1 内核对象
前面已经学过线程和互斥体两个内核对象。此节讲了事件这个内核对象。前面提出了内核对象这个概念,可能不太清晰,简单来说内核对象就是系统层的东西。
1.1 小结内核对象:
进程、线程、事件、互斥体、文件、文件映射等。
1.2 事件内核对象的创建
HANDLE g_hEvent = CreateEvent(NULL, TRUE, FALSE, "XYZ");
HANDLE g_hMutex = CreateMutex(NULL,FALSE, "XYZ");
1.3 事件内核对象的获取
HANDLE OpenEvent(
DWORD dwDesiredAccess, // access
BOOL bInheritHandle, // inheritance option
LPCTSTR lpName // object name
);
HANDLE g_hEvent = OpenEvent(EVENT_ALL_ACCESS, FALSE, "XYZ");
HANDLE g_hMutex = OpenMutex(MUTEX_ALL_ACCESS,FALSE, "XYZ");
1.4 内核对象的销毁
BOOL CloseHandle(HANDLE hobj);
(1)、当没有其他程序引用时,系统会销毁内核对象(使用数量).
(2)、内核对象的生命周期,可能比创建它的对象要长.
2 事件对象
2.1 事件对象的创建
HANDLE CreateEvent(
LPSECURITY_ATTRIBUTES lpEventAttributes, // 安全属性 NULL时为系统默认
BOOL bManualReset, // TRUE 通过调用ResetEvent将事件对象标记为未通知
BOOL bInitialState, // TRUE 已通知状态 FALSE未通知状态
LPCTSTR lpName // 对象名称 以NULL结尾的字符串
);
2.2 事件对象的控制
BOOL SetEvent(HANDLE hEvent);
2.3 关闭时间对象句柄
CloseHandle();
2.4 线程控制实验:只读形式的线程控制
HANDLE g_hEvent;
HWND hEdit1;
HWND hEdit2;
HWND hEdit3;
HWND hEdit4;
HANDLE hThread1;
HANDLE hThread2;
HANDLE hThread3;
HANDLE hThread4;
DWORD WINAPI ThreadProc1(LPVOID lpParameter)
{
//创建事件
//默认安全属性 手动设置未通知状态(TRUE) 初始状态未通知 没有名字
g_hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
HANDLE hThread[3];
//创建3个线程
hThread[0] = ::CreateThread(NULL, 0, ThreadProc2, NULL, 0, NULL);
hThread[1] = ::CreateThread(NULL, 0, ThreadProc3, NULL, 0, NULL);
hThread[2] = ::CreateThread(NULL, 0, ThreadProc4, NULL, 0, NULL);
//设置文本框的值
SetWindowText(hEdit1,"1000");
//设置事件为已通知
SetEvent(g_hEvent);
//等待线程结束 销毁内核对象
WaitForMultipleObjects(3, hThread, TRUE, INFINITE);
CloseHandle(hThread[0]);
CloseHandle(hThread[1]);
CloseHandle(hThread[2]);
CloseHandle(g_hEvent);
return 0;
}
DWORD WINAPI ThreadProc2(LPVOID lpParameter)
{
TCHAR szBuffer[10] = {0};
//当事件变成已通知时
WaitForSingleObject(g_hEvent, INFINITE);
//读取内容
GetWindowText(hEdit1,szBuffer,10);
SetWindowText(hEdit2,szBuffer);
return 0;
}
DWORD WINAPI ThreadProc3(LPVOID lpParameter)
{
TCHAR szBuffer[10] = {0};
//当事件变成已通知时
WaitForSingleObject(g_hEvent, INFINITE);
//读取内容
GetWindowText(hEdit1,szBuffer,10);
SetWindowText(hEdit3,szBuffer);
return 0;
}
DWORD WINAPI ThreadProc4(LPVOID lpParameter)
{
TCHAR szBuffer[10] = {0};
//当事件变成已通知时
WaitForSingleObject(g_hEvent, INFINITE);
//读取内容
GetWindowText(hEdit1,szBuffer,10);
SetWindowText(hEdit4,szBuffer);
return 0;
}
3 线程同步
3.1 什么是线程同步?
同步就是协同步调,按预定的先后次序进行运行。如:你说完,我再说。
如进程、线程同步,可理解为进程或线程A和B一块配合,A执行到一定程度时要依靠B的某个结果,于是停下来,示意B运行;B依言执行,再将结果给A;A再继续操作。
[摘自百度百科]
3.2 事件和临界区
HANDLE g_hSet, g_hClear;
int g_Max = 10;
int g_Number = 0;
//生产者线程函数
DWORD WINAPI ThreadProduct(LPVOID pM)
{
for (int i = 0; i < g_Max; i++)
{
WaitForSingleObject(g_hSet, INFINITE);
g_Number = 1;
DWORD id = GetCurrentThreadId();
printf("生产者%d将数据%d放入缓冲区\n",id, g_Number);
SetEvent(g_hClear);
}
return 0;
}
//消费者线程函数
DWORD WINAPI ThreadConsumer(LPVOID pM)
{
for (int i = 0; i < g_Max; i++)
{
WaitForSingleObject(g_hClear, INFINITE);
g_Number = 0;
DWORD id = GetCurrentThreadId();
printf("----消费者%d将数据%d放入缓冲区\n",id, g_Number);
SetEvent(g_hSet);
}
return 0;
}
int main(int argc, char* argv[])
{
HANDLE hThread[2];
g_hSet = CreateEvent(NULL, FALSE, TRUE, NULL);
g_hClear = CreateEvent(NULL, FALSE, FALSE, NULL);
hThread[0] = ::CreateThread(NULL, 0, ThreadProduct, NULL, 0, NULL);
hThread[1] = ::CreateThread(NULL, 0, ThreadConsumer, NULL, 0, NULL);
WaitForMultipleObjects(2, hThread, TRUE, INFINITE);
CloseHandle(hThread[0]);
CloseHandle(hThread[1]);
//销毁
CloseHandle(g_hSet);
CloseHandle(g_hClear);
return 0;
}