IO多路转接之poll

一、IO多路转接之poll

1.1poll函数接口

1.2poll函数返回值

1.3poll参数

二、poll服务器代码

2.1PollServer.hpp文件

cpp 复制代码

#pragma once
#include <iostream>
#include <sys/select.h>
#include <sys/time.h>
#include <poll.h>
#include "Sock.hpp"

static const uint16_t defaultport = 8080;
static const int fd_num_max = 64;
int defaultfd = -1;
int non_event = 0;

class PollServer
{
public:
    PollServer(uint16_t port = defaultport)
        : _port(port)
    {
        for (size_t i = 0; i < fd_num_max; i++)
        {
            _event_fds[i].fd = defaultfd;
            _event_fds[i].events = non_event;
            _event_fds[i].revents = non_event;
        }
    }

    bool Init()
    {
        _listensock.Socket();
        _listensock.Bind(_port);
        _listensock.Listen();
        return true;
    }

    void PrintFd()
    {
        std::cout << "online fd list:";
        for (int i = 0; i < fd_num_max; i++)
        {
            if (_event_fds[i].fd == defaultfd)
            {
                continue;
            }
            else
            {
                std::cout << _event_fds[i].fd << "->";
            }
        }
        std::cout << std::endl;
    }

    void Accepter()
    {
        // 连接事件就绪
        uint16_t clientport;
        std::string clientip;
        // 在此处不会在阻塞了，因为selec已经告诉我事件已经就绪
        int sock = _listensock.Accept(&clientip, &clientport);
        if (sock < 0)
        {
            return;
        }
        else
        {
            lg.logmessage(Info, "accept success! %s, %d", clientip.c_str(), clientport);
            // 这里不能直接读，因为读写事件不一定就绪，所以要直接把这里获取的sock交给select

            // 这里吧sock交给辅助数组就可以把sock交给select来监听了
            int pos = 1;
            for (; pos < fd_num_max; pos++)
            {
                if (_event_fds[pos].fd != defaultfd)
                {
                    continue;
                }
                else
                {
                    break;
                }
            }
            // 这里跳出循环有两种情况，一是找到了没有设置的数组下标，二是数组满了
            if (pos == fd_num_max)
            {
                lg.logmessage(Warning, "sorry, server is full, sockfd[%d] will close", sock);

                close(sock);
                // poll这里也可以进行扩容
            }
            else
            {
                // 找到未被设置的下标了
                _event_fds[pos].fd = sock;
                // 设置关心事件
                _event_fds[pos].events = POLLIN | POLLOUT;
                _event_fds[pos].revents = non_event;
                
                PrintFd();
            }
        }
    }

    void Recvr(int fd, int pos)
    {
        // 其他的文件描述符就绪,进行读取操作
        char buffer[1024];
        ssize_t n = read(fd, buffer, sizeof(buffer) - 1);
        if (n > 0)
        {
            buffer[n] = 0;
            std::cout << "get a message:" << buffer << std::endl;
        }
        else if (n == 0)
        {
            lg.logmessage(Info, "client quit, close fd is:%d", fd);
            _event_fds[pos].fd = defaultfd;
            close(fd);
        }
        else
        {
            lg.logmessage(Warning, "read error, fd is:%d", fd);
            _event_fds[pos].fd = defaultfd;
            close(fd);
        }
    }

    void Dispacter()
    {
        // 便利所有的文件描述符数组，因为我不知道哪一个就绪了
        for (int i = 0; i < fd_num_max; i++)
        {
            int fd = _event_fds[i].fd;
            if (fd == defaultfd)
            {
                // 不是合法的文件描述符
                continue;
            }

            if (_event_fds[i].revents & POLLIN)
            {
                if (_listensock.Fd() == fd)
                {
                    // 连接管理器
                    Accepter();
                }
                else
                {
                    Recvr(fd, i);
                }
            }
        }
    }

    void Start()
    {
        _event_fds[0].fd = _listensock.Fd();
        _event_fds[0].events = POLLIN;
        int timeout = 3000;
        for (;;)
        {

            int n = poll(_event_fds, fd_num_max, timeout);
            switch (n)
            {
            case 0:
                std::cout << "time out......" << std::endl;
                break;
            case -1:
                std::cout << "poll fail" << std::endl;
                break;
            default:
                // 有事件就绪
                std::cout << "get a link" << std::endl;
                // 处理事件
                Dispacter();
                break;
            }
        }
    }

    ~PollServer()
    {
        _listensock.Close();
    }

private:
    Sock _listensock;
    uint16_t _port;
    struct pollfd _event_fds[fd_num_max];
};

2.2 Log.hpp文件

cpp 复制代码

#pragma once

#include <iostream>
#include <stdarg.h>
#include <time.h>
#include<sys/stat.h>
#include<sys/types.h>
#include<unistd.h>
#include<stdlib.h>
#include <fcntl.h>
#include<string.h>

#define SIZE 1024

// 设置日志等级
#define Info 0
#define Debug 1
#define Warning 2
#define Error 3
#define Fatal 4

#define Screen 1
#define Onefile 2
#define Classfile 3

#define logFile "log.txt"

class log
{
public:
    log()
    {
        PrintMethod = Screen;
        path = "./log/";
    }
    void Enable(int method)
    {
        PrintMethod = method;
    }

    std::string levelToString(int level)
    {
        switch (level)
        {
        case Info:
            return "Info";
        case Debug:
            return "Debug";
        case Warning:
            return "Warning";
        case Error:
            return "Error";
        default:
            return "None";
        }
    }

    void logmessage(int level, const char *format, ...) // 后面的省略号表示可变参数
    {

        char leftbuffer[SIZE];

        time_t t = time(nullptr);
        struct tm *ctime = localtime(&t);

        snprintf(leftbuffer, sizeof(leftbuffer), "[%s],[%d-%d-%d %d:%d:%d]", levelToString(level).c_str(),
                 ctime->tm_year + 1900, ctime->tm_mon, ctime->tm_mday,
                 ctime->tm_hour, ctime->tm_min, ctime->tm_sec);

        char rightbuffer[SIZE];

        va_list s;
        va_start(s, format);
        vsnprintf(rightbuffer, sizeof(rightbuffer), format, s);
        va_end(s);

        char logtxt[SIZE * 3];
        snprintf(logtxt, sizeof(logtxt), "%s %s\n", leftbuffer, rightbuffer);

        // printf("%d-%d-%d %d:%d:%d\n",ctime->tm_year + 1900, ctime->tm_mon, ctime->tm_mday, ctime->tm_hour,ctime->tm_min,ctime->tm_sec);

        //printf("%s", logtxt);
        PrintLog(level,logtxt);
        // 格式：默认部分+自定义部分（可变参数部分）
    }

    void PrintLog(int level, const std::string& logtxt)
    {
        switch(PrintMethod)
        {
            case Screen:
                std::cout << logtxt << std::endl;
            break;
            case Onefile:
                printOneFile(logFile, logtxt);
            break;
            case Classfile:
                printClassFile(level, logtxt);
            break;
            default:
            break;
        }
    }
    void printOneFile(const std::string &logname, const std::string &logtxt)
    { 
        std::string _logname = path + logname;
        int fd = open(_logname.c_str(),O_WRONLY|O_CREAT|O_APPEND,0666);
        if(fd < 0)
        {
            return  ;
        }
        write(fd,logtxt.c_str(),logtxt.size());
        close(fd);

    }
    void printClassFile(int level, const std::string &logtxt)
    {
        std::string filename = logFile;
        filename += ".";
        filename += levelToString(level);
        printOneFile(filename, logtxt);
    }
    ~log()
    {
    }
private:
    int PrintMethod;
    std::string path;
};


log lg;

2.3 Sock.hpp文件

cpp 复制代码

#pragma once
#include <iostream>
#include <string>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <cstring>
#include "Log.hpp"

const int backlog = 10;
extern log lg;

enum
{
    SocketError = 2,
    BindError,
    ListenError
};

class Sock
{
public:
    Sock()
    : _sockfd(-1)
    {
    }

    ~Sock()
    {
        if (_sockfd >= 0)
        {
            close(_sockfd);
        }
    }

    // 创建套接字
    void Socket()
    {
        _sockfd = socket(AF_INET, SOCK_STREAM, 0);
        if (_sockfd < 0)
        {
            lg.logmessage(Fatal, "socket fail, %s, %d", errno, strerror(errno));
            exit(SocketError);
        }
        int opt = -1;
        setsockopt(_sockfd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));
    }

    // 创建一个绑定接口
    void Bind(const uint16_t port)
    {
        struct sockaddr_in local;
        memset(&local, 0, sizeof(local));
        local.sin_family = AF_INET;
        local.sin_port = htons(port);
        local.sin_addr.s_addr = INADDR_ANY;

        if (bind(_sockfd, (struct sockaddr *)&local, sizeof(local)) < 0)
        {
            lg.logmessage(Fatal, "bind fail, %s, %d", errno, strerror(errno));
            exit(BindError);
        }
    }

    void Listen()
    {
        if (listen(_sockfd, backlog) < 0)
        {
            lg.logmessage(Fatal, "listen fail, %s, %d", errno, strerror(errno));
            exit(ListenError);
        }
    }

    int Accept(std::string *clientip, uint16_t *clientport)
    {
        struct sockaddr_in peer;
        socklen_t len = sizeof(peer);
        int newfd = accept(_sockfd, (struct sockaddr *)&peer, &len);
        if (newfd < 0)
        {
            lg.logmessage(Warning, "accept fail, %s, %d", errno, strerror(errno));
            return -1;
        }

        char ipstr[64];
        inet_ntop(AF_INET, &peer.sin_addr, ipstr, sizeof(ipstr));
        // 获取远端主机的信息
        *clientport = ntohs(peer.sin_port);
        *clientip = ipstr;

        return newfd;
    }

    bool Connect(const std::string &ip, const uint16_t &port)
    {
        struct sockaddr_in peer;
        memset(&peer, 0, sizeof(peer));
        peer.sin_family = AF_INET;
        peer.sin_port = htons(port);
        inet_pton(AF_INET, ip.c_str(), &peer.sin_addr);

        int n = connect(_sockfd, (struct sockaddr *)&peer, sizeof(peer));
        if (n == -1)
        {
            std::cerr << "connect to" << ip << ":" << port << std::endl;
            return false;
        }
        return true;
    }

    void Close()
    {
        close(_sockfd);
    }

    int Fd()
    {
        return _sockfd;
    }

private:
    int _sockfd;
};

2.4main.cc文件

cpp 复制代码

#include "PollServer.hpp"
#include <memory>

int main()
{
    std::unique_ptr<PollServer> svr(new PollServer());
    svr->Init();
    svr->Start();

    return 0;
}

三、poll的优缺点

3.1 poll的优点

(1)不同于select使用三个位图来表示三个fdset的方式，poll使用一个pollfd的指针实现。

(2)pollfd结构包含了要监视的event和发生的event，不再使用select"参数---值"传递的方式，接口使用比select更方便。

(3）poll并没有最大数量限制（但是数量过大后性能也是会下降）。

3.2 poll的缺点

当poll中监听的文件描述符数目增多时：

（1）poll和select函数一样，poll返回后，需要轮询pollfd来获取就绪的描述符。

（2）每次调用poll都需要把大量的pollfd结构从用户态拷贝到内核中。

（3）同时连接的大量客户端在一时刻可能只有很少的处于就绪状态，因此随着监视的描述符数量的增长，其效率也会线性下降。