Kailas Patil

Email Address verification using Perl script

2011-11-14T17:40:00.000+08:00

Checking correctness of one email address is easy and can be done manually, however, if you want to validate a bunch of email addresses then automated script plays a very handy role.

I would like to thank my colleague and friend "Sai Sathyanarayam" for giving me this script. I think this might be useful for others therefore, I am posting it here.

# email.pl file

#open "email.txt" file from current directory,

# email.txt file contains email addresses separated by , (comma) and each address is on new line

open(FILE,"email.txt");

while($line = <FILE> ) {

chomp($line);

if($line =~ /,/) { $line = $`; }else { print $line." is invalid\n";}

if ($line =~ /^(\w|\-|\_|\.)+\@((\w|\-|\_)+\.)+[a-zA-Z]{2,}$/)

{

print "$line is valid\n";

}

else {

print "$line is invalid\n";

}

Sample email.txt file is as follows:

xyz@abc.com,

pqr@mnr.ac.in,

To perform validation test run following command:

$ perl email.pl

JaegerMonkey Architecture

2011-08-26T11:58:00.001+08:00

JaegerMonkey is a JavaScript engine used in Firefox 4.0 and later versions. The SpiderMonkey JavaScript engine was used by Firefox for version 3.0 or earlier. TraceMonkey is a tracing engine which is an improvement to SpiderMonkey. Trace Monkey was used in Firefox 3.5 and above versions. Before we will look into architecture of JaegerMonkey, lets first have a glance at TraceMonkey JavaScript engine who is a predecessor of JaegerMonkey.

TraceMonkey Overview

TraceMonkey uses a trace monitor called jstracer. The jstracer monitors a script as interpreted by SpiderMonkey. Whenever jstracer sees a code that would benefit from the native compilation, it activates it recorder. The recorder records the execution of the IR and creates NanoJIT Low Level Intermediate Representation, which is then compiled into native code. NanoJIT produces optimized code. More information on TraceMonkey and its architecture diagram is available here.

JaegerMonkey Architecture

JaegerMonkey used in Fireox 4.0 and above version is Just-in-Time (JIT) JavaScript execution engine. JaegerMonkey JIT engine produces native code for JavaScripts. Usually JIT engines take an intermediate representation (IR) from a compiler and produce native (machine) code and execute it on the fly. Therefore, JIT engines do not parse the code or check its syntax, or create intermediate representation (IR) of code.

Hence, JavaScript engine in Mozilla Firefox we divide into two parts: front-end and back-end. The front-end is responsible to parse the script, check its syntax and generate intermediate representation (IR) of script required for native code generation. The back-end is responsible for generating native code and memory management.

In Mozilla Firefox front-end is SpiderMonkey which parses script syntax and generates an intermediate representation (IR) of the script. In SpiderMonkey intermediate representation of script is bytecode of the script. This generated bytecode is then fed to JaegerMonkey JIT engine to be compiled into machine code. JaegerMonkey is a method-base JIT JavaScript engine which compiles script into non-optimized machine code. JaegerMoneky uses Nitro (borrowed from the WebKit project) as its back-end assembler.

Nitro does memory management and code generation in JaegerMonkey.

Nitro contains two parts assembler and memory unit. Assembler handles the code assembly and memory unit handles allocation and deallocation of memory for native code. The bulk of the bytecode to native code translation is performed in the mjit::compiler class and it can be found in js/src/methodjit/Compiler.cpp. This compiler class translates SpiderMonkey bytecode instructions to their native code block equivalents using the AssemblerBuffer and LinkBuffer helper classes.

JaegerMonkey uses inline cache to improve the performance. Inline cache is used to perform faster object type lookups. JavaScript supports dynamic typing during runtime. To support this feature, in SpiderMonkey JSOP_GETPROP bytecode is responsible to return the value of a specific property by looking up its type first. SpiderMonkey uses property cache which stores the Shape of existing objects. Shape is a structure in SpiderMonkey that defines how the object can be accessed.

Inline Caching for good locality

When JIT compiles a property access bytecode, emitted machine code look like as follows:

type <- load addressof(object) + offsetof(JSObject, type)

shapeIsKnown <- type equals IMPOSSIBLE_TYPE

None <- goto slowLookupCode if shapeIsKnown is False

property <- load addressof(object) + IMPOSSIBLE_SLOT

JagerMonkey uses self modifying code to inline cache the Shape of the object. Self modifying code is a code that modifies code that currently exists in memory. When first time JaegerMonkey performs a property access on object its shape is unknown therefore shapeIsKnow will be false. Hence slowLookupCode will be executed. After slowLookupCode resolves the property it fills the appropriate value for IMPOSSIBLE_TYPE and IMPOSSIBLE_SLOT. Hence, next time when this piece of code is executed, if the type of object is not change then shapeIsKnown return true and there is no need to go into slowLookupCode. This technique of modifying JIT-compiled code to reflect a probable value is called as inline caching: inline, as in "in the emitted code"; caching, as in "cache a probable value".

However, JavaScript supports dynamic typing. This is handles by polymorphic inline caching (PIC). Lets consider an example of PIC code:

var vals = {1, "hello", [1, 2, 3]};

for (var i in vals) {

document.write(vals[i].toString());

}

In above code vals array contains different data types such as a Number, a String and a array. For each object in the array, the interpreter has to perform an expressive type lookup and determine the correct toString method to call. JaegerMonkey uses PIC slots to colve this problem, that is make a chain of cache entries. It creates several blocks of native code that perform property lookups for types the object has already been seen as. It the first type does not match, then a branch is taken to the next code block to perform a lookup. If type is match then it performs a fast slot lookup. According to our example, first time it recognizes Number object and fills cache entry for it. Second time its a String. So a new piece of code memory is created for type String and modify the jump of first lookup (that is, Number type mismatch in our example) to go to this newly created piece of code memory instead of slowLookupCode. and so on.

References:

1. PICing on JavaScript for fun and profit

2. Attacking Clientside JIT Compilers [BlackHat 2011]

How to Merge Multiple PDF files into single PDF file on Ubuntu

2011-04-01T15:43:00.000+08:00

Multiple PDF files can be merged into single PDF using two different ways: ghostscript or pdftk

A. Use Ghostscript to merge PDF files
Steps:
1. Install two pacakeges GhostScript and PDFtk tools.
$ sudo apt-get install gs pdftk

2. Use following command to combine multiple files into single PDF file. The output file name is "singleCombinedPdfFile.pdf". The input file names are all files in the current directory, bcoz we used "*.pdf".

$ gs -dNOPAUSE -sDEVICE=pdfwrite -sOUTPUTFILE=singleCombinedPdfFile.pdf -dBATCH *.pdf

If you want to join PDF files in specific order then you can also use file names.
$ gs -dNOPAUSE -sDEVICE=pdfwrite -sOUTPUTFILE=singleCombinedPdfFile.pdf -dBATCH 1.pdf 2.pdf 3.pdf

B. Use pdftk (PDF toolkit) to merge multiple PDF files into Single PDF file
1. To merge PDF files by using names of the source PDF files:
$ pdftk one.pdf two.pdf three.pdf cat output 123-combined.pdf

2. To merge PDF files using wildcard when number of files are large and its not feasible to input filenames of all files:
$ pdftk *.pdf cat output combined.pdf

3. Select specific pages from Multiple PDFs and create new PDF document:
$ pdftk A=one.pdf B=two.pdf cat A1-7 B1-5 A8 output combined.pdf

Embed fonts in PDF file using PDFLaTex

2011-03-14T11:53:00.001+08:00

This post explains how to embed fonts in PDF file.

Embedding the font in the PDF file is useful when you are preparing a paper for conference submission or you want to ensure that your PDF file looks exactly same on other's machine as it does on your computer.

In this post I will explain how to do it on Linux machine. I am not sure how to achieve the same on Windows computer.

We will use tool "pdffonts" to examine PDF file.

$ pdffonts mypaper.pdf

name type emb sub uni object ID

------------------------------------ ----------------- --- --- --- ---------

HVGYIY+NimbusRomNo9L-Medi Type 1 yes yes no 110 0

TFVQMQ+NimbusRomNo9L-Regu Type 1 yes yes no 111 0

XHGNKU+NimbusRomNo9L-MediItal Type 1 yes yes no 113 0

UUGCZC+NimbusRomNo9L-ReguItal Type 1 yes yes no 114 0

FDULPW+CMSY7 Type 1 yes yes no 148 0

SPCNWZ+NimbusMonL-Regu Type 1 yes yes no 150 0

ABCDEE+Times TrueType yes yes no 152 0

Arial TrueType no no no 153 0

Arial CID TrueType yes no yes 154 0

Arial TrueType no no no 220 0

Arial CID TrueType yes no yes 221 0

ABCDEE+Times TrueType yes yes no 222 0

Arial,Italic TrueType no no no 223 0

ZLLMAJ+CMMI10 Type 1 yes yes no 257 0

Arial TrueType no no no 259 0

ABCDEE+Calibri TrueType yes yes no 260 0

Arial,Italic TrueType no no no 261 0

Arial TrueType no no no 282 0

Arial,Italic TrueType no no no 283 0

The important columns are name and emb. The "name" column displays the name of the font and the "emb" column shows whether that font is embedded in your PDF file or not. "yes" is "emb" column indicates that the font is embedded in the PDF file and "no" indicates that the font is not embedded in the PDF file.

For example, in the above oputput, Arial, and Arial,Italic fonts are not embedded in the PDF file.

To embed the un-embedded fonts into your PDF file using PDFLaTex:

$ updmap --edit

The above command will open the configuration file for pdflatex.

Find the pdftexDownloadBase14 directive and make sure it is true. That is, when you're done, the following line should be in the file:
pdftexDownloadBase14 true

Save the file and rebuild your PDF file using "pdflatex".

Then check your PDF file using "pdffonts" command. It should now have embedded all the fonts use in your PDF file.

If there are still some fonts missing then it might be because your have embedded another pdf file (as a graphics) into your "mypaper.pdf" file.

In that case, you need to embedded the fonts into those embedded PDF files as well.

If you included figures in your PDF file then follow the steps given below:
1. Convert your PDF file to PS file
  $ pdftops mypaper.pdf

2. Convert back ps file to pdf using "prepress" settings
  $ ps2pdf14 -dPDFSETTINGS=/prepress mypaper.ps

Conversion from PDF to PS and again back from PS to PDF my cause some formatting errors. I recommend you to double check your PDF file for formatting errors.

3. Check PDF fonts using pdffonts command
  $ pdffonts mypaper.pdf

LibXML Tutorial

2011-03-11T00:14:00.032+08:00

In this blog post I will show some basic function of libxml, which is a freely licensed C language XML library.
This post gives an idea to beginners how to manipulate xml files using libxml library function. This post does not cover all XML API available in libxml, but it just gives an idea how to use libxml API's with the help of some basic functions.

For detailed XML API list please visit official website of libxml.

To Parse XML file:
xmlDocPtr doc; // pointer to parse xml Document

// Parse XML file

doc = xmlParseFile(xmlFileName);

// Check to see that the document was successfully parsed.

if (doc == NULL ) {

fprintf(stderr,"Error!. Document is not parsed successfully. \n");

return;

}

To Get the root Document:

// Retrieve the document's root element.

cur = xmlDocGetRootElement(doc);

// Check to make sure the document actually contains something

if (cur == NULL) {

fprintf(stderr,"Document is Empty\n");

xmlFreeDoc(doc);

return;

}

To Get the child Nodes of the current node element:

  cur = cur->xmlChildrenNode;

To Search for an attribute:

// search for "hash" attribute in the node pointed by cur
attr = xmlHasProp(cur, (const xmlChar*)"hash");

To add new Attribute:

/*
* New Attribute "hash" is added to element node pointed by cur,
* and default value of the attribute is set to "12345678"
*/
attr = xmlNewProp(cur, (const xmlChar*)"hash", (const xmlChar*)"12345678");

To Save XML document to Disk:

xmlSaveFormatFile (xmlFileName, doc, 1);

Complete Example is given below:
Suppose data.xml file is as follows:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE root SYSTEM "secPolicy2.dtd">
<root>
<url>
    <host hash="12345678">www.example1.com</host>
    <sctxid>2</sctxid>
</url>
<url>
    <host>www.example2.com</host>
    <sctxid>2</sctxid>
</url>
    <url>
    <host>www.example3.com</host>
    <sctxid>3</sctxid>
</url>

</root>

Following program reads the above xml file supplied as command line argument.
It adds "hash" attribute with default value set to "12345678" if its not present in the "host" element node.

* Filename = xmlexample.c

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <libxml/xmlmemory.h>
#include <libxml/parser.h>

/*
* Parse URL Element Node in XML file
* <url>
*    <host hash="hash_val_of_hostname">www.example.com</host>
*    <sctxid>Integer</sctxid>
* </url>
*/
void parseURL (xmlDocPtr doc, xmlNodePtr cur) {
xmlChar *key;
xmlAttrPtr attr;

// Get the childern Element Node of "url" node
cur = cur->xmlChildrenNode;

while (cur != NULL) {
    // check for "host" childern element node of "url" node
    if ((!xmlStrcmp(cur->name, (const xmlChar *)"host"))) {
      key = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
      fprintf(stderr,"host: %s\n", key);
      xmlFree(key);

      // search for "hash" attribute in the "host" node
      attr = xmlHasProp(cur, (const xmlChar*)"hash");

      // if attr is not found then set it
      if(attr == NULL){
    /*
    * Add the Attribute and value of the attribute
    */
    attr = xmlNewProp(cur, (const xmlChar*)"hash", (const xmlChar*)"12345678");

    /* Attribute is now set and has value.
    * Just retrieve the value and display it
    */
    key = xmlGetProp(cur, (const xmlChar*)"hash");
    fprintf(stderr,"hash: %s\n", key);
    xmlFree(key);

      }else{
    /* Attribute is available
    * Just retrieve the value and display it
    */
    key = xmlGetProp(cur, (const xmlChar*)"hash");
    fprintf(stderr, "hash: %s\n", key);
    xmlFree(key);
      }

    } // end of IF loop " host"

    // check for "sctxid" childern element node of "url" node
    if ((!xmlStrcmp(cur->name, (const xmlChar *)"sctxid"))) {
      key = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
      fprintf(stderr,"sctxid: %s\n", key);
      xmlFree(key);
    } // end of If loop "sctxid"

      cur = cur->next;
} // end of While loop

return;

} // end of parseURL function()

/*
* Parsing the XML file and Reading the Element Nodes
*/
static void parseDoc(char *xmlFileName) {
xmlDocPtr doc; // pointer to parse xml Document
xmlNodePtr cur; // node pointer. It interacts with individual node

// Parse XML file
doc = xmlParseFile(xmlFileName);

// Check to see that the document was successfully parsed.
if (doc == NULL ) {
    fprintf(stderr,"Error!. Document is not parsed successfully. \n");
    return;
}

// Retrieve the document's root element.
cur = xmlDocGetRootElement(doc);

// Check to make sure the document actually contains something
if (cur == NULL) {
    fprintf(stderr,"Document is Empty\n");
    xmlFreeDoc(doc);
    return;
}

/* We need to make sure the document is the right type.
   * "root" is the root type of the documents used in user Config XML file
   */
if (xmlStrcmp(cur->name, (const xmlChar *) "root")) {
    fprintf(stderr,"Document is of the wrong type, root node != root");
    xmlFreeDoc(doc);
    return;
}

/* Get the first child node of cur.
   * At this point, cur points at the document root,
   * which is the element "root"
   */
cur = cur->xmlChildrenNode;

// This loop iterates through the elements that are children of "root"
while (cur != NULL) {
    if ((!xmlStrcmp(cur->name, (const xmlChar *)"url"))){
      parseURL (doc, cur);
    }
    cur = cur->next;
}

/* Save XML document to the Disk
   * Otherwise, you changes will not be reflected to the file.
   * Currently it's only in the memory
   */
xmlSaveFormatFile (xmlFileName, doc, 1);

/*free the document */
xmlFreeDoc(doc);

/*
   * Free the global variables that may
   * have been allocated by the parser.
   */
    xmlCleanupParser();

return;

} // end of XMLParseDoc function

int main(int argc, char **argv) {
char *xmlFileName;

if (argc <= 1) {
    printf("Usage: %s inputfile.xml\n", argv[0]);
    return(0);
}

// Get the file name from the argv[1]
xmlFileName = argv[1];

// Custom function to parse XML file
parseDoc (xmlFileName);

return (1);
}

To compile the above program use following command:
$ gcc `xml2-config --cflags --libs` -o xmlexample xmlexample.c

To run the program, use following command:
$ ./xmlexample data.xml

Mercurial HG HOWTO guide

2011-02-28T22:47:00.002+08:00

In this tutorial I will cover the basic commands you will need to use mercurial.
hg help is your first friend and Mercurial Wiki is your second.

Help for Command:
$ hg help <command>
or
$ hg <command> - -help

Commands to Create, Clone Repository

To make a new repository:

$ hg init <path>

To copy a repository from an existing repository:

$ hg clone <sourcePath> [<DestinationPath>]

To clone specific branch of the repository:

$ hg clone -r <barnchName> <sourcePath> [<destinationPath>]

To copy existing repository to a new locaiton:

$ hg clone . <newPath>

To get changes from server repository and update working set:

$ hg pull -u

To get changes for specific branch from server repository:

$ hg pull -r <branchName>

To see what changes will come in on a PULL command:

$ hg incoming

To publish changes to specific branch on server repository:

$ hg push -r <branchName>

To see what changes will go out on a PUSH command:

$ hg outgoing

Commands for Add, Remove, Rename, Copy Operation
Add Specific file to repository:
$ hg add <filename1, filename2, ...>

To remove file from repository but don't delete from file system:
$hg remove <filename1, filename2...>

To remove file from repository and delete from file system as well"
$ hg remove -f <filename1, filename2,...>

To add all new files and remove all deleted files from repository:
$ hg addremove

To move or rename files in the repository:
$ hg move <oldfilename> <newfilename>

To copy files in the repository:
$ hg copy <oldfilename> <newfilename>

Commands for Commit, Revert Changes
To commit Changes to server repository:
$ hg commit
$ hg push

To commit as a particular user:
$ hg commit -u <username>

To revert all changes in local repository:
$ hg revert -a

To revert specific changes in local repositroy
$ hg revert <filename1, filename2, ..>

Commands to View Changes
To view changes between working set on your local repository and repository tip:
$ hg diff

To view changes between working set on your local repository and specific revision:
$ hg diff -r <revisionNumber>

To view changes between two revisions:
$ hg diff -r <revisionNumber> -r <revisionNumber>

To check what are changes in working set:
$ hg status

To list all changesets:
$ hg log

Commands to Update Working Set
To change working set to tip:
$ hg pull
$ hg up

To change working set with discarding any current work:
$ hg update -C

To change working set to specific revision:
$ hg update -r <revisionNumber>

To change working set to specific branch:
$ hg update -r <branchName>

To see the list of branches available for merging:
$ hg heads

Commands for Handling tags and Branches
To delete a tag:
$ hg tag -r <tagtext>

To tag a revision:
$ hg tag [-r <revisionNumber] <tagtext>

To list tags:
$ hg tags

To create new branch:
$ hg branch <branchName>
$ hg commit -m "New Branch created <branchName>"

To delete a branch:
$ hg commit - - close-branch <branchName>

To see the list of branches available:
$ hg branches

For HG Diff command setting in .hgrc file in /home/username folder:

[diff]
git=1
showfunc=1
unified=8

Commands related to Patch:
Generating a patch:
$ hg diff > patchfilename

Discarding all local changes:
$ hg revert -a

Ubuntu commands

2011-02-03T19:51:00.011+08:00

I am user of Ubuntu. I am writing this post to help people like me who forgets the stuff they used before.

How to check Installed Ubuntu version and its Codename
$ lsb_release -a

How to check Disk Space:
$ df -Th

Video editor in Ubuntu:
$ avidemux

To Upgrade Ubuntu Version Online:
Press ALT+F2 , then type "update-manager -d" without quotes and hit Enter key.

Mounting ISO image as a drive on Ubuntu:
$ sudo mount -o loop ~/Desktop/filename.iso /media/cdrom0

HOWTO: Move the Minimize/Maximize/Close Buttons back the Right Side
Hit ALT - F2
Type gconf-editor
Go to the following:
apps --> metacity --> general
Find the button_layout parameter, right mouse click, and select Edit Key
Change the value to the following:
menu:minimize,maximize,close
Don't forget the colon on the left side of the text. "menu" is not necessary.

To change scree resolution from Command prompt:
$ xrandr -s 1024*768

How to change MAC address of NIC card in Ubuntu:
Type following command either in /etc/rc.local file or at command prompt:

   ifconfig eth0 down
   ifconfig eth0 hw ether NEW_MAC_ADDR
   ifconfig eth0 up

To view or cancel print Job on Unix Printer
1. Login as a user or super-user to unix computer.
2. Use "lpq -Pprinter" command to view printer queue.
   $ lpq -Ppsc011
3. Use "lprm -Pprinter [user_id] to cancel your job
   $ lprm -Ppsc011 g0xyzqwe

Public key error while trying to run update command
$ sudo apt-get update
gives following error :
W: GPG error: http://ppa.launchpad.net lucid Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY D2B5F4E7C3BB95BB

Solution: Take last 8 characters in the key and run following command

$ gpg --keyserver keyserver.ubuntu.com --recv-keys C3BB95BB
$ gpg --export -armor C3BB95BB | sudo apt-key add -

To download the key on another computer and then to run on your computer :
$ gpg --keyserver keyserver.ubuntu.com --recv-keys C3BB95BB
$ gpg --export -armor C3BB95BB > key.asc

Now Copy key.asc file on your computer and run following command:
$ cat key.asc | sudo apt-key add -

To reflect the changes done in ~/.bashrc file without restarting your Terminal window:
$ source ~/.bashrc

To get Ubuntu Command prompt:
press : Ctrl + Alt + F2 or
  Ctrl + Alt + F5

and to get back GUI screen (Xserver):
press: Ctrl + Alt + F7

What to do if ubuntu hangs? Or how to restart Xserver:
press : Ctrl + Alt + Backspace
or press: Alt + Backspace
This usually restarts xserver. You need to login again to the system.

Using Bash History Effectively:
Type the following command to get a list of all related commands with their history numbers:
$ history | grep -i "search string"
Once you've found the command you want, you can execute it specifically by its number
$ !<history_command_number>

How to prevent Auto Locking the computer Screen:
1. Open file "/etc/default/acpi-support" and comment following line:

   # Comment this out to disable screen locking on resume
   LOCK_SCREEN=true

2. Open "System > Preferences > Screen Saver" and uncheck following option:
   Lock screen when screensaver is active

How to Merge Multiple PDF files into single PDF file:
Steps:
1. Install two pacakeges GhostScript and PDFtk tools.
$ sudo apt-get install gs pdftk

2. Use following command to combine multiple files into single PDF file. The output file name is "singleCombinedPdfFile.pdf". The input file names are all files in the current directory, bcoz we used "*.pdf".

$ gs -dNOPAUSE -sDEVICE=pdfwrite -sOUTPUTFILE=singleCombinedPdfFile.pdf -dBATCH *.pdf

If you want to join PDF files in specific order then you can also use file names.

$ gs -dNOPAUSE -sDEVICE=pdfwrite -sOUTPUTFILE=singleCombinedPdfFile.pdf -dBATCH 1.pdf 2.pdf 3.pdf

Wireless Networks: "Wireless is disabled"

$ rfkill list all

You should see both the soft blocked and hard blocked as no. If either of them is yes then the connection would not be enabled. To enable type the following:

$ rfkill unblock wifi

Hard blocked: yes

This suggests that the wireless button is not switched on.

String matching in a file using (sed/grep) commands in LINUX

2010-12-14T14:21:00.001+08:00

SED command using & for match string:
The special character "&" corresponds to the pattern found.
Suppose the filename ch.txt contains following lines. And we want for each function name to add (* ) brackets .
xpcom_ProcessNextEvent(int state);
loc_wer_test(int state);
Following command converts content in ch.txt into following format and stored output in ch1.txt file.
$sed 's/[a-zA-Z]*_*[a-zA-Z]*_*[a-zA-Z]*(/int (*&)/' < ch.txt > ch1.txt
The Output of above command in ch1.txt file is as per follows:
int (*xpcom_ProcessNextEvent()int state);
int (*loc_wer_test()int state);

Now we want to swap "()" bracket with ")(" from the output of above command. Following commands does that job.

$sed 's/()/)(/' < ch1.txt > ch2.txt

int (*xpcom_ProcessNextEvent)(int state);

int (*loc_wer_test)(int state);

You could also double a pattern, e.g. the first number of a line:

$ echo "123 abc" | sed 's/[0-9]*/& &/'

123 123 abc

In above command "123 abc" was input and output was "123 123 abc".

You can have any number of "&" in the replacement string.

GREP command to copy a matching string line from a file to another file.

Suppose input_filename contains following:

//Escape() Function hook

int js_js_str_fun (...)

{

.....

}

int js_str_fun2 (...)

{

.....

}

Using following command we can extract a line with function name:

$grep "int .*(.*)" input_filename > output_filename

Above commands stores following output in output_filename file:

int js_js_str_fun (...)

int js_str_fun2 (...)

Dynamic Lib using dlopen and dlsym

2010-12-08T13:56:00.002+08:00

dlopen system call loads dynamic library and returns handle to dynamic library. If dlopen() fails it returns NULL.

dlsym takes the library handle returnd by dlopen and symbol name as input, and returns the address where that symbol is loaded. If the symbol is not found, dlsym returns NULL.

dlerror returns NULL if no errors have occurred since initialization or since it was last called. (Calling dlerror() twice consecutively, will always result in the second call returning NULL.)

#include <stdio.h>

#include <dlfcn.h>

typedef void *(*func_t)(hooks *);

int main()
{
   // declare handle variable for dynamic library
   void *handle;

   double (*cosine)(double);

   // open the dynamic library
   handle = dlopen ("libm.so", RTLD_LAZY);
   if (!handle) {
   fprintf (stderr, "%s\n", dlerror());
   exit(1);
   }

   func_t initializer_fn = (func_t)dlsym(handle, "initializer");
   if (initializer_fn) {
   // call function
(*initializer_fn)(this);
   }

   // Initialize cosine with function pointer of "cos".
   cosine = dlsym(handle, "cos");
   // call "cos" function using function pointer
   fprintf (stderr, "%f\n", (*cosine)(2.0));

   dlclose(handle);
   return 0;
} // end of main

// functions defined in library file
void initializer(hooks *libifc)
{
}

Firefox about: urls

2010-12-06T23:27:00.000+08:00

Firefox can be tweak using about:config url, that allows to change user preferences.
There are other about: urls listed below. I tested them on FF 3.5.3.

about:blank : shows a blank web page.
about:buildconfig : shows mozilla build options
about:cache
about:cache?device=memory : Lists memory cache entries
about:config : modifies user preferences.
about:credits : Shows an alphabetical list of mozilla contributors
about:logo : shows mozilla logo
about:plugins : shows all installed plugins
about:crashes : shows Firefox crash reports if any

Other about: URLs showing some messages:
about:mozilla
about:robots
about:privatebrowsing
about:sessionrestore

Firefox Extension and Web Page Script Execution

2010-12-03T17:32:00.004+08:00

To access Web page Document from Extension
  webpageDocument = top.window.content.document;

To Execute Web Page defined function from Firefox Extension

var wm = Components.classes['@mozilla.org/appshell/window-mediator;1'].getService(Components.interfaces.nsIWindowMediator);

   var currentWindow = wm.getMostRecentWindow('navigator:browser').getBrowser().contentWindow;
   var sandbox = new Components.utils.Sandbox(SandboxURL);
   // __.proto__ hack removes need of using window.a, window.alert()
   sandbox.__proto__ = currentWindow.wrappedJSObject;
   // assume web page script defines variable "a"
   var pageResult = Components.utils.evalInSandbox("alert(a);", sandbox);
   dump("\n\n Web page Function execution Result = " + pageResult);

In FF Extension to execute a Script in a Sandbox and allowing Extension function to be accessed by Sandbox object
Following code I also added to MDN [1].

// Chrome (FF Extension) custom Functions:
function sandboxAlert(msg){
   dump("\n Inside sandboxAlert");
   msg = XPCSafeJSObjectWrapper(msg);
   dump("\n msg = " + msg);
}

// variable declared in Chrome code
var tempval = 10;

function sandboxFun1(){
   return tempval;
}

   // Chrome (Firefox Extension) code

   // create sandbox enviornment to execute script.
   // SandboxURL is required for XHR requests. Same domain are allowed.
   var sandbox = new Components.utils.Sandbox(SandboxURL);

   sandbox.y = 5; // insert property 'y' with value 5 into global scope.
   var scriptText = "var x = 2 + sandboxFun1(); var k = y + 15; sandboxAlert('Testing'); x + 3";

   // // include chrome function into sandbox context.
   sandbox.importFunction(sandboxFun1);
   sandbox.importFunction(sandboxAlert);

   // // execute script into sandbox object
   var sandboxResult = Components.utils.evalInSandbox(scriptText, sandbox);

References:
1. Mozilla FF Extension evalInSandbox

Upgrading Ubuntu 10.04 (Lucid) to 10.10 (Maverick)

2010-11-30T15:24:00.000+08:00

Steps to upgrade ubuntu v10.04 to v10.10 are very simple.
Option A. Using Update Manager (System -> Adminstration -> Update Manager)
1. Start Update Manager.
2. Click on Settings button
3. Choose the Update Tab in Software Sources.
4. Select Normal releases in the Show new distribution releases: drop-down menu and click on Close button.
5. Back in Update Manager and click on Check Button.
6. Update Manager shows the new release is available. Click on Upgrade button to start new distribution upgrade on your system.

Option B.
1. Open Software Sources (System -> Adminstration -> Software Sources)
2. Choose the Update Tab in Software Sources.

3. Select Normal releases in the Show new distribution releases: drop-down menu and click on Close button.

4. Open Update Manager (System -> Adminstration -> Update Manager) and click on Check Button.

5. Update Manager shows the new release is available. Click on Upgrade button to start new distribution upgrade on your system.

Hope this simple tutorial helps!

Food to control Abdominal Fat

2010-11-15T16:34:00.000+08:00

It's better to know which food is good for healthy and provides nutrition to our body, so that we can control abdominal fat.
First I will describe vegetables that helps against fighting abdominal fat, then I will explains fruits useful for the same purpose.

A. Vegetables
1. Broccoli: Broccoli is high in vitamins C, K, and A, as well as dietary fiber. Broccoli is also an excellent source of indole-3-carbinol, a chemical which boosts DNA repair in cells and appears to block the growth of cancer cells. Broccoli is a potent modulator of the innate immune response system with anti-viral, anti-bacterial and anti-cancer activity.
2. Tomatoes: It contains lycopene, one of the most powerful natural antioxidants. Tomato consumption has been associated with decreased risk of breast cancer, head and neck cancers and might be strongly protective against neurodegenerative diseases.
3. Cauliflower: Cauliflower is low in fat, high in dietary fiber, folate, water and vitamin C, possessing a very high nutritional density. Cauliflower is a source of indole-3-carbinol, a chemical which boosts DNA repair in cells and appears to block the growth of cancer cells.
4. Cabbage: Cabbage is an excellent source of vitamin C. It also contains significant amounts of glutamine, an amino acid that has anti-inflammatory properties. Fresh cabbage juice has been shown to promote rapid healing of peptic ulcers. Cabbage can also be included in dieting programs, as it is a low calorie food.
5. Mushroom: Mushrooms are high in dietary fiber, protein, and vitamins such as thiamine, riboflavin, niacin, biotin, cobalamins, and ascorbic acid.

B. Fruits
1. Apple: Apples may reduce the risk of colon cancer, prostate cancer and lung cancer.[53] Compared to many other fruits and vegetables, apples contain relatively low amounts of vitamin C, but are a rich source of other antioxidant compounds. However, apple seeds are mildly poisonous, containing a small amount of amygdalin, a cyanogenic glycoside; it usually is not enough to be dangerous to humans, but can deter birds.
2. Pineapple: Pineapple is a good source of manganese, and also contains significant amounts of vitamin C, and vitamin B1. Consumers of pineapple have claimed that pineapple has benefits for some intestinal disorders, and others believe it serves as a pain reliever; still others claim that it helps to induce childbirth when a baby is overdue.
3. Orange: Oranges contains carbohydrates and is a good source of dietary fibers.

Above list may not be complete. But it gives some awareness to readers that use of fruits and vegetables in our daily diet not only provides nutritions but also dietary fiber to fight against abdominal fat.

Examples of Creating Map of Maps in C++ or Multilevel Maps in C++

2010-11-04T17:16:00.006+08:00

To create map of map in C++ is very simple.
Map is a sorted associative array of unique keys and associated data. The elements of the map are internally sorted from lowest to highest key value.

Example 1:
//Program to create multi level map in C++
#include <iostream>
#include <map> // header file needed for to use MAP STL

using namespace std;

int main(void)
{
//Define multilevel map. map within a map.
map<int, map<int,char> > myMap;
myMap[1][1] = 'A';
myMap[1][2] = 'B';
myMap[2][1] = 'C';
myMap[2][2] = 'D';

cout << "[1][1] = " << myMap[1][1] << endl;
cout << "[1][2] = " << myMap[1][2] << endl;
cout << "[2][1] = " << myMap[2][1] << endl;
cout << "[2][2] = " << myMap[2][2] << endl;

return 0;
}

//Save a file as multimap.cpp

To Compile and execute it on Ubuntu use following commands:
$ g++ multimap.cpp -o multimap
$ ./multimap

[1][1] = A
[1][2] = B
[2][1] = C
[2][2] = D

Example 2:

#include <iostream>
#include <string>
#include <map>

using namespace std;

typedef map<int, string> innerMap;
typedef map<double, innerMap> mainMap;

mainMap m;

void print()
{
  map<double, innerMap >::iterator it;
  map<int, string>::iterator inner_it;

  for ( it=m.begin() ; it != m.end(); it++ ) {
   cout << "\n\nNew element\n" << (*it).first << endl;
   for( inner_it=(*it).second.begin(); inner_it != (*it).second.end(); inner_it++)
   cout << (*inner_it).first << " => " << (*inner_it).second << endl;
  }
}

int main (int argc, char *argv[])
{

  // First insert an element into outermap
  m.insert (make_pair (2.4, innerMap ()));
  // Now insert elements into innermap
  m[2.4].insert (make_pair (2, "two"));
  m[2.4].insert (make_pair (5, "five"));

  // First insert an element into outermap
  m.insert (make_pair (0.6, innerMap ()));
  // Now insert elements into innermap
  m[0.6].insert (make_pair (5, "five"));
  m[0.6].insert (make_pair (1, "one"));
  m[0.6].insert (make_pair (2, "two"));

  // print elements in the mainMap
  print();

}

Output of above program (Example 2):

New element

0.6

1 => one

2 => two

5 => five

New element

2.4

2 => two

5 => five

Example 3: Uses "multimap" STL
Note that, "mutimap" STL does not support [], therefore we cannot use syntax "m[].insert( make_pair())" we used in Example 2 to insert element.

#include <iostream>
#include <string>
#include <map>

using namespace std;

typedef multimap<int, string> innerMap;
multimap<double, innerMap> mainMap;

void print()
{
  multimap<double, innerMap >::iterator it;
  multimap<int, string>::iterator inner_it;

  for ( it=mainMap.begin() ; it != mainMap.end(); it++ ) {
   cout << "\n\nNew element\n" << (*it).first << endl;
   for( inner_it=(*it).second.begin(); inner_it != (*it).second.end(); inner_it++)
   cout << (*inner_it).first << " => " << (*inner_it).second << endl;
  }
}

void insert1(multimap<double, innerMap >::iterator it)
{
  it->second.insert (make_pair (2, "two"));
  it->second.insert (make_pair (5, "five"));
  it->second.insert (make_pair (2, "two"));

}

int main (int argc, char *argv[])
{
  multimap<double, innerMap >::iterator it;

  // First insert an element into outermap
  it = mainMap.insert (make_pair (2.4, innerMap ()));
  // Now insert elements into innermap
  insert1(it);

  // First insert an element into outermap
  it = mainMap.insert (make_pair (0.6, innerMap ()));
  // Now insert elements into innermap
  it->second.insert (make_pair (5, "five"));
  it->second.insert (make_pair (1, "one"));
  it->second.insert (make_pair (2, "two"));
  it->second.insert (make_pair (5, "five"));
  it->second.insert (make_pair (5, "five"));

  // print elements in the mainMap
  print();
}

Output of the above program (Example 3):

New element
0.6
1 => one
2 => two
5 => five
5 => five
5 => five

New element
2.4
2 => two
2 => two
5 => five

Creating C++ Component / Interface using Mozilla Build System

2010-11-03T01:26:00.004+08:00

This is a step-by-step guide to create C++ Component / Interface, build using Mozilla build system, and test our component using extension and web page. I tested this on Ubuntu 10.04.

1. Create a directory with the name of your extension under "/mozilla/extensions/" directory. Use only lowercase letter. Let say we created a directory "krpextension"

2. Create "Makefile.in" in krpextension directory.
#/* Makefile.in under /mozilla/extensions/krpextension directory */
DEPTH = ../..
topsrcdir = @top_srcdir@
srcdir = @srcdir@
VPATH = @srcdir@
include $(DEPTH)/config/autoconf.mk
MODULE = krpextension
DIRS = public src
XPI_NAME = krpextension
INSTALL_EXTENSION_ID = krpextension@mycompany.com
XPI_PKGNAME = krpextension
USE_EXTENSION_MANIFEST = 1
DIST_FILES = install.rdf
include $(topsrcdir)/config/rules.mk
#/* End of Makefile */

3. Create two subdirectories in "krpextension" directory namely "public" and "src". Public subdirectory to hold our ".idl" file and src subdirectory to hold component header and implementation files. Each subdirectory in-turn contains its own makefile. Step 4 contains Makefile for "public" directory and Step 5 contains Makefile for "src" directory.

4. change directory to "public" and create "Makefile.in"
#/* Makefile.in under "/mozilla/extensions/krpextension/public" directory */

DEPTH = ../../..
topsrcdir = @top_srcdir@
srcdir = @srcdir@
VPATH = @srcdir@
include $(DEPTH)/config/autoconf.mk
MODULE = krpextension
XPIDL_MODULE = krpextension
XPI_NAME = krpextension
XPIDLSRCS = \
krpIComponent.idl \
$(NULL)
include $(topsrcdir)/config/rules.mk

#/* end of Makefile */

5. change directory to "src" and create "Makefile.in"

#/* Makefile.in under "/mozilla/extensions/krpextension/src" directory */

DEPTH = ../../..

topsrcdir = @top_srcdir@

srcdir = @srcdir@

VPATH = @srcdir@

include $(DEPTH)/config/autoconf.mk

IS_COMPONENT = 1

MODULE = krpextension

LIBRARY_NAME = krpExtension

USE_STATIC_LIBS = 1

XPI_NAME = krpextension

REQUIRES = xpcom \

string \

$(NULL)

CPPSRCS = \

krpComponent.cpp \

krpExtension.cpp \

$(NULL)

include $(topsrcdir)/config/rules.mk

EXTRA_DSO_LDOPTS += \

$(XPCOM_GLUE_LDOPTS) \

$(NSPR_LIBS) \

$(NULL)

#/* end of Makefile */

6. Change to "public" sub-directory under "/mozilla/extension/krpextension" and now we will create our own Interface definition file (.idl) in public directory, Let say "krpIComponent.idl", if you used other name than "krpIComponent" then replace each occurring of krpIComponent with your custom name of Interface.

/* krpIComponent.idl file in public subdirectory */

#include <stdio.h>

#include "nsISupports.idl"

[scriptable, uuid(1c0856f7-ed61-471e-9dac-442565a5d1d2)]

interface krpIComponent : nsISupports

{

unsigned long long Add(in unsigned long long num1, in unsigned long long num2);

unsigned long long Sub(in unsigned long long num1, in unsigned long long num2);

};

/* End of krpIComponent.idl file */

7. Change to src sub-directory under /mozilla/extension/krpextension, now we will create header and implementation file for our interface.

/* krpComponent.h header file for our component */

#ifndef __KRPCOMPONENT_H__

#define __KRPCOMPONENT_H__

#include <stdio.h>

#include <stdlib.h>

#include <unistd.h>

#include "krpIComponent.h"

#include "nsIObserverService.h"

#include "nsServiceManagerUtils.h"

#define KRPCOMPONENT_CLASSNAME "krpcomponent"

#define KRPCOMPONENT_CID \

{ /* 1c0856f7-ed61-471e-9dac-442565a5d1d2 */ \

0x1C0856F7, 0xED61, 0x471E, \

{0x9D, 0xAC, 0x44, 0x25, 0x65, 0xA5, 0xD1, 0xD2} \

}

#define KRPCOMPONENT_CONTRACTID "@mycompany.com/krpcomponent;1"

/* Header file */

class krpComponent: public krpIComponent

{

public:

NS_DECL_ISUPPORTS

NS_DECL_KRPICOMPONENT

krpComponent();

private:

~krpComponent();

protected:

};

#endif // __KRPCOMPONENT_H__

/* End of krpComponent.h header file */

/*krpComponent.cpp C++ Implementation file of our component */

#include "krpComponent.h"

/* Implementation file */

NS_IMPL_ISUPPORTS1(krpComponent, krpIComponent)

krpComponent::krpComponent()

{

/* member initializers and constructor code */

}

krpComponent::~krpComponent()

{

/* destructor code */

}

/* unsigned long long Add (in unsigned long long num1, in unsigned long long num2); */

NS_IMETHODIMP krpComponent::Add(PRUint64 num1, PRUint64 num2, PRUint64 *_retval NS_OUTPARAM)

{

*_retval = num1 + num2;

return NS_OK;

}

/* unsigned long long Sub (in unsigned long long num1, in unsigned long long num2); */

NS_IMETHODIMP krpComponent::Sub(PRUint64 num1, PRUint64 num2, PRUint64 *_retval NS_OUTPARAM)

{

if(num1 > num2)

*_retval = num1 - num2;

else

*_retval = num2 - num1;

return NS_OK;

}

/* End of implementation class of our component. */

8. Now we will create module definition file lets say "krpExtension.cpp". If you use other name then replace all occurrences of krpExtension or krpExtension.cpp with your custom name.

/*krpExtension.cpp Module definition file */

#include "nsXPCOM.h"

#include "nsIGenericFactory.h"

/**

* Components to be registered

#include "krpComponent.h"

NS_GENERIC_FACTORY_CONSTRUCTOR(krpComponent)

//----------------------------------------------------------

static const nsModuleComponentInfo components[] =

{

KRPCOMPONENT_CLASSNAME,

KRPCOMPONENT_CID,

KRPCOMPONENT_CONTRACTID,

krpComponentConstructor

};

NS_IMPL_NSGETMODULE(krpExtension, components)

/* end of krpExtension.cpp File */

9. Now to integrate our component into Extension, we will create a custom extension. In "/mozilla/extensions/krpextension" create "install.rdf" file.

/*install.rdf file contents */

<?xml version="1.0" encoding="UTF-8"?>
<RDF xmlns="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
   xmlns:em="http://www.mozilla.org/2004/em-rdf#">
  <Description about="urn:mozilla:install-manifest">
   <em:id>krpextension@mycompany.com</em:id>
   <em:version>0.1</em:version>
   <em:targetApplication>
   
   <Description>
   <em:id>{ec8030f7-c20a-464f-9b0e-13a3a9e97384}</em:id>
   <em:minVersion>3.0</em:minVersion>
   <em:maxVersion>3.6.*</em:maxVersion>
   </Description>
   </em:targetApplication>
   
   <em:name>My First Interface Extension</em:name>
   <em:description>Just an FF Interface Example.</em:description>
   <em:creator>kailas</em:creator>
   <em:homepageURL>http://kailaspatil.blogspot.com/</em:homepageURL>
  </Description>
</RDF>

/*install.rdf file ends here */

10. Now create another file "jar.mn" in "/mozilla/extensions/krpextension" directory.

/* jar.mn file contents */

krpextension.jar:

% content krpextension %content/

% locale krpextension en-US %locale/en-US/

% skin krpextension classic/1.0 %skin/

% overlay chrome://browser/content/browser.xul chrome://krpextension/content/ff-overlay.xul

content/overlay.js (chrome/content/overlay.js)

content/ff-overlay.xul (chrome/content/ff-overlay.xul)

content/ff-overlay.js (chrome/content/ff-overlay.js)

content/about.xul (chrome/content/about.xul)

locale/en-US/overlay.dtd (chrome/locale/en-US/overlay.dtd)

locale/en-US/about.dtd (chrome/locale/en-US/overlay.dtd)

locale/en-US/overlay.properties (chrome/locale/en-US/overlay.properties)

skin/overlay.css (chrome/skin/overlay.css)

/* end of jar.mn file */

The files in jar.mn reflects the XUL/JavaScript files in your custom Extension.

Use Mozilla addon to build an empty extension for Firefox, with name krpextension. Copy its "chrome" directory including subdirectories "content, locale, and skin" in chrome directory into our extension directory, i.e "/mozilla/extensions/krpextension". Note that the paths in parentheses point to actual files.

11. Now run "make" command in "mozilla/$(OBJ_DIR)$" or "make -f client.mk build" command in "/mozilla" directory. If you are using make -f client.mk build command then make sure that you setup ".mozconfig" file. Pls read an article https://developer.mozilla.org/en/build_documentation to build firefox and prerequisites required to build Firefox.

12. Our component should be build successfully, and in "Tools->Addons->Extension" Tab you should see our custom Extension.

13. To test our component with Extension and Webpage. First we will test it with Extension. Open overlay.js file in our extension folder "/mozilla/extensions/krpextension/chrome/content/overlay.js". In OnLoad: function, add following lines of code to test our component.

/*********************/

var instance = Components.classes["@mycompany.com/krpcomponent;1"].getService();

var obj =instance.QueryInterface(Components.interfaces.krpIComponent);

var result = obj.Sub(10, 5);

alert("Sub(10-5) = " + result);

/******************/

Each time firefox will start, our custom extension will start, and during initialization of our extension it will call our component method (i.e Sub(10,5) which will return result of Subtraction operation and its get displayed to user using alert box.

Now we test our component using a Web page. Create a HTML file on local system, and use following script to test our component. It should display the correct result of Addition operation.

/************************/

var res = obj1.Add(10, 5);

alert('Performing 10 + 5 = ' + res );

} catch (err) {
alert(err);
}
</script>

/************************************/

Creating C++ Component / Interface of Firefox Using Gecko-SDK

2010-11-02T00:27:00.009+08:00

This is step-by-step guide to create, build, register and use a XPCOM component/Interface on Linux (Ubuntu)

A. Creating A Component
Step 1: Download Gecko SDK (gecko-sdk-i686-pc-linux-gnu-X.X.X.X) and Extract it to local directory "gecko-sdk".
Step 2: Use a utility "uuidgen" to generate UUID for our main Interface.
Step 3: Create an Interface defination file "KFFComponent.idl", use following template, simply replace uuid(1c0856f7-ed61-471e-9dac-442565a5d1d2) with your unique uuid(your_UUID) field.

#include "nsISupports.idl"
[scriptable, uuid(1c0856f7-ed61-471e-9dac-442565a5d1d2)]
interface KFFComponent : nsISupports
{
  unsigned long long Add(in unsigned long long num1, in unsigned long long num2);
  unsigned long long Sub(in unsigned long long num1, in unsigned long long num2);
};

Step 4: Open command prompt and go to "gecko-sdk/bin" and run following command:
$ ./xpidl -m header -I_DIR_ KFFComponent.idl

Replace "_DIR_" with the full path to the "gecko-sdk/idl". Above command will create "KFFComponent.h" header file.

Step 5: Now to create typelib file, execute following command
$ ./xpidl -m typelib -I_DIR_ KFFComponent.idl
Replace "_DIR_" with the full path to the "gecko-sdk/idl". Above command will create "KFFComponent.xpt" typelib file

Step 6: Interface header file contains the template for building our component header file as well as C++ Implementation file.

Step 7: Create our own component Header file "krpComponent.h", use following contents:

#ifndef _KRP_COMPONENT_H_
#define _KRP_COMPONENT_H_
#include "KFFComponent.h"
#define KRP_COMPONENT_CONTRACTID "@mydomain.com/XPCOMSample/krpComponent;1"
#define KRP_COMPONENT_CLASSNAME "First XPCOM Sample Interface"
#define KRP_COMPONENT_CID {0x462EF8EF, 0x9A05, 0x49DE, {0x97, 0xAC, 0x82, 0x2A, 0x6C, 0x46, 0xD2, 0xDC } }

/* KRP_COMPONENT_CID = GUID (462EF8EF-9A05-49DE-97AC-822A6C46D2DC)
   Note: Replace GUID with your own GUID field
*/
/* Header file */
class krpComponent : public KFFComponent
{
public:
  NS_DECL_ISUPPORTS
  NS_DECL_KFFCOMPONENT
  krpComponent();
private:
  ~krpComponent();
protected:
  /* additional members */
};
#endif /* end of _KRP_COMPONENT_H_ */

Step 8: Create our won C++ Implementation file for the Componenet "krpComponent.cpp".

#include "krpComponent.h"
/* Implementation file */
NS_IMPL_ISUPPORTS1(krpComponent, KFFComponent)
krpComponent::krpComponent()
{
  /* member initializers and constructor code */
}
krpComponent::~krpComponent()
{
  /* destructor code */
}
/* unsigned long long Add (in unsigned long long num1, in unsigned long long num2); */
NS_IMETHODIMP krpComponent::Add(PRUint64 num1, PRUint64 num2, PRUint64 *_retval)
{
  *_retval = num1 + num2;
  return NS_OK;
}
/* unsigned long long Sub (in unsigned long long num1, in unsigned long long num2); */
NS_IMETHODIMP krpComponent::Sub(PRUint64 num1, PRUint64 num2, PRUint64 *_retval)
{
  *_retval = num1 - num2;
  return NS_OK;
}
/* End of implementation class template. */

Step 9: Create our own Module definition file "krpComponentModule.cpp".

// This is necessary file to include Mozill Generic definations

#include "nsIGenericFactory.h"

//My Component Header File

#include "krpComponent.h"

NS_GENERIC_FACTORY_CONSTRUCTOR(krpComponent)

static nsModuleComponentInfo components[] =

{

KRP_COMPONENT_CLASSNAME,

KRP_COMPONENT_CID,

KRP_COMPONENT_CONTRACTID,

krpComponentConstructor,

}

};

NS_IMPL_NSGETMODULE("krpComponentsModule", components)

B: Building our Component / Interface

Step 1: Create Makefile or use your own template

CXX = c++

CPPFLAGS += -fno-rtti \

-fno-exceptions \

-shared

# Change this to point at your Gecko SDK directory.

GECKO_SDK_PATH = /home/username/cprogs/gecko-sdk

# GCC only define which allows us to not have to #include mozilla-config

# in every .cpp file. If your not using GCC remove this line and add

# #include "mozilla-config.h" to each of your .cpp files.

GECKO_CONFIG_INCLUDE = -include mozilla-config.h

GECKO_DEFINES = -DXPCOM_GLUE

GECKO_INCLUDES = -I $(GECKO_SDK_PATH)/include

GECKO_LDFLAGS = -L $(GECKO_SDK_PATH)/lib -lxpcomglue \

-lnspr4 \

-lplds4

FILES = krpComponent.cpp krpComponentModule.cpp

TARGET = krpComponent.so

build:

$(CXX) -Wall -Os -o $(TARGET) $(GECKO_CONFIG_INCLUDE) $(GECKO_DEFINES) $(GECKO_INCLUDES) $(GECKO_LDFLAGS) $(CPPFLAGS) $(CXXFLAGS) $(FILES)

chmod +x $(TARGET)

strip $(TARGET)

clean:

rm $(TARGET)

Step 2: Run "make" command, and it "krpComponent.so" file will be created.

C: Registering the Component

Step 1: Copy krpComponent.so and KFFComponent.xpt file to "~/.mozilla/component" directory

Step 2: use command "regxpcom" to register component

$ ./regxpcom -x _DIR_PATH_OF_COMPONENT_

Replace _DIR_PATH_OF_COMPONENT with the path of component (krpComponent.so)

Step 3: Restart Mozilla.

D: Testing Component
You can either use Extension or HTML page to test our new Firefox C++ Component.
HTML Code of "TestComponent.html" page is as follows

<script>
try {
netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");
const cid = "@mydomain.com/XPCOMSample/krpComponent;1";
var obj = Components.classes[cid].createInstance();
var obj1 = obj.QueryInterface(Components.interfaces.KFFComponent);

var res = obj1.Sub(10, 5);

alert('Performing 10 - 5 = ' + res );

} catch (err) {
alert(err);
}

</script>

References:
1. XPCOM GUIDE - http://www.iosart.com/firefox/xpcom/
2. Firefox Component - http://www.codeproject.com/KB/library/firefox_component.aspx

Narcissus/Zaphod JavaScript Research VM for Firefox

2010-10-21T09:41:00.000+08:00

Narcissus is a JavaScript virtual machine written in JavaScript. Firefox extension Zaphod allows using Narcissus as the default JavaScript engine in Firefox.
Developers can write scripts specifically for the Narcissus engine (by specifying script tags with a type of "application/narcissus"), or they can replace SpiderMonkey with Narcissus as the default engine.

References:
More info about Zaphod
Example Pages

How to use Huawei E1550 USB Modem On Ubuntu 10.04

2010-10-09T14:10:00.001+08:00

I am using StarHub MaxMobile SurfLite plan. A USB modem device that comes with the plan is supported on Mac and Windows OS bydefault.

I use Ubuntu and like to work on ubuntu than windows. It was very troublesome for me to change to windows whenever I needed Internet access. I was fed up with doing back and forth in windows and ubuntu OS. And desperately wanted to use my USB stick on ubuntu.

My previous USB stick was ZTE MF628. And I don't know how to use it on ubuntu. If anyone knows it, I will appreciate if you post how to make it work on ubuntu.

When I renewed my contract with StarHub, I got new USB stick Huawei E1550 that worked on ubuntu without any hurdles.

Step by Step guide to use Huawei E1550 USB stick on Ubuntu:

1. Plug in Huawei E1550 USB modem to USB port. You can notice its icon is loaded on Desktop.

2. Type following command at command prompt:

$ gksu gedit /etc/udev/rules.d/15-huawei-e1550.rules

3. It will open gedit. Type following lines in it and then save it and close the file.

SUBSYSTEM=="usb",

SYSFS{idProduct}=="1446",

SYSFS{idVendor}=="12d1",

RUN+="/lib/udev/modem-modeswitch --vendor 0x12d1 --product 0x1446 --type option-zerocd"

4. Restart the computer. After restart click on "Network connection" icon in the top panel. You will see new menu item under "Mobile Broadband" category.

5. Click on that new entry. It will open a New Mobile Broadband Connections dialog. Click Forward to continue.

6. Select you country (Singapore in my case) and click Forward. Then select service provider from the list and click forward. Then choose your Billing plan and click Forward. Then finally Click on Apply to save setting.

It will connect you to the Internet. Enjoy, hurdle free Internet connectivity on ubuntu using USB Modem (Huawei E1550).

Mac OS theme on Ubuntu 10.04 (Lucid)

2010-08-18T11:30:00.001+08:00

Installing Mac OS theme on Ubuntu 10.04 (Lucid) is easy and straightforward.

Step 1: Install Gstyle (Gstyle is a full Gnome Theme Manager)

sudo add-apt-repository ppa:s-lagui/ppa

sudo apt-get update

sudo apt-get install gstyle

Step 2: Once it is installed successfully. Launch Gstyle application (System -> Preferences - > Gstyle).

Step 3: Click on Download button and then Click on Refresh button. Select Mac4Lin theme from the list.

Step 4: Then in each category option in the left panel of Gstyle, select Mac4Lin. I choose Mac4Lin Aqua.

Step 5A: Now to Configure Global Menu (Top panel bar). Perform following steps:

sudo add-apt-repository ppa:globalmenu-team

sudo apt-get update && sudo apt-get install gnome-globalmenu

killall gnome-panel

Step 5B: Once done, remove all stuffs from top left panel (Right click on the panel and select “Remove from Panel”). Right click on the top panel and select Add to Panel. Select Main Menu, follow by the Global Menu Panel Applet. Close the window. Now move the two items (right click and select Move) to the left hand corner and make sure they are side by side.

Step 6A: Now to configure Dock (Bottom panel bar). Perform following Steps:

sudo apt-get install cairo-dock

There are lot of dock application, but I found this one is easy to use.

Step 6B: Before you launch the Cairo dock application, remove the bottom panel (right click at the bottom panel and select Delete This Panel). Cairo dock needs a compositing manager to work, so make sure that your system support Compiz before launching the app. Launch Cairo dock (Menu -> Accessories -> Cairo Dock). Make sure to set it to launch everytime you startup your computer.

Only if your system does not support Compiz: You can activate the in-built metacity compositing manager with the command:

gconftool-2 --type boolean --set /apps/metacity/general/compositing_manager TRUE

To change the logo in the panel bar with apple logo:
1. Download apple logo from google.
2. Then go to /home/urprofilename/.icons/Mac4Lin_Icons_v1.0/scalable/places folder. Check the resolution of distributor logo.png file. It may be 78 * 96. Now rescale the image you downloaded into 78 *96 or 96*96 size.
3. Then replace distributor-logo.png, gnome-main-menu.png, main-menu.png, and start-here.png with the apple logo file.
4. Open the terminal window and type killall gnome-panel to restart the gnome-panel. Now you should see your new icon.

How to create Patch on Liunx?

2010-08-16T11:33:00.003+08:00

In this post I will explain how to create a patch file and how to apply patch.
I only know the basic stuff. Therefore, if you want to know more then please use command man diff at command prompt to explore other possible options.

How to Create a Patch File?
Patch file is a readable text file which is created using diff command.
To create a patch of entire source folder including its sub directories, do as follows:

$ diff -rauB  old_dir new_dir > patchfile_name

  options -rauB mean:
  r -> recursive (multiple levels dir)
  a -> treat all files as text
  u -> Output NUM (default 3) lines of unified context
  B -> B is to ignore Blank Lines

Blank lines are usually useless in the patch file. Therefore I used B option, however you are free to tune your patch file according to your choice.
old_dir is the original source code directory, new_dir is the new version of source code and patchfile_name is the name of the patch file. You can give any name to your patch file.

How to Apply Patch to your Source Code?
Suppose you have got a patch file and you want to apply that patch to the version of your source code.
It is not necessary but I recommend to do a dry-run test first.

To do a dry run:
$ patch --dry-run -p1 -i patchfile_name

-i : Read the patch from patchfile.
-pnum : Strip the smallest prefix containing num leading slashes from each
   file name found in the patch file. A sequence of one or more adjacent
   slashes is counted as a single slash. This controls how file
   names found in the patch file are treated, in case you keep your
   files in a different directory than the person who sent out the
   patch.

If there is no failure then you can apply patch to your source code:
$ patch -p1 -i patchfile_name

I hope this post will help you to generate patch from your source code and apply patch to your source code.

How to Build Lobo browser on Ubuntu 10.04

2010-08-14T19:21:00.004+08:00

Prerequisites:

1. Eclipse SDK for Java.

2. IzPack (http://izpack.org/). Download cross platform installation jar file.

Steps:

1. Create a sudirectory "XAMJ_Project" in /opt folder. In linux, /opt belongs to root user so you may need to change the owner of /opt folder, so that write operation will be allowed.

2. Install IzPack in "/opt/IzPack". for installation of IzPack at command prompt run the command: java -jar IzPack-install-x.x.x.jar.

3. Open Eclipse and change workspace path to "/opt/XAMJ_Project".

4. Now choose the Project Explorer (Window->Show View -> Project Explorer).

5. Right click in project explorer and select New -> Project -> CVS - > Project from CVS.

6. When prompted for server details fill out the server details as given in step 3 of Lobo Eclipse build instruction page.

Host: xamj.cvs.sourceforge.net

Repository path: /cvsroot/xamj

User: anonymous

Password: [leave blank]

Connection type: pserver

7. Next, select "Use an existing module" option.

8. Then select 8 modules from the XAMJ_Project folder for basic web browser build. You can choose all modules. eight modules I choose were as follows:

Common
cssparser
HTML_Renderer
Platform_Public_API
Platform_Core
Primary_Extension
XAMJ_Build
IzPack_RegistryPanel

9. Next select the version of repository and check out.

10. Now right click on "IzPack_RegistryPanel" select "Properties" . Then select "Java Build Path". select the "Libraries" tab.

11. If you see cross for some libraries then its bcoz of the wrong path. As we have already installed IzPack, search for files in /opt/Izpack/lib or /opt/IzPack/bin/Panel, and correct the paths of library files.

12. Now configure "Run Configuration" for your Java Application project. Please see the README.txt file in Platform_Core for instructions, and set VM Variable and Program Variable in the Arguments tab according to the README.txt file. Also set the Project name and Main class name in the Main tab. The name of the main class is org.lobobrowser.main.EntryPoint .

13. Now apply your setting and run the project. It should work. If it doesn't then right click on IzPack_Registry Panel and add libraies: xpp3-1.1.3.4.M.jar, and cobra-no-commons.jar.zip. You can search and download these libraries if they are not present.

What is Really Simple Syndication( RSS)?

2010-07-30T19:45:00.004+08:00

Really Simple Syndication (RSS) is a way to subscribe to a source of information, such as a Web site.

RSS works by having the website author maintain a list of notifications on their website in a standard way. This list of notifications is called an "RSS Feed". Many Blog services automatically create RSS Feeds. For Websites, RSS Feeds can be created manually or with software(such as Software Garden, Inc.'s ListGarden).

The RSS Feed that is created is an XML file that lives on a Webserver. Once RSS feed is ready on web server, RSS Feeds waits for an RSS Reader to subscribe to them. The RSS Feed Reader reads the RSS Feed file and displays it. That is, the RSS Reader displays only new items from the RSS Feed. An RSS Feed Reader reads the RSS feed file, finds what is new, converts it to HTML, and displays it.

Spider-monkey Internals

2010-05-24T13:58:00.000+08:00

SpiderMonkey Internals

The JavaScript engine compiles and executes scripts containing JavaScript statements and functions. The engine handles memory allocation for the objects needed to execute scripts, and it cleans up—garbage collects—objects it no longer needs.

The word JavaScript may bring to mind features such as event handlers (like onclick), DOMobjects, window.open, and XMLHttpRequest. But in Mozilla, all of these features are actually provided by other components, not the SpiderMonkey engine itself. SpiderMonkey provides a few core JavaScript data types—numbers, strings, Arrays, Objects, and so on—and a few methods, such as Array.push. It also makes it easy for each application to expose some of its own objects and functions to JavaScript code. Browsers expose DOM objects.

Spidermonkey includes/implemented JavaScript functions such as eval(), charAt(), escape(), unescape(), encodeURI(), decodeURI(), etc.

JavaScript Event Handlers (like onClick) are implemented in the content/event/ module in Firefox. The file use to handle events is content/event/src/nsEventStateManager.cpp.

Window.open is implemented in the dom/ module. The file which implemented native function for window.open is dom/src/base/nsGlobalWindow::OpenJS() in Firefox. window object is not standardized in DOM specifications, therefore, it has vendor specific implementation of it.

XMLHttpRequest() is implemented in the content/base/ module in Firefox. The file is content/base/src/nsXMLHttpRequest.cpp implementing XHR request.

C/C++ code accesses SpiderMonkey via the JSAPI, by including the header "jsapi.h". The JSAPI provides functions for setting up the JavaScript runtime, compiling and executing scripts, creating and examining JavaScript data structures, handling errors, enabling security checks, and debugging scripts.

In order to run any JavaScript code in SpiderMonkey, an application must have three key elements: a JSRuntime, a JSContext, and a global object.

Runtimes. A JSRuntime, or runtime, is the space in which the JavaScript variables, objects, scripts, and contexts used by your application are allocated. Every JSContext and every object in an application lives within a JSRuntime. They cannot travel to other runtimes or be shared across runtimes. Most applications only need one runtime.

A program typically has only one JSRuntime, even if it has many threads.

Contexts. A JSContext, or context, is like a little machine that can do many things involving JavaScript code and objects. It can compile and execute scripts, get and set object properties, call JavaScript functions, convert JavaScript data from one type to another, create objects, and so on. Almost all JSAPI functions require a JSContext * as the first argument.

Global objects. Lastly, the global object contains all the classes, functions, and variables that are available for JavaScript code to use. Whenever JavaScript code does something like window.open("http://www.mozilla.org/"), it is accessing a global property, in this case window. JSAPI applications have full control over what global properties scripts can see. The application starts out by creating an object and populating it with the standard JavaScript classes, like Array and Object. Then it adds whatever custom classes, functions, and variables (like window) the application wants to provide; see Custom objects below. Each time the application runs a JS script (using, for example, JS_EvaluateScript), it provides the global object for that script to use. As the script runs, it can create global functions and variables of its own. All of these functions, classes, and variables are stored as properties of the global object.

References:

1. https://developer.mozilla.org/En/SpiderMonkey/JSAPI_User_Guide#JSAPI_basics

2. https://developer.mozilla.org/En/JSRuntime

V8 Build Error

2010-05-05T12:02:00.006+08:00

Hi,

I downloaded v8 and followed the build instruction given at http://code.google.com/apis/v8/build.html#build .

However, When I executed the command "scons" (without quotes) it shown following errors on my machine.

cc1plus: error: dereferencing pointer 'dest' does break strict-aliasing rules

src/api.cc:3495: note: initialized from here

scons: *** [obj/release/api.o] Error 1

scons: building terminated because of errors.

This is bcoz warnings are considered as errors by the compiler.

To solve this problem,

open "SConstruct" file in the source directory of v8 and look for "V8_EXTRA_FLAGS"

Then comment the line (use # to comment line) '-Werror' in

gcc:{

all:{

WARNINGFLAGS: [

]

After doing this, I was able to build it. However, I was not able to embed v8 in C++ application.

The reason was, I was running ubuntu x64 bit OS and V8 build is of 32-bit.

I ran following command to build 64-bit libaray of V8.

$ scons mode=debug arch=x64

Where mode=debug to build DEBUG version instead of by default release version. And arch=x64 to build 64-bit version instead of by-default 32-bit version.

Measure CPU usage time by Thread

2010-04-11T15:18:00.000+08:00

   On Linux there are two commands you can use to measure CPU usage time of a thread in a multi threaded application. Those commands are getrusage() and clock_gettime(). You can sue same commands to measure CPU time consumed by process.

Sample program to measure CPU time in a thread is given below:

#include
#include
#include

   int kResult = 0;
   struct rusage start, end;
   struct timeval timeS, timeE;
   double t= 0.0, time= 0.0;

   struct timespec st, endt;
   double t1= 0.0, time1= 0.0;

   // measure CPU time
      kResult = getrusage(RUSAGE_THREAD, &start);

   if (kResult == -1)
   fprintf(stderr, "\n\n Error in getrusage command");

   timeS = start.ru_stime; // system time
   t = (double)timeS.tv_sec + (double) timeS.tv_usec / 1000000.0;
   timeS = start.ru_utime; // user time
   t = t + (double)timeS.tv_sec + (double) timeS.tv_usec / 1000000.0;

   kResult = clock_gettime(CLOCK_THREAD_CPUTIME_ID, &st);
   if (kResult == -1)
   fprintf(stderr, "\n\n Error in clock_gettime command");

   t1 = (double) (st.tv_sec * 1000000.0 )+ (double) st.tv_nsec / 1000.0 ;


   // Do some operation to consume CPU

  // measure CPU time

kResult = getrusage(RUSAGE_THREAD, &end);

   if (kResult == -1)
   fprintf(stderr, "\n\n Error in getrusage command");

   timeE = end.ru_stime; // system time
   time = (double)timeE.tv_sec + (double) timeE.tv_usec / 1000000.0;
   timeE = end.ru_utime; // user time
   time = time + (double)timeE.tv_sec + (double) timeE.tv_usec / 1000000.0;

   time = time - t;
   fprintf(stderr,"\n\n Total CPU usage time using 'getrusage' = %.12lf\n\n", time);

   kResult = clock_gettime(CLOCK_THREAD_CPUTIME_ID, &endt);
   if (kResult == -1)
   fprintf(stderr, "\n\n Error in clock_gettime command");

   time1 = (double) (endt.tv_sec * 1000000.0)+ (double) endt.tv_nsec / 1000.0 ;
   time1 = (time1 - t1) / 1000000.0;

   fprintf(stderr,"\n\n Total CPU usage time using 'clock_gettime' = %.12lf\n\n", time1);

Note: clock_gettime will generate error if you will not provide -lrt library to linker.

To remove old kernel from Ubuntu

2010-03-19T13:32:00.001+08:00

To remove old kernels from ubuntu OS:

First check the current kernel version:
$ uname -r

Do not remove current version.

To remove old kernel version use command:
$sudo apt-get purge linux-image-2.6.XX-XX-generic

Then remove header of that version:
$sudo apt-get purge linux-headers-2.6.XX-XX

Cannot Update Ubuntu

2010-03-16T17:15:00.000+08:00

Recently, When I was trying to update ubuntu, I was getting following error message:

E: Could not get lock /var/lib/apt/lists/lock - open (11 Resource temporarily unavailable)

E: Unable to lock the list directory

After searching on Ubuntu forums I found the solution to solve this Problem.

Use following command to see is their any synaptic pkg manager running?

$ ps -e | grep apt

If yes, then kill all those processes using

$ sudo kill -9 processID

Then remove lock file from ur system:

$ sudo rm /var/lib/apt/lists/lock

Now try to update ur system. It should work. Atleast it worked for me.

DOT Graphs

2010-03-16T16:35:00.002+08:00

DOT (filename.dot) is a file format to draw graphs including directed graphs.
DOT writes graphs in .ps, .pdf, .gif, .png formats.

For example,

$ dot -Tps src.dot -o dest.ps

$ dot -Tpdf src.dot -o dest.pdf

Dot file format is as follows:

digraph graphName {
"Node 1" -> "Node 2" ;
"Node 1" -> "Node 2" -> "Node 3";
}

Each line is terminated by semicolon (;), and arrow (->) is used to show directed arc.

digraph means directed graph whereas graph means undirected graph.

Within a main graph a subgraph define a subset of graph.
For example,
digraph GraphName {
"Node 1" -> "Node 2";
subgraph SubGraphName{
   "Node 3" -> "Node 1";
   "Node 4" -> Node 3";
  }
}

JavaScript Injection

2010-03-02T19:19:00.001+08:00

JavaScript Injection is a technique that allows you alter the content of current web page without actually leaving the current web page. It is extremely useful when you want to spoof the contents that are sent to server using Forms.

Basics of JS Injection:

JS injection means inserting or executing a script. You can execute a script from the URL bar of the web page which you want to alter. To execute JS code, you must first clear the URL bar (Note: Don't press enter yet), that is, no http:// or anything else.

Javascript can be executed from URL using javascript: protocol.

Try following code in the URL bar of the web page to display your message.

javascript:alert("Hello World!");

If you saw a window pop-up and saying Hello World, then congrats, you successfully did a JS injection test.

Cookie Editing:

This time we will try penetrate one level deeper and we will try to modify server state.

One of the mechanism used to represent server state is using Cookies. Server identifies client state and authorization using Cookies. Therefore, it is worth to learn cookie alteration using JS injection technique.

To check the cookies set by web site, use following script at URL bar:

javascript:alert(document.cookie);

Above script will show you cookies set by web site. To modify any key=value pair, use following syntax:

javascript:void(document.cookie="Key=Value");

Above command can either alter existing Key=Value pair or add new Key=Value pair if it doesn't exists. To edit or alter information we use void( ) function of JavaScript.

For example, server set Authorization=no in Cookie and you want to modify this Key=value pair. Then you can use script given below:

javascript:void(document.cookie="Autorization=yes");

It is also useful to try an alert(document.cookie); script at the end of the same line to see what effect your altering had.

Form Modifications:

One way to edit values sent to web server from client using a Form is to store a web page on a local disk and modify its Form field values with whatever values you want and then submit the form to the server.

For example:

Following HTML code snippet shows that hidden field is submitted when a submit button is clicked on Form. If we want to modify email address to get data sent by email to webmaster.

<form action="/missions/basic/process.php" method="post">

<input type="hidden" name="to" value="webmaster@mywebsite.com" />

<input type="submit" value="Click to Submit" />

</form>

First, we need to store this web page on local disk, and then modify it as shown below.

<form action="http://mywebsite.com/missions/basic/process.php" method="post">

<input type="hidden" name="to" value="altered@emailaddress.com" />

<input type="submit" value="Click to Submit" />

</form>

However, sometimes the website checks to see if you actually submitted it from the website or not. To get around this, we can just edit the form using from javascript Injection.

Every form on a given webpage (unless named otherwise) is stored in the forms[x] array... where "x" is the number, in order from top to bottom, of all the forms in a page. Note that the forms start at 0, so the first form on the page would actually be 0, and the second would be 1 and so on.

Lets consider our previous form example:

<form action="/missions/basic/process.php" method="post">

<input type="hidden" name="to" value="webmaster@mywebsite.com" />

<input type="submit" value="Click to Submit" />

</form>

Note:Since this is the first form on the page, it is forms[0].

To check the value using JS, use following command:
      javascript:alert(document.forms[0].to.value)

In this case, It would pop up an alert that says "webmaster@mywebsite.com"

So here's how to Inject your email into it. You can use the same technique as shown earlier in the cookies editing :
   javascript:void(document.forms[0].to.value="altered@emailaddress.com");

Above script would change email address to altered@emailaddress.com. You can use alert( ) JavaScript function to check your work.

These are the most basic things you need to know about JS injection and useful in many cases.

How Download accelerator Works?

2010-02-23T11:22:00.000+08:00

In this post I will explain the basic principle of Download accelerators (such as DAP, wxDownload Fast, etc) used to download files.

How it speeds up the downloading.

First Let me explain the difference between normal downloading of a file and downloading of a file using download accelerator. If you use regular browser to download a file then it creates only one connection with the server to download the file, whereas if download accelerators is used to download file then it creates multiple connection with the server and downloads a file in chunks and upon completion of download it joins those chunks. Number of chunks created by download accelerators is depend on its configuration. I used wxDownload Fast and configured it to create 3 chunks of a file. That is, it creates 3 connections with the server to download any file.

Lets consider an example.

I used wxDownload Fast as download accelerator and downloaded a file ymsgr8us.exe (Yahoo messenger) which is of size 9.9 MB.
The initial request sent by wxDownload Fast to server was ordinary request to retrieve file, as given below:

Hypertext Transfer Protocol
GET /dl/9073e1f8a8d00eb735874cd9d3b6769c/4b824b4c/30%2Fymsgr8us.exe HTTP/1.1\r\n
Request Method: GET
Request Version: HTTP/1.1
HOST: us.download.soft32.com\r\n
User-Agent: wxDownload Fast\r\n
Range: bytes=0-\r\n

In HTTP response, from Content-Length header field wxDownload Fast learned the actual size of file. Once the file size is know to wxDownload Fast (in general, to download accelerators), depending on number of connection (chunks) to create it decides how big should be the chunk size. In our case, I configured it to create three chunks, therefore, it divides Content-Length value by 3 to create three chunks.

Then it sends another HTTP request to the server, by creating another connection. The HTTP request made by wxDownload to the server was as follows:

Hypertext Transfer Protocol
GET /download/63-164279-1/ymsgr8us.exe HTTP/1.1\r\n
Request Method: GET
Request URI: /download/63-164279-1/ymsgr8us.exe
Request Version: HTTP/1.1
HOST: www.soft32.com\r\n
User-Agent: wxDownload Fast\r\n
Range: bytes=3474600-\r\n

Note the Range field in HTTP request. The range header field was
Range: bytes=3474600-

It instructs the server to return a file from 3474600th byte onwards. Although, download manager requested for entire file in its first connection, it would however terminate that connection as soon as it will receive upto bytes 3474599. Hence it would not wast resources and download duplicate byte streams.

As now you can image what would be the third HTTP request. It is given below. observe the Range HTTP header field.

Hypertext Transfer Protocol
GET /download/63-164279-1/ymsgr8us.exe HTTP/1.1\r\n
Request Method: GET
Request URI: /download/63-164279-1/ymsgr8us.exe
Request Version: HTTP/1.1
HOST: www.soft32.com\r\n
User-Agent: wxDownload Fast\r\n
Range: bytes=6949200-\r\n

This is the basic principle followed by download accelerators (such as wxDownload Fast, etc) to download file quickly than normal browser download.

Heritrix and HTMLUnit

2010-02-19T13:37:00.022+08:00

Hi folks, In this post I will explain how to build Heritrix from its source code and how to Integrate HTMLUnit into Heritrix.

First question comes to mind is, What is Heritrix? and why do we need HTMLUnit to Integrate into Heritrix?

Well, Heritrix is a open-source, Web crawler. Heritrix does not include web page level DOM model and JavaScript Interpreter. Therefore, if you want to crawl the web to look for malicious scripts or obfuscated JS, then you need a JS interpreter. Hence. HTMLUnit comes into play. HTMLUnit is a headless browser, which has got JS interpreter.

Steps to Build Heritrix:

Download latest version of JDK rpm from sun website and install it.
Set JAVA_HOME and PATH environment to .bashrc file (~/.bashrc)

     export JAVA_HOME=/usr/java/jdk1.6.x.x
     export PATH=$JAVA_HOME/bin:$PATH
   Now JDK is ready to be used by Heritirx and Maven
   3. We need maven 1.0.2 to build heritix. Note: We need src of heritix so that we can modify it in future. Therefore do not use heritix binaries available on Ineternet. Build heritirx from src. Also Note the version of maven. it is very very important. Do not try with latest version of maven. It may not work.
   4. Download binary of maven 1.0.2 and extract it somewhere on disk. Now set MAVEN_HOME
   environment for it as mention below.
   Edit (/etc/profile) file to insert following lines before unset i and unset pathmunge commands at the end of file.
   export MAVEN_HOME=/path_of_Maven_directory
   pathmunge $MAVEN_HOME/bin before

     Now logout and login again to reflect environment variable changes done above to be get reflected.

   5. Run maven -v command to test maven is running properly.
   6. Run maven jar command. this will create /root/.maven/repository directory.
   7. Now go into heritirx directory and run command maven dist
   8. This will create subdirectory target, and many other subdirectories inside target directory.
   target/distribution directory holds heritirx build version.
   It there is failure due to any dependency jar file then download that file from Internet and store it in either /root/.maven/cache or /root/.maven/repository/.../jar/ directory.
   9. Heritirx is build Successfully. Extract build version and test heritirx.
  10. Launch heritrix by using command:
     $ HERITRIX_HOME/bin/heritrix --admin=LOGIN:PASSWORD
   where $HERITRIX_HOME is the location of your untarred heritrix.?.?.?.tar.gz.

Integrating HTMLUNIT into Heritrix:

This is little bit tricky. You are at this point means you already have heritrix, sun JDK and maven.

Follow the steps given below:
Step 1: Download HTMLUnit (I used HTMLUnit 2.5). We don't need source code of HTMLUnit therefore download binary of HTMLUnit. We only need its JAR files.

Step 2: Copy all JAR files in HTMLUnit into lib sub-directory of heritrix folder. Do not replace files, which are already there, if you replace them, then you need to modify project.properties file. Only add those files which are not there.

Step 3: Edit project.xml file in heritrix directory. Bcoz we want to tell heritrix where HTMLUnit classes can be found. Add tag for each JAR file of HTMLUnit.

Sample of dependency tag is given below:
   <dependency>
   <id>htmlunit</id>
   <version>2.5</version>
     <url>http://htmlunit.sourceforge.net/ </url>
   <properties>
     <war.bundle>true </war.bundle >
   <ear.bundle>true</ear.bundle>
   <ear.bundle.dir>APP-INF/lib</ear.bundle.dir>
   <description>
   Use to handle JS obfuscation. It is a headless browser.
   </description>
   <license>Apache 2.0
   http://www.apache.org/licenses/LICENSE-2.0 </license>
   </properties>
   </dependency>
Add this dependency tag for all JAR files of HTMLUnit.

Step 4: Edit project.properties file in heritirx directory to instruct maven that, do not try to download those dependency files from Internet, rather look into local directory. Syntax to do this can be easily found in project. properties file, simply make use of it.

For example:
   maven.jar.htmlunit = ${basedir}/lib/htmlunit-2.5.jar

Add a entry for each JAR file (that is, each dependency entry done in Step 3 ) of HTMLUnit.

Step 5. Done. Now build Heritrix again.

How to Reset Sansa Mp3 Player when it Freezes

2009-11-16T14:56:00.003+08:00

I got 2GB Sansa Mp3 player, as a complementary accessaries with Nikon CoolPix L20.
My Mp3 Player freezes, when I am charging it and accedentally unplug it, witout ejecting it. Some time it hungs while plying Song.

After couple of try I found few solutions that can reboot Sansa MP3 Player, and it works with my Sansa MP3 player.

1. Turn ON the Hold switch. (move hold button to Hold Position)
2. Press and hold Menu and Rec buttons at the same time until the Sansa MP3 player reboots.

Alternate Solution is :
Hold Menu (Power) button for atleast 20 seconds. Sometimes this trick works.

Hard Reset
To perform hardware reset on the Sansa Express, press and hold the "Select" button while pressing the Volume UP (+) buttons simultaneously once.

How to use ClamAv Antivirus on Ubuntu?

2009-11-16T14:28:00.008+08:00

This tutorial will explain you, how to Install and use ClamAv Antivirus on Ubuntu. ClamAv antivirus is a free antivirus, available in ubuntu repository.

To install ClamAv antivirus and GUI to manage it on ubuntu 9.10, use Ubuntu Software Center to install "KlamAV". KlamAV is an anti-virus manager for the KDE desktop. It allows virus scanning, software/update databases, etc.

I am using "KlamAV" as a GUI tool to manage and use ClamAV antivirus. You can also use "clamtk" as a GUI to use CLAMAV in Gnome or KDE.
Use following command to install "clamtk"
sudo apt-get install clamtk

Once it is installed on your machine, then install anti-virus updater, so that you can get latest update of ClamAV from Internet.

sudo apt-get install clamav-freshclam

Use command "sudo freshclam" to update ClamAV database.

To check the version of ClamAV use following Command:
clamdscan -V

To do command line scanning:
1. To scan specific folder:
   sudo clamscan -r /home/directoryname/subdirectory
     Above command will display the name of files in subdirectory on the screen. You can use -i parameter to display only infected files.
2. To scan all files on your computer
      sudo clamscan -r   --bell -i   /
     Above command will display only infected files and will bell the ring when virus found.
3. To remove infected file from your computer
   sudo clamscan -r -remove /

Lambda Calculus Type inference examples

2009-11-13T15:41:00.011+08:00

1] \ x -> x
Above function takes one argument and returns the same argument as result, therefore type of argument and return value must be same.

type: a - > a

2] \ x y -> x
Above function takes two arguments and returns the first argument as result, therefore type of first argument and return value must be same.

type: a -> b -> a

3] \f g -> g (f g)
Above function takes two parameter f and g.

To solve this, my algorithm is as follows:

First look at function body from right-to-left. Function body is g(f g)

Assume type of g is t1. That is, ( g = t1).

Now, take next variable from function body, which is f. f is a function that take g as argument and return value of any type, say return type is a. So far, there is no restriction of return value of f. assume type of f is t1-> a. That is, (f = t1 -> a).

Now, take next variable, which is g. g is a function that takes return value of function f as a argument (a), and returns value of any type, say return type is b. So far there is no restriction of type of value return by g. But we already assume g is of type t1. Now, we found that g is function so, t1 is a - > b.
That is, (g = g = t1 = a -> b).

Now replace t1 in f with (a -> b). So f becomes f = (a -> b ) -> a

we have done with function body. Now look at function declaration syntax. It takes two arguments f and g, and f is first argument, g is second argument, and return value is of same type of return value of g.

So type of function \f g -> g (f g) is as follows:

((a -> b) -> a) -> ( a -> b) -> b

4] \ x f g -> f g (x g)

Above function accepts three arguments x, f and g.
Assume g is of type a. that is, (g = a).
Now, x takes g as a argument and returns any type of value. So far there is no restriction on type of value returned by x, say return type of value is b.
Therefore, x = a -> b

Now, f takes two argument g and return type of x. Return type of f has no restriction, so say it is of type c.
Therefore, f = a -> b -> c

(Note: For simplicity as assume g as a variable. And is of type a. However, you can consider it g as a function then you have to unify a = d->e and replace all occurrences of a with d->e)

Return type of f is the return type of this function.

Now look at function definition and arrange its type accordingly.

\ x f g -> f g (x g) type is as follows:

(a -> b) -> (a -> b -> c) -> a - > c

5] \ f g x -> f ( g x)

Above function takes three arguments, namely, f , g ,and x.

Assume x is of type a., That is ( x = a)

Now g takes x as argument and returns a value. Assume return type of g is b.
Therefore, (g = a -> b)

Now f takes return value of g as argument (that is, b) and returns a value.
Therefore, ( f = b -> c)

So type of \f g x -> f (g x) is:
Now, look at function declaration: \f g x

(b -> c) -> (a -> b) -> a ->c

6] \x y f -> f (x (\w -> f w)) (y f x)

Above function takes three arguments, x y and f.

Now look at Function body, and assume type for each variable.
Let w = a
   x = t1
       y = t2
       f = t3

Observe the function body, f will be applied to on first argument (x (\w -> f x)), and then it will be applied on second argument (y f x).

Go inside \w function,

f = t3 = a - > b

Therefore, x = t1 = (a -> b) -> c

Return type of x is c, which will become the argument of f, therefore unification is possible here, and c = a;

Hence, x = t1 = (a->b) ->a

Now we examine ( y f x) part,

y = t2 = (a -> b) -> (a->b->a) -> d

d is the return type of y.

After applying the first argument (x(\w->f w)), f returns b.

Therefore, d is parameter of b.

b should take d as argument and return a value, That is, b = d -> e

Now replace each occurrence of b with d -> e

f = a -> b = a -> d -> e

x = (a ->b -> a ) = ((a -> d -> e)- > a)

y = (a ->d -> e) -> ( a -> d -> e) -> a) -> d

Hence type of entire expression is, (arrenge according to function definition:

((a -> d -> e)- > a) ->
(a ->d -> e) -> ( a -> d -> e) -> a) -> d ->
(a -> d -> e) -> e

e is the return type of entire expression which is also the return type of f.

Plugins Vs Extension

2009-11-04T11:05:00.000+08:00

Extension and plugins often confused people. And Mostly people believe both are same.
However, there is subtle difference between Extension and Plugin. Extensions are mostly written in JavaScript and/or XUL and relies on XPCOM APIs to access resources. Whereas, plugins are binary applications and they make use of operating system and can do interaction with operating system or access events from OS.

Securing plugins is more complex than extension. Extension are individual identity so one extension needs one set of privileges, whereas plugins are more complicated and needs to identify privileges for each application runs plugins rather than a whole plugin.

JavaScript Call Stack

2009-10-13T15:32:00.001+08:00

This post explains how to get JavaScript Calls stack in Mozilla extension. You can also use jsdI interface hooks to get JS call stack. Pls refer jsdIDebuggerService on MDC.

You need to call the function callstack( ) to get the JSCall stack. From where to call this function is depend on need of user. You can call this function wherever you want to get JS call stack.

function callstack( ){
/* stackFrameStrings holds entire JS calls stack in string format */

var stackFrameStrings = new Error().stack.split('\n');

/* remove first two stack frames because they are frames of callstack() and error() functions */
stackFrameStrings.splice(0,2);

for (var i in stackFrameStrings) {
      /*
        A stack frame string split into parts. (example of stack frame string is:
        href("http://www.comp.nus.edu.sg")@:0)   Note 0 indicates native function call in Mozilla firefox, and 1 is for onclick, onmouseover functions, ie. JS event functions, otherwise the number is line number in source file and contains URL of source file. Anothe rexample of stack frame string is :
onclick([object MouseEvent])@file:///home/patilkr/Desktop/Html%20Test/js_http_test.html:1
      */
      var stackFrame = stackFrameStrings[i].split('@');

    if (stackFrame && stackFrame.length == 2) {
                dump("\n stackFrame[0]=" + stackFrame[0] + " stackFrame[1]=" + stackFrame[1] );
   } // end of if loop

}//end of for loop
} //end of callstack function

Mozilla Firefox about:config Tweaks

2009-10-07T14:06:00.006+08:00

Accessing your about:config page
In your Firefox, type about:config in the address bar.

Disable Delay Time When Installing Add-on

Config name: security.dialog_enable_delay
Default: 2000 (in msec)
Modified value:

0 – start installation immediately
any other value (in msec)

View Source in Your Favorite Editor
There are two configuration need to be made:
Config name: view_source.editor.external
Default: False
Modified value: True ( enable view source using external text editor)

Config name: view_source.editor.path
Default: blank
Modified value: insert the file path to your editor here.

Autohide Toolbar in Fullscreen mode
Config name: browser.fullscreen.autohide
Default: True (always autohide)
Modified value: False (always show the toolbar)

90/10 and Self assement Principals

2009-10-02T12:21:00.003+08:00

This is a non-technical post. It is about, how to improve yourself. How to improve your thinking and your life. Principals describe here, if you applied in your life then, they will surely help you to feel satisfaction.

First principal is 90/10 Rule:

What is 90/10 Principal? Well, it is very simple. 10% of life is made of what happens to you and 90% of life is decided by how you react to things happens in your day to day life.

Let me explain this in more detail:

We really have NO control over 10% of incidences that happens to us.

For example, We cannot stop plane from arriving late, we cannot stop mechanical devices from breaking down. We cannot control this 10% of incidences happens to us, However, over the 90% of incidences we have control and our reaction to the situation is the key factor which plays an important role in deciding 90% of our life.

If someone says something negative about you, do not be a sponge or do not lose your tamper.

Let the attack roll off like water on glass. You do not have to let the negative comments affect you.

React properly and it will not ruin your day. A wrong reaction could result in losing a friend, or getting stressed out.

Remember the 90/10 Principle and don’t worry about life.

You are told you lost your job. Why lose sleep and get irritated? It will work out.

Use your worrying energy and time to find a new job.

Millions of people are suffering from stress, problems and headaches.

We all must understand and apply the 90/10 Principle.

It can change your life! You will lose nothing if you apply it.

Second Principal is Self Assessment:

Self assessment means do a regular review of your daily activity/reaction/behavior at the end of day. It helps to make judgment about our own actions.

If you apply this two principals in your life, you will surely be get benefited from it, without lossing anything. You will observe its good effect in you life by yourself.

How to access other VMs and Internet on VirtualBox

2009-09-18T15:37:00.003+08:00

VirtualBox supports NAT, host-only, Internal network and Bridged network options.

When Network card of VirtualBox VM is configured with "NAT" option then VM can access host machine and can access Internet, but cannot access other VMs. When I looked at IP address of VM's, I found that they all have same IP address.

VirtualBox assigns same IP to all virtual machine (for example, 10.0.2.15) when NAT is configured. That is, it treats all VM as they on different physical network.

When Network Card of VirtualBox VM is configured with "Internal Network" option then VM can access other VMs but cannot access Internet. In this case, all VM are on same physical network.

If you want to access other VMs as well as Internet, then the simplest solution is install two network cards in VM and assign one to NAT and another to internal network. Then login to all VMs and assign unique address to internal network card of each VM. Note that, you have to assign address to network card which is configured for "Internal Network" in VirtualBox.

That's it. Done. Now you can access Internet as well as other VMs.

Object Oriented Programming

2009-09-18T14:56:00.002+08:00

Struct is use to define data types and group them into one object. Struct does not contain methods or functions, and its data members are all public. Struct are useful when we want sets of element with different data types. Struct is a group of data elements grouped under one name. Those data elements are know as members and can have differnet type and different lengths. Struct creates a new type. Once a struct is created a new type with the name of struct is created. It can be used later on in the program to create objects of struct.

A Class have both data members and functions/methods associated with it. A class can contain sever variables and functions/methods, those are called members of class. Bydefault all its members are private.

Class can define its member as private, protected, public. Protected has a special meaning to inheritance. Protected members are accessible in the class that defines them as well as in the classes that inherit from that base class or friend of it.

Class can contain special member functions called as constructors or destructors. Constructors cannot be explicitly called like regular member functions. They are automatically executed when new object of class is created.

In principal, private and protected members of a class cannot be accessed from outside the scope of the same class in which they are declared. However this rule does not affect friends. Friendship is no transitive and it is not bidirectional.

Inheritance is a key feature of C++ class. It allows to create a class which is derived from other classes, so it can automatically include/inherit members of base class. When class inhertis from another class the members of derived class can access only the public/protected members of base class, but cannot access private members of base class.

In principal, a derived class inherits every member of base class except its constructor, destructor, and its friends.

Virtual function/member: A member of class can be redefined in its derived classes is know as a virtual member.

When the type of pointer is pointer to base class but it is pointing to an object of th derived class, virtual keyword in-front of member functions allows a member function of a derived class with the same name as one in base class to be called from base class pointer to derived class object.

A class that declares or inherits a virtual function/member is called a polymorphic class.

Abstract base class is a class that lacks implementation of atleast one member. Therefore, we cannot create object of that class (cannot create object of ABC - Abstract Base Class). These are the main differences between abstract class and a regular polymorphic class. The function which lacks implementation is called as pure virtual function. for example, virtual int function_name() = 0; However, pointers of ABC (Abstract Base Class) can be used to point to objects of derived classes.

Templates are special types that can operate with generic types. Templates allows us to create a function template whose functionality can be adapted to more than one type without repeating the entire code. That is, we don't need to write the same functionality code for different types such as int, float, char, etc. This allows generic programming, bocz it access any type object.

Vector better than Array and works as Array

2009-09-18T14:27:00.004+08:00

Vector is a template class and it allows programmers to create a dynamic array of elements of one type per instance.

Vector is conceptually same as arrays in C. However, vector size can expand to hold more elements and can shrink when fewer will suffice.

Note: Accessing members of vector or appending elements does not depend on vector size and takes fixed amount of time, however, locating a specific value element or inserting value element into vector takes the amount of time directly proportional to its location in vector.

//////////////////////////////////////////////////////////////////////
// Standard Template Library (STL)
//
// Vector Functions:
//
// vector::push_back - Appends (inserts) an element to the end of a
// vector, allocating memory for it if necessary.
//
// vector::pop_back - Erases the last element of the vector.
//
// vector::size - Returns number of elements in the vector.
//
//////////////////////////////////////////////////////////////////////

#include <iostream>
#include <vector >

using namespace std ;

int main()
{
    // Dynamically allocated vector begins with 0 elements.
    vector<int> theVector;

    // Add one element to the end of the vector, an int with the value 1.
    // Allocate memory if necessary.
    theVector.push_back(1) ;

    // Add two more elements to the end of the vector.
    // theVector will contain [ 1, 2, 3 ].
    theVector.push_back(2) ;
    theVector.push_back(3) ;

    int tmp;

    cout << "\n Enter new element on new line. press Ctrl +D to terminate " <
    while (cin >> tmp)
      theVector.push_back(tmp);

    // Erase last element in the vector.
    theVector.pop_back();
    theVector.pop_back();

    // Print contents of theVector.
    cout << "theVector [" ;
    for (int k =0; k < theVector.size(); k++)
      cout <<" " << theVector[k];

    cout << " ]" << endl ;
}

Who calls main() function in C

2009-09-11T18:09:00.005+08:00

The run-time environment calls the main function to begin program execution.

On Linux operating system, C runtime file can be found in either /usr/lib directory or /lib directory.

crt0 (or crt0.o, gcrt0.o, mcrt0.o) is a set of execution startup routines that are platform-dependent, and is required in order to compile using the GCC and other GNU tools.

crt stands for 'C runtime'.

Let me explain you the life cycle of c program:

1. Create a C program

2. Compile C program to generate object file.

3. Link object files (s)

4. execute the program

During compilation, compiler generates the object code for the program and for standard C library functions used in program such as printf(), scanf (), etc, it puts the entry in object file saying that "unresolved reference".

Linking can be static or dynamic. During static linking,

the static linker (ld) sees the unresolved reference to printf(), scanf(), and searches the available libraries for an implementation for printf(), scanf(), etc. In general this will be found in the C library (for example, libC ). Now, the linker has two options:

Linker can take the printf(), scanf(), implementation from the library and copy it into the final executable accordingly. The linker then  searches the printf(), scanf() implementation for other unresolved references, and again consult the libraries for resolution. This  process will be performed iteratively until all references to the symbols were resolved. This is known as static linking.

If the C library is realized as a `shared library', the linker can simply put a reference to the C library into the final  executable. This is known as dynamic linking.

  
A statically linked executable is self contained. It is loaded into memory. The entry point, whose designation is system  dependent (for eg, the `__main' symbol) is found and called.
In a dynamically linked executable, after loading the executable binary into memory, the dynamic linker (ld.so.1) takes control first. It reads the library references to dynamic libraries produced by the static linker, and loads them into memory. It then performs symbol resolution and updates all references to symbols in the shared library to point to their actual location, which can only be determined at runtime, because the shared libraries might be loaded to different memory locations each time the executable binary gets executed.

C++ pointer

2009-09-10T13:56:00.002+08:00

Pointers

Reference Operator (&)

The address that locates a variable within memory is what we call a reference to that variable.

A variable which stores a reference to another variable is called a pointer.

& is the reference operator and can be read as "address of"

* is the dereference operator and can be read as "value pointed by"

The declaration of pointers follows this format:
type * name;

where type is the data type of the value that the pointer is intended to point to. This type is not the type of the pointer itself! but the type of the data the pointer points to.

For example:

int * number;
char * character;
float * realnumber;

These are three declarations of pointers. Each one is intended to point to a different data type, but in fact all of them are pointers and all of them will occupy the same amount of space in memory. Nevertheless, the data to which they point to do not occupy the same amount of space nor are of the same type: the first one points to an int, the second one to a char and the last one to a float.

Void Pointer

The void type of pointer is a special type of pointer. In C++, void represents the absence of type, so void pointers are pointers that point to a value that has no type.

Makefile

2009-09-03T21:33:00.091+08:00

Compiling the source code of your program/project on Linux/UNIX system is tedious, specially when program/project has several source files and you have to type command every time you want to compile it.

There is a utility called make to build the applications. Make looks for a text file in the current directory called "makefile" or "Makefile" to execute. Makefile is a file that instructs the program make how to compile and link a program. In this post I will explain, how to use GNU make utility with Makefiles.

How to write comments in the makefile:

The comment in the Makefile is indicated by the comment character “#”. All text from the comment character to the end of the line is ignored.

Example:

# This is the comment in the Makefile

# Comment

How to define Variable in the Makefile:

You can define variable in the makefile. Variable definition format is as follows:

VARNAME = Value

For example, Lets define a variable and set it to the compiler which I want to use to compile my program code.

CC = g++

CC is the variable name and g++ is the compiler I want to use to compile my program.

How to use the variable:

We have define the variable CC above, now let me explain you, how to use it.

To use the variable syntax is as follows:

$(VARNAME)

In our example, we define CC variable, we can access the variable as follows:

$(CC)

How to compile program using command line:

Suppose my program name is myprog.cpp. To compile it, I have to type following command:

g++ -o myexe myprog.cpp

Whereas myexe is an executable file name and myprog.cpp is the source file of my program.

If I want to compile my program multiple times then I have to issue this command multiple times.

Things become more complicated when I need to give some parameter to compile my program such as

optimization parameters, library paths, etc.

Makefile comes for rescue here.  Create a new text file and named it as Makefile. Do not give any extension to it.

Simply put the command (g++ -o myexe myprog.cpp) in the makefile, save the file, and at command

prompt type make

#Makefile
     g++ -o myexe myprog.cpp

Now suppose we have three source files namely mainprog.cpp, file1.cpp and file2.cpp.

Then you can create a makefile as follows:

g++ -c -o file1.o file1.cpp
g++ -c -o file2.o file2.cpp
g++ -o myexe mainprog.cpp file1.o file2.o

You can now make use of variables and can make the Makefile much simpler as shown below:

COMPILER=g++
OBJS=mainprog.o file1.o file2.o
default: myapp

myapp: $(OBJS)
 $(COMPILER) -o myexe $(OBJS)

You only need to issue only the make command everytime you want to compile you program, that's it.

If the source file in your project increses then you only have to add filename.o to

OBJS variable list, that's it. Very simple.

JavaScript Scramblers / Obfuscators Softwares and Techniques they used

2009-09-02T11:37:00.021+08:00

There are many JavaScript Scrambling softwares/tools available on Internet.
All of them aims to scramble the JavaScript source code to prevent the theft of JavaScript Code.
Obfuscated code is a source code that is very hard to read and understand. 
Macro preprocessors are often used to create hard to read code by masking the standard language syntax and grammar from the main code.

How to create hard to read code (Obfuscated code)?
Take a JavaScript code in .JS files or in HTML files as a input  and replace descriptive variable and function names like Customer, Salary, FirstName... with meaningless names like x0de234f, III111000, oo00ooo... 
Also removes comments and unnecessary whitespace characters (space, tab, carriage return, line feed). The functionality of the code remains the same while source code changes dramatically. This process is called obfuscation, and the tool is called obfuscator.

I tried to find and collect under one roof information about JavaScript Obfuscators.

1. Stunnix JavaScript Obfuscator
 Stunnix JavaScript Obfuscator converts scripts in input files into highly mangled and obfuscated form, while fully retaining  functionality of the original code.
 It provides different encoding techniques such as MD5 (Message Digest version 5), set of o and 0, and set of I and 1 for identifiers/variables/function names. Similarly it provides different encoding technique such as Hex escapes, List of codes for strings. It uses regular expression to replace numbers. It gives freedom to the programmer to select encoding technique of there choice to make JavaScript code difficult to study and analyze. It is also possible to encode the code using one set of encoding techniques and again encode the encoded code using different set of encoding techniques supported by the tool. For example, first encode using a set {MD5, Hex escapes, regular expression} and then encode the encoded code using same or another set of supported techniques by the tool such as {set of o and 0, List of codes, regular expressions}.   
 Examples of Encoding techniques of Stunnix tool are given below:
 Encoding for Identifiers/variables/function name:
  1. MD5: Message Digest version 5, 
   It generates hash value for identifier/variable_name or function_name and replaces the occurrence of identifier/variable with its hash value. (for example every occurrence of FACTORIAL function name in the script is replaced with it hash value Z001C775808)
  2. set of I and 1
   It generates a unique set of I's and 1's for each identifier/variable_name ( for example every occurrence of      SHOW_TOP_RECORDS function name in the script is replaced by IlIlIIIllI)
  3. set of o and 0 
   It generates a unique set of o's and 0's for each identifier/variable_name ( for example every occurrence of      SHOW_TOP_RECORDS function name in the script is replaced by o0o0ooo00o)
 Encoding for strings in the script:
  1. Hex escapes
   It uses Hex encoding for strings (for example no entries is replaced with  \x3c\x62\x3e\x6e\x6f\x20\x65\x6e\x74\x72\x69\x65\x73\x3c\x2f\x62\x3e)
  2. List of Codes
   Adds some constant prefix such as ReplacementFor_ to every occurance of string. (for example  strcomputer variable is replaced with ReplacementFor_strcomputer)
 Encoding for numbers/digits
  It uses regular expression to encode numbers in the script. (For example every occurrence of number 232 is get replaced with 0x14b6+2119-0x1c15 in the script)

2. TagsLock Pro. 
 Replaces string characters (ASCII) with hexadecimal equivalent value and each preceded by a percent symbol. (For example, space character is hexadecimal 20, so the encoded version of a space character is %20)
 It uses JavaScript inbuilt function escape() to generate encoded version of string and uses inbuilt JavaScript function unescape() to decode it.

 For example:
   Original JavaScript:
      document.write("Hello, world!");    

    Scrambled JavaScript:

          document.write(unescape('%3cs%63ript%3e%3c%21%2d-%0d%0ado%63ument.write("%48%65llo%2c %77orld%21"); %0d%0a%2f%2f %2d%2d%3e%0d%0a%3c/s%63%72i'+'pt%3e %0d%0a%0d%0a'))      


3. iWeb Tool. 
 Similar to TagsLock Pro, iWeb tool uses escape() function to convert string (ASCII) into hex encoding.  But to make it more confusing it perform encoding on hex encoded string and converts hex encoded string into unicode. 
 To decrept it uses a inbuilt JavaScript function String fromCharCode() to convert it from Unicode to hex codes and then using unescape () function converts hex codes into a string (ASCII). 
 It keeps the Javascript inbuilt function name as it is, such as document.write in original source code will as it is appear in encoded code.
 For example:
 Original Code:
   document.write("Hello")

Encrypted Code:
  var enkripsi="'1Aqapkrv'1Gfmawoglv,upkvg'0:'00Jgnnm'00'0;'1A-qapkrv'1G"; teks=""; teksasli="";var    panjang;panjang=enkripsi.length;for (i=0;i2) }teksasli=unescape(teks);document.write(teksasli);


4. Javascript Obfuscator v2.53. 
 It reads files with JavaScript code and replaces each occurance of descriptive
variable and function names like CHILDNODE, FIRSTNAME, LASTNAME... with meaningless names like Ia, g, m... 
It also removes comments and unnecessary whitespace characters (such as space, tab, carriage return, line feed).

5. Ajaxian JavaScript Obfucator. 
 It is same as JavaScript Obfuscator v2.53. 
 And Like a iWeb tool, it does not replace document.write() function name, that is the rule is not to replace the function name or vaiable name if it has ".". 

6. JavaScript Scrambler v1.11. 
 It is the simplest JavaScript Obfuscator, which removes comments and unnecessary whitespace characters. It keeps the variable names and Javascript code as it is; except only changes function names in the original code. (for example,  every occurance of function name "doTICKER" is get replaced with "x0822631")


References
1. Stunnix JavaScript Obfuscator. http://www.stunnix.com/prod/jo/
2. TagsLock Pro. http://www.aerotags.com/faq/tips-js-protection.php
3. iWeb Tool. http://www.virtualpromote.com/tools/javascript-encrypt/
4. Javascript Obfuscator v2.53. http://javascript-source.com/javascript-obfuscator.html
5. Ajaxian JavaScript Obfucator. http://ajaxian.com/archives/utility-javascript-obfuscator
6. JavaScript Scrambler v1.11. http://www.quadhead.de/jss.html

Obfuscated code examples

2009-09-02T11:26:00.007+08:00

In this post I will give to some examples of JavaScript Obfuscation.

Example 1:

This following code is obfuscated using online JavaScript Obfuscator on http://www.javascriptobfuscator.com/

Plain text Code:

var a="Hello World!";
function MsgBox(msg)
{
alert(msg+"\n"+a);
}
MsgBox("OK");

Obfuscated code:
var _0x8e48=["\x48\x65\x6C\x6C\x6F\x20\x57\x6F\x72\x6C\x64\x21","\x0A","\x4F\x4B"];var a=_0x8e48[0];function MsgBox(_0xab5dx3){alert(_0xab5dx3+_0x8e48[1]+a);} ;MsgBox(_0x8e48[2]);

You can apply multiple level of obfuscation by repeatedly obfuscating the obfuscated code.

Following obfuscated code is 2 level obfuscation of plain text code given above. That is, obfuscation of obfuscated code.

Obfuscated code of the Obfuscated code given above:

var _0x1c08=["\x48\x65\x6C\x6C\x6F\x20\x57\x6F\x72\x6C\x64\x21","\x0A","\x4F\x4B"];var _0x1bae=[_0x1c08[0],_0x1c08[1],_0x1c08[2]];var a=_0x1bae[0];function MsgBox(_0xc9d7x4){alert(_0xc9d7x4+_0x1bae[1]+a);} ;MsgBox(_0x1bae[2]);

Example 2:

The following code is obfuscated using online JavaScript Obfuscator. http://www.virtualpromote.com/tools/javascript-encrypt/

Plain text code:

document.write("hello, world");

Obfuscated code:

var enkripsi="'1Aqapkrv'1G'2Cfmawoglv,upkvg'0:'00jgnnm'0A'02umpnf'00'0;'1@'2C'1A-qapkrv'1G";
teks="";
teksasli="";
var panjang;
panjang=enkripsi.length;
for (i=0;i
teks+=String.fromCharCode(enkripsi.charCodeAt(i)^2)
}
teksasli=unescape(teks);
document.write(teksasli);

In the second example, document.write is used. So during parsing of the code in the browser (for example, Firefox), DOM nodes will be get created for obfuscated code and for each level of de-obfuscated code.

Obfuscated Code

2009-08-29T18:32:00.008+08:00

When source code in programming language is transform to human unreadable form then it is known as Obfuscated Code. The software that performs obfuscation on code are called as obfuscators.

Obfuscation on the source code can be used for good purpose as well as for bad purpose. Programmers can obfuscate there code to conceal its purpose, to avoid theft of there code. This is also known as security through obscurity. On other hand, attackers can use obfuscator to hide malicious program.

The code written in languages which can be obfuscated includes but not limited to are C, C++, Perl, JavaScript, etc.

Obfuscation by code morphing refers to obfuscating machine language code or object code rather than obfuscating the source code.

Obfuscated code makes it difficult to reverse engineer the code, but it is not impossible to reverse engineer the obfuscated code. Obfuscated code makes it difficult to debug, because the variable names no longer make sense, and the structure of code is hard to recognize.

In this post I will mainly focus on the JavaScript Obfuscators, techniques used for JavaScript Obfuscation, and JavaScript Obfuscation used in malicious software.

Obfuscated JavaScript code is mostly used by spammers in spam messages. The obfuscation makes it difficult for investigators to identify what exactly the JavaScript code does? or where the link goes?. Attackers used JavaScript Obfuscation to conceal an entire or some part of code that runs browser exploit.

The good news about JavaScript source code obfuscation techniques is, they are limited to number of techniques (de-obfuscation) supported by Web browser. However the bad news is, it is not limited to number of levels of obfuscation on source code.

While mixing C and C++ code, how to avoid name mangling done by C++ compiler for C Code

2009-08-28T19:16:00.005+08:00

C language does not have overloading, that's why C function names are not mangled by C compiler (such as GCC), but C++ has overloading. Overloading means the same function name can appear for more than two functions in C++ with different parameters. That's why C++ complier do name mangling to identify the function names uniquely.

You may encounter a problem while writing you own library by mixing C and C++ code. because you have to compile it with C++ compiler and it will mangled the function names. If you want to avoid the mangling of function names done by C++ compiler then you can use extern "C" keyword in the code. This will tell C++ compiler that do not mangled function names, variable names, defined in extern "C" brackets.

For example:

extern "C"
{
   int functionx();
}

The name of functionx will not be get mangled by C++ compiler.

Firefox-3.5 debugging problem on Ubuntu9.04

2009-08-26T19:19:00.007+08:00

I and my colleague Xinshu are working on Firefox-3.5 web browser and from last few months since Firefox-3.5 is released we were searching for how to debug Firefox-3.5 with gdb on ubuntu v9.04. We are able to debug Firefox-3.0 with gdb on ubuntu v9.04, but we were not be able to debug Firefox-3.5. Whenever we tried to debug Firefox-3.5 with gdb debugger, GDB sometimes terminated by giving "Segmentation Fault" error , or sometimes terminated by giving memory leak error. So we developed a wrong impression that Firefox-3.5 cannot be debug with gdb in Ubuntu v9.04, because official version of Firefox-3.5 for ubuntu is not yet released. Ubuntu has Firefox v3.0.13 in its repository. However for Fedora and Windows, Firefox v3.5.2 is available. We searched on many blogs/forums, etc for the solution or does somebody faced/facing the same problem as we do. Many of them misdirected by saying some package is missing on your machine, which is required for Firefox-3.5 to debug on Ubuntu v9.04. We installed all the packages named on those forums, but had no luck, till today.
My colleague (Xinshu) finally discovered the caused of error. And the solution was very simple, but not convenient for users who has many Firefox profiles for different purpose .
When we looked into terminal window, we found that GDB terminated after Firefox creates a new process. And new process is created when you have multiple profiles on your system, and selecting the one out of them each time Firefox starts, was the source of error. Firefox creates a new process whenever we select the profile.
So we tried by deleting all profiles, and it was miracle, it really worked. The solution is very simple, delete all Firefox profiles and then try Firefox-3.5 to debug with GDB on Ubuntu. It works!.
Although it is not convenient to users who have many profiles.

DOS attack on Firefox

2009-08-26T19:13:00.008+08:00

Denial of Service (DOS) Attack for Firefox

It is caused by consuming memory on user computer.

The main reason, why this attack is possible on Firefox is insufficient memory check at document.write function.

The parser first builds DOM tree on received input before it is displayed to user (or it is given to rendering unit). Following code consumes all available memory on your system, if you have quad-core processor with 4GB RAM then following code will terminate on that machine after few hours. (approx, 8 to 10 hrs)

The sample code is given below:
var a;
for (var i=0; i < 32000; i++) {

document.write(a+=i));

}
document.write("Terminated");

Backtrace is as follows:

nsScannerString::AppendBuffer()

nsScanner::AppendToBuffer()

nsScanner::Append()

nsParser::Parse()

nsHTMLDocument::WriteCommon()

nsHTMLDocument::ScriptWriteCommon()

nsHTMLDocument::Write()

Chrome browser uses behavior analysis to detect unresponsive scripts/programs.

Function call analysis will not work correctly on such kind of examples, bcoz attacker can create the same effect (DOS attack) in many different ways.

Mozilla has dom.max_script_run_time variable which is set 10 by default. In debug mode, Firefox would prompt user with a warning against that unresponsive script; however, this warning does not appear in normal mode and the script hangs Firefox (or even the whole system) after some time. In another word, Firefox has built-in check for unresponsive script, but this mechanism somehow just won't work for this example in normal mode.

I tested the above code in Internet Explorer, but IE show a pop-up window and ask user, he want to terminate the script or want to continue the execution of script. I think that's the expected behaviour.

Encrypted Virtual File System (EVFS): Building a encrypted Linux filesystem from an ordinary linux file

2009-08-25T17:20:00.011+08:00

This tutorial will explain step-by-step process to create Encrypted Virtual Linux File System (EVFS).

First let me explain you, What are the advantages of EVFS:
1. You can take a disk file, format it as an vfat, ext3 filesystem, and then mount it, just like a physical drive. This is an excellent way to investigate different filesystems without hassle of reformatting a physical drive.

2. It protects unauthorized access to the information.

3. It is a single file which will acts as encrypted virtual disk, that will store files, directories inside it.

4. The big advantage is, it is Portable. The file we create here will open as encrypted virtual disk in windows, Linux, etc.

We will use LUKS (Linux Unified Key Setup) standard for creating encrypted virtual file system.

LUKS is a standard for hard disk encryption. Most disk encryption software implements different and incompatible formats, LUKS specifies a platform-independent standard on disk format for use in various tools on different operating systems such as Windows, Linux, etc

In this article, I will explain how to create encrypted virtual disk, how to use it on Linux and how to use it on windows.

A. How to create Encrypted Virtual Disk

Step1: Create a file with desired size. (The size you will specify here will be the size of your virtual disk.)

dd if=/dev/urandom of=disk.img bs=1M count=10

I used urandom to fill the file with random values. You can use if=/dev/zero instead of if=/dev/urandom to fill the file with zeros. Bydefault dd uses 512bytes as a size parameter. We define custom size using bs argument, as show in example (in blue colour). The bs argument accepts common suffixes (k, M, G) for large numbers. bs specifies the number of bytes read into memory with single read() system call and written out with s single write() system call. I created 10MB file in this example. (size = bs * count). You can tune the bs and count parameters according to your need.

Step 2: Make the file we created as a disk device

sudo losetup /dev/loop0 disk.img

Loop device makes a file accessible as a block device. losetup command associats the file (disk.img in our example) with loop device (loop0 in our example)

Step 3: Now we have a partition of 10MB. In this step we will encrypt that partition.

sudo cryptsetup luksFormat -c aes -s 256 /dev/loop0

-c parameter is used to specify cipher. I used AES (Advanced Encryption Standard) in this example.
-s parameter is used to specify keysize for cipher in bits. It must be multiple of 8 bits. In this example I used 256 bit cipher key.

(Note: You can tune above parameters according to ur need)

(Note: This will ask you for confirmation before proceeding, you have to type YES in uppercase, if you want to continue. Then it will ask you for password for EVFS. This password you have to use whenever you want to access EVFS).

Step4: Now tell Linux to treat the encrypted partition as a Disk Device.

sudo cryptsetup luksOpen /dev/loop0 krp

krp is the name of disk device. you can use any name there.

Step5: Now Format the file system on ths disk

sudo mkfs -t vfat /dev/mapper/krp

Step6: Done. Cleanup the system now.

sudo cryptsetup luksClose krp
sudo losetup -d /dev/loop0

Now we have a single file as a encrypted virtual file system. In that file we can store any data which we want to hide from others. And as it is a single file you can move it from one machine to another machine without hassle of reformatting and installation of OS.

B. How to use Encrypted Virtual File System on Linux

Step 1: Tell Linux to treat this file as a disk device

sudo losetup /dev/loop0 disk.img

Step2: Tell Linux to treat the encrypted partition as a disk device

sudo cryptsetup luksOpen /dev/loop0 kailas

Step3: Mount the disk

sudo mount /dev/mapper/kailas /mnt

Now you can access the files in directory /mnt
You can create new files there or copy files there. Those files will be stored in your encrypted Virtual FileSystem.

C. How to cleanup EVFS after using it on Linux

sudo umount /dev/mapper/kailas
sudo cryptsetup luksClose kailas
sudo losetup -d /dev/loop0

D. How to use Encrypted Virtual File System on Windows

To open/access the EVFS we created above on Windows, download a open source free software FreeOTFE.
Install the FreeOTFE software, then launch the FreeOTFE software.
Select "File-> Linux Volume -> Mount File"

Enter the password of EVFS. FreeOTFE will show the virtual drive. Done!.