-% -----------------------------------------------------------------------------
-% $Id: PrelIOBase.lhs,v 1.12 1999/08/23 12:53:25 keithw Exp $
+% ------------------------------------------------------------------------------
+% $Id: PrelIOBase.lhs,v 1.27 2000/07/08 18:17:40 panne Exp $
%
-% (c) The AQUA Project, Glasgow University, 1994-1998
+% (c) The University of Glasgow, 1994-2000
%
\section[PrelIOBase]{Module @PrelIOBase@}
\begin{code}
{-# OPTIONS -fno-implicit-prelude -#include "cbits/stgio.h" #-}
-#include "cbits/error.h"
+#include "config.h"
+#include "cbits/stgerror.h"
#ifndef __HUGS__ /* Hugs just includes this in PreludeBuiltin so no header needed */
module PrelIOBase where
import PrelST
import PrelBase
-import {-# SOURCE #-} PrelException ( ioError )
-import PrelST ( ST(..), STret(..) )
import PrelMaybe ( Maybe(..) )
-import PrelAddr ( Addr(..), nullAddr )
-import PrelPack ( unpackCString )
+import PrelAddr ( Addr(..) )
import PrelShow
+import PrelList
+import PrelDynamic
+import PrelPack ( unpackCString )
#if !defined(__CONCURRENT_HASKELL__)
import PrelArr ( MutableVar, readVar )
#endif
#ifdef __HUGS__
-#define cat2(x,y) x/**/y
-#define CCALL(fun) cat2(prim_,fun)
#define __CONCURRENT_HASKELL__
#define stToIO id
#define unpackCString primUnpackString
-#else
-#define CCALL(fun) _ccall_ fun
-#define ref_freeStdFileObject (``&freeStdFileObject''::Addr)
#endif
#ifndef __PARALLEL_HASKELL__
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}
#ifndef __HUGS__
newtype IO a = IO (State# RealWorld -> (# State# RealWorld, a #))
{-# INLINE (>>) #-}
{-# INLINE (>>=) #-}
m >> k = m >>= \ _ -> k
- return x = IO $ \ s -> (# s, x #)
+ return x = returnIO x
m >>= k = bindIO m k
fail s = error s -- not ioError?
- -- not required but worth having around
-fixIO :: (a -> IO a) -> IO a
-fixIO m = stToIO (fixST (ioToST . m))
-
liftIO :: IO a -> State# RealWorld -> STret RealWorld a
liftIO (IO m) = \s -> case m s of (# s', r #) -> STret s' r
(# new_s, a #) -> unIO (k a) new_s
)
+returnIO :: a -> IO a
+returnIO x = IO (\ s -> (# s, x #))
#endif
\end{code}
%*********************************************************
%* *
+\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}
+
+#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
+
+eqForeignObj :: ForeignObj -> ForeignObj -> Bool
+eqForeignObj mp1 mp2
+ = unsafePerformIO (primEqForeignObj mp1 mp2) /= (0::Int)
+
+foreign import "eqForeignObj" unsafe primEqForeignObj :: ForeignObj -> ForeignObj -> IO Int
+
+instance Eq ForeignObj where
+ p == q = eqForeignObj p q
+ p /= q = not (eqForeignObj p q)
+#endif /* ndef __HUGS__ */
+
+#if defined(__CONCURRENT_HASKELL__)
+newtype Handle = Handle (MVar Handle__)
+#else
+newtype Handle = Handle (MutableVar RealWorld Handle__)
+#endif
+
+instance Eq Handle where
+ (Handle h1) == (Handle h2) = h1 == h2
+
+{-
+ 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]
+ }
+
+{-
+ Internally, we classify handles as being one
+ of the following:
+-}
+data Handle__Type
+ = ErrorHandle IOException
+ | ClosedHandle
+ | SemiClosedHandle
+ | ReadHandle
+ | WriteHandle
+ | AppendHandle
+ | ReadWriteHandle
+
+
+-- 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}
+%* *
+%*********************************************************
+
+\begin{code}
+-- 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
+ 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"
+
+instance Show Handle where
+ showsPrec p (Handle 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
+ 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"
+ ErrorHandle _ -> 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}
+
+%*********************************************************
+%* *
+\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.)
+
+\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
+ | 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@}
%* *
%*********************************************************
flagged.
\begin{code}
-data IOError
- = IOError
+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
| ResourceBusy | ResourceExhausted
| ResourceVanished | SystemError
| TimeExpired | UnsatisfiedConstraints
- | UnsupportedOperation | UserError
+ | UnsupportedOperation
| EOF
-#ifdef _WIN32
+#if defined(cygwin32_TARGET_OS) || defined(mingw32_TARGET_OS)
| ComError Int -- HRESULT
#endif
deriving (Eq)
SystemError -> "system error"
TimeExpired -> "timeout"
UnsatisfiedConstraints -> "unsatisified constraints" -- ultra-precise!
- UserError -> "failed"
UnsupportedOperation -> "unsupported operation"
EOF -> "end of file"
-#ifdef _WIN32
+#if defined(cygwin32_TARGET_OS) || defined(mingw32_TARGET_OS)
ComError _ -> "COM error"
#endif
userError :: String -> IOError
-userError str = IOError Nothing UserError "" str
+userError str = UserError str
\end{code}
Predicates on IOError; little effort made on these so far...
\begin{code}
isAlreadyExistsError :: IOError -> Bool
-isAlreadyExistsError (IOError _ AlreadyExists _ _) = True
-isAlreadyExistsError _ = False
+isAlreadyExistsError (IOException (IOError _ AlreadyExists _ _)) = True
+isAlreadyExistsError _ = False
isAlreadyInUseError :: IOError -> Bool
-isAlreadyInUseError (IOError _ ResourceBusy _ _) = True
-isAlreadyInUseError _ = False
+isAlreadyInUseError (IOException (IOError _ ResourceBusy _ _)) = True
+isAlreadyInUseError _ = False
isFullError :: IOError -> Bool
-isFullError (IOError _ ResourceExhausted _ _) = True
-isFullError _ = False
+isFullError (IOException (IOError _ ResourceExhausted _ _)) = True
+isFullError _ = False
isEOFError :: IOError -> Bool
-isEOFError (IOError _ EOF _ _) = True
-isEOFError _ = False
+isEOFError (IOException (IOError _ EOF _ _)) = True
+isEOFError _ = False
isIllegalOperation :: IOError -> Bool
-isIllegalOperation (IOError _ IllegalOperation _ _) = True
-isIllegalOperation _ = False
+isIllegalOperation (IOException (IOError _ IllegalOperation _ _)) = True
+isIllegalOperation _ = False
isPermissionError :: IOError -> Bool
-isPermissionError (IOError _ PermissionDenied _ _) = True
-isPermissionError _ = False
+isPermissionError (IOException (IOError _ PermissionDenied _ _)) = True
+isPermissionError _ = False
isDoesNotExistError :: IOError -> Bool
-isDoesNotExistError (IOError _ NoSuchThing _ _) = True
-isDoesNotExistError _ = False
+isDoesNotExistError (IOException (IOError _ NoSuchThing _ _)) = True
+isDoesNotExistError _ = False
isUserError :: IOError -> Bool
-isUserError (IOError _ UserError _ _) = True
-isUserError _ = False
+isUserError (UserError _) = True
+isUserError _ = False
\end{code}
Showing @IOError@s
#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 IOError where
+instance Show IOException where
showsPrec p (IOError hdl iot loc s) = showString s . showChar '\n'
#else
-instance Show IOError where
+instance Show IOException where
showsPrec p (IOError hdl iot loc s) =
showsPrec p iot .
showChar '\n' .
constructErrorAndFail :: String -> IO a
constructErrorAndFail call_site
= constructError call_site >>= \ io_error ->
- ioError io_error
+ ioError (IOException io_error)
constructErrorAndFailWithInfo :: String -> String -> IO a
constructErrorAndFailWithInfo call_site reason
= constructErrorMsg call_site (Just reason) >>= \ io_error ->
- ioError io_error
+ ioError (IOException io_error)
\end{code}
and grab these values when generating
\begin{code}
-constructError :: String -> IO IOError
+constructError :: String -> IO IOException
constructError call_site = constructErrorMsg call_site Nothing
-constructErrorMsg :: String -> Maybe String -> IO IOError
+constructErrorMsg :: String -> Maybe String -> IO IOException
constructErrorMsg call_site reason =
- CCALL(getErrType__) >>= \ errtype ->
- CCALL(getErrStr__) >>= \ str ->
+ getErrType__ >>= \ errtype ->
+ getErrStr__ >>= \ str ->
let
iot =
case (errtype::Int) of
in
return (IOError Nothing iot call_site msg)
\end{code}
-
-File names are specified using @FilePath@, a OS-dependent
-string that (hopefully, I guess) maps to an accessible file/object.
-
-\begin{code}
-type FilePath = String
-\end{code}
-
-%*********************************************************
-%* *
-\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}
-
-#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)
-
-{-
- Double sigh - ForeignObj is needed here too to break a cycle.
--}
-data ForeignObj = ForeignObj ForeignObj# -- another one
-instance CCallable ForeignObj
-instance CCallable ForeignObj#
-#endif /* ndef __HUGS__ */
-
-#if defined(__CONCURRENT_HASKELL__)
-newtype Handle = Handle (MVar Handle__)
-#else
-newtype Handle = Handle (MutableVar RealWorld Handle__)
-#endif
-
-{-
- 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
- }
-
-{-
- Internally, we classify handles as being one
- of the following:
--}
-data Handle__Type
- = ErrorHandle IOError
- | ClosedHandle
- | SemiClosedHandle
- | ReadHandle
- | WriteHandle
- | AppendHandle
- | ReadWriteHandle
-
-
--- 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
- 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"
-
-instance Show Handle where
- showsPrec p (Handle 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
- 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"
- ErrorHandle _ -> 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 (CCALL(getBufSize) fo)
-
-mkBuffer__ :: FILE_OBJECT -> Int -> IO ()
-mkBuffer__ fo sz_in_bytes = do
- chunk <-
- case sz_in_bytes of
- 0 -> return nullAddr -- this has the effect of overwriting the pointer to the old buffer.
- _ -> do
- chunk <- CCALL(allocMemory__) sz_in_bytes
- if chunk == nullAddr
- then ioError (IOError Nothing ResourceExhausted "mkBuffer__" "not enough virtual memory")
- else return chunk
- CCALL(setBuf) fo chunk sz_in_bytes
-
-\end{code}
-
-%*********************************************************
-%* *
-\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.)
-
-\begin{code}
-data BufferMode
- = NoBuffering | LineBuffering | BlockBuffering (Maybe Int)
- deriving (Eq, Ord, Show)
- {- Read instance defined in IO. -}
-
-\end{code}
projects / ghc-hetmet.git / blobdiff