From: Mikael Brockman <mikael@...>
Date: 2004-11-26T22:17:03+09:00
Subject: [ANN] Multiplexer - linear non-blocking I/O

Blocking I/O is really easy to use.  But when you use it to write
servers, you run into problems: you can't run two blocking syscalls
simultaneously.  So if you're writing a huge file to some guy, every
other client is stalled, and no one new can connect.  Unacceptable, for
many types of servers.  They need non-blocking I/O.

Non-blocking I/O is a lot more annoying to use.  Instead of going

| write "Hello.  What's your name?"
| name = read_line
| write "How do you do, #{name}?"
| state = read_line
| write "It's nice to hear that you're #{state}, #{name}."

we have to make weird state machines.

The good news: we can use callcc to make the non-blocking nature
practically invisible.  Multiplexer does that.  Here's how you'd write a
hello server:

| class Test < Multiplexer::Handler
|   def handle
|     write_line "Hello.  What's your name?"
|     name = read_line
|     write_line "How do you do, #{name}?"
|     state = read_line
|     write_line "It's nice to hear that you're #{state}, #{name}."
|     disconnect
|   end
| end
| 
| def test
|   multiplexer = Multiplexer::Multiplexer.new 0.5
|   multiplexer.listen 31337, Test
|   multiplexer.run
| end
| 
| test

It'll run in one thread.  Multiplexer handles the select(3) calls.

Get it:
http://www.phubuh.org/Projects/nntpu/_darcs/current/multiplexer.rb