+We guess the size of the buffer required as 20% extra for
+expanded tabs, and enlarge it if necessary.
+
+\begin{code}
+#if __GLASGOW_HASKELL__ < 303
+mayBlock fo thing = thing
+
+writeCharOffAddr :: Addr -> Int -> Char -> IO ()
+writeCharOffAddr addr off c
+ = _casm_ ``*((char *)%0+(int)%1)=(char)%2;'' addr off c
+#endif
+
+getErrType :: IO Int
+#if __GLASGOW_HASKELL__ < 303
+getErrType = _casm_ ``%r = ghc_errtype;''
+#else
+getErrType = _ccall_ getErrType__
+#endif
+
+slurpFileExpandTabs :: FilePath -> IO (Addr,Int)
+slurpFileExpandTabs fname = do
+ bracket (openFile fname ReadMode) (hClose)
+ (\ handle ->
+ do sz <- hFileSize handle
+ if sz > toInteger (maxBound::Int)
+ then IOERROR (userError "slurpFile: file too big")
+ else do
+ let sz_i = fromInteger sz
+ sz_i' = (sz_i * 12) `div` 10 -- add 20% for tabs
+ chunk <- allocMem sz_i'
+ trySlurp handle sz_i' chunk
+ )
+
+trySlurp :: Handle -> Int -> Addr -> IO (Addr, Int)
+trySlurp handle sz_i chunk =
+#if __GLASGOW_HASKELL__ == 303
+ wantReadableHandle "hGetChar" handle >>= \ handle_ ->
+ let fo = haFO__ handle_ in
+#elif __GLASGOW_HASKELL__ > 303
+ wantReadableHandle "hGetChar" handle $ \ handle_ ->
+ let fo = haFO__ handle_ in
+#else
+ readHandle handle >>= \ handle_ ->
+ let fo = filePtr handle_ in
+#endif
+ let
+ (I# chunk_sz) = sz_i
+
+ tAB_SIZE = 8#
+
+ slurpFile :: Int# -> Int# -> Addr -> Int# -> Int# -> IO (Addr, Int)
+ slurpFile c off chunk chunk_sz max_off = slurp c off
+ where
+
+ slurp :: Int# -> Int# -> IO (Addr, Int)
+ slurp c off | off >=# max_off = do
+ let new_sz = chunk_sz *# 2#
+ chunk' <- reAllocMem chunk (I# new_sz)
+ slurpFile c off chunk' new_sz (new_sz -# (tAB_SIZE +# 1#))
+ slurp c off = do
+ intc <- mayBlock fo (_ccall_ fileGetc fo)
+ if intc == ((-1)::Int)
+ then do errtype <- getErrType
+ if errtype == (ERR_EOF :: Int)
+ then return (chunk, I# off)
+ else constructErrorAndFail "slurpFile"
+ else case chr intc of
+ '\t' -> tabIt c off
+ ch -> do writeCharOffAddr chunk (I# off) ch
+ let c' | ch == '\n' = 0#
+ | otherwise = c +# 1#
+ slurp c' (off +# 1#)
+
+ tabIt :: Int# -> Int# -> IO (Addr, Int)
+ -- can't run out of buffer in here, because we reserved an
+ -- extra tAB_SIZE bytes at the end earlier.
+ tabIt c off = do
+ writeCharOffAddr chunk (I# off) ' '
+ let c' = c +# 1#
+ off' = off +# 1#
+ if c' `remInt#` tAB_SIZE ==# 0#
+ then slurp c' off'
+ else tabIt c' off'
+ in do
+
+ -- allow space for a full tab at the end of the buffer
+ -- (that's what the max_off thing is for),
+ -- and add 1 to allow room for the final sentinel \NUL at
+ -- the end of the file.
+ (chunk', rc) <- slurpFile 0# 0# chunk chunk_sz (chunk_sz -# (tAB_SIZE +# 1#))
+#if __GLASGOW_HASKELL__ < 404
+ writeHandle handle handle_
+#endif
+ if rc < (0::Int)
+ then constructErrorAndFail "slurpFile"
+ else return (chunk', rc+1 {-room for sentinel-})
+
+
+reAllocMem :: Addr -> Int -> IO Addr
+reAllocMem ptr sz = do
+ chunk <- _ccall_ realloc ptr sz
+ if chunk == nullAddr
+#if __GLASGOW_HASKELL__ >= 400
+ then fail "reAllocMem"
+#else
+ then fail (userError "reAllocMem")
+#endif
+ else return chunk
+
+allocMem :: Int -> IO Addr
+allocMem sz = do
+#if __GLASGOW_HASKELL__ < 303
+ chunk <- _ccall_ malloc sz
+ if chunk == nullAddr
+ then fail (userError "allocMem")
+ else return chunk
+#else
+ chunk <- _ccall_ allocMemory__ sz
+ if chunk == nullAddr
+ then constructErrorAndFail "allocMem"
+ else return chunk
+#endif