Windows进程通信--共享内存（一）

最新推荐文章于 2024-09-18 19:16:01 发布

原创最新推荐文章于 2024-09-18 19:16:01 发布 · 403 阅读

4 ·

CC 4.0 BY-SA版权

C++ 专栏收录该内容

8 篇文章

订阅专栏

本文介绍了一个基于Windows平台的共享内存通信实例，通过使用CreateFileMapping、MapViewOfFile等API实现跨进程数据交换。代码中详细展示了如何创建和读取共享内存，以及通过事件对象同步数据读写过程。

一、知识点

主要使用了以下几个函数，具体入参等含义可以百度

1.CreateFileMapping、OpenFileMapping、MapViewOfFile

2.CreateEvent、SetEvent、ResetEvent、WaitForSingleObject

二、功能

逻辑很简单，就是：

1.先根据名称打开共享内存，打开失败的话，就去创建。然后调用MapViewOfFile获取共享内存的地址

2.启动一个线程，使用事件检测共享内存是否有数据，如果有数据的话，就去读取，然后调用数据处理函数进行处理

代码：

ShareMemory.h

#ifndef SHAREMEMORY_H
#define SHAREMEMORY_H

#include <string>
#include <thread>
#include <memory>
#include "Windows.h"

class ShareMemory
{
public:
	ShareMemory(std::wstring strKey, unsigned int nSize = 1024);
	~ShareMemory();

	void registeReceiver(std::function<void(char *)> pfunReceiver);
	void writeData(char *data, int nLength);

private:
	void readData();

private:
	std::shared_ptr<std::thread> m_ptrReadThread;
	bool m_bThreadRunning = true;

	HANDLE m_hMapFile = nullptr;
	LPVOID m_buffer = nullptr;

	std::function<void(char *)> m_pfunReceiver = nullptr;
	
	std::wstring m_strUniqueId;
	HANDLE m_writeEvent = nullptr;
};

#endif

ShareMemory.cpp

#include "stdafx.h"
#include "ShareMemory.h"
#include <iostream>


ShareMemory::ShareMemory(std::wstring strKey, unsigned int nSize)
{
	m_strUniqueId = std::move(strKey);
	m_hMapFile = OpenFileMapping(FILE_MAP_ALL_ACCESS, 0, m_strUniqueId.c_str());
	if (!m_hMapFile)
	{
		m_hMapFile = CreateFileMapping(INVALID_HANDLE_VALUE, nullptr, PAGE_READWRITE, 0, nSize, m_strUniqueId.c_str());
	}

	if (m_hMapFile)
	{
		m_buffer = MapViewOfFile(m_hMapFile, FILE_MAP_ALL_ACCESS, 0, 0, nSize);

		if (!m_buffer)
		{
			CloseHandle(m_hMapFile);
		}
		else
		{
			
			
			std::wstring strWriteKey = m_strUniqueId;
			strWriteKey.append(L"_write");
			m_writeEvent = CreateEvent(NULL, TRUE, FALSE, strWriteKey.c_str());

			memset(m_buffer, 0, nSize);
			m_ptrReadThread = std::make_shared<std::thread>(std::bind(&ShareMemory::readData, this));
		}
	}
}


ShareMemory::~ShareMemory()
{
	if (m_buffer)
	{
		UnmapViewOfFile(m_buffer);
		m_buffer = nullptr;
	}

	if (m_hMapFile)
	{
		CloseHandle(m_hMapFile);
		m_hMapFile = nullptr;
	}

	if (m_writeEvent)
	{
		CloseHandle(m_writeEvent);
		m_writeEvent = nullptr;
	}
	
}

void ShareMemory::registeReceiver(std::function<void(char *)> pfunReceiver)
{
	m_pfunReceiver = pfunReceiver;
}

void ShareMemory::writeData(char *data, int nLength)
{
	if (m_writeEvent)
	{
		memcpy(m_buffer, data, nLength);
		SetEvent(m_writeEvent);
	}	
}

void ShareMemory::readData()
{
	if (!m_writeEvent)
	{
		return;
	}

	while (m_bThreadRunning)
	{
		DWORD  dwWaitResult = WaitForSingleObject(m_writeEvent, INFINITE);
		switch (dwWaitResult)
		{
			// Event object was signaled
		case WAIT_OBJECT_0:
		{
			if (m_pfunReceiver)
			{
				char *data = (char*)m_buffer;
				int nLen = strlen(data);
				m_pfunReceiver(data);
				memset(m_buffer, 0, nLen);
				ResetEvent(m_writeEvent);
			}
			break;
		}

		default:
			std::cout<<"Wait error :" << GetLastError()<<std::endl;
			break;
		}
	}
	
	
}

写数据进程

int main(int *argc, char *argv[])
{
	ShareMemory sm(L"mysharememory");

	while (true)
    {
		char in[100];
		std::cin >> in;
		sm.writeData(in, strlen(in));
	}


	system("pause");
    return 0;
}

读数据进程

int main(int *argc, char *argv[])
{
	ShareMemory sm(L"mysharememory");

	std::string i = std::string(argv[1]);

	
	sm.registeReceiver([](char *data) {
		std::cout << data << std::endl;
	});
	

	system("pause");
    return 0;
}

三、问题

这段代码逻辑比较简单，已经实现共享内存的数据读写，但是还是有很多场景没有处理，接下来我们会对它进行修改