Use poll instead of select on platforms where it's available

[cesanta]

Use poll instead of select on platforms where it's available

[cpq]

My thinking is that poll() exists on all unix-like systems.
for windows and friends, we can just implement poll() using, say, select().
So I guess we should just blatantly replace select code with poll code.

[cpq]

We can grab the implementation for windows from
https://github.com/cesanta/mongoose/blob/3.8/mongoose.c#L1231

[mkmik]

poll() conforms to POSIX.1-2001.

Man page on OSX (afaik since 10.5) says:
The poll() system call currently does not support devices.

I guess that this might be a problem for people adding arbitrary FDs, e.g. serial ports on mac. We should have let the user choose which impl, via preprocessor define, and have the select based impl be selected by default on windows.

Later we can also implement kqueue on osx/freebsd and epoll on linux which afaik doesn't have this problem and offers better performance.

[cpq]

That's surprising that poll does not support any FD.
Okay.
If we go preprocessor way, then I see no point in implementing poll for linuks.
Shall we go with epoll() straight away?

[mkmik]

It's just a bug. See also a python bug report about the same issue:
http://bugs.python.org/issue5154

From there it seems that kqueue is also affected by the same thing.
I don't think we should care too much, as long as we allow the user to force select fallback (since we'll already provide it for windows). Software using fossa on osx/linux will be mostly for networking and when not, it's probably for development.

[cpq]

Ok.
I mean, there is little value in adding poll() mechanism, cause it's as slow as select - we should invest in epoll() instead.

[mkmik]

I think it's worth to implement epoll/kqueue and fallback to select, unless there are some interesting platforms which do implement poll but not epoll/kqueue. In that case the advantage of poll over select would be just the maximum number of FDs.

[pujo]

On Windows OS we have the WSAPoll API function available.
I used it in previous Mongoose implementations working perfectly.

http://msdn.microsoft.com/en-us/library/windows/desktop/ms741669

[cpq]

Thanks @pujo .
Note that WSAPoll is present only in recent runtime DLLs, starting from Vista. Older windows runtimes do not have it.

[pujo]

Yes, true, but I think it's not worth to support XP or older Windows.

[cpq]

Rojer, please take this over.
Consider abstracting polling API and make it easy to use different multiplexing methods, like poll, epoll, kqueue.

[schmurfy]

I might be completely wrong on that but from my understanding select is more eficient for small number of descriptors and after certain threshold epool/kqueue take the lead. If that is the case select might be more appropriate in the use case I would use this library (small embedded systems won't handle thousands of connections).

[rojer]

poll() is cumbersome. 3a54681 added support for epoll on linux, and refactoring has been done to make adding support for other mechanisms easier.