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30Aug/100

How to declare pointer to member function ?

Today while browsing at CP MFC forums, I find these two reply intresting for problem mentioned in title.

Aescleal replied:-

Member function pointers are really handy when you want to call the same member function on every element of a collection. It's either that or write a shim functor to do the call for you. So instead of:

class functor{ 
   public:      
  void operator()( object &obj )   
     {            obj.A();        }
};
std::for_each( data.begin(), data.end(), functor() );

you can use:

std::for_each( data.begin(), data.end(), std::mem_fun_ref( &object::A ) );

The first form is a real pain in the neck before C++0x as you can't define a local class or use a lamda. Your functor has to be defined "somewhere else" which can lead to a bit of flow interruption when you're reading code (for me anyway, your experience probably differs).

SuperMan replied:-

Consider the class -

class A{
    public:    void One() {}
};

Declaring and initializing a member function pointer would be -

void (A::*pmfn)() = &A::One;

Calling the method using the function pointer would be -

A obj;(obj.*pmfn)();

OR

A* ptr = new A;(A->*pmfn)();
Filed under: General No Comments
10Aug/100

String Manipulation!

Today I found a interesting post at CP, which states

"I've given a string like this:"S R Tendulkar". I've to get the third part in the string ie "Tendulkar" and randomly rearrange or replace the characters between 'd' to 'r'. ie I've to display "SR Tendulkar" as "S R Tendalkur" or as "S R Tendelker". My string is a std::string. How to do this?"

Aescleal commented as following :-

std::transform takes a range over which you want to do something, a destination and what you want to do. So if you wanted to convert all vowels to the next in a sequence you could do something like:

std::pair<char, char> vowel_step =
{
   std::pair<char, char> ( 'a', 'e' ),
   std::pair<char, char> ( 'e', 'i' ),
   std::pair<char, char> ( 'i', 'o' ),
   std::pair<char, char> ( 'o', 'u' ),
   std::pair<char, char> ( 'u', 'a' )
 };

std::map<char, char> vowel_map( &vowel_step[ 0 ], &vowel_step[ 5 ] );

class vowel_transformer
{
 public:
 char operator()( char c )
 {
   std::map<char, char>::const_iterator iter( vowel_map.find( c ) );
   if( iter != vowel_map.end() )
           return iter->second;

   return c;
 }
};

std::string aesc( "aescleal" );
std::transform( aesc.begin(), aesc.end(), aesc.begin(), vowel_transformer() );

That should convert "aescleal" into "eiscliel". To get the effect you want define a class to do the tranformation on a per-character basis and work out the range you want to operate on.

Filed under: General, STL No Comments
19Jul/100

Using IComparer interface in Managed C++!

IComparer is an useful interface provided to programmer to sort collection according to programmer wish. IComparer has one virtual function which need to be overload by programmer to sort.

Class T<>
virtual int Compare(T x, T y)

Here is mine custom implementation to sort array/list in desending way.

using namespace System::Collections::Generic;

ref class RevCompare:public IComparer&lt;int&gt;
{
public:
 
 virtual int Compare(int x, int y)
    {
            if (x &gt; y)
                return -1;
            else
                if (x == y)
                    return 0;
                else
                    return 1;
     };

};

points to remember while implementing managed interface :-

  1. Put ref before class, otherwise it treat it as unmanaged class.
  2. implemented function should be preceded by virtual keyword, if not you will receive following error.

“error C3766: 'RevCompare' must provide an implementation for the interface method 'int System::Collections::Generic::IComparer<T>::Compare(int,int)'”

Code Snippet:-


using namespace System;
using namespace System::Collections::Generic;

ref class RevCompare:public IComparer<int>
{
public:

 virtual int Compare(int x, int y)
    {
            if (x > y)
                return -1;
            else
                if (x == y)
                    return 0;
                else
                    return 1;
     };

};

int main(array<System::String ^> ^args)
{

System::Collections::Generic::List<int> intList = gcnew List<int>();

	intList.Add(7);
	intList.Add(4);
	intList.Add(3);
	intList.Add(10);
	intList.Add(19);
	intList.Add(20);
	intList.Add(12);

	Console::WriteLine(L"Before Sorting");

	List<int>::Enumerator^ enumIt = intList.GetEnumerator();

	while(enumIt->MoveNext())
	{
		Console::WriteLine(L"{0}",enumIt->Current);
	}

	Console::WriteLine(L"After Sorting");

	intList.Sort(gcnew RevCompare());
	enumIt = intList.GetEnumerator();

	while(enumIt->MoveNext())
	{
		Console::WriteLine(L"{0}",enumIt->Current);
	}

    return 0;
}

Output:-

Before Sorting
7
4
3
10
19
20
12
After Sorting
20
19
12
10
7
4
3

Filed under: General, Managed VC No Comments
11Jul/100

IPC: Using Memory Mapped Files!

There are many ways you can do inter-process communication in unmanaged world. One of them is data sharing using memory mapped files. Here how’s it work.

Server Application:-

  1. Create File Handle using CreateFileMapping.
  2. Use MapViewOfFile function to get starting address of shared memory address.
  3. Use Starting address pointer receieved in last step to update information you want to share.
  4. Once done,use UnmapViewOfFile to release shared memory.
  5. Use CloseHandle Api to close file Handle.

Client Application:-

  1. Open File Handle using OpenFileMapping.
  2. Use MapViewOfFile function to get starting address of shared memory address.
  3. Use Starting address pointer receieved in last step to update information you want to share.
  4. Once done,use UnmapViewOfFile to release shared memory.
  5. Use CloseHandle Api to close file Handle.

Code Snippet (Server Side):-

 HANDLE m_hMemoryMappedFile=NULL;
 TCHAR *m_pFileBuff  = NULL;
 m_hMemoryMappedFile = CreateFileMapping(INVALID_HANDLE_VALUE,
           NULL,
           PAGE_READWRITE,
           0,
           100,
           L"SHARED_FILE_{E2128B79-1C09-4805-9330-1420E19D87E1}");

 if(m_hMemoryMappedFile == NULL)
 {
  MessageBox(_T("CreateFileMapping fails"));
 }

 m_pFileBuff = (LPTSTR)MapViewOfFile(m_hMemoryMappedFile,
          FILE_MAP_ALL_ACCESS,
          0,
          0,
          100); // Buffersize 100

 if(m_pFileBuff== NULL)
 {
  MessageBox(_T("MapViewOfFile fails"));
 }

Code Snippet (Client Side):-

 HANDLE m_hMemoryMappedFile=NULL;
 TCHAR *m_pFileBuff  = NULL;

 m_hMemoryMappedFile = OpenFileMapping(FILE_MAP_ALL_ACCESS,
            FALSE,  
               L"SHARED_FILE_{E2128B79-1C09-4805-9330-1420E19D87E1}");

 if(m_hMemoryMappedFile == NULL)
 {
  MessageBox(_T("CreateFileMapping fails"));
 }

 m_pFileBuff = (LPTSTR)MapViewOfFile(m_hMemoryMappedFile,
          FILE_MAP_ALL_ACCESS,
          0,
          0,
          100);

 if(m_pFileBuff== NULL)
 {
  MessageBox(_T("MapViewOfFile fails"));
 }

Code Snippet (Data Sharing):-

Saving:-
  SetDlgItemText(IDC_EDIT1,m_pFileBuff);

 //Retrieving:-
     GetDlgItemText(IDC_EDIT1,m_pFileBuff,100);

Code Snippet (On Close) :-
  

 

UnmapViewOfFile(m_pFileBuff);
 CloseHandle(m_hMemoryMappedFile);

Preview:-

Data exchange using shared memory!

Filed under: General, IPC, Win32 No Comments
5Jul/100

Plot4: Smart Device Game!

Out of hobby, I am making application(s) on window based smart devices. I opened Visual Studio 2008 (though I have VS2010 too, but I haven’t installed it’s fully) and selected smart device project targeting Mobile-Phone/Pocket-PC SDK. I am surprise to see almost same set of class I used for developing window application, however they are tear down version of same (removing memory intensive API’s or windows pc specific API’s).

All the programming design and architecture are similar to that of programming on window pc, however background implementation is different. So here is my first successful implemented mobile app, it’s a Game, yes it is  . Players have to position four consecutive coins in horizontal, diagonal or vertical direction to win the game. Example:-

Game Picture
Game Winning Condition

 

Here is  little glimpse of my logic (it’s very beginner-ish ), there might be much better logic around, however I am not seasoned game programmer and I am open to any comments and  improvements suggestion.

I have created a 9*8 matrix for holding falling coin. Matrix can have following values only:-

enum EPlayerCoin {eCoinEmpty,eCoinPlayerOne,eCoinPlayerTwo};
#define X_MAX 9
#define Y_MAX 8
EPlayerCoin m_eGameMatrix[X_MAX][Y_MAX];

Games start with matrix containing eEmptyCoin, one by one player chose a particular column to drop its coloured coin, this game would continue till all the places are filled or either of player come victories.

For every successful coin drop, app would checks it’s diagonally, horizontally and vertically in matrix for four consecutive coins for winning condition. Here is the logic :-

bool CChildView::CheckMatrixForResult(int a_iX, int a_iY)
{
EPlayerCoin eTmp = m_eGameMatrix[a_iX][a_iY];
int i=0,j=0;
bool bFlag = true;
#ifdef _DEBUG
CString strDebugMsg;
#endif

//Check LEFT to RIGHT in batch of 4
for(i=a_iX-3;i&lt;=a_iX;i++)
{

#ifdef _DEBUG
strDebugMsg.Format(_T("PLT4(LEFT2RIGHT) StartI=[%d]\n"),i);
OutputDebugString(strDebugMsg);
#endif

//check for array break condition
if(i&lt;0)
{
continue;
}

for(j=i;j&lt;=i+3;j++)
{
#ifdef _DEBUG
strDebugMsg.Format(_T("m_eGameMatrix[%d][%d]\n"),j,a_iY);
OutputDebugString(strDebugMsg);
#endif
//check for array break condition
if(j&gt;X_MAX)
{
bFlag = false;
break;
}

if( m_eGameMatrix[j][a_iY]!=eTmp)
{
bFlag = false;
break;
}
}

/// check for game winning condition!
if(bFlag== true)
{
#ifdef _DEBUG
OutputDebugString(_T("Game Won Right Left"));
#endif
// Game Won.
return true;
}

//Set flag condition to true
bFlag = true;
}

//Check UP AND Down in batch of 4
bFlag = true;
for(i=a_iY-3;i&lt;=a_iY;i++)
{
#ifdef _DEBUG
strDebugMsg.Format(_T("PLT4(UP2DOWN) StartI=[%d]\n"),i);
OutputDebugString(strDebugMsg);
#endif
//check for array break condition
if(i&lt;0)
{
continue;
}
for(j=i;j&lt;=i+3;j++)
{
#ifdef _DEBUG
strDebugMsg.Format(_T("m_eGameMatrix[%d][%d]\n"),a_iY,j);
OutputDebugString(strDebugMsg);
#endif
//check for array break condition
if(j&gt;Y_MAX)
{
bFlag = false;
break;
}
if( m_eGameMatrix[a_iX][j]!=eTmp)
{
bFlag = false;
break;
}
}
/// check for game winning condition!
if(bFlag== true)
{
#ifdef _DEBUG
OutputDebugString(_T("Game Won UP - DOWN"));
#endif
// Game Won.
return true;
}
//Set flag condition to true
bFlag = true;
}
//Check LEFT UP to RIGHT Bottom in batch of 4
bFlag = true;
for(i=a_iX-3,j=a_iY-3;i&lt;=a_iX;i++,j++)
{
#ifdef _DEBUG
strDebugMsg.Format(_T("PLT4(UPLEFT_2_BOTTOMRIGHT) tartX,Y=[%d][%d]\n"),i,j);
OutputDebugString(strDebugMsg);
#endif
//check for array break condition
if((i&lt;0)||(j&lt;0))
{
continue;
}
for(int x=i,y=j;x&lt;=i+3;x++,y++)
{
#ifdef _DEBUG
strDebugMsg.Format(_T("m_eGameMatrix[%d][%d]\n"),x,y);
OutputDebugString(strDebugMsg);
#endif
//check for array break condition
if(x&gt;X_MAX)
{
bFlag = false;
break;
}
if(y&gt;Y_MAX)
{
bFlag = false;
break;
}
if( m_eGameMatrix[x][y]!=eTmp)
{
bFlag = false;
break;
}
}

/// check for game winning condition!
if(bFlag== true)
{
#ifdef _DEBUG
OutputDebugString(_T("Game Won UpLeft - Bottom Right"));
#endif
// Game Won.
return true;
}
//Set flag condition to true
bFlag = true;
}
//Check LEFT Bottom to RIGHT UP in batch of 4
bFlag = true;
for(i=a_iX-3,j=a_iY+3;i&lt;=a_iX;i++,j--)
{
#ifdef _DEBUG
strDebugMsg.Format(_T("PLT4BOTTOMLEFT_2_BOTTOMUP) StartX,Y=[%d][%d]\n"),i,j);
OutputDebugString(strDebugMsg);
#endif
//check for array break condition
if((i&lt;0)||(j&gt;Y_MAX))
{
continue;
}
for(int x=i,y=j;x&lt;=i+3;x++,y--)
{
#ifdef _DEBUG
strDebugMsg.Format(_T("m_eGameMatrix[%d][%d]\n"),x,y);
OutputDebugString(strDebugMsg);
#endif
//check for array break condition
if(x&gt;X_MAX)
{
bFlag = false;
break;
}

if(y&lt;0)
{
bFlag = false;
break;
}

if( m_eGameMatrix[x][y]!=eTmp)
{
bFlag = false;
break;
}
}

/// check for game winning condition!
if(bFlag== true)
{
#ifdef _DEBUG
OutputDebugString(_T("Game Won BottomLeft - UpRight"));
#endif
// Game Won.
return true;
}

//Set flag condition to true
bFlag = true;
}
return false;
}

And here are the game files :-

These files are release as part of CPOL license, you must use it at your own risk! This is without any warranty and gurantee.

Filed under: General, Smart Device, Win32 No Comments
1Jul/100

Is there is any way to convert ASM program into C or C++ code?

Yes you can, there are many third party software available on internet, some of them are :-

This is not a advertisement, there might be more tool available on Internet. would update the list once find more!

Filed under: General, Win32 No Comments
1Jul/100

C# typeof in Managed C++

There are two ways to find type of any DataType, those are :-

  1. __typeof
  2. DataType::typeid

Read more here

Filed under: General No Comments
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