os_q.c

完整的ucos实例

/* 
********************************************************************************************************* 
*                                                uC/OS-II 
*                                          The Real-Time Kernel 
*                                        MESSAGE QUEUE MANAGEMENT 
* 
*                          (c) Copyright 1992-2002, Jean J. Labrosse, Weston, FL 
*                                           All Rights Reserved 
* 
* File : OS_Q.C 
* By   : Jean J. Labrosse 
********************************************************************************************************* 
*/ 
 
#ifndef  OS_MASTER_FILE 
#include "includes.h" 
#endif 
 
#if (OS_Q_EN > 0) && (OS_MAX_QS > 0) 
/* 
********************************************************************************************************* 
*                                      ACCEPT MESSAGE FROM QUEUE 
* 
* Description: This function checks the queue to see if a message is available.  Unlike OSQPend(), 
*              OSQAccept() does not suspend the calling task if a message is not available. 
* 
* Arguments  : pevent        is a pointer to the event control block 
* 
* 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 the queue is empty or, 
*                            if 'pevent' is a NULL pointer or, 
*                            if you passed an invalid event type 
********************************************************************************************************* 
*/ 
 
#if OS_Q_ACCEPT_EN > 0 
void  *OSQAccept (OS_EVENT *pevent) 
{ 
#if OS_CRITICAL_METHOD == 3                      /* Allocate storage for CPU status register           */ 
    OS_CPU_SR  cpu_sr; 
#endif 
    void      *msg; 
    OS_Q      *pq; 
 
 
#if OS_ARG_CHK_EN > 0 
    if (pevent == (OS_EVENT *)0) {               /* Validate 'pevent'                                  */ 
        return ((void *)0); 
    } 
    if (pevent->OSEventType != OS_EVENT_TYPE_Q) {/* Validate event block type                          */ 
        return ((void *)0); 
    } 
#endif 
    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; 
        } 
    } else { 
        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) 
{ 
#if OS_CRITICAL_METHOD == 3                      /* Allocate storage for CPU status register           */ 
    OS_CPU_SR  cpu_sr; 
#endif 
    OS_EVENT  *pevent; 
    OS_Q      *pq; 
 
 
    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; 
            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) 
{ 
#if OS_CRITICAL_METHOD == 3                                /* Allocate storage for CPU status register */ 
    OS_CPU_SR  cpu_sr; 
#endif 
    BOOLEAN    tasks_waiting; 
    OS_Q      *pq; 
 
 
    if (OSIntNesting > 0) {                                /* See if called from ISR ...               */ 
        *err = OS_ERR_DEL_ISR;                             /* ... can't DELETE from an ISR             */ 
        return ((OS_EVENT *)0); 
    } 
#if OS_ARG_CHK_EN > 0 
    if (pevent == (OS_EVENT *)0) {                         /* Validate 'pevent'                        */ 
        *err = OS_ERR_PEVENT_NULL; 
        return (pevent); 
    } 
    if (pevent->OSEventType != OS_EVENT_TYPE_Q) {          /* Validate event block type                */ 
        *err = OS_ERR_EVENT_TYPE; 
        return (pevent); 
    } 
#endif 
    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) { 
                 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  */ 
                 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        */ 
                 OS_EventTaskRdy(pevent, (void *)0, OS_STAT_Q); 
             } 
             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  */ 
             OSEventFreeList     = pevent;                 /* Get next free event control block        */ 
             OS_EXIT_CRITICAL(); 
             if (tasks_waiting == TRUE) {                  /* Reschedule only if task(s) were waiting  */ 
                 OS_Sched();                               /* Find highest priority task ready to run  */ 
             } 
             *err = OS_NO_ERR; 
             return ((OS_EVENT *)0);                       /* Queue has been deleted                   */ 
 
        default: 
             OS_EXIT_CRITICAL();