[darcs-devel] http pipelining

[Simon Marlow]

Stefan O'Rear wrote:

> How about something like:
> 
> data Cookie = C { getData :: L.ByteString }
> fetchURL :: URI -> Cookie           -- sends request when forced, reads responce when deeply forced
> 
> {- sample implementation, ignores the existance of multiple servers and
> the Connection: close header -}
> 
> sock = unsafePerformIO ...
> 
> queue fun = newChan >>= \q -> forkIO (forever (readChan q >>= fun)) >>
>             return q
> 
> writer = unsafePeformIO $ queue $ \ req -> writeRequest sock req
> reader = unsafePeformIO $ queue $ \ var ->
>   readRequest sock (\ bit -> writeChan var (Just bit)) >>
>   writeChan var Nothing
> 
> 
> fetchURL url = unsafePerformIO $ do
>   c <- newChan
>   writeChan writer (fetch url)
>   writeChan reader c

A single queue seems nicer, given that you would otherwise need some 
locking to prevent races between multiple threads (I know this doesn't 
apply to darcs, but still).

>   return $ C $ unsafePerformIO $ getData c

Cheers,
	Simon