Dennis Ritchie

http://www.nytimes.com/2011/10/14/technology/dennis-ritchie-programming-trailblazer-dies-at-70.html 

No doubt, comparisons will be made with Steve Jobs and how much media buzz was created.

iPhone has had a huge impact in my life, but not as much as C. C has defined my thinking. During college, most of the programming I did was in C and K&R was THE reference book I had with me most of the time (I still have it). The precise and succinct way the book is written helped me appreciate the beauty of coding. Every function was defined in clear and concise terms. That not only guided me in my programming adventures, but somehow it also helped me put a different perspective around life and accumulate a no-nonsense attitude of holding myself to much higher standards than anyone else.

From the article linked above:

Colleagues who worked with Mr. Ritchie were struck by his code — meticulous, clean and concise. His writing, according to Mr. Kernighan, was similar. “There was a remarkable precision to his writing,” Mr. Kernighan said, “no extra words, elegant and spare, much like his code.”

In essence, this guy created something wonderful and powerful in the world of computing. And I hope his legacy lives on.

-Gaurav Gupta

Puzzler: Prisoners and Hats and a Jungle, Oh My!

This puzzler was mentioned in Car Talk sometime ago and I really liked it. In brief, it goes like this:

A prison has 30 prisoners sentenced to be executed and the warden, who has the authority to pardon, decides to give them a chance to escape the punishment. He will stand all the prisoners in a straight line with each prisoner able to see the heads of all prisoners in front of him but not of those behind him. Next, he will put either a white or black hat on each prisoner’s head and ask them to guess the color of their hat one by one (starting with the 1st prisoner in the back of the line who can see all 29 other prisoners’ heads). If he guesses correctly, he’s pardoned. What is the strategy that the prisoners can use to maximize their chances of being pardoned?

The answer I came up with was grossly wrong so when these guys gave the answer (link to which I’m not posting here but can be found easily), I was intrigued. When listening to the answer, it sounded very simple but when I actually thought about it some more, I had to listen to it again to understand the strategy. For example, does the current prisoner need to know all the previous guesses or only the most previous guess?

I decided to write a simple program for this. The line of prisoners here is a StringBuffer of predefined size (in this case, 30) that is randomly filled with ‘B’ or ‘W’ chars. The objective is to write a method that will be called for each character in the StringBuffer with all the previous guesses (as a String) and remaining series (as a String). The method has to return the current character and should be implemented in such a way as to maximize the correct answers. Here’s the code:

   1: import java.util.Random;

2: public class Test {

3: static int SIZE = 30;

4:

5: public static void main(String[] args){

6: int correctGuesses = 0;

7: StringBuffer pRow = new StringBuffer(SIZE);

8: StringBuffer prevGuesses = new StringBuffer(SIZE-1);

9: char currGuess;

10:

11: Random rnd = new Random(System.currentTimeMillis());

12: //---print the series

13: System.out.print("Series:\t");

14: for (int i=0;i<SIZE;i++){

15: if (rnd.nextInt(2) == 0) //0=black, 1=white

16: pRow.append('B');

17: else pRow.append('W');

18: System.out.print(pRow.charAt(i) + " ");

19: }

20: //---strategy

21: System.out.print("\nStrat:\t");

22:

23: for (int i=0;i<SIZE;i++){

24: currGuess = guessStrategy(prevGuesses.toString(),pRow.substring(i+1));

25: System.out.print(currGuess + " ");

26: if(currGuess == pRow.charAt(i)) correctGuesses++;

27: prevGuesses.append(currGuess);

28: }

29: System.out.print("\nCorrect Guesses=" + correctGuesses);

30: }

31: 

32: public static char guessStrategy(String prevGuesses, String remArr){

33: //random

34: Random rnd = new Random(System.currentTimeMillis());

35: if (rnd.nextInt(2) == 0) //0=black, 1=white

36: return 'B';

37: else return 'W';

38: }

39: }

First, I generate the series and print it (lines 13-19). And then I call the guessStrategy method for each character in the series with all the previous guesses and the remaining series. But currently, there is no strategy and each time, it randomly returns ‘B’ or ‘W’. And obviously, result is that correct guesses average around 15. Your job, should you decide to accept this assignment is to provide a better implementation of the guessStrategy method which maximizes the chances of guessing correctly. If you’re stuck, you can look at the Car Talk website or search on internet to find the answer and then try to implement it.

I’ll post my implementation of the method in a few days. Hopefully it provides enough of a challenge to some people to work on this besides their otherwise busy life.

Friday Lunch: Content-Type, Content-Disposition HTTP Headers and MIME type handling in IE

We have a scripting tool that is used to create web-based scripts that simulate application scenarios. These scripts are run through a monitoring tool on a continuous basis to assess the health of these applications. The scripts & scripting tool are also used to validate the scenarios if the monitoring tool issues an alert. The scripting tool uses IE to run the HTTP request/response scenarios. When recording the script for a recent new application, it was noticed that after submitting the request which was an HTTP POST with XML data, the tool was bringing up a dialog box to save the response file, something you’d get when clicking on a HTML link in the browser to a file (maybe a word .doc etc) and if you don’t have an application to open that kind of file. We checked the response and it contained a standard XML that should usually be displayed within the browser (like if you click on Amazon’s AWS service). The fact that it was bringing up a download prompt and not displaying the XML in the browser was a problem because the non-technical team that uses it to validate the application will not be able to determine whether the script ran successfully or not.

The application is a servlet that takes the initial POST request and returns an XML response. After further investigation with the tool and looking at the response headers, it was found that the application was returning “application/x-www-form-urlencoded” in “Content-Type” header erroneously. I haven’t found something specific that would say that content type is not correct for HTTP response, but it is more common to use this content type when submitting form-submission data that is URL encoded (see here).

Investigating with WebScarab

My first conjecture was that the file download prompt was being displayed because of this Content-type header’s value. If we could intercept the response and replace its value with something like “text/xml”, the tool or browser will be able to display the content within the application instead of bringing up the file download prompt. And to validate that, I used WebScarab to intercept the request/responses. But for some reason (maybe because of invalid Content-Type header), it didn’t intercept the response. It would intercept the request and after accepting, it would just complete the request and we’ll end up seeing the file download prompt in the tool. Clearing the “Only MIME-Types matching:” didn’t help.

So the workaround was to write a BeanShell script within WebScarab to replace the “Content-Type” header with a proper value instead of manually intercepting the response. That turned out to be quite straightforward. All we needed to do was put:

response.setHeader("Content-Type","text/xml");

in WebScarab’s Bean Shell interface under the fetchResponse method. As is obvious, this replaces the value of Content-Type header in the response to “text/xml”.

Once we tried it out, it worked and the browser displayed the XML response without bringing up the file download prompt. This proved that the Content-Type header was the problem. But what exactly was the problem? What makes the browser display a prompt to the user to download a file instead of just displaying the content? Further searching revealed this article: http://www.jtricks.com/bits/content_disposition.html

So basically the Content-Disposition header along with Content-Type specifies the MIME type of the file returned and whether the browser should display it or prompt the user to download it. The RFC has all the details but the gist is that the Content-Disposition header can be set to “attachment” for the browser to display the file download prompt. But the response we were getting didn’t have a Content-Disposition header. And IE was still displaying the file download prompt. Further reading warranted.

How does IE handle MIME types in a response, anyways?

I kept on searching and reading on how and when a browser brings up the file dialog prompt. The Content-Type header still bothered me. Then I came across this MSDN article: MIME Type Detection in IE. It provides details on what steps IE takes to detect the content-type of the content before deciding what to do with the file:

The purpose of MIME type detection, or data sniffing, is to determine the MIME type (also known as content type or media type) of downloaded content using information from the following four sources:

• The server-supplied MIME type, if available
• An examination of the actual contents associated with a downloaded URL
• The file name associated with the downloaded content (assumed to be derived from the associated URL)
• Registry settings (file name extension/MIME type associations or registered applications) in effect during the download

If you look at the known MIME types for FindMimeFromData, “application/x-www-form-urlencoded” is not one of them. It is also not an ambiguous MIME type ("text/plain," "application/octet-stream," an empty string, or null) either. So with the MIME type as unknown,

If the "suggested" (server-provided) MIME type is unknown (not known and not ambiguous), FindMimeFromData immediately returns this MIME type as the final determination.

And what happens after that is in this MSDN article: Handling MIME Types in IE. It doesn’t mention exactly what happens if the MIME type is unknown, there’s no application associated with it in the registry and there’s no Content-Disposition header. But I’m guessing that the only thing for it left to do is to let the user decide by showing the file download prompt as was happening in our case. And we were able to prove that. I looked up the registry key for “text/xml” under HKEY_CLASSES_ROOT\MIME\Database\Content Type and added it to a new key “application/x-www-form-urlencoded”. The new registry key looked like this:

[HKEY_CLASSES_ROOT\MIME\Database\Content Type\application/x-www-form-urlencoded]
"CLSID"="{48123BC4-99D9-11D1-A6B3-00C04FD91555}"
"Extension"=".xml"
"Encoding"=hex:08,00,00,00

This tells IE that for responses received with Content-Type equal to “application/x-www-form-urlencoded”, use extension “.xml” and open it however XML files are opened (which is to display them inline). Once added, we went back to the tool and ran the script. And this time, it displayed the response xml without bringing up the download prompt.

So through this exercise, I learned about how IE displays different MIME types and about Content-Type and Content-Disposition headers.

GLaDOS is back…

So it's ok if she tries to incinerate me alive for sake of “science” but when I try to escape and torch her in the process, she gets all psyched up and starts singing sarcasm laden song?

C++ turns 25

Just wanted to share a quick link - Bjarne Stroustrup’s reflections on the 25th anniversary of C++’s first release: http://www.wired.com/thisdayintech/2010/10/1014cplusplus-released/all/1

A Generic Function to enhance BPT components

About 2 years ago, we created a set of QTP function libraries to drive the automation effort using Quality Center's Business Process Testing (BPT) functionality. What those libraries provide are a set of generic functions from clicking on a UI object to verifying an object's property, which then can be used to create both generic BPT components that can be used on any application and specific components that target a particular application or a screen within an application. We have used those libraries and components to successfully automate our application testing without much modification and maintenance.

Recently, we were using the same set of components to create/update the test cases for a new application and I took this opportunity to enhance the libraries by adding a few functions. One of them is a generic Eval function that provides some more flexibility in creating components. As we know, VBScript has its own Eval function that evaluates the provided expression and returns the result. So to be able to use that functionality from within the components, I created a new function that returns the result of that expression or the string itself if it is not an expression. Here's the function listing:

' Function EvalFunction
' ------------------
' Evals the function call specified in the parameter and returns the result
' Parameter: expr - Any VBScript expression
'@Description Evals the function call specified in the parameter and returns the result
'@Documentation Evals the function call specified in the parameter and returns the result
Public Function EvalFunction(ByVal expr)
  Dim res
  On Error Resume Next
  If (expr <> "") Then
    res = Eval(expr)
    If (Err <> 0)Then
      res = -1
      Err.Clear
    Elseif res = "" Then
      res = expr
    End If
  End If
  EvalFunction = res
  On Error Goto 0
End Function

The function itself is quite simple but it provides a lot of added functionality. I can use this function in my BPT components to evaluate any expression during run-time. And in addition, I also create a generic component that calls this function and returns the result. When I need to create a test case that needs a run-time value, I can use this component within my test cases to have that functionality.

Using the EvalFunction function in components:

For a part of our application's functionality, we had a component ("AddIP") that adds an IP to a user. Since there were 4 text fields for each of the octets, we had 4 component input parameters for each octet. In the picture below of AddIP component, each octet is a different text field (“IP1”…”IP4”) requiring a different input parameter (BrowserWebEditSet is another generic function to enter value in a WebEdit object)

But while revisiting the testing, I felt that its much easier to provide the IP parameter as a whole when you're creating a large test case where multiple IPs need to be added. So instead of having to create a new function, I just used the EvalFunction to create another component ("AddIPv2") that takes the full IP address and splits it into each octet and then enters the values as required in different text boxes. I use the VBScript “split” function to split the input parameter (the IP address) into each octet like this: "Split(""" & Parameter("IP") & """,""."",-1,vbTextCompare)(0)" which returns the 1st octet. As in the picture of the component below, I call the function 4 times for each octet which returns the result in a local parameter which I can then use to set for each text field.

So using this enhanced component, the user has to provide only the whole IP address “xxx.xxx.xxx.xxx” instead of each octet in a separate parameter.

Using the EvalFunction component in BPT tests:

The EvalFunction component is a one operation component that calls the EvalFunction and returns the result in a component output parameter. This component can be used in any test to evaluate any expression and use the result in a subsequent component.

For example, a lot of our test cases require creating a new user. Instead of specifying a fixed value for the user ID or having the tester enter a value in a run-time parameter before every run of the test, the user ID can be generated using a timestamp which guarantees its uniqueness. This is done by using the EvalFunction component. In the BPT test case below, the EvalFunction component is used with input parameter a string prefix concatenated with the current timestamp (DateFormatter is another function that returns the current date/time in appropriate format). It returns the result in a component parameter “result” which is then later used in AddUser component to create a user with that user ID. 

This way, this test can be run any number of times without requiring any modification.

Epilogue:

The function that I showed in this post is a part of the automation libraries that we created. Over time, as we use them for testing multiple applications, we have enhanced the libraries even more. These libraries, along with the BPT functionality provided by Quality Center, have helped us create reusable components that require very less maintenance. And these components are being used by testers to create and run automated test cases for different applications and different functionalities.

HP Quality Center (ALM 11.0) and REST

We are currently using Quality Center 9.2 and one of my goals for this year is to upgrade it to the latest version. While browsing through the What’s New documentation for version 11.0 (seems like it has been rebranded to Application Lifecycle Management, or ALM), I saw this line:

There are now ALM REST resources available. For details, see the HP ALM REST API Reference.

That to me is something that stood out from all the other features. Of course, from 9.2 there have been other great features added as well, like version control and flows in version 10 and Sprinter and others in 11. But being able to write clients using the REST API is a great feature and something that I definitely will be exploring once we have this version installed. I went through their REST API reference and as expected, it exposes all the entities in a RESTful way that would make it easier to write the clients in Java or any other language.

Related: a previous REST-related post