move与函数指针的简单使用

std::move()

C++11的标准库提供了一个非常有用的函数 std::move()，std::move() 函数将一个左值强制转化为右值引用，以用于移动语义。

就是说 std::move(str); 之后原来的值因为变成了右值失效了
但是这样赋值可以避免出现拷贝

#include <iostream>
#include <string>
#include <vector>
using namespace std;int main()
{string str = "hello";cout << "before str: " << str << endl;vector<string> vstr;vstr.emplace_back(std::move(str));cout << "after  str: " << str << endl;return 0;
}

str 就没有了因为被转移语义了


#include <iostream>
#include <functional>
#include <utility>
#include "tinyNetWorkLib.h"
class People{using actionEvent = std::function<void()>;public:People():value(2){}People(int v):value(v){}void setCryEvent(actionEvent func){ cry = std::move(func); }void setSimleEvent(actionEvent func){ smile = std::move(func);}void handleEvent(Timestamp receiverTime){if(value >= 0){smile(); cout<<receiverTime.toFormattedString()<<endl;}else{cry();cout<<receiverTime.toFormattedString()<<endl;}}
private:actionEvent cry;actionEvent smile;int value;
};
int main()
{std::function<void()> func = []{std:: cout<<"happy"<<std::endl;       };std::function<void()> func2 = []{std::cout<<"cry"<<std::endl;};People peo;peo.setCryEvent(func2);peo.setSimleEvent(func);peo.handleEvent(Timestamp ::now());// std::cout << "Hello world" << std::endl;return 0;
}

执行结果

happy
2023/08/27 20:49:59

这里函数指针还能用,因为这里转移语义的对象是参数

给出依赖文件的代码Timestamp 复制下来用就好

记得给个#ifndef这里自己

#include <functional>
#include <set>
#include <sys/time.h>
#include <sys/eventfd.h>
#include <fcntl.h>
#include <unistd.h>
#include  <mutex>
#include<unordered_map>
using namespace std;
class Timestamp
{
public:Timestamp(): microSecondsSinceEpoch_(0){}explicit Timestamp(int64_t microSecondsSinceEpoch): microSecondsSinceEpoch_(microSecondsSinceEpoch){}// 获取当前时间戳static Timestamp now();//用std::string形式返回,格式[millisec].[microsec]std::string toString() const;//格式, "%4d年%02d月%02d日 星期%d %02d:%02d:%02d.%06d",时分秒.微秒std::string toFormattedString(bool showMicroseconds = false) const;//返回当前时间戳的微妙int64_t microSecondsSinceEpoch() const { return microSecondsSinceEpoch_; }//返回当前时间戳的秒数time_t secondsSinceEpoch() const{ return static_cast<time_t>(microSecondsSinceEpoch_ / kMicroSecondsPerSecond); }// 失效的时间戳，返回一个值为0的Timestampstatic Timestamp invalid(){return Timestamp();}// 1秒=1000*1000微妙static const int kMicroSecondsPerSecond = 1000 * 1000;private:// 表示时间戳的微秒数(自epoch开始经历的微妙数)int64_t microSecondsSinceEpoch_;
};/*** 定时器需要比较时间戳，因此需要重载运算符*/
inline bool operator<(Timestamp lhs, Timestamp rhs)
{return lhs.microSecondsSinceEpoch() < rhs.microSecondsSinceEpoch();
}inline bool operator==(Timestamp lhs, Timestamp rhs)
{return lhs.microSecondsSinceEpoch() == rhs.microSecondsSinceEpoch();
}// 如果是重复定时任务就会对此时间戳进行增加。
inline Timestamp addTime(Timestamp timestamp, double seconds)
{// 将延时的秒数转换为微妙int64_t delta = static_cast<int64_t>(seconds * Timestamp::kMicroSecondsPerSecond);// 返回新增时后的时间戳return Timestamp(timestamp.microSecondsSinceEpoch() + delta);
}Timestamp Timestamp::now()
{struct timeval tv;// 获取微妙和秒// 在x86-64平台gettimeofday()已不是系统调用,不会陷入内核, 多次调用不会有性能损失.gettimeofday(&tv, NULL);int64_t seconds = tv.tv_sec;// 转换为微妙return Timestamp(seconds * kMicroSecondsPerSecond + tv.tv_usec);
}// 2022/08/26 16:29:10
// 20220826 16:29:10.773804
std::string Timestamp::toFormattedString(bool showMicroseconds) const
{char buf[64] = {0};time_t seconds = static_cast<time_t>(microSecondsSinceEpoch_ / kMicroSecondsPerSecond);// 使用localtime函数将秒数格式化成日历时间tm *tm_time = localtime(&seconds);if (showMicroseconds){int microseconds = static_cast<int>(microSecondsSinceEpoch_ % kMicroSecondsPerSecond);snprintf(buf, sizeof(buf), "%4d/%02d/%02d %02d:%02d:%02d.%06d",tm_time->tm_year + 1900,tm_time->tm_mon + 1,tm_time->tm_mday,tm_time->tm_hour,tm_time->tm_min,tm_time->tm_sec,microseconds);}else{snprintf(buf, sizeof(buf), "%4d/%02d/%02d %02d:%02d:%02d",tm_time->tm_year + 1900,tm_time->tm_mon + 1,tm_time->tm_mday,tm_time->tm_hour,tm_time->tm_min,tm_time->tm_sec);}return buf;
}

最后我们给出要给第一个版本的channel

一个文件描述符,发生读事件写时间关闭事件错误事
文件描述符就是一个整形变量
int revents 表示这个文件描述符的心情(状态)
通过位运算表示和EPOLLINT OUT HUB 先不管

#include <functional>
#include "tinyNetWorkLib.h"
#include <sys/epoll.h>class Channel{using EventCallback = std::function<void()>;using ReadEventCallback = std::function<void(Timestamp)>;
public:    Channel(int fd):fd_(fd){};void setReadCallback(ReadEventCallback cb) { readCallback_ = std::move(cb); }void setWriteCallback(EventCallback cb) { writeCallback_ = std::move(cb); }void setCloseCallback(EventCallback cb) { closeCallback_ = std::move(cb); }void setErrorCallback(EventCallback cb) { errorCallback_ = std::move(cb); } void set_revents(int revt){ revents = revt; }void handleWithGuard(Timestamp receiverTime){if(revents & EPOLLHUP && !(revents & EPOLLIN)){if(closeCallback_){closeCallback_();}}if(revents & EPOLLERR){if(errorCallback_){errorCallback_();}    }if(revents & (EPOLLIN|EPOLLPRI)){if(readCallback_){readCallback_(receiverTime);}}if(revents & EPOLLOUT){if(writeCallback_){writeCallback_();}}}private:ReadEventCallback readCallback_;EventCallback writeCallback_;EventCallback closeCallback_;EventCallback errorCallback_;const int fd_;int revents;};

这个和我们People类设计几乎一样除了设计了一点系统知识

#include <iostream>
#include <functional>
#include <utility>
#include "tinyNetWorkLib.h"
#include "Channel.h"
class People{using actionEvent = std::function<void()>;public:People():value(2){}People(int v):value(v){}void setCryEvent(actionEvent func){ cry = std::move(func); }void setSimleEvent(actionEvent func){ smile = std::move(func);}void handleEvent(Timestamp receiverTime){if(value >= 0){smile(); cout<<receiverTime.toFormattedString()<<endl;}else{cry();cout<<receiverTime.toFormattedString()<<endl;}}int set_value(int v){value = v;}
private:actionEvent cry;actionEvent smile;int value;
};
int main()
{std::function<void()> func = []{std:: cout<<"happy"<<std::endl;       };std::function<void()> func2 = []{std::cout<<"cry"<<std::endl;};// People peo;// peo.setCryEvent(func2);// peo.setSimleEvent(func);//  peo.handleEvent(Timestamp ::now());// std::cout << "Hello world" << std::endl;// func();Channel chanel(1);chanel.set_revents(EPOLLOUT);chanel.setWriteCallback(func);chanel.handleWithGuard(Timestamp::now());return 0;
}