C++多线程的经典例子

/*  file Main.cpp
*
*  This program is an adaptation of the code Rex Jaeschke showed in
*  Listing 1 of his Oct 2005 C/C++ User's Journal article entitled
*  "C++/CLI Threading: Part I".  I changed it from C++/CLI (managed)
*  code to standard C++.
*
*  One hassle is the fact that C++ must employ a free (C) function
*  or a static class member function as the thread entry function.
*
*  This program must be compiled with a multi-threaded C run-time
*  (/MT for LIBCMT.LIB in a release build or /MTd for LIBCMTD.LIB
*  in a debug build).
*
*                                      John Kopplin  7/2006
*/

#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;
}

// In C++ you must employ a free (C) function or a static
// class member function as the thread entry-point-function.
// Furthermore, _beginthreadex() demands that the thread
// entry function signature take a single (void*) and returned
// an unsigned.
static unsigned __stdcall ThreadStaticEntryPoint(void * pThis)
{
ThreadX * pthX = (ThreadX*)pThis;   // the tricky cast
pthX->ThreadEntryPoint();           // now call the true entry-point-function

// A thread terminates automatically if it completes execution,
// or it can terminate itself with a call to _endthread().

return 1;          // the thread exit code
}

void ThreadEntryPoint()
{
// This is the desired entry-point-function but to get
// here we have to use a 2 step procedure involving
// the ThreadStaticEntryPoint() function.

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()
{
// All processes get a primary thread automatically. This primary
// thread can generate additional threads.  In this program the
// primary thread creates 2 additional threads and all 3 threads
// then run simultaneously without any synchronization.  No data
// is shared between the threads.

// We instantiate an object of the ThreadX class. Next we will
// create a thread and specify that the thread is to begin executing
// the function ThreadEntryPoint() on object o1. Once started,
// this thread will execute until that function terminates or
// until the overall process terminates.

ThreadX * o1 = new ThreadX( 0, 1000000, 20000 );

// When developing a multithreaded WIN32-based application with
// Visual C++, you need to use the CRT thread functions to create
// any threads that call CRT functions. Hence to create and terminate
// threads, use _beginthreadex() and _endthreadex() instead of
// the Win32 APIs CreateThread() and EndThread().

// The multithread library LIBCMT.LIB includes the _beginthread()
// and _endthread() functions. The _beginthread() function performs
// initialization without which many C run-time functions will fail.
// You must use _beginthread() instead of CreateThread() in C programs
// built with LIBCMT.LIB if you intend to call C run-time functions.

// Unlike the thread handle returned by _beginthread(), the thread handle
// returned by _beginthreadex() can be used with the synchronization APIs.

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 );

// The System::Threading::Thread object in C++/CLI has a "Name" property.
// To create the equivalent functionality in C++ I added a public data member
// named threadName.

o1->threadName = "t1";

ThreadX * o2 = new ThreadX( -1000000, 0, 20000 );

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";

// If we hadn't specified CREATE_SUSPENDED in the call to _beginthreadex()
// we wouldn't now need to call ResumeThread().

ResumeThread( hth1 );   // serves the purpose of Jaeschke's t1->Start()

ResumeThread( hth2 );

// In C++/CLI the process continues until the last thread exits.
// That is, the thread's have independent lifetimes. Hence
// Jaeschke's original code was designed to show that the primary
// thread could exit and not influence the other threads.

// However in C++ the process terminates when the primary thread exits
// and when the process terminates all its threads are then terminated.
// Hence if you comment out the following waits, the non-primary
// threads will never get a chance to run.

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 );

// The handle returned by _beginthreadex() has to be closed
// by the caller of _beginthreadex().

CloseHandle( hth1 );
CloseHandle( hth2 );

delete o1;
o1 = NULL;

delete o2;
o2 = NULL;

printf("Primary thread terminating.\n");
}