C++定时器
定时器：管理大量延时任务的模块，异步任务
addTimer(1000, func);
addTimer(1000, func);
addTimer(1000, func);
addTimer(1000, func);
数据结构： 有序结构， 增删改后仍然有序
最近要被触发的定时任务
可用：set/map/multiset/multiset/
跳表skiplist
时间轮
触发机制： 不要占用线程或者系统性能（sleep）
任务如何组织？
C语言：
struct TimerNode {
time_t expire;//not unique
callback func;
void* ctx;//args
};
C++11:
struct TimerNode {
time_t expire;//not unique
uint64_t id;//用于set数据结构
using callback = std::function<void(const TimerNode&)>;
callback func;
};
优化
=====》
struct TimerNodeBase {
time_t expire;//not unique
uint64_t id;//用于set数据结
};
struct TimerNode : public TimerNodeBase {
callback func;//函数对象，拷贝成本高，所以通过继承现剥离
TimerNode(int times, int i, callback f) : expire:(times), func(f) , id(i) {}
};
-===》 std::set<TimerNode > //用object而不是指针，为了简化，不用单独维护指针
//借助C++14 等价key
bool operator<(const TimerNodeBase &, const TimerNodeBase &) {
if (l.expire < r.expire)
return true;
else if (l.expire > r.expire)
return false;
else
return l.id < r.id;
}
class Timer {
public:
static inline time_t GetTicks() {
//返回最近的系统启动时间到当前时间，单位ms，
return std::chrono::duration_cast<chrono::milliseconds>(chrono::steady_clock::now().time_since_epoch()).count();
//这里用steady_clock而不是system_clock是因为前者在修改系统时间不受影响
}
TimerNodeBase AddTimer(int msec, callback func) {
time_t exp = GetTick() + msec;
auto pairs = timeouts.emplace(exp, GetId(), func);
return (TimerNodeBase)*pairs.first;
}
void DelTimer(TimerNodeBase node) {
auto iter = timesout.find(node);
if (iter != timesout.end())
timesout.erase(iter);
}
private:
static inline uint64_t GetId() {
return gid++;
}
static uint64_t gid;
set<TimerNode, std::less<>> timeouts;
};
timerfd linux 2.6 内核用fd来管理定时器
creat timerfd
方式：
1 read(fd);
2. epoll //检测time事件
int main() {
int epfd = epoll_create(1);//大于0即可
int timerfd = timerfd_create(CLOCK_MONOTONIC, 0);
//注册事件
struct epoll_event ev = {.events= EPOLLIN | EPOLLET};//EPOLLET:edge trigger,only once边缘触发
epoll_ctl(epfd, EPOLL_CTL_ADD, timerfd, &ev);
//用unique ptr实现单例
unique_ptr<Timer> timer = make_unique<Timer>();
int i = 0;
timer->AddTimer(1000, [&](const TimerNode& node) {
});
//事件检测流程
struct epoll_event evs[64] = {0};
while (1) {
int n = epoll_wait(epfd, evs, 64, -1);
/handle timer
}
}
完整代码如下：
#include <sys/epoll.h>
#include <functional>
#include <chrono>
#include <set>
#include <memory>
#include <iostream>using namespace std;struct TimerNodeBase {time_t expire;int64_t id;
};struct TimerNode : public TimerNodeBase {using Callback = std::function<void(const TimerNode &node)>;Callback func;
};bool operator < (const TimerNodeBase &lhd, const TimerNodeBase &rhd) {if (lhd.expire < rhd.expire)return true;else if (lhd.expire > rhd.expire) return false;return lhd.id < rhd.id;
}class Timer {
public:static time_t GetTick() {auto sc = chrono::time_point_cast<chrono::milliseconds>(chrono::steady_clock::now());auto temp = chrono::duration_cast<chrono::milliseconds>(sc.time_since_epoch());return temp.count();}static int64_t GenID() {return ++gid;}TimerNodeBase AddTimer(time_t msec, TimerNode::Callback func) {TimerNode tnode;tnode.expire = GetTick() + msec;tnode.func = func;tnode.id = GenID();timermap.insert(tnode);return static_cast<TimerNodeBase>(tnode);}bool DelTimer(TimerNodeBase &node) {auto iter = timermap.find(node);if (iter != timermap.end()) {timermap.erase(iter);return true;}return false;}bool CheckTimer() {auto iter = timermap.begin();if (iter != timermap.end() && iter->expire <= GetTick()) {iter->func(*iter);timermap.erase(iter);return true;}return false;}time_t TimeToSleep() {auto iter = timermap.begin();if (iter == timermap.end()) {return -1;}time_t diss = iter->expire-GetTick();return diss > 0 ? diss : 0;}
private:static int64_t gid;set<TimerNode, std::less<>> timermap;
};
int64_t Timer::gid = 0;int main() {int epfd = epoll_create(1);unique_ptr<Timer> timer = make_unique<Timer>();int i =0;timer->AddTimer(1000, [&](const TimerNode &node) {cout << Timer::GetTick() << "node id:" << node.id << " revoked times:" << ++i << endl;});timer->AddTimer(1000, [&](const TimerNode &node) {cout << Timer::GetTick() << "node id:" << node.id << " revoked times:" << ++i << endl;});timer->AddTimer(3000, [&](const TimerNode &node) {cout << Timer::GetTick() << "node id:" << node.id << " revoked times:" << ++i << endl;});auto node = timer->AddTimer(2100, [&](const TimerNode &node) {cout << Timer::GetTick() << "node id:" << node.id << " revoked times:" << ++i << endl;});timer->DelTimer(node);cout << "now time:" << Timer::GetTick() << endl;epoll_event ev[64] = {0};while (true) {/*-1 永久阻塞0 没有事件立刻返回，有事件就拷贝到 ev 数组当中t > 0 阻塞等待 t ms， timeout 最近触发的定时任务离当前的时间*/int n = epoll_wait(epfd, ev, 64, timer->TimeToSleep());for (int i = 0; i < n; i++) {/**/}/* 处理定时事件*/while(timer->CheckTimer());}return 0;
}