Question

我正在编写一个小程序来模拟操作系统内的调度程序，并且在执行期间我注意到当我为链接列表的头指针分配一个新值时，这不会延续到下一个函数中。它几乎就像我甚至没有写过。

//insert at head of Event queue
if(ecursor == ehead){
    cout << "insert at head" << endl;
    eve->prev =  NULL;
    eve->next = ecursor;
    ecursor->prev = eve;
    ehead = eve;
    ecursor = eve;
}

我已经仔细检查了插入登录，以确保我没有遗漏任何东西，并且它适用于其他插入。在某些时候它永远不会正确指定头指针。

在插入之后，头指针被读入程序的主体，然后显示事件发生的时间（可能是我们刚刚使头部等于的事件）

事件类型：2

检查队列中的事件

ecount：1

检查事件顺序

eve-＆gt;时间：0.0667091

ecursor-＆gt;时间：0.0108831

尾部后插入

调度到达：1

事件类型：1

检查队列中的事件

ecount：1

检查事件顺序

eve-＆gt;时间：0.015281

ecursor-＆gt;时间：0.0667091

插入头部

时钟：0.0667091

类型1：到达

类型2：离开

正如您所看到的那样，最后一次插入是在头部插入的，新的头部时间应该是插入的事件时间，但时钟不显示该更改。

这里有一些参考程序

void insert_event(struct event* eve)
{
ecursor = ehead;

cout << "event type: " << eve->type << endl;

cout << "check for no events in queue" << endl;

cout << "ecount: " << ecount << endl;

if(ecount == 0){

    ehead = eve;

    eve->next = NULL;

    eve->prev = NULL;

    etail = ehead;
}


//if newEvent is preceded by other events/event queue not empty
else{
    cout << "check event order" << endl;
    //insert new arrival into Event queue
    do{
        cout << "eve->time: " << eve->time << endl;
        cout << "ecursor->time: " << ecursor->time << endl;
        //new arrival earlier than event cursor points to 
        if(ecursor->time >= eve->time){

            //insert at head of Event queue
            if(ecursor == ehead){
                cout << "insert at head" << endl;
                eve->prev =  NULL;
                eve->next = ecursor;
                ecursor->prev = eve;
                ehead = eve;
                ecursor = eve;
            }

            //insert inside of Event queue
            else{
                cout << "insert inside " << endl;
                ecursor->prev->next = eve;
                eve->next = ecursor;
                eve->prev = ecursor->prev; 
                ecursor->prev = eve;
            }
            break;
        }

        //new arrival after final event in Event queue
        //insert at tail of Event queue
        else if(ecursor == etail && (ecursor->time < eve->time)){
            cout << "insert after tail" << endl;
            ecursor->next = eve;
            eve->prev = ecursor;
            etail = eve;
            break;
        }

        ecursor = ecursor->next;
    }while(ecursor != NULL);

    //reset ecursor to head of Event queue
    ecursor = ehead;


//increment Event queue count
ecount++;
}


int process_event_ARR(struct event* eve){

cout << "processing arrival: " << pacount << endl; 
//generate new process
struct process* proc = new process;


//process time starts now
proc->start = simclock;

//generate service time for process
proc->serTime = genexp(1/Ts);

//if no processes to service, service arrival instantly
//add departure event
if(!server_busy){

    phead = proc;
    schedule_event_DEP(proc);
    server_busy = true;

    //set CPU to proc
    inCPU = proc;
}

//behavior for process queueing
else{

    //Non Premptive
    if(sType == 1 || sType == 3)
        //process to ready queue
        phead->next = proc;
        phead = proc;
    }
}

//remove arrival from Event queue
remove_event(eve);
eve = NULL;

//schedule new Arrival Event
schedule_event_ARR();

//increment process count
pcount++;
pacount++;
}

int process_event_DEP(struct event* eve){

pcursor = phead;
cout << "processing dep: " << depcount << endl;
//process completed process
eve->link->finish = simclock;

cout << " if no ready queue release cpu" << endl;
if(pcount == 0)
    server_busy = false;

else{
    cout << "creating temp process" << endl;
    struct process* temp = new process;

    cout << "assigning temp process cursor time" << endl;
    temp->start = pcursor->start;

    cout << "schedule next process" << endl;
    switch(sType){
        case 1:     //FCFS
                    do
                        if(pcursor->start < temp->start)
                            temp = pcursor;

                        pcursor = pcursor->next;
                    while(pcursor != NULL);

                    schedule_event_DEP(temp);
                    inCPU = temp;
                    break;
        default:
                    //error
                    break;
    };
};

//remove event from Event queue/process from ready queue
remove_event(eve);
eve = NULL;

//incremement departure count
//decrement process/event count
dcount++;   
pcount--;
ecount--;
}


int run_sim(){

struct event* eve = new event;
while(!(dcount > 10000)){

    eve = ehead;
    simclock = eve->time;
    cout << "clock: " << simclock << endl;
    switch (eve->type){

        case ARR:
            process_event_ARR(eve);
            break;
        case DEP:
            process_event_DEP(eve);
            break;
        case Qtum:
            process_event_tslice(eve);
            break;
        default:
            //error
            break;

    }
    ehead = eve->next;
    free(eve);
    eve = NULL;
}

return 0;
}

指针赋值没有通过多个函数c ++持有

0 个答案: