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  The most stupid C bug ever

I have been programming for a number of years already. I have seen others introduce bugs, and I have also introduced (and solved!) many bugs while coding. Off-by-one, buffer-overflow, treating pointers as pointees, different behaviors or the same function (this is specially true for cross-platform applications), race conditions, deadlocks, threading issues. I think I have seen quite a few of the typical issues. Yet recently I lost a lot of time to what I would call the most stupid C bug in ...

   C,Bug,Comment,Back slash     2012-04-22 03:40:49

  Tricks with Direct Memory Access in Java

Java was initially designed as a safe managed environment. Nevertheless, Java HotSpot VM contains a “backdoor” that provides a number of low-level operations to manipulate memory and threads directly. This backdoor – sun.misc.Unsafe â€“ is widely used by JDK itself in packages like java.nio or java.util.concurrent. It is hard to imagine a Java developer that uses this backdoor in any regular development because this API is extremely dangerous...

   Java,Directly memory access,Tricks,JVM     2012-02-13 05:31:19

  Install and setup vsftpd on AWS server

When developing websites, frequently we may need to upload source codes to the remote server. To ease of thew work, many website developers set up FTPs to upload the files. This post is a tutorial on how to install and setup vsftpd on a server. vsftpd is a very popular FTP service on Unix-like systems. Open command terminal, then install the vftpd by issuing command yum install vsftpd or sudo apt-get install vsftpd After installing the vsftpd, the config file needs to be updated based on the ope...

   FTP,vsftpd,AWS,Passive,Active     2015-02-02 02:20:27

  JavaScript's Two Zeros

JavaScript has two zeros: -0 and +0. This post explains why that is and where it matters in practice. The signed zero Numbers always need to be encoded to be stored digitally. Why do some encodings have two zeros? As an example, let’s look at encoding integers as 4-digit binary numbers, via the sign-and-magnitude method. There, one uses one bit for the sign (0 if positive, 1 if negative) and the remaining bits for the magnitude (absolute value). Therefore, -2 and +2 are encoded as f...

   JavaScript,zeros     2012-03-24 05:21:49

  Communicating Between Widgets in a Rich Internet Application

As a part of our October Free Dojo Support initiative, we received the following question from Manu Subramanian about how to manage communication between distinct components in a rich internet application: We are building an application with dojo. It does have many inter connected interface parts. For example it does have a top bar with drop down buttons. The menu items opens tabs in a tab controller. In general we need to call functions from different widgets or there are many interconne...

   Internet application,Rick internet,Widget,comminucation     2012-03-16 10:49:36

  Currying in Python

What is Currying? Currying is like a kind of incremental binding of function arguments. Let’s define a simple function which takes 5 arguments: 1def f(a, b, c, d, e):2    print(a, b, c, d, e) In a language where currying is supported, f is a function which takes one argument (a) and returns a function which takes 4 arguments. This means that f(5) is the following function: 1def g(b, c, d, e):2    f(5, b, c, d, e) We could emulate this behavior the...

   Python,Curring,Binding,Implement     2012-03-19 12:59:10

  Differences among Enter,F5 and Ctrl+F5 in webpage refresh

When we press Enter, F5 or Ctrl+F5 to refresh a webpage, is there any difference among them? Actually it's yes, we can find the difference from the request header and response header information. There are two cases about pressing Enter in the address bar. First if the page requested is cached and not expired in the browser, we can find the header information sent by the browser is : Host 192.168.3.174:8080 User-Agent Mozilla/5.0 (Windows NT 5.1; rv:5.0) Gecko/20100101 Firefox/5.0 Accept ...

   Refresh,F5,Ctrl+F5     2013-06-13 22:03:35

  The tic-tac-toe game with Python

In this tutorial, we will show how to build a tic-tac-toe game with Python. We will use functions,arrays,if statements,while statements, for loops and error handling etc. First, we need to create two functions, the first function will display the borad of the game: def print_board(): for i in range(0,3): for j in range(0,3): print map[2-i][j], if j != 2: print "|", print "" Here we used two for loops to loop through the map, this map is...

   Python,Tic-Tac-Toe     2013-07-30 02:49:09

  MaxHeapSize in JVM

MaxHeapSize is an option which is to set the JVM maximum heap size can be allocated. We can specify the MaxHeapSize as VM argument when we run the program by setting -XX:MaxHeapSize=, here can be 2M, 20M, 200M etc. We can also view the current MaxHeapSize set by setting different JVM options. To view the MaxHeapSize, we can use two JVM options : -XX:+PrintFlagsFinal and -XX:+PrintCommandLineFlags. Below is one example when running -XX:+PrintFlagsFinal: bool MaxFDLimit ...

   JVM,MaxHeapSize,Alignment     2014-06-17 07:01:50

  CASSANDRA data model

Cassandra is an open source distributed database, it combines dynamic key/value and column oriented feature of Bigtable. Features of Cassandra are: Flexible schema, no need to design schema first, it's very convenient to add or delete strings Support range search on keys High usability, extensible. The single node error will not affect the cluster. We can think Cassandra's data model as a 4 or 5 dimensional Hash. COLUMN Columns is the smallest data unit in Cassandra, it is a 3 dimensional data...

   Cassandra,database,sort     2013-06-08 22:07:40

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