pic.c

test file nucleus source

    /* Make an entry that corresponds to this function in the system history
       log.  */
    HIC_Make_History_Entry(NU_SEND_TO_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 make 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_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;

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

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

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

                CSC_Priority_Place_On_List((CS_NODE **)
                                &(pipe -> pi_suspension_list),
                                        &(suspend_ptr -> pi_suspend_link));
            }

            /* 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_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_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_write;

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

                /* Fixed-size messages are supported by this pipe.  */

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

                /* Variable-size messages are supported.  Processing must
                   check for pipe wrap-around conditions.  */

                /* Place message size in first location.  */
                *((UNSIGNED *) destination) =  size;
                destination =  destination + sizeof(UNSIGNED);

                /* Check for a wrap-around condition on the pipe.  */
                if (destination >= pipe -> pi_end)

                    /* Wrap the write pointer back to the top of the pipe
                       area.  */
                    destination =  pipe -> pi_start;

                /* Decrement the number of bytes remaining for this
                   extra word of overhead.  */
                pipe -> pi_available =  pipe -> pi_available -
                                                        sizeof(UNSIGNED);

                /* Calculate the number of bytes remaining from the write
                   pointer to the bottom of the pipe.  */
                copy_size =  pipe -> pi_end - destination;

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

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

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

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

            /* Check again for wrap-around condition on the write pointer. */
            if (destination >= pipe -> pi_end)

                /* Move the write pointer to the top of the pipe area.  */
                destination =  pipe -> pi_start;

            /* Determine if the pipe supports variable-length messages.  If
               so, pad bytes are needed to keep UNSIGNED alignment.  */
            if (pad)
            {

                /* Variable-size message.  Add pad bytes to the write
                   pointer.  */

                /* Calculate the number of bytes remaining from the write
                   pointer to the bottom of the pipe.  */
                copy_size =  pipe -> pi_end - destination;

                /* If there is not enough room at the bottom of the pipe, the
                   pad bytes must be wrapped around to the top.  */
                if (copy_size <= pad)

                    /* Move write pointer to the top of the pipe and make the
                       necessary adjustment.  */