilePath) -- filename the error is related to.
instance Eq IOException where
- (IOError h1 e1 loc1 str1) == (IOError h2 e2 loc2 str2) =
- e1==e2 && str1==str2 && h1==h2 && loc1 == loc2
+ (IOError h1 e1 loc1 str1 fn1) == (IOError h2 e2 loc2 str2 fn2) =
+ e1==e2 && str1==str2 && h1==h2 && loc1==loc2 && fn1==fn2
data IOErrorType
= AlreadyExists | HardwareFault
userError :: String -> IOError
userError str = UserError str
-\end{code}
-
-Predicates on IOError; little effort made on these so far...
-\begin{code}
+-- ---------------------------------------------------------------------------
+-- Predicates on IOError
isAlreadyExistsError :: IOError -> Bool
-isAlreadyExistsError (IOException (IOError _ AlreadyExists _ _)) = True
-isAlreadyExistsError _ = False
+isAlreadyExistsError (IOException (IOError _ AlreadyExists _ _ _)) = True
+isAlreadyExistsError _ = False
isAlreadyInUseError :: IOError -> Bool
-isAlreadyInUseError (IOException (IOError _ ResourceBusy _ _)) = True
-isAlreadyInUseError _ = False
+isAlreadyInUseError (IOException (IOError _ ResourceBusy _ _ _)) = True
+isAlreadyInUseError _ = False
isFullError :: IOError -> Bool
-isFullError (IOException (IOError _ ResourceExhausted _ _)) = True
-isFullError _ = False
+isFullError (IOException (IOError _ ResourceExhausted _ _ _)) = True
+isFullError _ = False
isEOFError :: IOError -> Bool
-isEOFError (IOException (IOError _ EOF _ _)) = True
-isEOFError _ = False
+isEOFError (IOException (IOError _ EOF _ _ _)) = True
+isEOFError _ = False
isIllegalOperation :: IOError -> Bool
-isIllegalOperation (IOException (IOError _ IllegalOperation _ _)) = True
-isIllegalOperation _ = False
+isIllegalOperation (IOException (IOError _ IllegalOperation _ _ _)) = True
+isIllegalOperation _ = False
isPermissionError :: IOError -> Bool
-isPermissionError (IOException (IOError _ PermissionDenied _ _)) = True
-isPermissionError _ = False
+isPermissionError (IOException (IOError _ PermissionDenied _ _ _)) = True
+isPermissionError _ = False
isDoesNotExistError :: IOError -> Bool
-isDoesNotExistError (IOException (IOError _ NoSuchThing _ _)) = True
-isDoesNotExistError _ = False
+isDoesNotExistError (IOException (IOError _ NoSuchThing _ _ _)) = True
+isDoesNotExistError _ = False
isUserError :: IOError -> Bool
isUserError (UserError _) = True
-isUserError _ = False
-\end{code}
+isUserError _ = False
-Showing @IOError@s
+-- ---------------------------------------------------------------------------
+-- Showing IOErrors
-\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 (IOError hdl iot loc s fn) =
showsPrec p iot .
- showChar '\n' .
(case loc of
"" -> id
- _ -> showString "Action: " . showString loc . showChar '\n') .
- showHdl .
+ _ -> showString "\nAction: " . showString loc) .
+ (case hdl of
+ Nothing -> id
+ Just h -> showString "\nHandle: " . showsPrec p h) .
(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)
+ _ -> showString "\nReason: " . showString s) .
+ (case fn of
+ Nothing -> id
+ Just name -> showString "\nFile: " . showString name)
\end{code}
projects / ghc-hetmet.git / blobdiff