【Linux篇】共享内存实战：打造高性能服务端与客户端通信的终极指南（赋源码）

#include <sys/ipc.h>
#include <sys/shm.h>
#include <stdio.h>
#include <stdlib.h>

int main() {
    // 创建共享内存
    int shmid = shmget(IPC_PRIVATE, 1024, IPC_CREAT | 0666);
    if (shmid == -1) {
        perror("shmget failed");
        return -1;
    }

    // 获取共享内存的状态
    struct shmid_ds shm_info;
    if (shmctl(shmid, IPC_STAT, &shm_info) == -1) {
        perror("shmctl IPC_STAT failed");
        return -1;
    }

    // 打印共享内存信息
    printf("Shared memory size: %zu bytes\n", shm_info.shm_segsz);
    printf("Last attach time: %s", ctime(&shm_info.shm_atime));

    // 删除共享内存
    if (shmctl(shmid, IPC_RMID, NULL) == -1) {
        perror("shmctl IPC_RMID failed");
        return -1;
    }

    return 0;
}

#pragma once

#include <iostream>
#include <cstdio>
#include <string>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <unistd.h>
#include "comm.hpp"

const int defaultid = 1;
const int gsize = 4096;
const std::string pathname = ".";
const int projid = 0X66;
const int gmode = 0666;
#define CREATER "creater"
#define USER "user"

class Shm
{
private:
    void CreateHelper(int flg)
    {
        printf("key: 0x%x\n", _key);
        // 共享内存的生命周期，随内核
        // shmget() 会失败（因为共享内存已存在），导致程序直接终止。
        _shmid = shmget(_key, _size, flg);
        if (_shmid < 0)
        {
            ERR_EXIT("shmget");
        }
        printf("shmid: %d\n", _shmid);
    }
    void Create()
    {
        CreateHelper(IPC_CREAT | IPC_EXCL | gmode);
    }
    void Attach()
    {
        _start_mem = shmat(_shmid, nullptr, 0);
        if ((long long)_start_mem < 0)
        {
            ERR_EXIT("shmat");
        }
        printf("attach success\n");
    }
    void Detach()
    {
        int n = shmdt(_start_mem);//去关联系统调用
        if (n == 0)
        {
            printf("detach success\n");
        }
    }
    void Get()
    {
        CreateHelper(IPC_CREAT); // 不存在则创建；否则打开它，并返回
    }
    void Destory()
    {
        Detach();
        if (_usertype == CREATER)
        {
            int n = shmctl(_shmid, IPC_RMID, nullptr);
            if (n >= 0)
            {
                printf("shmcyl delete shm: %d success!\n", _shmid);
            }
            else
            {
                ERR_EXIT("shmctl");
            }
        }
    }

public:
    Shm(const std::string &pathname, int projid, const std::string &usertype)
        : _shmid(defaultid),
          _size(gsize),
          _start_mem(nullptr),
          _usertype(usertype)
    {
        _key = ftok(pathname.c_str(), projid); // 手动创建key值,用于让不同的进程看到一份资源(共享内存)
        if (_key < 0)
        {
            ERR_EXIT("ftok");
        }
        if (_usertype == CREATER)
            Create();
        else if (_usertype == USER)
            Get();
        else
        {
        }
        Attach();
    }
    void *VirtualAddr()
    {
        printf("VirtualAddr: %p\n", _start_mem); // 存在于堆栈区间的虚拟地址,堆栈之间的空间是共享区，
        // 属于用户的空间，不需要用系统调用
        // 共享内存是进程间通信最快的方式：原因1:映射之后直接被对方看到，原因2:不需要系统调用，花费额外的时间开销
        return _start_mem;
    }
    int Size()
    {
        return _size;
    }
    void Attr()
    {
        struct shmid_ds ds;
        int n =shmctl(_shmid, IPC_STAT,&ds);
        printf("shm_segsz: %ld\n",ds.shm_segsz);
        printf("key: 0x%x\n",ds.shm_perm.__key);
    }
    ~Shm()
    {
        if (_usertype == CREATER)
            Destory();
    }

private:
    int _shmid;
    key_t _key;
    int _size;
    void *_start_mem;
    std::string _usertype;
};

#pragma once
#include <iostream>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string>
#include <unistd.h>
#include <cstdio>
#include "comm.hpp"

#define PATH "."
#define FIFENAME "fifo"

class NameFifo
{
public:
    NameFifo(const std::string &path, const std::string &name)
        : _path(path), _name(name)
    {
        _filoname = _path + "/" + _name;
        umask(0);
        // 新建管道
        int n = mkfifo(_filoname.c_str(), 0666);
        if (n < 0)
        {
            ERR_EXIT("mkfifo");
        }
        else
        {
            std::cout << "mkfifo success" << std::endl;
        }
    }

    ~NameFifo()
    {
        // 删除管道文件
        int n = unlink(_filoname.c_str());
        if (n == 0)
        {
            //ERR_EXIT("unlink");
        }
        else
        {
            std::cout << "remove fifo failed" << std::endl;
        }
    }

private:
    std::string _path;
    std::string _name;
    std::string _filoname;
};

class FileOper
{
public:
    FileOper(const std::string &path, const std::string &name)
        : _path(path), _name(name), _fd(-1)
    {
        _filoname = _path + "/" + _name;
    }
    void OpenForRead()
    {
        // 打开管道文件
        _fd = open(_filoname.c_str(), O_RDONLY);
        if (_fd < 0)
        {
            ERR_EXIT("open");
        }
        std::cout << "open fifo sucess" << std::endl;
    }
    void OpenForWrite()
    {
        // write
        _fd = open(_filoname.c_str(), O_WRONLY);
        if (_fd < 0)
        {
            ERR_EXIT("open");
        }
        std::cout << "open fifo success" << std::endl;
    }
    void Wakeup()
    {
        // 写入操作
        char c = 'c';
        int n = write(_fd, &c, 1);
        printf("尝试唤醒: %d\n", n);
    }
    bool Wait()
    {
        char c;
        int number = read(_fd, &c, 1);
        if (number > 0)
        {
            printf("醒来: %d\n", number);
            return true;
        }
        return false;
    }
    void Close()
    {
        if (_fd > 0)
            close(_fd);
    }
    ~FileOper()
    {
    }

private:
    std::string _path;
    std::string _name;
    std::string _filoname;
    int _fd;
};