Re: [Haskell-cafe] Libevent FFI problems

Thanks Adam. It took me some time to realize what you recognized immediately - xptr is useless. Instead I now bind the additional value which might be provided on event creation in a closure since the C code never has to deal with it. And yes, there are many functions missing. For now I just need the event notification to detect file descritor (or socket) changes. Regarding your remark, that the RTS multiplexes IO already I am usure how this works out in practice. The reason I write this wrapper is that I want a network server which can handle thousands of connections. And to not require a permanent thread for each I would like to use something like select in C or Selector in Java. I haven't found something like this in Haskell, hence the libevent wrapper. If you have any information how to write something like this without this wrapper I would be more than happy. Finally the code still leaks FunPtrs as so far I never free them and honestly I don't know when to do this. Any ideas? For reference I have attached a newer version of the wrapper code (removed the TimeVal stuff since I don't need it). Thanks again, Levi On Fri, Jul 25, 2008 at 7:21 PM, Adam Langley wrote:

2008/7/23 Levi Greenspan :

...

I would be grateful for any advices, hints or comments. And I really look forward to the FFI section in the "Real World Haskell" book.

Generally it looks pretty good. I think I'm missing some C code (function "wrapper"). However, libevent is an odd choice to wrap. The RTS already multiplexes IO for Haskell programs. In order not to block the RTS, the libevent using code would have to be in its own kernel thread.

Really, the RTS needs to be ported to libevent rather than an FFI wrapping.

For your specific problem, I see you're allocating xptr, but I don't see that you're ever poking a value into it. Indeed, I can't see that createEvent ever uses 'x'.

Hope that helps.

AGL

-- Adam Langley agl@imperialviolet.org http://www.imperialviolet.org