一意孤行: 回调机制的简单实现

回调机制的简单实现

a simple implement of callback mechanism

上班的时候一个同事坐在我旁边看我review代码，看到了我的callback函数，就开始问我这是什么东西，我很奇怪，丫也工作了好几年了，怎么还问我这种问题，给他解释了老半天。然后他要我给他将怎么样实现的，能不能给他写一个范例。给磨得没有办法，就信手写了一下。

/* --------------------------------------------------------------
 * FILE NAME : Callback.c
 * AUTHOR : sAm yOuNg
 * Creation Date : 2005/12/05
 * DESCRIPTION : a demo of callback mechanism  *
 * --------------------------------------------------------------
 */

//define register table struct
typedef struct tagCallbackTable
{
    unsigned int nEvent;
    void (*callbackfunc)(char *buffer,unsigned int len);
}STRUCT_REG_TABLE,*PSTRUCT_REG_TABLE;

#define MaxEvent 12

//define the msg struct
typedef struct tagMsgHeader
{
    int nIdx;
    int nEvent;
    int nLen;
}STRUCT_MSG_HEADER,*PSTRUCT_MSG_HEADER;

//define a global variable of table array
STRUCT_REG_TABLE g_RegTable[MaxEvent];

//phase 1,init the reg table
memset(g_RegTable,0,sizeof(STRUCT_REG_TABLE)*(MaxEvent));

//phase 2, receive the register event
void RegisterEvent(int msgEvent,void (*callback_func)(char *buffer,int len))
{
    //validate the register params.    //write to register table
    g_RegTable[msgEvent].nEvent = msgEvent;
    g_RegTable[msgEvent].callbackfunc = callback_func;
}

//phase 3, process message and registered table.
void mainTableProcess()
{
    int msgEvent=0;
    int len=0;

    PSTRUCT_MSG_HEADER lpMsgHeader = NULL;

    //get msg and allocate buffer
    while(getMsg(lpMsgHeader))
    {
        msgEvent=lpMsgHeader->nEvent;
        len=lpMsgHeader->nLen;

        for(int i=0;i<=MaxEvent;i++)
        {
            if( (g_RegTable[i].nEvent == msgEvent) )
            {
                //call the callback function registered
                g_RegTable[i].callbackfunc((char*)lpMsgHeader,len);
            }
        }
    }
}

//define a callback function and register it
//define events
#define EVENT_1 1
#define EVENT_2 2
#define EVENT_3 3

void test_callback_1(char *pptr,uint len)
{
    PSTRUCT_MSG_HEADER lpMsgHeader = NULL;

    //process the msg buffer

    return 0;
}
void test_callback_2(char *pptr,uint len)
{
    PSTRUCT_MSG_HEADER lpMsgHeader = NULL;

    //process the msg buffer

    return 0;
}

//init system and register event and callback function
void sysInit()
{
    //init sys

    //.................

    //register event and callback function
    RegisterEvent(EVENT_1,test_callback_1);

    RegisterEvent(EVENT_2,test_callback_2);

}

Posted by 三更天 at December 5, 2005 08:27 PM