Re: [libmicrohttpd] Writing response to socket?

[Christian Grothoff]

Hi!

If you are using the external select model, this should be possible.  You'll 
need to use an internal buffer; whenever MHD polls and the buffer is empty, 
you return 0.  Then, once librdf pushes you first copy into the buffer and 
then next time MHD polls you give it to MHD.  If you are able to "defer" 
pushing by librdf until your buffer is not full, you should be able to do this 
with a bounded buffer size.  Naturally, librdf would need to be integrated 
with your main external select loop (that select would need to unblock on RDF 
or MHD activity).

Alternatively, with "thread-per-connection", you could just block on the MHD-
read until RDF pushes; naturally, if RDF pushes before MHD reads you'd again 
need to buffer. So yes, I think this can be done, but may involve some non-
trivial code.

Happy hacking!

Christian

On Thursday 31 December 2009 01:25:11 pm Nicholas J Humfrey wrote:
> Hello,
> 
> I am writing an RDF Triplestore[1] called Redstore[2] using the Redland[3]
>  libraries.
> 
> The HTTP responses could end up being quite large, so I would like to try
>  and stream the results, rather than storing it all in memory first, as I
>  am at the moment.
> 
> Is there a way that I can write directly to the connection socket? I have
>  looked at the callback methods and fileserver_example.c but I can't see
>  how I can tie that into the Redland library API.
> 
> Here are the serializer functions available from Redland:
> librdf_serializer_serialize_stream_to_file()
> librdf_serializer_serialize_stream_to_file_handle()
> librdf_serializer_serialize_stream_to_iostream()
> librdf_serializer_serialize_stream_to_string()
> 
> I am currently using the 'to_string' method and then constructing the HTTP
>  response. In order to use to_file_handle or to_iostream, there seems to be
>  a bit of a control inversion problem. librdf wants to push the results to
>  a socket and libmicrohttpd wants to pull the results.
> 
> Any suggestions?
> 
> 
> Thanks,
> 
> nick.
> 
> 
> [1] http://en.wikipedia.org/wiki/Triplestore
> [2] http://code.google.com/p/redstore/
> [3] http://www.librdf.org/
>