/***********************************************************************************************************                                                uC/OS-II*                                          The Real-Time Kernel*                                        MESSAGE QUEUE MANAGEMENT**                          (c) Copyright 1992-2001, 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 > 0void  *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();                     /* Get a free queue control block                     */        pq = OSQFreeList;        if (OSQFreeList != (OS_Q *)0) {            OSQFreeList = OSQFreeList->OSQPtr;        }        OS_EXIT_CRITICAL();        if (pq != (OS_Q *)0) {                   /* See if we were able to get a queue control block   */            pq->OSQStart        = start;         /* Yes, 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->OSEventPtr  = pq;            OS_EventWaitListInit(pevent);        } else {                                 /* No,  since we couldn't get a queue control block   */            OS_ENTER_CRITICAL();                 /* Return event control block on error                */            pevent->OSEventPtr = (void *)OSEventFreeList;            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 > 0OS_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: