[Haskell-cafe] Data.Binary.GetT or ... ?

[Paul Johnson]

On 13/03/10 10:06, Juraj Hercek wrote:
> Hello,
>
> I'm thinking about using Data.Binary to parse binary stream of data. 
> Binary data stream consists of messages which can have one or more 
> (sometimes couple of hundreds) sub-messages.  The stream is spitting 
> out data slowly.
>
> I would like to parse this data with Data.Binary.Get monad, but I 
> would like to send sub-messages to a STM channel while parsing, so 
> "observers" could handle them during parsing process.

I think you could do this by having your top-level Get action return a 
list of IO actions, like this:

    bigGet :: Get ([IO ()])

Then arrange for the parser for each smaller sub-message to return the 
corresponding action.  In this case these actions will be calls to 
"atomic" to run the appropriate STM action.

The trick is in lazyness: the lazy bytestring is read as it comes in, 
and hence is translated to a lazy list of IO actions, which are also 
executed as they come in.

Hope this helps,

Paul.