Class: IO

Inherits:
Object
  • Object
show all
Extended by:
FFI::Library
Defined in:
lib/io/poll.rb,
lib/io/poll.rb

Defined Under Namespace

Modules: Poll Classes: PollFdStruct

Class Method Summary collapse

Class Method Details

.select_using_poll(read, write, error, timeout) ⇒ Object 



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# File 'lib/io/poll.rb', line 90

def IO.select_using_poll(read, write, error, timeout)
  read = [] if read.nil?
  write = [] if write.nil?
  error = [] if error.nil?
  all = read.map { |f| { :io => f, :events => IO::Poll::POLLIN } } +
        write.map { |f| { :io => f, :events => IO::Poll::POLLOUT } } +
        error.map { |f| { :io => f, :events => IO::Poll::POLLERR } }
  pollfds = FFI::MemoryPointer.new(IO::PollFdStruct, all.length)
  all.each_with_index do |poll, i|
    struct = IO::PollFdStruct.new(pollfds[i])
    struct[:fd] = poll[:io].fileno
    struct[:events] = poll[:events]
    struct[:revents] = 0
  end
  ret = IO.poll(pollfds, all.length, timeout)
  if ret < 0
    # error. IO.select() returns nil in this case
    return nil
  elsif 0 == ret
    # timed out, exit fast
    return [[],[],[]]
  else
    # returned some interesting descriptors
    ret_read, ret_write, ret_error = [], [], []
    all.each_with_index do |poll, i|
      # select() will signal unrequested flags (eg POLLNVAL) which must be passed
      # back to the correct read/write/error fdset. So, test what we were requesting,
      # and return the fd if *any* notification occured, even if it wasn't what we asked for
      struct = IO::PollFdStruct.new(pollfds[i])
      next if 0 == struct[:revents]
      ret_read << poll[:io] if poll[:events] == IO::Poll::POLLIN and not struct[:revents].zero?
      ret_write << poll[:io] if poll[:events] == IO::Poll::POLLOUT and not struct[:revents].zero?
      ret_error << poll[:io] if poll[:events] == IO::Poll::POLLERR and not struct[:revents].zero?
    end
    return [ret_read, ret_write, ret_error]
  end # if/else ret
end