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NIO::Selector

Selectors monitor IO objects for events of interest

Public Class Methods

new() click to toggle source

Create a new NIO::Selector

# File lib/nio/selector.rb, line 5
def initialize
  @selectables = {}
  @lock = Mutex.new

  # Other threads can wake up a selector
  @wakeup, @waker = IO.pipe
  @closed = false
end

Public Instance Methods

close() click to toggle source

Close this selector and free its resources

# File lib/nio/selector.rb, line 114
def close
  @lock.synchronize do
    return if @closed

    @wakeup.close rescue nil
    @waker.close rescue nil
    @closed = true
  end
end
closed?() click to toggle source

Is this selector closed?

# File lib/nio/selector.rb, line 125
def closed?; @closed end
deregister(io) click to toggle source

Deregister the given IO object from the selector

# File lib/nio/selector.rb, line 37
def deregister(io)
  @lock.synchronize do
    monitor = @selectables.delete io
    monitor.close(false) if monitor and not monitor.closed?
    monitor
  end
end
empty?() click to toggle source
# File lib/nio/selector.rb, line 127
def empty?
  @selectables.empty?
end
register(io, interest) click to toggle source

Register interest in an IO object with the selector for the given types of events. Valid event types for interest are:

  • :r - is the IO readable?

  • :w - is the IO writeable?

  • :rw - is the IO either readable or writeable?

# File lib/nio/selector.rb, line 19
def register(io, interest)
  @lock.synchronize do
    if closed?
      raise IOError, "selector is closed"
    end

    if monitor = @selectables[io]
      raise ArgumentError, "this IO is already registered with the selector as #{monitor.interests.inspect}"
    end

    monitor = Monitor.new(io, interest, self)
    @selectables[monitor.io] = monitor

    monitor
  end
end
registered?(io) click to toggle source

Is the given IO object registered with the selector?

# File lib/nio/selector.rb, line 46
def registered?(io)
  @lock.synchronize { @selectables.has_key? io }
end
select(timeout = nil) click to toggle source

Select which monitors are ready

# File lib/nio/selector.rb, line 51
def select(timeout = nil)
  @lock.synchronize do
    readers, writers = [@wakeup], []

    @selectables.each do |io, monitor|
      readers << io if monitor.interests == :r || monitor.interests == :rw
      writers << io if monitor.interests == :w || monitor.interests == :rw
      monitor.readiness = nil
    end

    ready_readers, ready_writers = Kernel.select readers, writers, [], timeout
    return unless ready_readers # timeout or wakeup

    selected_monitors = Set.new

    ready_readers.each do |io|
      if io == @wakeup
        # Clear all wakeup signals we've received by reading them
        # Wakeups should have level triggered behavior
        @wakeup.read(@wakeup.stat.size)
        return
      else
        monitor = @selectables[io]
        monitor.readiness = :r
        selected_monitors << monitor
      end
    end

    ready_writers.each do |io|
      monitor = @selectables[io]
      monitor.readiness = case monitor.readiness
      when :r
        :rw
      else
        :w
      end
      selected_monitors << monitor
    end

    if block_given?
      selected_monitors.each do |m|
        yield m
      end
      selected_monitors.size
    else
      selected_monitors
    end
  end
end
wakeup() click to toggle source

Wake up a thread that’s in the middle of selecting on this selector, if any such thread exists.

Invoking this method more than once between two successive select calls has the same effect as invoking it just once. In other words, it provides level-triggered behavior.

# File lib/nio/selector.rb, line 107
def wakeup
  # Send the selector a signal in the form of writing data to a pipe
  @waker.write "\00""
  nil
end

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