High Tech Sorcery » Uncategorized

various ways of escaping content in ruby

specialj — Fri, 05 Aug 2011 11:08:39 +0000

It’s difficult to keep these all straight:

storing money in decimal fields in MySQL

specialj — Wed, 15 Jun 2011 08:51:06 +0000

I haven’t found a lot of advice about what precision values to use for storing money in decimal fields. Here’s what I calculated. The scale is going to be 2 for US currency which requires 1 byte of storage.

precision 4, scale 2 = 2 bytes of storage, 99.99 to -99.99
precision 6, scale 2 = 3 bytes of storage, 9999.99 to -9999.99
precision 8, scale 2 = 4 bytes of storage, 999999.99 to -999999.99 (I’ve tended to suggest this as a starting point)
precision 11, scale 2 = 5 bytes
precision 13, scale 2 = 6 bytes
precision 15, scale 2 = 7 bytes
precision 17, scale 2 = 8 bytes

Encoding webm with ffmpeg

specialj — Fri, 11 Mar 2011 21:46:07 +0000

It was pretty easy. At it’s most basic:

ffpeg -i infile -f webm outfile.webm

Some resources to get fancier:

Alternatives to the ASUS M4A785TD-V EVO

specialj — Tue, 11 Jan 2011 21:50:56 +0000

There seems to be a small market for consumer motherboards with ECC. I had planned on purchasing a new system with the ASUS M4A785TD-V EVO motherboard which got excellent reviews, was reasonably priced, and supported ECC DDR3 memory. As this motherboard has been discontinued I took some time to find its successor. I’m not sure the M4A78T-E counts as a successor but it is a reasonable alternative. Finding it was somewhat difficult as ECC is not a feature many places seem to list (including newegg). The main difference between the M4A785TD-V EVO and the M4A78T-E is the chipset combo: AMD 785G/SB710/RADEON 4200 on the former, AMD 790GX/SB750/RADEON 3300 on the latter. For an additional $50 the ASUS M4A89GTD PRO/USB3 brings a bump to AMD 890GX/SB850/RADEON 4290 as well as USB 3 and 6Gbps SATA. That makes it a little more future-proof but as to whether that’s worth a 50% price jump I’m skeptical.

Getting more entropy for virtual servers

specialj — Wed, 05 May 2010 03:54:38 +0000

It is not uncommon for people to have performance problems with the their virtual servers and chalk it up to virtualization as the problem instead of insufficient entropy. Running a mail server or SSL web server are particularly vulnerable to virtual servers without much entropy. I have noticed that my virtual servers have had a lot less entropy in the past 6 months or so. I decided to revisit what simple and effective solutions exist to solve this problem.

I decided I would do a search for debian and ubuntu packages that could be used without much modification or configuration.

reseed – this pulls random data from random.org. However, it does this over HTTP so this package should be avoided unless one wanted to rewrite it to use HTTPS.
randomsound – this pulls random bits from a soundcard. This is good for a host system with a soundcard but not useful for a virtual server.
rng-tools – this is supposed to pull from a hardware true random number generator however some people have used /dev/urandom as the source. This is probably not a good solution.
haveged – this basically uses interrupt timing to generate random numbers. Not a lot has been written about haveged but it seems like the best easily available solution. It would be nice to review the quality of the random numbers though.

Other options:

KVM supposedly has a virtio-rng device which can pull entropy from the host into the guest. This would still potentially create a need for entropy creation on the host but could be a simpler setup for those using KVM.
It would be pretty easy to write a script to download random bits from random.org using HTTPS.

Chromium Extensions

specialj — Fri, 23 Apr 2010 01:31:11 +0000

I’ve been playing with the beta builds of chromium for a while. There are not nearly as many useful extensions are there are for firefox but these have helped:

Copy Without Formatting
FlashBlock (there’s also this FlashBlock, not sure what the practical difference is)

MySQL Workbench 5.2.16 Beta 6 has been released

specialj — Sat, 20 Feb 2010 08:31:14 +0000

MySQL Workbench 5.2.16 Beta 6 Available

Open Source Search Engines with Web Crawling and HTML Indexing

specialj — Wed, 20 Jan 2010 02:48:30 +0000

The term search engine is particularly vague. It can mean an online search engine, or it can mean software that provides something similar to the online search engines, or it can mean software that does fulltext indexing and querying. I specifically wanted to find a tool that could be used to create a niche search engine without having to write the whole thing myself as a ruby on rails app. Here’s what I found:

mnoGoSearch – seems very actively maintained, packages present in Debian and Ubuntu, written in c
DataparkSearch – seems fairly actively maintained, apparently a branch of mnoGoSearch, written in c
Nutch – seems fairly actively maintained,written in java, built on top of Lucene

And that’s really it. There is a product called ASPseek but it has long since been abandoned. There is also ht://Dig but it has not been updated in years and is not really in the same league as the above. So, at least for anyone trying to research this area there are not a whole lot options to try.

Resources:

Alternative Search Engines
Alternative Search Engines
A comparison between public-domain search engines – pdf, html (via google)

Alternative Search EnginesAlternative Search Engines

Another year, another blog

specialj — Tue, 19 Jan 2010 20:31:54 +0000

I believe this is my 6th blog. So far I have never taken the time to migrate articles from one to another and I am continuing that tradition. Not so good for the internet perhaps but better for me to not have to take the time to get a migration right. I may go back and report some of my older content as appropriate though. I decided to use wordpress this time because I’m supporting some other wordpress users. I haven’t been the biggest wordpress fan in the past but I’m willing to give it another try.