<h2 id="event-base">EventBase: events dispatcher</h2>
EventBase is an events dispatcher，use epoll/kqueue to handle non-blocking I/O
```c
EventBase base;

//call epoll_wait repeatedly, handle I/O events
base.loop();

//exit events loop, can be called from other threads
base.exit();

bool exited();

TcpConnPtr con = TcpConn::createConnection(&base, host, port);

TcpServer echo(&base);

void safeCall(const Task& task);

base.safeCall([](con){con->send("OK");});

//interval: 0：once task；>0：repeated task, task will be execute every interval milliseconds
TimerId runAfter(int64_t milli, const Task& task, int64_t interval=0);
//runAt will specify the absolute time
TimerId runAt(int64_t milli, const Task& task, int64_t interval=0)
//cancel Task, Ignore if task is already removed or expired.
bool cancel(TimerId timerid);

TimerId tid = base.runAfter(1000, []{ info("a second passed"); });
base.cancel(tid);

###Message mode
you can onRead or onMsg to handle message
```c
//message callback, confict with onRead callback. You should set only one of these
//codec will be released when connection destroyed
void onMsg(CodecBase* codec, const MsgCallBack& cb);
//send message
void sendMsg(Slice msg);

con->onMsg(new LineCodec, [](const TcpConnPtr& con, Slice msg) {
    info("recv msg: %.*s", (int)msg.size(), msg.data());
    con->sendMsg("hello");
});

template<class T> T& context();

con->context<std::string>() = "user defined data";

<h2 id="http-server">HttpServer</h2>
```c
//example
HttpServer sample(&base);
int r = sample.bind("", 8081);
exitif(r, "bind failed %d %s", errno, strerror(errno));
sample.onGet("/hello", [](const HttpConnPtr& con) {
   HttpResponse resp;
   resp.body = Slice("hello world");
   con.sendResponse(resp);
});

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