Simon Peyton-Jones wrote:
> What about this specification?
>
> hReadByteArray :: Handle -> MutableByteArray a -> Int -> IO Int
> [...]
> hWriteByteArray :: Handle -> MutableByteArray a -> Int -> IO ()
> [...]
> Both may block.
>
> Would that do what you want? If so we can add it to IOExts.
That's not what I had in mind: Given the Glorious FFI lib, Addr would
be much better than MutableByteArrays, and both are one-liners with
foreign import + Posix's read/write. What I want is
hGetBin :: Storable a => Handle -> IO a
hPutBin :: Storable a => Handle -> a -> IO ()
with the following "specification":
--SNIP----SNIP----SNIP----SNIP----SNIP----SNIP----SNIP----SNIP--
import IO
import IOExts(fixIO)
import FFI
import Monad(zipWithM_)
----------------------------------------------------------------------
-- cut'n'paste from
http://www.informatik.uni-muenchen.de/~Sven.Panne/haskell_libs/ffi/Marshal.hs
marshal :: Storable a => a -> IO Addr
marshal x = do
buf <- mallocElem x
poke buf x
return buf
marshalList :: Storable a => [a] -> IO (Int, Addr)
marshalList xs = do
let numElements = length xs
buf <- mallocElems (head xs) numElements
zipWithM_ (pokeElemOff buf) [ 0 .. ] xs
return (numElements, buf)
unmarshalList :: Storable a => Int -> Addr -> IO [a]
unmarshalList numElements buf =
mapM (peekElemOff buf) [ 0 .. numElements-1 ]
inParamWith :: (a -> IO c) -> (c -> Addr) -> (c -> IO b) -> a -> IO b
inParamWith marshal_ selAddr act x = do
marshRes <- marshal_ x
val <- act marshRes
free (selAddr marshRes)
return val
inParam :: Storable a => (Addr -> IO b) -> a -> IO b
inParam = inParamWith marshal id
----------------------------------------------------------------------
-- Hmmm, this looks like a good cadidate for the Obfuscated Haskell Contest. :-)
hGetBin :: Storable a => Handle -> IO a
hGetBin h = fixIO (\x -> inParamWith marshalList snd (peek . snd) =<< (sequence .
replicate (sizeOf x) . hGetChar $ h))
hPutBin :: Storable a => Handle -> a -> IO ()
hPutBin h x = hPutStr h =<< inParam (unmarshalList (sizeOf x)) x
main :: IO ()
main = do
hPutBin stdout (3.141592 :: Float)
hPutBin stdout (12345678 :: Int)
print =<< (hGetBin stdin :: IO Int)
--SNIP----SNIP----SNIP----SNIP----SNIP----SNIP----SNIP----SNIP--
Cheers,
Sven
--
Sven Panne Tel.: +49/89/2178-2235
LMU, Institut fuer Informatik FAX : +49/89/2178-2211
LFE Programmier- und Modellierungssprachen Oettingenstr. 67
mailto:[EMAIL PROTECTED] D-80538 Muenchen
http://www.informatik.uni-muenchen.de/~Sven.Panne
