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In-language commenting

Lua is clever and uses –[[ … –]] for multi-line comments. The usefulness in this scheme is that the syntax used for closing a multi-line comment IS a comment, and no syntax error results if you comment out the opener by adding an extra -, which re-enables the commented out section. The part that I don’t like is how single-line comments are specified, with –. Just IMO, FWIW, etc., I don’t think the same characters used for basic operators should be re-used for something like a comment. Really, shouldn’t a = a — 2 result in a-4?

The same in C99/C++, how does using // to specify a comment really make sense? a //= 2 ? a ///= 2 ? /* */ -style comments are better, I suppose, because they are an obvious nop.

Ideally I think we would be using something that allows for the abuse that Lua’s multi-line comments gives us, without overloading any of the basic operators provided by the language. “ perhaps?

“ Comment

“
Multi-line comment
“

“ “
“ Active multi-line comment?
a //= 37;
“

Maybe, I’m not sure.

There are also languages that allow comments to effectively serve as documentation that is preserved (potentially) at runtime. For example, Python assumes unassigned strings immediately inside a class or function definition are to serve as a documentation block for that section. These documentation blocks can be accessed through runtime introspection, or used with appropriate tooling to generate documentation. This is a great approach from my experience, and perhaps -all- comments should be given the opportunity (optionally) to persist alongside the code for which they are intended.

If one is to take this approach, how does one rectify comment specification with static string initialization? Especially with regards to whitespace (esp. newline) handling? How does one specify to what block of code a comment refers when not at the beginning of a closure of some sort? Is there even any point in preserving these comments for any sort of runtime introspection or should the goal be simply the production of documentation, ala Literate Programming?

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ActionScript

This week I decided to toy with ActionScript/Flash a bit (for the first time, really). I’m using the FlashDevelop IDE, so it’s all free goodness, no shelling out $500 to Adobe. Anyway, I wrote an MP3 player that is devoid of any sort of flash user interface, completely controllable through JavaScript. It’s a mere 162 lines of ActionScript and weighs in at 2071 bytes as an swf. It supports a wide range of operations, load, play, pause, stop, setvolume, getvolume, ispaused, getpauseoffset, getcurrentfile, getduration, getposition, getbytesloaded, getbytestotal, getid3, as well as a number of asynchronous JavaScript callbacks (notifications) on various events, loadcomplete, playcomplete and id3found. You can see it in action with possibly the simplest UI possible here: http://evilcode.net/sjg/player/.

The real question that I am trying to answer for myself is, does eliminating the flash user interface somehow make it [flash] more palatable?

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JavaScript/File-based HTTP request logging

http://httpd.apache.org/docs/2.0/mod/mod_log_config.html

I just had the thought that it should be pretty feasible (if not trivial) to tie JavaScript-based request logging (like Mint and Analytics) to traditional file-based request logging using cookies and/or headers and CustomLog in Apache or similar in other httpd’s.

The question being… Is this somehow useful? I think it potentially could be, I’m just not 100% on how as yet.

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PHP/AJAX file upload with progress bar, part 3

Part 1, Part 2

I pulled this back out over the weekend and did a little work on it. The backend code is now totally functional, however I would consider it to be alpha quality. It just needs to be wrapped in a UI now, check it out and let me know what you think. Try the demo with JavaScript enabled first, once the upload completes you will see the result is a mash-up that looks like PHP’s $_REQUEST/$_FILES. Hit the resulting url again within 60 seconds and you will see the status side of things (Using a GET request, you don’t want to re-post the form data). Total bytes, bytes received, percent complete. Try it again with JavaScript disabled and behold the standard php handler.

Source – Demo

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XSLT shorthand for PHP

As I trudge toward Exhibition v2, I am taking the templating in an entirely new direction. Exhibition deals with XML, a lot of XML. As a direct consequence there is a fairly substantial amount of XSLT. Noticing that XSLT has a very straightforward syntax, I decided to write a little preprocessor to save my fingers some walking later on. Most commands boil down to “command” or “command required_argument” (required_argument usually being an XPath expression). So, that’s exactly what I pruned it down to.

<@ for-each atom @>

versus

<xsl:for-each select=”atom”>

Check it out —

xsltemplate.phps

xsltemplate-test.tpl
xsltemplate-test.xml
xsltemplate-test.xsl
(examples stolen from W3Schools)

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PHP/AJAX file upload with progress bar, part 2

I made some good progress on implementing the server side of things as outlined in my prior post on this subject, but I got lazy as usual. I simply haven’t gotten around to finishing this up, so I decided to throw the code up and make a post about it in the hopes that someone will either badger me into completing it, or find some of what is already there useful. The code as of now implements what could be a reasonably useful (python asyn* inspired) set of utility classes for writing socket applications in PHP. Not that anyone would ever want to do anything like that, of course.

http://evilprojects.com/hacks/

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PHP/AJAX file upload with progress bar

Over the past couple of days I have been pondering adding some file upload functionality to the form classes I have been using for a bit over a year now. History repeats itself, again, time spent pondering instead of just getting on with the nitty gritty means I start thinking about ideal functionality. So, as I pondered how to go about sanely handling file uploads features started coming to mind, and one of them just wouldn’t go away. A semi-realtime inline file upload progress indicator. Well, that doesn’t sound so hard.

I spent some time with Google doing the requisite research to find that there are a number of stumbling blocks. The first being client-side, when a browser window/frame is busy pushing a file or files up the pipe, it seems that it is just that, busy. Which makes it a bit difficult to talk it into displaying updates. This seems to be pretty easily solved by pushing the file upload through a hidden iframe referenced by the target attribute on the form.

That certainly isn’t where the problems end. As luck would have it, not only is the browser happy to be working against us, so is PHP, in more ways than one.

When the execution unit handling the upload gets hit with the POST, it would seem that it likes to make itself busy as well. Ok, so no way to get the status of the file upload from the thread/process actually handling the upload. Apparently there are some patches against PHP to rectify this situation, but until they get committed and see a release they are unusable for most people. I am all for gratuitously hacking my own PHP install, but it seemed like there must be a better way.

I then stumbled across another method. Scan the upload_tmp_dir (PHP INI variable) for files of a known naming scheme, looking for the one with the latest timestamp. The current size of this file could be pushed back to the browser so that it could calculate the upload progress. This method is also not without its glaring faults. The probability of a race condition is too high for any kind of production use. Oh wait, scratch that, I’m starting to sound like a PHP developer, let me rephrase… There is an unavoidable possibility of a race condition, so this method cannot be used. Well… Wait a minute, there is an upload_tmp_dir variable. Why don’t we just generate some kind of unique form id to be passed back to us when we get the POST, then it should be possible to create a directory to have PHP put the file(s) in of a known name, eliminating our race, no? I suppose upload_tmp_dir being read-only is a bit of a stumbling block with that idea, considering we already decided hacks to the PHP source were out. Not to mention PHP probably isn’t going to let us set the variable before it gets busy processing that form data anyway.

Google led me to a couple more resources for accomplishing this throughout the course of my research, but they all involved an external non-PHP script to handle the upload and drop status information somewhere accessible. Unacceptable I say! There must be a way to do it with PHP alone!

I have theorized a method, implementation forthcoming. Here is a brief summary. Have an onSubmit handler frob a PHP script and retrieve a URL to apply to the action property of the form, said PHP script will have just launched a PHP-based very simple webserver. This webserver’s sole purpose in life is to eat POST’s and parse multipart form data. This same PHP script will update an accessible location with the status of the upload. The hidden iframe trick gets used to free up the window with the form in it. This window can now pull upload status via XMLHttpRequest and update a progress bar accordingly. This method also has the benefit of being able to degrade gracefully in the event that JavaScript is unavailable on the client. The default action URL can be implemented as a standard file upload handler.