*                           }
*
*              ptos     is a pointer to the task's top of stack.  If the configuration constant 
*                       OS_STK_GROWTH is set to 1, the stack is assumed to grow downward (i.e. from high
*                       memory to low memory).  'pstk' will thus point to the highest (valid) memory 
*                       location of the stack.  If OS_STK_GROWTH is set to 0, 'pstk' will point to the 
*                       lowest memory location of the stack and the stack will grow with increasing
*                       memory locations.  'pstk' MUST point to a valid 'free' data item.
*
*              prio     is the task's priority.  A unique priority MUST be assigned to each task and the
*                       lower the number, the higher the priority.
*
*              id       is the task's ID (0..65535)
*
*              pbos     is a pointer to the task's bottom of stack.  If the configuration constant 
*                       OS_STK_GROWTH is set to 1, the stack is assumed to grow downward (i.e. from high
*                       memory to low memory).  'pbos' will thus point to the LOWEST (valid) memory 
*                       location of the stack.  If OS_STK_GROWTH is set to 0, 'pbos' will point to the 
*                       HIGHEST memory location of the stack and the stack will grow with increasing
*                       memory locations.  'pbos' MUST point to a valid 'free' data item.
*
*              stk_size is the size of the stack in number of elements.  If OS_STK is set to INT8U,
*                       'stk_size' corresponds to the number of bytes available.  If OS_STK is set to
*                       INT16U, 'stk_size' contains the number of 16-bit entries available.  Finally, if
*                       OS_STK is set to INT32U, 'stk_size' contains the number of 32-bit entries
*                       available on the stack.
*
*              pext     is a pointer to a user supplied memory location which is used as a TCB extension.
*                       For example, this user memory can hold the contents of floating-point registers
*                       during a context switch, the time each task takes to execute, the number of times
*                       the task has been switched-in, etc. 
*
*              opt      contains additional information (or options) about the behavior of the task.  The 
*                       LOWER 8-bits are reserved by uC/OS-II while the upper 8 bits can be application 
*                       specific.  See OS_TASK_OPT_??? in uCOS-II.H.
*
* Returns    : OS_NO_ERR        if the function was successful.
*              OS_PRIO_EXIT     if the task priority already exist 
*                               (each task MUST have a unique priority).
*              OS_PRIO_INVALID  if the priority you specify is higher that the maximum allowed 
*                               (i.e. > OS_LOWEST_PRIO)
*********************************************************************************************************
*/
/*$PAGE*/
#if   OS_TASK_CREATE_EXT_EN    
INT8U OSTaskCreateExt (void   (*task)(void *pd), 
                       void    *pdata, 
                       OS_STK  *ptos, 
                       INT8U    prio,
                       INT16U   id,
                       OS_STK  *pbos,
                       INT32U   stk_size,
                       void    *pext,
                       INT16U   opt)
{
    void    *psp;
    INT8U    err;
    INT16U   i;
    OS_STK  *pfill;


    if (prio > OS_LOWEST_PRIO) {             /* Make sure priority is within allowable range           */
        return (OS_PRIO_INVALID);
    }
    OS_ENTER_CRITICAL();
    if (OSTCBPrioTbl[prio] == (OS_TCB *)0) { /* Make sure task doesn't already exist at this priority  */
        OSTCBPrioTbl[prio] = (OS_TCB *)1;    /* Reserve the priority to prevent others from doing ...  */
                                             /* ... the same thing until task is created.              */
        OS_EXIT_CRITICAL();
        
        if (opt & OS_TASK_OPT_STK_CHK) {     /* See if stack checking has been enabled                 */
            if (opt & OS_TASK_OPT_STK_CLR) { /* See if stack needs to be cleared                       */
                pfill = pbos;                /* Yes, fill the stack with zeros                         */
                for (i = 0; i < stk_size; i++) {
                    #if OS_STK_GROWTH == 1
                    *pfill++ = (OS_STK)0;
                    #else
                    *pfill-- = (OS_STK)0;
                    #endif
                }
            }
        }
        
        psp = (void *)OSTaskStkInit(task, pdata, ptos, opt); /* Initialize the task's stack            */
        err = OSTCBInit(prio, psp, pbos, id, stk_size, pext, opt);         
        if (err == OS_NO_ERR) {
            OS_ENTER_CRITICAL();
            OSTaskCtr++;                                     /* Increment the #tasks counter           */
            OSTaskCreateHook(OSTCBPrioTbl[prio]);            /* Call user defined hook                 */
            OS_EXIT_CRITICAL();
            if (OSRunning) {                 /* Find highest priority task if multitasking has started */
                OSSched();
            }
        } else {
            OS_ENTER_CRITICAL();
            OSTCBPrioTbl[prio] = (OS_TCB *)0;/* Make this priority available to others                 */
            OS_EXIT_CRITICAL();
        }
        return (err);
    } else {
        OS_EXIT_CRITICAL();
        return (OS_PRIO_EXIST);
    }
}
#endif
/*$PAGE*/
/*
*********************************************************************************************************
*                                            DELETE A TASK
*
* Description: This function allows you to delete a task.  The calling task can delete itself by 
*              its own priority number.  The deleted task is returned to the dormant state and can be
*              re-activated by creating the deleted task again.
*
* Arguments  : prio    is the priority of the task to delete.  Note that you can explicitely delete
*                      the current task without knowing its priority level by setting 'prio' to
*                      OS_PRIO_SELF.
*
* Returns    : OS_NO_ERR           if the call is successful
*              OS_TASK_DEL_IDLE    if you attempted to delete uC/OS-II's idle task
*              OS_PRIO_INVALID     if the priority you specify is higher that the maximum allowed 
*                                  (i.e. >= OS_LOWEST_PRIO) or, you have not specified OS_PRIO_SELF.
*              OS_TASK_DEL_ERR     if the task you want to delete does not exist
*              OS_TASK_DEL_ISR     if you tried to delete a task from an ISR
*
* Notes      : 1) To reduce interrupt latency, OSTaskDel() 'disables' the task:
*                    a) by making it not ready
*                    b) by removing it from any wait lists
*                    c) by preventing OSTimeTick() from making the task ready to run.
*                 The task can then be 'unlinked' from the miscellaneous structures in uC/OS-II.
*              2) The function OSDummy() is called after OS_EXIT_CRITICAL() because, on most processors, 
*                 the next instruction following the enable interrupt instruction is ignored.  You can 
*                 replace OSDummy() with a macro that basically executes a NO OP (i.e. OS_NOP()).  The 
*                 NO OP macro would avoid the execution time of the function call and return.
*              3) An ISR cannot delete a task.
*              4) The lock nesting counter is incremented because, for a brief instant, if the current
*                 task is being deleted, the current task would not be able to be rescheduled because it
*                 is removed from the ready list.  Incrementing the nesting counter prevents another task
*                 from being schedule.  This means that the ISR would return to the current task which is
*                 being deleted.  The rest of the deletion would thus be able to be completed.
*********************************************************************************************************
*/
/*$PAGE*/
#if OS_TASK_DEL_EN
INT8U OSTaskDel (INT8U prio)
{
    OS_TCB   *ptcb;
    OS_EVENT *pevent;


    if (prio == OS_IDLE_PRIO) {                                 /* Not allowed to delete idle task     */
        return (OS_TASK_DEL_IDLE);
    }
    if (prio >= OS_LOWEST_PRIO && prio != OS_PRIO_SELF) {       /* Task priority valid ?               */
        return (OS_PRIO_INVALID);
    }
    OS_ENTER_CRITICAL();
    if (OSIntNesting > 0) {                                     /* See if trying to delete from ISR    */
        OS_EXIT_CRITICAL();
        return (OS_TASK_DEL_ISR);
    }
    if (prio == OS_PRIO_SELF) {                                 /* See if requesting to delete self    */
        prio = OSTCBCur->OSTCBPrio;                             /* Set priority to delete to current   */
    }
    if ((ptcb = OSTCBPrioTbl[prio]) != (OS_TCB *)0) {           /* Task to delete must exist           */
        if ((OSRdyTbl[ptcb->OSTCBY] &= ~ptcb->OSTCBBitX) == 0) {/* Make task not ready                 */
            OSRdyGrp &= ~ptcb->OSTCBBitY;
        }
        if ((pevent = ptcb->OSTCBEventPtr) != (OS_EVENT *)0) {  /* If task is waiting on event         */
            if ((pevent->OSEventTbl[ptcb->OSTCBY] &= ~ptcb->OSTCBBitX) == 0) { /* ... remove task from */
                pevent->OSEventGrp &= ~ptcb->OSTCBBitY;                        /* ... event ctrl block */
            }
        }
        ptcb->OSTCBDly  = 0;                                    /* Prevent OSTimeTick() from updating  */
        ptcb->OSTCBStat = OS_STAT_RDY;                          /* Prevent task from being resumed     */
        OSLockNesting++;
        OS_EXIT_CRITICAL();                                     /* Enabling INT. ignores next instruc. */
        OSDummy();                                              /* ... Dummy ensures that INTs will be */
        OS_ENTER_CRITICAL();                                    /* ... disabled HERE!                  */
        OSLockNesting--;
        OSTaskDelHook(ptcb);                                    /* Call user defined hook              */
        OSTaskCtr--;                                            /* One less task being managed         */
        OSTCBPrioTbl[prio] = (OS_TCB *)0;                       /* Clear old priority entry            */
        if (ptcb->OSTCBPrev == (OS_TCB *)0) {                   /* Remove from TCB chain               */
            ptcb->OSTCBNext->OSTCBPrev = (OS_TCB *)0;
            OSTCBList                  = ptcb->OSTCBNext;
        } else {
            ptcb->OSTCBPrev->OSTCBNext = ptcb->OSTCBNext;
            ptcb->OSTCBNext->OSTCBPrev = ptcb->OSTCBPrev;
        }
        ptcb->OSTCBNext = OSTCBFreeList;                        /* Return TCB to free TCB list         */
        OSTCBFreeList   = ptcb;
        OS_EXIT_CRITICAL();
        OSSched();                                              /* Find new highest priority task      */
        return (OS_NO_ERR);
    } else {
        OS_EXIT_CRITICAL();
        return (OS_TASK_DEL_ERR);
    }
}
#endif
/*$PAGE*/
/*
*********************************************************************************************************
*                                    REQUEST THAT A TASK DELETE ITSELF
*
* Description: This function is used to:
*                   a) notify a task to delete itself.
*                   b) to see if a task requested that the current task delete itself.
*              This function is a little tricky to understand.  Basically, you have a task that needs
*              to be deleted however, this task has resources that it has allocated (memory buffers,
*              semaphores, mailboxes, queues etc.).  The task cannot be deleted otherwise these
*              resources would not be freed.  The requesting task calls OSTaskDelReq() to indicate that
*              the task needs to be deleted.  Deleting of the task is however, deferred to the task to
*              be deleted.  For example, suppose that task #10 needs to be deleted.  The requesting task
*              example, task #5, would call OSTaskDelReq(10).  When task #10 gets to execute, it calls
*              this function by specifying OS_PRIO_SELF and monitors the returned value.  If the return
*              value is OS_TASK_DEL_REQ, another task requested a task delete.  Task #10 would look like
*              this:
*
*                   void Task(void *data)
*                   {
*                       .
*                       .
*                       while (1) {
*                           OSTimeDly(1);
*                           if (OSTaskDelReq(OS_PRIO_SELF) == OS_TASK_DEL_REQ) {
*                               Release any owned resources;
*                               De-allocate any dynamic memory;
*                               OSTaskDel(OS_PRIO_SELF);
*                           }
*                       }
*                   }
*
* Arguments  : prio    is the priority of the task to request the delete from
*
* Returns    : OS_NO_ERR          if the task exist and the request has been registered
*              OS_TASK_NOT_EXIST  if the task has been deleted.  This allows the caller to know whether
*                                 the request has been executed.
*              OS_TASK_DEL_IDLE   if you requested to delete uC/OS-II's idle task
*              OS_PRIO_INVALID    if the priority you specify is higher that the maximum allowed 
*                                 (i.e. >= OS_LOWEST_PRIO) or, you have not specified OS_PRIO_SELF.
*              OS_TASK_DEL_REQ    if a task (possibly another task) requested that the running task be 
*                                 deleted.
*********************************************************************************************************
*/