Request for review / feedback: SocketChannel.poll()

[Rob McKenna]

Hi folks,

After adding Net.poll() in 7184932, Alan suggested I implement a poll 
method in SocketChannel to allow for the temporary use of non-blocking 
SocketChannels in a blocking fashion. So this is my first public effort 
and is likely quite rough around the edges.

Apologies for the rushed approach, but I'd really like to gather 
feedback as soon as possible as we're running quite late for 8. (its 
been a busy couple of months unfortunately)

http://cr.openjdk.java.net/~robm/sc.poll/webrev.01/

One thing to note is that in the implementation of poll we have 3 calls 
to Net.poll() within 3 conditionals. The reason for this is to allow for 
simultaneous calls to sc.poll(OP_READ) and sc.poll(OP_WRITE).

Another part in particular that I'd like to highligh is the awkward 
timeout. The spec does say that this method will block if (e.g.) a read 
operation is performed in another thread and we poll for OP_READ in our 
thread. That is to say, the timeout only comes into play once we have 
the appropriate locks. I've also followed the poll system calls 
semantics for the timeout parameter. (<0: block indefinitely, 0: return 
immediately, >0: block for specified interval)

The test is still a work in progess, but any feedback at all would be 
gratefully received.

     -Rob