[Haskell-cafe] Serializing with alignment

Ben Franksen ben.franksen at online.de
Tue Nov 6 22:33:56 CET 2012

Hi Everyone

I want to implement a binary protocol that, unfortunately, has some 
alignment restrictions. In order to fulfill these, I need access to the 
"current offset" in the bytestring. The binary package does provide a 

  bytesRead :: Get Int64

but only for the Get monad; there is no equivalent for the Put monad.

So my first question: is there a serialization library that offers something 

  bytesWritten :: PutM Int64

Failing that, would you think adding it to binary is a reasonable feature 
request? I have taken a cursory look at the implementation and it looks like 
this is not a matter of simply adding a missing function, but would probably 
need an addition to internal data structures.

I could also try and wrap the PutM from binary with a StateT transformer and 
count the bytes myself. I will probably have to use at least a ReaderT 
wrapper anyway, since I have to pass the byte order as a parameter (byte 
order gets negotiated between client and server, it is not fixed).

I was really hoping that there is some library that has built-in support for 
stateful serialization (alignment, byte-order, etc).

Any pointers, hints, etc are much appreciated.

Ben Franksen
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