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

[John Van Enk]

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