C++ IPC进程间的通信《C++多线程编程实战》

• 临界值：程序中能被访问共享内存的部分
• 2个CPP文件需要在同一个解决方案中分别创建2个项目

进程间通信示例：程序一开始就有2个进程，它们在一个普通窗口中完成绘制矩形的任务。2个进程相互通信，一个进程再画矩形时，另一个进程要等待

• IPCWorker.cpp

#include <Windows.h>
#include <tchar.h> //_tcscmp() _TCHAR*

#define COMMUNICATION_OBJECT_NAME TEXT("__FILE_MAPPING__")
#define SYNCHRONIZING_MUTEX_NAME TEXT("__TEST_MUTEX__")

typedef struct _tagCOMMUNICATIONOBJECT 
{
	HWND hWndClient;
	BOOL bExitLoop;
	LONG lSleepTimeout;
}COMMUNICATIONOBJECT, *PCOMMUNICATIONOBJECT;

int main(int argc, _TCHAR* argv[])
{
	HBRUSH hBrush = NULL;

	if (_tcscmp(TEXT("blue"), argv[0]) == 0)
	{
		hBrush = CreateSolidBrush(RGB(0, 0, 255));
	}
	else
	{
		hBrush = CreateSolidBrush(RGB(255, 0, 0));
	}

	HWND hWnd = NULL;
	HDC hDC = NULL;
	RECT rectClient = { 0 };
	LONG lWaitTimeout = 0;
	HANDLE hMapping = NULL;
	PCOMMUNICATIONOBJECT pCommObject = NULL;
	BOOL bContinueLoop = TRUE;

    //OpenMutex获得该已命名互斥量的句柄(如果有的话)
	HANDLE hMutex = OpenMutex(MUTEX_ALL_ACCESS, FALSE, SYNCHRONIZING_MUTEX_NAME);
	hMapping = OpenFileMapping(FILE_MAP_READ, FALSE, COMMUNICATION_OBJECT_NAME);

	if (hMapping)
	{
		while (bContinueLoop)
		{
			WaitForSingleObject(hMutex, INFINITE);
			//获得指向文件映像对象的句柄
			pCommObject = (PCOMMUNICATIONOBJECT)MapViewOfFile(hMapping,
				FILE_MAP_READ, 0, 0, sizeof(COMMUNICATIONOBJECT));

			if (pCommObject)
			{
				bContinueLoop = !pCommObject->bExitLoop;
				hWnd = pCommObject->hWndClient;
				lWaitTimeout = pCommObject->lSleepTimeout;
				UnmapViewOfFile(pCommObject);
				hDC = GetDC(hWnd);
				if (GetClientRect(hWnd, &rectClient))
				{
					FillRect(hDC, &rectClient, hBrush);
				}

				ReleaseDC(hWnd, hDC);
				Sleep(lWaitTimeout); //故意的,因为记录的时候,进程切换太快根本注意不到
			}
			ReleaseMutex(hMutex); //释放互斥量的所有权,让其它进程可以获得互斥量,继续执行其他任务
		}
	}

	CloseHandle(hMapping);
	CloseHandle(hMutex);
	DeleteObject(hBrush);
	return 0;
}

• IPCDemo.cpp

#include <Windows.h>
#include <iostream>
#include <tchar.h> // _TCHAR*

using namespace std;

#define COMMUNICATION_OBJECT_NAME TEXT("__FILE_MAPPING__")
#define SYNCHRONIZING_MUTEX_NAME TEXT( "__TEST_MUTEX__" )
#define WINDOW_CLASS_NAME TEXT( "__TMPWNDCLASS__" )
#define BUTTON_CLOSE 100

typedef struct _tagCOMMUNICATIONOBJECT //用于整个文件映射过程中对象之间的通信
{
	HWND hWndClient;
	BOOL bExitLoop;
	LONG lSleepTimeout;
} COMMUNICATIONOBJECT, *PCOMMUNICATIONOBJECT;

LRESULT CALLBACK WndProc(HWND hDlg, UINT uMsg, WPARAM wParam, LPARAM lParam);
HWND InitializeWnd();
PCOMMUNICATIONOBJECT pCommObject = NULL;
HANDLE hMapping = NULL;

int _tmain(int argc, _TCHAR* argv[])
{
	cout << "Interprocess communication demo." << endl;
	HWND hWnd = InitializeWnd();
	if (!hWnd)
	{
		cout << "Cannot create window!" << endl << "Error:\t" <<
			GetLastError() << endl;
		return 1;
	}
	HANDLE hMutex = CreateMutex(NULL, FALSE, SYNCHRONIZING_MUTEX_NAME);
	if (!hMutex)
	{
		cout << "Cannot create mutex!" << endl << "Error:\t" <<
			GetLastError() << endl;
		return 1;
	}
	hMapping = CreateFileMapping((HANDLE)-1, NULL, PAGE_READWRITE, 0,
		sizeof(COMMUNICATIONOBJECT), COMMUNICATION_OBJECT_NAME);
	if (!hMapping)
	{
		cout << "Cannot create mapping object!" << endl << "Error:\t"
			<< GetLastError() << endl;
		return 1;
	}
	pCommObject = (PCOMMUNICATIONOBJECT)MapViewOfFile(hMapping,
		FILE_MAP_WRITE, 0, 0, 0);
	if (pCommObject)
	{
		pCommObject->bExitLoop = FALSE;
		pCommObject->hWndClient = hWnd;
		pCommObject->lSleepTimeout = 250;
		UnmapViewOfFile(pCommObject);
	}

	STARTUPINFO startupInfoRed = { 0 };
	PROCESS_INFORMATION processInformationRed = { 0 };
	STARTUPINFO startupInfoBlue = { 0 };
	PROCESS_INFORMATION processInformationBlue = { 0 };

	BOOL bSuccess = CreateProcess(TEXT("..\\Debug\\IPCWorker.exe"),
		(LPWSTR)TEXT("red"), NULL, NULL, FALSE, 0, NULL, NULL, &startupInfoRed,
		&processInformationRed);
	if (!bSuccess)
	{
		cout << "Cannot create process red!" << endl << "Error:\t" <<
			GetLastError() << endl;
		return 1;
	}
	bSuccess = CreateProcess(TEXT("..\\Debug\\IPCWorker.exe"),
		(LPWSTR)TEXT("blue"), NULL, NULL, FALSE, 0, NULL, NULL, &startupInfoBlue,
		&processInformationBlue);
	if (!bSuccess)
	{
		cout << "Cannot create process blue!" << endl << "Error:\t" <<
			GetLastError() << endl;
		return 1;
	}
	MSG msg = { 0 };
	while (GetMessage(&msg, NULL, 0, 0))
	{
		TranslateMessage(&msg);
		DispatchMessage(&msg);
	}
	UnregisterClass(WINDOW_CLASS_NAME, GetModuleHandle(NULL));
	CloseHandle(hMapping);
	CloseHandle(hMutex);
	cout << "End program." << endl;
    return 0; 
}

LRESULT CALLBACK WndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
	switch (uMsg)
	{
	case WM_COMMAND:
	{
		switch (LOWORD(wParam))
		{
		case BUTTON_CLOSE:
		{
			PostMessage(hWnd, WM_CLOSE, 0, 0);
			break;
		}
		default:
			break;
		}
		break;
	}
	case WM_DESTROY:
	{
		pCommObject = (PCOMMUNICATIONOBJECT)MapViewOfFile(hMapping,
			         FILE_MAP_WRITE, 0, 0, 0);
		if (pCommObject)
		{
			pCommObject->bExitLoop = TRUE;
			UnmapViewOfFile(pCommObject);
		}
		PostQuitMessage(0);
		break;
	}
	default:
	{
		return DefWindowProc(hWnd, uMsg, wParam, lParam);
		break;
	}
	}

	return 0;
}

HWND InitializeWnd()
{
	WNDCLASSEX wndEx;
	wndEx.cbSize = sizeof(WNDCLASSEX);
	wndEx.style = CS_HREDRAW | CS_VREDRAW;
	wndEx.lpfnWndProc = WndProc;
	wndEx.cbClsExtra = 0;
	wndEx.cbWndExtra = 0;
	wndEx.hInstance = GetModuleHandle(NULL);
	wndEx.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
	wndEx.lpszMenuName = NULL;
	wndEx.lpszClassName = WINDOW_CLASS_NAME;
	wndEx.hCursor = LoadCursor(NULL, IDC_ARROW);
	wndEx.hIcon = LoadIcon(wndEx.hInstance, MAKEINTRESOURCE(IDI_APPLICATION));
	wndEx.hIconSm = LoadIcon(wndEx.hInstance, MAKEINTRESOURCE(IDI_APPLICATION));
	if (!RegisterClassEx(&wndEx))
	{
		return NULL;
	}
	HWND hWnd = CreateWindow(wndEx.lpszClassName,
		TEXT("Interprocess communication Demo"),
		WS_OVERLAPPEDWINDOW, 200, 200, 400, 300, NULL, NULL,
		wndEx.hInstance, NULL);
	if (!hWnd)
	{
		return NULL;
	}
	HWND hButton = CreateWindow(TEXT("BUTTON"), TEXT("Close"),
		WS_CHILD | WS_VISIBLE | BS_PUSHBUTTON | WS_TABSTOP,
		275, 225, 100, 25, hWnd, NULL, wndEx.hInstance, NULL);
	ShowWindow(hWnd, SW_SHOW);
	UpdateWindow(hWnd);

	return hWnd;
}

• 运行结果