_beginThreadex创建多线程解读

来源：互联网发布：淘宝二手ipad哪家靠谱编辑：程序博客网时间：2024/06/05 17:40

http://blog.csdn.net/wojiushiwo987/article/details/7720656

一、需要的头文件支持

#include <process.h> // for _beginthread()

需要的设置:ProjectàSetting-->C/C++-->User run-time library 选择Debug Multithreaded 或者Multithreaded。即使用: MT或MTD。

源码如下：

[cpp] view plaincopyprint?

#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( -100000, 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");
return 0;
}

#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( -100000, 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");return 0;}

二、解释

（1）如果你正在编写C/C++代码，决不应该调用CreateThread。相反，应该使用VisualC++运行期库函数_beginthreadex，退出也应该使用_endthreadex。如果不使用Microsoft的VisualC++编译器，你的编译器供应商有它自己的CreateThread替代函数。不管这个替代函数是什么，你都必须使用。

（2）因为_beginthreadex和_endthreadex是CRT线程函数，所以必须注意编译选项runtimelibaray的选择，使用MT或MTD。[MultiThreaded , Debug MultiThreaded]。

（3）_beginthreadex函数的参数列表与CreateThread函数的参数列表是相同的，但是参数名和类型并不完全相同。这是因为Microsoft的C/C++运行期库的开发小组认为，C/C++运行期函数不应该对Windows数据类型有任何依赖。_beginthreadex函数也像CreateThread那样，返回新创建的线程的句柄。

下面是关于_beginthreadex的一些要点：

1）每个线程均获得由C/C++运行期库的堆栈分配的自己的tiddata内存结构。（tiddata结构位于Mtdll.h文件中的VisualC++源代码中）。

2）传递给_beginthreadex的线程函数的地址保存在tiddata内存块中。传递给该函数的参数也保存在该数据块中。

3）_beginthreadex确实从内部调用CreateThread，因为这是操作系统了解如何创建新线程的唯一方法。

4）当调用CreatetThread时，它被告知通过调用_threadstartex而不是pfnStartAddr来启动执行新线程。还有，传递给线程函数的参数是tiddata结构而不是pvParam的地址。

5）如果一切顺利，就会像CreateThread那样返回线程句柄。如果任何操作失败了，便返回NULL。

（4）_endthreadex的一些要点：

C运行期库的_getptd函数内部调用操作系统的TlsGetValue函数，该函数负责检索调用线程的tiddata内存块的地址。

然后该数据块被释放，而操作系统的ExitThread函数被调用，以便真正撤消该线程。当然，退出代码要正确地设置和传递。

（5）虽然也提供了简化版的的_beginthread和_endthread，但是可控制性太差，所以一般不使用。

（6）线程handle因为是内核对象，所以需要在最后closehandle。

（7）更多的API：

HANDLE GetCurrentProcess();

HANDLE GetCurrentThread();

DWORD GetCurrentProcessId();

DWORD GetCurrentThreadId()。

DWORD SetThreadIdealProcessor(HANDLE hThread,DWORDdwIdealProcessor);

BOOL SetThreadPriority(HANDLE hThread,int nPriority);

BOOL SetPriorityClass(GetCurrentProcess(), IDLE_PRIORITY_CLASS);

BOOL GetThreadContext(HANDLE hThread,PCONTEXTpContext);

BOOL SwitchToThread();

三、注意

（1）C++主线程的终止，同时也会终止所有主线程创建的子线程，不管子线程有没有执行完毕。所以上面的代码中如果不调用WaitForSingleObject，则2个子线程t1和t2可能并没有执行完毕或根本没有执行。

（2）如果某线程挂起，然后有调用WaitForSingleObject等待该线程，就会导致死锁。所以上面的代码如果不调用resumethread，则会死锁。

四、为什么用_beginthreadex而不是CreateThread?

为什么要用C运行时库的_beginthreadex代替操作系统的CreateThread来创建线程？

来源自自1999年7月MSJ杂志的《Win32 Q&A》栏目

你也许会说我一直用CreateThread来创建线程，一直都工作得好好的，为什么要用_beginthreadex来代替CreateThread，下面让我来告诉你为什么。

回答一个问题可以有两种方式，一种是简单的，一种是复杂的。

如果你不愿意看下面的长篇大论，那我可以告诉你简单的答案：_beginthreadex在内部调用了CreateThread，在调用之前_beginthreadex做了很多的工作，从而使得它比CreateThread更安全。