Alan's RamblingsWeb

Scala snippet of the day

Fri, 17 Feb 2012 14:04:00 GMT

The following is useful for benchmarking code from inside the REPL:

def timed(op: => Unit) = {
  val start = System.nanoTime
  op
  (System.nanoTime - start) / 1e9
}

Then you can use it like this:

scala> timed { Thread.sleep(5000) }
res0: Double = 5.010083526

That's syntactic sugar for an anonymous function definition and a call of timed. If a function takes only a single parameter you can pass it inside { }, so if we wrote that out longhand it would be:

scala> def fn = Thread.sleep(5000)
fn: Unit

scala> timed(fn)
res0: Double = 5.010088248

The other neat bit is the use of Scala's pass-by-name mechanism to pass the op parameter. That's the funny-looking op: => Unit argument list to timed. Normally Scala uses by-value parameters, i.e. the line timed(fn) would result in the evaluation of fn, and then passing the returned value (in this case, nothing) into timed. However by using pass-by-name, the evaluation of fn takes place inside timed, and by wrapping it inside timing instrumentation we can time how long op takes to execute.

Stupid BT router...

Wed, 23 Nov 2011 14:12:00 GMT

I have the misfortune to own a BT Business 2Wire router, and bleaklow.com sits behind that. A while back it threw a fit and reconfigured itself and when I beat it into submission I didn't notice that it had also lost the port mappings for bleaklow.com. As a result I've been off-air for quite some time. Bloody BT...

mod-rewrite equivalent for Tomcat

Wed, 02 Jun 2010 17:15:00 GMT

I've migrated and merged my old blogs.sun.com and bleaklow.com blogs into this new one, using Pebble. As a result, there are a number of links out there on the interwebs to bleaklow.com that are now broken, as everything has moved around - google's webmaster tools gives me a comprehensive list. If I was hosting this blog using Apache, the standard solution would be to use the most excellent mod-rewrite Apache module to redirect the broken links to somewhere appropriate. However Pebble is a J2EE application and uses Tomcat instead of Apache. I've been looking for an equivalent to mod-rewrite for a while and never managed to find anything. Whilst looking for something else entirely (always the way) I found Url Rewrite Filter. This is functional equivalent to mod-rewrite for J2EE servers, and offers most of the same features as mod-rewrite. I'm using it and it seems to do the job just fine, and the beta even has a mod-rewrite style configuration option, if you need a security blanket :-)

Simple parser for MovableType exports

Sun, 23 May 2010 10:03:00 GMT

As part of moving my blog over to I needed to be able to transfer the content from my old MovableType blog and my blogs.sun.com blog, which runs on Roller. Both MT and Roller can export in MovableType export format and Pebble has a MT importer, so it looked relatively straightforward. However when I looked at the content I was importing it was clear I'd need to munge it on its way into Pebble. The Pebble MT importer is one-pass and loads the entries into Pebble as it reads them, whereas I wanted to read them in, munge them and only then load them into Pebble, so I wrote a simple parser to read in the MT export. It's not a thing of great beauty but it got the job done. I thought it might be useful for other people who want to read MovableType exports from Java, so I've put a copy of it here.

Image thumbnailer for Pebble

Sun, 23 May 2010 08:54:00 GMT

This blog uses the Pebble package for delivering content. Pebble isn't a particularly common blogging package but it fits my purely personal and subjective requirements:

Not written in PHP (blegh)
Open source, and something in Java would be nice
Doesn't use a database and uses flat files that I can manage manually if I need to
Good RSS, search, tag and category management
Can be restyled easily

The old incarnation of this blog used MovableType but that doesn't really tick the Open Source box any more. blogs.sun.com uses Roller but that requires a database back-end. All these constraints combined to give a pretty short list of candidates, i.e. Pebble.

One thing that Pebble lacks is an image thumbnailer. I'm not bothered about glossy JavaScript solutions such as Lightbox, and I'm quite happy to type in HTML table definitions. All I wanted was something to save me the tedium of manually generating the thumbnails and typing in the HTML to display them and link to the full-size image in a popup window. MovableType has this feature but Pebble doesn't so I sat down one evening and knocked together an equivalent as a Pebble plugin, using the standard Java2D APIs to do the image manipulation. All the thumbnails on this site are done with it, and I've submitted this as a patch to Pebble so hopefully it will make it into a future release.

Update

The patch has been accepted and should be appearing in a future version of Pebble.