iOS進階-Runloop源碼探究
開頭
這是一篇探究runloop內部原理實現的文章，不涉及具體使用。windows
內部實現
下面部分會以CFRunLoop說明，由於NSRunloop只是對CFRunLoop的封裝bash
do-while 循環
源碼
void CFRunLoopRun(void) { /* DOES CALLOUT */
int32_t result;
do {
result = CFRunLoopRunSpecific(CFRunLoopGetCurrent(), kCFRunLoopDefaultMode, 1.0e10, false);
CHECK_FOR_FORK();
} while (kCFRunLoopRunStopped != result && kCFRunLoopRunFinished != result);
}
複製代碼
結論
能夠看到，runloop在run起來後實際上是用一個do-while循環實現的，不一樣的是，runloop能夠作到不須要處理事務的時候就sleep，須要的時候就work。其做用總結就是：markdown
- 保持程序的持續運行
- 處理App中各類事件(觸摸、定時器、performSelector)
- 節省CPU資源、提供程序的性能：該作事作事，該休息休息
與線程的關係
源碼
##### mainRunloop CFRunLoopRef mainRunloop = CFRunLoopGetMain(); ##### CFRunLoopGetMain()函數內部實現 CFRunLoopRef CFRunLoopGetMain(void) { CHECK_FOR_FORK(); static CFRunLoopRef __main = NULL; // no retain needed //能夠看到傳了一個主線程參數進入 if (!__main) __main = _CFRunLoopGet0(pthread_main_thread_np()); // no CAS needed return __main; } ##### _CFRunLoopGet0()函數內部實現 CF_EXPORT CFRunLoopRef _CFRunLoopGet0(pthread_t t) { if (pthread_equal(t, kNilPthreadT)) { t = pthread_main_thread_np(); } __CFSpinLock(&loopsLock); if (!__CFRunLoops) { __CFSpinUnlock(&loopsLock); //創建全局的字典用來存儲 線程和runloop的關係 CFMutableDictionaryRef dict = CFDictionaryCreateMutable(kCFAllocatorSystemDefault, 0, NULL, &kCFTypeDictionaryValueCallBacks); //經過__CFRunLoopCreate()函數建立runloop實例對象 CFRunLoopRef mainLoop = __CFRunLoopCreate(pthread_main_thread_np()); //將mainLoop 和 mainThreadb存入字典 CFDictionarySetValue(dict, pthreadPointer(pthread_main_thread_np()), mainLoop); if (!OSAtomicCompareAndSwapPtrBarrier(NULL, dict, (void * volatile *)&__CFRunLoops)) { CFRelease(dict); } CFRelease(mainLoop); __CFSpinLock(&loopsLock); } //主線程的loop在上面就已經建立了，因此若是獲取不到，那確定是子線程的loop CFRunLoopRef loop = (CFRunLoopRef)CFDictionaryGetValue(__CFRunLoops, pthreadPointer(t)); __CFSpinUnlock(&loopsLock); //沒有loop，那就建立子線程的loop對象 if (!loop) { CFRunLoopRef newLoop = __CFRunLoopCreate(t); __CFSpinLock(&loopsLock); loop = (CFRunLoopRef)CFDictionaryGetValue(__CFRunLoops, pthreadPointer(t)); if (!loop) { //子線程和其runloop也會被存在這個全局的字典中 CFDictionarySetValue(__CFRunLoops, pthreadPointer(t), newLoop); loop = newLoop; } // don't release run loops inside the loopsLock, because CFRunLoopDeallocate may end up taking it __CFSpinUnlock(&loopsLock); CFRelease(newLoop); } if (pthread_equal(t, pthread_self())) { _CFSetTSD(__CFTSDKeyRunLoop, (void *)loop, NULL); if (0 == _CFGetTSD(__CFTSDKeyRunLoopCntr)) { _CFSetTSD(__CFTSDKeyRunLoopCntr, (void *)(PTHREAD_DESTRUCTOR_ITERATIONS-1), (void (*)(void *))__CFFinalizeRunLoop); } } //返回runloop return loop; } 複製代碼
結論
- 系統會建立一個全局的可變字典
CFMutableDictionaryRef dict，儲存線程和runloop； - 主線程的runloop是默認建立的
- 子線程的runloop默認不啓動，須要主動獲取
內部的mode-item關係
源碼
#### __CFRunLoop對象內部結構 struct __CFRunLoop { CFRuntimeBase _base; pthread_mutex_t _lock; /* locked for accessing mode list */ __CFPort _wakeUpPort; // used for CFRunLoopWakeUp Boolean _unused; volatile _per_run_data *_perRunData; // reset for runs of the run loop //關聯的線程 pthread_t _pthread; uint32_t _winthread; //有好多的Modes、Items CFMutableSetRef _commonModes; CFMutableSetRef _commonModeItems; //可是隻有一個currentMode CFRunLoopModeRef _currentMode; CFMutableSetRef _modes; struct _block_item *_blocks_head; struct _block_item *_blocks_tail; CFTypeRef _counterpart; }; struct __CFRunLoopMode { CFRuntimeBase _base; pthread_mutex_t _lock; /* must have the run loop locked before locking this */ CFStringRef _name; Boolean _stopped; char _padding[3]; //有好多的事件源 _sources0、_sources一、_observers、_timers CFMutableSetRef _sources0; CFMutableSetRef _sources1; CFMutableArrayRef _observers; CFMutableArrayRef _timers; CFMutableDictionaryRef _portToV1SourceMap; __CFPortSet _portSet; CFIndex _observerMask; #if USE_DISPATCH_SOURCE_FOR_TIMERS dispatch_source_t _timerSource; dispatch_queue_t _queue; Boolean _timerFired; // set to true by the source when a timer has fired Boolean _dispatchTimerArmed; #endif #if USE_MK_TIMER_TOO mach_port_t _timerPort; Boolean _mkTimerArmed; #endif #if DEPLOYMENT_TARGET_WINDOWS DWORD _msgQMask; void (*_msgPump)(void); #endif uint64_t _timerSoftDeadline; /* TSR */ uint64_t _timerHardDeadline; /* TSR */ }; 複製代碼
結論
__CFRunLoop對象內部包含多個modes- 而每一個
mode中又包含了多個items items就是事件源_sources0、_sources一、_observers、_timers...- 可是
__CFRunLoop對象同時只能持有一種mode：_currentMode
runloop對象結構圖
Runloop的item
runloop有六大事務item，這些item都是由runloop調用的。先看代碼app
- (void)timerItem{
//__CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__
[NSTimer scheduledTimerWithTimeInterval:1 repeats:YES block:^(NSTimer * _Nonnull timer) {
NSLog(@"test timer");
}];
}
複製代碼
等程序運行起來在斷點看內存堆棧調用less
(lldb) bt * thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 1.2 * frame #0: 0x000000010b59a240 01-Runloop初探`__28-[ViewController sourceDemo]_block_invoke(.block_descriptor=0x0000600000658318, timer=0x0000600000f58010) at ViewController.m:26 frame #1: 0x000000010b987413 Foundation`__NSFireTimer + 72 frame #2: 0x000000010bfb3b94 CoreFoundation`__CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ + 20 frame #3: 0x000000010bfb3882 CoreFoundation`__CFRunLoopDoTimer + 1026 frame #4: 0x000000010bfb2eda CoreFoundation`__CFRunLoopDoTimers + 266 frame #5: 0x000000010bfadc4e CoreFoundation`__CFRunLoopRun + 2238 frame #6: 0x000000010bfad066 CoreFoundation`CFRunLoopRunSpecific + 438 frame #7: 0x00000001154c6bb0 GraphicsServices`GSEventRunModal + 65 frame #8: 0x000000010f2e0d4d UIKitCore`UIApplicationMain + 1621 frame #9: 0x000000010b59a471 01-Runloop初探`main(argc=1, argv=0x00007ffee4664cf0) at main.m:21:16 frame #10: 0x000000010d90fc25 libdyld.dylib`start + 1 複製代碼
能夠看到在調用timer回調以前，調用了函數__CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__，咱們再去看源碼ide
static void __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__(CFRunLoopTimerCallBack func, CFRunLoopTimerRef timer, void *info) {
if (func) {
func(timer, info);
}
asm __volatile__(""); // thwart tail-call optimization
}
複製代碼
能夠看到確實是先調用__CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__,再調用timer回調函數func(timer,info)。這裏只是timer-item這一種，下面是iOS中全部的item調用狀況：函數
- block:
__CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK__ - timer:
__CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ - 響應source0:
__CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__觸摸事件 - 響應source1:
__CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__系統端口事件 - GCD主隊列:
__CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ - observer源:
__CFNOTIFICATIONCENTER_IS_CALLING_OUT_TO_AN_OBSERVER__
事務是如何被調用的
仍是以timer 調用爲例子說明oop
NSTimer *timer = [NSTimer timerWithTimeInterval:1 repeats:YES block:^(NSTimer * _Nonnull timer) {
NSLog(@"fire in home -- %@",[[NSRunLoop currentRunLoop] currentMode]);
}];
[[NSRunLoop currentRunLoop] addTimer:timer forMode:NSRunLoopCommonModes];
複製代碼
存item
先看- (void)addTimer:(NSTimer *)timer forMode:(NSRunLoopMode)mode內部作了什麼性能
static void __CFRunLoopAddItemsToCommonMode(const void *value, void *ctx) {
CFTypeRef item = (CFTypeRef)value;
CFRunLoopRef rl = (CFRunLoopRef)(((CFTypeRef *)ctx)[0]);
CFStringRef modeName = (CFStringRef)(((CFTypeRef *)ctx)[1]);
if (CFGetTypeID(item) == CFRunLoopSourceGetTypeID()) {
CFRunLoopAddSource(rl, (CFRunLoopSourceRef)item, modeName);
} else if (CFGetTypeID(item) == CFRunLoopObserverGetTypeID()) {
CFRunLoopAddObserver(rl, (CFRunLoopObserverRef)item, modeName);
} else if (CFGetTypeID(item) == CFRunLoopTimerGetTypeID()) {
CFRunLoopAddTimer(rl, (CFRunLoopTimerRef)item, modeName);
}
}
#### CFRunLoopAddTimer()
void CFRunLoopAddTimer(CFRunLoopRef rl, CFRunLoopTimerRef rlt, CFStringRef modeName) {
CHECK_FOR_FORK();
if (__CFRunLoopIsDeallocating(rl)) return;
if (!__CFIsValid(rlt) || (NULL != rlt->_runLoop && rlt->_runLoop != rl)) return;
__CFRunLoopLock(rl);
//判斷當前loop的mode類型
if (modeName == kCFRunLoopCommonModes) {
CFSetRef set = rl->_commonModes ? CFSetCreateCopy(kCFAllocatorSystemDefault, rl->_commonModes) : NULL;
if (NULL == rl->_commonModeItems) {
rl->_commonModeItems = CFSetCreateMutable(kCFAllocatorSystemDefault, 0, &kCFTypeSetCallBacks);
}
//將timers添加到當前rl->_commonModeItems中
CFSetAddValue(rl->_commonModeItems, rlt);
//判斷set是否存在
if (NULL != set) {
CFTypeRef context[2] = {rl, rlt};
/* add new item to all common-modes */
//將這個timer 提交到當前loop的上下文中，方便後面使用去取
CFSetApplyFunction(set, (__CFRunLoopAddItemToCommonModes), (void *)context);
CFRelease(set);
}
} else {//其餘類型也差很少，這裏就再也不細說
CFRunLoopModeRef rlm = __CFRunLoopFindMode(rl, modeName, true);
if (NULL != rlm) {
if (NULL == rlm->_timers) {
CFArrayCallBacks cb = kCFTypeArrayCallBacks;
cb.equal = NULL;
rlm->_timers = CFArrayCreateMutable(kCFAllocatorSystemDefault, 0, &cb);
}
}
if (NULL != rlm && !CFSetContainsValue(rlt->_rlModes, rlm->_name)) {
__CFRunLoopTimerLock(rlt);
if (NULL == rlt->_runLoop) {
rlt->_runLoop = rl;
} else if (rl != rlt->_runLoop) {
__CFRunLoopTimerUnlock(rlt);
__CFRunLoopModeUnlock(rlm);
__CFRunLoopUnlock(rl);
return;
}
CFSetAddValue(rlt->_rlModes, rlm->_name);
__CFRunLoopTimerUnlock(rlt);
__CFRunLoopTimerFireTSRLock();
__CFRepositionTimerInMode(rlm, rlt, false);
__CFRunLoopTimerFireTSRUnlock();
if (!_CFExecutableLinkedOnOrAfter(CFSystemVersionLion)) {
if (rl != CFRunLoopGetCurrent()) CFRunLoopWakeUp(rl);
}
}
if (NULL != rlm) {
__CFRunLoopModeUnlock(rlm);
}
}
__CFRunLoopUnlock(rl);
}
複製代碼
有上面的源碼可知- (void)addTimer:(NSTimer *)timer forMode:(NSRunLoopMode)mode內部就是將timer提交到當前runlopp對象的modes中的items中，注意是全部modes中的items中;ui
取item
等程序運行起來在斷點看內存堆棧調用
(lldb) bt * thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 1.2 * frame #0: 0x000000010b59a240 01-Runloop初探`__28-[ViewController sourceDemo]_block_invoke(.block_descriptor=0x0000600000658318, timer=0x0000600000f58010) at ViewController.m:26 frame #1: 0x000000010b987413 Foundation`__NSFireTimer + 72 frame #2: 0x000000010bfb3b94 CoreFoundation`__CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ + 20 frame #3: 0x000000010bfb3882 CoreFoundation`__CFRunLoopDoTimer + 1026 frame #4: 0x000000010bfb2eda CoreFoundation`__CFRunLoopDoTimers + 266 frame #5: 0x000000010bfadc4e CoreFoundation`__CFRunLoopRun + 2238 frame #6: 0x000000010bfad066 CoreFoundation`CFRunLoopRunSpecific + 438 frame #7: 0x00000001154c6bb0 GraphicsServices`GSEventRunModal + 65 frame #8: 0x000000010f2e0d4d UIKitCore`UIApplicationMain + 1621 frame #9: 0x000000010b59a471 01-Runloop初探`main(argc=1, argv=0x00007ffee4664cf0) at main.m:21:16 frame #10: 0x000000010d90fc25 libdyld.dylib`start + 1 複製代碼
能夠看到在調用__CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__以前調用了__CFRunLoopDoTimer、__CFRunLoopDoTimers、__CFRunLoopRun這三個方法，那就去源碼查下看看
##### __CFRunLoopRun() 源碼太長，只展現部分 static int32_t __CFRunLoopRun__CFRunLoopRun(CFRunLoopRef rl, CFRunLoopModeRef rlm, CFTimeInterval seconds, Boolean stopAfterHandle, CFRunLoopModeRef previousMode) { uint64_t startTSR = mach_absolute_time(); if (__CFRunLoopIsStopped(rl)) { __CFRunLoopUnsetStopped(rl); return kCFRunLoopRunStopped; } else if (rlm->_stopped) { rlm->_stopped = false; return kCFRunLoopRunStopped; } ... //調用__CFRunLoopDoTimers() if (!__CFRunLoopDoTimers(rl, rlm, mach_absolute_time())) { // Re-arm the next timer, because we apparently fired early __CFArmNextTimerInMode(rlm, rl); } ... } ##### __CFRunLoopDoTimers() static Boolean __CFRunLoopDoTimers(CFRunLoopRef rl, CFRunLoopModeRef rlm, uint64_t limitTSR) { /* DOES CALLOUT */ Boolean timerHandled = false; CFMutableArrayRef timers = NULL; //遍歷當前runloop中modes中的times加到CFMutableArrayRef timers對象中 for (CFIndex idx = 0, cnt = rlm->_timers ? CFArrayGetCount(rlm->_timers) : 0; idx < cnt; idx++) { CFRunLoopTimerRef rlt = (CFRunLoopTimerRef)CFArrayGetValueAtIndex(rlm->_timers, idx); if (__CFIsValid(rlt) && !__CFRunLoopTimerIsFiring(rlt)) { if (rlt->_fireTSR <= limitTSR) { if (!timers) timers = CFArrayCreateMutable(kCFAllocatorSystemDefault, 0, &kCFTypeArrayCallBacks); CFArrayAppendValue(timers, rlt); } } } //遍歷上面的CFMutableArrayRef timers，拿到具體每一個timer for (CFIndex idx = 0, cnt = timers ? CFArrayGetCount(timers) : 0; idx < cnt; idx++) { CFRunLoopTimerRef rlt = (CFRunLoopTimerRef)CFArrayGetValueAtIndex(timers, idx); //調用timer Boolean did = __CFRunLoopDoTimer(rl, rlm, rlt); timerHandled = timerHandled || did; } if (timers) CFRelease(timers); return timerHandled; } ##### __CFRunLoopDoTimer() 部分源碼 static Boolean __CFRunLoopDoTimer(CFRunLoopRef rl, CFRunLoopModeRef rlm, CFRunLoopTimerRef rlt) { /* DOES CALLOUT */ Boolean timerHandled = false; uint64_t oldFireTSR = 0; /* Fire a timer */ CFRetain(rlt); __CFRunLoopTimerLock(rlt); //判斷是否還在超時時間內 if (__CFIsValid(rlt) && rlt->_fireTSR <= mach_absolute_time() && !__CFRunLoopTimerIsFiring(rlt) && rlt->_runLoop == rl) { ... //最終調用`__CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__` __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__(rlt->_callout, rlt, context_info); ... } ... } 複製代碼
因此取(調用)的過程是：
當runloop對象在run時候，會去獲取當前loop->currrentMode->timers,若是內部有timer那就遍歷調用。擴展到其餘的item也同樣(事件源_sources0、_sources一、_observers、_timers...)，也是先提交到後遍歷調用。
注意這裏currrentMode是一種也能夠是多種好比commandModes就是多種mode的集合；
這個時候再看這張經典圖是否是以爲很形象
runloop如何工做的
源代碼詳細版
仍是得看__CFRunLoopRun()方法源碼，可是此次沒法省略了，源碼有詳細註釋就再也不贅述
static int32_t __CFRunLoopRun(CFRunLoopRef rl, CFRunLoopModeRef rlm, CFTimeInterval seconds, Boolean stopAfterHandle, CFRunLoopModeRef previousMode) {
//獲取系統啓動後的CPU運行時間，用於控制超時時間
uint64_t startTSR = mach_absolute_time();
// 判斷當前runloop的狀態是否關閉
if (__CFRunLoopIsStopped(rl)) {
__CFRunLoopUnsetStopped(rl);
return kCFRunLoopRunStopped;
} else if (rlm->_stopped) {
rlm->_stopped = false;
return kCFRunLoopRunStopped;
}
//mach端口，在內核中，消息在端口之間傳遞。 初始爲0
mach_port_name_t dispatchPort = MACH_PORT_NULL;
//判斷是否爲主線程
Boolean libdispatchQSafe = pthread_main_np() && ((HANDLE_DISPATCH_ON_BASE_INVOCATION_ONLY && NULL == previousMode) || (!HANDLE_DISPATCH_ON_BASE_INVOCATION_ONLY && 0 == _CFGetTSD(__CFTSDKeyIsInGCDMainQ)));
//若是在主線程 && runloop是主線程的runloop && 該mode是commonMode，則給mach端口賦值爲主線程收發消息的端口
if (libdispatchQSafe && (CFRunLoopGetMain() == rl) && CFSetContainsValue(rl->_commonModes, rlm->_name)) dispatchPort = _dispatch_get_main_queue_port_4CF();
#if USE_DISPATCH_SOURCE_FOR_TIMERS
mach_port_name_t modeQueuePort = MACH_PORT_NULL;
if (rlm->_queue) {
//mode賦值爲dispatch端口_dispatch_runloop_root_queue_perform_4CF
modeQueuePort = _dispatch_runloop_root_queue_get_port_4CF(rlm->_queue);
if (!modeQueuePort) {
CRASH("Unable to get port for run loop mode queue (%d)", -1);
}
}
#endif
dispatch_source_t timeout_timer = NULL;
struct __timeout_context *timeout_context = (struct __timeout_context *)malloc(sizeof(*timeout_context));
if (seconds <= 0.0) { // instant timeout
seconds = 0.0;
timeout_context->termTSR = 0ULL;
// 1.0e10 == 1* 10^10
} else if (seconds <= TIMER_INTERVAL_LIMIT) {
//seconds爲超時時間，超時時執行__CFRunLoopTimeout函數
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, DISPATCH_QUEUE_OVERCOMMIT);
timeout_timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue);
dispatch_retain(timeout_timer);
timeout_context->ds = timeout_timer;
timeout_context->rl = (CFRunLoopRef)CFRetain(rl);
timeout_context->termTSR = startTSR + __CFTimeIntervalToTSR(seconds);
dispatch_set_context(timeout_timer, timeout_context); // source gets ownership of context
dispatch_source_set_event_handler_f(timeout_timer, __CFRunLoopTimeout);
dispatch_source_set_cancel_handler_f(timeout_timer, __CFRunLoopTimeoutCancel);
uint64_t ns_at = (uint64_t)((__CFTSRToTimeInterval(startTSR) + seconds) * 1000000000ULL);
dispatch_source_set_timer(timeout_timer, dispatch_time(1, ns_at), DISPATCH_TIME_FOREVER, 1000ULL);
dispatch_resume(timeout_timer);
} else { // infinite timeout
//永不超時 - 永動機
seconds = 9999999999.0;
timeout_context->termTSR = UINT64_MAX;
}
//標誌位默認爲true
Boolean didDispatchPortLastTime = true;
//記錄最後runloop狀態，用於return
int32_t retVal = 0;
// itmes
do {
//初始化一個存放內核消息的緩衝池
uint8_t msg_buffer[3 * 1024];
#if DEPLOYMENT_TARGET_MACOSX || DEPLOYMENT_TARGET_EMBEDDED || DEPLOYMENT_TARGET_EMBEDDED_MINI
mach_msg_header_t *msg = NULL;
mach_port_t livePort = MACH_PORT_NULL;
#elif DEPLOYMENT_TARGET_WINDOWS
HANDLE livePort = NULL;
Boolean windowsMessageReceived = false;
#endif
//取全部須要監聽的port
__CFPortSet waitSet = rlm->_portSet;
//設置RunLoop爲能夠被喚醒狀態
__CFRunLoopUnsetIgnoreWakeUps(rl);
/// 2. 通知 Observers: RunLoop 即將觸發 Timer 回調。
if (rlm->_observerMask & kCFRunLoopBeforeTimers) __CFRunLoopDoObservers(rl, rlm, kCFRunLoopBeforeTimers);
if (rlm->_observerMask & kCFRunLoopBeforeSources)
/// 3. 通知 Observers: RunLoop 即將觸發 Source0 (非port) 回調。
__CFRunLoopDoObservers(rl, rlm, kCFRunLoopBeforeSources);
/// 執行被加入的block
__CFRunLoopDoBlocks(rl, rlm);
/// 4. RunLoop 觸發 Source0 (非port) 回調。
Boolean sourceHandledThisLoop = __CFRunLoopDoSources0(rl, rlm, stopAfterHandle);
if (sourceHandledThisLoop) {
/// 執行被加入的block
__CFRunLoopDoBlocks(rl, rlm);
}
//若是沒有Sources0事件處理 而且 沒有超時，poll爲false
//若是有Sources0事件處理 或者 超時，poll都爲true
Boolean poll = sourceHandledThisLoop || (0ULL == timeout_context->termTSR);
//第一次do..whil循環不會走該分支，由於didDispatchPortLastTime初始化是true
if (MACH_PORT_NULL != dispatchPort && !didDispatchPortLastTime) {
#if DEPLOYMENT_TARGET_MACOSX || DEPLOYMENT_TARGET_EMBEDDED || DEPLOYMENT_TARGET_EMBEDDED_MINI
//從緩衝區讀取消息
msg = (mach_msg_header_t *)msg_buffer;
/// 5. 若是有 Source1 (基於port) 處於 ready 狀態，直接處理這個 Source1 而後跳轉去處理消息。
if (__CFRunLoopServiceMachPort(dispatchPort, &msg, sizeof(msg_buffer), &livePort, 0)) {
//若是接收到了消息的話，前往第9步開始處理msg
goto handle_msg;
}
#elif DEPLOYMENT_TARGET_WINDOWS
if (__CFRunLoopWaitForMultipleObjects(NULL, &dispatchPort, 0, 0, &livePort, NULL)) {
goto handle_msg;
}
#endif
}
didDispatchPortLastTime = false;
/// 6.通知 Observers: RunLoop 的線程即將進入休眠(sleep)。
if (!poll && (rlm->_observerMask & kCFRunLoopBeforeWaiting)) __CFRunLoopDoObservers(rl, rlm, kCFRunLoopBeforeWaiting);
//設置RunLoop爲休眠狀態
__CFRunLoopSetSleeping(rl);
// do not do any user callouts after this point (after notifying of sleeping)
// Must push the local-to-this-activation ports in on every loop
// iteration, as this mode could be run re-entrantly and we don't // want these ports to get serviced. __CFPortSetInsert(dispatchPort, waitSet); __CFRunLoopModeUnlock(rlm); __CFRunLoopUnlock(rl); #if DEPLOYMENT_TARGET_MACOSX || DEPLOYMENT_TARGET_EMBEDDED || DEPLOYMENT_TARGET_EMBEDDED_MINI #if USE_DISPATCH_SOURCE_FOR_TIMERS //這裏有個內循環，用於接收等待端口的消息 //進入此循環後，線程進入休眠，直到收到新消息才跳出該循環，繼續執行run loop do { if (kCFUseCollectableAllocator) { objc_clear_stack(0); memset(msg_buffer, 0, sizeof(msg_buffer)); } msg = (mach_msg_header_t *)msg_buffer; //7.接收waitSet端口的消息 __CFRunLoopServiceMachPort(waitSet, &msg, sizeof(msg_buffer), &livePort, poll ? 0 : TIMEOUT_INFINITY); //收到消息以後，livePort的值爲msg->msgh_local_port， if (modeQueuePort != MACH_PORT_NULL && livePort == modeQueuePort) { // Drain the internal queue. If one of the callout blocks sets the timerFired flag, break out and service the timer. while (_dispatch_runloop_root_queue_perform_4CF(rlm->_queue)); if (rlm->_timerFired) { // Leave livePort as the queue port, and service timers below rlm->_timerFired = false; break; } else { if (msg && msg != (mach_msg_header_t *)msg_buffer) free(msg); } } else { // Go ahead and leave the inner loop. break; } } while (1); #else if (kCFUseCollectableAllocator) { objc_clear_stack(0); memset(msg_buffer, 0, sizeof(msg_buffer)); } msg = (mach_msg_header_t *)msg_buffer; /// 7. 調用 mach_msg 等待接受 mach_port 的消息。線程將進入休眠, 直到被下面某一個事件喚醒。 /// • 一個基於 port 的Source 的事件。 /// • 一個 Timer 到時間了 /// • RunLoop 自身的超時時間到了 /// • 被其餘什麼調用者手動喚醒 // mach 事務 - 指令 __CFRunLoopServiceMachPort(waitSet, &msg, sizeof(msg_buffer), &livePort, poll ? 0 : TIMEOUT_INFINITY); #endif #elif DEPLOYMENT_TARGET_WINDOWS // Here, use the app-supplied message queue mask. They will set this if they are interested in having this run loop receive windows messages. __CFRunLoopWaitForMultipleObjects(waitSet, NULL, poll ? 0 : TIMEOUT_INFINITY, rlm->_msgQMask, &livePort, &windowsMessageReceived); #endif __CFRunLoopLock(rl); __CFRunLoopModeLock(rlm); // Must remove the local-to-this-activation ports in on every loop // iteration, as this mode could be run re-entrantly and we don't
// want these ports to get serviced. Also, we don't want them left // in there if this function returns. __CFPortSetRemove(dispatchPort, waitSet); __CFRunLoopSetIgnoreWakeUps(rl); // user callouts now OK again //取消runloop的休眠狀態 __CFRunLoopUnsetSleeping(rl); /// 8. 通知 Observers: RunLoop 的線程剛剛被喚醒了。 if (!poll && (rlm->_observerMask & kCFRunLoopAfterWaiting)) __CFRunLoopDoObservers(rl, rlm, kCFRunLoopAfterWaiting); /// 收到消息，處理消息。 handle_msg:; __CFRunLoopSetIgnoreWakeUps(rl); #if DEPLOYMENT_TARGET_WINDOWS if (windowsMessageReceived) { // These Win32 APIs cause a callout, so make sure we're unlocked first and relocked after
__CFRunLoopModeUnlock(rlm);
__CFRunLoopUnlock(rl);
if (rlm->_msgPump) {
rlm->_msgPump();
} else {
MSG msg;
if (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE | PM_NOYIELD)) {
TranslateMessage(&msg);
DispatchMessage(&msg);
}
}
__CFRunLoopLock(rl);
__CFRunLoopModeLock(rlm);
sourceHandledThisLoop = true;
// To prevent starvation of sources other than the message queue, we check again to see if any other sources need to be serviced
// Use 0 for the mask so windows messages are ignored this time. Also use 0 for the timeout, because we're just checking to see if the things are signalled right now -- we will wait on them again later. // NOTE: Ignore the dispatch source (it's not in the wait set anymore) and also don't run the observers here since we are polling. __CFRunLoopSetSleeping(rl); __CFRunLoopModeUnlock(rlm); __CFRunLoopUnlock(rl); __CFRunLoopWaitForMultipleObjects(waitSet, NULL, 0, 0, &livePort, NULL); __CFRunLoopLock(rl); __CFRunLoopModeLock(rlm); __CFRunLoopUnsetSleeping(rl); // If we have a new live port then it will be handled below as normal } #endif if (MACH_PORT_NULL == livePort) { CFRUNLOOP_WAKEUP_FOR_NOTHING(); // handle nothing } else if (livePort == rl->_wakeUpPort) { CFRUNLOOP_WAKEUP_FOR_WAKEUP(); // do nothing on Mac OS #if DEPLOYMENT_TARGET_WINDOWS // Always reset the wake up port, or risk spinning forever ResetEvent(rl->_wakeUpPort); #endif } #if USE_DISPATCH_SOURCE_FOR_TIMERS else if (modeQueuePort != MACH_PORT_NULL && livePort == modeQueuePort) { CFRUNLOOP_WAKEUP_FOR_TIMER(); /// 9.1 若是一個 Timer 到時間了，觸發這個Timer的回調。 if (!__CFRunLoopDoTimers(rl, rlm, mach_absolute_time())) { // Re-arm the next timer, because we apparently fired early __CFArmNextTimerInMode(rlm, rl); } } #endif #if USE_MK_TIMER_TOO else if (rlm->_timerPort != MACH_PORT_NULL && livePort == rlm->_timerPort) { CFRUNLOOP_WAKEUP_FOR_TIMER(); // On Windows, we have observed an issue where the timer port is set before the time which we requested it to be set. For example, we set the fire time to be TSR 167646765860, but it is actually observed firing at TSR 167646764145, which is 1715 ticks early. The result is that, when __CFRunLoopDoTimers checks to see if any of the run loop timers should be firing, it appears to be 'too early' for the next timer, and no timers are handled. // In this case, the timer port has been automatically reset (since it was returned from MsgWaitForMultipleObjectsEx), and if we do not re-arm it, then no timers will ever be serviced again unless something adjusts the timer list (e.g. adding or removing timers). The fix for the issue is to reset the timer here if CFRunLoopDoTimers did not handle a timer itself. 9308754 if (!__CFRunLoopDoTimers(rl, rlm, mach_absolute_time())) { // Re-arm the next timer __CFArmNextTimerInMode(rlm, rl); } } #endif /// 9.2 若是有dispatch到main_queue的block，執行block else if (livePort == dispatchPort) { CFRUNLOOP_WAKEUP_FOR_DISPATCH(); __CFRunLoopModeUnlock(rlm); __CFRunLoopUnlock(rl); _CFSetTSD(__CFTSDKeyIsInGCDMainQ, (void *)6, NULL); #if DEPLOYMENT_TARGET_WINDOWS void *msg = 0; #endif __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__(msg); _CFSetTSD(__CFTSDKeyIsInGCDMainQ, (void *)0, NULL); __CFRunLoopLock(rl); __CFRunLoopModeLock(rlm); sourceHandledThisLoop = true; didDispatchPortLastTime = true; } else { /// 9.3 若是一個 Source1 (基於port) 發出事件了，處理這個事件 CFRUNLOOP_WAKEUP_FOR_SOURCE(); // Despite the name, this works for windows handles as well CFRunLoopSourceRef rls = __CFRunLoopModeFindSourceForMachPort(rl, rlm, livePort); if (rls) { #if DEPLOYMENT_TARGET_MACOSX || DEPLOYMENT_TARGET_EMBEDDED || DEPLOYMENT_TARGET_EMBEDDED_MINI mach_msg_header_t *reply = NULL; sourceHandledThisLoop = __CFRunLoopDoSource1(rl, rlm, rls, msg, msg->msgh_size, &reply) || sourceHandledThisLoop; if (NULL != reply) { (void)mach_msg(reply, MACH_SEND_MSG, reply->msgh_size, 0, MACH_PORT_NULL, 0, MACH_PORT_NULL); CFAllocatorDeallocate(kCFAllocatorSystemDefault, reply); } #elif DEPLOYMENT_TARGET_WINDOWS sourceHandledThisLoop = __CFRunLoopDoSource1(rl, rlm, rls) || sourceHandledThisLoop; #endif } } #if DEPLOYMENT_TARGET_MACOSX || DEPLOYMENT_TARGET_EMBEDDED || DEPLOYMENT_TARGET_EMBEDDED_MINI if (msg && msg != (mach_msg_header_t *)msg_buffer) free(msg); #endif /// 執行加入到Loop的block __CFRunLoopDoBlocks(rl, rlm); if (sourceHandledThisLoop && stopAfterHandle) { /// 進入loop時參數說處理完事件就返回。 retVal = kCFRunLoopRunHandledSource; } else if (timeout_context->termTSR < mach_absolute_time()) { /// 超出傳入參數標記的超時時間了 retVal = kCFRunLoopRunTimedOut; } else if (__CFRunLoopIsStopped(rl)) { /// 被外部調用者強制中止了 __CFRunLoopUnsetStopped(rl); retVal = kCFRunLoopRunStopped; } else if (rlm->_stopped) { /// 自動中止了 rlm->_stopped = false; retVal = kCFRunLoopRunStopped; } else if (__CFRunLoopModeIsEmpty(rl, rlm, previousMode)) { /// source/timer/observer一個都沒有了 retVal = kCFRunLoopRunFinished; } /// 若是沒超時，mode裏沒空，loop也沒被中止，那繼續loop。 } while (0 == retVal); if (timeout_timer) { dispatch_source_cancel(timeout_timer); dispatch_release(timeout_timer); } else { free(timeout_context); } return retVal; } 複製代碼
僞代碼簡化版
SInt32 CFRunLoopRunSpecific(CFRunLoopRef rl, CFStringRef modeName, CFTimeInterval seconds, Boolean returnAfterSourceHandled) { /* DOES CALLOUT */ CHECK_FOR_FORK(); if (__CFRunLoopIsDeallocating(rl)) return kCFRunLoopRunFinished; __CFRunLoopLock(rl); /// 首先根據modeName找到對應mode CFRunLoopModeRef currentMode = __CFRunLoopFindMode(rl, modeName, false); /// 通知 Observers: RunLoop 即將進入 loop。 __CFRunLoopDoObservers(rl, currentMode, kCFRunLoopEntry); /// 內部函數，進入loop result = __CFRunLoopRun(rl, currentMode, seconds, returnAfterSourceHandled, previousMode); /// 通知 Observers: RunLoop 即將退出。 __CFRunLoopDoObservers(rl, currentMode, kCFRunLoopExit); return result; } /// 核心函數 static int32_t __CFRunLoopRun(CFRunLoopRef rl, CFRunLoopModeRef rlm, CFTimeInterval seconds, Boolean stopAfterHandle, CFRunLoopModeRef previousMode) { int32_t retVal = 0; do { /// 通知 Observers: 即將處理timer事件 __CFRunLoopDoObservers(rl, rlm, kCFRunLoopBeforeTimers); /// 通知 Observers: 即將處理Source事件 __CFRunLoopDoObservers(rl, rlm, kCFRunLoopBeforeSources) /// 處理Blocks __CFRunLoopDoBlocks(rl, rlm); /// 處理sources0 Boolean sourceHandledThisLoop = __CFRunLoopDoSources0(rl, rlm, stopAfterHandle); /// 處理sources0返回爲YES if (sourceHandledThisLoop) { /// 處理Blocks __CFRunLoopDoBlocks(rl, rlm); } /// 判斷有無故口消息(Source1) if (__CFRunLoopServiceMachPort(dispatchPort, &msg, sizeof(msg_buffer), &livePort, 0, &voucherState, NULL)) { /// 處理消息 goto handle_msg; } /// 通知 Observers: 即將進入休眠 __CFRunLoopDoObservers(rl, rlm, kCFRunLoopBeforeWaiting); __CFRunLoopSetSleeping(rl); /// 等待被喚醒 __CFRunLoopServiceMachPort(waitSet, &msg, sizeof(msg_buffer), &livePort, poll ? 0 : TIMEOUT_INFINITY, &voucherState, &voucherCopy); // user callouts now OK again __CFRunLoopUnsetSleeping(rl); /// 通知 Observers: 被喚醒，結束休眠 __CFRunLoopDoObservers(rl, rlm, kCFRunLoopAfterWaiting); handle_msg: if (被Timer喚醒) { /// 處理Timers __CFRunLoopDoTimers(rl, rlm, mach_absolute_time())； } else if (被GCD喚醒) { /// 處理gcd __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__(msg); } else if (被Source1喚醒) { /// 被Source1喚醒，處理Source1 __CFRunLoopDoSource1(rl, rlm, rls, msg, msg->msgh_size, &reply) } /// 處理block __CFRunLoopDoBlocks(rl, rlm); if (sourceHandledThisLoop && stopAfterHandle) { retVal = kCFRunLoopRunHandledSource; } else if (timeout_context->termTSR < mach_absolute_time()) { retVal = kCFRunLoopRunTimedOut; } else if (__CFRunLoopIsStopped(rl)) { __CFRunLoopUnsetStopped(rl); retVal = kCFRunLoopRunStopped; } else if (rlm->_stopped) { rlm->_stopped = false; retVal = kCFRunLoopRunStopped; } else if (__CFRunLoopModeIsEmpty(rl, rlm, previousMode)) { retVal = kCFRunLoopRunFinished; } } while (0 == retVal); return retVal; } // main dispatch queue __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ // __CFRunLoopDoObservers __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ // __CFRunLoopDoBlocks __CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK__ // __CFRunLoopDoSources0 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ // __CFRunLoopDoSource1 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ // __CFRunLoopDoTimers __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ 複製代碼
上面源碼總結就是這麼一張圖
寫在最後
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