第二十章 多任务和多线程

Microsoft Windows的16位版本支持有限度的多任务，Windows的32位版本支持真正的多任务，而且，还多了一种额外的优点，多线程

20.1多任务的各种模式

多线程是为了使得多个线程并行的工作以完成多项任务，以提高系统的效率。线程是在同一时间需要完成多项任务的时候被实现的 多任务是指用户可以在同一时间内运行多个应用程序,每个应用程序被称作一个任务。Windows就是一个支持多任务的操作系统,比起DOS的单任务系统,确实方便了许多。使用Windows定时器是在Windows的早期（和目前）版本中模拟多任务的一种好方法，然而，定时器的使用有时限制了程序的速度。

#include <windows.h> #include <math.h> LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ; int cyChar ; int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR szCmdLine, int iCmdShow) { static TCHAR szAppName[] = TEXT ("Multi1") ; HWND hwnd ; MSG msg ; WNDCLASS wndclass ; wndclass.style = CS_HREDRAW | CS_VREDRAW; wndclass.lpfnWndProc = WndProc; wndclass.cbClsExtra = 0; wndclass.cbWndExtra = 0; wndclass.hInstance = hInstance; wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION); wndclass.hCursor = LoadCursor(NULL, IDC_ARROW); wndclass.hbrBackground =(HBRUSH)GetStockObject(WHITE_BRUSH); wndclass.lpszMenuName = NULL; wndclass.lpszClassName = szAppName; if (!RegisterClass(&wndclass)) { MessageBox (NULL, TEXT("This program requires Windows NT!"), szAppName, MB_ICONERROR); return 0; } hwnd = CreateWindow(szAppName, TEXT("Multitasking Demo"), WS_OVERLAPPEDWINDOW, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, NULL, NULL, hInstance, NULL); ShowWindow(hwnd, iCmdShow); UpdateWindow(hwnd); while (GetMessage (&msg, NULL, 0, 0)) { TranslateMessage(&msg); DispatchMessage(&msg); } return msg.wParam; } int CheckBottom(HWND hwnd, int cyClient, int iLine) { if (iLine * cyChar + cyChar > cyClient) { InvalidateRect(hwnd, NULL, TRUE); UpdateWindow(hwnd); iLine = 0; } return iLine; }LRESULT APIENTRY WndProc1(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam) { static int iNum, iLine, cyClient; HDC hdc; TCHAR szBuffer[16]; switch (message) { case WM_SIZE: cyClient = HIWORD(lParam); return 0 ; case WM_TIMER: if (iNum < 0) iNum = 0 ; iLine = CheckBottom(hwnd, cyClient, iLine); hdc = GetDC(hwnd); TextOut(hdc, 0, iLine * cyChar, szBuffer, wsprintf(szBuffer, TEXT ("%d"), iNum++)); ReleaseDC(hwnd, hdc); iLine++; return 0; } return DefWindowProc(hwnd, message, wParam, lParam); } /************************************************************************//*如果一个数除了1和它自身以外没有别的因子，那么这个数就是质数。当然，要检查一个数是否是质数并不要求使用小于被检查数的所有数来除这个数并检查余数，而只需使用所有小于被检查数的平方根的数。平方根计算是发表浮点数的原因，否则，该程序将是完全依据整数的程序。*//************************************************************************/LRESULT APIENTRY WndProc2(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam) { static int iNum = 1, iLine, cyClient; HDC hdc; int i, iSqrt; TCHAR szBuffer[16]; switch (message) { case WM_SIZE: cyClient = HIWORD(lParam); return 0 ; case WM_TIMER: do{ if (++iNum < 0) iNum = 0 ; iSqrt = (int)sqrt((double)iNum); for (i = 2 ; i <= iSqrt ; i++) if (iNum % i == 0) break ; } while (i <= iSqrt); iLine = CheckBottom(hwnd, cyClient, iLine); hdc = GetDC(hwnd); TextOut (hdc, 0, iLine * cyChar, szBuffer, wsprintf(szBuffer, TEXT ("%d"), iNum)); ReleaseDC(hwnd, hdc); iLine++; return 0; } return DefWindowProc(hwnd, message, wParam, lParam); }LRESULT APIENTRY WndProc3(HWND hwnd, UINT message, WPARAM wParam,LPARAM lParam) { static int iNum = 0, iNext = 1, iLine, cyClient; HDC hdc; int iTemp; TCHAR szBuffer[16]; switch (message) { case WM_SIZE:cyClient = HIWORD(lParam); return 0 ; case WM_TIMER: if (iNum < 0) { iNum = 0; iNext = 1; } iLine = CheckBottom(hwnd, cyClient, iLine); hdc = GetDC(hwnd); TextOut (hdc, 0, iLine * cyChar, szBuffer, wsprintf(szBuffer, TEXT("%d"), iNum)); ReleaseDC (hwnd, hdc) ; iTemp = iNum ; iNum = iNext ; iNext += iTemp; iLine++; return 0; } return DefWindowProc(hwnd, message, wParam, lParam) ; } LRESULT APIENTRY WndProc4(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam) { static int cxClient, cyClient ; HDC hdc ; int iDiameter ; switch (message) { case WM_SIZE: cxClient = LOWORD(lParam); cyClient = HIWORD(lParam); return 0 ; case WM_TIMER: //该函数向指定的窗体添加一个矩形，//然后窗口客户区域的这一部分将被重新绘制。//当指定TRUE时需要重画。InvalidateRect(hwnd, NULL, TRUE); UpdateWindow(hwnd); iDiameter = rand() % (max(1, min(cxClient, cyClient))); hdc = GetDC(hwnd); Ellipse(hdc, (cxClient - iDiameter) / 2, (cyClient - iDiameter) / 2, (cxClient + iDiameter) / 2, (cyClient + iDiameter) / 2) ; ReleaseDC(hwnd, hdc); return 0 ; } return DefWindowProc(hwnd, message, wParam, lParam) ; } LRESULT APIENTRY WndProc( HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam) { static HWND hwndChild[4] ; static TCHAR * szChildClass[] = { TEXT ("Child1"), TEXT("Child2"), TEXT ("Child3"), TEXT ("Child4") } ; static WNDPROC ChildProc[] = { WndProc1, WndProc2, WndProc3, WndProc4}; HINSTANCE hInstance; int i, cxClient, cyClient; WNDCLASS wndclass; switch(message) { case WM_CREATE: hInstance = (HINSTANCE)GetWindowLong(hwnd, GWL_HINSTANCE); wndclass.style = CS_HREDRAW | CS_VREDRAW; wndclass.cbClsExtra = 0; wndclass.cbWndExtra = 0; wndclass.hInstance = hInstance; wndclass.hIcon = NULL; wndclass.hCursor = LoadCursor(NULL, IDC_ARROW); wndclass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH); wndclass.lpszMenuName = NULL; for (i = 0 ; i < 4 ; i++) { wndclass.lpfnWndProc = ChildProc[i]; wndclass.lpszClassName = szChildClass[i];RegisterClass(&wndclass); hwndChild[i] = CreateWindow(szChildClass[i], NULL, WS_CHILDWINDOW | WS_BORDER | WS_VISIBLE, 0, 0, 0, 0, hwnd, (HMENU) i, hInstance, NULL); } //该函数返回系统的对话基本单位，//该基本单位为系统字体字符的平均宽度和高度。//返回值的低位字含有水平对话框基本单位，//且高低位字含有垂直对话框基本单位。cyChar = HIWORD(GetDialogBaseUnits()); SetTimer(hwnd, 1, 10, NULL); return 0; case WM_SIZE: cxClient = LOWORD(lParam); cyClient = HIWORD(lParam); for (i = 0 ; i < 4 ; i++) MoveWindow(hwndChild[i], (i % 2) * cxClient / 2, (i > 1) * cyClient / 2, cxClient / 2, cyClient / 2, TRUE); return 0 ; case WM_TIMER: for (i = 0 ; i < 4 ; i++) SendMessage(hwndChild[i], WM_TIMER, wParam, lParam); return 0; case WM_CHAR: //ESC按下以后就销毁窗口if (wParam == '/x1B') DestroyWindow(hwnd); return 0; case WM_DESTROY: KillTimer(hwnd, 1); PostQuitMessage(0); return 0; } return DefWindowProc(hwnd, message, wParam, lParam); }

20.2Windows 的多线程处理

建立新的线程的API函数是CreateThread.线程回调函数格式：DWORD WINAPI ThreadProc(PVOID pParam);

hThread = CreateThread (&security_attributes, dwStackSize, ThreadProc, pParam, dwFlags, &idThread);//security_attributes 指向SECURITY_ATTRIBUTES型态的结构的指针,在Windows NT中，它被设为NULL// dwStackSize 第二个参数是用于新线程的初始堆栈大小，默认值为0//ThreadProc 第三个参数是指向线程函数的指标//pParam 第四个参数为传递给ThreadProc的参数，这样主线程和从属线程就可以共享数据//dwFlags 第五个参数通常为0，但当建立的线程不马上执行时为旗标CREATE_SUSPENDED。线程将暂停直到呼叫ResumeThread来恢复线程的执行为止。//idThread 第六个参数是一个指标，指向接受执行绪ID值的变量。

再论随机矩形

「Project Settings」  「C/C++」  「Category」  「Code Generation」
在「Use  Run-Time  Library」下拉式清单方块中，可以看到用于「Release」设定的
「Single-Threaded」和用于Debug设定的「Debug  Single-Threaded」 。将这些分别改
为「Multithreaded」和「Debug Multithreaded」 。这将把编译器旗标改为/MT

PROCESS.H，这个文件定义一个名为_beginthread的函数，它启动一个新的线程。只有定义了_MT标识符，才会声明这个函数，这是/MT旗标的另一个结果。

#include <windows.h> #include <stdlib.h>// for the rand function LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ; void DrawRectangle (HWND) ; int cxClient, cyClient ; int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR szCmdLine, int iCmdShow) { static TCHAR szAppName[] = TEXT ("RandRect") ; HWND hwnd ; MSG msg ; WNDCLASS wndclass ; wndclass.style = CS_HREDRAW | CS_VREDRAW ; wndclass.lpfnWndProc= WndProc ; wndclass.cbClsExtra = 0 ; wndclass.cbWndExtra = 0 ; wndclass.hInstance = hInstance ; wndclass.hIcon = LoadIcon (NULL, IDI_APPLICATION) ; wndclass.hCursor = LoadCursor (NULL, IDC_ARROW) ; wndclass.hbrBackground= (HBRUSH) GetStockObject (WHITE_BRUSH) ; wndclass.lpszMenuName= NULL ; wndclass.lpszClassName= szAppName ; if (!RegisterClass (&wndclass)) { MessageBox (NULL, TEXT ("This program requires Windows NT!"), szAppName, MB_ICONERROR) ; return 0 ; } hwnd = CreateWindow (szAppName, TEXT ("Random Rectangles"), WS_OVERLAPPEDWINDOW, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, NULL, NULL, hInstance, NULL) ; ShowWindow (hwnd, iCmdShow) ; UpdateWindow (hwnd) ; while (TRUE){ //ｸﾃｺｯﾊﾎｪﾒｻｸ鋧｢ｼ・鰕ﾟｳﾌﾏ鋧｢ｶﾓﾁﾐ//ﾈ郢鋧鋧｢ｿﾉｵﾃｵｽ｣ｬｷｵｻﾘｷﾇﾁ聊ｵ｣ｻﾈ郢鈊ｻﾓﾐﾏ鋧｢ｿﾉｵﾃｵｽ｣ｬｷｵｻﾘﾖｵﾊﾇﾁ罍｣if (PeekMessage (&msg, NULL, 0, 0, PM_REMOVE)) { if (msg.message == WM_QUIT) break ; TranslateMessage (&msg) ; DispatchMessage (&msg) ; } else DrawRectangle (hwnd) ; } return msg.wParam ; } LRESULT CALLBACK WndProc (HWND hwnd, UINT iMsg, WPARAM wParam, LPARAM lParam) { switch (iMsg) { case WM_SIZE: cxClient = LOWORD (lParam) ; cyClient = HIWORD (lParam) ; return 0 ; case WM_DESTROY: PostQuitMessage (0) ; return 0 ; } return DefWindowProc (hwnd, iMsg, wParam, lParam) ; } void DrawRectangle (HWND hwnd) { HBRUSH hBrush; HDC hdc ; RECT rect ; if (cxClient == 0 || cyClient == 0) return ;//ｸﾝﾓﾉCｵﾄrandｺｯﾊｵﾃｵｽｵﾄﾋ貊摠ｾｨｾﾘﾐﾎﾗ・ﾍﾊｵﾐﾄｻｭﾋ｢ｵﾄﾉｫｲﾊ｡｣SetRect (&rect, rand () % cxClient, rand () % cyClient, rand () % cxClient, rand () % cyClient) ;//ｴｴｽｨｻｭﾋ｢hBrush = CreateSolidBrush (RGB (rand () % 256, rand () % 256, rand () % 256)) ; hdc = GetDC (hwnd) ;//ﾓﾃﾖｸｶｨｻｭﾋ｢ﾀｴﾌ鏸・ﾘﾐﾎFillRect (hdc, &rect, hBrush) ; ReleaseDC (hwnd, hdc) ; DeleteObject (hBrush) ; }   

编译器将在.OBJ文件中插入LIBCMT.LIB文件名，而不是LIBC.LIB。连结程序使用这个名称与执行期链接库函数连结LIBC.LIB和LIBCMT.LIB文件包含C语言链接库函数，有些C语言链接库函数包含静态数据。  

多线程解决方案

 #include <windows.h> #include <math.h> #include <process.h> typedef struct { HWND hwnd; int cxClient; int cyClient; int cyChar; BOOL bKill; } PARAMS, *PPARAMS; LRESULT APIENTRY WndProc(HWND, UINT, WPARAM, LPARAM); int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR szCmdLine, int iCmdShow) { static TCHAR szAppName[] = TEXT("Multi2"); HWND hwnd; MSG msg; WNDCLASS wndclass; wndclass.style = CS_HREDRAW | CS_VREDRAW; wndclass.lpfnWndProc = WndProc ; wndclass.cbClsExtra = 0 ; wndclass.cbWndExtra = 0 ; wndclass.hInstance = hInstance ; wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION); wndclass.hCursor = LoadCursor(NULL, IDC_ARROW); wndclass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH); wndclass.lpszMenuName = NULL; wndclass.lpszClassName = szAppName; if (!RegisterClass(&wndclass)) { MessageBox(NULL, TEXT ("This program requires Windows NT!"), szAppName, MB_ICONERROR); return 0; } hwnd = CreateWindow ( szAppName, TEXT("Multitasking Demo"), WS_OVERLAPPEDWINDOW, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, NULL, NULL, hInstance, NULL) ; ShowWindow(hwnd, iCmdShow); UpdateWindow(hwnd); while (GetMessage(&msg, NULL, 0, 0)) { TranslateMessage(&msg); DispatchMessage(&msg); } return msg.wParam; } int CheckBottom(HWND hwnd, int cyClient, int cyChar, int iLine) { if (iLine * cyChar + cyChar > cyClient) { InvalidateRect(hwnd, NULL, TRUE); UpdateWindow(hwnd); iLine = 0; } return iLine; } // -------------------------------------------------------------------------- // Window 1: Display increasing sequence of numbers // -------------------------------------------------------------------------- void Thread1(PVOID pvoid) { HDC hdc; int iNum = 0, iLine = 0; PPARAMS pparams; TCHAR szBuffer[16]; pparams = (PPARAMS)pvoid; while (!pparams->bKill) { if (iNum < 0) iNum = 0; iLine = CheckBottom(pparams->hwnd, pparams->cyClient, pparams->cyChar,iLine); hdc = GetDC(pparams->hwnd); TextOut (hdc, 0, iLine * pparams->cyChar, szBuffer, wsprintf (szBuffer, TEXT ("%d"), iNum++)); ReleaseDC(pparams->hwnd, hdc); iLine++; } _endthread(); } LRESULT APIENTRY WndProc1(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam) { static PARAMS params; switch (message) { //WM_CREATE消息处理期间，//它设定这个结构的hwnd和cyChar字段，呼叫_beginthread来建立一个使用Thread1函数//的新线程，并传递给新线程一个指向该结构的指针。case WM_CREATE: params.hwnd = hwnd; params.cyChar = HIWORD(GetDialogBaseUnits()); _beginthread(Thread1, 0, ¶ms); return 0 ; case WM_SIZE://WM_SIZE消息处理期间WndProc1//设定结构的cyClient字段params.cyClient = HIWORD(lParam); return 0 ; case WM_DESTROY://它将bKill字段设定为TRUE。params.bKill = TRUE; return 0; } return DefWindowProc(hwnd, message, wParam, lParam); } // -------------------------------------------------------------------------- // Window 2: Display increasing sequence of prime numbers // -------------------------------------------------------------------------- void Thread2(PVOID pvoid) { HDC hdc; int iNum = 1, iLine = 0, i, iSqrt; PPARAMS pparams; TCHAR szBuffer[16]; pparams = (PPARAMS)pvoid; while (!pparams->bKill) { do { if (++iNum < 0) iNum = 0; iSqrt = (int)sqrt((double)iNum); for (i = 2 ; i <= iSqrt ; i++) if (iNum % i == 0) break; } while (i <= iSqrt) ; iLine = CheckBottom(pparams->hwnd, pparams->cyClient, pparams->cyChar,iLine); hdc = GetDC(pparams->hwnd); TextOut(hdc, 0, iLine * pparams->cyChar, szBuffer, wsprintf(szBuffer, TEXT ("%d"), iNum)); ReleaseDC(pparams->hwnd, hdc); iLine++; } _endthread(); } LRESULT APIENTRY WndProc2(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam) { static PARAMS params; switch (message) { case WM_CREATE: params.hwnd = hwnd; params.cyChar = HIWORD(GetDialogBaseUnits()); _beginthread(Thread2, 0, ¶ms); return 0 ; case WM_SIZE: params.cyClient = HIWORD(lParam); return 0 ; case WM_DESTROY: params.bKill = TRUE; return 0; } return DefWindowProc(hwnd, message, wParam, lParam); } // Window 3: Display increasing sequence of Fibonacci numbers // ---------------------------------------------------------- void Thread3(PVOID pvoid) { HDC hdc; int iNum = 0, iNext = 1, iLine = 0, iTemp; PPARAMS pparams; TCHAR szBuffer[16]; pparams = (PPARAMS) pvoid ; while (!pparams->bKill) { if (iNum < 0) { iNum = 0 ; iNext = 1 ; } iLine = CheckBottom(pparams->hwnd, pparams->cyClient, pparams->cyChar, iLine); hdc = GetDC(pparams->hwnd); TextOut(hdc, 0, iLine * pparams->cyChar, szBuffer, wsprintf (szBuffer, TEXT ("%d"), iNum)); ReleaseDC (pparams->hwnd, hdc); iTemp = iNum; iNum = iNext; iNext += iTemp; iLine++ ; } _endthread(); } LRESULT APIENTRY WndProc3(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam) { static PARAMS params ; switch (message) { case WM_CREATE: params.hwnd = hwnd;//GetDialogBaseUnits//该函数返回系统的对话基本单位，//该基本单位为系统字体字符的平均宽度和高度params.cyChar = HIWORD (GetDialogBaseUnits()); _beginthread(Thread3, 0, ¶ms); return 0; case WM_SIZE: params.cyClient = HIWORD(lParam); return 0; case WM_DESTROY: params.bKill = TRUE; return 0; } return DefWindowProc(hwnd, message, wParam, lParam); } // ------------------------------------------------------------------------- // Window 4: Display circles of random radii // ------------------------------------------------------------------------- void Thread4 (PVOID pvoid) { HDC hdc; int iDiameter; PPARAMS pparams; pparams = (PPARAMS) pvoid ; while (!pparams->bKill) { InvalidateRect (pparams->hwnd, NULL, TRUE) ; UpdateWindow (pparams->hwnd) ; iDiameter = rand() % (max (1, min (pparams->cxClient, pparams->cyClient))) ; hdc = GetDC(pparams->hwnd); Ellipse(hdc, (pparams->cxClient - iDiameter) / 2, (pparams->cyClient - iDiameter) / 2, (pparams->cxClient + iDiameter) / 2, (pparams->cyClient + iDiameter) / 2); ReleaseDC(pparams->hwnd, hdc); } _endthread(); } //APIENTRY的定义//#define APIENTRY WINAPILRESULT APIENTRY WndProc4(HWND hwnd, UINT message,WPARAM wParam,LPARAM lParam) { static PARAMS params; switch (message) { case WM_CREATE: params.hwnd = hwnd; params.cyChar = HIWORD(GetDialogBaseUnits()); _beginthread(Thread4, 0, ¶ms); return 0; case WM_SIZE: params.cxClient = LOWORD(lParam); params.cyClient = HIWORD(lParam); return 0 ; case WM_DESTROY: params.bKill = TRUE; return 0; } return DefWindowProc (hwnd, message, wParam, lParam); } // -------------------------------------------------------------------------- // Main window to create child windows // -------------------------------------------------------------------------- LRESULT APIENTRY WndProc ( HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam) { static HWND hwndChild[4]; static TCHAR * szChildClass[] = { TEXT ("Child1"), TEXT ("Child2"), TEXT ("Child3"), TEXT ("Child4") }; static WNDPROC ChildProc[] = { WndProc1, WndProc2, WndProc3, WndProc4}; HINSTANCE hInstance; int i, cxClient, cyClient; WNDCLASS wndclass; //WndProc//为四个窗口注册了四种窗口类别，建立了这些窗口，//并在WM_SIZE消息处理期间缩放这些窗口。switch (message) { case WM_CREATE: hInstance = (HINSTANCE)GetWindowLong(hwnd, GWL_HINSTANCE); wndclass.style = CS_HREDRAW | CS_VREDRAW ; wndclass.cbClsExtra = 0 ; wndclass.cbWndExtra = 0 ; wndclass.hInstance =hInstance ; wndclass.hIcon = NULL ; wndclass.hCursor = LoadCursor(NULL, IDC_ARROW); wndclass.hbrBackground =(HBRUSH)GetStockObject(WHITE_BRUSH); wndclass.lpszMenuName = NULL; for (i = 0 ; i < 4 ; i++){ wndclass.lpfnWndProc = ChildProc[i] ; wndclass.lpszClassName = szChildClass[i]; RegisterClass (&wndclass); hwndChild[i] = CreateWindow (szChildClass[i], NULL, WS_CHILDWINDOW | WS_BORDER | WS_VISIBLE, 0, 0, 0, 0, hwnd, (HMENU) i, hInstance, NULL) ; } return 0; case WM_SIZE: cxClient = LOWORD(lParam); cyClient = HIWORD(lParam); for (i = 0 ; i < 4 ; i++) MoveWindow(hwndChild[i], (i % 2) * cxClient / 2, (i > 1) * cyClient / 2, cxClient / 2, cyClient / 2, TRUE) ; return 0 ; case WM_CHAR://ESC键if (wParam == '/x1B') DestroyWindow(hwnd);return 0; case WM_DESTROY: PostQuitMessage(0); return 0; } return DefWindowProc(hwnd, message, wParam, lParam); }

临界区域通过对EnterCriticalSection和LeaveCriticalSection的呼叫而加以界定。最好不要在线程之间共享GDI对象。

Sleep的好处

线程呼叫Sleep函数来自动暂停执行，该函数唯一一个参数是以毫秒计的时间。Sleep函数呼叫在指定的时间过去以前不会传回控制权。在这段时间内，线程被暂停，并且不会被配置给时间片段

20.3线程同步

有四个函数用于临界区域。要使用这些函数，您必须定义一个临界区域对象，这是一个型态
为CRITICAL_SECTION的整体变量。
CRITICAL_SECTION cs ;
这个临界区域对象必须先被程序中的某个线程初始化
InitializeCriticalSection (&cs) ;
当临界区域对象被初始化之后，线程可以通过下面的呼叫进入临界区域：
EnterCriticalSection (&cs) ;  
离开临界区域时，函数才会传回控制权：
LeaveCriticalSection (&cs) ;  
当临界区域不再被程序所需要时，可以通过呼叫
DeleteCriticalSection (&cs) ;  
临界区域的一个限制是它们只能用于在同一程序内的线程之间的协调。
需要协调两个不同程序对同一资源的共享（如共享内存等）。在此其况下不能使用临界区
域，但是可以使用一种被称为「互斥对象（mutex  object） 」的技术

事件对象

事件对象可以是「有信号的」或「没信号的」
可以通过下面呼叫来建立事件对象：
hEvent = CreateEvent(&sa, fManual, fInitial, pszName);  
第一个参数（指向一个SECURITY_ATTRIBUTES结构的指针）和最后一个参数（一个事
件对象的名字）只有在事件对象被多个程序共享时才有意义。
要设立一个现存的事件对象，呼叫
SetEvent(hEvent); 
要重置一个事件对象，呼叫
ResetEvent(hEvent);

BIGJOB1
#include <windows.h> #include <math.h> #include <process.h> #define REP 1000 #define STATUS_READY 0 #define STATUS_WORKING 1 #define STATUS_DONE 2 #define WM_CALC_DONE (WM_USER + 0) #define WM_CALC_ABORTED (WM_USER + 1) typedef struct { //为窗口句柄HWND hwnd;//指示线程是否继续计算或者停止BOOL bContinue; }PARAMS, *PPARAMS;LRESULT APIENTRY WndProc(HWND, UINT, WPARAM, LPARAM);int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR szCmdLine, int iCmdShow) { static TCHAR szAppName[] = TEXT ("BigJob1"); HWND hwnd; MSG msg; WNDCLASS wndclass ; wndclass.style = CS_HREDRAW | CS_VREDRAW; wndclass.lpfnWndProc = WndProc; wndclass.cbClsExtra = 0; wndclass.cbWndExtra = 0; wndclass.hInstance = hInstance; wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION) ; wndclass.hCursor = LoadCursor(NULL, IDC_ARROW) ; wndclass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH); wndclass.lpszMenuName = NULL; wndclass.lpszClassName = szAppName; if (!RegisterClass (&wndclass)) { MessageBox (NULL, TEXT("This program requires Windows NT!"), szAppName, MB_ICONERROR) ; return 0 ; } hwnd = CreateWindow (szAppName, TEXT ("Multithreading Demo"), WS_OVERLAPPEDWINDOW, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, NULL, NULL, hInstance, NULL) ; ShowWindow (hwnd, iCmdShow); UpdateWindow (hwnd); while (GetMessage(&msg, NULL, 0, 0)) { TranslateMessage(&msg); DispatchMessage(&msg); } return msg.wParam; } void Thread(PVOID pvoid) { double A = 1.0 ; INT i ; LONG lTime;//volatile，这种型态限定字向编译器指出变量可能会//在实际的程序叙述外被修改volatile PPARAMS pparams; pparams = (PPARAMS) pvoid; lTime = GetCurrentTime(); for (i = 0 ; i < REP && pparams->bContinue ; i++){ A = tan (atan (exp (log (sqrt (A * A))))) + 1.0;Sleep(5);}if (i == REP){ lTime = GetCurrentTime () - lTime ; //使用SendMessage向窗口消息处理程序发//送一个由程序定义的WM_USER_DONE消息，//并以经过的时间作为lParam参数。SendMessage(pparams->hwnd, WM_CALC_DONE, 0, lTime); } else{ //如果计算是在未完成之前被终止的//那么线程将发送给窗口消息处理程序一个WM_USER_ABORTED消息。SendMessage(pparams->hwnd, WM_CALC_ABORTED, 0, 0); }_endthread(); } LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam) { static INT iStatus; static LONG lTime; static PARAMS params ; static TCHAR *szMessage[] = { TEXT ("Ready (left mouse button begins)"), TEXT ("Working (right mouse button ends)"), TEXT ("%d repetitions in %ld msec") }; HDC hdc; PAINTSTRUCT ps; RECT rect; TCHAR szBuffer[64]; switch (message) { case WM_LBUTTONDOWN: if (iStatus == STATUS_WORKING) { MessageBeep(0); return 0; } //窗口消息处理程序将iStatus变量设为//STATUS_WORKINGiStatus = STATUS_WORKING; params.hwnd = hwnd; params.bContinue = TRUE; _beginthread(Thread, 0, (void*)¶ms); InvalidateRect(hwnd, NULL, TRUE); return 0; //当正在进行计算时，可以通过在显示区域中按下//鼠标右键来终止它case WM_RBUTTONDOWN: params.bContinue = FALSE; return 0; case WM_CALC_DONE: lTime = lParam; iStatus = STATUS_DONE; InvalidateRect(hwnd, NULL, TRUE); return 0; case WM_CALC_ABORTED: iStatus = STATUS_READY; InvalidateRect(hwnd, NULL, TRUE); return 0 ; case WM_PAINT: hdc = BeginPaint(hwnd, &ps); GetClientRect(hwnd, &rect); wsprintf (szBuffer, szMessage[iStatus], REP, lTime); DrawText (hdc, szBuffer, -1, &rect, DT_SINGLELINE | DT_CENTER | DT_VCENTER); EndPaint (hwnd, &ps); return 0; case WM_DESTROY: PostQuitMessage(0); return 0; } return DefWindowProc(hwnd, message, wParam, lParam); }

BIGJOB2

#include <windows.h> #include <math.h> #include <process.h> #define REP 1000000 #define STATUS_READY 0 #define STATUS_WORKING 1 #define STATUS_DONE 2 #define WM_CALC_DONE (WM_USER + 0) #define WM_CALC_ABORTED (WM_USER + 1) typedef struct { HWND hwnd;//PARAMS结构包括一个包含事件对象句柄的字段HANDLE hEvent; BOOL bContinue; }PARAMS, *PPARAMS ; LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM); int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR szCmdLine, int iCmdShow) { static TCHAR szAppName[] = TEXT ("BigJob2"); HWND hwnd; MSG msg; WNDCLASS wndclass; wndclass.style = CS_HREDRAW | CS_VREDRAW; wndclass.lpfnWndProc = WndProc; wndclass.cbClsExtra = 0; wndclass.cbWndExtra = 0; wndclass.hInstance = hInstance; wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION); wndclass.hCursor = LoadCursor(NULL, IDC_ARROW); wndclass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH); wndclass.lpszMenuName = NULL; wndclass.lpszClassName = szAppName; if (!RegisterClass (&wndclass)) { MessageBox (NULL, TEXT ("This program requires Windows NT!"), szAppName, MB_ICONERROR) ; return 0 ; } hwnd = CreateWindow (szAppName, TEXT ("Multithreading Demo"), WS_OVERLAPPEDWINDOW, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, NULL, NULL, hInstance, NULL) ; ShowWindow (hwnd, iCmdShow); UpdateWindow (hwnd); while (GetMessage (&msg, NULL, 0, 0)) {TranslateMessage (&msg); DispatchMessage (&msg); } return msg.wParam ; }//WaitForSingleObject//参数hHandle是一个事件的句柄，//第二个参数dwMilliseconds是时间间隔。如果事件是有信号状态返回WAIT_OBJECT_0，//如果时间超过dwMilliseconds值但时间事件还是无信号状态则返回WAIT_TIMEOUT。 //如果参数dwMilliseconds为INFINITE时函数将直到相应时间事件变成有信号状态才返回，//否则就一直等待下去，void Thread(PVOID pvoid) { double A = 1.0; INT i; LONG lTime ; volatile PPARAMS pparams ; pparams = (PPARAMS)pvoid;//Thread函数进入一个无限的while循环，//在循环开始时首先呼叫WaitForSingleObjectwhile (TRUE) { //因为事件被初始化为重置的，所以线//程的执行被阻挡在函数呼叫中。WaitForSingleObject(pparams->hEvent, INFINITE) ; lTime = GetCurrentTime () ; for (i = 0 ; i < REP && pparams->bContinue ; i++) A = tan (atan (exp (log (sqrt (A * A))))) + 1.0 ; if (i == REP) { lTime = GetCurrentTime () - lTime ; PostMessage(pparams->hwnd, WM_CALC_DONE, 0, lTime) ; } else PostMessage(pparams->hwnd, WM_CALC_ABORTED, 0, 0) ; } } LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam) { static HANDLE hEvent; static INT iStatus; static LONG lTime; static PARAMS params; static TCHAR *szMessage[] = { TEXT ("Ready (left mouse button begins)"), TEXT ("Working (right mouse button ends)"), TEXT ("%d repetitions in %ld msec") }; HDC hdc; PAINTSTRUCT ps; RECT rect;TCHAR szBuffer[64]; switch (message) { case WM_CREATE: //窗口消息处理程序首先建立一个初始化为没信号的自动重置事//件对象，然后建立线程。hEvent = CreateEvent(NULL, FALSE, FALSE, NULL);params.hwnd = hwnd ; params.hEvent = hEvent ; params.bContinue = FALSE ; _beginthread(Thread, 0, (PVOID)¶ms); return 0 ; case WM_LBUTTONDOWN: if (iStatus == STATUS_WORKING) { MessageBeep (0); return 0; } iStatus = STATUS_WORKING;params.bContinue = TRUE ; //按下鼠标左键将导致窗口过程调用SetEvent//这将释放由WaitForSingleObject呼叫产生的第二个线程，//并开始暴力测试计算SetEvent(hEvent); InvalidateRect(hwnd, NULL, TRUE); return 0; case WM_RBUTTONDOWN: params.bContinue = FALSE; return 0; case WM_CALC_DONE: lTime = lParam; iStatus = STATUS_DONE; InvalidateRect(hwnd, NULL, TRUE); return 0; case WM_CALC_ABORTED: iStatus = STATUS_READY; InvalidateRect(hwnd, NULL, TRUE); return 0;case WM_PAINT: hdc = BeginPaint(hwnd, &ps); GetClientRect(hwnd, &rect); wsprintf(szBuffer, szMessage[iStatus], REP, lTime); DrawText(hdc, szBuffer, -1, &rect, DT_SINGLELINE | DT_CENTER | DT_VCENTER); EndPaint(hwnd, &ps); return 0 ; case WM_DESTROY: PostQuitMessage(0); return 0; } return DefWindowProc(hwnd, message, wParam, lParam) ; }