Finite Automata with Thundax P-Zaggy part I

I have moved forward the development of Thundax P-Zaggy with the addition of a Finite Automata builder and simulator. "A deterministic finite automaton (DFA) also known as deterministic finite state machine is a finite state machine that accepts/rejects finite strings of symbols and only produces a unique computation (or run) of the automaton for each input string. (wikipedia)". Building the automata with P-Zaggy is quite simple, so let's start by building a DFA for the following language: 

L = {ba | abⁿa, n > 0}.

As it is shown in the previous image, the DFA would be as follows:

With the tool we would be able to create our diagrams placing the states and transitions. Once the diagram is set up, all transitions need to have the transition string to change the ongoing state and initial and final states need to be selected (using right click and selecting "Mark as Start Node" for Initial state and "Mark as End Node" for Final state).

We can start the simulation with very simple steps. Firstly, select the tab called "Finite Automaton (simulation)" and enter the test input string to test. Then press start button to internally initialize the graph as a DFA and press step to process every character of the input string while the diagram is changing states and showing you which is the actual state and whether the string is being accepted or rejected. To set up a single loop transition, select the node and with right click select "Set connector loop" and add text for the transition.

In this beta version, we can also use Regular Expressions in our transitions thanks to the widespread use of regular expressions inside Delphi XE. 

From the same screen we can test our regular expressions and check whether if they match or not. There are still some issues to tackle like "empty string" and other considerations that I would be delving into detail in the following days. I am also working on a Layered-Tree-Draw Algorithm using Reingold-Tilford Algorithm and the enhancement of the better recognition of more complex regular expressions.

Have a look at this preview of the functioning of the graph, it is really worth it:

Stay tuned and give P-Zaggy a try from here:

• Thundax P-Zaggy v1.2.0 build 155. (there are two examples included).

Related links:

• Regular language closure properties.
• VLO Framework.
• Thundax P-Zaggy presentation.
• Thundax P-Zaggy 1.2 beta.
• Regular Expressions.

Install multiple instances of the same Delphi application service

In this article you will find an example on How to install multiple instances of the same Delphi application service under Windows. This topic was raised a few years ago in StackOverflow and I have decided to give more details about how to use multiple instances of the same service.

The service needs to be unique in name and the best way to sort this out is using a parameter to describe the service in a unique way. The service itself will use this parameter to compose its name even though it is using the same  executable. In this example I will identify the services when installing the service using the command line with the following instruction: "myService /install Param1". Param1 will be used to compose the internal service name as myServiceParam1. If we want to use another instance, just install a second service with a different param name as: myService /install Param2.

To achieve this is pretty simple, just create the service using your Delphi XE and then create the methods ServiceBeforeUninstall and ServiceCreate:

Notice the System.ParamStr(2) that will use the second parameter which was input from the command line. The first parameter is the /install command needed to install the service.

After the execution of the following commands:

myService /install Param1
myService /install Param2

You will see two installed services using the same executable:

To uninstall them, use the opposite command:

myService /uninstall Param1

myService /uninstall Param2

But this is not ending here. Now the services are installed, but neither the service name is set nor the description. To achieve this, we need to use the ChangeServiceConfig functions from WinSvc - Service Control Manager unit.

Have a look at the complete source code:

This solution is using the example provided by koochangmin on his Delphi blog. If you have a closer look at the ServiceAfterInstall method, you will find the composition of the name and description which will be used to populate the values in the service:

That is the way the service needs to be created in order to let the application use the parameters in runtime.

If you have any problem uninstalling the services, just use the SC command to delete the service:

sc delete ServiceExampleParam1

Related links:

• Windows Service Managing Unit.
• ChangeServiceConfig2 function.
• Another Windows Service: A supplementary note.
• How to delete a service.

Google and Facebook "Secrets" unveiled

Here you can see an interesting video from one of the TED talks this year in which we can see how the information is filtered and presented according to our surfing (using algorithmic and personalized filters). It gives interesting reflections.

Enjoy the video!.

Monitoring Desktop Heap Memory and troubleshooting issues (part II)

Now that we know what Desktop Heap Memory is and How works (Monitoring Desktop Heap Memory and troubleshooting issues (part I)), we can extend this functionality and retrieve the Heap size from our Delphi app and even better, create a new desktop with a specified heap size.

To achieve this I am going to use the public API functions introduced in Windows Vista: CreateDesktopEx, which allows the caller to specify the size of desktop heap.And, GetUserObjectInformation that includes a  flag for retrieving the desktop heap size (UOI_HEAPSIZE).

Get Heap Size:

To get the heap size, we just need to invoke the GetUserObjectInformation using the UOI_HEAPSIZE flag:

procedure GetHeapSizeClick();
var
  HDesktop: HDESK;
  UHeapSize: ULong;
  tempDword: DWORD;
begin
  HDesktop := OpenInputDesktop(0, False, DESKTOP_CREATEMENU or
    DESKTOP_CREATEWINDOW or DESKTOP_ENUMERATE or DESKTOP_HOOKCONTROL or
    DESKTOP_WRITEOBJECTS or DESKTOP_READOBJECTS or DESKTOP_SWITCHDESKTOP or
    GENERIC_WRITE);

  GetUserObjectInformation(HDesktop, UOI_HEAPSIZE, @UHeapSize, SizeOf(UHeapSize), tempDword);
  OutputDebugString(PChar('UOI_HEAPSIZE ' + Inttostr(UHeapSize)));
  CloseDesktop(HDesktop);
end;

The output of the string is as follows:
Debug Output: UOI_HEAPSIZE 12288 Process Project1.exe (4224)

Where the value highlighted in bold, is the predefined size of your heap in the SubSystems\Windows registry key.

Create a new desktop with a specific heap size:

Using the CreateDesktopEx or CreateDesktopExW (Unicode):

var
  HDesktopglobal: HDESK;

procedure CreateDesktop();
var
  UHeapSize: ULong;
  tempDword: DWORD;
begin
  try
    HDesktopglobal := CreateDesktopExW('Z', nil, nil, DF_ALLOWOTHERACCOUNTHOOK, GENERIC_ALL, nil, 3052, nil);
  except
    on e: exception do
      ShowMessage(SysErrorMessage(GetLastError));
  end;
  if HDesktopglobal <> 0 then
  begin
    GetUserObjectInformation(HDesktopglobal, UOI_HEAPSIZE, @UHeapSize, SizeOf(UHeapSize), tempDword);
    OutputDebugString(PChar('UOI_HEAPSIZE ' + Inttostr(UHeapSize)));
  end;
end;

procedure CloseDesk();
begin
  CloseDesktop(HDesktopglobal);
end;

We can check the result with dheapmon tool:

With more details using dheapmon -v and the looking for 'Z' desktop.

The output of the string is as follows:

Debug Output: UOI_HEAPSIZE 3052 Process Project1.exe (364)

Remember that the Desktop needs to be closed.

Related links:

• Desktop heap.
• GetUserObjectInformation.
• CreateDesktopEx.

Open a list of URLs

Going on with my previous entries, in this post I am releasing a little tool to open a web browser (in this case google chrome) and populate it with a list of stored URLs. This tool would be the culmination of the articles: My first Google Chrome extension (Get all URLs from Google Chrome tabs) and Get Chrome active tab URL using Delphi. And as you know, I love automating and when I am surfing the internet I like keeping track of my URLs and being able to retrieving and saving them easily.

You can download the tool from here. The tool only needs the path to your browser (in my case google chrome) and a list of pre-saved urls (for example the output list from my chrome extension).

The tool looks like this:

And it uses the ShellExecute function from ShellAPI.

Enjoy it!.

Related Links:

• Open browser.