Re: [Haskell-cafe] Success and one last issue with Data.Binary

Perhaps there's some place in your code that's forcing the lazy read to consume more. Perhaps you could replace it with an explict (and strict) getBytes[1] in combination with remaining[2]? Is there a reason you want to use lazy byte strings rather than forcing full consumption? Do the 9P packets generally have a lot of trailing useless data? 1. http://hackage.haskell.org/packages/archive/binary/0.5.0.1/doc/html/Data-Bin... 2. http://hackage.haskell.org/packages/archive/binary/0.5.0.1/doc/html/Data-Bin... On Tue, Jun 2, 2009 at 4:28 PM, David Leimbach wrote:

On Tue, Jun 2, 2009 at 10:24 AM, Thomas DuBuisson wrote:

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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.

I've shown that I am not trying to decode more than I'm providing.  I've asked, expliciitly, for 13 bytes, and then "remaining", and the library is complaining about the 20th byte.

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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.

The other branch is Rerror, which is a shorter message decode stream.  Unfortunately, I can't get Debug.Trace to show anything to prove it's taking this fork of the code.  I suppose I could unsafePerformIO :-) Perhaps I just need a new version of "binary"??  I'll give it a go and try your version.  But I need to decode over a dozen message types, so I will need a case or guard or something. Dave

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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.

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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)

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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