匿名管道+进程池+命名管道

mkfifo name_pipe

创建管道文件。

命名管道：

路径+文件名具有唯一性。

匿名管道：

进程池代码：

#include<iostream>
#include<unistd.h>
#include<cstdlib>
#include<cassert>
#include<vector>
#include<string>
#include<ctime>
#include<sys/types.h>
#include<sys/wait.h>


#define PROCESS_NUM 5
#define MakeSeed() srand((unsigned long)time(nullptr))

typedef void(*func_t)();

using namespace std;
class subEp
{
public:    
    subEp(pid_t subId,int wirteFd)
        :subId_(subId),wirteFd_(wirteFd)
        {
            char nameBuffer[1024];
            snprintf(nameBuffer,sizeof nameBuffer,"process-%d[pid(%d)-fd(%d)]",num++,subId_,wirteFd_);
            name_=nameBuffer;
        }
    static int num;
    string name_;
    pid_t subId_;//进程id
    int wirteFd_;//fd[0] fd[1]文件描述符
};
int subEp::num=0;

void downLoadTask()
{
    cout<<getpid()<<":下载任务\n"<<endl;
    sleep(1);
}
void ioTask()
{
    cout<<getpid()<<"IO任务\n"<<endl;
}
void flushTask()
{
    cout<<getpid()<<"刷新任务\n"<<endl;
}
void loadTaskFunc(vector<func_t>* out)
{
    assert(out);
    out->push_back(downLoadTask);
    out->push_back(ioTask);
    out->push_back(flushTask);
}
int recvTask(int readFd)
{
    int code=0;
    ssize_t s=read(readFd,&code,sizeof code);
    assert(s==sizeof(int));
    if(s==4) return code;
    else if(s<=0) return -1;
}

void createSubProcess(vector<subEp>* subs,vector<func_t>& funcMap)
{
    for(int i=0;i<PROCESS_NUM;i++)
    {
        int fds[2];
        int n=pipe(fds);
        assert(n==0);
        (void)n;
        pid_t id=fork();
        if(id==0)
        {
            //子进程，进行读
            close(fds[1]);          
            while(true)
            {
                //1.获取命令码，如果没有发送，子进程应该阻塞
                int commenCode=recvTask(fds[0]);
                //2.完成任务
                if(commenCode>=0&&commenCode<funcMap.size())
                    funcMap[commenCode]();
                else if(commenCode==-1)
                    break;
            }
            exit(0);
        }
        close(fds[0]);
        subEp sub(id,fds[1]);
    }
}
void sendTask(const subEp& process,int tasknum)
{
    cout<<"send task num"<<tasknum<<"sent to -> "<< process.name_<<endl;
    int n=write(process.wirteFd_,&tasknum,sizeof(tasknum));
    assert(n==sizeof(int));
    (void)n;
}
void loadBalanceContrl(vector<subEp> subs,vector<func_t> funcMap,int count)
{
    //进程个数
    int processnum=subs.size();
    //任务个数
    int tasknum=funcMap.size();
    bool quit=false;
    bool forever=(count==0?true:false);
    while(!quit)
    {
        //1.选择一个字进程 --> vector<subEp> -> index 随机数
        int subIdx=rand()%processnum;
        //2.选择一个任务 --> vector<func_t> -> index
        int taskIdx=rand()%tasknum;
        //3.将任务发送给选择的进程
        sendTask(subs[subIdx],taskIdx);
        sleep(1);
        if(!forever)
        {
            count--;
            if(count==0)
                break;
        }
        //write quit -> read 0
        for(int i=0;i<processnum;i++)
        {
            close(subs[i].wirteFd_);
        }
    }
}
void waitProcess(vector<subEp> process)
{
    int processnum=process.size();
    for(int i=0;i<processnum;i++)
    {
        waitpid(process[i].subId_,nullptr,0);
        cout<<"wait sub process success ..."<<process[i].subId_<<endl;
    }
}
int main()
{
    MakeSeed();
    //1.建立子进程并建立和子进程通信的管道
    //1.1  加载方法表
    vector<func_t> funcMap;
    loadTaskFunc(&funcMap);
    //1.2创建子进程，并且维护好父进程通信信道
    vector<subEp> subs;
    createSubProcess(&subs,funcMap);
    //2.到达父进程，父进程控制子进程，负责负载均衡的想子进程发送命令码
    int taskCnt=3;
    loadBalanceContrl(subs,funcMap,taskCnt);
    //3.回收子进程信息
    waitProcess(subs);
    
    return 0;
}

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

       int shmget(key_t key, size_t size, int shmflg);

通过ftok()创建key

key能进行唯一性标识

共享内存原理理解：

1.进程间通信，是专门设计的，用来ipc

2.共享内存时一种通信方式，所有需要通信的进程均可以使用

3.OS中一定可能会同时存在很多共享内存

ipcs -m

------ Shared Memory Segments --------
key        shmid      owner      perms      bytes      nattch     status  

查看共享内存。

ipc资源的特征：

共享内存的生命周期是随OS的，不是随进程的。

client.cc

#include"comm.hpp"

int main()
{
    int wfd=open(NAMED_PIPE,O_WRONLY);
    if(wfd<0) exit(1);
    char buffer[1024];
    while(true)
    {
        cout<<"Please Say# ";
        fgets(buffer,sizeof(buffer),stdin);
        ssize_t n=write(wfd,buffer,strlen(buffer));
        assert(n=strlen(buffer));
        (void)n;
    }
    close(wfd);
    return 0;
}

server.cc

#include"comm.hpp"

int main()
{
    bool r=createFifo(NAMED_PIPE);
    // assert(r);
    // (void)r;

    int rfd=open(NAMED_PIPE,O_RDONLY);
    if(rfd<0) exit(1);
    //read
    char buffer[1024];
    while(true)
    {
        ssize_t s=read(rfd,buffer,sizeof(buffer)-1);
        if(s>0)
        {
            buffer[s]=0;
            cout<<"client->server# "<<buffer<<endl;
        }
        else if(s==0)
        {
            cout<<"client quit, me too!!!"<<endl;
            break;
        }
        else
        {
            cout<<"err string: "<<strerror(errno)<<endl;
            break;
        }
    }
    close(rfd);

    removeFifo(NAMED_PIPE);
    return 0;
}

comm.hpp

#pragma once

#include<iostream>
#include<cstring>
#include<cerrno>
#include<string>
#include<cassert>
#include<unistd.h>
#include<fcntl.h>
#include<sys/types.h>
#include<sys/stat.h>


#define NAMED_PIPE "/tmp/mypipe.xxx"


using namespace std;
bool createFifo(const string &path)
{
    umask(0);
    int n=mkfifo(path.c_str(),0600);
    if(n==0) return true;
    else
    {
        cout<<"errno: "<<errno<<"err string: "<<strerror(errno)<<endl;
    }
}
void removeFifo(const string &path)
{
    int n=unlink(path.c_str());
    assert(n==0);
    (void)n;
}