Some weird stuff about Ant

Currently I was using Ant with TestNG, please take note that when taskdef was missing in the code, the error is misleading.

<taskdef name="testng" classpathref="compilePath" classname="org.testng.TestNGAntTask" />

Below are the error generated:

Cause: The name is undefined.

Action: Check the spelling.

Action: Check that any custom tasks/types have been declared.

Action: Check that any <presetdef>/<macrodef> declarations have taken place.

std::nothrow new

Sometime during the new operation it might fail the process due to certain reason, this isn’t a big deal because exception could be a good friend to help out. Unfortunately exception still have its own limitation where it might not able to find the matching catch() clause due to the mistake of programmer. Or it could be in other situation; CRT’s new will return a NULL pointer whereas standard C++ will throw a std::bad_alloc exception when memory allocation failed.

Instead of worrying:-
1. How does the programmer know about how the exception going to catch?
2. The programmer has to be aware that he/she is dealing with CRT’s version of new or standard version of new.

Let’s put in alternative point of view:
What if the programmer knows that the new operator is NOT going to throwing any exceptions?

Thus, std::nothrow new would be the best solution. This will guarantee that the new will only return either a NULL pointer or a valid pointer.

Here is the sample usage:

Foo *p;
p = new(std::nothrow) Foo();
if( !p ) { exit(1); }

reference
1. msdn reference
2. C++ reference guide

How to get a file size?

stat structure is the guy to retrieve the file information, and this structure has a field called st_size where this field will retrieve the file size in bytes.

Here is the sample code:

struct stat FileStat;


if( stat( "MyFile", &FileStat ) == 0 ) {
   cout << FileStat.st_size << endl;
}

Who is popen()?

I found a new function called popen() in stdio.h. This is so interesting that this function wasn't in the C Programming Language (ANSI) but can be found in the Standard C Library book, according to this page. This function is useful where it can direct the *NIX (e.g. ls -l) command into a FILE pointer, and read the desire output from that pointer.

For example, ls -l command was type in the console like this:

huahsin68@huahsin68-laptop:~/Development/TestLab$ ls -l
total 12
drwxr-xr-x 3 huahsin68 huahsin68 4096 2010-06-12 19:45 Debug
-rw-r--r-- 1 huahsin68 huahsin68 241 2010-03-27 15:00 MyLog.000.txt
drwxr-xr-x 4 huahsin68 huahsin68 4096 2010-03-27 12:19 src

the same thing can be done using popen(), each line of the output will be direct to FILE pointer. Use fgets() to retrieve each line of the output. Below is the sample code:

FILE *fp;
char line[130];

fp = popen("ls -l", "r");
while ( fgets( line, sizeof line, fp)) {
   printf("%s", line);
}
pclose(fp);

A note on installing flash player in Ubuntu

If you are using 'root user' during the installation of Linux Debugger and Standalone Players for Flash Developers, it will prompt an message to locate the installation path of Mozilla. Using whereis command to locate the mozilla folder, for my case, the path /usr/lib/mozilla will be shown. Unfortunately the installation wizard will complain that particular path was invalid. According to the suggestion from Ubuntu forum, giving this path /usr/lib/firefox- will be more accurate.

If the user wasn't a 'root user' during the installation, the installation will proceed just as normal. The destination of the installation files will locate at /home//.mozilla/plugins.

My GoogleAppEngine is working now!!

Hurray!!

Finally I have successfully get my Google App Engine up and running. I am able to see the hello world string appear in my browser when I'm pointing my URL to localhost:8080. Following the tutorial provided by Google (here is the link), it wasn't mention clearly on how the Hello World application suppose to be running. It just mention this:

google_appengine/dev_appserver.py helloworld/

Initially I tough I must have my Apache setup in order to run the Google App. hehe...

I have my Google App Engine SDK install in one directory, say Directory A. And then I have my source code locate in Directory B. It doesn't matter where the source code must put, it just my development style. When compiling the source code, it will automatically fire up the server. This is so different from the way I did in programming, where I have to tell the compiler which file to compile. Whereas Google App Engine "compiler" target on the whole directory. In order words, in the helloworld directory, I have app.yaml and helloworld.py, I just need to supply the helloworld directory instead of single individual file, like this:

./dev_appserver.py HelloWorld

One thing to note, the ./ simbol must put at the front of dev_appserver.py, otherwise Linux will not able to recorgnise that command.

Enjoy your programming @!

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My first attempts to OSX86

I have been spending a lot of my effort on searching OSX86 v10.6 operating system. Anyhow the feed was so limited. The average download speed was about 3KB - 5KB, and required 18 - 20 days to complete the download. One of my friend shares out his OSX86 v10.4.x to me. Although it is quite old to me, but I am still OK with it because I just need it to learn Xcode programming. Trying the whole night to install it in Virtual Box and VMWare, neither one is working. Fortunately I found OSX86 v10.5.5, the progress is still downloading, hope this will bring me some good news.

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