SRS中使用协程库state-thread(ST), 在使用时对其进行了封装，保证使用方便。这种封装方法和使用thread库比较类似。

SrsEndlessThread

用于创建一个永不退出的协程，生命周期和整个程序一样。使用时需要继承ISrsEndlessThreadHandler方法，并在构造函数中创建SrsEndlessThread,重写cycle方法。

使用时执行流程：

 //永不退出协程的处理类
class ISrsEndlessThreadHandler
{
public:
    ISrsEndlessThreadHandler();
    virtual ~ISrsEndlessThreadHandler();
public:
    virtual int cycle() = 0;
public:
    virtual void on_thread_start();
    virtual int on_before_cycle();
    virtual int on_end_cycle();
    virtual void on_thread_stop();
};

//永不退出的协程
class SrsEndlessThread : public internal::ISrsThreadHandler
{
private:
    internal::SrsThread* pthread; //包含一个协程封装类
    ISrsEndlessThreadHandler* handler; //协程处理类
public:
    SrsEndlessThread(const char* n, ISrsEndlessThreadHandler* h);
    virtual ~SrsEndlessThread();
public:
    virtual int start(); //启动
public:
    virtual int cycle(); //执行的循环
    virtual void on_thread_start();
    virtual int on_before_cycle();
    virtual int on_end_cycle();
    virtual void on_thread_stop();
};

SrsOneCycleThread

用于创建一次循环的thread,在cycle函数执行完后，调用stop_loop退出。执行流程和SrsEndlessThread类似。

//执行完handler->cycle()后，调用stop_loop，退出
int SrsOneCycleThread::cycle()
{
    int ret = handler->cycle();
    pthread->stop_loop();
    return ret;
}

SrsReusableThread

可以重复使用的thread, 其他类继承ISrsReusableThreadHandler，并包含SrsReusableThread的变量，start函数启动线程，stop函数停止线程。重写cycle函数

class ISrsReusableThreadHandler
{
public:
    ISrsReusableThreadHandler();
    virtual ~ISrsReusableThreadHandler();
public:
    virtual int cycle() = 0;
public:
    virtual void on_thread_start();
    virtual int on_before_cycle();
    virtual int on_end_cycle();
    virtual void on_thread_stop();
};
class SrsReusableThread : public internal::ISrsThreadHandler
{
private:
    internal::SrsThread* pthread;
    ISrsReusableThreadHandler* handler;
public:
    SrsReusableThread(const char* n, ISrsReusableThreadHandler* h, int64_t interval_us = 0);
    virtual ~SrsReusableThread();
public:
    virtual int start();
    virtual void stop();
public:
    virtual int cid();
// interface internal::ISrsThreadHandler
public:
    virtual int cycle();
    virtual void on_thread_start();
    virtual int on_before_cycle();
    virtual int on_end_cycle();
    virtual void on_thread_stop();
};

//可以调用stop
void SrsReusableThread::stop()
{
    pthread->stop();
}

SrsReusableThread2

和SrsReusableThread区别是：在线程cycle里有内部循环，需要判断interrupt状态，如果内部loop想要退出线程，应该interrupt该线程。

//多了interrupt
void SrsReusableThread2::interrupt()
{
    pthread->stop_loop();
}

bool SrsReusableThread2::interrupted()
{
    return !pthread->can_loop();
}

SrsThread

/*
 * 线程处理类，定制线程启动的回调函数
 * */
class ISrsThreadHandler
{
public:
    ISrsThreadHandler();
    virtual ~ISrsThreadHandler();
public:
    virtual void on_thread_start(); //线程启动
    virtual int on_before_cycle(); //cycle前
    virtual int cycle() = 0; //cycle
    virtual int on_end_cycle(); //cycle后
    virtual void on_thread_stop(); //stop时
};
 /*
  * 协程的封装，作为内部使用的类
  * */
class SrsThread
{
private:
    st_thread_t tid; //tid
    int _cid; //cid
    bool loop; //是否支持loop
    bool can_run; //是否能run
    bool really_terminated; //是否terminate
    bool _joinable; //是否joinable
    const char* _name; //协程名字
    bool disposed; //是否dispose
private:
    ISrsThreadHandler* handler; //回调处理
    int64_t cycle_interval_us; //循环时间us
public:
     //初始化协程
    SrsThread(const char* name, ISrsThreadHandler* thread_handler, int64_t interval_us, bool joinable);
    virtual ~SrsThread();
public:
    virtual int cid(); //获取cid
    virtual int start(); //启动线程
    virtual void stop(); //暂停线程
public:
    virtual bool can_loop(); //是否能loop
    virtual void stop_loop(); //停止loop
private:
    virtual void dispose(); //释放
    virtual void thread_cycle(); //线程循环
    static void* thread_fun(void* arg); //线程循环调用的函数
};

/*
     * 线程的构造函数
     * name：函数名
     * thread_handle：线程处理函数
     * interval_us: 休眠时长
     * joinalbe: 是否能join
     * */
    SrsThread::SrsThread(const char* name, ISrsThreadHandler* thread_handler, int64_t interval_us, bool joinable)
    {
        _name = name;
        handler = thread_handler;
        cycle_interval_us = interval_us;
        
        tid = NULL;
        loop = false;
        really_terminated = true;
        _cid = -1;
        _joinable = joinable;
        disposed = false;
        can_run = false;
    }
    //析构函数，调用stop
    SrsThread::~SrsThread()
    {
        stop();
    }
    
    int SrsThread::cid()
    {
        return _cid;
    }
    //启动一个协程
    int SrsThread::start()
    {
        int ret = ERROR_SUCCESS;
        
        if(tid) {
            srs_info("thread %s already running.", _name);
            return ret;
        }
        //创建协程，调用thread_fun
        if((tid = st_thread_create(thread_fun, this, (_joinable? 1:0), 0)) == NULL){
            ret = ERROR_ST_CREATE_CYCLE_THREAD;
            srs_error("st_thread_create failed. ret=%d", ret);
            return ret;
        }
        //是否dispose
        disposed = false;
        // we set to loop to true for thread to run.
        loop = true;
        
        // wait for cid to ready, for parent thread to get the cid.
        while (_cid < 0) {
            st_usleep(10 * 1000);
        }
        
        // now, cycle thread can run.
        can_run = true;
        
        return ret;
    }

    //停止一个协程
    void SrsThread::stop()
    {
        if (!tid) {
            return;
        }
        
        loop = false; //loop为false, 那么不会继续执行cycle()
        
        dispose(); //释放协程
        
        _cid = -1;
        can_run = false;
        tid = NULL;        
    }

    //清理
    void SrsThread::dispose()
    {
        if (disposed) {
            return;
        }
        st_thread_interrupt(tid);
        if (_joinable) {
            // wait the thread to exit.
            int ret = st_thread_join(tid, NULL);
            if (ret) {
                srs_warn("core: ignore join thread failed.");
            }
        }
        while (!really_terminated) {
            st_usleep(10 * 1000);
            
            if (really_terminated) {
                break;
            }
            srs_warn("core: wait thread to actually terminated");
        }
        
        disposed = true;
    }

    //协程的循环
    void SrsThread::thread_cycle()
    {
        int ret = ERROR_SUCCESS;
        
        _srs_context->generate_id(); //生成cid
        srs_info("thread %s cycle start", _name);
        
        _cid = _srs_context->get_id();
        
        srs_assert(handler);
        handler->on_thread_start(); //调用handle的on_thread_start
        
        // thread is running now.
        really_terminated = false;
        
        // wait for cid to ready, for parent thread to get the cid.
        while (!can_run && loop) {
            st_usleep(10 * 1000);
        }
        //正在的loop，loop里执行函数为：on_before_cycle->cycle->on_end_cycle
        while (loop) {
            if ((ret = handler->on_before_cycle()) != ERROR_SUCCESS) {
                srs_warn("thread %s on before cycle failed, ignored and retry, ret=%d", _name, ret);
                goto failed;
            }
            srs_info("thread %s on before cycle success", _name);
            
            if ((ret = handler->cycle()) != ERROR_SUCCESS) {
                if (!srs_is_client_gracefully_close(ret) && !srs_is_system_control_error(ret)) {
                    srs_warn("thread %s cycle failed, ignored and retry, ret=%d", _name, ret);
                }
                goto failed;
            }
            srs_info("thread %s cycle success", _name);
            
            if ((ret = handler->on_end_cycle()) != ERROR_SUCCESS) {
                srs_warn("thread %s on end cycle failed, ignored and retry, ret=%d", _name, ret);
                goto failed;
            }
            srs_info("thread %s on end cycle success", _name);
            
        failed:
            if (!loop) {
                break;
            }
            if (cycle_interval_us != 0) {
                st_usleep(cycle_interval_us);
            }
        }
        
        // really terminated now.
        really_terminated = true;
        
        handler->on_thread_stop();//停止时的回调
        srs_info("thread %s cycle finished", _name);
    }

    //协程执行的函数
    void* SrsThread::thread_fun(void* arg)
    {
        SrsThread* obj = (SrsThread*)arg;
        srs_assert(obj);
        
        obj->thread_cycle(); //调用cycle函数
        
        // for valgrind to detect.
        SrsThreadContext* ctx = dynamic_cast<SrsThreadContext*>(_srs_context);
        if (ctx) {
            ctx->clear_cid();
        }
        
        st_thread_exit(NULL); //退出协程
        
        return NULL;
    }