[Haskell-cafe] Binary serialization, was Re: Abstraction leak
phil at kantaka.co.uk
Wed Jul 4 09:50:42 EDT 2007
On Wed, Jul 04, 2007 at 09:44:13PM +1000, Donald Bruce Stewart wrote:
>Binary instances are pretty easy to write. For a simple data type:
> > instance Binary Exp where
> > put (IntE i) = do put (0 :: Word8)
> > put i
> > put (OpE s e1 e2) = do put (1 :: Word8)
> > put s
> > put e1
> > put e2
> > get = do tag <- getWord8
> > case tag of
> > 0 -> liftM IntE get
> > 1 -> liftM3 OpE get get get
That's quite verbose! Plus I'm a bit concerned by the boxing implied
by those IntE / OpE constructors in get. If you were using those
values in a pattern match on the result of get, would the compiler be
able to eliminate them and refer directly to the values in the source
>The Data.Binary comes with one tool to derive these. The DrIFT preprocessor
>also can, as can Stefan O'Rear's SYB deriver.
>I just write them by hand, or use the tool that comes with the lib.
>More docs here,
This doesn't seem to deal with endianness. Am I missing something?
>> >>world, you could operate on the packets in place in Haskell where
>> >>possible and save the deserialization overhead...
>> >Data.ByteString.* for this.
Ah, does Data.Binary fuse with ByteString.* then?
>Hack those bytes! Quickly! :-)
It's a shame the layout definition is so verbose. Erlang's is quite
compact. I wonder if something could be done with template haskell to
translate an Erlang-style data layout definition to the Data.Binary
(Bonus points for being able to parse ASN.1 and generate appropriate
Haskell datatypes & serialization primitives automatically :-) )
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