Cross-browser data binding with jQuery

From version 4.0 Internet Explorer has had the ability to bind certain HTML elements to a client-side data source. Pretty much any data you can access with ADO you can use as a data source but the one we've used most commonly at work is XML. By adding some attributes to your HTML elements e.g.

<input type="text" datasrc="#dsoComposers" datafld="compsr_last"/>

you can get them to render out the data from the data source and, in the case of inputs, persist any changes back to the source. Additionally, if you have a multi-row data source and you bind it to a table the contents of the tbody tag are duplicated for each row.

This is very useful for making web applications because:

• you only send the raw data along with a small amount of rendering HTML to the client
• the client edits the data, adding/deleting rows without postbacks
• the client posts back structured data rather than a ton of awkwardly named querystring variables
• you need no presentation code for translating your data to or from HTML

All this considered I thought I'd have a go at creating a simple cross-browser version of this databinding functionality in jQuery with a limited feature set.

Features to implement

For this proof of concept I decided the features I would try and implement were:

• Support for JSON as a data source
• Repeat rendering of a table's tbody section for each item in an array of objects
• CSS class name based way of tying properties of the objects to HTML elements
• Rendering of property values within HTML elements innerHTML or value
• Attaching of event handlers to persist data changes on inputs back to the array data source
• Some ability to reflect programmatic changes to the underlying data source in the bound HTML elements
• Doing the above without needing to fully refresh the HTML every time

Use

Some "template" HTML...

    <table id="info">
      <thead>
        <tr>
          <th>Common name</th>  
          <th>Origin</th>
          <th>First developed</th>
          <th>Use</th>
        </tr>
      </thead>
      <tbody>
        <tr>
          <td class="field[name]"></td>
          <td><input type="text" class="field[origin]"/></td>
          <td class="field[developed]"></td>
          <td class="field[use]"></td>
          <td><button class="field[delete]">Delete Row</button></td>
        </tr>
        <tr>
          <td colspan="4" style="border-bottom: 2px solid #888;"><textarea class="field[comments]" style="width: 100%;"></textarea></td>
        </tr>
      </tbody>
      <tfoot>
        <tr>
          <td colspan="4"><button id="add">Add Item</button></td>
        </tr>
      </tfoot>
    </table>

...some data...

var data = [
   { name: 'Braeburn', origin: 'New Zealand', developed: '1950s, United States', comments: '', use: 'Eating' },
   { name: 'Bramley', origin: 'Southwell, Nottinghamshire, England', developed: 'about 1809', comments: '', use: 'Cooking' },
   { name: 'Cox\'s Orange Pippin', origin: 'Great Britain, New Zealand', developed: 'c. 1829', comments: '', use: 'Eating' },
   { name: 'Empire', origin: 'New York', developed: '1966', comments: 'Lovely white subacid flesh. Tangy taste.', use: 'Eating' },
   { name: 'Granny Smith', origin: 'Australia', developed: '1868, Australia', comments: 'This is the apple once used to represent Apple Records. Also noted as common pie apple.', use: 'Eating or cooking' }
];

...and a small amount of JavaScript...

$(document).ready(function(){
   $('#info').databind(data);
});

The add button handler looks like this...

data.push({ name: '', origin: '', developed: '', comments: '', use: '' });
$('#info').databind(data);

...any code making programmatic changes to the data must recall databind to refresh the bound HTML elements.

Demo

I've set up this quick proof of concept here. I haven't looked at how it performs with large arrays of data but I expect the answer would be badly.

Going forward there may be scope for turning this into a proper jQuery plugin with support for other types of data source and the ability to bind an arbitrary group of elements to some data rather than just a table.

Links

• IE data binding @ MSDN
• jQuery
• I used the stringify function from this JSON library for the debug output

JSLinted and namespaced Mapstraction

I've been using Mapstraction in work over the past few months and now my current project has come to an end I've generated a few Subversion patches of my changes, which include:

• JSLinting the source
• Adding simple namespacing (read "hacking in") with backward compatibity "pollute" mode
• Adding ability to execute event handlers in a particular scope along with a general rework of the event implementation to allow easier extensibility
• Fixing several bugs with the Multimap implementation
• Adding new and refining existing JSDoc comments

Files

Should probably point out that I'm not part of the team that maintain Mapstraction and these aren't "official" patches. Hopefully the bug fixes at least will make it back into the repository though.

• Patch for revision 174 to add all changes
• Patch to revision 174 to add all except namespacing
• mapstraction.js rev174 with patches applied

Notes

The namespacing is on by default so to get it to work with an old page you do need to call mxn.activatePolluteMode() first. Additionally there are a few loose utility functions in the mapstraction file that are also within the namespacing. You can get to three of them (metresToLon, lonToMetres and loadScript) from the mxn.fn namespace so if you have been making use of those you'd have to change your code to mxn.fn.metresToLon() for example. I'm not sure which of the other functions in there people would be likely to make use of so I left it at those three to try and minimise surface area but it wouldn't be a problem to add them all to fn.

There is also some backward compatibility stuff in the events implementation. I modified events so that they pass an eventArgs object rather than the arguments individually, that way the signature of all handlers is the same. This is only activated when you pass the third "scope" argument to addEventListener so old implementations should work as before either being passed no argument for move or a LatLonPoint for click.

Large capacity PMP roundup

After my considerable disappointment at no news of a 160GB iPod Touch from Apple at this year's Macworld I decided to have a look at what the competition is doing in the way of large capacity portable media players.

My criteria

• 40GB or greater disk
• 3" or larger screen (preferably 16:9)

The contenders

Model	Capacity (GB)	Screen (Inches)	Formats	Battery A/V (Hours)	Price
Archos
504	40, 80, 160	4.3"	Video: MPEG-4 Audio: MP3, WMA, WAV	17/5.5	£172.21, £258.99, £394.95
704 WiFi	40, 80	7"	Video: MPEG-4, WMV Audio: MP3, WMA, WAV	25/5.5	£269.99, £368.23
605 WiFi	80, 160	4.3"	Video: MPEG-4, WMV Audio: MP3, WMA, WAV	17/5.5	£214.99, £254.64
705 WiFi	80, 160	7"	Video: MPEG-4, WMV Audio: MP3, WMA, WAV	25/5.5	£269.99, £368.23
Cowon
A3	60	4	Video: DivX, XviD, MPEG 1/2/4, WMV, H.264 Audio: MP3, WMA, FLAC, OGG, AAC, AC3, BSAC, True Audio, WavPack, G.726, CM	25/5.5	£315.95
Q5	60	5	Video: DivX, XviD, MPEG4, WMV Audio: MP3, WMA, ASF, OGG, WAV, FLAC, APE, MPC	13/7	£409.95
iRiver
PMC-140	40	3.5	Video: WMV Audio: MP3, WMA	12/5
PMP-140	40	3.5	Video: AVI, XviD, MPEG-4, MPEG-1 Audio: MP3, WMA, WAV, ASF	10/5

Archos have the most players meeting the criteria with large disk versions up to 160GB however they are let down by poor codec support although you can add support for more by downloading them from their website (at extra cost).

The two Cowon players offer an impressive list of codecs out-of-the-box but they only come in a maximum 60 gigabyte version and are a lot more expensive than in particular the Archos players.

The iRiver players have small disks, small screens and poor codec support but I couldn't find anywhere stocking them anyway so it looks like I couldn't buy one even if I were interested.

Conclusion

The Archos players definitely seem to be the best deal if you're not bothered about having support for a large number of codecs. One big criticism of them however is that, looking at the overview of for example the 605 WiFi on the Archos site, it seems like you're getting loads of features for your money. Reading the small print, however, will tell you that to use some of them you need to buy optional add-ons and they're not cheap. The DVR dock for recording TV is an extra £60, the web browser is £20, the Video podcast plug-in (read iPod compatibility pack featuring H.264 and AAC codecs) is £15! I'm surprised they are allowed to sell the product based on features it doesn't have out of the box and it certainly puts a sting in the tail of the good deal.

NHibernate in Visual Web Developer Express

If you fancy using NHibernate in VWD you'll have trouble because you can't compile your mapping files into the same assembly as your classes. As a result you can't add mappings to your session factory by assembly name or class name.

Thankfully there is a simple solution to this, which I'll demonstrate with the aid of the quickstart example in the NHibernate documentation.

Start by creating all your persistance class files in your App_Code folder with your mapping files (.hbm.xml) alongside. Next, make the alterations to your web.config as outlined in section 1.1 of the quickstart but leave out this line:

<mapping assembly="QuickStart" />

In your mapping files, change the assembly attribute of the root hibernate-mapping element to "App_Code" and remove the namespace attribute if you're not using a namespace (the default behaviour of VWD) e.g:

<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="App_Code">

Finally, copy the code for the NHibernateHelper class from section 1.4 and change its constructor from this:

static NHibernateHelper()
{
   sessionFactory = new Configuration().Configure().BuildSessionFactory();
}

to this:

static NHibernateHelper()
{
   Configuration cfg = new Configuration().Configure();
   cfg.AddDirectory(new System.IO.DirectoryInfo(HttpContext.Current.Server.MapPath(@"~/App_Code/")));
   sessionFactory = cfg.BuildSessionFactory();
}

The original constructor used the mapping element in the web.config to find out which mappings to load, here we're telling it to load all the mapping files it finds in the App_Code folder. You can also use the AddFile method to add individual mapping files.

Merge with "How to Code"

Initially I thought it was a good idea to write separate blogs because people interested in gadgets and codecs aren't necessarily interested in code and databases.

I've since realised three things; that the target audiences were pretty much the same, that dividing my traffic was a bad idea and that I don't really have enough to say or the time to fill two blogs.

So, having just finished copying all the posts over from Derek's How to Code, I'll be deleting it and maintaining just the one from now on.

What a shame I never got to use this snazzy bit of artwork...

Processing instructions and Microsoft XML DOM

If you're using Microsoft's XML DOM you'll find it strips out the encoding attribute from your processing instruction (the <?xml ... ?> bit) when you get the value of the Xml property. This is because it always returns unicode regardless of what the input encoding was. As unicode is the default for the XML specification, no encoding attribute is required.

The Save method, which writes the contents of the DOM document to a file, maintains the original encoding. If you need your XML in the original encoding after some manipulation in the DOM then you can do this:

xmldoc.Save("c:\blah.xml")
Set fs = Server.CreateObject("Scripting.FileSystemObject")
Set ts = fs.OpenTextFile("c:\blah.xml")
strXml = ts.ReadAll

Programmatically changing a processing instruction

Looks a bit dodgy but this is the way to do it:

Set pi = xmldoc.createProcessingInstruction("xml", "version=""1.0"" encoding=""UTF-16""")
xmldoc.replaceChild pi, xmldoc.childNodes.Item(0)

Mapstraction "to do" list

I've been using Mapstraction to implement draggy maps in our platforms at work for the past month or so and thought I'd share some of the problems I came across so, should you decide to do the same, you know what to watch out for. The issues I've come across below I've fixed for the APIs with which I was working and I'll be submitting the changes back to the project in the near future.

I should say first that Mapstraction is an awesome piece of work that frees you from having to commit to one mapping provider. When clients don't want to pay for maps so you give them Google and then change their mind when Google start inserting advertisements, all you have to do is change one line of code.

The List

1. Patchy implementations

Mapstraction abstracts the lowest common denominator set of functionality for its supported APIs. I've been working primarily with Multimap and have discovered that, for this API at least, some API classes are missing methods or have non-working implementations.

In the Multimap case this is just a few methods here and there but the thing I found annoying was that, rather than the method just being empty or throwing a "not implemented" exception, the method was populated with the code for one of the other APIs.

2. Incomplete events

The only events catered for by Mapstraction are "move end" and "click" which is severely limiting considering the vast array of events available through the native APIs. Events like "zoom", "open bubble", "change map type" etc aren't there.

Arguably, abstracting events is probably the most difficult part of the process as you have to take into account differences in when similar events fire, orders that they fire and event arguments that are passed back to the handler.

The event implementation for the two events also doesn't cater for overriding the scope in which the handler function is to be executed via the call method which is essential if you're working with methods of JavaScript objects.

3. No namespacing or prefixing

The Mapstraction code is not namespaced, scoped or prefixed in any way so is dangerous when used with a lot of JavaScript code from different sources as you'll likely end up with name clashes and global variables being overwritten.

4. No standards enforced on the source code

There appear to be no coding standards enforced on the source. It's full of undelared variables, dodgy constructs and some bits that just aren't formatted well, making the code difficult to follow.

The likes of Yahoo! run all their code through JSLint before it goes anywhere near deployment and with a library of this type I think at least a loose Linting is a must.

To sum up

If your integration is complex and requires a lot of event handling and dynamic manipulation of the map artifacts then Mapstraction isn't quite there yet but for most other things it's worth filling in any holes yourself for that freedom of API.

What Hi-Fi disappoint on Lossless

In the Sound Advice section of the Jan 2008 issue of What Hi-Fi a reader asks what the best portable player and file format is for maximising digital audio quality. The response is essentially buy an iPod and use Apple Lossless. Whilst I agree the iPod's audio hardware is very good, I don't think its virtually proprietary encoding algorithm is something What Hi-Fi should be encouraging people to use.

They later go on to say that you could buy a device from Creative and use "one of the other lossless formats" but they don't give any examples of other formats or mention that the only lossless formats the current Creative products support are WMA (Microsoft Lossless) and AAC (Apple Lossless).

All in all I'm disappointed that a magazine that professes to be unbiased and impervious to the corporates is so casual about recommending proprietary formats which facilitate consumer lock-in. In my opinion they should be promoting the open source formats and marking the products they review down for only supporting propretary technologies. Decreasing consumer choice is, after all, a negative factor and the corporates shouldn't be allowed to get away with it.

On the plus side, from 31st Dec, 7 Digital will be offering Radiohead's In Rainbows in FLAC format click here for more.

Reference types in prototype declaration - JavaScript gotcha

I've recently started doing some heavy duty JavaScript, including messing around with constructors, prototypes, lamdas, closures etc. I started off creating a few classes by creating a constructor function and then defining its prototype using object-literal notation as it means your code looks quite like class declarations in other OO languages.

Here is a simple example without any methods, just with two member variables:

function MyClass(){}
MyClass.prototype = {
 iNum: 0,
 sStr: 'Derek'
};

var oA = new MyClass();
var oB = new MyClass();

// oA: iNum -> 0, sStr -> Derek
// oB: iNum -> 0, sStr -> Derek

oA.iNum++;
oA.sStr += ' Fowler';

// oA: iNum -> 1, sStr -> Derek Fowler
// oB: iNum -> 0, sStr -> Derek

All seems well, however, upon adding some reference types to the prototype things get a bit strange:

//...

MyClass.prototype = {
 iNum: 0,
 sStr: 'Derek',
 aAry: []
};

//...

// oA: aAry.length -> 0
// oB: aAry.length -> 0

oA.aAry.push('test');

// oA: aAry.length -> 1
// oB: aAry.length -> 1

Adding an element to aAry of oA has added it to oB's aAry too. "Odd", I thought, so I did a little more investigation:

// MyClass.prototype.aAry.length -> 1

The array property of the instances is pointing back to the property of the prototype. In other OO languages all member variables within the class declaration are copied into the instances, it is only static variables and method implementations that are shared between them. These JavaScript variables seem to be neither member nor static, they are member if value types and static if reference types. Next I tried looping though the properties and testing hasOwnProperty:

for(var sProp in oA){
 // oA.hasOwnProperty(sProp)
}

Before the assignments all the properties return false, that they are not member properties but reside within the prototype. Following the assignment however iNum and sStr return member and only aAry still claims to be prototype.

This behaviour isn't a bug in an implementation either, it is consistant in all the browsers but after having a quick look in the ECMA-262 doc i'm still none the wiser about why this is the case. Anyone who can shed light on this please comment below.

The solution

The solution to this is to create all member variables using the this keyword in the class constructor thus:

function MyClass(){
 this.aAry = [];
}

This ensures that the variable is created upon the new instance and you don't get any sharing problems.

ALA Web Design Survey 2007 Results

The results from this year's A List Apart Survey of Web Design Professionals are in.

The findings are in an 82 page PDF which makes some interesting reading. You can also get an anonymised version of the 33,000 raw responses if you want to do some number crunching of your own.

Links

• ALA Web Design Survey 2007
• ALA Web Design Survey 2007 Results

Winamp 5.5 - 10th Anniversary Edition

That's right, 10th Anniversary, the first version of Winamp came out in 1997. Interestingly, on the 6th of August that year, Microsoft bought a $150 million share of the "financially troubled" Apple.

Since I bought my iPod (2004) I've pretty much exclusively used iTunes however, my foray into the world of FLAC has meant that it's not really meeting my requirements any more and I've been looking for a media library application with better format support.

I'll be posting a feature comparison and which one I've decided to go with in the coming weeks but until then I'll just say that I'm impressed with Winamp 5.5 so far. I'm only using the free version however it seems to have come a long way since the last time I used it. Features I'm particularly enjoying are:

• Album art
• Advanced SQL query style smart playlist generation
• iPod support
• Ripping to FLAC

Links

• Winamp

Ripping to FLAC with Exact Audio Copy

In a previous post I talked about the convenience of having your CD collection archived to a hard disk. I weighed up the options for a archiving format and decided FLAC met my needs the best.

Anyone who has done and serious ripping on a Windows PC in the past will likely know that there are two big players; CDex and Exact Audio Copy. While EAC is not open source it seems to me to be the more complete solution and in a like for like comparison ripped far faster than CDex without any loss of quality. Mac or Unix users can check out the download page on the FLAC site for the ripping options availabe to them.

Getting it set up

After downloading and installing EAC you'll be presented with the very handy setup wizard which does a lot of the hard work for you. Unfortunately in my case the drive setup parts of the wizard didn't work first time which was down to EAC defaulting to using a third party ASAPI drive interface which i didn't have installed. This is easily fixed after the setup finished by going to:
EAC > EAC Options... > Interface(tab)
and selecting "Native Win32 interface for Win NT/2000/XP". Re-run the wizard again from the EAC menu to configure your drives.

Once you're finished with the wizard it's best to run through the settings it's chosen anyway as in some cases they aren't optimal. Main things to check, from the EAC menu:

EAC Options:

• Extraction tab
  • Extraction and compression priority
    Setting this to "High" will ensure that EAC is prioritised above other applications when its ripping.

Drive Options:

• Extraction Method tab
  • Mode
    Ideally you want "Secure".
  • Examine C2 Feature...
    You can use this tool along with a suitably scratched CD to determine whether your drive supports C2. This is worth doing as it will increase the speed of your rips.
• Drive tab
  • Drive read command
    Hit the "Autodetect read command now" button as the wizard doesn't seem to set this.
• Offset/Speed tab
  • Allow speed reduction during extraction
    Ideally you want this checked but some drives don't speed up again once they've slowed down.
  • Use AccurateRip with this drive
    You want this checked as it will look up the checksums of your rips against a database of other people's thus ensuring they're accurate.
• Gap Detection tab
  • Gap/Index retrieval method
    It's worth putting a CD in and running a Detect Gaps once for each one of these options to see which is quickest.
  • Detection accuracy
    Set this to "Secure".

Compression Options:

The configuration wizard should have configured your FLAC settings for you so long as you picked the right option. You can check this in "Compression Options...". If it hasn't then run the wizard again and chose the FLAC option when prompted rather than trying to set the command line and all its parameters yourself.

freedb/Database Options:

• freedb tab
  • Your e-mail address
    Enter your e-mail address to use freedb.
  • Get active freedb server list
    Hit this to get the list of freedb servers.

Ripping a CD

1. Put a CD in and select the right drive from the drop-down list, the list of track should appear.
2. Hit F4 (Action > Detect Gaps) to run the gap detection.
3. Hit Alt-G (Database > Get CD Information From > Remote freedb) to get the album and track info.
4. Check the album info is right and if not update it.
5. Hit Ctrl-A (Edit > Select All) and the Shift-F5 (Action > Copy Selected Tracks > Compressed...) to begin ripping.

After this finishes you get a status log that gives you a quality percentage, AccurateRip confidence and and errors for each track.

Track quality indicates what percentage of the track was ripped first time with no problems. If everything is set up properly and you have a scratch free CD will normally be 99.9% or 100%.

AccurateRip confidence is the number of people in the AccurateRip database who have submitted the same checksum for a particular track as you. The higher the confidence the better however, a low confidence doesn't necessarily mean it is a bad rip, especially if you're ripping a lesser known CD.

Finally

Fire up Winamp, have a listen and then kick yourself for ever thinking MP3s sounded good!

Amazon MP3 downloads

Today's top two MP3 artists on Amazon MP3 are Richard Wagner and Pink Floyd. I find this odd considering that the audiences for these two artists i.e. the classical lot and the prog lot are probably the most demanding when it comes to audio quality.

After it went public beta last week I have to admit I'm very impressed with Amazon's offering; comparing its service to a few others:

	iTunes		HMV	Walmart		Amazon
	Standard	Plus		WMA	MP3
Format	AAC	AAC	WMA	WMA	MP3	MP3
Quality	128kbps	256kbps	?	128kbps	256kbps	256kbps
DRM	Yes	No	Yes	Yes	No	No
Price Feist - The Reminder	$9.99	$12.99	$16.22	$9.44	$9.22	$8.99

I'm not sure how many people consider things like quality and DRM when downloading music but one thing they will consider is price and Amazon is the clear leader here. Especially seeing as the album I chose for the comparison is one of the more expensive ones; you can download the whole of Pink Floyd's Wish You Were Here for $4.45, that's £2.20!

The fact that Amazon offer DRM-free MP3s means that they will play on pretty much anything. In addition to computers and portable music players, these days you'd be hard pushed to find a CD or DVD player that doesn't play MP3s. The AAC and WMA offerings of the competitors very much limit your choice of player; for example AAC work on iPods, WMA work on Creative Zens but not vice versa. MP3s, however, will work on both.

Amazon already has a massive share of the music retail market so its existing customers are more likely to download from them than go with one of the alternatives. Although they don't offer this yet, something that would seal up the Christmas market would be a "Buy an MP3 player preloaded with albums of your choice" service.

It all seems to stack up in Amazon's favour, I'd wager iTunes are going to see their market share slipping away in the coming months.

FLAC on your iPod with Rockbox

The list of hardware with native FLAC support on the FLAC website includes quite a few home systems; Slim Devices' Squeezebox and Transporter, the Sonos Music System and wireless media players from the likes of Netgear, Olive and Helios. The list of portable players with native support is less impressive however, Cowon and Rio being the only names I recognise.

Thankfully the very nice people responsible for the Rockbox firmware had the foresight to include a FLAC codec meaning if you own an iPod or one of the other supported players listed below then all is not lost.

• Apple: 1st through 5.5th generation iPod, iPod Mini and 1st generation iPod Nano (not the Shuffle, 2nd/3rd gen Nano, Classic or Touch)
• Archos: Jukebox 5000, 6000, Studio, Recorder, FM Recorder, Recorder V2 and Ondio
• Cowon: iAudio X5, X5V, X5L, M5 and M5L
• iriver: H100, H300 and H10 series
• SanDisk: Sansa c200, e200 and e200R series
• Toshiba: Gigabeat X and F series (not the S series)

I'm normally skeptical of any such warranty voiding activities however, as my iPod is third generation its warranty days are long gone, I thought I'd give it a go. The firmware itself runs alongside the Apple one in a very nifty dual boot setup and the installation couldn't really be simpler. All you do is download one of the builds, copy it to the root of your iPod's hard disk, run a flash utility and it's done.

There are a lot of benefits to Rockbox over the native firmware including folder browsing, playlist editing, skinning and one the audiophiles will love, a proper parametric EQ so you can even out your headphones' response. There does seem to be one disadvantage too in that battery life seems somewhat reduced, possibly due to the increased disk access required for FLAC playback. This is a small price to pay for an impeccable performance from the full quality tracks going through the iPod DAC though.

Links

• FLAC
• Rockbox

.NET Performance Counter Problems

I've recently been doing some work with performance counters in .NET and discovered the support for them in the framework is a bit nasty.

One example is that the only way to add counters is through the PerformanceCounterCategory.Create method so you can't append a new counter to an existing category. You have to copy all the counters from the old category, add you new counter, delete the old category and then recreate the category with the new list of counters.

Another example is that in order to use any of the fraction based counters like averages you have to add two separate counters, one for the numerator and one for the denominator.

All very long winded anyway so I decided that I'd wrap up the creation of the counters and categories along with a few other bits in a helper class. That was the plan but it fell at the first hurdle - trying to create categories.

The symptom

This, seemingly innocuous bit of code...

if(!PerformanceCounterCategory.Exists(categoryName))
{
 PerformanceCounterCategory.Create(categoryName, categoryName, new CounterCreationDataCollection() );
}

if(!PerformanceCounterCategory.CounterExists(counterName, categoryName))
{
 //add a counter
}

...was yielding the following error on line 6:

System.InvalidOperationException: Category does not exist.
   at System.Diagnostics.PerformanceCounterLib.CounterExists(String machine, Str
ing category, String counter)
   at System.Diagnostics.PerformanceCounterCategory.CounterExists(String counter
Name, String categoryName, String machineName)
   at System.Diagnostics.PerformanceCounterCategory.CounterExists(String counter
Name, String categoryName)

i.e. three lines after the statement creating a category it says the category doesn't exist. Odd, I thought, so I knocked together a quick Snippet Compiler script:

string categoryName = "foo";
string counterName = "bar";
  
if(PerformanceCounterCategory.Exists(categoryName))
 PerformanceCounterCategory.Delete(categoryName);
  
WL("Category " + categoryName + " exists? " + PerformanceCounterCategory.Exists(categoryName));
  
PerformanceCounterCategory.Create(categoryName, categoryName, new CounterCreationDataCollection() );
  
WL("Category " + categoryName + " exists? " + PerformanceCounterCategory.Exists(categoryName));
      
try
{
 WL("Counter foobar exists? " + PerformanceCounterCategory.CounterExists(counterName, categoryName));
}
catch(Exception ex)
{
 WL(ex.ToString());
}
  
RL();

Further oddness arose from this because the call to PerformanceCounterCategory.Exists after the Create actually gives the correct response, it is only the CounterExists method that fails. I immediately suspected some sort of caching issue.

The cause

After having a poke around with Lutz Roeder's .NET Reflector I discovered that all the Performance Counter classes make use of an internal class called PerformanceCounterLib which has a few hashtables it uses to cache information about the categories and their counters.

The hashtable concerned here was the CategoryTable which, on adding a category for he first time, does not update properly. When the CounterExists call runs this line:

if(this.CategoryTable.ContainsKey(category))

it fails throwing the error however the Exists call has this line:

return (PerformanceCounterLib.IsCustomCategory(machineName, categoryName) 
   || PerformanceCounterLib.CategoryExists(machineName, categoryName));

the right part of this calls the same CategoryTable.ContainsKey however the IsCustomCategory on the left accesses the registry directly and returns the correct answer - true.

Why the CounterExists doesn't call this method itself and opts instead to provide its own implementation i've no idea.

The solution

Luckily the PerformanceCounter.CloseSharedResources() method flushes all these internal caches so the calls all return the same answer. Adding a call to this straight after my PerformanceCounterCategory.Create solved the problem.

Archiving your CD collection

This post could probably be considered to be the second part of my very first post on this blog entitled Freeing your digital media in which I talked about the DLNA standards and how they allowed you to store all your media on a NAS device and stream it around your house over your network.

I'd been considering this more seriously and realised that a large proportion of my MP3 collection were low bitrate poor quality rips which just sound awful played though a half decent hi-fi.

Storage space is only getting cheaper and today you can pick up a 500GB external hard disk, enough for 700 uncompressed albums, for less than £80; the Western Digital My Book series proving to be a popular choice. There really is no reason why, with this much space, we should be sticking to lossy compression formats for our music archiving. So, with that in mind, what are the options?

The main contenders

WAV

Microsoft's uncompressed audio format

AIFF

Apple's uncompressed audio format

WMA Lossless

Microsoft's lossless audio compression format

Apple Lossless

Apple's lossless audio compression format

FLAC

Open source lossless audio compression format - now part of the Xiph.org Foundation, originally developed by Josh Coalson

Monkey's Audio

A lossless audio compression format developed by Matt Ashland

Shorten

An old open source lossless audio compression format developed by Tony Robinson at SoftSound

Hydrogen Audio have prepared a good comparison table of lossless formats. Uncompressed 44.1kHz 16bit audio uses up about 10MB of space per minute. The lossless compression formats listed above all reduce file sizes to about 6MB per minute. Not bad but compared to the 1 - 2MB per minute we're used to with lossy formats this still seems like a lot. My justification for this space usage is that I want the convenience of being able to carry 700 albums around with me and I've paid for the CDs so i might as well be listening to them in full CD quality.

My criteria for a format were; open source, good compression and good hardware and software support. This already removes all the Microsoft and Apple options and Monkey's Audio. Shorten is old and has poor support so the natural choice is FLAC which, being part of the Xiph.org Foundation, has a large developer base behind it and support in all the major software and hardware music players albeit via new firmware in some cases. Not to mention that it's now packaged with arguably the best CD ripper, Exact Audio Copy.

A quick download, set up and a few rips later and I'm rather astounded by the results. To my ears the FLAC files actually sound better than playing the original CD through the same system, delivering a far more punchy and detailed sound. I have to admit I wasn't expecting this and I'm assuming it's down to my CD-ROM reading the audio data poorly when playing the CD directly.

Links

• Audio compression - Wikipedia

Mobile madness

I've recently been going through the yearly trauma of picking a new phone as my free upgrade. It's the same every time - there is never one phone that meets all my criteria so I have to go for the best compromise. The phone I'm upgrading is a Nokia 6680 which is a rather large Symbian smartphone, lacking in both the processor speed and memory stakes. The criteria for my new phone are therefore:

• Features - preferably a smartphone with a camera (40%)
• Usability - a decent size keypad and quick processor (30%)
• Size - not a brick but not very thin either (20%)
• Design - least important but something that looks reasonable (10%)

I've only ever had Nokia phones and have stuck with them mainly because they were a lot more usable than other brands. Nokia's current offerings were leaving me a bit cold however so I've been thinking "surely the other brands must have caught up" and indeed Sony Ericsson's sales are topping Nokia's in the UK at the moment. Anyway I thought I'd give another brand a try so I went for a Samsung U600 as I like the look of their sliders and although it's not a smartphone it is from their new "Ultra Edition 2" line so I thought it would meet my needs.

I'm currently awaiting the Jiffy bag from Orange to send it back in so needless to say it fell at the first hurdle. A hopelessly inadequate phonebook, annoying predictive text set-up requiring constant swapping between keypad and navigation key, and some very questionable calling and hanging up behaviour were my main grievances.

So now I'm back to square one and thinking I'm either going to get a Nokia or another brand only if it's running Symbian so I can be assured of a certain amount of base functionality. So the next two candidates were the Nokia 6300 or the Sony Ericsson W950i - the Sony is missing the all important camera and the Nokia isn't running Symbian so not clear cut by any means. I may have finally found the answer with the Nokia 6120 which is a smartphone, has a camera and is a centimetre narrower and half a centimetre thinner than the 6680. Only problem with this one is that it's not currently available on Orange so I've got to wait for it - Doh!

Links

• Nokia
• Sony Ericsson
• Samsung

500 Geeks + 1.21 Jigawatts = ?

Well, i'm back. Thanks to Yahoo! and the BBC for a great weekend. It didn't get off to the best of starts what with the lightning and broken WiFi and all but everyone made the best of it.

A total of 73 hacks were presented on the Sunday evening however ours wasn't finished in time which was a shame because no-one else had made anything similar. If 500 geeks went and were in teams of five then there should have been 100 hacks so i'm guessing we weren't the only people who didn't finish.

Hack-tastic, looking forward to the next one!

• Hack Day on Yahoo! Developer
• Hack Day on BBC Backstage
• Hack Day on Wired

Hack Day UK 2007

Thought a quick post was in order as I've just received the e-mail confirming my place at this year's Hack Day UK.

I'll be there along with the fellows from my blogroll - current and former colleges - and we'll likely be attempting our own hack as well as pimping our skills to the highest bidder!

• Hack Day

ALA Web Design Survey 2007

Just a quick post to point you all in the direction of A List Apart's survey of Web Design Professionals. It's been up for a while now and I've only just remembered to fill it in myself. I look forward to the results and hope at least some of them are plotted on a nice graph.

• A List Apart Web Design Survey