*
*              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_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 you didn't pass a pointer to a queue.
*********************************************************************************************************
*/

void *OSQPend (OS_EVENT *pevent, INT16U timeout, INT8U *err) reentrant
{
    void  *msg;
    OS_Q  *pq;


    OS_ENTER_CRITICAL();
    if (pevent->OSEventType != OS_EVENT_TYPE_Q) {/* Validate event block type                          */
        OS_EXIT_CRITICAL();
        *err = OS_ERR_EVENT_TYPE;
        return ((void *)0);
    }
    pq = 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;
    } else if (OSIntNesting > 0) {               /* See if called from ISR ...                         */
        OS_EXIT_CRITICAL();                      /* ... can't PEND from an ISR                         */
        *err = OS_ERR_PEND_ISR;
    } else {
        OSTCBCur->OSTCBStat    |= OS_STAT_Q;     /* Task will have to pend for a message to be posted  */
        OSTCBCur->OSTCBDly      = timeout;       /* Load timeout into TCB                              */
        OSEventTaskWait(pevent);                 /* Suspend task until event or timeout occurs         */
        OS_EXIT_CRITICAL();
        OSSched();                               /* Find next highest priority task ready to run       */
        OS_ENTER_CRITICAL();
        if ((msg = OSTCBCur->OSTCBMsg) != (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;
        } else if (OSTCBCur->OSTCBStat & OS_STAT_Q) { /* Timed out if status indicates pending on Q    */
            OSEventTO(pevent);
            OS_EXIT_CRITICAL();
            msg                     = (void *)0;      /* No message received                           */
            *err                    = OS_TIMEOUT;     /* Indicate a timeout occured                    */
        } else {
            msg = *pq->OSQOut++;                      /* Extract message from 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 Q    */
                pq->OSQOut = pq->OSQStart;
            }
            OSTCBCur->OSTCBEventPtr = (OS_EVENT *)0;
            OS_EXIT_CRITICAL();
            *err = OS_NO_ERR;
        }
    }                                                 
    return (msg);                                     /* Return message received (or NULL)             */
}
/*$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.
*********************************************************************************************************
*/

INT8U OSQPost (OS_EVENT *pevent, void *msg) reentrant
{
    OS_Q   *pq;


    OS_ENTER_CRITICAL();
    if (pevent->OSEventType != OS_EVENT_TYPE_Q) {     /* Validate event block type                     */
        OS_EXIT_CRITICAL();
        return (OS_ERR_EVENT_TYPE);
    }
    if (pevent->OSEventGrp) {                         /* See if any task pending on queue              */
        OSEventTaskRdy(pevent, msg, OS_STAT_Q);       /* Ready highest priority task waiting on event  */
        OS_EXIT_CRITICAL();
        OSSched();                                    /* Find highest priority task ready to run       */
        return (OS_NO_ERR);
    } else {
        pq = 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);
        } else {
            *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);
    }
}
/*$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.
*********************************************************************************************************
*/

INT8U OSQPostFront (OS_EVENT *pevent, void *msg) reentrant
{
    OS_Q   *pq;


    OS_ENTER_CRITICAL();
    if (pevent->OSEventType != OS_EVENT_TYPE_Q) {     /* Validate event block type                     */
        OS_EXIT_CRITICAL();
        return (OS_ERR_EVENT_TYPE);
    }
    if (pevent->OSEventGrp) {                         /* See if any task pending on queue              */
        OSEventTaskRdy(pevent, msg, OS_STAT_Q);       /* Ready highest priority task waiting on event  */
        OS_EXIT_CRITICAL();
        OSSched();                                    /* Find highest priority task ready to run       */
        return (OS_NO_ERR);
    } else {
        pq = 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);
        } else {
            if (pq->OSQOut == pq->OSQStart) {         /* Wrap OUT ptr if we are at the 1st queue entry */
                pq->OSQOut = pq->OSQEnd;
            }
            pq->OSQOut--;
            *pq->OSQOut = msg;                        /* Insert message into queue                     */
            pq->OSQEntries++;                         /* Update the nbr of entries in the queue        */
            OS_EXIT_CRITICAL();
        }
        return (OS_NO_ERR);
    }
}
/*$PAGE*/
/*
*********************************************************************************************************
*                                        QUERY A MESSAGE QUEUE
*
* Description: This function obtains information about a message queue.
*
* Arguments  : pevent        is a pointer to the event control block associated with the desired mailbox
*
*              pdata         is a pointer to a structure that will contain information about the message
*                            queue.
*
* Returns    : OS_NO_ERR          The call was successful and the message was sent
*              OS_ERR_EVENT_TYPE  If you are attempting to obtain data from a non queue.
*********************************************************************************************************
*/

INT8U OSQQuery (OS_EVENT *pevent, OS_Q_DATA *ppdata) reentrant
{
    OS_Q   *pq;
    INT8U   i;
    INT8U  *psrc;
    INT8U  *pdest;
    
    
    OS_ENTER_CRITICAL();
    if (pevent->OSEventType != OS_EVENT_TYPE_Q) {          /* Validate event block type                */
        OS_EXIT_CRITICAL();
        return (OS_ERR_EVENT_TYPE);
    }
    ppdata->OSEventGrp = pevent->OSEventGrp;                /* Copy message mailbox wait list           */
    psrc              = &pevent->OSEventTbl[0];
    pdest             = &ppdata->OSEventTbl[0];
    for (i = 0; i < OS_EVENT_TBL_SIZE; i++) {
        *pdest++ = *psrc++;   
    }
    pq = (OS_Q *)pevent->OSEventPtr;
    if (pq->OSQEntries > 0) {
        ppdata->OSMsg = pq->OSQOut;                         /* Get next message to return if available  */
    } else {
        ppdata->OSMsg = (void *)0;
    }
    ppdata->OSNMsgs = pq->OSQEntries;
    ppdata->OSQSize = pq->OSQSize;
    OS_EXIT_CRITICAL();
    return (OS_NO_ERR);
}
#endif