simulate events

windows system maintains a msg queue, and any process that supports msg will create an thread that have a loop which checks its own msg queue;

we can set a callback for it through define an event.

　　　　　　　　　　
                                  

// file Eventt.h
#include <map>
#include <functional>
using namespace std;

template<class T1, class T2>
class Eventt
{
public:
    typedef void FunctionA(T1, T2);
    Eventt() :eventID(0), softwareID(0){}
    template<class T3> int addHandler(T3 t3)
    {
        m_handlers.emplace(eventID, t3);
        return eventID++;
    }

    void operator()(T1 t1, T2 t2)
    {
        for (auto i : m_handlers)    i.second(t1, t2);
    }

private:
    map<int, function<FunctionA> > m_handlers;
    int eventID;
    int softwareID;
};

#include "Eventt.h"
#include <iostream>
#include <queue>
#include <thread>
#include <stdlib.h>
#include <windows.h>
using namespace std;

// to simulate msg and event machinism used in Windows

struct Messg
{
    enum SoftType{ NUL, A, B };
    int a, b, Type;
    Messg(int aa, int bb, int cc) :a(aa), b(bb), Type(cc){}
};

struct
{
    queue<pair<int, int>> m_softA, m_softB;
    queue<Messg> m_system;
} Computr;

void fuctionA(int a, int b)
{
    cout << "software A : " << a*b << endl;
}

void fuctionB(int a, int b)
{
    cout << "software B : " << a * b <<"\t\t" << a+b << endl;
}

void FunctionCC(void)
{
    int a, b, c;
    while (1)
    {
        Sleep(1500);
        a = rand() % 100;
        b = rand() % 100;
        c = rand() % 3;
        Computr.m_system.push(Messg(a, b, c));
    }
}

void FunctionAA(void)
{
    Eventt<int, int> ea;
    // register callback
    ea.addHandler(fuctionA);
    while (1)
    {
        Sleep(1000);
        while (!Computr.m_softA.empty())
        {
            pair<int, int> msg(Computr.m_softA.front());
            ea(msg.first, msg.second);
            Computr.m_softA.pop();
        }
    }
}

void FunctionBB(void)
{
    Eventt<int, int> ea;
    ea.addHandler(fuctionB);
    while (1)
    {
        Sleep(1000);
        while (!Computr.m_softB.empty())
        {
            pair<int, int> msg(Computr.m_softB.front());
            ea(msg.first, msg.second);
            Computr.m_softB.pop();
        }
    }
}

int main() // the function main is like a system
{
    thread softA(FunctionAA), softB(FunctionBB), softC(FunctionCC);
    while (1)
    {
        Sleep(700);
        if (!Computr.m_system.empty())
        {
            Messg temp = Computr.m_system.front();
            pair<int, int> tempmsg(temp.a, temp.b);
            switch (temp.Type)
            {
            case Messg::NUL:Computr.m_softA.push(tempmsg);
                Computr.m_softB.push(tempmsg);
                break;
            case Messg::A:Computr.m_softA.push(tempmsg); // send mesg to softA
                break;
            case Messg::B:Computr.m_softB.push(tempmsg); // send mesg to softB
                break;
            default: ;
            }
            Computr.m_system.pop();
        }
    }
}