*err = OS_ERR_INVALID_OPT;
             return (pevent);
    }
}
#endif

/*$PAGE*/
/*
*********************************************************************************************************
*                                           FLUSH QUEUE
*
* Description : This function is used to flush the contents of the message queue.
*
* Arguments   : none
*
* Returns     : OS_NO_ERR           upon success
*               OS_ERR_EVENT_TYPE   If you didn't pass a pointer to a queue
*               OS_ERR_PEVENT_NULL  If 'pevent' is a NULL pointer
*********************************************************************************************************
*/

#if OS_Q_FLUSH_EN > 0
INT8U  OSQFlush (OS_EVENT *pevent)
{
#if OS_CRITICAL_METHOD == 3                           /* Allocate storage for CPU status register      */
    OS_CPU_SR  cpu_sr;
#endif
    OS_Q      *pq;


#if OS_ARG_CHK_EN > 0
    if (pevent == (OS_EVENT *)0) {                    /* Validate 'pevent'                             */
        return (OS_ERR_PEVENT_NULL);
    }
    if (pevent->OSEventType != OS_EVENT_TYPE_Q) {     /* Validate event block type                     */
        return (OS_ERR_EVENT_TYPE);
    }
#endif
    OS_ENTER_CRITICAL();
    pq             = (OS_Q *)pevent->OSEventPtr;      /* Point to queue storage structure              */
    pq->OSQIn      = pq->OSQStart;
    pq->OSQOut     = pq->OSQStart;
    pq->OSQEntries = 0;
    OS_EXIT_CRITICAL();
    return (OS_NO_ERR);
}
#endif

/*$PAGE*/
/*
*********************************************************************************************************
*                                     PEND ON A QUEUE FOR A MESSAGE
*
* Description: This function waits for a message to be sent to a queue
*
* Arguments  : pevent        is a pointer to the event control block associated with the desired queue
*
*              timeout       is an optional timeout period (in clock ticks).  If non-zero, your task will
*                            wait for a message to arrive at the queue up to the amount of time
*                            specified by this argument.  If you specify 0, however, your task will wait
*                            forever at the specified queue or, until a message arrives.
*
*              err           is a pointer to where an error message will be deposited.  Possible error
*                            messages are:
*
*                            OS_NO_ERR           The call was successful and your task received a
*                                                message.
*                            OS_TIMEOUT          A message was not received within the specified timeout
*                            OS_ERR_EVENT_TYPE   You didn't pass a pointer to a queue
*                            OS_ERR_PEVENT_NULL  If 'pevent' is a NULL pointer
*                            OS_ERR_PEND_ISR     If you called this function from an ISR and the result
*                                                would lead to a suspension.
*
* Returns    : != (void *)0  is a pointer to the message received
*              == (void *)0  if no message was received or,
*                            if 'pevent' is a NULL pointer or,
*                            if you didn't pass a pointer to a queue.
*********************************************************************************************************
*/

void  *OSQPend (OS_EVENT *pevent, INT16U timeout, INT8U *err)
{
#if OS_CRITICAL_METHOD == 3                      /* Allocate storage for CPU status register           */
    OS_CPU_SR  cpu_sr;
#endif
    void      *msg;
    OS_Q      *pq;


    if (OSIntNesting > 0) {                      /* See if called from ISR ...                         */
        *err = OS_ERR_PEND_ISR;                  /* ... can't PEND from an ISR                         */
        return ((void *)0);
    }
#if OS_ARG_CHK_EN > 0
    if (pevent == (OS_EVENT *)0) {               /* Validate 'pevent'                                  */
        *err = OS_ERR_PEVENT_NULL;
        return ((void *)0);
    }
    if (pevent->OSEventType != OS_EVENT_TYPE_Q) {/* Validate event block type                          */
        *err = OS_ERR_EVENT_TYPE;
        return ((void *)0);
    }
#endif
    OS_ENTER_CRITICAL();
    pq = (OS_Q *)pevent->OSEventPtr;             /* Point at queue control block                       */
    if (pq->OSQEntries > 0) {                    /* See if any messages in the queue                   */
        msg = *pq->OSQOut++;                     /* Yes, extract oldest message from the queue         */
        pq->OSQEntries--;                        /* Update the number of entries in the queue          */
        if (pq->OSQOut == pq->OSQEnd) {          /* Wrap OUT pointer if we are at the end of the queue */
            pq->OSQOut = pq->OSQStart;
        }
        OS_EXIT_CRITICAL();
        *err = OS_NO_ERR;
        return (msg);                            /* Return message received                            */
    }
    OSTCBCur->OSTCBStat |= OS_STAT_Q;            /* Task will have to pend for a message to be posted  */
    OSTCBCur->OSTCBDly   = timeout;              /* Load timeout into TCB                              */
    OS_EventTaskWait(pevent);                    /* Suspend task until event or timeout occurs         */
    OS_EXIT_CRITICAL();
    OS_Sched();                                  /* Find next highest priority task ready to run       */
    OS_ENTER_CRITICAL();
    msg = OSTCBCur->OSTCBMsg;
    if (msg != (void *)0) {                      /* Did we get a message?                              */
        OSTCBCur->OSTCBMsg      = (void *)0;     /* Extract message from TCB (Put there by QPost)      */
        OSTCBCur->OSTCBStat     = OS_STAT_RDY;
        OSTCBCur->OSTCBEventPtr = (OS_EVENT *)0; /* No longer waiting for event                        */
        OS_EXIT_CRITICAL();
        *err                    = OS_NO_ERR;
        return (msg);                            /* Return message received                            */
    }
    OS_EventTO(pevent);                          /* Timed out                                          */
    OS_EXIT_CRITICAL();
    *err = OS_TIMEOUT;                           /* Indicate a timeout occured                         */
    return ((void *)0);                          /* No message received                                */
}
/*$PAGE*/
/*
*********************************************************************************************************
*                                        POST MESSAGE TO A QUEUE
*
* Description: This function sends a message to a queue
*
* Arguments  : pevent        is a pointer to the event control block associated with the desired queue
*
*              msg           is a pointer to the message to send.  You MUST NOT send a NULL pointer.
*
* Returns    : OS_NO_ERR             The call was successful and the message was sent
*              OS_Q_FULL             If the queue cannot accept any more messages because it is full.
*              OS_ERR_EVENT_TYPE     If you didn't pass a pointer to a queue.
*              OS_ERR_PEVENT_NULL    If 'pevent' is a NULL pointer
*              OS_ERR_POST_NULL_PTR  If you are attempting to post a NULL pointer
*********************************************************************************************************
*/

#if OS_Q_POST_EN > 0
INT8U  OSQPost (OS_EVENT *pevent, void *msg)
{
#if OS_CRITICAL_METHOD == 3                      /* Allocate storage for CPU status register           */
    OS_CPU_SR  cpu_sr;
#endif
    OS_Q      *pq;


#if OS_ARG_CHK_EN > 0
    if (pevent == (OS_EVENT *)0) {                    /* Validate 'pevent'                             */
        return (OS_ERR_PEVENT_NULL);
    }
    if (msg == (void *)0) {                           /* Make sure we are not posting a NULL pointer   */
        return (OS_ERR_POST_NULL_PTR);
    }
    if (pevent->OSEventType != OS_EVENT_TYPE_Q) {     /* Validate event block type                     */
        return (OS_ERR_EVENT_TYPE);
    }
#endif
    OS_ENTER_CRITICAL();
    if (pevent->OSEventGrp != 0x00) {                 /* See if any task pending on queue              */
        OS_EventTaskRdy(pevent, msg, OS_STAT_Q);      /* Ready highest priority task waiting on event  */
        OS_EXIT_CRITICAL();
        OS_Sched();                                   /* Find highest priority task ready to run       */
        return (OS_NO_ERR);
    }
    pq = (OS_Q *)pevent->OSEventPtr;                  /* Point to queue control block                  */
    if (pq->OSQEntries >= pq->OSQSize) {              /* Make sure queue is not full                   */
        OS_EXIT_CRITICAL();
        return (OS_Q_FULL);
    }
    *pq->OSQIn++ = msg;                               /* Insert message into queue                     */
    pq->OSQEntries++;                                 /* Update the nbr of entries in the queue        */
    if (pq->OSQIn == pq->OSQEnd) {                    /* Wrap IN ptr if we are at end of queue         */
        pq->OSQIn = pq->OSQStart;
    }
    OS_EXIT_CRITICAL();
    return (OS_NO_ERR);
}
#endif
/*$PAGE*/
/*
*********************************************************************************************************
*                                   POST MESSAGE TO THE FRONT OF A QUEUE
*
* Description: This function sends a message to a queue but unlike OSQPost(), the message is posted at
*              the front instead of the end of the queue.  Using OSQPostFront() allows you to send
*              'priority' messages.
*
* Arguments  : pevent        is a pointer to the event control block associated with the desired queue
*
*              msg           is a pointer to the message to send.  You MUST NOT send a NULL pointer.
*
* Returns    : OS_NO_ERR             The call was successful and the message was sent
*              OS_Q_FULL             If the queue cannot accept any more messages because it is full.
*              OS_ERR_EVENT_TYPE     If you didn't pass a pointer to a queue.
*              OS_ERR_PEVENT_NULL    If 'pevent' is a NULL pointer
*              OS_ERR_POST_NULL_PTR  If you are attempting to post to a non queue.
*********************************************************************************************************
*/

#if OS_Q_POST_FRONT_EN > 0
INT8U  OSQPostFront (OS_EVENT *pevent, void *msg)
{
#if OS_CRITICAL_METHOD == 3                      /* Allocate storage for CPU status register           */
    OS_CPU_SR  cpu_sr;
#endif
    OS_Q      *pq;


#if OS_ARG_CHK_EN > 0
    if (pevent == (OS_EVENT *)0) {                    /* Validate 'pevent'                             */
        return (OS_ERR_PEVENT_NULL);
    }
    if (msg == (void *)0) {                           /* Make sure we are not posting a NULL pointer   */
        return (OS_ERR_POST_NULL_PTR);
    }
    if (pevent->OSEventType != OS_EVENT_TYPE_Q) {     /* Validate event block type                     */
        return (OS_ERR_EVENT_TYPE);
    }
#endif
    OS_ENTER_CRITICAL();
    if (pevent->OSEventGrp != 0x00) {                 /* See if any task pending on queue              */
        OS_EventTaskRdy(pevent, msg, OS_STAT_Q);      /* Ready highest priority task waiting on event  */
        OS_EXIT_CRITICAL();
        OS_Sched();                                   /* Find highest priority task ready to run       */
        return (OS_NO_ERR);