Count programs running by it's className - c++

Question

I am trying to detect how many instances of a application person is running. Did he open my application once? Twice? Thrice?
I tried to detect it by checking it's instances by process names, but in windows it is pointles - people might change .exe name and it won't count towards final number.
How would I proceed then? I thought about searching it by className (HWND?) rather by processName, but how would I do it?
This is the code I am using for detecting by process name:
int Platform::getMulticlientCount(const std::string& ProcessName)
{
PROCESSENTRY32 pe32 = { sizeof(PROCESSENTRY32) };
HANDLE hSnapshot = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);
const char *cstr = ProcessName.c_str();
int counter = 0;
if (Process32First(hSnapshot, &pe32))
{
do
{
if (_tcsicmp(pe32.szExeFile, cstr) == 0)
{
counter++;
}
} while (Process32Next(hSnapshot, &pe32));
}
CloseHandle(hSnapshot);
return counter;
}

Answer 1

The instance of the Remy:
static int counter;
BOOL CALLBACK EnumWindowsProc(HWND hwnd, LPARAM lParam)
{
char classname[MAX_PATH] = { 0 };
GetClassNameA(hwnd,classname, MAX_PATH);
if (_tcsicmp(classname, (char*)lParam) == 0)
counter++;
return true;
}
int Platform::getMulticlientCount(const std::string& ClassName)
{
counter = 0;
const char *cstr = ClassName.c_str();
EnumWindows(EnumWindowsProc, (LPARAM)cstr);
return counter;
}
If you also need to get the instance, in EnumWindowsProc:
HINSTANCE instance = (HINSTANCE)GetWindowLongPtr(hwnd, GWLP_HINSTANCE);
If you also need to get the processId, in EnumWindowsProc:
DWORD pid;
GetWindowThreadProcessId(hwnd, &pid);

Answer 2

Here is an example code that counts the instances that are running. While the application count the instances it self it does not matter if the binary is renamed. I used a file to keep the example simple but registry would work too. The only thing that is missing is a global mutex to protect the file against concurrent access. HTH
#include <iostream>
#include <thread>
#include <fstream>
#include <Windows.h>
class GlobalCounter
{
public:
GlobalCounter(const std::string& id)
: _id(id)
{
const auto filename = "C:\\users\\twollgam\\" + id + ".counter";
if (GlobalFindAtomA(id.c_str()) == 0)
{
std::ofstream(filename) << 1;
std::cout << "I am the first instance." << std::endl;
}
else
{
auto counter = 0;
std::ifstream(filename) >> counter;
++counter;
std::ofstream(filename) << counter;
std::cout << "I am the " << counter << " instance." << std::endl;
}
_atom = GlobalAddAtomA(id.c_str());
}
~GlobalCounter()
{
const auto filename = "C:\\users\\twollgam\\" + _id + ".counter";
auto counter = 0;
std::ifstream(filename) >> counter;
--counter;
std::ofstream(filename) << counter;
GlobalDeleteAtom(_atom);
}
private:
const std::string _id;
ATOM _atom;
};
int main()
{
const auto globalCounter = GlobalCounter("test");
std::cout << "Hello World!\n";
std::this_thread::sleep_for(std::chrono::seconds(30));
return 0;
}