pis.c

test file nucleus source

/*      PISE_Send_To_Front_Of_Pipe          Error checking shell         */
/*                                                                       */
/* CALLS                                                                 */
/*                                                                       */
/*      CSC_Place_On_List                   Place on suspend 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         */
/*      [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 pipe                 */
/*      TCT_Unprotect                       Release protection           */
/*                                                                       */
/* INPUTS                                                                */
/*                                                                       */
/*      pipe_ptr                            Pipe control block pointer   */
/*      message                             Pointer to message to send   */
/*      size                                Size of message to send      */
/*      suspend                             Suspension option if full    */
/*                                                                       */
/* OUTPUTS                                                               */
/*                                                                       */
/*      NU_SUCCESS                          If service is successful     */
/*      NU_PIPE_FULL                        If pipe is currently full    */
/*      NU_TIMEOUT                          If timeout on service expires*/
/*      NU_PIPE_DELETED                     If pipe was deleted during   */
/*                                            suspension                 */
/*      NU_PIPE_RESET                       If pipe was reset 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 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                             */
/*                                                                       */
/*************************************************************************/
STATUS  PIS_Send_To_Front_Of_Pipe(NU_PIPE *pipe_ptr, VOID *message,
                                        UNSIGNED size, UNSIGNED suspend)
{

R1 PI_PCB      *pipe;                       /* Pipe control block ptr    */
PI_SUSPEND      suspend_block;              /* Allocate suspension block */
PI_SUSPEND     *suspend_ptr;                /* Pointer to suspend block  */
R2 BYTE_PTR     source;                     /* Pointer to source         */
R3 BYTE_PTR     destination;                /* Pointer to destination    */
UNSIGNED        copy_size;                  /* Partial copy size         */
R4 INT          i;                          /* Working counter           */
UNSIGNED        pad = 0;                    /* Number of pad bytes       */
TC_TCB         *task;                       /* Task pointer              */
STATUS          preempt;                    /* Preempt flag              */
STATUS          status;                     /* Completion status         */
NU_SUPERV_USER_VARIABLES

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

    /* Move input pipe pointer into internal pointer.  */
    pipe =  (PI_PCB *) pipe_ptr;


#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_SEND_TO_FRONT_OF_PIPE_ID, (UNSIGNED) pipe,
                                        (UNSIGNED) message, (UNSIGNED) size);

#endif

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

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

    /* Determine if an extra word of overhead needs to be added to the
       calculation.  */
    if (pipe -> pi_fixed_size)

        /* No overhead.  */
        i =  0;
    else
    {

        /* Variable messages have one additional word of overhead.  */
        i =  sizeof(UNSIGNED);

        /* Calculate the number of pad bytes necessary to keep the pipe
           write pointer on an UNSIGNED data element alignment.  */
        pad =  (((size + sizeof(UNSIGNED) - 1)/sizeof(UNSIGNED)) *
                        sizeof(UNSIGNED)) - size;

        /* Insure that padding is included in the overhead.  */
        i =  i + ((INT) pad);

        /* Make special check to see if a suspension needs to be
           forced for a variable length message.  */
        if ((pipe -> pi_suspension_list) && (pipe -> pi_messages))
        {

            /* Pickup task control block pointer.  */
            task =  (TC_TCB *) TCT_Current_Thread();

            /* Now we know that there are other task(s) are suspended trying
               to send a variable length message.  Determine whether or not
               a suspension should be forced.  */
            if ((pipe -> pi_fifo_suspend) ||
                (suspend == NU_NO_SUSPEND) ||
                ((pipe -> pi_suspension_list) -> pi_suspend_link.cs_priority <=
                                                    TCC_Task_Priority(task)))

                /* Bump the computed size to avoid placing the new variable
                   length message ahead of the suspended tasks.  */
                i =  (INT) pipe -> pi_available;
        }
    }

    /* Determine if there is enough room in the pipe for the message.  */
    if (pipe -> pi_available < (size + i))
    {

        /* pipe does not have room for the message.  Determine if
           suspension is required.  */
        if (suspend)
        {

            /* Suspension is requested.   */

            /* Increment the number of tasks waiting.  */
            pipe -> pi_tasks_waiting++;

#ifdef INCLUDE_PROVIEW
            _RTProf_DumpPipe(RT_PROF_SEND_TO_FRONT_OF_PIPE,pipe,RT_PROF_WAIT);
#endif /* INCLUDE_PROVIEW */

            /* Setup the suspend block and suspend the calling task.  */
            suspend_ptr =  &suspend_block;
            suspend_ptr -> pi_pipe =                     pipe;
            suspend_ptr -> pi_suspend_link.cs_next =     NU_NULL;
            suspend_ptr -> pi_suspend_link.cs_previous = NU_NULL;
            suspend_ptr -> pi_message_area =       (BYTE_PTR) message;
            suspend_ptr -> pi_message_size =             size;
            task =                            (TC_TCB *) TCT_Current_Thread();
            suspend_ptr -> pi_suspended_task =           task;

            /* Place the task on the urgent message suspension list.  */
            CSC_Place_On_List((CS_NODE **) &(pipe -> pi_urgent_list),
                                        &(suspend_ptr -> pi_suspend_link));

            /* Move the head pointer of the list to make this suspension the
               first in the list.  */
            pipe -> pi_urgent_list =  (PI_SUSPEND *)
                (pipe -> pi_urgent_list) -> pi_suspend_link.cs_previous;

            /* Finally, suspend the calling task. Note that the suspension call
               automatically clears the protection on the pipe.  */
            TCC_Suspend_Task((NU_TASK *) task, NU_PIPE_SUSPEND,
                                        PIC_Cleanup, suspend_ptr, suspend);

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

            /* Return a status of NU_PIPE_FULL because there is no
               room in the pipe for the message.  */
            status =  NU_PIPE_FULL;

#ifdef INCLUDE_PROVIEW
            _RTProf_DumpPipe(RT_PROF_SEND_TO_FRONT_OF_PIPE,pipe,RT_PROF_FAIL);
#endif /* INCLUDE_PROVIEW */

        }
    }
    else
    {

        /* Determine if a task is waiting on an empty pipe.  */
        if ((pipe -> pi_suspension_list) && (pipe -> pi_messages == 0))
        {

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

            /* Decrement the number of tasks waiting on pipe.  */
            pipe -> pi_tasks_waiting--;

#ifdef INCLUDE_PROVIEW
        _RTProf_DumpPipe(RT_PROF_SEND_TO_FRONT_OF_PIPE,pipe,RT_PROF_OK);
#endif /* INCLUDE_PROVIEW */

            /* Remove the first suspended block from the list.  */
            suspend_ptr =  pipe -> pi_suspension_list;
            CSC_Remove_From_List((CS_NODE **) &(pipe -> pi_suspension_list),
                                          &(suspend_ptr -> pi_suspend_link));

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

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

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

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

            /* Wakeup the waiting task and check for preemption.  */
            preempt =
                TCC_Resume_Task((NU_TASK *) suspend_ptr -> pi_suspended_task,
                                                     NU_PIPE_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
        {

            /* There is enough room in the pipe and no task is waiting.  */

            /* Setup the source pointer.  */
            source =       (BYTE_PTR) message;
            destination =  pipe -> pi_read;

            /* Process according to the type of message supported.  */
            if (pipe -> pi_fixed_size)
            {

                /* Fixed-size message pipe.  */

                /* Determine if the read pointer is at the top of the pipe
                   area.  */
                if (destination == pipe -> pi_start)

                    /* Prepare to place the message in the lower part of the
                       pipe area.  */
                    destination =  pipe -> pi_end - size;
                else

                    /* Backup the length of the message from the current
                       read pointer.  */
                    destination =  destination - size;

                /* Adjust the actual read pointer before the copy is done.  */
                pipe -> pi_read =  destination;

                /* Copy the message into the pipe area.  */
                i =  (INT) size;
                do
                {
                    *(destination++) =  *(source);