From: "Iñaki Baz Castillo" <ibc@...>
Date: 2011-08-23T04:55:26+09:00
Subject: Re: Possble bug in Ruby parser (Fixnum#times within "case" statement)

2011/8/22 Ryan Davis <ryand-ruby@zenspider.com>:
> Needless complexity is needless and will _always_ bite you sooner or later.
>
> Compare:
>
> def receive_data(data)
>  @buffer << data
>
>  @parser.reset
>  @parser_nbytes = 0
>  parse_headers
>  get_body
>  process_request
> end
>
> catch :done do
>  loop do
>    receive_data get_data
>  end
> end


This is a very simplistic and urrealistic approach for a parsing on
top of TCP in which you can receive incomplete data in each TCP
package so must wait until the event reactor (EventMachine in this
case) calls receive_data(data) again.

For example, the method parse_headers() reads data from the buffer and
determines if it's a complete protocol message (just headers, as in a
HTTP request) or not. If so, it returns and sets @state=:body, true so
the case statement gets true and the loop continues, but now it goes
to get_body() method. This method, similary, checks whether there are
Content-Length bytes in the buffer. If so, it has the complete body,
sets @state=:finished and returns true. If not, it returns false so
the while ends. Next time the TCP server receives pending data, the
reactor calls receive_data(data) again so the case enters again in
get_body() method and reads, probably, the entire buffer to complete
the body.

It's much more complex than your code which cannot work in a real TCP
server in which nobody can expect to receive the entire protocol
message in a single TCP package.


-- 
Iñaki Baz Castillo
<ibc@aliax.net>