# How to Write Blog via Vim

Today, I find a vim plugin called vimrepress. So I install it and write this blog here.

Note: this blog is expired for it was for Wordpress. However currently this blog is built with Octopress instead of Wordpress.

# Checklist Before Launching a Website

Just record these steps for possible uses in the future.

• Check the favicon of the website

• Check the title and meta data: add description and keywords

• Performance test, get the maximum concurrent access the website can bear

• Database security check

• Database backup configuration

• Web server backup

• Cache images, java script and css files.

• Use gzip to compress web pages.

• Use a dedicate domain name and server for images and other static files.

• Write the robots.txt file

• Write the sitemap.xml file

• Use optipng to compress png and gif files

• Use jpegoptim to compress jpeg files

• Use Google’s Chrome and PageSpeed plugin to optimize website’s speed

# How to Translate Apache’s “RewriteRule” Into Nginx’s “Rewrite”

There are many cases you need to use friendly url. If you are using Apache, tipcially you can activate the URL rewriting module and write some rewriting rules with .htaccess file; While if you are using Nginx, you can also write some rewriting rules. Both of them support regular expression, so it’s easy to translate from one to the other.

To translate from the Apache’s rewriting rule to the Nginx’s, simply do the following substitutions:

This is an adaptive color selector. It can dynamically choose which color of checkmark to use. When a light color is chosen, a black checkmark display; while when dark color is chosen, a white checkmark display.

Here is a screenshot.

# Replace Strings for All Files in a Folder

In my previous blog, I wrote the code to replace all string in a file: http://leons.im/2011/02/replace-all-strings-in-a-file/. Today, I write a cooler code – It can replace all strings in many files, actually it can replace all strings in files that are in a same folder.

# Always “Clear” the “Float”

Unless you really want to use Block Formatting Context, it’s usually a good idea to clear the float.

I have got this error many times. Today, I dived into it and resolved it.

I use php-fpm and nginx on my server. Occasionally, I got 502 bad request error. When I check the nginx log, it says upstream sent too big header. In my memory, the default buffer size if big enough. To make sure it’s not caused by this, I add the following lines to the nginx configuration file:

# My Certificates for CS101 and CS373 @ Udacity

I received Certificate of Accomplishment with Highest Distinction, which the highest level of certificates, from Udacity for both CS101 (Introduction To Computer Science - Building A Search Engine) and CS373 (Programming a Robotic Car).

# PID Control

When I was a college student, I participated a contest of mathimatical model. It’s a physical problem, which I didn’t find the model to solve. While I am studying the Udacity’s class Progamming a Robotic Car, and when it comes to PID control, it occurs to me that it’s the model exactly to solve the contest’s problem!

PID control is really an interesting and excellent algorithm. The detail information can be found at Wikipedia. The main point is that the control system has 3 parts: the Proportional, the Integral and the Derivative.

The formular is:

$$u(t) = MV(t) = K_pe(t)+K_i\int_0^t \! {e(\tau) \, \mathrm{d}\tau}+K_d\dfrac{d}{dt}e(t)$$

# Python Script for Getting a Random Address With Google Map API

With Google Map API, you can do a lot of thing. Here I will use it to turn latitude and longitude into human-readable addresses.

# Python Code for Counting LOC(Lines of Code)

Before I know CLOC, SourceCounter or Ohcount, I write this script.

# Vimrc

I’m using vim while still using emacs.

Just record my .vimrc file here.

# Pyramid + Nginx + uWSGI + MySQL

This article describes how to set an development and production environment for Pyramid web framework on a Linux platform with Nginx, uWSGI and MySQL.

# Do Not Use Inline-block in CSS (Obsolete)

UPDATE: As Vensires mentions in the comment, this post is obsolete.

Usually, when we want to arrange some blocks horizontally with CSS, we may choose to use float: left; property, or display: inline-block; alternatively.

According to http://www.quirksmode.org/css/display.html, inline-block is not supported by IE 5.5 and it’s not completely supported by IE 6 and IE 7.

# Anti-Debug With Trap Flag Register

Let’s play an interesting Crack-memuckis’s crackme #2.

When you run the crack-me with a debugger, say OllyDbg, the program pops up a message box saying “What the hell are you doing in my app with a debugger?” and then exists, but when you run the crack-me without a debugger, just double-click on it, it runs normally.

# My First Keygen

Recently, I’m reading pediy’s book: Encryption and Decryption. This is a really good book with many practical technologies and skills, and it’s also very interesting. In Chapter 2, I met a problem, so I cracked the demo crack-me program with ollydbg, but I’m not satisfied with that, so I studied the encrytion algorithm and wrote a keygen program.

The main algorithm is very simple, but it took me a lot of time to deal with the multi-byte characters problems, and I found there is another defination of unicode on Microsoft’s platform! I can’t figure out why Micro\$oft didn’t use UTF-8 to build his system just like Macintosh, because with UTF-8, we programmers don’t have to deal with these troubles at all. Anyway, Windows is such a snorty that most people still have to use it.

# A Simple Implementation of Solving Sudoku

Sudoku is a popular game. Howerver, solving Sudoku is sometimes not so easy, so I wrote a program to help me do this job.