簡介

Windows線上程控制方面提供了多種訊號處理機制，其中一種便是使用 CreateEvent() 函式建立事件，然後使用訊號控制執行緒執行。其中將事件變為有訊號可使用 SetEvent() 函式，將事件訊號復位（變為無訊號）可使用 ResetEvent() 函式，訊號可以配合 WaitForSingleObject() 函式對執行緒的同步進行控制，當有訊號時，此函式便會放行；無訊號時，此函式會將阻塞。

提示： CreateEvent() 函式的引數 bManualReset 的含義是訊號是否由人工復位，如果選擇true，則訊號必須手動採用ResetEvent() 函式進行復位操作。在這種情況下，可能會偶爾出現執行緒不同步的情況，問題出在可能同時會有多個執行緒穿過 WaitForSingleObject()

程式碼樣例

• bManualReset引數為false

////////////////////////////////
//
// FileName : ThreadEventDemo.cpp
// Creator : PeterZheng
// Date : 2018/9/23 18:00
// Comment : The usage of "CreateEvent"
//
////////////////////////////////

#pragma once

#include <cstdio>
#include <iostream>
#include <cstdlib>
#include <windows.h>

using namespace std;

DWORD WINAPI func1(LPVOID lpParam);
DWORD WINAPI func2(LPVOID lpParam);

HANDLE hEvent = NULL;
unsigned int unCount = 0;

DWORD WINAPI func1(LPVOID lpParam)
{
	while (true)
	{
		WaitForSingleObject(hEvent, INFINITE);
		ResetEvent(hEvent);
		if (unCount < 100)
		{
			unCount++;
			Sleep(10);
			cout << "Count: " << unCount << endl;
			SetEvent(hEvent);
		}
		else
		{
			SetEvent(hEvent);
			break;
		}
	}
	return 0;
}

DWORD WINAPI func2(LPVOID lpParam)
{
	while (true)
	{
		WaitForSingleObject(hEvent, INFINITE);
		ResetEvent(hEvent); // 重置事件為無訊號狀態
		if (unCount < 100)
		{
			unCount++;
			Sleep(10);
			cout << "Count: " << unCount << endl;
			SetEvent(hEvent); // 設定事件為有訊號狀態
		}
		else
		{
			SetEvent(hEvent);
			break;
		}
	}
	return 0;
}

int main(void)
{
	HANDLE hThread[2] = { NULL };
	hEvent = CreateEvent(NULL, false, false, NULL); //建立一個匿名事件,當引數bManualReset設定為false時
	hThread[0] = CreateThread(NULL, 0, func1, NULL, 0, NULL);
	cout << "Thread-1 is RUNNING" << endl;
	hThread[1] = CreateThread(NULL, 0, func2, NULL, 0, NULL);
	cout << "Thread-2 is RUNNING" << endl;
	SetEvent(hEvent);
	WaitForMultipleObjects(2, hThread, true, INFINITE); //等待兩個執行緒執行結束
	CloseHandle(hThread[0]);
	CloseHandle(hThread[1]);
	CloseHandle(hEvent);
	system("pause");
	return 0;
}
 

• bManualReset引數為true

////////////////////////////////
//
// FileName : ThreadEventDemo.cpp
// Creator : PeterZheng
// Date : 2018/9/23 18:00
// Comment : The usage of "CreateEvent"
//
////////////////////////////////

#pragma once

#include <cstdio>
#include <iostream>
#include <cstdlib>
#include <windows.h>

using namespace std;

DWORD WINAPI func1(LPVOID lpParam);
DWORD WINAPI func2(LPVOID lpParam);

HANDLE hEvent = NULL;
HANDLE hMutex = NULL;
unsigned int unCount = 0;

DWORD WINAPI func1(LPVOID lpParam)
{
	while (true)
	{
		WaitForSingleObject(hEvent, INFINITE);
		WaitForSingleObject(hMutex, INFINITE); //為互斥體上鎖
		ResetEvent(hEvent); // 重置事件為無訊號狀態
		if (unCount < 100)
		{
			unCount++;
			Sleep(10);
			cout << "Count: " << unCount << endl;
			SetEvent(hEvent); // 設定事件為有訊號狀態
			ReleaseMutex(hMutex); //互斥體解鎖
		}
		else
		{
			SetEvent(hEvent);
			ReleaseMutex(hMutex);
			break;
		}
	}
	return 0;
}

DWORD WINAPI func2(LPVOID lpParam)
{
	while (true)
	{
		WaitForSingleObject(hEvent, INFINITE);
		WaitForSingleObject(hMutex, INFINITE); //為互斥體上鎖
		ResetEvent(hEvent); // 重置事件為無訊號狀態
		if (unCount < 100)
		{
			unCount++;
			Sleep(10);
			cout << "Count: " << unCount << endl;
			SetEvent(hEvent); // 設定事件為有訊號狀態
			ReleaseMutex(hMutex);
		}
		else
		{
			SetEvent(hEvent);
			ReleaseMutex(hMutex);
			break;
		}
	}
	return 0;
}

int main(void)
{
	HANDLE hThread[2] = { NULL };
	hEvent = CreateEvent(NULL, true, false, NULL); //建立一個匿名事件,當引數bManualReset設定為true時
	hMutex = CreateMutex(NULL, false, NULL); //建立一個匿名互斥體
	hThread[0] = CreateThread(NULL, 0, func1, NULL, 0, NULL);
	cout << "Thread-1 is RUNNING" << endl;
	hThread[1] = CreateThread(NULL, 0, func2, NULL, 0, NULL);
	cout << "Thread-2 is RUNNING" << endl;
	SetEvent(hEvent); // 設定事件為有訊號狀態
	WaitForMultipleObjects(2, hThread, true, INFINITE); //等待兩個執行緒執行結束
	CloseHandle(hThread[0]);
	CloseHandle(hThread[1]);
	CloseHandle(hEvent);
	CloseHandle(hMutex);
	system("pause");
	return 0;
}