#!/bin/bash

# Custom prompt
PS1='\[\e]0;\w\a\]\n\[\e[32m\]\u@\h:\[\e[33m\]\w\[\e[0m\]$ '

Turns out none of the Windows fonts support box drawing characters (from what I’ve read, it seems that they don’t have the characters in the expected positions in the character table)…

The easiest solution is to tell MC to use non box drawing characters to draw boxes with the -a switch. The other solution is to get the Lucida ConsoleP Font. (307), and set rxvt to use it (as suggested by this guide).

How do you set the fonts? You could set them with command line switches, or use a .XResources file in your Cygwin home directory (base file from here)):

rxvt.font:             Lucida Console-14
rxvt.boldFont:         Lucida Console-14
rxvt.scrollBar:        True
rxvt.visualBell:       True
rxvt.loginShell:       True
rxvt.background:       Black
rxvt.foreground:       White
rxvt.saveLines:        3000
rxvt.cursorColor:      Green
rxvt.scrollBar_right:  True

If you want to use the box drawing font (you have to install it on the system first):

rxvt.font:             Lucida ConsoleP-14
rxvt.boldFont:         Lucida ConsoleP-14
rxvt.scrollBar:        True
rxvt.visualBell:       True
rxvt.loginShell:       True
rxvt.background:       Black
rxvt.foreground:       White
rxvt.saveLines:        3000
rxvt.cursorColor:      Green
rxvt.scrollBar_right:  True

If you use the standard DOS terminal for Cygwin, you may want to change the code page setting in the batch file to:

set CYGWIN=codepage:oem

The most troubling incident I’ve dealt with involved an attacker who exploited a security vulnerability in Valve’s server query protocol, which caused a serious degradation of service condition. I couldn’t simply block all the query packets, since legitimate clients needed to be able to query servers. To further complicate matters, the attacker was also spoofing IP headers, which ruled out the possibility of a simple firewall rule.

This particular vulnerability was not really bad design per say (although it was poorly designed), but more a really poor implementation. Here are the details:

When a client wishes to find out basic information about a server (player counts, game type, game version, etc), they send a packet to the server requesting the information. The server then locates all this information, creates a packet and replies.

Normally, the query protocol works perfectly, without any performance issues. However, the code that generates the replies is so poorly written, that a large number of query packets will generate lag spikes on the server, thus making the server unplayable (degradation of service). Did Valve require a handshake / challenge before replying with this expensive to generate packet? Nope.

To resolve the attack, I wrote a server plugin that hooks the Winsock recvfrom call, and replies to query packets (it generates the replies itself) from a high performance cache (it returns SOCKET_ERROR to the server so it doesn’t try to reply).

With this cache installed, the server works flawlessly. This makes me wonder, how could Valve have written such inefficient code, and having written it, consider it ready for production.

I’d like to take a minute here and remind everyone this is just one of many known (and inexplicably, not yet patched) vulnerabilities (in game and network based) in the Source engine.

Why anyone would compress a package designed for Windows in .lzma format? The only way to extract it is with a command line sdk tool. Even on Linux, distributing archives in .lzma format is a little strange.

Anyhow, to save everyone the trouble, here’s a package (includes C, C++ and all necessary tools) in .7z format (which can be extracted by 7-Zip, the best file archiver for Windows) -> MinGW Compiler Package (238).

I found something interesting in the event log yesterday:

PHP Warning:  [eAccelerator] This build of "eAccelerator" was compiled for PHP version 5.2.9. Rebuild it for your PHP version (5.2.9-2) or download precompiled binaries.

Now that error message makes perfect sense. The reason I didn’t see it the first time around is that PHP logged two messages separately at the same time. If I was reading a flat file log, I would’ve noticed it immediately.

After a few seg-faults, I realized that eAccelerator isn’t thread safe (I was running it under a thread safe server)… It is thread safe… I just wasn’t loading it in thread safe mode (see the manual for details). Whoops.

Following the path of logic, I went to the eAccelerator website in search of the appropriate files. Their Windows section directed me to SiteBuddy, which had a nice collection of binaries for various PHP versions. After determining my PHP version (5.2.9-2), I tried the closest match (5.2.9), and was greeted by the following error in the Windows event log:

Unable to start eAccelerator module in Unknown on line 0.

My initial reaction to the error: what the ****… (UPDATE: See this post for more details) After a quick Google search, I found that PHP modules must be built for the EXACT PHP version you plan to use them on.

Since I have just about every Microsoft C++ compiler, I figured compiling a new eAccellerator module for my version of PHP would be simple. I downloaded the archived PHP files I needed (now I understand why they keep archives), switched to the release configuration, and pressed build.

error C2466: cannot allocate an array of constant size 0

My reaction to this was about the same as the other one. After half an hour, I tracked down and fixed the problem, which was a broken Windows build configuration (which the PHP developers KNEW about, and marked as “Wont Fix”).

The solution was to make the changes suggested by sailormax.

In the end, everything compiled, and you’re reading my post through eAccelerator. I noticed that blog page loads are 2 – 3 times faster.

Ad blockers like ABP (Ad Block Plus) scan web pages for ads, and remove them. As simple as they are, ad blockers are incredible.

I installed ABP when I was trying to print an article from a coding website. There were so many ads on their main and print views of the article that printing it would have barely been worth the effort. I remembered that a friend of mine had talked about ABP, so I looked it up and installed it. After enabling it and returning to the website, the ads were gone, and I could actually print the article.

ABP also lets you block new ads that it doesn’t already detect with a few simple clicks. Some websites use JavaScript to display ads, and if ABP can’t block them, NoScript can.

Web masters should realize that intrusive ads will just cause more and more people to start using ad blockers, and start being reasonable.

To understand how one enum variable can be multiple values, you need to understand the bitwise AND and OR operations.

An OR operation compares two sets of bits. If either bit is 1, the result is 1, else, result is 0. In the below example, set 1 is the value of enum option 1, and set 2 is the value of enum option 2.

Set 1:  11001000
Set 2:  00110110
Result: 11111110

An AND operation compares two sets of bits. If both bits are 1, the result is 1, else, result is 0. In the below example, set 1 is enum option 1, and set 2 is the result from the OR above.

Set 1:  11001000
Set 2:  11111110
Result: 11001000

Notice what the result is? enum option 1. Using this logic, we can create the following snippet:

enum Status {STOP, START, RUN};

// Bitwise OR of START and RUN
Status s = START | RUN;

// If the result of a bitwise AND of s and START is START
// (if condition is true)
if ((s & START) == START))
   cout << "s is Start." << endl;

// If the result of a bitwise AND of s and RUN is RUN
// (if condition is true)
if ((s & RUN) == RUN))
   cout << "s is Run." << endl;

Pretty neat right? Well, there's one more use that I learned yesterday.

Suppose you wanted to find out if an integer was a power of 2. One person volunteered a somewhat complex algorithm using logarithms, and someone else said, it's faster to count the bits. After reading the bit counting algorithm several times, I realized how amazingly simple it was.

The binary number system, base 2, has two digits, 1 and 0. Every place value is a power of two (in the decimal / base 10 system, there are ten digits, 0 - 9, and every place value is a power of 10). What this means is, if only one bit is 1 in the byte (a byte is 8 bits) storing the number, it must be a power of two.

For example:

Binary Place value: From right to left, 2 ^ 0, 2 ^ 1, 2 ^ 2, etc.

128 64 32 16 8 4 2 1
1   0  0  0  0 0 0 0

The binary byte, 10000000, is 128 in decimal, and 128 is 2 ^ 7.