Class: LXC::Extra::Selector

Inherits:
Object
  • Object
show all
Defined in:
lib/lxc/extra/selector.rb

Overview

Provides a way to listen to multiple disparate file descriptors with different callbacks to handle each one.

Example

require 'lxc/extra/selector'
require 'socket'

def repeat_to(socket, selector, out)
  message, *other = socket.recvmsg
  if message.size == 0
    selector.delete(socket)
    return
  end
  out.write(message)
end

selector = LXC::Extra::Selector.new()

# Listen on 20480 and echo output to STDOUT
server = TCPServer.new(20480)
selector.on_select(server) do |server|
  socket = server.accept
  selector.on_select(socket, selector, STDOUT, &method(:repeat_to))
end

# Listen on 20481 and echo output to STDERR
server = TCPServer.new(2049)
selector.on_select(server) do |server|
  socket = server.accept
  selector.on_select(socket, selector, STDERR, &method(:repeat_to))
end

# Do all that listening on one thread!
selector.main_loop

NOTE: This is not presently thread-safe in that adds and deletes must be done on the same thread as the main_loop.

Instance Method Summary collapse

Constructor Details

#initialize ⇒ Selector

Create a new selector.



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# File 'lib/lxc/extra/selector.rb', line 47

def initialize
  @fd_callbacks = {}
end

Instance Method Details

#delete(fd) ⇒ Object

Stop listening to a file descriptor.

Arguments

fd

file descriptor to stop listening to.



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# File 'lib/lxc/extra/selector.rb', line 74

def delete(fd)
  @fd_callbacks.delete(fd)
end

#main_loop ⇒ Object

Listen for any of the given file handles to be ready (with IO.select) and call their callbacks when they are.



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# File 'lib/lxc/extra/selector.rb', line 82

def main_loop
  begin
    while true
      ready = IO.select(@fd_callbacks.keys)
      ready[0].each do |fd|
        callback = @fd_callbacks[fd]
        if callback
          args = [ fd ]
          args += callback[:args] if callback[:args]
          if callback[:callback].call(*args) == :stop
            return
          end
        end
      end
    end
  rescue
    raise
  end
end

#on_select(fd, *args, &callback) ⇒ Object

Add a file descriptor to listen on.

Arguments

fd

file descriptor to listen on.

args

optional set of arguments to pass to callback

callback

callback to call when file descriptor has data available



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# File 'lib/lxc/extra/selector.rb', line 60

def on_select(fd, *args, &callback)
  @fd_callbacks[fd] = {
    :args => args,
    :callback => callback
  }
end