network.rb

### network.rb - Andy Brown <neorab@gmail.com> [21 March, 2010]
###============================================================================
### Network class for communication with the game server.

require 'socket'
require 'fiber'

## Network Class
##-----------------------------------------------------------------------
## Rather than threads, the Network class uses fibers from Ruby 1.9.  It
## turns out that fibers are a fantastic implement nonblocking sockets.
## It's very similar to a Fun from Erlang.  A little more experimentaion
## and it might be exactly like a Fun.  I really wish that Ruby threads
## were more like Erlang threads though and I could just spawn it instead
## of jumping through hoops with fibers.  It seems to work well though.
class Network
  
  # constructor
  #~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  # This is the thing that makes the Network object come to
  # life.  We will throw the third switch.  Throw IT!
  def initialize(ip, port)
    @socket, @running = TCPSocket.new(ip, port), true
    
    @outbox, @outbox_mutex = Array.new, Mutex.new
    @inbox,  @inbox_mutex  = Array.new, Mutex.new
    
    @out_fiber = Fiber.new do
      while(@running)
        @outbox_mutex.synchronize do
          unless(@outbox.empty?)
            msg = @outbox.delete_at(0)
            @socket.puts(msg)
          end
        end
        Fiber.yield
      end
    end
    
    @in_fiber = Fiber.new do
      while(@running)
        @inbox_mutex.synchronize do
          begin
            msg = @socket.recv_nonblock(100)
            @inbox.push(msg)
          rescue Errno::EAGAIN
            # Should something happen (?)
          end
        end
        Fiber.yield
      end
    end
  end
  
  ## Run both Box handlers
  def update
    @out_fiber.resume
    @in_fiber.resume
  end
  
  ## Add a message to the oubox (mutexed)
  def send(message)
    @outbox_mutex.synchronize do
      @outbox.push(message)
    end
  end
  
  ## Pop a message off the inbox (mutexed)
  def recv
    @inbox_mutex.synchronize do
      unless(@inbox.empty?)
        return @inbox.delete_at(0)
      else
        return false
      end
    end
  end
  
end