非阻塞输入C [英] Non blocking input C

问题描述

我正在尝试创建一个程序，向用户询问一个问题并有几秒钟的时间回答该问题，否则该程序将停止输入.

I'm trying to create a program where the user is asked a question and has a few seconds to answer the question, or else the program stops input.

现在我的问题是我无法使我的程序不阻止输入. 我可以输入数据，但是当我不输入数据并且计时器用完时，它会不断要求输入.

Now my problem is I'm unable to get my program not to block input. I am able to input data, but when I don't and the timer runs out it keeps asking for input.

我正在Windows上运行，并使用Code :: Blocks以防万一. 如果有人可以向我解释我在做什么错，那将不胜感激.

I'm running on Windows and use Code::Blocks in case it's important. If someone could explain to me what I'm doing wrong, it would be appreciated.

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <pthread.h>
#include <conio.h>

int key = 0;
int GradeTotal = 0;

//runs an empty loop every iteration F.E. for loop
void timer(int seconds)
{
    clock_t wait = (clock() + (seconds * CLOCKS_PER_SEC));
    while(clock() < wait){}

}

void timeleft()
{
    int index;

    for(index = 5; index >= 0; index--)
    {
        if(key != 0)
        {
            pthread_exit(timeleft);
        }

        timer(1);

        if(index == 0)
        {
        printf("\n\nTime's up!");
        }
    }
}

void questions()
{
    int key;

    printf("what is 1 + 1?\nAnswer: ");

    while(1)
    {
        if(_kbhit())
        {
            key = _getch();
            printf("%c",key);
            break;
        }
    }
    if(key == 50)
    {
         GradeTotal += 1;
    }  
 }


int main()
{
    pthread_t thread1,thread2;

    int index;
    int seconds = 0;
    pthread_create(&thread1, NULL, questions, NULL);
    pthread_create(&thread2, NULL, timeleft, NULL);
    pthread_join(thread1, NULL);
    pthread_join(thread2, NULL);

    printf("\n\nGrade: %d",GradeTotal);

    return 0;
}

推荐答案

当时间用完时，请timeleft()设置一个全局标志，该标志由questions()测试，如果设置，则使代码离开while (1)循环.

When time ran out have timeleft() set a global flag, which is tested by questions(), and if set makes the code leave the while (1) loop.

确保使用互斥锁保护对标志的访问.

Make sure access to the flag is protected using a mutex.

谈论受保护的访问":key是在没有保护的情况下并发访问的.不好.

Talking about "protected access": key is accessed concurrently without protection. Not good.

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