關(guān)鍵數(shù)據(jù)結(jié)構(gòu)

typedef struct tagEvent {    UINT32 uwEventID;           LOS_DL_LIST stEventList; /**< Event control block linked list */  }EVENT_CB_S,*PEVENT_CB_S;

事件初始化

LITE_OS_SEC_TEXT_INIT UINT32 LOS_EventInit(PEVENT_CB_S eventCB){    if (eventCB == NULL) {        return LOS_ERRNO_EVENT_PTR_NULL;    }    eventCB->uwEventID = 0;    LOS_ListInit(&eventCB->stEventList);    OsHookCall(LOS_HOOK_TYPE_EVENT_INIT, eventCB);    return LOS_OK;}

PEVENT_CB_S 相當(dāng)于 EVENT_CB_S *， 因此 eventCB 是指針。

說明事件控制塊由任務(wù)自己創(chuàng)建，內(nèi)核事件模塊只負責(zé)維護。任務(wù)定義自己的事件控制塊變量，通過 LOS_EventInit 初始化，此時沒有事件發(fā)生，事件鏈表為空。

用圖來表達就是：

事件寫操作

LITE_OS_SEC_TEXT UINT32 LOS_EventWrite(PEVENT_CB_S eventCB, UINT32 events){    ...    eventCB->uwEventID |= events;                    ---1    if (!LOS_ListEmpty(&eventCB->stEventList)) {     ---2        for (resumedTask = LOS_DL_LIST_ENTRY((&eventCB->stEventList)->pstNext, LosTaskCB, pendList);             &resumedTask->pendList != (&eventCB->stEventList);) { -------3            nextTask = LOS_DL_LIST_ENTRY(resumedTask->pendList.pstNext, LosTaskCB, pendList);
            if (((resumedTask->eventMode & LOS_WAITMODE_OR) && (resumedTask->eventMask & events) != 0) ||                ((resumedTask->eventMode & LOS_WAITMODE_AND) &&                 ((resumedTask->eventMask & eventCB->uwEventID) == resumedTask->eventMask))) {                exitFlag = 1;
                OsSchedTaskWake(resumedTask);       ---4            }            resumedTask = nextTask;        }
        if (exitFlag == 1) {            LOS_IntRestore(intSave);            LOS_Schedule();                        ---5            return LOS_OK;        }    }    ...}

寫事件實際操作如下圖：

事件讀操作

下面是 LOS_EventPoll() 的實現(xiàn)：

LITE_OS_SEC_TEXT UINT32 LOS_EventPoll(UINT32 *eventID, UINT32 eventMask, UINT32 mode){    UINT32 ret = 0;    UINT32 intSave;
    if (eventID == NULL) {        return LOS_ERRNO_EVENT_PTR_NULL;    }    intSave = LOS_IntLock();    if (mode & LOS_WAITMODE_OR) {        if ((*eventID & eventMask) != 0) {      ---1            ret = *eventID & eventMask;        }    } else {        if ((eventMask != 0) && (eventMask == (*eventID & eventMask))) {   ---2            ret = *eventID & eventMask;        }    }    if (ret && (mode & LOS_WAITMODE_CLR)) {   ---3        *eventID = *eventID & ~(ret);    }    LOS_IntRestore(intSave);    return ret;}

可以看出以上實現(xiàn)了兩種事件的讀取方式：一種是多個事件只要一個發(fā)生就算發(fā)生，另一種是全部事件發(fā)生才算發(fā)生。

下面是 LOS_EventRead()：

LITE_OS_SEC_TEXT UINT32 LOS_EventRead(PEVENT_CB_S eventCB, UINT32 eventMask, UINT32 mode, UINT32 timeOut){    ...    ret = LOS_EventPoll(&(eventCB->uwEventID), eventMask, mode);           ---1    OsHookCall(LOS_HOOK_TYPE_EVENT_READ, eventCB, eventMask, mode, timeOut);    if (ret == 0) {        if (timeOut == 0) {            LOS_IntRestore(intSave);            return ret;        }
        if (g_losTaskLock) {            LOS_IntRestore(intSave);            return LOS_ERRNO_EVENT_READ_IN_LOCK;        }        runTsk = g_losTask.runTask;        runTsk->eventMask = eventMask;        runTsk->eventMode = mode;        OsSchedTaskWait(&eventCB->stEventList, timeOut);                  ---2        LOS_IntRestore(intSave);        LOS_Schedule();                                                   ---3
        intSave = LOS_IntLock();        if (runTsk->taskStatus & OS_TASK_STATUS_TIMEOUT) {            runTsk->taskStatus &= ~OS_TASK_STATUS_TIMEOUT;            LOS_IntRestore(intSave);            return LOS_ERRNO_EVENT_READ_TIMEOUT;        }
        ret = LOS_EventPoll(&eventCB->uwEventID, eventMask, mode);       ---4    }     ...}

事件讀寫整個過程串起來如下圖所示：

事件銷毀操作

LITE_OS_SEC_TEXT_MINOR UINT32 LOS_EventClear(PEVENT_CB_S eventCB, UINT32 eventMask){    ...    eventCB->uwEventID &= eventMask;    ...}

LITE_OS_SEC_TEXT_INIT UINT32 LOS_EventDestroy(PEVENT_CB_S eventCB){    ...    eventCB->stEventList.pstNext = (LOS_DL_LIST *)NULL;    eventCB->stEventList.pstPrev = (LOS_DL_LIST *)NULL;    ...}

小結(jié)

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