Watch points for variables in Ruby - Object#freeze

Almost every programmer knows about watch points. Especially the ones doing native development with C/C++. Watch points were really helpful to me when I was working with C/C++. They were, sort of, my go to weapons whenever I wanted to understand how some third party code worked. It was something that I dearly missed when I started with Ruby. I am fairly new to Ruby and I have never used the ruby-debug (or ruby-debug19) gem, because until today simple print statements were sufficient most of the times.

Today I was at a loss as I was unable to figure out where a particular hash variable was getting two new key-value pairs in it. It was an instance variable with just an attr_reader defined. So obviously a reference to the instance variable was being passed around to the place where it was being modified. So my initial idea of writing a custom write accessor method was probably not going to work (did not try it). That is when I came across this http://ruby-doc.org/docs/ProgrammingRuby/html/trouble.html#S3. The last bullet point in that section has the answer.

You just freeze the object/variable that you want to watch by calling the "freeze" instance method on that object and anyone modifying that object after it's frozen will cause an exception to be raised giving you the precise location of where that modification is happening. This isn't probably as elegant as running a debugger and setting a watch point but it gets the work done nevertheless. RTFM after all..!! This tool is definitely going into my belt. :)

Backup contacts from Nokia phone to a excel spreadsheet -- Convert VCF to CSV with nodejs.!

Yesterday my uncle asked me to take a backup of his cellphone contacts. He has a Nokia 3600 Slide phone. Now this phone is a piece of work.. ! It doesn't provide a way to copy/move contacts to the external memory card. I found a couple of file manager applications in .jar and .jad formats and tried to see if they show me the phone's memory (not the external memory card, but the memory embedded in the phone) as that is where the contacts are stored. But no luck. Later when I found one such application, whose description said it gives you access to contacts, it was a .sis file and phone simply said "File format not supported"... !! . It's a S40 phone and hence cannot install applications from .sis files and most of the cool and usable stuff seem to be available in .sis format only. :(

A little searching led me to Nokia Europe support website page for "Backing up your phone" and the preferred method for backing up contacts was copying to a computer via bluetooth (mentioned as the simpler solution) and backup via PC Suite (mentioned as the harder way). Sadly the simpler way was not possible for me as my current laptop (Lenovo G550) is bluetooth challenged (a.k.a no bluetooth module) and I did not have the CD that comes with the phone to install the PC Suite (I wouldn't have installed it even if I had the CD.. !!)

Some more searching led to me a few applications (free and paid, .sis and .jar/.jad formats) which would "sync" your phone to a "remote location" via GPRS and make it available to us globally and also (here comes the best part) via "Social Networking Websites".... (Geez... as if we love spam calls and SMS and we are short of them..!!).

Having found nothing really useful I started fiddling with the phone settings to see if I can find something there. Luckily there was the Backup option there. The default backup tool available in the phone can apparently dump your phone's current state --- including contacts, calender, settings, applications, etc.. etc.., all into a backup file (a .NBF file which I presume stands for Nokia Backup File/Format). Well thankfully this file is placed in the external memory card, in a folder named Backups. Then I connected my phone to my laptop and chose it to be used as an external storage device. Copied the .NBF to my computer. And I was happy that I could do it without any additional installation.

Sadly the happiness did not last long. I tried to open the NBF file in a few text editors (hoping to see a huge list of contacts) but was instead presented some gibberish.. Damn it... it's a binary file.. ! And I could not find any reader/converter for this file format on the internet. But thanks to the linux "file" utility, I got to know that NBF is just a zip archive. Fantastic... !! I unzipped it and found all my contacts in a folder at a depth of 4 (i.e. a folder in a folder.. 4 times). Again I did not see a huge list of contacts. I saw a huge list of VCF files, one each for every entry in my contacts. And this is how each file looked : (in case you are wondering why this file per entry is a problem)

BEGIN:VCARD

VERSION:2.1

N;CHARSET=UTF-8;ENCODING=8BIT:

TEL;PREF;WORK;VOICE;ENCODING=8BIT:

END:VCARD

Well clearly this is not really a usable form.. !!

Now, I thought I would just import all these VCF files into my contacts in Outlook and then export it as a CSV. That would be a pain in two ways -- First I need to setup my Outlook if it is not already setup, which was the case with me(a small pain). Secondly if Outlook is already setup then the two sets of contacts will be merged. Not something that my uncle wants. So the next idea was to convert all these VCF files into one CSV.

Then the hunt started for VCF to CSV converter. I found a couple of online ones, but was apprehensive to upload the files to a remote server. I also had the option of downloading those server side scripts and run them in a webserver locally or with a PHP engine from the command line. I did not have PHP installed and did not think it was worth the effort as I wasn't sure how well those scripts worked. Finally I found this python script - http://code.google.com/p/vcf-to-csv-converter/ . Happily I fired up my Linux VM and ran the script with nearly 1000 VCF files got from the phone. Bang.. !!! The script erred out with an exception while processing some 332nd file. :(

At this point it appeared to me that the easiest way out was to write a simple importer myself. I was in no mood to write a C/C++ program and do all that string manipulation with raw character buffers and pointers. And the only scripting language that I know well (well enough to write something useful on my own from scratch) was Javascript... !! So how do I process these VCF files with Javascript?

Enter, Nodejs. I had been fiddling around with node for some time now but had not done anything useful with it. So I fired up vim and started to write the importer script and in about 30 mins (much less than the time spent on the internet searching for an existing tool... !) I had the contacts list in a CSV..!! Wohooo... And here is the script which did the job : https://gist.github.com/738325

The script is very crude, to the extent that I have hardcoded the path of the output file and it's very likely not efficient either. Also note that this script just extracts Name and Phone numbers and no other details. It is a not a generic VCF parser ( I don't even know the VCF spec. I just looked at a couple of VCF fies and figured the format of lines for name and numbers). If anyone needs it, they are free to use it. No guarantees though.. !! :)

It was a fun playing with JS, specially NodeJS. :)