From: Robert Klemme <shortcutter@...>
Date: 2012-09-05T16:40:54+09:00
Subject: Re: Socket Decorator

On Tue, Sep 4, 2012 at 7:53 PM, Bernhard Brodowsky <lists@ruby-forum.com> wrote:
> Robert Klemme wrote in post #1074648:
>> On Tue, Sep 4, 2012 at 2:34 PM, Bernhard Brodowsky
>> <lists@ruby-forum.com> wrote:
>>> Hi, I am implementing a special kind of socket that takes an io object
>>> (usually a socket) as its argument and then behaves like a socket, but
>>> does some transformations before/after it sends/receives, so in pseudo
>>> code, it could look about like this:
>>
>>> But now I would like to implement the io interface like all those other
>>> io classes,
>>
>> Why?  I'd rather have a clean separation, i.e. you have a class [...]

> My transformed socket can send arbitrary strings, so a client can send
> anything he likes. The advantage of implementing the same interface as
> the other IO classes is that my transformed socket can be reused in more
> different ways and passed to other methods that take IO streams as
> arguments, for example YAML::load(transformed_socket) might read yaml
> directly from my transformed socket, which is not possible if I have a
> different interface.

Ah, I see.  Basically you are defining a different message format
across the wire but otherwise want to retain all the other
functionality.  I have two ideas for this:

- look at how Ruby's SSL implementation does it
- define a "default forwarding" like this:

class Wrapper # maybe inherit BasicObject
  def initialize(socket)
    @socket = socket or raise "Invalid nil socket"
  end

  def write...
  def read...
  # other methods that either accept data to send or return data read

  def method_missing(*a, &b)
    __wrap__(@socket.send(*a, &b))
  end

private
  def __wrap__(obj)
    obj.equal?(@socket) ? self : obj
  end

# variant
  def method_missing(*a, &b)
    __wrap__(@socket.send(*a) do |*x|
      b[*x.map! {|e| __wrap__(e)}]
    end)
  end
end

> Thanks a lot, I alredy switched to String#<< and String#slice!. The
> message size sent through the internal socket is fixed, but from
> outside, it appears like a normal IO stream, so a client may call gets,
> but several internal messages may have to be read until a newline
> character is found. Or read(n) may be called for n != block_size, so a
> buffer is definitely necessary.

I see.

Kind regards

robert

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