Category Archives: Programming

Go, the language for emulators

So, I hear you like emulators. It turns out that Go is a great language for writing retro-computing emulators. Here are the ones that I have tried so far:

trs80 by Lawrence Kesteloot

I really liked this one because it avoids the quagmire of OpenGL or SDL dependencies and runs in your web browser. I had a little trouble getting it going so if you run into problems remember to execute the trs80 command in the source directory itself. If you’ve used go get github.com/lkesteloot/trs80 then it will be $GOPATH/src/github.com/lkesteloot/trs80.

trs80

GoSpeccy by Andrea Fazzi

GoSpeccy was the first emulator written in Go that I am aware of, Andrea has been quietly hacking away well before Go hit 1.0. I’ve even been able to get GoSpeccy running on a Raspberry Pi, X forwarded back to my laptop. Here is a screenshot running the Fire104b intro by Andrew Gerrand

GoSpeccy on a Raspberry Pi

Fergulator by Scott Ferguson

Like GoSpeccy, Fergulator shows the power of Go as a language for writing complex emulators, and the power of go get to handle packages with complex dependencies. Here are the two commands that took me from having no NES emulation on my laptop, to full NES emulation on my laptop. 

lucky(~) sudo apt-get install libsdl1.2-dev libsdl-gfx1.2-dev libsdl-image1.2-dev libglew1.6-dev libxrandr-dev
lucky(~) % go get github.com/scottferg/Fergulator
Fergulator

sms by Andrea Fazzi

What’s this? Another emulator for Andrea Fazzi ? Why, yes it is. Again, super easy to install with go get -v github.com/remogatto/sms. Sadly there are no sample roms included with sms due to copyright restrictions, so no screenshot. Update: Andrea has included an open source ROM so we can have a screenshot.

sms

Update: Several Gophers from the wonderful Go+ community commented that there are still more emulators that I haven’t mentioned.

Andrei Alexandrescu on exceptions

Source: C++ and Beyond 2012: Andrei Alexandrescu – Systematic Error Handling in C++

Earlier today on the #go-nuts irc channel:

11:32 < nsf> http://channel9.msdn.com/Shows/Going+Deep/C-and-Beyond-2012-Andrei-Alexandrescu-Systematic-Error-Handling-in-C

11:32 < nsf> Andrei invents multiple return values and defer

I have a great deal of respect for Andrei. I think whenever he speaks, you should listen. In watching this video I was struck by his excellent categorisation of some of the less common arguments for errors over exceptions:

  • The exceptional path is slow (00:10:23). Facebook was using exceptions to signal parsing errors, which turned out to be too slow when dealing with loosely formatted input. Facebook found that using exceptions in this way increased the cost of parsing a file by 50x (00:10:42). No real surprise here, this is also a common pattern in the Java world and clearly the wrong way to do it. Exceptions are for the exceptional.
  • Exceptions require immediate and exclusive attention (00:11:28). To me, this is a killer argument for errors over exceptions. With exceptions, you can be in your normal control flow, or the exceptional control flow, not both. You have to deal with the exception at the point it occurs, even if that exception is truly exceptional. You cannot easily stash the first exception and do some cleanup if that may itself throw an exception.

Netgear Stora as an ARM development platform

About a week ago I posted a request for recommendations for ARM based systems that could be used for Go development. There were some great responses, including the BeagleBoard and the Guru Plug. Being impatient, and in Australia, I ended up getting a Netgear Stora which has turned out to be a great home NAS, and a capable ARM5 development system. This is the same hardware, albeit with less RAM, that ships in the ShivaPlug.

axentraserver(~/go/src) % export MAKEFLAGS=-j1
axentraserver(~/go/src) % hg identify 
546b1fc95dcc+ tip
axentraserver(~/go/src) % time ./make.bash > /dev/null
hg not installed
conflicts: 3 shift/reduce

real    10m48.889s
user    9m15.380s
sys     0m52.480s

Not too shabby, my 8g host (2.8Ghz Celeron) turns around the same build in just under 12 minutes.

Pros

  • Very good value. For less thatn $200 AUD you get a 1.2Ghz Marvel ARM5 CPU, 128mb of ram and a 1Tb Seagate 3.5″ drive (and a slot for a second drive). Online Computer have the 1Tb units for $185.
  • Very hackable. SSH is enabled out of the box, if you know the magic suffix that Netgear, and all users created via the web interface are in /etc/sudoers. The fantastic ipkg system will close the gap between the slimmed down RedHat distribution that Netgear Axentra ship and a GNU buildchain that can bootstrap Go.

Cons

  • 128mb of ram, non expandable. This actually turns out to not be a big deal. The stock install has ~75mb of RAM free while running. Turing off a few options and trimming the daemons Netgear installs can get another 10-15mb back.