原创 UCOS-II中消息队列学习笔记（5）

8.清空消息队列

   pq             = (OS_Q*)pevent->OSEventPtr;      /* Point toqueue storage structure              */

   pq->OSQIn      =pq->OSQStart;

   pq->OSQOut     =pq->OSQStart;

pq->OSQEntries = 0;

9.获取消息队列的状态

消息队列状态结构

typedef struct {

   void          *OSMsg;               /* Pointer to next message to beextracted from queue          */

   INT16U         OSNMsgs;             /* Number of messages in messagequeue                         */

   INT16U         OSQSize;             /* Size of message queue                                       */

   INT8U         OSEventTbl[OS_EVENT_TBL_SIZE];  /*List of tasks waiting for event to occur        */

   INT8U          OSEventGrp;          /* Group corresponding to taskswaiting for event to occur     */

} OS_Q_DATA;

INT8U  OSQQuery (OS_EVENT*pevent, OS_Q_DATA *ppdata) reentrant

{

    OS_ENTER_CRITICAL();

 //将事件(消息队列)结构中的等待任务列表复制到pdata数据结构中

    ppdata->OSEventGrp =pevent->OSEventGrp;                /*Copy message queue wait list           */

    psrc              = &pevent->OSEventTbl[0];

    pdest             = &ppdata->OSEventTbl[0];

#if OS_EVENT_TBL_SIZE > 0                                                          //当事件就绪对应表中的对应值>0时

    *pdest++          = *psrc++;                                                           //地址指针下移一个类型地址，获取信号量的值

#endif

#if OS_EVENT_TBL_SIZE > 1

    *pdest++          = *psrc++;

#endif

#if OS_EVENT_TBL_SIZE > 2

    *pdest++          = *psrc++;

#endif

#if OS_EVENT_TBL_SIZE > 3

    *pdest++          = *psrc++;

#endif

#if OS_EVENT_TBL_SIZE > 4

    *pdest++          = *psrc++;

#endif

#if OS_EVENT_TBL_SIZE > 5

    *pdest++          = *psrc++;

#endif

#if OS_EVENT_TBL_SIZE > 6

    *pdest++          = *psrc++;

#endif

#if OS_EVENT_TBL_SIZE > 7

    *pdest            = *psrc;

#endif

    pq = (OS_Q*)pevent->OSEventPtr;                                   //将队列事件指针保存到pq 中

    if (pq->OSQEntries > 0){                                                   //如果消息队列指针中有消息

        ppdata->OSMsg =*pq->OSQOut;                        /* Get next message to return if available 将最早进入队列得消息复制到数据结构的OSMsg中 */

    } else {

        ppdata->OSMsg = (void*)0;

    }

    ppdata->OSNMsgs =pq->OSQEntries;                                       //消息队列中的消息数放置在数据结构的(OSNMsgs)中

    ppdata->OSQSize =pq->OSQSize;                                              //消息队列中的消息队列容量放置在数据结构得(OSQSize)中

    OS_EXIT_CRITICAL();

    return (OS_NO_ERR);

}