squid源码分析1 ----EventLoop
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// squid 的核心循环class EventLoop{public: EventLoop(); // 注册引擎，这类引擎在每次循环中都被调用 void registerEngine(AsyncEngine *engine); // 主要运行函数 void run(); bool runOnce(); void setPrimaryEngine(AsyncEngine * engine); void setTimeService(TimeEngine *engine); // 定时器？ void stop(); // 停止 int errcount; // 出错次数private: // 设置运行状态字 void prepareToRun(); void checkEngine（AsyncEngine *engine, bool const primary); // 检测引擎 bool dispatchCalls();// 分发处理事件？ bool last_loop; typedef Vector<AsyncEngine *> engine_vector; engine_vector engines; // 循环调用事件 TimeEngine * timeService; // 时间触发事件 AsyncEngine *primaryEngine; // 当前的 int loop_delay; bool error; bool runOnceResult;}// 上次循环为假，初始化时EventLoop::EventLoop()：errcount(0),last_loop(false),timeService(NULL), primaryEngine(NULL){}void EventLoop::checkEngine(AsyncEngine *engine, bool const primary){ int requested_dalay; if (!primary) // primary 为假 requested_dalay = engine->checkEvent(0); // 为假就使用引擎指定? else requested_delay = engine->checkEvent(loop_delay); // loop delay 在运行时可能被指定为1秒== 1000毫秒 if (requested_delay < 0 ) // 小于0 ，就是超时了？ { switch(requested_delay){ case AsyncEngine::EVENT_IDLE: // 引擎空闲？ debugs(1,9,"Engine" << engine << "is idle"); break; case AsyncEngine::EVENT_ERROR: runOnceResult = false; error = true; // 循环里出现错误 break; default: fatal_dump("unknow AsynEngine result"); // 认为出现严重错误退出 } } else { runOnceResult = false; if (requested_delay < loop_delay) loop_delay = requested_delay; }} // 这么简单，仅仅是两个状态变量赋初值，看处理完后状态有变否void EventLoop::prepareToRun(){last_loop = false; errcount = 0;}void EventLoop::Run(){ prepareToRun();// runOnce出错时就跳出循环 非 0 返回值就出， 0 就继续循环// 如果链表中有fire被掉用，返回false，则继续循环while(!runOnce()); }bool EventLoop::runOnce(){bool sawActivity = false;runOnceResult = true;error = true;loop_delay = EVENT_LOOP_TIMEOUT; // wait 赋值 AsyncEngine *waitingEngine = primaryEngine;if (!waitingEngine && !engines.empty()) // 当前无和同步不为空waitingEngine = engines.back();// 返回最后一个元素 // 依次调用AsyncCall的链表的firedo {typedef engine_vector::iterator EVI;foe (EVI i = engines.begin(); i != engines.end(); ++i) // 剩下的都要check一次{if (*i != waitingEngine)checkEngine(*i,false);}sawActivity = dispatchCalls();// 至少链表中有一次fire，sawActivity就为TRUEif (sawActivity)runOnceResult = false;}while(sawActivity);if (waitingEngine != NULL){checkEngine(waitingEngine, true); // 此处就是weiting的check了}if (timeService != NULL)timeService->tick();sawActivity = disptchCalls(); // 实际是fire的返回结果if (sawActivity)runOnceResult =false;if (error){++errcount;debugs();}else{errcount = 0;}if (errcount == 10)return true;if (last_loop)return true;return runOnceResult;}bool EventLoop::disptchCalls(){bool dispatchedSome = AsyncCallQueue::Instance().fire();return dispatchedSome;}// 于传入的相等的就是当前的void EventLoop::setPrimaryEngine(AsyncEngine *engine){for (engine_vector::iterator i = engines.begin();i != engines.end(); ++i){if (*i == engine){primaryEngine = engine;}}}void EventLoop::setTimeService(TimeEngine *engine){timeService = engine;}void EventLoop::stop(){last_loop = true;}
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