RE: [Haskell-cafe] Data.Binary and little endian encoding

On a related matter, I am using Data.Binary to serialise data from haskell for use from other languages. The Data.Binary encoding of a Double is a long integer for the mantissa, and an int for the exponent. This doesn't work too well for interacting with other languages as I'd need to have an arbitrary precision int type there to decode/encode. The CORBA CDR standard encodes doubles in a big ended fashion like this (excuse my possibly incorrect ascii art): | byte | msb lsb | |------+---------------------------| | 0 | S E6 E0 | | 1 | E10 E9 E8 E7 F3 F2 F1 F0 | | 2 | F11 F4 | | 3 | F19 F12 | | 4 | F27 F20 | | 5 | F35 F28 | | 6 | F43 F36 | | 7 | F51 F44 | Up until now, my code is pure haskell. Is it possible to get at the internal bits of a Double/CDouble in ghc? Or Should I use the FFI and write C to encode something like the above? Tim ________________________________ From: haskell-cafe-bounces@haskell.org [mailto:haskell-cafe-bounces@haskell.org] On Behalf Of David Leimbach Sent: Friday, 15 May 2009 1:58 PM To: Don Stewart Cc: Haskell Cafe Subject: Re: [Haskell-cafe] Data.Binary and little endian encoding On Thu, May 14, 2009 at 8:54 PM, Don Stewart wrote: > I'm speaking specifically of the encode/decode functions. I have no idea how > they're implemented. > > Are you saying that encode is doing something really simple and the default > encodings for things just happen to be big endian? If so, then I understand > the pain.... but it still means I have to roll my own :-) I guess if one must > choose, big endian kind of makes sense, except that the whole world is little > endian now, except for networks :-) (No one *really* cares about anything but > x86 anyway these days right?) Oh, 'encode' has type: encode :: Binary a => a -> ByteString it just encodes with the default instances, which are all network order: http://en.wikipedia.org/wiki/Endianness#Endianness_in_networking Yeah I understand that Big Endian == Network Byte Order... which would be true, if I wasn't talking about Plan 9's 9P protocol which specifies little endian bytes on the wire (as far as I can tell anyway from the man page). Dave -- Don