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

[David Leimbach]

On Thu, May 14, 2009 at 8:57 PM, David Leimbach <leimy2k at gmail.com> wrote:

>
>
> On Thu, May 14, 2009 at 8:54 PM, Don Stewart <dons at galois.com> 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
>

FYI here's what I've ended up trying to write to negotiate the "version" of
a 9p server:

main = withSocketsDo $
       do
          ainfo <- getAddrInfo Nothing (Just "127.0.0.1") (Just "6872")  --
hardcoded for now, it's an IRC filesystem server
          let a = head ainfo
          sock <- socket AF_INET Stream defaultProtocol
          connect sock (addrAddress a)
          sendAll sock $ (toLazyByteString (putWord32le (fromIntegral (16
::Int32))))
          sendAll sock $ (encode (100 ::Int8))
          sendAll sock $ (toLazyByteString (putWord32le (fromIntegral (1024
::Int32))))
          sendAll sock $ (encode (C.pack "9P2000"))


I feel like I should use wireshark or something to watch the bytes :-)  I'm
not feeling very sure about this.


>
>>
>> -- Don
>>
>
>
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