I just knew this problem a month ago when one of my friend’s website on my server being hacked and installed a background program. The background program generate huge and useless image and movie files at server.

After hours of inspection at my server, I found the background progam ran under apche’s process. The background program called “footer.gif”. Smart huh? They name the background program as a image file’s name so that people can’t find it.

[Read more…]

How do we swap values of two integer variables?

Normally we will introduce a third variable as the temporay storage. For example in C/C++:

int a = 123456;
int b = 567890;
int temp;

temp = a;
a = b;
b = temp;


Ok the question now is: How do we swap values of two integer variables without third variable?

Here is the trick:

int a = 123456;
int b = 567890;

a ^= b;
b ^= a;
a ^= b;


Don’t believe? You can try it out yourself.
Note:

• only for integer values (eg. 8, 16, 32, 64 bits integers)
• ^ means eXclusive OR (XOR)

Explaination:
When a value is XOR with another value, the result is actually “storing” value of two values. When one of the original value is XOR again with the result value, you will get the another value. For example:

int a = 123;
int b = 456;
int resultOfXOR;

resultOfXOR = a ^ b; // "storing" 2 values

resultOfXOR ^ a; // return value of b
resultOfXOR ^ b; // return value of a


From the above code

int a = 123456;
int b = 567890;

a ^= b; // storing a^b into a. a becomes result of XOR
b ^= a; // get value of original a by resultOfXOR^b and store into b. Now b = 123456.
a ^= b; // get value of original b by resultOfXOR^b and store into a. Now a = 567890.

// Finally b = 123456 and a = 567890


That’s the beauty of XOR.

I had tried out the code Recent WordPress Post in Sidebar suggested by EngLee. Although the code did shows the recent posts correctly but some functions (eg: is_page() and is_home() are not working properly when it is after the portion of the code. My guess is the wordpress loop in the code modified value of some global variables.

I have a workaround for it. Before using the is_home() or is_page() function, I save the returned in a temporay variable, call the recent posts loop, and use the temporary variable later when neccessary.

Today when I search for wp_get_archives() in WordPress WIki, I found that I can generate recent wordpress posts in the more easier way. Here is the code:

<li>
	<h2>Recent Posts</h2>
	<ul>
		<?php wp_get_archives('type=postbypost&limit=10'); ?>
	</ul>
</li>

Simple and tidy :)

Added feed for each category in www.blogtal.com

For example:
Technology:
http://www.blogtal.com/categories/technology

Feed for Technology
http://www.blogtal.com/categories/technology/feed

For a better performance purpose, all feed entries (up to 20 latest pings) are loaded from cache. Therefore there is no database query when the feed is loaded. Later, I might need to increase the size of cache to cater more pings for categories.