mbc.c

test file nucleus source

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

    /* Determine if the mailbox is empty or full.  */
    if (mailbox -> mb_message_present)
    {

        /* Mailbox already has a message.  Determine if suspension is
           required.  */
        if (suspend)
        {

            /* Suspension is requested.   */

            /* Increment the number of tasks waiting.  */
            mailbox -> mb_tasks_waiting++;

#ifdef INCLUDE_PROVIEW
    _RTProf_DumpMailBox(RT_PROF_SEND_TO_MAILBOX,mailbox,RT_PROF_WAIT);
#endif /* INCLUDE_PROVIEW */

            /* Setup the suspend block and suspend the calling task.  */
            suspend_ptr =  &suspend_block;
            suspend_ptr -> mb_mailbox =                  mailbox;
            suspend_ptr -> mb_suspend_link.cs_next =     NU_NULL;
            suspend_ptr -> mb_suspend_link.cs_previous = NU_NULL;
            suspend_ptr -> mb_message_area =             (UNSIGNED *) message;
            task =                           (TC_TCB *)  TCT_Current_Thread();
            suspend_ptr -> mb_suspended_task =           task;

            /* Determine if priority or FIFO suspension is associated with the
               mailbox.  */
            if (mailbox -> mb_fifo_suspend)
            {

                /* FIFO suspension is required.  Link the suspend block into
                   the list of suspended tasks on this mailbox.  */
                CSC_Place_On_List((CS_NODE **) &(mailbox ->mb_suspension_list),
                                        &(suspend_ptr -> mb_suspend_link));
            }
            else
            {

                /* Get the priority of the current thread so the suspend block
                   can be placed in the appropriate place.  */
                suspend_ptr -> mb_suspend_link.cs_priority =
                                                     TCC_Task_Priority(task);

                CSC_Priority_Place_On_List((CS_NODE **)
                        &(mailbox -> mb_suspension_list),
                                        &(suspend_ptr -> mb_suspend_link));
            }

            /* Finally, suspend the calling task. Note that the suspension call
               automatically clears the protection on the mailbox.  */
            TCC_Suspend_Task((NU_TASK *) task, NU_MAILBOX_SUSPEND,
                                MBC_Cleanup, suspend_ptr, suspend);

            /* Pickup the return status.  */
            status =  suspend_ptr -> mb_return_status;
        }
        else
        {

            /* Return a status of NU_MAILBOX_FULL because there is no
               room in the mailbox for the message.  */
            status =  NU_MAILBOX_FULL;
#ifdef INCLUDE_PROVIEW
            _RTProf_DumpMailBox(RT_PROF_SEND_TO_MAILBOX,mailbox,RT_PROF_FAIL);
#endif /* INCLUDE_PROVIEW */

        }
    }
    else
    {

        /* Determine if a task is waiting on the mailbox.  */
        if (mailbox -> mb_suspension_list)
        {

            /* Task is waiting on mailbox for a message.  */

            /* Decrement the number of tasks waiting on mailbox.  */
            mailbox -> mb_tasks_waiting--;

#ifdef INCLUDE_PROVIEW
            _RTProf_DumpMailBox(RT_PROF_SEND_TO_MAILBOX,mailbox,RT_PROF_OK);
#endif /* INCLUDE_PROVIEW */

            /* Remove the first suspended block from the list.  */
            suspend_ptr =  mailbox -> mb_suspension_list;
            CSC_Remove_From_List((CS_NODE **)
                &(mailbox -> mb_suspension_list),
                                &(suspend_ptr -> mb_suspend_link));

            /* Setup the source and destination pointers.  */
            source_ptr =       (UNSIGNED *) message;
            destination_ptr =  suspend_ptr -> mb_message_area;

            /* Copy the message directly into the waiting task's
               destination.  */
            *destination_ptr       =  *source_ptr;
            *(destination_ptr + 1) =  *(source_ptr + 1);
            *(destination_ptr + 2) =  *(source_ptr + 2);
            *(destination_ptr + 3) =  *(source_ptr + 3);

            /* Setup the appropriate return value.  */
            suspend_ptr -> mb_return_status =  NU_SUCCESS;

            /* Wakeup the waiting task and check for preemption.  */
            preempt =
               TCC_Resume_Task((NU_TASK *) suspend_ptr -> mb_suspended_task,
                                                NU_MAILBOX_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();
        }
        else
        {

            /* Mailbox is empty and no task is waiting.  */

            /* Setup the source and destination pointers.  */
            source_ptr =       (UNSIGNED *) message;
            destination_ptr =  &(mailbox -> mb_message_area[0]);

            /* Place the message in the mailbox. */
            *destination_ptr =        *source_ptr;
            *(destination_ptr + 1) =  *(source_ptr + 1);
            *(destination_ptr + 2) =  *(source_ptr + 2);
            *(destination_ptr + 3) =  *(source_ptr + 3);

            /* Indicate that the mailbox has a message.  */
            mailbox -> mb_message_present =  NU_TRUE;

#ifdef INCLUDE_PROVIEW
            _RTProf_DumpMailBox(RT_PROF_SEND_TO_MAILBOX,mailbox,RT_PROF_OK);
#endif /* INCLUDE_PROVIEW */
        }
    }

    /* Release protection.  */
    TCT_Unprotect();

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

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


/*************************************************************************/
/*                                                                       */
/* FUNCTION                                                              */
/*                                                                       */
/*      MBC_Receive_From_Mailbox                                         */
/*                                                                       */
/* DESCRIPTION                                                           */
/*                                                                       */
/*      This function receives a message from the specified mailbox.     */
/*      If there is a message currently in the mailbox, the message is   */
/*      removed from the mailbox and placed in the caller's area.        */
/*      Otherwise, if no message is present in the mailbox, suspension   */
/*      of the calling task is possible.                                 */
/*                                                                       */
/* CALLED BY                                                             */
/*                                                                       */
/*      Application                                                      */
/*      MBCE_Receive_From_Mailbox           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 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 mailbox              */
/*      TCT_Unprotect                       Release protection           */
/*                                                                       */
/* INPUTS                                                                */
/*                                                                       */
/*      mailbox_ptr                         Mailbox control block pointer*/
/*      message                             Pointer to message to send   */
/*      suspend                             Suspension option if empty   */
/*                                                                       */
/* OUTPUTS                                                               */
/*                                                                       */
/*      NU_SUCCESS                          If service is successful     */
/*      NU_MAILBOX_EMPTY                    If mailbox is currently empty*/
/*      NU_TIMEOUT                          If timeout on service expires*/
/*      NU_MAILBOX_DELETED                  If mailbox is deleted during */
/*                                            suspension                 */
/*      NU_MAILBOX_RESET                    If mailbox is deleted during */
/*                                            suspension                 */
/*                                                                       */
/* HISTORY                                                               */
/*                                                                       */
/*         DATE                    REMARKS                               */
/*                                                                       */
/*      03-01-1993      Created initial version 1.0                      */
/*      04-19-1993      Verified version 1.0                             */
/*      03-01-1994      Changed function interface to                    */
/*                        match the prototype, added                     */
/*                        register variable logic,                       */
/*                        optimized protection logic,                    */
/*                        resulting in version 1.1                       */
/*                                                                       */
/*      03-18-1994      Verified version 1.1                             */
/*                                                                       */
/*************************************************************************/
STATUS  MBC_Receive_From_Mailbox(NU_MAILBOX *mailbox_ptr, VOID *message,
                                                        UNSIGNED suspend)
{

R1 MB_MCB      *mailbox;                    /* Mailbox control block ptr */
MB_SUSPEND      suspend_block;              /* Allocate suspension block */
R2 MB_SUSPEND  *suspend_ptr;                /* Pointer to suspend block  */
R3 UNSIGNED    *source_ptr;                 /* Pointer to source         */
R4 UNSIGNED    *destination_ptr;            /* Pointer to destination    */
TC_TCB         *task;                       /* Task pointer              */
STATUS          preempt;                    /* Preemption flag           */
STATUS          status;                     /* Completion status         */
NU_SUPERV_USER_VARIABLES

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

    /* Move input mailbox pointer into internal pointer.  */
    mailbox =  (MB_MCB *) mailbox_ptr;

#ifdef  NU_ENABLE_STACK_CHECK

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

#endif

#ifdef  NU_ENABLE_HISTORY