From: why the lucky stiff <ruby-talk@...>
Date: 2005-01-12T06:03:53+09:00
Subject: Re: question about YAML over sockets

Ken Collins (pine29@myfastmail.com) wrote:
> > > As far as I can tell, YAML.load will not return until the sender closes
> > > the socket. Is this true? If true, is this desirable?
> > > 
> > If you need to have YAML.load return before you've closed the socket, 
> > send a pause indicator "\n...\n".  YAML.load will return and you can 
> > read further documents from the same IO.
> > 
> > _why
> 
> I tried sending the pause indicator using a variety of plausible IO
> methods (write, print, puts, etc.) but without success. The receiver
> listed below prints the data but only after five seconds. 
> 

The YAML loader tries to read enough to fill its buffer.  It might be
better to use IO#readline.  The only way to do this for now is to
overload IO#read so it will read a line at a time.

Here's a replacement receiver:

  require "socket"
  require "yaml"
  
  socket = TCPSocket.new("localhost", 5555)
  class << socket
      alias _read read
      def read( len )
          readline
      end
  end
  data = YAML.load(socket)
  p data

Also, the parser isn't stopping at the pause indicator properly and is
requiring an additional newline.

Here's a replacement sender:

  data = { 'a' => [1,2,3], 'b' => 43 }
  server = TCPServer.new("localhost", 5555)
  socket = server.accept
  YAML.dump(data, socket)
  socket.write "\n...\n\n"
  sleep 5

Stream parsing like this is totally untested.   Time to remedy the
situation.

_why