include/photon/common/event-loop.h

/*
Copyright 2022 The Photon Authors

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

#pragma once
#include <photon/common/callback.h>
#include <photon/common/object.h>

namespace photon {
struct thread;
};

class EventLoop : public Object {
public:
    const static int STOP = 0;
    const static int RUNNING = 1;
    const static int WAITING = 2;
    const static int STOPPING = -1;

    // return value > 0 indicates there is (are) event(s)
    // return value = 0 indicates there is still no event
    // return value < 0 indicates interrupted, will then exit the loop
    using Wait4Events = Callback<EventLoop*>;

    // return value is ignored
    using OnEvents = Callback<EventLoop*>;

    // run event loop and block current photon-thread, till the loop stopped
    virtual void run() = 0;
    // run event loop in new photon thread, so that will not block thread
    virtual void async_run() = 0;
    virtual void stop() = 0;

    int state() { return m_state; }

    photon::thread* loop_thread() { return m_thread; }

protected:
    EventLoop() {}  // not allowed to directly construct
    photon::thread* m_thread = nullptr;
    int m_state = STOP;
};

extern "C" EventLoop* new_event_loop(EventLoop::Wait4Events wait,
                                     EventLoop::OnEvents on_event);