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Table of Contents

Programming POE

Ah, a book. Who'd have thunk it.

Authors: Rocco, Sungo, DrForr

The outline we're working with looks something like this (as with all things, it won't look anything like this in the end game. suck it up):

/Introduction to POE

  • What is POE?
    • Why should I use it?
    • Where do I find it?
    • When and how was it developed?
  • General Concepts
    • Events
    • States
    • Sessions
    • Heaps
  • POErl
    • Basic Rules
    • Session Creation
    • State Parameters
    • Methods
      • post
      • yield
      • delay


  • Overview
    • POE's event loop is flexible enough to handle GUIs like Tk and Gtk, and network events all at the same time.
    • Events in POE interact with Components.
    • Components can be network servers like IRC or HTTPD
    • Components can spawn their own children, much like how Apache handles connections.
  • Low-Level layers
    • Sessions are like processes on your typical O/S.
    • Just like processes, Sessions are non-blocking, which means that they're always ready to accept input.
    • Of course, processes are no use unless they can accept input and produce output.
    • Wheels take on this challenge. Wheels can deal with file handles, like Wheel::ReadWrite, or network events like Wheel::SocketFactory.
  • Components
    • An Event can be a webserver access. POE::Component::Client::HTTPD can manage that.
    • A webserver has to return something to the user, so, assuming we have a class called "Game", stick some text into a webpage and return it.
  • Wheel
  • Session (process)
  • Filters and the Driver
    • Filters take data from a source (socket, filehandle, and other Filters.
    • They take the incoming data and buffer, block and/or transform it in some manner.
    • Driver::SysRW
  • Kernel

/Advanced POE

  • Component Internals
    • Anatomy of a component
    • A sample component.
  • Inside Filters
    • Anatomy of a filter.
      • Filters take an input handle and store the data collected somewhere.
    • A sample filter.
      • The Block Filter collects N bytes of data
      • And the Filter posts an event to send the post-processed data out.
      • We'll simply separate the string into integers, identifiers, and everything else.
      • Using the Block filter as a sample, we'll accumulate text into a buffer.
      • Instead of returning the entire buffer
        • If there's a number at the start of the buffer, send that back.
        • If there's an identifier at the start, send that back.
        • Couldn't find anything to process, so just return the first character.
  • Network protocol modules
    • HTTP
      • Sample app: metavoyeur. I have a command-line interface to fifteen or so search voyeurs. It polls them periodically and generates combined popularity numbers. it may be too big to present, though.
      • Micrometavoyeur: a scaled down version.
    • IRC
    • Others (Just as important, but web applications will likely get the most time and attention)
      • DNS
      • ping
      • PCap
  • General purpose components
    • Components don't need to be I/O bound.
      • JobQueue
    • Text and Speech
      • Text parsing
        • RSS
        • Tokenize
        • Speech synthesis and recognition
        • POE::Component::Festival - Speech generation
        • POE::Component::SPX - Speech Recognition
    • IKC
      • Kernels can communicate with one another.
    • Uncategorized Stuff
      • Notes:
        • The introductory section might cover projects using POE. Lots of sexy stuff is going on.
        • This uncategorized section is just free-association outside the main outline. I'll weed through stuff here and put the useful bits into the outline above.
        • I could be on the bad kind of crack. Someone tell me some sense before I go nuts on this. :)
        • Don't eat the brown acid! --coral

Uncategorized Topics

These topics are from the original outline. They should be integrated into the book or swept under a carpet.

  • How events are dispatched.
    • The precedence order of dispatched events.
    • Synchronous vs. asynchronous events.
      • post() vs. call()
      • Why not to use call()
      • When call() is necessary.
    • Signal propagation from the operating system to your code.
      • Signals are bad, but this is useful information.
  • Extending sessions with wheels.
    • How wheels work.
      • Anatomy of a wheel.
      • They plug into sessions.
      • They add states into sessions, like viral DNA in an unsuspecting cell.
      • They take their tentacles back out when destroyed.
      • They cannot be given to another session!
      • Nice place for a diagram: wheels, filters, and drivers.
      • Design flaws, and a future without them?
    • How to write a wheel.
      • Parts of a wheel.
  • Extending sessions with interfaces.
    • Interfaces are just boilerplate sets of states.
    • Interfaces are defined in session constructors.
    • So far nobody has ever used them.
  • Extending wheels with filters.
    • How filters work.
    • How to write a new filter.
    • Jeff has practically finished this session.
  • Extending programs with components.
    • What components are.
    • Component interfaces.
      • Event driven: request and response messages. Wallowing in the POE-ness of it all.
      • Function interface with callbacks. Hiding POE behind an innocent looking function library.
      • Object interface with callbacks. Hiding POE behind a suspicious looking set of objects.
  • Customizing event dispatch with new sessions.
    • How sessions work inside. What goes on in there?
      • Route events to handlers.
      • They do the _default thing, not Kernel.
      • NFA vs. Session.
      • Sessions own resources, but Kernel does that for us. Sessions are basically keys into the Kernel's data structures.
    • How sessions don't work. What's wrong with them?
      • Can't tell which events a session supports without the session's cooperation. That's called "encapsulation", and it's a feature.
      • A new kind of session could publish its event handler names, etc.
    • Design and build a new session from scratch.
      • Something useful, fun, and not too big. Ch'yeah!
  • Supporting new event loops. Event substrates.
    • Deep guts magic.
    • Requires a firm grasp of POE::Preprocessor.
    • How to roll a new event substrate.
      • Dear gods, no!
  • Macros
    • Templates for Perl source code.
    • const
    • enum
    • macro
    • conditional compilation (deprecated?)
    • What happens when const/enum names clash with other source code.
      • Hint: It's bad.
  • *nix vs Win32 environment (kz15)
    • fork() implementations
    • Wheels and filters
    • Creating standalone executables in Win32
      • Hint: sub RUNNING_IN_HELL () { $^O eq 'MSWin32' }
Rocco adds here: Creating standalone executables in Win32 has been documented (and tested with perl2exe) in POE 0.21. See the notes towards the end of the POE::Preprocessor perldoc/man page.

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