Terminal Awesomeness

The best way to make your desktop look nice is to add true transparency to your terminals. I got urxvt with true transparency enabled working with xcompmgr and it looks wonderful.

xcompmgr is a lightweight composite window manager.
urxvt is an xterm-like terminal lightweight and fast.

I'm using openbox as a window manager and hsetroot to set my desktop wallpaper. These are the contents of my ~/.config/openbox/autostart.sh :

hsetroot -fill ~/Desktop/desktop.jpg &
xcompmgr &
rxvt &
docker &

"docker" takes care of the system tray.

To enable transparency in urxvt you need to add these lines to your ~/.Xresources file:
URxvt*depth: 32
urxvt*background: rgba:0000/0000/0000/cccc
URxvt*background: rgba:0000/0000/0000/cccc
URxvt*foreground: green


Change the background and foreground to whatever color you want.

I believe desktop managers like kde or gnome are overrated. Openbox is great and doesn't consume your precious resources so u can use them for more important things like compiling code.

More VIM stuff

Set tab size:
set tabstop=2
Quick Write and quit
:wq
If you press Ctrl+S while on a terminal and it freezes then press the following to unfreeze:
Ctrl+Q
Working with tabs
:tabe file # Opens File
:tabn # goes to next tab
:tabp # goes to previous tab
:q # closes current tab
gt # will take you to the next tab
gT # will take you to the previous tab

Auto completion
Ctrl+N Ctrl+P
You can also invoke make and grep within vim
:grep args
:make
If you work on windows (gvim.exe) place your vimrc file in the VIM exe directory. You might need to set the environment variable VIM to the path where gvim.exe. Name your vimrc file as _vimrc

Moving to VIM

I decided to make vim my default text editor. Here are a couple of tips:

To get syntax highlighting in vim, add the following to your ~/.vimrc file or enter while editing (command mode, remember to press ':' before entering):
set background=dark # if your console background is dark..
syntax on
To get line numbers:
set nu
To split the screen in 2
split
vsplit # Vertical Split
To Move from split windows
Ctrl+W+(direction)
Open a file
open file
Close a file
close
Search Reg Ex
/regex
Goto Line Number
:number
Search word under cursor
*

I will post more eventually... vim kicks emacs butt by the way.

Ruby 1.9 C API - Object Instances

To Create a new instance of an object with class Class we will do this:

VALUE obj;

obj = rb_obj_alloc(Class); // Allocate space and create new instance
rb_obj_call_init(obj, 0, 0); // We call the initialize method for the object

Remember rb_obj_alloc() does not initialize the object and will seg fault if you use any custom data types in the object.

The 2nd and 3rd parameters of rb_obj_call_init() are the argument count (argc) and the constructor parameters array ( VALUE* ).

Ruby C API - Classes I

To create a class:


VALUE rb_define_class("name", parent_class);
VALUE rb_define_class_under(module_or_class, "name", parent_class);


To create a method:

rb_define_method(class, "name", c_function, argc)

argc is the number of arguments of the function, not including the first parameter of the c_function which would be the instance variable. Default Parameters can be implemented by setting this number to negative. (-1 would mean variable number of parameters, -2 would create an array to store the arguments)

"name" is the name of the method in ruby, for setter methods you would add the = to the name just like in ruby ( ie "name=" ). The same with operator for the [] operator you will use the string "[]" or "[]=".

The format of a ruby function accepting a variable number of arguments (argc = -1) would be like this:


VALUE function( int argc, VALUE* args, VALUE instance );


argc is the number of arguments passed.
args is an array containing the arguments.
instance is the instance of the object.

The format for a ruby function accepting an array of arguments (argc = -2) :


VALUE function( VALUE instance, VALUE array_of_arguments);


To access instance variables you will use this two methods:


rb_iv_get(instance, "variable");
rb_iv_set(instance, "variable", new_value);


stay tuned for part II.

Firefox Download Antivirus??

I recently noticed that firefox stopped responding for a couple of seconds every time i downloaded a file. The cause was the new virus scan feature. To disable this ( I tried Tools/Options but couln't find anything ) go to about:config and search for browser.download.manager.scanWhenDone then set it to false.

Ruby 1.9 C API - Exceptions I

rb_raise(exception_object, string_message);
rb_raise will try to call exception_object.new and display string-message as the exception error message.

Some of the built-in exceptions that can be raised are:
rb_eArgError
rb_eEOFError
rb_eException
rb_eFatal
rb_eFloatDomainError
rb_eIndexError
rb_eInterrupt
rb_eIOError
rb_eKeyError
rb_eLoadError
rb_eLocalJumpError
rb_eNameError
rb_eNoMemError
rb_eNoMethodError
rb_eNotImpError
rb_eRangeError
rb_eRegexpError
rb_eRuntimeError
rb_eScriptError
rb_eSecurityError
rb_eSignal
rb_eStandardError
rb_eStopIteration
rb_eSyntaxError
rb_eSysStackError
rb_eSystemCallError
rb_eSystemExit
rb_eThreadError
rb_eTypeError
rb_eZeroDivError


Listing RSS items with PHP in 3 lines


$rss = simplexml_load_file("rss feed url");
foreach ($rss->channel->item as $k)
echo $k->title . "\n";

In 4 lines with HTML formatting!!

$rss = simplexml_load_file("blog rss url!");
foreach ($rss->channel->item as $k)
$rss_list .= "<li>" . $k->title . "</li>\n";

$index_rss = "<ul>$rss_list</ul>";


Ruby 1.9 C API - Accepting Blocks

Executing the Block
rb_yield(Qnil);
Replace Qnil with the parameters you wish to pass to the block. The Result of the block is returned.
rb_block_given_p();
This function will tell you if a block was passed. Blocks are not counted as parameters so if your function only accepts a block then you need to specify 0 as the number of parameters.

Ruby 1.9 C API !! - Internal Structures

To access the internal structure of any Ruby object, 'ruby.h' defines the following macros:
#define RBASIC(obj) (R_CAST(RBasic)(obj))
#define ROBJECT(obj) (R_CAST(RObject)(obj))
#define RCLASS(obj) (R_CAST(RClass)(obj))
#define RMODULE(obj) RCLASS(obj)
#define RFLOAT(obj) (R_CAST(RFloat)(obj))
#define RSTRING(obj) (R_CAST(RString)(obj))
#define RREGEXP(obj) (R_CAST(RRegexp)(obj))
#define RARRAY(obj) (R_CAST(RArray)(obj))
#define RHASH(obj) (R_CAST(RHash)(obj))
#define RDATA(obj) (R_CAST(RData)(obj))
#define RSTRUCT(obj) (R_CAST(RStruct)(obj))
#define RBIGNUM(obj) (R_CAST(RBignum)(obj))
#define RFILE(obj) (R_CAST(RFile)(obj))
#define RRATIONAL(obj) (R_CAST(RRational)(obj))
#define RCOMPLEX(obj) (R_CAST(RComplex)(obj))

The most important are:
struct RFloat {
struct RBasic basic;
double float_value;
};

struct RBignum {
struct RBasic basic;
union {
struct {
long len;
BDIGIT *digits;
} heap;
BDIGIT ary[RBIGNUM_EMBED_LEN_MAX];
} as;
};

struct RBasic basic;
union {
struct {
long len;
char *ptr;
union {
long capa;
VALUE shared;
} aux;
} heap;
char ary[RSTRING_EMBED_LEN_MAX];
} as;

To Access the value of a float number you will call:

RFLOAT(ruby_value)->double_value;


Fixnum's (Integers) are stored differently:

10 in Ruby => (10 >> 1) in C
10 in C => (10 << 1 | 1) in Ruby
-10 in Ruby => (10 >> 1) in C
-10 in C => (10 >> 1 | 1) in Ruby (0xffffffed)

Bignums are usually 8 bytes (long long).