[Haskell-cafe] Data.Binary and little endian encoding
dons at galois.com
Sun May 17 09:08:29 EDT 2009
> Am Freitag, 15. Mai 2009 06:37:22 schrieb Don Stewart:
> > timd:
> > > On a related matter, I am using Data.Binary to serialise data from
> > > haskell for use from other languages. [...]
> > [...]
> > Yep, it's possible, just not portably so. Google for Data.Binary IEEE
> > discussions.
> I think this topic pops up over and over again, and the proposed "solutions"
> are no solutions at all, neither from a performance point of view, nor from an
> ease of use point of view. Proposing insane bit fiddling by hand when all one
> technically needs is often a "peek" or "poke" amounts to simply ignoring an
> API problem. ;-)
> I think most problems can be fixed in a rather pragmatic way by adding a few
> functions to the binary package:
> Add to Data.Binary.Builder:
> putFloatIEEEbe :: Float -> Builder
> putDoubleIEEEbe :: Double -> Builder
> putFloatIEEEle :: Float -> Builder
> putDoubleIEEEle :: Double -> Builder
> putFloatIEEEhost :: Float -> Builder
> putDoubleIEEEhost :: Double -> Builder
> Add to Data.Binary.Get:
> getFloatIEEEbe :: Get Float
> getDoubleIEEEbe :: Get Double
> getFloatIEEEle :: Get Float
> getDoubleIEEEle :: Get Double
> getFloatIEEEhost :: Get Float
> getDoubleIEEEhost :: Get Double
> Add to Data.Binary.Put:
> putFloatIEEEbe :: Float -> Put
> putDoubleIEEEbe :: Double -> Put
> putFloatIEEEle :: Float -> Put
> putDoubleIEEEle :: Double -> Put
> putFloatIEEEhost :: Float -> Put
> putDoubleIEEEhost :: Double -> Put
> The *host functions are basically peek/poke for most platforms. The *le/*be
> functions can use peek/poke if the endianess matches (compile time decision)
> *and* the alignment is OK for the given platform (runtime decision). Non-IEEE
> platforms always have to do the bit fiddling internally, but all this is
> hidden behind the above API.
> IIRC I have proposed something similar 1-2 years ago, but I can't remember any
> reason why this hasn't been implemented. Any comments on the above functions?
Patches are welcome.
> One final remarks: I think the low level functions of the binary package
> should really keep the notions of "endianess" and "alignment constraints"
> separate, something which isn't done currently: The *host functions have
> alignment restrictions, the *be/*le functions don't. There is no good reason
> for this non-orthogonality.
That seems reasonable.
More information about the Haskell-Cafe