?? quc.c
字號(hào):
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);
#endif
/* Determine if any tasks suspended on a full queue can be woken
up. */
if (queue -> qu_suspension_list)
{
/* Overhead of each queue message. */
if (!queue -> qu_fixed_size)
i = 1;
else
i = 0;
/* Pickup the suspension list and examine suspension blocks
to see if the message could now fit in the queue. */
suspend_ptr = queue -> qu_suspension_list;
preempt = NU_FALSE;
while ((suspend_ptr) &&
((suspend_ptr -> qu_message_size + i) <= queue -> qu_available))
{
/* Place the suspended task's message into the queue. */
/* Setup the source and destination pointers. */
source = suspend_ptr -> qu_message_area;
destination = queue -> qu_write;
size = suspend_ptr -> qu_message_size;
/* Process according to the type of message supported. */
if (queue -> qu_fixed_size)
{
/* Fixed-size messages are supported by this queue. */
/* Loop to copy the message into the queue area. */
i = (INT) size;
do
{
*(destination++) = *(source);
if ((--i) == 0)
break;
source++;
} while (1);
}
else
{
/* Variable-size messages are supported. Processing must
check for queue wrap-around conditions. */
/* Place message size in first location. */
*(destination++) = size;
/* Check for a wrap-around condition on the queue. */
if (destination >= queue -> qu_end)
/* Wrap the write pointer back to the top of the queue
area. */
destination = queue -> qu_start;
/* Decrement the number of words remaining by 1 for this
extra word of overhead. */
queue -> qu_available--;
/* Calculate the number of words remaining from the write
pointer to the bottom of the queue. */
copy_size = queue -> qu_end - destination;
/* 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;
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 = queue -> qu_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 >= queue -> qu_end)
/* Move the write pointer to the top of the queue area. */
queue -> qu_write = queue -> qu_start;
else
/* Simply copy the last position of the destination pointer
into the write pointer. */
queue -> qu_write = destination;
/* Decrement the number of available words. */
queue -> qu_available = queue -> qu_available - size;
/* Increment the number of messages in the queue. */
queue -> qu_messages++;
/* Decrement the number of tasks waiting counter. */
queue -> qu_tasks_waiting--;
/* Remove the first suspended block from the list. */
CSC_Remove_From_List((CS_NODE **)
&(queue -> qu_suspension_list),
&(suspend_ptr -> qu_suspend_link));
/* Return a successful status. */
suspend_ptr -> qu_return_status = NU_SUCCESS;
/* Resume the suspended task. */
preempt = preempt |
TCC_Resume_Task((NU_TASK *) suspend_ptr -> qu_suspended_task,
NU_QUEUE_SUSPEND);
/* Setup suspend pointer to the head of the list. */
suspend_ptr = queue -> qu_suspension_list;
/* Overhead of each queue message. */
if (!queue -> qu_fixed_size)
i = 1;
else
i = 0;
}
/* Determine if a preempt condition is present. */
if (preempt)
/* Transfer control to the system if the resumed task function
detects a preemption condition. */
TCT_Control_To_System();
}
}
else
{
/* Queue is empty. Determine if the task wants to suspend. */
if (suspend)
{
/* Increment the number of tasks waiting on the queue counter. */
queue -> qu_tasks_waiting++;
#ifdef INCLUDE_PROVIEW
_RTProf_DumpQueue(RT_PROF_RECEIVE_FROM_QUEUE,queue,RT_PROF_WAIT);
#endif
/* Setup the suspend block and suspend the calling task. */
suspend_ptr = &suspend_block;
suspend_ptr -> qu_queue = queue;
suspend_ptr -> qu_suspend_link.cs_next = NU_NULL;
suspend_ptr -> qu_suspend_link.cs_previous = NU_NULL;
suspend_ptr -> qu_message_area = (UNSIGNED_PTR) message;
suspend_ptr -> qu_message_size = size;
task = (TC_TCB *) TCT_Current_Thread();
suspend_ptr -> qu_suspended_task = task;
/* Determine if priority or FIFO suspension is associated with the
queue. */
if (queue -> qu_fifo_suspend)
{
/* FIFO suspension is required. Link the suspend block into
the list of suspended tasks on this queue. */
CSC_Place_On_List((CS_NODE **) &(queue -> qu_suspension_list),
&(suspend_ptr -> qu_suspend_link));
}
else
{
/* Get the priority of the current thread so the suspend block
can be placed in the appropriate place. */
suspend_ptr -> qu_suspend_link.cs_priority =
TCC_Task_Priority(task);
CSC_Priority_Place_On_List((CS_NODE **)
&(queue -> qu_suspension_list),
&(suspend_ptr -> qu_suspend_link));
}
/* Finally, suspend the calling task. Note that the suspension call
automatically clears the protection on the queue. */
TCC_Suspend_Task((NU_TASK *) task, NU_QUEUE_SUSPEND,
QUC_Cleanup, suspend_ptr, suspend);
/* Pickup the status of the request. */
status = suspend_ptr -> qu_return_status;
*actual_size = suspend_ptr -> qu_actual_size;
}
else
{
/* Return a status of NU_QUEUE_EMPTY because there are no
messages in the queue. */
status = NU_QUEUE_EMPTY;
#ifdef INCLUDE_PROVIEW
_RTProf_DumpQueue(RT_PROF_RECEIVE_FROM_QUEUE,queue,RT_PROF_FAIL);
#endif
}
}
/* Release protection against access to the queue. */
TCT_Unprotect();
/* Return to user mode */
NU_USER_MODE();
/* Return the completion status. */
return(status);
}
/*************************************************************************/
/* */
/* FUNCTION */
/* */
/* QUC_Cleanup */
/* */
/* DESCRIPTION */
/* */
/* This function is responsible for removing a suspension block */
/* from a queue. It is not called unless a timeout or a task */
/* terminate is in progress. Note that protection is already in */
/* effect - the same protection at suspension time. This routine */
/* must be called from Supervisor mode in Supervisor/User mode */
/* switching kernels. */
/* */
/* CALLED BY */
/* */
/* TCC_Timeout Task timeout */
/* TCC_Terminate Task terminate */
/* */
/* CALLS */
/* */
/* CSC_Remove_From_List Remove suspend block from */?? 快捷鍵說(shuō)明
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