jruby: not properly registering interests for IO coming from ffi(?)

[HoneyryderChuck]

I'm writing a ruby client for net-snmp using ffi and making it compatible with celluloid-io. For MRI, it has been working alright. I'm having issues with jruby 9k, though.

All the examples have been done using 9.1.1.0 (latest release). The following example works:

# example script of creating io object from fd and passing it to the selector
io = IO.for_fd 2 # stderrr
IO.select [], [io] #=> [], [io]
selector = NIO::Selector.new
selector.register(io, :w)

Problem is when I'm acting on a file descriptor coming from the snmp session structure. As it's all done in C, I'm "deep-fetching" from the structure and initializing an IO object, which would then be passed to the reactor.

...
require 'nio'
io = IO.for_fd(fd_from_the_snmp_structure)
# this works, btw
IO.select [], [io] #=> [], [io]

selector = NIO::Selector.new
selector.register(io, :w) #=>
ArgumentError: mode not supported for this object: r
  register at org/nio4r/Nio4r.java:172

as previously stated, it works under MRI. It might be a bug in jruby, it's a bit hard for me to figure out, problem seems however to be in the symbolToInterestOps in the java extension(?), possibly, maybe. Is the first such report, or do I have to dig a bit deeper?

[tarcieri]

@TiagoCardoso1983 that indicates the underlying NIO channel does not support being monitored for reading. I'd suggest opening a JRuby issue and we can discuss there.

[HoneyryderChuck]

I had the feeling it was on jruby. Done.

[tarcieri]

We can continue the discussion on the JRuby thread. I am guessing that if it's resolved though, you might run into issues with #67.