One of the main components of URL shortener script is the base 62 encoder / decoder. Base 62 is just another way of counting, which allows us to pack more numbers into a shorter string. In base 10, we count: 1,2,3,...,9,10,11, etc. That's good, everyone knows how to count that, but the down side is, it's not very short. If we do URL shorteners like that, pretty soon, we'll have long URLs because 5 digits will only encompass 99999 links, etc. You might say, hey, 99999 links isn't too bad, but I say why end there? In base 62, we count like this: 1,2,3,...7,8,9,A,B,C,...,X,Y,Z,a,b,c,...x,y,z,10,11,12, etc. Notice by the time we got to "10", we're already at 63? Now, with the same 5 digits, we're looking at 62^5 instead of 10^5 links.

Computers generally don't know how in fancy bases unless you teach it to do so, and teaching MySQL to count like that is way over my head -- hey, cut me some slacks, I'm a PHP guru, not a MySQL guru -- so I'm letting MySQL count in its native auto increment on an unsigned integer. With that, I also get a fancy pool of numbers to work with... Unsigned BIGINT in MySQL goes up to 18446744073709551615 to be exact. That's eighteen quintillion, four hundred and forty six quadrillion, seven hundred and seventy four trillion, seventy three billion, seven hundred and nine million, five hundred and fifty one thousand, and six hundred and fifteen. Or in short: quite-a-mouth-full (see, wasn't that easier?).

Now, we obviously don't expect to house that much links in the URL shortener database, but its always fun for a small challenge. PHP can't count that much in integers (default int size is 4 bytes, and we'd need around 8 to 9 bytes to match that), and floats aren't that accurate when we're doing math (decimal precision issues), so we'll obviously need something better.

In comes BCMath Arbitrary Precision Mathematics. BCMath allows us to work with arbitrary large numbers with arbitrary precision through some nifty black magic API function calls. So anyways, after a few minutes of tinkering and editing, I present you a quick and simple base62 class for you to use in your application!

<?php
/**
 * Base 62 Encoder / Decoder Class
 * (c) Andy Huang, 2009; All rights reserved
 *
 * This code is not distributed under any specific license, 
 * as I do not believe in them, but it is distributed under
 * these terms outlined below:
 * - You may use these code as part of your application, even if it is a commercial product
 * - You may modify these code to suite your application, even if it is a commercial product
 * - You may sell your commercial product derived from these code
 * - You may donate to me if you are some how able to get a hold of me, but that's not required
 * - You may link back to the original article for reference, but do not hotlink the source file
  * - This line is intentionally added to differentiate from LGPL, or other similar licensing terms
 * - You must at all time retain this copyright message and terms in your code
 */
class base62 
{
	static $characters = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';
	static $base = 62;

	public function encode($var) 
	{
		$stack = array();
		while (bccomp($var, 0) != 0)
		{
			$remainder = bcmod($var, self::$base);
			$var = bcdiv( bcsub($var, $remainder), self::$base );
	
			array_push($stack, self::$characters[$remainder]);
		}
	
		return implode('', array_reverse($stack));
	}
	
	public function decode($var) 
	{
		$length = strlen($var);
		$result = 0;
		for($i=0; $i<$length; $i++) 
		{
			$result = bcadd($result, bcmul(self::get_digit($var[$i]), bcpow(self::$base, ($length-($i+1)))));
		}
	
		return $result;
	}
	
	private function get_digit($var) 
	{
		if(ereg('[0-9]', $var))
		{
			return (int)(ord($var) - ord('0'));
		}
		else if(ereg('[A-Z]', $var))
		{
			return (int)(ord($var) - ord('A') + 10);
		}
		else if(ereg('[a-z]', $var))
		{
			return (int)(ord($var) - ord('a') + 36);
		}
		else
		{
			return $var;
		}
	}
}

If copy & paste isn't your thing, you can download the file directly: class_base62.phps.

Since it is a static class, you can invoke it directly without having to instantiate it. Simply do this:

require_once("class_base62.php");
base62::encode("100"); // returns "1c";
base62::decode("LygHa16AHYF"); // returns "18446744073709551615";

Happy coding! But please do let me know if you encounter any problems with the script, so I can fix it!

I have a NAS with four 400GB harddrives running a RAID 5 installation, which means I won't lose data on there unless two of the drives go bad. It's done through my TS-409 (shown to the right). Since I have all these space, I might as well use it to backup my MacBook regularly so I don't lose any of my important data. OS X users know, Time Machine is awesome. It helps you take hourly, daily, and weekly snapshots of your computer. But unfortunately, it only works with additional harddrives attached to the machine, OR Time Capsule on your network... right? Wrong. Today, we will sideways hack Time Machine, and make it work with your SMB (Windows) share folder.

Before you get started, counter intuitive as it may seem, please be sure to have your data backed up before proceeding. While the memo is written with the best of intentions to help people make backups, I will not be responsible for any data loss as result of you following through this memo of my. You have been warned.

Now then, let's move on.

If you head straight over to System Preferences -> Time Machine, you will notice that it does not allow you to select your SMB based share. This is probably because Apple wants you to buy Time Capsule / external hard drives, or it could be because hdiutil doesn't work too well with SMB based share. Either ways, we'll hack it to work with our SMB share.

First, head over to the terminal; typically Applications -> Utilities -> Terminal, or if you're like me, QuickSilver -> iTerm. Once you have your terminal launched, issue this command:

It's pretty long, and it might've gotten squeeshed here, but that's all in one line. What that does is that it modifies a hidden configuration setting set by Apple, for the System Preferences application, to get Time Machine to show unsupported network drives. Guess what's unsupported? Yep, you guessed it, SMB / Windows share drives. Now that if you have it enabled, you will see your drive as an option to back up to... but you're not done yet! As this alone will not work -- remember what I said about hdiutils?

The next step gets a little bit more complicated, so please read carefully and look at the screenshots I am attaching. What you'd need to do now is figure out what is your ethernet's MAC address. Go back to your terminal (if you've left it already) and enter this command:

You should get something like this as result:

Copy down the series of hexadecimal numbers without the colons; in my example, it would be: "0023df905fe8". You will need this number later, so don't lose it.

Next, head over to System Preferences -> Sharing, and look near your computer name. While your computer name can be anything (I, for example, have it in Japanese), the identifier on networks MUST BE alphanumeric, and some basic symbols. This is typically deduced from your computer name's ascii parts. Take a look at this screenshot:

Notice my says "chiisana-osx.local"? You want to note down the part before .local. So for my example, it'd be "chiisana-osx". Write yours down, and don't lose it, you'll need this later too.

Finally, ask yourself the question: "How big is my harddrive?" If you don't know this information, go to your desktop, select "Macintosh HD", and click "Command + I". In the new window, it should tell you your harddrive's capacity. Note down that number, and give or take double it, because you'll need some extra space to keep historical copies in the Time Machine. Now we have all the information we'd need.

Go to System Preferences -> Time Machine, and setup your Time Machine on your desired network drive. Please keep in mind that Time Machine will create the backup file at the root of that network share, so if you want it in a specific folder, make sure you adjust your share accordingly before mounting. It should get started creating the backup... but after a while, it will fail (oh no!)... because hdiutil doesn't really work with SMB shares. Now what? Now we create our own backup file... Your backup file should be named machine identifier, underscore, MAC address, dot, sparsebundle. In my example, it would be "chiisana-osx_0023df905fe8.sparsebundle", make sure you make your own backup file name correctly, or Time Machine will not work. Once you have your backup file name constructed, go back to the terminal and issue this command:

Replace xxxg with numbers of GB you would like to allocate for backup; IE: 200g for 200GB, 300g for 300GB, 1T for 1TB, etc.

Replace yyyyyyyy_zzzzzzzz.sparesbundle with your backup file name; IE: chiisana-osx_0023df905fe8.sparsebundle

The first line, cd, will set you to your home directory, regardless of where you are. The second line will create the backup sparsebundle for you. In my case, the 200G sparse bundle worked out to be around 115M, but your sizes may vary. Once you have this file, move it to your SMB share, and set your Time Machine to backup again. This time, Time Machine will magically work! But because you're copying your entire harddrive's contents (in my case, upwards to 100GB), the first time making the backup will take some time... After it is done once, it will be much more snappy in the future. Happy time traveling!