os_core/os_flag.c

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/***********************************
* Operation System Kernel File
* function: flag event handler
* 
* File:   os_flag.c
* Author: Book Chen
* Date: 2008.07.18
************************************
*/
#include "includes.h"

void OsFlagInit(void);
OS_EVENT *OsFlagCreat(void);
INT8U OsFlagDelete(OS_EVENT *pFlag);
INT16U OsFlagGet(OS_EVENT *pFlag); // 0 if no semaphore 
void OsFlagPending(OS_EVENT *pFlag,INT16U TimeOut,INT8U *Error);
INT8U OsFlagPost(OS_EVENT *pFlag);

void OsFlagInit(void){}
OS_EVENT *OsFlagCreat(void){
    OS_EVENT *pEvent;
        
    OS_ENTER_CRITICAL();
    pEvent=OsEventFreeEventGet();
    OS_EXIT_CRITICAL();
    if(pEvent!=(OS_EVENT *)0){ 
        pEvent->EventType=EVENT_TYPE_FLAG;
        pEvent->EventCounter=1; 
        pEvent->ListHead=(INT32U *)0;
        pEvent->EntryNumber=0;
        pEvent->Prev=(struct os_event *)0;
        pEvent->Next=(struct os_event *)0;
        OsTimeEventListPut(pEvent); // hook event to timer event list
    }
    return pEvent;
}
INT8U OsFlagDelete(OS_EVENT *pFlag){return TRUE;}
INT16U OsFlagGet(OS_EVENT *pFlag){
    INT16U i;
    
    if(pFlag==(OS_EVENT *)0) return 0; 
    if(pFlag->EventType!=EVENT_TYPE_FLAG) return 0;
    OS_ENTER_CRITICAL();
    i=pFlag->EventCounter; 
    if(pFlag->EventCounter>0) pFlag->EventCounter--;
    OS_EXIT_CRITICAL();
    return i;
}
void OsFlagPending(OS_EVENT *pFlag,INT16U TimeOut,INT8U *pError){
    OS_TCB *pOsTcb;
    
    if(pFlag==(OS_EVENT *)0){                  // check flag event 
        *pError=OS_ERROR;
        return;
    }     
    if(pFlag->EventType!=EVENT_TYPE_FLAG){     // check event type 
        *pError=OS_ERROR;
        return;
    }     
    OS_ENTER_CRITICAL();
    if(pFlag->EventCounter>0){
        pFlag->EventCounter--;
        OS_EXIT_CRITICAL();
        *pError=OS_NO_ERROR;
        return;
    }
    pOsTcb=(OS_TCB *)OSTCBCur;                 //
    pOsTcb->Status=OS_TASK_PENDING;            // set task pending s.t. scheduler doesn't run it. 
    pOsTcb->PendingType=OS_PENDING_FLAG;       // set pending type
    pOsTcb->pEvent=pFlag;                      // set pending event
    pOsTcb->TimeDelay=TimeOut;                 // set pending time out  
    OsEventPendingTaskPut(pFlag,pOsTcb);     // put this task in event list
    OsSchedulerRunNext();                           // find out next task to run 
    OS_EXIT_CRITICAL();                        // this line execute when return from semaphore waiting list
    if(pOsTcb->TimeDelay==0) *pError=OS_ERROR_TIMEOUT;
    else *pError=OS_NO_ERROR;                  // no error...pending to weakup success!!
    return;                                    // leave pending status
}
INT8U OsFlagPost(OS_EVENT *pFlag){
    OS_TCB *pTcb;
    
    if(pFlag==(OS_EVENT *)0) return OS_ERROR_NULL_POINTER;
    if(pFlag->EventType!=EVENT_TYPE_FLAG) return OS_ERROR_EVENT_TYPE;
    OS_ENTER_CRITICAL();
    if(pFlag->ListHead==(INT32U *)0) pFlag->EventCounter=1; // semaphore free...no task pending for it now
    else{
        pTcb=(OS_TCB *)pFlag->ListHead;
        if(pTcb->Next==(OS_TCB *)0){
            pFlag->ListHead=(INT32U *)0;
            pFlag->EntryNumber=0;
        }
        else{
            pTcb->Next->Prev=(OS_TCB *)0;
            pFlag->ListHead=(INT32U *)pTcb->Next;            
            pFlag->EntryNumber--;
            OsTaskReadyTaskPut(pTcb); // put 1st pending task back to scheduler       
        }    
    }
    OS_EXIT_CRITICAL(); 
    return OS_NO_ERROR;
}

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