GZIP/BZIP2 progress indicator

Have you ever needed to figure out how long gzip/bzip compression would take for the file and found it difficult to present it to the user ? Especially for scripts dealing with large files, this would be one of the major usability issues. Well there's a solution for the problem with the use of tool called pipe viewer. You can find more details on how to use it on it's home page, but I'll show you how I've used it to show progress for bzip2 compression of large files.

filename="file_to_bzip2"
size=`stat -L "$filename" -c "%s"`
pv -s $size "$filename" | bzip2 -c > "$filename.bz2"

Generates following output:

# output
2.75GB 0:32:47 [ 1.5MB/s] [===================>     ] 61% ETA 0:20:16

GoF design patterns reference card

Gang Of Four design patterns is probably most known developer book ever. As it is little too verbose on single patterns, people created reference cards for it. Most popular would probably be one at DZone. Recently I've tried to find one, that I can put on my Kindle and eventually found it on Google docs, so I've thought maybe I should share it.

Design of t-shirt for cryptoclass 2012

YouTube video offline mode

Recently I enrolled to AI class online course. Each week they submit dozen of explanatory and Q&A videos on youtube and reference them from AI-class site. As I mostly have time to study those videos when I'm offline I've decided to explore possibilities of getting videos to local computer for offline viewing. Purpose of this post is just to summarize steps which I did in order to achieve this goal on linux.


Get tools

First thing first, I had to equip myself with tools.

youtube-dl
After unsuccessful attempt to use clive/cclive, I decided to use youtube-dl which you can download at github project page. Although it is single purpose youtube only downloader it works and does exactly what I need. You need python interpreter to run it.
grake
Grake is utility to parse youtube links out of HTML and it's hosted at code.google.com. Grake is Perl module, but installation is straightforward, as one only has to follow instructions in INSTALL file.


Get list of videos
First step is using youtube.com to find playlist of videos. For example I've just typed 'AI class unit9 videos' to google/youtube to get this link: 'http://www.youtube.com/playlist?list=PL9163DC3C43AF7612'.


Next step is to download list using Grake and edit it

$ cd ~/Videos/Unit9
$ grake http://www.youtube.com/playlist?list=PL9163DC3C43AF7612 < Unit9.lst

Downloaded file looks like:

http://youtube.com/watch?v=videoseries
http://youtube.com/watch?v=DgH6NaJHfVQ
http://youtube.com/watch?v=9D35JSWSJAg
http://youtube.com/watch?v=9QMZQkKuYjo
http://youtube.com/watch?v=YfSBYf9h7qk
...

I've just deleted first line using vim.


Get videos
Last step is to get the videos by using youtube-dl. I've used this:

$ cat Unit9.lst | xargs youtube-dl -tA

With -tA options I told downloader to use video name as filename instead of funky hash and autoprefix it with number as it's downloaded.

Groovy Junit tests in Eclipse Indigo

I'm playing with Groovy and Grails a little bit and recently I had a problem running unit-test from recent Eclipse Indigo (3.7) with groovy-eclipse plugin installed.

Problem manifests itself with following error, when I try to righ-click and "run as" junit test-case.

junit.framework.AssertionFailedError: No tests found in path.to.your.class

I've spent some time trying to find solution and it was obvious. Think it might be helpful to keep solution in some form. I'll probably post more Groovy/Grails related stuff in the future, so why not start with this.

Let's have simple class MyClass

package sk.adino.poc.groovy.unittests

class MyClass {
  x() { return 1;}
}

and test class MyClassTest in same package

package sk.adino.poc.groovy.unittests

class MyClassTest extends GroovyTestCase {
  testX { assert x==1 }
}

Right-click in eclipse and run as JUnit test should work, but you have to:

1. have groovy-eclipse plugin installed
2. add external JAR pointing to junit-x.y.z.jar from your groovy installation lib directory - otherwise it won't even compile
3. add void as a return type of your testX function so it should look like:

package sk.adino.poc.groovy.unittests

class MyClassTest extends GroovyTestCase {
  void testX { assert x==1 }
}

Java puzzler - Letter went missing

Recently I've implemented function that takes String and populates long so that it contains character values from the back of the string. However my unit test is failing because one Letter is missing. Are you able to put it to the right place so that unit tests will not fail without debugging the code?

import static org.junit.Assert.*;
import org.junit.Test;

public class StringToolsTest {

	static final char [] data = {0xca, 0xfe, 0xeb, 0xab, 0xee};
	static final String string5 = String.valueOf(data);
	static final String string0 = "";
	static final String string1 = "a";
	static final String string9 = "987654321";
	
	@Test
	public void testFillBackwards() {
		long l = 0;
		assertEquals(0xcafeebabeeL, StringTools.fillBackwards(string5, l));
		assertEquals(0L, StringTools.fillBackwards(string0, l));
		assertEquals(0x61L, StringTools.fillBackwards(string1, l));
		assertEquals(0x3837363534333231L, StringTools.fillBackwards(string9, l));
	}
}

public class StringTools {
	public static long fillBackwards(String s, long d)
	{
		long result = 0L;
		byte[] bytes = s.getBytes();
		for (int i=0; i<Math.min(8,bytes.length); i++){
			result |= ((bytes[bytes.length-i-1] & 0xff) << (8*i));
		}
		return result;
	}
}

Solution bellow (highlight to show):

The problem is on the line 29 in "& 0xFF". I should be doing &0xFFL instead. Why ? bytes[x]&0xff is by default int (both operands are widened to int), but then << is applied, result of which is type of left operand (java spec) and this is |= to long result. Solution is to make & operator to work on long values by adding L to 0xFF.

Puzzler on snipplr.