Class: NIO::Selector

Inherits:
Object
  • Object
show all
Defined in:
lib/nio/selector.rb,
ext/nio4r/selector.c

Overview

Selectors monitor IO objects for events of interest

Instance Method Summary collapse

Constructor Details

#initializeObject

Methods



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# 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

Instance Method Details

#closeObject

Close this selector and free its resources



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# File 'lib/nio/selector.rb', line 131

def close
  @lock.synchronize do
    return if @closed

    @wakeup.close rescue nil
    @waker.close rescue nil
    @closed = true
  end
end

#closed?Boolean

Is this selector closed?

Returns:

  • (Boolean)


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# File 'lib/nio/selector.rb', line 142

def closed?; @closed end

#deregister(io) ⇒ Object

Deregister the given IO object from the selector



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# File 'lib/nio/selector.rb', line 31

def deregister(io)
  @lock.synchronize do
    monitor = @selectables.delete io
    monitor.close(false) if monitor and not monitor.closed?
    monitor
  end
end

#register(io, interest) ⇒ Object

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?



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# File 'lib/nio/selector.rb', line 19

def register(io, interest)
  @lock.synchronize do
    raise ArgumentError, "this IO is already registered with the selector" if @selectables[io]

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

    monitor
  end
end

#registered?(io) ⇒ Boolean

Is the given IO object registered with the selector?

Returns:

  • (Boolean)


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# File 'lib/nio/selector.rb', line 40

def registered?(io)
  @lock.synchronize { @selectables.has_key? io }
end

#select(timeout = nil) ⇒ Object

Select which monitors are ready



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# File 'lib/nio/selector.rb', line 45

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
    end

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

    if block_given?
      result = 0
    else
      result = []
    end

    ready_readers.each do |io|
      if io == @wakeup
        # Clear all wakeup signals we've received by reading them
        # Wakeups should have level triggered behavior
        begin
          @wakeup.read_nonblock(1024)

          # Loop until we've drained all incoming events
          redo
        rescue Errno::EWOULDBLOCK
        end

        return
      else
        monitor = @selectables[io]
        monitor.readiness = :r

        if block_given?
          yield monitor
          result += 1
        else
          result << monitor
        end
      end
    end

    ready_readwriters = ready_readers & ready_writers
    ready_writers = ready_writers - ready_readwriters

    [[ready_writers, :w], [ready_readwriters, :rw]].each do |ios, readiness|
      ios.each do |io|
        monitor = @selectables[io]
        monitor.readiness = readiness

        if block_given?
          yield monitor
          result += 1
        else
          result << monitor
        end
      end
    end

    result
  end
end

#select_each(timeout = nil, &block) ⇒ Object

Select for ready monitors, successively yielding each one in a block



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# File 'lib/nio/selector.rb', line 111

def select_each(timeout = nil, &block)
  selected = select(timeout)
  return unless selected
  selected.each(&block)
  selected.size
end

#wakeupObject

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.



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# File 'lib/nio/selector.rb', line 124

def wakeup
  # Send the selector a signal in the form of writing data to a pipe
  @waker << "\0"
  nil
end