C++常用代码

构造

#include<iostream>
#include<list>
using namespace std;
class A
{
private:
	int a;
	int *buf;
public: 
	A(){//构造
		a = 0;
		buf = new int[100];
		cout << "A" << endl;
	}
	~A(){//析构
		if (buf != nullptr)
		{
			delete[]buf;
			cout << "~A" << endl;
		}
	}
	A(const A &tmp)//拷贝构造函数 //= delete;
	{
        if(this!=&tmp)//检查自己拷贝自己
        {
          this->a = tmp.a;
          this->buf = new int[100];
          cout << "copy A" << endl;
        }
	} 
	A( A &&tmp)//移动构造
	{
		cout << "move A" << endl;
		this->a = tmp.a;
		this->buf = tmp.buf;
		tmp.buf = nullptr;
	}
	A& operator=(const A &temp)//赋值函数    // = delete;
	{
		this->a = temp.a;
		this->buf = new int[100];
		cout << "= A" << endl;
		return *this;
	}
	
	A operator=( A &&temp)//移动赋值
	{
		cout << "move =  A" << endl;
		this->a = temp.a;
		this->buf = temp.buf;
		temp.buf = nullptr; // 置为空指针
		return std::move(*this);//变量强制转右值
	}
	A copyA(A&a)
	{
		return std::move(a);
	}
};
int main()
{
	list<A> list_;
	for (auto a : { 1, 2, 4 })
	{
		cout << "-------begin------" << endl << endl;
		list_.push_back(A());
	}
	cout << "-------1------" << endl;
	list_.clear();
	cout << "-------2------" << endl;
	{
		A a;
		A b = a;
		const A c;
		A d = c;
	}
	getc(stdin);
	return 1;
}
输出
-------begin------
A
move A
-------begin------
A
move A
-------begin------
A
move A
-------1------
~A
~A
~A
-------2------
A
copy A
A
copy A
~A
~A
~A
~A

智能指针

#include<iostream>
#include<list>
#include<memory>
using namespace std;

int cnt = 0; //记录C的分配析构次数
class C
{
public:
	int c;
public:
	C(int aa) :c(aa)
	{
		cnt++;
		cout << "C" << endl;
	}
	~C()
	{
		cnt--;
		cout << "~C" << endl;
	}
	C(const C&)
	{
		cout << "C copy" << endl;
		cnt++;
	}
};
int a = 0; //记录B的分配析构次数
class B
{
public:

	std::shared_ptr<C> buf = nullptr;
public:

	B() {

		buf = make_shared<C>(3);
		cout << "B" << endl;
		a++;
	}
	~B() {
		if (buf != nullptr)
		{
			a--;
			cout << "~B" << endl;
		}
	}


	B(const B& tmp) //= delete;
	{

		this->buf = make_shared<C>(*tmp.buf);
		a++;
		cout << "copy B" << endl;
		//return *this;
	}

	B(B&& tmp)
	{
		cout << "move B" << endl;
		this->buf = tmp.buf;
		tmp.buf = nullptr;
	}



	B& operator=(const B& temp)// = delete;
	{
		a++;

		this->buf = make_shared<C>(*temp.buf);
		cout << "= B" << endl;
		return *this;
	}

	B&& operator=(B&& temp)
	{
		cout << "move =  B" << endl;

		this->buf = temp.buf;
		temp.buf = nullptr;
		return std::move(*this);
	}

};

int main()
{
	list<B> list_;
	for (auto a : { 1, 2, 4 })
	{
		cout << "-------begin------" << endl << endl;
		list_.push_back(B());
	}
	cout << "-------1------" << endl;
	list_.clear();
	cout << "-------2------" << endl;
	{
		B a;
		B b = a;

	}
	cout << "a = " << a << "cnt = " << cnt << endl;
	getc(stdin);
	return 1;
}
结果:
-------begin------

C
B
move B
-------begin------

C
B
move B
-------begin------

C
B
move B
-------1------
~B
~C
~B
~C
~B
~C
-------2------
C
B
C copy
copy B
~B
~C
~B
~C
a = 0cnt = 0

进程间通信

消息(Message)队列：消息队列是消息链式队列，消息被读完就删除，可以供多个进程间通信。有足够权限的进程可以向队列中添加消息，被赋予读权限的进程则可以读走队列中的消息。消息队列克服了信号承载信息量少，管道只能承载无格式字节流以及缓冲区大小受限等缺点。

共享内存：使得多个进程可以访问同一块内存空间，是最快的可用IPC形式。

/**
 * @file	share-memory.h
 * @brief   进程间通信-共享内存头文件封装
 *              共享内存创建之后，一直存在于内核中，读完之后，内容还存在，直到被删除或系统关闭
 * @author	yanjingang
 */
#pragma once

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/shm.h>
#include <unistd.h>
#include <iostream>

#define PATHNAME "."
#define PROCID 'b' //0x6666
#define MEMSIZE 4096*1

using namespace