IDITAROD

How to increase service start/stop timeout ?

2011-12-13T03:55:00.001-08:00

Windows provide SetServiceStatus function by which one can manage service time out period. It’s a very straight forward API here are its details:-

BOOL WINAPI SetServiceStatus(

__in SERVICE_STATUS_HANDLE hServiceStatus,

__in LPSERVICE_STATUS lpServiceStatus

);

To manage timeout one need to inform SCM periodically about the current status of service. So if one have pending operations same information can be conveyed with this interface to SCM.

A common bug is for the service to have the main thread perform the initialization while a separate thread continues to call SetServiceStatus to prevent the service control manager from marking it as hung. However, if the main thread hangs, then the service start ends up in an infinite loop because the worker thread continues to report that the main thread is making progress.

Here are the details of structure

typedef struct _SERVICE_STATUS {

  DWORD dwServiceType;

  DWORD dwCurrentState;

  DWORD dwControlsAccepted;

  DWORD dwWin32ExitCode;

  DWORD dwServiceSpecificExitCode;

  DWORD dwCheckPoint;

  DWORD dwWaitHint;

} SERVICE_STAT

And following are the main parameters to be used while managing service time out duration in the structure

dwCheckPoint

The check-point value the service increments periodically to report its progress during a lengthy start, stop, pause, or continue operation. For example, the service should increment this value as it completes each step of its initialization when it is starting up. The user interface program that invoked the operation on the service uses this value to track the progress of the service during a lengthy operation. This value is not valid and should be zero when the service does not have a start, stop, pause, or continue operation pending.

dwWaitHint

The estimated time required for a pending start, stop, pause, or continue operation, in milliseconds. Before the specified amount of time has elapsed, the service should make its next call to the SetServiceStatus function with either an incremented dwCheckPoint value or a change in dwCurrentState. If the amount of time specified by dwWaitHint passes, and dwCheckPoint has not been incremented ordwCurrentState has not changed, the service control manager or service control program can assume that an error has occurred and the service should be stopped. However, if the service shares a process with other services, the service control manager cannot terminate the service application because it would have to terminate the other services sharing the process as well.

A sample code showing the use of above discussed variable :-

//

// Purpose:

//   It will set the current service status and reports it to the SCM.

//

// Parameters:

//   dwCurrentState - The current state (see SERVICE_STATUS)

//   dwWin32ExitCode - The system error code

//   dwWaitHint - Estimated time for pending operation,

//     in milliseconds

//

VOID ReportServiceStatus( DWORD dwCurrentState,

                      DWORD dwWin32ExitCode,

                      DWORD dwWaitHint)

    static DWORD dwCheckPoint = 1;

    // Fill in the SERVICE_STATUS structure.

    gSvcStatus.dwCurrentState = dwCurrentState;

    gSvcStatus.dwWin32ExitCode = dwWin32ExitCode;

    gSvcStatus.dwWaitHint = dwWaitHint;

    if (dwCurrentState == SERVICE_START_PENDING)

        gSvcStatus.dwControlsAccepted = 0;

    else gSvcStatus.dwControlsAccepted = SERVICE_ACCEPT_STOP;

    if ( (dwCurrentState == SERVICE_RUNNING) ||

           (dwCurrentState == SERVICE_STOPPED) )

        gSvcStatus.dwCheckPoint = 0;

    else gSvcStatus.dwCheckPoint = dwCheckPoint++;

    // Report the status of the service to the SCM.

    SetServiceStatus( gSvcStatusHandle, &gSvcStatus );

One more important thing to remember :

Ø   Do not wait longer than the wait hint. A good interval is one-tenth of the wait hint but not less than 1 second  and not more than 10 seconds.

          Example:-

        dwWaitTime = ssStatus.dwWaitHint / 10;

        if( dwWaitTime < 1000 )

            dwWaitTime = 1000;

        else if ( dwWaitTime > 10000 )

            dwWaitTime = 10000;

The following are some of the best practices when calling SetServiceStatus function:

Initialize all fields in the SERVICE_STATUS structure, ensuring that there are valid check-point and wait hint values for pending states. Use reasonable wait hints.
Do not register to accept controls while the status is SERVICE_START_PENDING or the service can crash. After initialization is completed, accept the SERVICE_CONTROL_STOP code.
Call this function with checkpoint and wait-hint values only if the service is making progress on the tasks related to the pending start, stop, pause, or continue operation. Otherwise, SCM cannot detect if your service is hung.
Enter the stopped state with an appropriate exit code if ServiceMain fails.
If the status is SERVICE_STOPPED, perform all necessary cleanup and call SetServiceStatus one time only. This function makes an LRPC call to the SCM. The first call to the function in the SERVICE_STOPPED state closes the RPC context handle and any subsequent calls can cause the process to crash.
Do not attempt to perform any additional work after calling SetServiceStatus with SERVICE_STOPPED, because the service process can be terminated at any time.

Inline function example, a sample program c++

2011-12-03T10:07:00.001-08:00

Inline function examples :-
recommended article :- Inline Function

Lets look out one of the simple example :-

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

// inline_functions_inline.cpp
#include 
#include 

inline char toupper( char a ) {
   return ((a >= 'a' && a <= 'z') ? a-('a'-'A') : a );
}

int main() {
   printf_s("Enter a character: ");
   char ch = toupper( getc(stdin) );
   printf_s( "%c", ch );
}

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

Now  moving to example of using inline function inside a class :-

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

// Inline_Member Function example

class CBankAccount
{
public:
    CBankAccount(double initial_balance) { balance = initial_balance; }
    double GetBalance();
    double Deposit( double Amount );
    double Withdraw( double Amount );
private:
    double balance;
};

inline double CBankAccount::GetBalance()
{
    return balance;
}

inline double CBankAccount::Deposit( double Amount )
{
    return ( balance += Amount );
}

inline double CBankAccount::Withdraw( double Amount )
{
    return ( balance -= Amount );
}

int main()
{
 CBankAccount objAccount;
 objAccount.Deposit(1000);
}

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

Just as you can ask the compiler to make a regular function inline, you can make class methods inline. The keyword inline appears before the return value. In the class declaration, the functions were declared without the inline keyword. The inline keyword can be specified in the class declaration; the result is the same.

 Inline functions are best used for small functions such as accessing private data members. The main purpose of these one- or two-line "accessor" functions is to return state information about objects; short functions are sensitive to the overhead of function calls. Longer functions spend proportionately less time in the calling/returning sequence and benefit less from inlining.
 Read More :- Guidelines for using Inline function.

Check this out

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

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How to start , stop perfmon from the command line in Windows ?

2011-11-22T23:21:00.001-08:00

Logman command is the solution for it.
let's have a look at the command syntax

Syntax Verbs
Logman [create {counter | trace} collection_name ] [start collection_name] [stop collection_name] [delete collection_name] [query {collection_name|providers}] [update collection_name]

Parameter details:-

create {counter | trace} collection_name : Creates collection queries for either counter or trace collections. You can use command line options to specify settings.

start collection_name : Starts the data collection query collection_name. Use this option to change from scheduled collections to manual ones. Use the update parameter in the command line with begin-time (-b), end-time (-e), or repeat-time (-rt) to reschedule collections.

stop collection_name : Stops the data collection query collection_name. Use this option to change from scheduled collections to manual ones. Use the update parameter in the command line with begin-time (-b), end-time (-e), or repeat-time (-rt) to reschedule collections.

delete collection_name : Deletes the data collection query collection_name. If the collection_name does not exist, you will receive an error.

query {collection_name|providers} : If no collection_name or providers are given, the status of all existing collection queries are displayed. Use collection_name to display the properties of a specific collection. To display the properties on remote computers, use the -s remote computer option in the command line. Use providers as your keyword in place of collection_name to display the registered providers installed on your local system. To list registered providers installed on the remote system, use the -soption in the command line.

update collection_name : Updates collection queries for counter and trace collections. For counter collections, modifications to the query will stop, and then restart the collections. For trace collections, use the following parameters in the command line to query without stopping the collection: -p provider [(flags[,flags ...])] Level, - max n, - o PathName, -ft mm:ss, or -fd.

This command is very helpful in performance automation scenario.
If performance monitoring counter name is test_perf_log
then start command will go as :-
logman start test_perf_log
on similar line stop command will go as:-
logman stop test_perf_log

For more detail jump to page :- http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/nt_command_typeperf.mspx?mfr=true

Google MAP APIs to charge for usage, heavy traffic cost more

2011-11-01T22:57:00.000-07:00

Google MAP server with their increased traffic has given a new dimension of earning to Google. With its success now Google is planning to charge for its usage.
Now one has to pay according to their usage.

Following is the cost estimation as per BBC
"The BBC is reporting that from 1 January 2012, Google will charge for the Google Maps API service when more than the limit of 25,000 map "hits" are made in a day. Google is rumoured to be charging $4 per 1,000 views in excess of the limit. Google maintains the high limit of 25,000 free hits before charging 'will only affect 0.35% of users.'"

In the Google announcement: "We understand that the introduction of these limits may be concerning. However with the continued growth in adoption of the Maps API we need to secure its long term future by ensuring that even when used by the highest volume for-profit sites, the service remains viable. By introducing these limits we are ensuring that Google can continue to offer the Maps API for free to the vast majority of developers for many years to come."

About Google Maps API

The Maps API is a free service, available for any web site that is free to consumers. Please see the terms of service for more information.

Businesses that charge fees for access, track assets or build internal applications must use Google Maps API Premier, which provides enhanced features, technical support and a service-level agreement.

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How to stop function inlining ?

2011-10-20T03:02:00.001-07:00

__declspec(noinline) tells the compiler to never inline a particular member function (function in a class).

It may be worthwhile to not inline a function if it is small and not critical to the performance of your code.

That is, if the function is small and not likely to be called often, such as a function that handles an error condition.

Keep in mind that if a function is marked noinline, the calling function will be smaller and thus, itself a candidate for compiler inlining.

More about inlining :-

Distance Calculation from Latitude/Longitude using Google MAP APIs between two locations

2011-10-16T06:58:00.000-07:00

Here is a sample application which i have developed to get the direction, distance and duration between two location/places using Latitude/Longitude with the help of Google MAP APIs.

This application will also reveals that how can we retrieve place/city name from the Latitude/Longitude.

Let's look at the input of application :-

Just input Lat/Lng and press "get Directions with Distance/Duration!" and get the updated direction MAP with Distance and Duration.
Place A and Place B will displays the Lat/Lng resolved location.

Check out its demo :-

Google Maps API Sample, Distance from Latitude and Longitude between two locations

Maps API Directions Illustrated with Latitude and Longitude

From:		To:
Place A:		Place B:
Distance	KM	Duration	Minutes
Language:

Formatted Directions	Map

Google's new web programming language, Dart

2011-10-14T11:22:00.000-07:00

Google recently came up with new programming language for web application named as Dart.
Let's look at its technical specification :-

Dart is a new class-based programming language for creating structured web applications. Developed with the goals of simplicity, efficiency, and scalability, the Dart language combines powerful new language features with familiar language constructs into a clear, readable syntax.

In 2009, Google launched Go, a language designed for writing server software and handling other chores often handled today by C or C++. Dart, though, is "a new programming language for structured Web programming," according to the schedule for the Goto conference where Googlers plan to describe it next month.

Some Key feature mentioned by google about Dart.

Key features of the Dart language include:

Classes
Classes and interfaces provide a well understood mechanism for efficiently defining APIs. These constructs enable encapsulation and reuse of methods and data.
Optional types
Dart programmers can optionally add static types to their code. Depending on programmer preference and stage of application development, the code can migrate from a simple, untyped experimental prototype to a complex, modular application with typing. Because types state programmer intent, less documentation is required to explain what is happening in the code, and type-checking tools can be used for debugging.
Libraries
Developers can create and use libraries that are guaranteed not to change during runtime. Independently developed pieces of code can therefore rely on shared libraries.
Tooling
Dart will include a rich set of execution environments, libraries, and development tools built to support the language. These tools will enable productive and dynamic development, including edit-and-continue debugging and beyond—up to a style where you program an application outline, run it, and fill in the blanks as you run.

More information about Dart can be found at :- http://www.dartlang.org/

Sample "Hello World" program :-

main() {
var name = 'World';
print('Hello, ${name}!');
}

Tutorial for Dart language :- http://www.dartlang.org/docs/getting-started/

How to use Dart with HTML ?
Like JavaScript, Dart programs can be directly embedded on HTML pages served to the browser.
Here is the example for it :-

simple Hello World in HTML using Dart. The main() method is the entry point.

<html>
<body>
<script type='application/dart'>
void main() {
HTMLElement element = document.getElementById('message');
element.innerHTML = 'Hello from Dart';
}
</script>
<div id='message'></div>
</body>
</html>

The div element above is guaranteed to exist by the time the Dart code starts running.

Let's see now whether in future DART will hit its target or not.

How to write HTML code inside blogger blog post ?

2011-10-12T23:13:00.000-07:00

Most of the time it become very messy when we try to write HTML code inside blog post.
It does not appear in the same way as we want when we publish it.

Following are some tricks which one can follow to simplify this process :-

1) Using existing HTML editor for writing complete content, and then copy paste entire content in post HTML mode.
2) Encode specific code with HTML encoder :-
shared one link here for you : http://centricle.com/tools/html-entities/
a) Write your html code or any other code in the above site
b) Press encode button. This will change all html tags with relevant encoded symbols ( e.g. < with < )
c) Copy and paste encoded content into your compose post window.
here is the demo of embedded code:-

void CLogicalTimeMarker::RegisteringFlag(int nModuleID, char* pszName)
{
if(NULL != pszName && nModuleID <= g_nMaxModuleSupported)
{
m_stArrTimeAccounterStats[nModuleID].strName = pszName;
}
}

Here is one more site doing same html code encode:-
http://www.eblogtemplates.com/blogger-ad-code-converter/

Though one can embed any type of code like c/c++ , javascript , html with discussed approach.

Distance between two locations with the help of Latitude and Longitude

2011-10-12T10:45:00.000-07:00

Finding Distance between two locations with Latitude and Longitude.

Lets see how can we find out the distance and duration between two diffrent locations,
if you have the latitude and longitude of two places.

Here is the pic of the application :-

Steps for finding distance with latitude/longitude.
1) Lets say we have latitude and longitude set P1 and P2.
    Google MAP comes up with the class GLatLng. This class helps to encapsulate Latitude
    and Longitude.
    GLatLng is a point in geographical coordinates longitude and latitude. Notice that although usual map projections associate longitude with the x-coordinate of the map, and latitude with the y-coordinate, the latitude cooridnate is always written first, followed by the longitude, as it is custom in cartography.

2) From this GLatLng points we need to get place name first.
    class GClientGeocoder will help us to get the place name from LatLng.
   This class is used to communicate directly with Google servers to obtain geocodes for user specified addresses. In addition, a geocoder maintains its own cache of addresses, which allows repeated queries to be answered without a round trip to the server. As a general best practice, it is not recommended to use GClientGeocoder functions in a loop. Developers that have multiple addresses to geocode should probably use our HTTP Geocoder instead.

Method :- getLocations(latlng:GLatLng, callback:function)

This method performs reverse-geocoding, the conversion of a latitude/longitude pair into human-readable addresses. getLocations() sends a request to the Google geocoding service, asking it to return the address for the given latlng and pass the response in the given callback. As this method requires a call to a Google server, you must also pass a callback method to handle the response. This response will contain a Status code, and if successful, one or more Placemark objects. Note that this method may instead pass an addressable String, as indicated above; in that case, the service will do a standard geocode. If however, the first argument contains a GLatLng, the service will do a reverse-geocode.

Here is the example of function :-

function showAddress(response) {
  map.clearOverlays();
  if (!response || response.Status.code != 200) {
    alert("Status Code:" + response.Status.code);
  } else {
    place = response.Placemark[0];
    point = new GLatLng(place.Point.coordinates[1],place.Point.coordinates[0]);
    marker = new GMarker(point);
    map.addOverlay(marker);
    marker.openInfoWindowHtml(
        'orig latlng:' + response.name + ' ' + 
        'latlng:' + place.Point.coordinates[1] + "," + place.Point.coordinates[0] + ' ' +
        'Status Code:' + response.Status.code + ' ' +
        'Status Request:' + response.Status.request + ' ' +
        'Address:' + place.address + ' ' +
        'Accuracy:' + place.AddressDetails.Accuracy + ' ' +
        'Country code: ' + place.AddressDetails.Country.CountryNameCode);
  }
}

3) With the help of place name, we will query map for getting the distance and duration.
A sample code snippet for displaying location with map :-

// Create a directions object and register a map and DIV to hold the 
// resulting computed directions

var map;
var directionsPanel;
var directions;

function initialize() {
  map = new GMap2(document.getElementById("map_canvas"));
  directionsPanel = document.getElementById("my_textual_div");
  directions = new GDirections(map, directionsPanel);
  directions.load("from:"+ fromAddress + "to: " + toAddress);
}

fromAddress and toAddress is the same which we can retrieve easily with as we have discussed in step 2.

Let's see the demo in a sample application

From:			To:
Place A:			Place B:
Language:

Formatted Directions	Map

How to add gadget to blogger header ?

2011-10-01T03:18:00.000-07:00

Recently experimenting with blogger template came across need of adding gadget to blogger header.

Its very simple , just follow the steps below :-
1) Go to the edit section of blogger template.
Template->Edit HTML
2) Search for following code which is about header.

<b:section class='header' id='header' maxwidgets='1' showaddelement='no'>

3) Just change the showaddelement to yes.
4) Now move back to template layout view and now one can gadget to the header.

In addition to it one can also change maxwidgets count from 1 to desired number to increase widget counts.

Extending the same concept of showaddelement and maxwidgets, one can also add and increase the gadget count to any other part of your blog. For example to body, footer or side column.

Try this out to customize.

Google In Page Analytics

2011-09-23T22:50:00.000-07:00

Yet another awesome innovation from Google.A very important SEO tool, it actually helps one to visualize click views performed on a web page. Google recently launched In Page Analytic for this which can be found under Content section of Google analytic.

It enables you to visually analyze your website pages in order to assess how users interact with those pages, and helps you understand the answers to questions as per Google Analytics such as:

Is my page layout optimal for what I want users to accomplish on the page?
Are my users seeing the content I want them to see?
Are my users finding what they're looking for on the page?
Are my calls to action motivating or visible enough?
Which links are users clicking?

Here is the image for my web page:-

It's really great to see In-Page-Analytic report.

For more details one can refer :-

http://www.google.com/support/analytics/bin/answer.py?answer=178902

For SEO purpose this analysis report is very helpful, Try it out.

How to add adsense to blog using javascript

2011-09-20T01:59:00.000-07:00

Untitled Page

Google Adsense can be easily added with the help of javascript in any poart of post.

Lets look at the simple steps for doing it :-

1) Go to the edit post of your blog.

2) Select HTML edit mode.

3) Insert following javascript to your HTML.

Below is the example of leader board Adsense :-

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

google_ad_client = "ca-pub-9274462217825187"; //change your pusblisher id

google_ad_width = 728;

google_ad_height = 90;

google_ad_format = "728x90_as";

google_ad_type = "text";

google_ad_channel ="";

google_color_border = "E8E7D0"; //change background color from here

google_color_bg = "dcdcdc"; //change back ground coloe from here

google_color_link = "B96F17"; //change link color from here

google_color_url = "B96F17"; //change url color from here

google_color_text = "000000"; //change text color from here

//--></script>

src="http://pagead2.googlesyndication.com/pagead/show_ads.js">

script>

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

4) Save your post and you done with Adsense emebed into your post.

Above adsense javascript code will return some thing like below in your blog post :-

How to change the Adsense Unit Size ?

Next important point is to change the adsense layout using javascript.

Follow below step to change the :-

1) Go to the adsense javascript.

2) Change the hieght and width field , get the value of hieght and width from the image shown below:-

3) After changing the hieght and width, change the "google_ad_format" value in "width_height_as" format, example :-

google_ad_width = 336;
google_ad_height = 280;
google_ad_format = "336x280_as";

4) Just save it after changing the value, and you are ready with new Adsense unit size. Choose unit size according to your website/blog.

List of Blog Post Gadget for blogger using javascript

2011-09-18T10:37:00.000-07:00

Blogger Data API Sample

Following post will help in retrieving the information related to list of post from a blog. One can use this to display the list of blogs by following easy step mentioned below

1) Add one html/javascript gadget to your blog.

2) Copy paste below code to your gadget.

3) Replace feeduri with your blog feed uri.

var feedUri = 'http://www.blogger.com/feeds/10861780/posts/default';

4) just save the gadget and its ready to use. Here goes the code for list of post for a blog :-

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

/*
* Retrieve a list of blog posts
*/

// Obtain a reference to the 'content' div
var content = document.getElementById('content');

// Create the blogger service object
var bloggerService =
  new google.gdata.blogger.BloggerService('com.appspot.interactivesampler');

// The feed for a single blog. (In this case, the Official Google Blog.)
//
// The ID included in this URI can be retrieved from the
// <link rel="service.post"> element in the Blog's HTML source
var feedUri = 'http://www.blogger.com/feeds/10861780/posts/default';

// A callback method invoked getBlogPostFeed() returns data
var handleBlogPostFeed = function(postsFeedRoot) {
  var posts = postsFeedRoot.feed.getEntries();

  // This variable will buffer HTML output until function completes
  var html = '';

  // Display blog's title
  html += '<dl>'
+ '<dt><strong>Blog:</strong> '
+ '<a href="'
+ postsFeedRoot.feed.getLink('alternate').getHref()
+ '">'
+ postsFeedRoot.feed.getTitle().getText()
+ '</a></dt>';

  // Display blog posts
  html += '<dd><ul>';
  for (var i = 0, post; post = posts[i]; i++) {
  var postTitle = post.getTitle().getText();
  var postURL = post.getHtmlLink().getHref();
  html += '<li><a href="' + postURL + '" target="_blank">'
  + postTitle
  + '</a></li>';
  }
  html += '</ul></dd>';

  // Write out buffered HTML, and clear the "Loading..." message
  content.innerHTML = html;
};

var handleError = function(error) {
  content.innerHTML = '<pre>' + error + '</pre>';
};

bloggerService.getBlogPostFeed(feedUri, handleBlogPostFeed, handleError);

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

Below is the demo of above code for my blog :-

Postfix to Infix Algorithm

2011-09-15T10:50:00.000-07:00

I have come across one very interesting query about Postfix to Infix conversion.

Let’s understand first the importance of having Postfix notation:-

· To reduce computer memory access.

The automatic stack permits the automatic storage of intermediate results for use later: this key
feature is what permits RPN calculators to easily evaluate expressions of arbitrary complexity: they
do not have limits on the complexity of expression they can evaluate.

· To utilize the stack to evaluate expressions.

· To reduce the complexity of expression while evaluation.

· Postfix notation is often used in stack-based and concatenative programming languages.

Postfix to Infix Algorithm

Let’s look out for the algorithm for converting postfix to infix expression:-

§ While there are input symbol left

§ Read the next symbol from input.

§ If the symbol is an operand (i.e. value)

§ Push it onto the stack.

§ Otherwise, the symbol is an operator.

§ If there are fewer than 2 values on the stack

§ (Error) The user has not input sufficient values in the expression.

§ Else, Pop the top 2 values from the stack (operand1 & operand 2).

§ Put the operator, with the values as arguments and form a string (like : operand1 operator operand2).

§ Encapsulate the resulted string with parenthesis. (like: (a+b) if operand1 =’a’, operand2 =’b’, operator = ‘+’ )

§ Push the resulted string back to stack.

§ If there is only one value in the stack

§ That value in the stack is the desired infix string.

§ If there are more values in the stack

§ (Error) The user input has too many values.

Postfix to infix will not give you exact expression in terms of parenthesis, though it will give you same result on evaluation.

e.g. (a+b+c)*2
Postfix will be :- ab+c+2*
And postfix to infix will give :- (((a+b)+c)*2)

Distance Google MAP API demo

2011-09-15T00:19:00.000-07:00

Google Maps API Sample

Google Maps API Directions Illustrated

Enter Location in format #place,#city

Experimenting with google maps api, i have developed this quick utility to show the distance and duration between locations. TRY IT OUT

From:		To:
Language:
Distance:	KMs
Duration:	Minutes

Formatted Directions	Map

Distance between two locations with Google Map API

2011-09-14T06:52:00.000-07:00

One can easily calculate distance between two location with the help of Google Map APIs. Google Map APIs comes with a set of classes which helps in doing such tasks.
class GDirection, helps in getting the travel distance between the two different location.
So example shown below targets following features :-

Getting distance between two location.
Getting duration between two location.

Here goes the complete java script code for it

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

    <script type="text/javascript">

    var map;

    var gdir;

    var geocoder = null;

    var addressMarker;

    var distance;

    function initialize() {

      if (GBrowserIsCompatible()) {      

        map = new GMap2(document.getElementById("map_canvas"));

        gdir = new GDirections(map, document.getElementById("directions"));

        GEvent.addListener(gdir, "load", onGDirectionsLoad);

        GEvent.addListener(gdir, "error", handleErrors);

        setDirections("San Francisco", "Mountain View", "en_US");

      }

    }

    function setDirections(fromAddress, toAddress, locale) {

      gdir.load("from: " + fromAddress + " to: " + toAddress,

                { "locale": locale });

    }

    function onGDirectionsLoad(){ 

        // Use this function to access information about the latest load()

        // results.

        // e.g.

      distance = gdir.getDistance().meters;

      alert("Distance is : " + gdir.getDistance().meters + "and Duration Is: " +

            gdir.getDuration().seconds/60);

      document.getElementById("fdistance").innerHTML = gdir.getDistance().meters;

      document.getElementById("fduration").innerHTML = gdir.getDuration().seconds/60;

    }

    script>
 -------------------------------------------------------------------------------

Can we call GDirection without creating GMap ?
So the answer is yes, one can create GDirection without pasing GMap also.
So the output will only contain text format.
sample code
gdir = new GDirections(null, document.getElementById("directions"));
so instead of map object null is passed in above code line, it will
display direction information in only text format.
One can also use above logic to design their own Google Gadgets too.

new vs malloc ?

2011-09-11T23:33:00.000-07:00

C++ often confuses beginners with its multiple way to allocate and free memory. Most of them understand them that free must be used with malloc and delete with new. But still they are not clear with the differences. This article will help in understanding the concept behind new and malloc.

Lets see the broader level differences first :-

'new' helps in constructing an object (calls constructor), malloc does not. One of the most important differences between them.

e.g. Consider a

Class A {

public : A() { cout <<"In constructor"; }

}

A* pobjA = new A(); //it will call constructor and displays "In constructor"

A* pa = (A*) malloc(sizeof(A)); //it will not call constructor

new requires type of object to be allocated, malloc requires you to specify the total number of bytes to allocate.

operator new is an operator, malloc is a function.

operator new throws an exception if there is not enough memory, malloc returns a NULL. As both function help allocating memory dynamically, there are chances for run-time failure due to non availability of memory. For such cases both shows different behavior and hence need to be handled accordingly.

very important pint to be noticed over here is

When new is used to allocate memory for a C++ class object, the object's constructor is called after the memory is allocated.

operator new can be overloaded, malloc cannot be overloaded.

operator new/new[] must be matched with operator delete/delete[] to deallocate memory, malloc() must be matched with free() to deallocate memory.

Another big question is

How to choose between malloc and new ?

While working with C++, its always recommended to use "new", because it has additive advantage over malloc which are:-

Its type safe.
It calls constructor and helps in implementing very important Object Oriented feature Inheritence (constructor chaining).

One can though use malloc while working with buffer (non class and struct base) , which they want to resize with time with the help of realloc. But still it can be achieved with the combination new/delete too.

How much one can allocate ?

One more query one can have now is, "How much one can allocate"? The largest possible memory block malloc can allocate depends on the host system, particularly the size of physical memory and the operating system implementation. Theoretically, the largest number should be the maximum value that can be held in a size_t type, which is an implementation-dependent unsigned integer representing the size of an area of memory. The maximum value is 2power(CHAR_BIT*sizeof(size_t) − 1), or the constant SIZE_MAX in the C99 standard.

Post a Suggestion/Query

2011-09-10T21:43:00.000-07:00

Open post for adding suggestions/queries to be considered for next posting.

Queries and SuggestionsQueries and SuggestionsQueries and SuggestionsQueries and SuggestionsQueries and SuggestionsQueries and SuggestionsQueries and SuggestionsQueries and SuggestionsQueries and SuggestionsQueries and SuggestionsQueries and SuggestionsQueries and SuggestionsQueries and SuggestionsQueries and SuggestionsQueries and SuggestionsQueries and SuggestionsQueries and SuggestionsQueries and SuggestionsQueries and SuggestionsQueries and SuggestionsQueries and Suggestions

What is Hashing , HashTable, Hash Function and its collision resolution strategies

2011-09-10T11:21:00.000-07:00

Hashing is the technique used for performing almost constant time search in case of insertion, deletion and find operation. Taking a very simple example of it, an array with its index as key is the example of hash table.
So each index (key) can be used for accessing the value in a constant search time. This mapping key must be simple to compute and must helping in identifying the associated value. Function which helps us in generating such kind of key-value mapping is known as Hash Function.

Hash Table a.k.a Hash Map is a data structure which uses hash function to generate key corresponding to the associated value.

lets look at some sample hash function for strings

Folding Method:-
int h(String x, int D)
{
int i, sum;
for (sum=0, i=0; i<x.length(); i++)
sum+= (int)x.charAt(i);
return (sum%D);
}

Cyclic Shift :-
static long hashCode(String key, int D)
{
int h=0;
for (int i=0, i<key.length(); i++)
{
h = (h << 4) | ( h >> 27);
h += (int) key.charAt(i);
}
return h%D;
}

good link for hash function on string : click here

Coming to very important part of hashing , which is collision resolution. Since its always not possible to design perfect hash function with minimal overhead which would generate unique key. To address this problem following are the two main collision resolving techniques :-

1) Open Hashing also known as separate chaining

2) Closed Hashing also known as open addressing

Lets understand the difference between them

1) Open Hashing :- In this strategy collision is resolved by keeping the conflicting element in a list. That is to keep all element in a list which generate same hash.

Open Hashing

From above figure its clear that how collision get resolved by keeping a linked list.

2) Closed Hashing :- In this strategy collision is resolved by placing the conflicting element near to the slot generated by the hash function. Associated with closed hashing is a rehash strategy:

“If we try to place x in bucket h(x) and find it occupied, find alternative location h1(x), h2(x), etc. Try each in order, if none empty table is full,”

Lets take an example to understand it

HASH_TABLE_SIZE = 8

Input data :- a,b,c,d Hash for them H(a) = 0, H(b) = 3, H(c) = 7 and H(d) = 3

Now as 'c' and 'd' has same hash, where to insert 'd' then ?

Finding position using linear hashing :

h1(d) = (h(d)+1)%8 = 4%8 = 4

Adding 1 to hash function of h(d) we get new position 4, and slot 4 is currently non occupied. So entering d at position 4. In this way Closed hashing works.

Disadvantage of closed hashing is that it consumes more space as compared to open hashing

also it has less flexibility in accommodating for duplicate hash element.

Major advantage of closed hashing is that it reduces the overhead of introducing new data structure and reduces cost of new memory allocation per new element insertion.

Iterator in C++

2011-09-09T00:04:00.000-07:00

Iterator an object which help in traversing a container. Its like a navigator.
For beginners its very difficult to digest/learn Iterator after Array. Since access to array is very easy just pass an index and get the value.
So this post will help beginners to build understanding about Iterator.

To start with lets look out for simple array traversal.

const int nLength = 10;
int account[nLength] = {0};
//to traverse the array one can simply provide for loop upto length and access it by index
for(int i = 0; i< nLength; i++)
{
cout<<account[i];
}

Now lets solve the above problem if its a list container.

std::list lstAccount; //list container for account
stAccount.push_back(1);
lstAccount.push_back(2);
lstAccount.push_back(3);
lstAccount.push_back(4);
std::list::iterator lstAccountIterator;//iterator for traversing list
for(lstAccountIterator = lstAccount.begin(); //initialize iterator with begining
lstAccountIterator != lstAccount.end(); // traverse until iterator rach end
lstAccountIterator++) //move itertor to next element.
{
cout<<*lstAccountIterator; //print value at itertor
}
So above code will help in traversing a list container.
Some good article on Iterator can be found at following links
http://www.cplusplus.com/reference/std/iterator/
http://www.cprogramming.com/tutorial/stl/iterators.html
http://en.wikipedia.org/wiki/Iterator

Now moving to next level, lets understand the iterator design pattern.

Purpose:
To provide a way for accessing and traversing the collection of elements, without actually exposing the internal structure/representation of the collection organisation.

Benefits:
An abstraction which helps in simplifying the traversal mechanism.

Design Layout:

Fig. Iterator Design Pattern

Some good SEO resources , links

2011-09-06T06:06:00.000-07:00

Here are list of some good SEO resources :-

One of the best description about SEO :-
http://searchengineland.com/guide/what-is-seo

This page contain many relevant pointers -
http://www.pronetadvertising.com/articles/top-50-seo-resources.html

Good resource :-
http://www.seoconsultants.com/seo-resources/

It takes time to be consumed by crawlers, if we talk about google search engine. And it depends on many factors but focusing on the below key points are good enough for a new blogger.
Some key facts about SEO:-
1) Choose keywords (label) very effectively.
2) Do not create complex titles.
3) Leave back-links with relevant context.
4) Be consistent with post, it will help in keeping readers interested in the blog.

Keep Blogging
-Tajendra

sizeof operator , learning with experiments

2011-09-06T04:35:00.000-07:00

sizeof a very interesting operator, lets do some experiments with it to gain more understanding about it.

Lets look at the msdn definition of it first :-

Yields the size of its operand with respect to the size of type char [definition from msdn].

Now lets start experimenting with it :-

what will following statement yields

a) sizeof function ?
sizeof(&main);
sizeof(&printf);

b) sizeof an empty class ?
class A {};
sizeof(A)

c) Can sizeof return 0 ?

d) What will be the output of following program ?
int i = 1;
sizeof(i++);
cout<<"i="<<i;

e) sizeof following class ?
class A { char c; int i; };
sizeof(A)

Now lets look at them one by one

a) sizeof function ?
sizeof(&main);
sizeof(&printf);

Answer : sizeof(&main) will return 4 on 32 bit OS.
same hold true for sizeof(&printf). And the reason is very straight forward. As its returning size of function pointer.

b) sizeof an empty class ?
class A {};
sizeof(A);
Answer : Its a very interesting question which have very straight forward answer. It directly depends on sizeof operator implementation, if one looks at msdn documentation it says sizeof operator never returns zero. Considering this fact it returns 1.
For more details one can go through link (stroustrup's FAQs):-
http://www2.research.att.com/~bs/bs_faq2.html#sizeof-empty

c) Can sizeof return 0 ?
Answer : NO, sizeof operator never returns 0.

d) What will be the output of following program ?
int i = 1;
sizeof(i++);
cout<<"i="<<i;
Answer : output would be 1, sizeof operator gets resolved at compile time only, no run-time execution will be entertained for sizeof operator. So the output would be 1.

e) sizeof following class ?
class A { char c; int i; };
sizeof(A);
Answer : Don't hurry up to reply with 5 byte, because it depends on the byte alignment of class.
If it is 1 byte aligned, output would be 5;
And for 4 byte aligned, output would be 8;

Online Regular Expression / Regex Tools and Editor

2011-09-01T07:14:00.000-07:00

Some useful compiled link about online regex tester :-

Regex tester from Regular Expression Info.com

http://www.regular-expressions.info/javascriptexample.html

Interactively create and test regular expressions with RegexBuddy.
Create and analyze regex patterns with RegexBuddy's intuitive regex building blocks. Quickly test regular expressions on sample data and files in a safe sandbox. Debug regexes easily with real-time highlighting and informative regex match details. Get your own copy of RegexBuddy now.

Online regular Expression tester from PageColumn.

http://www.pagecolumn.com/tool/regtest.htm

A very fast and effective regex tester.

FileFormat.Info

http://www.fileformat.info/tool/regex.htm

Table For regular expression syntax:-
Regular Expression Syntax :- http://msdn.microsoft.com/en-us/library/1400241x(v=vs.85).aspx

CPU spike problem, here is the library

2011-07-29T00:56:00.000-07:00

If facing problem of improper CPU utilization while working with multiple core, then here is one good reference:-
http://msdn.microsoft.com/en-us/library/gg675934.aspx

Perception a boon or a killer ?

2010-03-18T11:20:00.000-07:00

Perception is considered to be starting point of thinking. In most of the cases perception starts with our experiences we have from life.

If we look thinking steps it would be:-
a) We see, observe or feel.
b) We percepts i.e. start thinking and analyzing.
c) We conclude and take actions.
<p>&amp;amp;lt;p&amp;amp;gt;&amp;amp;lt;p&amp;amp;gt;&amp;amp;lt;p&amp;amp;gt;&amp;amp;amp;lt;p&amp;amp;amp;gt;&amp;amp;amp;amp;amp;lt;br /&amp;amp;amp;amp;amp;gt; &amp;amp;amp;lt;/p&amp;amp;amp;gt;&amp;amp;lt;/p&amp;amp;gt;&amp;amp;lt;/p&amp;amp;gt;&amp;amp;lt;/p&amp;amp;gt;</p>

Most of us just ignore the step (b), which i want to highlight with examples and will see some steps to improve this.

Lets take an example of one short story showing perception role in real life:-
In Australia, the one dollar coin is much bigger than two dollar coin. One day, one big guy and his friend offered five-year old Johnny a choice between two coins: a one dollar coin and the small two dollar coin. He could take and keep whichever one he wanted.He picked the bigger, one dollar coin.His friends laughed and giggled.Whenever they wanted to tease Johnny they offered him again this choice of coins.He always took the bigger one.He never seemed to learn.
One day an adult saw this and called Johnny over.He told Johnny that although the smaller coin was smaller it was actually worth more."I know that", said Johnny. The adult man just got stunned from his answer. Johnny added "If i had taken smaller one first time, then how often they will offer me again".

With the above example it's very clear that perception made by big guys for that small kid was absolutely wrong. And utilizing same perception kid actually got the benefit.This example reveals us that don't precept that you are the most intelligent and the "only one".Always keep in mind that you cant fool people all the time. So be very cautious in case you start perceiving things.

Lets take one more practical example.

This is a small story indicating how perception can change with time and circumstances.

Rishita joined college after stepping out of school world. She made few friends and Pinky was one of them. They soon became good friends and shared a small world together of friendship and trust with lots of fun and enjoyment. One day Rishita was not feeling well so she asked Pinky to submit her assignment on her behalf, as the assignment marks were to be added to final score.

She was relieved that her assignment will be submitted on time. But next day she came to know that her assignment was not submitted and even Pinky was absent.
Rishita felt cheated and was very annoyed over Pinky. More important was that Pinky didn't even contact her once. One week passed by and Pinky joined back but Rishita decided not to talk to her. She created a perception for her and acted accordingly. Pinky tried to contact her many times but all in vein.

Few months passed by. Rishita was talking to one of her classmate and when Pinky was mentioned, she suddenly came up with an abrupt remark on Pinky's credibility. Then her classmate asked the reason for such comment and Rishita told her everything. Then her classmate broke her perception by telling truth about Pinky's unavailability.The second side of story gave Rishita shock of her life.

The day Pinky was going to submit Rishika's submission, her younger brother had a bad road accident and she was occupied for nearly 2 weeks with her brother's recovery. This was the reason she couldn't even inform Rishita. when she joined back she tried to contact Rishita, but Rishita's perception deprived her of the best friend she had.

At this time she realized that her wrong perception due to a single incident and incomplete information cost her best friend she had.

This example reveals that perception if made wrong can be a killer.

A perception taken at a time plays very important role in real life situation.
As we saw perception taken by big guys was totally different from kids perception.
To kid perception made by big guys was a boon to him. We also seen
perception can make or break friendship.

Lets take one more example to understand that perception is a boon or a killer?

An old man of ninety goes down to Hell. As he wonders around he sees a friend of his, about the same age, with the most beautiful young woman on his knee.
He ask, "Is this hell? You seem to be having a good time."
The friend replies, "it is indeed hell, i am the punishment for the young lady."

This humorous example shows that perception can vary from people to people and its very difficult to get the right one. If you apply logic then also its difficult to create right perception. Perception as we seen can be a boon or it can be killer at times. So, just be careful whenever you precept things, try to add more and more dimensions to your thinking process before taking an action.

Hope you enjoyed reading the post.

Keep Rocking,
-Tajendra