原文链接:http://blog.csdn.net/chen825919148/article/details/7904289
HANDLE CreateEvent(
LPSECURITY_ATTRIBUTES lpEventAttributes,
BOOL bManualReset,
BOOL bInitialState,
LPCSTR lpName
);
bManualReset:TRUE,使用ResetEvent()手动重置为无信号状态;FALSE,当一个等待线程被释放时,自动重置状态为无信号状态。
bInitialState:指定事件对象的初始状态,当TRUE,初始状态为有信号状态;当FALSE,初始状态为无信号状态。
下面主要演示一下采用CreateEvent实现多线程。
例子很简单,主要测试CreateEvent中bManualReset:和bInitialState参数的取值在线程调用中信号状态的情况。
测试1:
bManualReset:TRUE
bInitialState:TRUE
CreateEvent(NULL, TRUE, TRUE, NULL); //使用手动重置为无信号状态,初始化时有信号状态
example.cpp
- #include "iostream"
- #include "windows.h"
- using namespace std;
-
- DWORD WINAPI ThreadProc1(LPVOID lpParam);
- DWORD WINAPI ThreadProc2(LPVOID lpParam);
- HANDLE hEvent = NULL;
- HANDLE hThread1 = NULL;
- HANDLE hThread2 = NULL;
- int main(int argc, char *args[])
- {
- <span style="color:#ff0000;">hEvent = CreateEvent(NULL, TRUE, TRUE, NULL)</span>;
-
-
-
-
-
- hThread1 = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)ThreadProc1, NULL, 0,NULL);
- Sleep(200);
- hThread2 = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)ThreadProc2, NULL, 0,NULL);
- Sleep(200);
- if ( NULL == hThread1)
- {
- cout <<"create thread fail!";
- }
-
-
- return 0;
- }
- DWORD WINAPI ThreadProc1(LPVOID lpParam)
- {
- cout <<"in thread1@!"<<endl;
-
- DWORD dReturn = WaitForSingleObject(hEvent,INFINITE);
-
- if ( WAIT_OBJECT_0 == dReturn)
- {
- cout <<" thread1 signaled ! "<<endl;
- }
- cout <<"in thread1 --signal"<<endl;
-
-
- return 0;
- }
- DWORD WINAPI ThreadProc2(LPVOID lpParam)
- {
- cout <<"in thread2@!"<<endl;
-
- DWORD dReturn = WaitForSingleObject(hEvent,INFINITE);
-
- if ( WAIT_OBJECT_0 == dReturn)
- {
- cout <<"thread2 signaled ! "<<endl;
- }
- cout <<"in thread2--signal"<<endl;
-
- return 0;
- }
执行结果:
![CreateEvent用法_第1张图片](http://img.e-com-net.com/image/info5/28de8fd57a204137b1811a8caa880209.png)
从结果中看,执行完线程1又执行了线程2.
由于hEvent = CreateEvent(NULL, TRUE, TRUE, NULL),使用手动重置为无信号状态,初始化时有信号状态
所以hEvent一直处于有信号状态,无论是线程1释放后,hEvent仍处于有信号状态,所以线程2正常执行了。
测试2:
bManualReset:FALSE
bInitialState:TRUE
- hEvent = CreateEvent(NULL, FALSE, TRUE, NULL);
example2.cpp
- #include "iostream"
- #include "windows.h"
- using namespace std;
-
- DWORD WINAPI ThreadProc1(LPVOID lpParam);
- DWORD WINAPI ThreadProc2(LPVOID lpParam);
- HANDLE hEvent = NULL;
- HANDLE hThread1 = NULL;
- HANDLE hThread2 = NULL;
- int main(int argc, char *args[])
- {
-
- <span style="color:#ff0000;">hEvent = CreateEvent(NULL, FALSE, TRUE, NULL); </span>
-
-
-
-
- hThread1 = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)ThreadProc1, NULL, 0,NULL);
- Sleep(200);
- hThread2 = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)ThreadProc2, NULL, 0,NULL);
- Sleep(200);
- if ( NULL == hThread1)
- {
- cout <<"create thread fail!";
- }
-
-
- return 0;
- }
- DWORD WINAPI ThreadProc1(LPVOID lpParam)
- {
- cout <<"in thread1@!"<<endl;
-
- DWORD dReturn = WaitForSingleObject(hEvent,INFINITE);
-
- if ( WAIT_OBJECT_0 == dReturn)
- {
- cout <<" thread1 signaled ! "<<endl;
- }
- cout <<"in thread1 --signal"<<endl;
-
-
- return 0;
- }
- DWORD WINAPI ThreadProc2(LPVOID lpParam)
- {
- cout <<"in thread2@!"<<endl;
-
- DWORD dReturn = WaitForSingleObject(hEvent,INFINITE);
-
- if ( WAIT_OBJECT_0 == dReturn)
- {
- cout <<"thread2 signaled ! "<<endl;
- }
- cout <<"in thread2--signal"<<endl;
-
- return 0;
- }
执行结果:
![](http://img.e-com-net.com/image/info5/a347121c42a94f43bd6dfe6ccaccf663.png)
从执行结果中分析,执行了线程1,线程2一直在等待,直到主线程结束。
由于hEvent = CreateEvent(NULL, FALSE, TRUE, NULL),当一个等待线程被释放时,自动重置为无信号状态,初始是有信号状态
初始执行线程1的时候,hEvent是有信号的,所以线程1正常执行;又由于bManualReset=FALSE,所以执行完线程1后,hEvent自动重置为无信号状态,所以在线程2中,
- WaitForSingleObject(hEvent,INFINITE);
函数一直在等待hEvent变为有信号状态,但是当主线程执行完,还没等待到,线程2程序一直没有走下去。
测试3:
bManualReset:TRUE
bInitialState:FALSE
hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);//使用手动重置为无信号状态,初始化时为无信号状态
example3.cpp
- #include "iostream"
- #include "windows.h"
- using namespace std;
-
- DWORD WINAPI ThreadProc1(LPVOID lpParam);
- DWORD WINAPI ThreadProc2(LPVOID lpParam);
- HANDLE hEvent = NULL;
- HANDLE hThread1 = NULL;
- HANDLE hThread2 = NULL;
- int main(int argc, char *args[])
- {
-
-
- <span style="color:#ff0000;">hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
-
-
-
-
- hThread1 = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)ThreadProc1, NULL, 0,NULL);
- Sleep(200);
- hThread2 = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)ThreadProc2, NULL, 0,NULL);
- Sleep(200);
- if ( NULL == hThread1)
- {
- cout <<"create thread fail!";
- }
-
-
- return 0;
- }
- DWORD WINAPI ThreadProc1(LPVOID lpParam)
- {
- cout <<"in thread1@!"<<endl;
-
- DWORD dReturn = WaitForSingleObject(hEvent,INFINITE);
-
- if ( WAIT_OBJECT_0 == dReturn)
- {
- cout <<" thread1 signaled ! "<<endl;
- }
- cout <<"in thread1 --signal"<<endl;
-
-
- return 0;
- }
- DWORD WINAPI ThreadProc2(LPVOID lpParam)
- {
- cout <<"in thread2@!"<<endl;
-
- DWORD dReturn = WaitForSingleObject(hEvent,INFINITE);
-
- if ( WAIT_OBJECT_0 == dReturn)
- {
- cout <<"thread2 signaled ! "<<endl;
- }
- cout <<"in thread2--signal"<<endl;
-
- return 0;
- }
执行结果,可想而知,只能输出:
因为初始为无信号状态,所以hEvent一直处于无信号状态,因此这两个线程一直在等待,直到主线程结束。
修改:放开例子中的注释部分:
if (SetEvent(hEvent))//设置信号为有信号状态
{
cout << "setEvent 成功" <<endl;
}
执行结果:
![CreateEvent用法_第2张图片](http://img.e-com-net.com/image/info5/40d36ce2591d4a22af372ab0e9851b98.png)
可见,线程1和线程2都执行了。
因为调用SetEvent,事件变为有信号状态,线程1执行;又由于线程1释放后,hEvent仍旧处于有信号状态,所以线程2也执行了。
再修改:在线程1中,添加ResetEvent(hEvent)(手动设置事件为无信号状态),则线程2不会执行。
测试4:
bManualReset:FALSE
bInitialState:FALSE
hEvent = CreateEvent(NULL, FALSE, FALSE, NULL);//线程释放后自动重置为无信号状态,初始化时为无信号状态
example4.cpp
- #include "iostream"
- #include "windows.h"
- using namespace std;
-
- DWORD WINAPI ThreadProc1(LPVOID lpParam);
- DWORD WINAPI ThreadProc2(LPVOID lpParam);
- HANDLE hEvent = NULL;
- HANDLE hThread1 = NULL;
- HANDLE hThread2 = NULL;
- int main(int argc, char *args[])
- {
-
-
-
- hEvent = CreateEvent(NULL, FALSE, FALSE, NULL);
- if (SetEvent(hEvent))
- {
- cout << "setEvent 成功" <<endl;
- }
- hThread1 = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)ThreadProc1, NULL, 0,NULL);
- Sleep(200);
- hThread2 = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)ThreadProc2, NULL, 0,NULL);
- Sleep(200);
- if ( NULL == hThread1)
- {
- cout <<"create thread fail!";
- }
-
-
- return 0;
- }
- DWORD WINAPI ThreadProc1(LPVOID lpParam)
- {
- cout <<"in thread1@!"<<endl;
-
- DWORD dReturn = WaitForSingleObject(hEvent,INFINITE);
-
- if ( WAIT_OBJECT_0 == dReturn)
- {
- cout <<" thread1 signaled ! "<<endl;
- }
- cout <<"in thread1 --signal"<<endl;
-
-
- return 0;
- }
- DWORD WINAPI ThreadProc2(LPVOID lpParam)
- {
- cout <<"in thread2@!"<<endl;
-
- DWORD dReturn = WaitForSingleObject(hEvent,INFINITE);
-
- if ( WAIT_OBJECT_0 == dReturn)
- {
- cout <<"thread2 signaled ! "<<endl;
- }
- cout <<"in thread2--signal"<<endl;
-
- return 0;
- }
执行结果:
![CreateEvent用法_第3张图片](http://img.e-com-net.com/image/info5/c2137f47bc9f4dc2b81c4da8875a03cd.png)
由于调用SetEvent,hEvent为有信号状态,线程1正常执行,又由于调用完线程1后,hEvent自动重置为无信号状态,所以线程2只能在等待,直到主线程退出。
修改:线程1中的SetEvent(hEvent);的注释去掉,再运行,则线程1和线程2 都会执行。