quc.c

test file nucleus source

    }

    /* Release protection against access to the queue.  */
    TCT_Unprotect();

    /* Return to user mode */
    NU_USER_MODE();

    /* Return the completion status.  */
    return(status);
}


/*************************************************************************/
/*                                                                       */
/* FUNCTION                                                              */
/*                                                                       */
/*      QUC_Receive_From_Queue                                           */
/*                                                                       */
/* DESCRIPTION                                                           */
/*                                                                       */
/*      This function receives a message from the specified queue.  The  */
/*      size of the message is specified by the caller.  If there is a   */
/*      message currently in the queue, the message is removed from the  */
/*      queue and placed in the caller's area.  Suspension is possible   */
/*      if the request cannot be satisfied.                              */
/*                                                                       */
/* CALLED BY                                                             */
/*                                                                       */
/*      Application                                                      */
/*      QUCE_Receive_From_Queue             Error checking shell         */
/*                                                                       */
/* CALLS                                                                 */
/*                                                                       */
/*      CSC_Place_On_List                   Place on suspend list        */
/*      CSC_Priority_Place_On_List          Place on priority list       */
/*      CSC_Remove_From_List                Remove from suspend list     */
/*      [HIC_Make_History_Entry]            Make entry in history log    */
/*      TCC_Resume_Task                     Resume a suspended task      */
/*      TCC_Suspend_Task                    Suspend calling task         */
/*      TCC_Task_Priority                   Pickup task's priority       */
/*      [TCT_Check_Stack]                   Stack checking function      */
/*      TCT_Control_To_System               Transfer control to system   */
/*      TCT_Current_Thread                  Pickup current thread pointer*/
/*      TCT_System_Protect                  Protect queue                */
/*      TCT_Unprotect                       Release protection           */
/*                                                                       */
/* INPUTS                                                                */
/*                                                                       */
/*      queue_ptr                           Queue control block pointer  */
/*      message                             Pointer to message to send   */
/*      size                                Size of the message          */
/*      actual_size                         Size of message received     */
/*      suspend                             Suspension option if empty   */
/*                                                                       */
/* OUTPUTS                                                               */
/*                                                                       */
/*      NU_SUCCESS                          If service is successful     */
/*      NU_QUEUE_EMPTY                      If queue is currently empty  */
/*      NU_TIMEOUT                          If timeout on service expires*/
/*      NU_QUEUE_DELETED                    If queue was deleted during  */
/*                                            suspension                 */
/*      NU_QUEUE_RESET                      If queue was reset during    */
/*                                            suspension                 */
/*                                                                       */
/* HISTORY                                                               */
/*                                                                       */
/*         DATE                    REMARKS                               */
/*                                                                       */
/*      03-01-1993      Created initial version 1.0                      */
/*      04-19-1993      Verified version 1.0                             */
/*      11-01-1993      Corrected a problem resuming a                   */
/*                      task suspended on a full queue                   */
/*                      that only has a capacity of a                    */
/*                      single message, resulting in                     */
/*                      version 1.0b                                     */
/*      11-01-1993      Verified version 1.0b                            */
/*      03-01-1994      Changed function interfaces to                   */
/*                      match those in prototype,                        */
/*                      added register options, changed                  */
/*                      protection logic to reduce                       */
/*                      overhead, optimized copy loop,                   */
/*                      resulting in version 1.1                         */
/*                                                                       */
/*      03-18-1994      Verified version 1.1                             */
/*      01-28-1998      Corrected SPR412.                                */
/*                                                                       */
/*************************************************************************/
STATUS  QUC_Receive_From_Queue(NU_QUEUE *queue_ptr, VOID *message,
                UNSIGNED size, UNSIGNED *actual_size, UNSIGNED suspend)
{

R1 QU_QCB      *queue;                      /* Queue control block ptr   */
QU_SUSPEND      suspend_block;              /* Allocate suspension block */
QU_SUSPEND     *suspend_ptr;                /* Pointer to suspend block  */
R3 UNSIGNED_PTR source;                     /* Pointer to source         */
R4 UNSIGNED_PTR destination;                /* Pointer to destination    */
TC_TCB         *task;                       /* Task pointer              */
UNSIGNED        copy_size;                  /* Number of words to copy   */
R2 INT          i;                          /* Working counter           */
STATUS          preempt;                    /* Preemption flag           */
STATUS          status;                     /* Completion status         */
NU_SUPERV_USER_VARIABLES


    /* Move input queue pointer into internal pointer.  */
    queue =  (QU_QCB *) queue_ptr;

    /* Switch to supervisor mode */
    NU_SUPERVISOR_MODE();

#ifdef  NU_ENABLE_STACK_CHECK

    /* Call stack checking function to check for an overflow condition.  */
    TCT_Check_Stack();

#endif

#ifdef  NU_ENABLE_HISTORY

    /* Make an entry that corresponds to this function in the system history
       log.  */
    HIC_Make_History_Entry(NU_RECEIVE_FROM_QUEUE_ID, (UNSIGNED) queue,
                                        (UNSIGNED) message, (UNSIGNED) size);

#endif

    /* Initialize the status as successful.  */
    status =  NU_SUCCESS;

    /* Protect against simultaneous access to the queue.  */
    TCT_System_Protect();

    /* Determine if an urgent message request is currently suspended.  */
    if (queue -> qu_urgent_list)
    {

        /* If so, copy the message from the suspended request block and
           resume the associated task.  */

        /* Decrement the number of tasks waiting on queue.  */
        queue -> qu_tasks_waiting--;

        /* Remove the first suspended block from the list.  */
        suspend_ptr =  queue -> qu_urgent_list;
        CSC_Remove_From_List((CS_NODE **) &(queue -> qu_urgent_list),
                                          &(suspend_ptr -> qu_suspend_link));

        /* Setup the source and destination pointers.  */
        destination =   (UNSIGNED_PTR) message;
        source =        suspend_ptr -> qu_message_area;

        /* Initialize the return status.  */
        suspend_ptr -> qu_return_status =  NU_SUCCESS;

        /* Loop to actually copy the message.  */
        i =  (INT) suspend_ptr -> qu_message_size;
        do
        {
            *(destination++) =  *(source);
            if ((--i) == 0)
                break;
            source++;
        } while (1);

        /* Return the size of the message copied.  */
        *actual_size =  suspend_ptr -> qu_message_size;

        /* Wakeup the waiting task and check for preemption.  */
        preempt =
            TCC_Resume_Task((NU_TASK *) suspend_ptr -> qu_suspended_task,
                                                     NU_QUEUE_SUSPEND);

        /* Determine if preemption needs to take place. */
        if (preempt)

             /* Transfer control to the system if the resumed task function
                detects a preemption condition.  */
             TCT_Control_To_System();
    }

    /* Determine if there are messages in the queue.  */
    else if (queue -> qu_messages)
    {

        /* Copy message from queue into the caller's area.  */

        /* Setup the source and destination pointers.  */
        source =       queue -> qu_read;
        destination =  (UNSIGNED_PTR) message;

        /* Process according to the type of message supported by the queue. */
        if (queue -> qu_fixed_size)
        {

            /* Queue supports fixed-size messages.  */

            /* Copy the message from the queue area into the destination.  */
            i =  (INT) size;
            do
            {
                *(destination) =  *(source++);
                if ((--i) == 0)
                    break;
                destination++;
            } while (1);
        }
        else
        {

            /* Queue supports variable-size messages.  */

            /* Variable length message size is actually in the queue area. */
            size =  *(source++);

            /* Check for a wrap-around condition on the queue.  */
            if (source >= queue -> qu_end)

                /* Wrap the read pointer back to the top of the queue
                   area.  */
                source =  queue -> qu_start;

            /* Increment the number of available words in the queue.  */
            queue -> qu_available++;

            /* Calculate the number of words remaining from the read pointer
               to the bottom of the queue.  */
            copy_size =  queue -> qu_end - source;

            /* Determine if the message needs to be wrapped around the
               edge of the queue area.  */
            if (copy_size >= size)
            {

                /* Copy the whole message at once.  */
                i =  (INT) size;
                do
                {
                    *(destination) =  *(source++);
                    if ((--i) == 0)
                        break;
                    destination++;
                } while (1);
            }
            else
            {

                /* Copy the first half of the message.  */
                i =  (INT) copy_size;
                do
                {
                    *(destination++) =  *(source);
                    if ((--i) == 0)
                        break;
                    source++;
                } while (1);

                /* Copy the second half of the message.  */
                source =  queue -> qu_start;
                i =  (INT) (size - copy_size);
                do
                {
                    *(destination) =  *(source++);
                    if ((--i) == 0)
                        break;
                    destination++;
                } while (1);
            }
        }

        /* Check again for wrap-around condition on the read pointer. */
        if (source >= queue -> qu_end)

            /* Move the read pointer to the top of the queue area.  */
            queue -> qu_read =  queue -> qu_start;
        else

            /* Move the read pointer to where the copy left off.  */
            queue -> qu_read =  source;

        /* Increment the number of available words.  */
        queue -> qu_available =  queue -> qu_available + size;

        /* Decrement the number of messages in the queue.  */
        queue -> qu_messages--;

        /* Return the number of words received.  */
        *actual_size =  size;

#ifdef INCLUDE_PROVIEW
        _RTProf_DumpQueue(RT_PROF_RECEIVE_FROM_QUEUE,queue,RT_PROF_OK);