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) the built-in Data.Binary.decodeFile function doesn't close its handle when it is done (same reason as my earlier examples).
However, I think probably the real blame here should probably go to Data.Binary which doesn't attempt to check that it has consumed all of its input after doing a "decode". If "decode" completes and there is unconsumed data, it should probably raise an error (it already raises errors for premature EOF). There's no reason for it not to, since it does not provide the unconsumed data to the caller when its done, anyway...
I would have expected this to fix my problems: binEof :: Get () binEof = do more <- not <$> isEmpty when more $ error "expected EOF" decodeFully :: Binary b => B.ByteString -> b decodeFully = runGet (get << binEof) where a << b = a >>= (\x -> b >> return x) but even when using decodeFully, it still doesn't close the handle. Shouldn't Data.Binary.Get.isEmpty force a file handle close in the case that it returns True? Tim Newsham http://www.thenewsh.com/~newsham/