So am I understanding you correctly that you believe this is not a bug? That the use Data.Binary.decodeFile function leaks a file descriptor and this is proper behavior? I still don't understand your explanation of how isEmpty can return True without having read to EOF. The ByteString continues to contain more data until an EOF is reached. Doesn't one of return (B.null s && L.null ss) force getContents to read until EOF? On Wed, 13 Aug 2008, Don Stewart wrote:
newsham:
Ok, surely at least everyone must agree that this is a bug:
force :: Word8 -> IO Word8 force x = print x >> return x -- force = return . (`using` rnf)
main = do d <- force =<< decodeFile stateFile encodeFile stateFile d where stateFile = "1word32.bin"
test8.hs: 1word32.bin: openBinaryFile: resource busy (file is locked)
Remember that
decodeFile f = liftM decode (L.readFile f)
and
readFile :: FilePath -> IO ByteString readFile f = openBinaryFile f ReadMode >>= hGetContents
where hGetContents sits in a loop, reading chunks,
loop = do c <- S.hGetNonBlocking h k if S.null c then do eof <- hIsEOF h if eof then hClose h >> return Empty else hWaitForInput h (-1) >> loop else do cs <- lazyRead return (Chunk c cs)
while isEmpty is just,
isEmpty :: Get Bool isEmpty = do S s ss _ <- get return (B.null s && L.null ss)
That is, it checks the parsed chunk, it doesn't demand any more reading be done.
So the only way you're going to get that Handle closed by readFile is to ensure you read till EOF is hit. After you decode, just ask keep asking for bytes till EOF, or close it yourself,
decodeFile f = do h <- openFile f ReadMode ss <- L.hGetContents h let e = decode ss rnf e `seq` hClose h
or some such, where you can confirm the decoding as taken place.
Tim Newsham http://www.thenewsh.com/~newsham/