?? os_q.c
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/*
*********************************************************************************************************
* uC/OS-II
* The Real-Time Kernel
* MESSAGE QUEUE MANAGEMENT
*
* (c) Copyright 1992-2003, Jean J. Labrosse, Weston, FL
* All Rights Reserved
*
* File : OS_Q.C
* By : Jean J. Labrosse
* Version : V2.76
*********************************************************************************************************
*/
#ifndef OS_MASTER_FILE
#include <ucos_ii.h>
#endif
#if (OS_Q_EN > 0) && (OS_MAX_QS > 0)
/*
*********************************************************************************************************
* ACCEPT MESSAGE FROM QUEUE
*
* OSQAccept() does not suspend the calling task if a message is not available.
*
* Arguments : pevent is a pointer to the event control block
*
* err is a pointer to where an error message will be deposited. Possible error
* messages are:
*
* OS_NO_ERR The call was successful and your task received a
* message.
* OS_ERR_EVENT_TYPE You didn't pass a pointer to a queue
* OS_ERR_PEVENT_NULL If 'pevent' is a NULL pointer
* OS_Q_EMPTY The queue did not contain any messages
*
* Returns : != (void *)0 is the message in the queue if one is available. The message is removed
* from the so the next time OSQAccept() is called, the queue will contain
* one less entry.
* == (void *)0 if you received a NULL pointer message
* if the queue is empty or,
* if 'pevent' is a NULL pointer or,
* if you passed an invalid event type
*
* Note(s) : As of V2.60, you can now pass NULL pointers through queues. Because of this, the argument
* 'err' has been added to the API to tell you about the outcome of the call.
*********************************************************************************************************
*/
#if OS_Q_ACCEPT_EN > 0
void *OSQAccept (OS_EVENT *pevent, INT8U *err)
{
void *msg;
OS_Q *pq;
#if OS_CRITICAL_METHOD == 3 /* Allocate storage for CPU status register */
OS_CPU_SR cpu_sr;
cpu_sr = 0; /* Prevent compiler warning */
#endif
#if OS_ARG_CHK_EN > 0
if (pevent == (OS_EVENT *)0) { /* Validate 'pevent' */
*err = OS_ERR_PEVENT_NULL;
return ((void *)0);
}
#endif
if (pevent->OSEventType != OS_EVENT_TYPE_Q) {/* Validate event block type */
*err = OS_ERR_EVENT_TYPE;
return ((void *)0);
}
OS_ENTER_CRITICAL();
pq = (OS_Q *)pevent->OSEventPtr; /* Point at queue control block */
if (pq->OSQEntries > 0) { /* See if any messages in the queue */
msg = *pq->OSQOut++; /* Yes, extract oldest message from the queue */
pq->OSQEntries--; /* Update the number of entries in the queue */
if (pq->OSQOut == pq->OSQEnd) { /* Wrap OUT pointer if we are at the end of the queue */
pq->OSQOut = pq->OSQStart;
}
*err = OS_NO_ERR;
} else {
*err = OS_Q_EMPTY;
msg = (void *)0; /* Queue is empty */
}
OS_EXIT_CRITICAL();
return (msg); /* Return message received (or NULL) */
}
#endif
/*$PAGE*/
/*
*********************************************************************************************************
* CREATE A MESSAGE QUEUE
*
* Description: This function creates a message queue if free event control blocks are available.
*
* Arguments : start is a pointer to the base address of the message queue storage area. The
* storage area MUST be declared as an array of pointers to 'void' as follows
*
* void *MessageStorage[size]
*
* size is the number of elements in the storage area
*
* Returns : != (OS_EVENT *)0 is a pointer to the event control clock (OS_EVENT) associated with the
* created queue
* == (OS_EVENT *)0 if no event control blocks were available or an error was detected
*********************************************************************************************************
*/
OS_EVENT *OSQCreate (void **start, INT16U size)
{
OS_EVENT *pevent;
OS_Q *pq;
#if OS_CRITICAL_METHOD == 3 /* Allocate storage for CPU status register */
OS_CPU_SR cpu_sr;
cpu_sr = 0; /* Prevent compiler warning */
#endif
if (OSIntNesting > 0) { /* See if called from ISR ... */
return ((OS_EVENT *)0); /* ... can't CREATE from an ISR */
}
OS_ENTER_CRITICAL();
pevent = OSEventFreeList; /* Get next free event control block */
if (OSEventFreeList != (OS_EVENT *)0) { /* See if pool of free ECB pool was empty */
OSEventFreeList = (OS_EVENT *)OSEventFreeList->OSEventPtr;
}
OS_EXIT_CRITICAL();
if (pevent != (OS_EVENT *)0) { /* See if we have an event control block */
OS_ENTER_CRITICAL();
pq = OSQFreeList; /* Get a free queue control block */
if (pq != (OS_Q *)0) { /* Were we able to get a queue control block ? */
OSQFreeList = OSQFreeList->OSQPtr; /* Yes, Adjust free list pointer to next free*/
OS_EXIT_CRITICAL();
pq->OSQStart = start; /* Initialize the queue */
pq->OSQEnd = &start[size];
pq->OSQIn = start;
pq->OSQOut = start;
pq->OSQSize = size;
pq->OSQEntries = 0;
pevent->OSEventType = OS_EVENT_TYPE_Q;
pevent->OSEventCnt = 0;
pevent->OSEventPtr = pq;
#if OS_EVENT_NAME_SIZE > 1
pevent->OSEventName[0] = '?'; /* Unknown name */
pevent->OSEventName[1] = OS_ASCII_NUL;
#endif
OS_EventWaitListInit(pevent); /* Initalize the wait list */
} else {
pevent->OSEventPtr = (void *)OSEventFreeList; /* No, Return event control block on error */
OSEventFreeList = pevent;
OS_EXIT_CRITICAL();
pevent = (OS_EVENT *)0;
}
}
return (pevent);
}
/*$PAGE*/
/*
*********************************************************************************************************
* DELETE A MESSAGE QUEUE
*
* Description: This function deletes a message queue and readies all tasks pending on the queue.
*
* Arguments : pevent is a pointer to the event control block associated with the desired
* queue.
*
* opt determines delete options as follows:
* opt == OS_DEL_NO_PEND Delete the queue ONLY if no task pending
* opt == OS_DEL_ALWAYS Deletes the queue even if tasks are waiting.
* In this case, all the tasks pending will be readied.
*
* err is a pointer to an error code that can contain one of the following values:
* OS_NO_ERR The call was successful and the queue was deleted
* OS_ERR_DEL_ISR If you tried to delete the queue from an ISR
* OS_ERR_INVALID_OPT An invalid option was specified
* OS_ERR_TASK_WAITING One or more tasks were waiting on the queue
* OS_ERR_EVENT_TYPE If you didn't pass a pointer to a queue
* OS_ERR_PEVENT_NULL If 'pevent' is a NULL pointer.
*
* Returns : pevent upon error
* (OS_EVENT *)0 if the queue was successfully deleted.
*
* Note(s) : 1) This function must be used with care. Tasks that would normally expect the presence of
* the queue MUST check the return code of OSQPend().
* 2) OSQAccept() callers will not know that the intended queue has been deleted unless
* they check 'pevent' to see that it's a NULL pointer.
* 3) This call can potentially disable interrupts for a long time. The interrupt disable
* time is directly proportional to the number of tasks waiting on the queue.
* 4) Because ALL tasks pending on the queue will be readied, you MUST be careful in
* applications where the queue is used for mutual exclusion because the resource(s)
* will no longer be guarded by the queue.
* 5) If the storage for the message queue was allocated dynamically (i.e. using a malloc()
* type call) then your application MUST release the memory storage by call the counterpart
* call of the dynamic allocation scheme used. If the queue storage was created statically
* then, the storage can be reused.
*********************************************************************************************************
*/
#if OS_Q_DEL_EN > 0
OS_EVENT *OSQDel (OS_EVENT *pevent, INT8U opt, INT8U *err)
{
BOOLEAN tasks_waiting;
OS_Q *pq;
#if OS_CRITICAL_METHOD == 3 /* Allocate storage for CPU status register */
OS_CPU_SR cpu_sr;
cpu_sr = 0; /* Prevent compiler warning */
#endif
if (OSIntNesting > 0) { /* See if called from ISR ... */
*err = OS_ERR_DEL_ISR; /* ... can't DELETE from an ISR */
return (pevent);
}
#if OS_ARG_CHK_EN > 0
if (pevent == (OS_EVENT *)0) { /* Validate 'pevent' */
*err = OS_ERR_PEVENT_NULL;
return (pevent);
}
#endif
if (pevent->OSEventType != OS_EVENT_TYPE_Q) { /* Validate event block type */
*err = OS_ERR_EVENT_TYPE;
return (pevent);
}
OS_ENTER_CRITICAL();
if (pevent->OSEventGrp != 0x00) { /* See if any tasks waiting on queue */
tasks_waiting = TRUE; /* Yes */
} else {
tasks_waiting = FALSE; /* No */
}
switch (opt) {
case OS_DEL_NO_PEND: /* Delete queue only if no task waiting */
if (tasks_waiting == FALSE) {
#if OS_EVENT_NAME_SIZE > 1
pevent->OSEventName[0] = '?'; /* Unknown name */
pevent->OSEventName[1] = OS_ASCII_NUL;
#endif
pq = (OS_Q *)pevent->OSEventPtr; /* Return OS_Q to free list */
pq->OSQPtr = OSQFreeList;
OSQFreeList = pq;
pevent->OSEventType = OS_EVENT_TYPE_UNUSED;
pevent->OSEventPtr = OSEventFreeList; /* Return Event Control Block to free list */
pevent->OSEventCnt = 0;
OSEventFreeList = pevent; /* Get next free event control block */
OS_EXIT_CRITICAL();
*err = OS_NO_ERR;
return ((OS_EVENT *)0); /* Queue has been deleted */
} else {
OS_EXIT_CRITICAL();
*err = OS_ERR_TASK_WAITING;
return (pevent);
}
case OS_DEL_ALWAYS: /* Always delete the queue */
while (pevent->OSEventGrp != 0x00) { /* Ready ALL tasks waiting for queue */
(void)OS_EventTaskRdy(pevent, (void *)0, OS_STAT_Q);
}
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