[Haskell-cafe] Success and one last issue with Data.Binary
David Leimbach
leimy2k at gmail.com
Tue Jun 2 17:07:24 EDT 2009
On Tue, Jun 2, 2009 at 1:56 PM, Thomas DuBuisson <thomas.dubuisson at gmail.com
> wrote:
> Again, I can't reproduce your problem. Are you getting data through
> some previous Binary instance before calling the routines you show us
> here?
Ah good question... I'm calling "decode", but it's not clear that it's even
running my instance of Get!!!!
If I have a lazy bytestring, and call "decode", which instance of "Get"
runs? Probably not my 9P message version I'll bet...
geeze... :-(
> The code I tested with is below - I've tried it with both
> 'getSpecific' paths by commenting out one path at a time. Both
> methods work, shown below.
>
> Thomas
>
> *Main> decode test :: RV
> Rversion {size = 19, mtype = 101, tag = 65535, msize = 1024, ssize =
> 6, version = Chunk "9P2000" Empty}
> *Main> :q
> Leaving GHCi.
> [... edit ...]
> [1 of 1] Compiling Main ( p.hs, interpreted )
> Ok, modules loaded: Main.
> *Main> decode test :: RV
> Rerror {size = 19, mtype = 101, tag = 65535, ssize = 1024, ename =
> Chunk "\NUL\NUL\ACK\NUL9P2000" Empty}
> *Main>
>
>
>
> import Data.ByteString.Lazy
> import Data.Binary
> import Data.Binary.Get
>
> data RV =
> Rversion { size :: Word32,
> mtype :: Word8,
> tag :: Word16,
> msize :: Word32,
> ssize :: Word16,
> version :: ByteString}
> | Rerror { size :: Word32,
> mtype :: Word8,
> tag :: Word16,
> ssize :: Word16,
> ename :: ByteString}
> deriving (Eq, Ord, Show)
>
> instance Binary RV where
> put = undefined
> get = do s <- getWord32le
> mtype <- getWord8
> getSpecific s mtype
> where
> getSpecific s mt
> {- = do t <- getWord16le
> ms <- getWord32le
> ss <- getWord16le
> v <- getRemainingLazyByteString
> return $ Rversion {size=s,
> mtype=mt,
> tag=t,
> msize=ms,
> ssize=ss,
> version=v}
> -}
> = do t <- getWord16le
> ss <- getWord16le
> e <- getLazyByteString $ fromIntegral ss
> return $ Rerror {size=s,
> mtype=mt,
> tag=t,
> ssize=ss,
> ename=e}
>
> test = pack
> [ 0x13
> , 0x00
> , 0x00
> , 0x00
> , 0x65
> , 0xff
> , 0xff
> , 0x00
> , 0x04
> , 0x00
> , 0x00
> , 0x06
> , 0x00
> , 0x39
> , 0x50
> , 0x32
> , 0x30
> , 0x30
> , 0x30 ]
>
> On Tue, Jun 2, 2009 at 1:31 PM, David Leimbach <leimy2k at gmail.com> wrote:
> >
> >
> > On Tue, Jun 2, 2009 at 1:28 PM, John Van Enk <vanenkj at gmail.com> wrote:
> >>
> >> I think Thomas' point was that some other branch in `getSpecific' is
> >> running. Is there a chance we can see the rest of `getSpecific'?
> >
> > Sure: (In the meantime, I'll try the suggested code from before)
> > get = do s <- getWord32le
> > mtype <- getWord8
> > getSpecific s mtype
> > where
> > getSpecific s mt
> > | mt == mtRversion = do t <- getWord16le
> > ms <- getWord32le
> > ss <- getWord16le
> > v <-
> > getRemainingLazyByteString
> > return $ MessageClient $
> > Rversion {size=s,
> >
> > mtype=mt,
> >
> > tag=t,
> >
> > msize=ms,
> >
> > ssize=ss,
> >
> > version=v}
> > | mt == mtRerror = do t <- getWord16le
> > ss <- getWord16le
> > e <- getLazyByteString $
> > fromIntegral ss
> > return $ MessageClient $
> Rerror
> > {size=s,
> >
> > mtype=mt,
> >
> > tag=t,
> >
> > ssize=ss,
> >
> > ename=e}
> >
> >>
> >> On Tue, Jun 2, 2009 at 4:20 PM, David Leimbach <leimy2k at gmail.com>
> wrote:
> >> > The thing is I have 19 bytes in the hex string I provided:
> >> > 1300000065ffff000400000600395032303030
> >> > That's 38 characters or 19 bytes.
> >> > The last 4 are 9P2000
> >> > 13000000 = 4 bytes for 32bit message payload, This is little endian
> >> > for 19
> >> > bytes total.
> >> > 65 = 1 byte for message type. 65 is "Rversion" or the response type
> for
> >> > a
> >> > Tversion request
> >> > ffff = 2 bytes for 16bit message "tag".
> >> >
> >> > 00040000 = 4 bytes for the 32 bit maximum message payload size I'm
> >> > negotiating with the 9P server. This is little endian for 1024
> >> > 0600 = 2 bytes for 16 bit value for the length of the "string" I'm
> >> > sending.
> >> > The strings are *NOT* null terminated in 9p, and this is little
> endian
> >> > for
> >> > 6 bytes remaining.
> >> > 5032303030 = 6 bytes the ASCII or UTF-8 string "9P2000" which is 6
> bytes
> >> > 4 + 1 + 2 + 4 + 2 + 6 = 19 bytes.
> >> > As far as I can see, my "get" code does NOT ask for a 20th byte, so
> why
> >> > am I
> >> > getting that error?
> >> > get = do s <- getWord32le -- 4
> >> > mtype <- getWord8 -- 1
> >> > getSpecific s mtype
> >> > where
> >> > getSpecific s mt
> >> > | mt == mtRversion = do t <- getWord16le -- 2
> >> > ms <- getWord32le -- 4
> >> > ss <- getWord16le -- 2
> >> > v <-
> >> > getRemainingLazyByteString -- remaining should be 6 bytes.
> >> > return $ MessageClient $
> >> > Rversion {size=s,
> >> >
> >> > mtype=mt,
> >> >
> >> > tag=t,
> >> >
> >> > msize=ms,
> >> >
> >> > ssize=ss,
> >> >
> >> > version=v}
> >> > Should I file a bug? I don't believe I should be seeing an error
> >> > message
> >> > claiming a failure at the 20th byte when I've never asked for one.
> >> > Dave
> >> >
> >> > On Tue, Jun 2, 2009 at 10:51 AM, John Van Enk <vanenkj at gmail.com>
> wrote:
> >> >>
> >> >> Thomas,
> >> >>
> >> >> You're correct. For some reason, I based my advice on the thought
> that
> >> >> 19 was the minimum size instead of 13.
> >> >>
> >> >> On Tue, Jun 2, 2009 at 1:24 PM, Thomas DuBuisson
> >> >> <thomas.dubuisson at gmail.com> wrote:
> >> >> >> I think getRemainingLazyByteString expects at least one byte
> >> >> > No, it works with an empty bytestring. Or, my tests do with binary
> >> >> > 0.5.0.1.
> >> >> >
> >> >> > The specific error means you are requiring more data than
> providing.
> >> >> > First check the length of the bytestring you pass in to the to
> level
> >> >> > decode (or 'get') routine and walk though that to figure out how
> much
> >> >> > it should be consuming. I notice you have a guard on the
> >> >> > 'getSpecific' function, hopefully you're sure the case you gave us
> is
> >> >> > the branch being taken.
> >> >> >
> >> >> > I think the issue isn't with the code provided. I cleaned up the
> >> >> > code
> >> >> > (which did change behavior due to the guard and data declarations
> >> >> > that
> >> >> > weren't in the mailling) and it works fine all the way down to the
> >> >> > expected minimum of 13 bytes.
> >> >> >
> >> >> >
> >> >> >> import Data.ByteString.Lazy
> >> >> >> import Data.Binary
> >> >> >> import Data.Binary.Get
> >> >> >>
> >> >> >> data RV =
> >> >> >> Rversion { size :: Word32,
> >> >> >> mtype :: Word8,
> >> >> >> tag :: Word16,
> >> >> >> msize :: Word32,
> >> >> >> ssize :: Word16,
> >> >> >> version :: ByteString}
> >> >> >> deriving (Eq, Ord, Show)
> >> >> >
> >> >> >> instance Binary RV where
> >> >> >> get = do s <- getWord32le
> >> >> >> mtype <- getWord8
> >> >> >> getSpecific s mtype
> >> >> >> where
> >> >> >> getSpecific s mt = do t <- getWord16le
> >> >> >> ms <- getWord32le
> >> >> >> ss <- getWord16le
> >> >> >> v <- getRemainingLazyByteString
> >> >> >> return $ Rversion {size=s,
> >> >> >> mtype=mt,
> >> >> >> tag=t,
> >> >> >> msize=ms,
> >> >> >> ssize=ss,
> >> >> >> version=v }
> >> >> >> put _ = undefined
> >> >> >
> >> >>
> >> >>
> >> >>
> >> >> --
> >> >> /jve
> >> >
> >> >
> >> > _______________________________________________
> >> > Haskell-Cafe mailing list
> >> > Haskell-Cafe at haskell.org
> >> > http://www.haskell.org/mailman/listinfo/haskell-cafe
> >> >
> >> >
> >>
> >>
> >>
> >> --
> >> /jve
> >
> >
> > _______________________________________________
> > Haskell-Cafe mailing list
> > Haskell-Cafe at haskell.org
> > http://www.haskell.org/mailman/listinfo/haskell-cafe
> >
> >
>
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