typedef struct QueueDefinition
{
    int8_t *pcHead;             /* 指向隊(duì)列存儲(chǔ)區(qū)起始位置,即第一個(gè)隊(duì)列項(xiàng) */
    int8_t *pcTail;             /* 指向隊(duì)列存儲(chǔ)區(qū)結(jié)束后的下一個(gè)字節(jié) */
    int8_t *pcWriteTo;          /* 指向下隊(duì)列存儲(chǔ)區(qū)的下一個(gè)空閑位置 */
    union                       /* 使用聯(lián)合體用來(lái)確保兩個(gè)互斥的結(jié)構(gòu)體成員不會(huì)同時(shí)出現(xiàn) */
    {
        int8_t *pcReadFrom;     /* 當(dāng)結(jié)構(gòu)體用于隊(duì)列時(shí),這個(gè)字段指向出隊(duì)項(xiàng)目中的最后一個(gè). */
        UBaseType_t uxRecursiveCallCount;/* 當(dāng)結(jié)構(gòu)體用于互斥量時(shí),用作計(jì)數(shù)器,保存遞歸互斥量被"獲取"的次數(shù). */
    } u;
    List_t xTasksWaitingToSend;      /* 因?yàn)榈却腙?duì)而阻塞的任務(wù)列表,按照優(yōu)先級(jí)順序存儲(chǔ) */
    List_t xTasksWaitingToReceive;   /* 因?yàn)榈却?duì)列項(xiàng)而阻塞的任務(wù)列表,按照優(yōu)先級(jí)順序存儲(chǔ) */
    volatile UBaseType_t uxMessagesWaiting;/*< 當(dāng)前隊(duì)列的隊(duì)列項(xiàng)數(shù)目 */
    UBaseType_t uxLength;            /* 隊(duì)列項(xiàng)的數(shù)目 */
    UBaseType_t uxItemSize;          /* 每個(gè)隊(duì)列項(xiàng)的大小 */
    volatile BaseType_t xRxLock;   /* 隊(duì)列上鎖后,存儲(chǔ)從隊(duì)列收到的列表項(xiàng)數(shù)目，如果隊(duì)列沒(méi)有上鎖，設(shè)置為queueUNLOCKED */
    volatile BaseType_t xTxLock;   /* 隊(duì)列上鎖后,存儲(chǔ)發(fā)送到隊(duì)列的列表項(xiàng)數(shù)目，如果隊(duì)列沒(méi)有上鎖，設(shè)置為queueUNLOCKED */
    #if ( configUSE_QUEUE_SETS == 1 )
        struct QueueDefinition *pxQueueSetContainer;
    #endif
     #if ( configUSE_TRACE_FACILITY == 1 )
        UBaseType_t uxQueueNumber;
        uint8_t ucQueueType;
    #endif
    #if ( configSUPPORT_STATIC_ALLOCATION == 1 )
        uint8_t ucStaticAllocationFlags;
    #endif
} xQUEUE;
 typedef xQUEUE Queue_t;

QueueHandle_t xQueueGenericCreate
        ( 
                const UBaseType_t uxQueueLength, 
                const UBaseType_t uxItemSize, 
                uint8_t *pucQueueStorage, 
                StaticQueue_t *pxStaticQueue, 
                const uint8_t ucQueueType 
        )

QueueHandle_t xQueueGenericCreate( 
              const UBaseType_t uxQueueLength, 
              const UBaseType_t uxItemSize, 
             uint8_t *pucQueueStorage, 
             StaticQueue_t *pxStaticQueue, 
             const uint8_t ucQueueType )
{
Queue_t *pxNewQueue;
    /* 如果使能可視化跟蹤調(diào)試,這里用來(lái)消除編譯器警告. */
    ( void ) ucQueueType;
    /*分配隊(duì)列結(jié)構(gòu)體和隊(duì)列項(xiàng)存儲(chǔ)空間.可以靜態(tài)也可以動(dòng)態(tài)分配,取決于參數(shù)值,FreeRTOS默認(rèn)采取動(dòng)態(tài)分配 */
    pxNewQueue = prvAllocateQueueMemory( uxQueueLength, uxItemSize, &pucQueueStorage, pxStaticQueue );
    if( pxNewQueue != NULL )
    {
        if( uxItemSize == ( UBaseType_t ) 0 )
        {
            /* 沒(méi)有為隊(duì)列項(xiàng)存儲(chǔ)分配內(nèi)存,但是pcHead指針不能設(shè)置為NULL,因?yàn)殛?duì)列用作互斥量時(shí),pcHead要設(shè)置成NULL.這里只是將pcHead指向一個(gè)已知的區(qū)域 */
            pxNewQueue->pcHead = ( int8_t * ) pxNewQueue;
        }
        else
        {
            /* 指向隊(duì)列項(xiàng)存儲(chǔ)區(qū)域*/
            pxNewQueue->pcHead = ( int8_t * ) pucQueueStorage;
        }
        /* 初始化隊(duì)列結(jié)構(gòu)體成員*/
        pxNewQueue->uxLength = uxQueueLength;
        pxNewQueue->uxItemSize = uxItemSize;
        ( void ) xQueueGenericReset( pxNewQueue, pdTRUE );
        #if ( configUSE_TRACE_FACILITY == 1 )
        {
            pxNewQueue->ucQueueType = ucQueueType;
        }
        #endif /* configUSE_TRACE_FACILITY */
        traceQUEUE_CREATE( pxNewQueue );
    }
    return ( QueueHandle_t ) pxNewQueue;
}

BaseType_t xQueueGenericSend
				( 
					QueueHandle_t xQueue, 
					const void * const pvItemToQueue, 
					TickType_t xTicksToWait, 
					const BaseType_t xCopyPosition 
				)

BaseType_t xQueueGenericSend( 
				QueueHandle_t xQueue, 
				const void * const pvItemToQueue, 
				TickType_t xTicksToWait, 
				const BaseType_t xCopyPosition )
{
BaseType_t xEntryTimeSet = pdFALSE, xYieldRequired;
TimeOut_t xTimeOut;
Queue_t * const pxQueue = ( Queue_t * ) xQueue;
     for( ;; )
    {
        taskENTER_CRITICAL();
        {
            /* 隊(duì)列還有空閑?正在運(yùn)行的任務(wù)一定要比等待訪問(wèn)隊(duì)列的任務(wù)優(yōu)先級(jí)高.如果使用覆蓋式入隊(duì),則不需要關(guān)注隊(duì)列是否滿*/
            if( ( pxQueue->uxMessagesWaiting < pxQueue->uxLength ) || ( xCopyPosition == queueOVERWRITE ) )
            {
                /*完成數(shù)據(jù)拷貝工作,分為從隊(duì)列尾入隊(duì),從隊(duì)列首入隊(duì)和覆蓋式入隊(duì)*/
                xYieldRequired = prvCopyDataToQueue( pxQueue, pvItemToQueue, xCopyPosition );
                /* 如果有任務(wù)在此等待隊(duì)列數(shù)據(jù)到來(lái),則將該任務(wù)解除阻塞*/
                if( listLIST_IS_EMPTY( &( pxQueue->xTasksWaitingToReceive ) ) == pdFALSE )
                {
                    /*有任務(wù)因等待出隊(duì)而阻塞,則將任務(wù)從隊(duì)列等待接收列表中刪除,然后加入到就緒列表*/
                    if( xTaskRemoveFromEventList( &( pxQueue->xTasksWaitingToReceive ) ) != pdFALSE )
                    {
                        /* 解除阻塞的任務(wù)有更高的優(yōu)先級(jí),則當(dāng)前任務(wù)要讓出CPU,因此觸發(fā)一個(gè)上下文切換.又因?yàn)楝F(xiàn)在還在臨界區(qū),要等退出臨界區(qū)后,才會(huì)執(zhí)行上下文切換.*/
                        queueYIELD_IF_USING_PREEMPTION();
                    }
                }
                else if( xYieldRequired != pdFALSE )
                {
                    /* 這個(gè)分支處理特殊情況*/
                    queueYIELD_IF_USING_PREEMPTION();
                }
                taskEXIT_CRITICAL();
                return pdPASS;
            }
            else
            {
                if( xTicksToWait == ( TickType_t ) 0 )
                {
                    /* 如果隊(duì)列滿并且沒(méi)有設(shè)置超時(shí),則直接退出 */
                    taskEXIT_CRITICAL();
                    /* 返回隊(duì)列滿錯(cuò)誤碼 */
                    return errQUEUE_FULL;
                }
                else if( xEntryTimeSet == pdFALSE )
                {
                    /* 隊(duì)列滿并且規(guī)定了阻塞時(shí)間,因此需要配置超時(shí)結(jié)構(gòu)體對(duì)象 */
                    vTaskSetTimeOutState( &xTimeOut );
                    xEntryTimeSet = pdTRUE;
                }
            }
        }
        taskEXIT_CRITICAL();
        /* 退出臨界區(qū),至此,中斷和其它任務(wù)可以向這個(gè)隊(duì)列執(zhí)行入隊(duì)(投遞)或出隊(duì)(讀取)操作.因?yàn)殛?duì)列滿,任務(wù)無(wú)法入隊(duì),下面的代碼將當(dāng)前任務(wù)將阻塞在這個(gè)隊(duì)列上,在這段代碼執(zhí)行過(guò)程中我們需要掛起調(diào)度器,防止其它任務(wù)操作隊(duì)列事件列表;掛起調(diào)度器雖然可以禁止其它任務(wù)操作這個(gè)隊(duì)列,但并不能阻止中斷服務(wù)程序操作這個(gè)隊(duì)列,因此還需要將隊(duì)列上鎖,防止中斷程序讀取隊(duì)列后,使阻塞在出隊(duì)操作其它任務(wù)解除阻塞,執(zhí)行上下文切換(因?yàn)檎{(diào)度器掛起后,不允許執(zhí)行上下文切換) */
        vTaskSuspendAll();
        prvLockQueue( pxQueue );
        /* 查看任務(wù)的超時(shí)時(shí)間是否到期 */
        if( xTaskCheckForTimeOut( &xTimeOut, &xTicksToWait ) == pdFALSE )
        {
            if( prvIsQueueFull( pxQueue ) != pdFALSE )
            {
                /*超時(shí)時(shí)間未到期,并且隊(duì)列仍然滿*/
                vTaskPlaceOnEventList( &( pxQueue->xTasksWaitingToSend ), xTicksToWait );
                /* 解除隊(duì)列鎖,如果有任務(wù)要解除阻塞,則將任務(wù)移到掛起就緒列表中(因?yàn)楫?dāng)前調(diào)度器掛起,所以不能移到就緒列表)*/
                prvUnlockQueue( pxQueue );
                /* 恢復(fù)調(diào)度器,將任務(wù)從掛起就緒列表移到就緒列表中*/
                if( xTaskResumeAll() == pdFALSE )
                {
                    portYIELD_WITHIN_API();
                }
            }
            else
            {
                /* 隊(duì)列有空閑,重試 */
                prvUnlockQueue( pxQueue );
                ( void ) xTaskResumeAll();
            }
        }
        else
        {
            /* 超時(shí)時(shí)間到期,返回隊(duì)列滿錯(cuò)誤碼*/
            prvUnlockQueue( pxQueue );
            ( void ) xTaskResumeAll();
            traceQUEUE_SEND_FAILED( pxQueue );
            return errQUEUE_FULL;
        }
    }
}

BaseType_t xQueueGenericSendFromISR
				( 
						QueueHandle_t xQueue, 
						const void * const pvItemToQueue, 
						BaseType_t * const pxHigherPriorityTaskWoken, 
						const BaseType_t xCopyPosition 
				)

BaseType_t xQueueGenericSendFromISR(
 				QueueHandle_t xQueue, 
				const void * const pvItemToQueue, 
				BaseType_t * const pxHigherPriorityTaskWoken, 
				const BaseType_t xCopyPosition )
{
BaseType_t xReturn;
UBaseType_t uxSavedInterruptStatus;
Queue_t * const pxQueue = ( Queue_t * ) xQueue;
    uxSavedInterruptStatus = portSET_INTERRUPT_MASK_FROM_ISR();
    {
        if( ( pxQueue->uxMessagesWaiting < pxQueue->uxLength ) || ( xCopyPosition == queueOVERWRITE ) )
        {
            traceQUEUE_SEND_FROM_ISR( pxQueue );
            /*完成數(shù)據(jù)拷貝工作,分為從隊(duì)列尾入隊(duì),從隊(duì)列首入隊(duì)和覆蓋式入隊(duì)*/
            ( void ) prvCopyDataToQueue( pxQueue, pvItemToQueue, xCopyPosition );
            /*檢查隊(duì)列是否上鎖,如果上鎖,則隊(duì)列事件列表不能被改變 */
            if( pxQueue->xTxLock == queueUNLOCKED )
            {   /*隊(duì)列沒(méi)有上鎖*/
                if( listLIST_IS_EMPTY( &( pxQueue->xTasksWaitingToReceive ) ) == pdFALSE )
                {
                    if( xTaskRemoveFromEventList( &( pxQueue->xTasksWaitingToReceive ) ) != pdFALSE )
                    {
                        /* 解除阻塞的任務(wù)優(yōu)先級(jí)比當(dāng)前任務(wù)高,記錄上下文切換請(qǐng)求,等返回中斷服務(wù)程序后,可以顯示的強(qiáng)制上下文切換 */
                        if( pxHigherPriorityTaskWoken != NULL )
                        {
                            *pxHigherPriorityTaskWoken = pdTRUE;
                        }
                    }
                }
            }
            else
            {
                /* 隊(duì)列上鎖,增加鎖計(jì)數(shù)器,等到任務(wù)解除隊(duì)列鎖時(shí),使用這個(gè)計(jì)數(shù)器就可以知道有多少數(shù)據(jù)入隊(duì),可以最多解除多少個(gè)因等待從隊(duì)列讀數(shù)據(jù)而阻塞的任務(wù) */
                ++( pxQueue->xTxLock );
            }
            xReturn = pdPASS;
        }
        else
        {
            xReturn = errQUEUE_FULL;
        }
    }
    portCLEAR_INTERRUPT_MASK_FROM_ISR( uxSavedInterruptStatus );
    return xReturn;
}