[RFC] try* interfaces in io_splice 2.2.0.18.g3025

[Eric Wong <normalperson@yhbt.net>]

$ gem install --pre io_splice

It's also up at git://bogomips.org/ruby_io_splice.git in master.

This adds IO.trytee and IO.trysplice which behave like their
non-trying counterparts with the following exceptions:

1) IO::Splice::F_NONBLOCK is implied/forced.
   IO.trysplice may still block if the non-pipe descriptor blocks, so
   users should always set non-blocking on that descriptor.

2) Unlike the established Kgio, this returns :EAGAIN instead
   of :wait_readable or :wait_writable.  This is because only
   the user of the code can tell which descriptor is actually
   full/empty.

There is no IO.tryvmsplice, I haven't figured out if IO.vmsplice is
useful or not and non-blocking I/O with iovecs is so painful to deal
with it's not worth it.

The flags argument of all these interfaces is now optional and will
default to zero (and IO::Splice::F_NONBLOCK for IO.try{splice,tee}).

-- 
Eric Wong