windows多线程分析——Event

CreateThread（）函数中的第五个参数如果是0的话，那么创建的线程会马上执行。

先来看代码：

#define WIN32_LEAN_MEAN	
#include <stdio.h>
#include <stdlib.h>
#include <Windows.h>
#include <time.h>
#include "../../MtVerify.h"
DWORD WINAPI ThreadFunc(LPVOID);
HANDLE hRequestExitEvent=false;
int main()
{
	HANDLE hThreads[2];
	DWORD dwThreadId;
	DWORD dwExitCode=0;
	int i;
	hRequestExitEvent=CreateEvent(NULL,TRUE,FALSE,NULL);
	for (int i = 0; i < 2; i++)
	{
		MTVERIFY(hThreads[i]=CreateThread(NULL,0,ThreadFunc,(LPVOID)i,0,&dwThreadId));
	}
	Sleep(1000);
	SetEvent(hRequestExitEvent);
	WaitForMultipleObjects(2,hThreads,TRUE,INFINITE);
	for (int i = 0; i < 2; i++)
	{
		MTVERIFY(CloseHandle(hThreads[i]));
	}
	return EXIT_SUCCESS;
}
DWORD WINAPI ThreadFunc(LPVOID p)
{
	int i;
	int inside=0;
	UNREFERENCED_PARAMETER(p);
	srand((unsigned)time(NULL));
	for ( i = 0; i < 1000000; i++)
	{
		double x=(double)(rand())/RAND_MAX;
		double y=(double)(rand())/RAND_MAX;
		if ((x*x+y*y)<=1.0)
		{
			inside++;
		}

SetEvent(hRequestExitEvent);

代码执行结果是打印出两行PI=3.142

如果我们把

SetEvent(hRequestExitEvent);

这句代码放到

Sleep(1000);

的前面一行，那么执行结果就是两行Received request to terminate

因为在执行两条工作线程的时候，事件已经被激活。