?? quc.c
字號(hào):
/* Decrement the number of available words. */
queue -> qu_available = queue -> qu_available - size;
/* Increment the number of messages in the queue. */
queue -> qu_messages++;
#ifdef INCLUDE_PROVIEW
_RTProf_DumpQueue(RT_PROF_SEND_TO_QUEUE,queue,RT_PROF_OK);
#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_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;
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