Analysis of C ++ multi-threaded code examples

The C ++ programming language supports multithreading. So how can we implement this function correctly? Today, we will explain in detail the C ++ multi-thread application method through an example. I hope beginners can learn some knowledge based on the content we introduced.

Example of C ++ multithreading:

The main thread creates two threads t1 and t2. When the two threads are created, they are suspended. Later, they call ResumeThread to resume the execution of the two threads, call WaitForSingleObject to wait for the execution of the two threads, and then launch the main thread to end the process.

 
 

  
  
#include <stdio.h> 
  
  
#include <string> // for STL string class  
  
  
#include <windows.h> // for HANDLE  
  
  
#include <process.h> // for _beginthread()  
  
  
using namespace std;  
  
  
class ThreadX  
  
  
{  
  
  
private:  
  
  
int loopStart;  
  
  
int loopEnd;  
  
  
int dispFrequency;  
  
  
public:  
  
  
string threadName;  
  
  
ThreadX( int startValue, int endValue, int frequency )  
  
  
{  
  
  
loopStart = startValue;  
  
  
loopEnd = endValue;  
  
  
dispFrequency = frequency;  
  
  
}  
  
  
static unsigned __stdcall ThreadStaticEntryPoint(void * pThis)  
  
  
{  
  
  
ThreadX * pthX = (ThreadX*)pThis; // the tricky cast  
  
  
pthX->ThreadEntryPoint(); // now call the true entry-point-function
  
  
return 1; // the thread exit code  
  
  
}  
  
  
void ThreadEntryPoint()  
  
  
{  
  
  
for (int i = loopStart; i <= loopEnd; ++i)  
  
  
{  
  
  
if (i % dispFrequency == 0)  
  
  
{  
  
  
printf( "%s: i = %d\n", threadName.c_str(), i );  
  
  
}  
  
  
}  
  
  
printf( "%s thread terminating\n", threadName.c_str() );  
  
  
}  
  
  
};  
  
  
int main()  
  
  
{  
  
  
ThreadX * o1 = new ThreadX( 0, 1, 2000 );  
  
  
HANDLE hth1;  
  
  
unsigned uiThread1ID;  
  
  
hth1 = (HANDLE)_beginthreadex( NULL, // security  
  
  
0, // stack size  
  
  
ThreadX::ThreadStaticEntryPoint,  
  
  
o1, // arg list  
  
  
CREATE_SUSPENDED, // so we can later call ResumeThread()  
  
  
&uiThread1ID );  
  
  
if ( hth1 == 0 )  
  
  
printf("Failed to create thread 1\n");  
  
  
DWORD dwExitCode;  
  
  
GetExitCodeThread( hth1, &dwExitCode ); // should be STILL_ACTIVE = 0x00000103 = 259  
  
  
printf( "initial thread 1 exit code = %u\n", dwExitCode );  
  
  
o1->threadName = "t1";  
  
  
ThreadX * o2 = new ThreadX( -1000000, 0, 2000 );  
  
  
HANDLE hth2;  
  
  
unsigned uiThread2ID;  
  
  
hth2 = (HANDLE)_beginthreadex( NULL, // security  
  
  
0, // stack size  
  
  
ThreadX::ThreadStaticEntryPoint,  
  
  
o2, // arg list  
  
  
CREATE_SUSPENDED, // so we can later call ResumeThread()  
  
  
&uiThread2ID );  
  
  
if ( hth2 == 0 )  
  
  
printf("Failed to create thread 2\n");  
  
  
GetExitCodeThread( hth2, &dwExitCode ); // should be STILL_ACTIVE = 0x00000103 = 259  
  
  
printf( "initial thread 2 exit code = %u\n", dwExitCode );  
  
  
o2->threadName = "t2";  
  
  
ResumeThread( hth1 ); // serves the purpose of Jaeschke's t1->Start()  
  
  
ResumeThread( hth2 );  
  
  
WaitForSingleObject( hth1, INFINITE );  
  
  
WaitForSingleObject( hth2, INFINITE );  
  
  
GetExitCodeThread( hth1, &dwExitCode );  
  
  
printf( "thread 1 exited with code %u\n", dwExitCode );  
  
  
GetExitCodeThread( hth2, &dwExitCode );  
  
  
printf( "thread 2 exited with code %u\n", dwExitCode );  
  
  
CloseHandle( hth1 );  
  
  
CloseHandle( hth2 );  
  
  
delete o1;  
  
  
o1 = NULL;  
  
  
delete o2;  
  
  
o2 = NULL;  
  
  
printf("Primary thread terminating.\n");  
  
  
}
 
 

The above is an introduction to C ++ multithreading.