C 结构指针

Question

给定的默认结构:

struct counter {
  long long counter;
};    

struct instruction {
  struct counter *counter;
  int repetitions;
  void(*work_fn)(long long*);
};

static void increment(long long *n){
  n++;
}

我的台词:

n = 2;
struct counter *ctest = NULL;

int i;
if( ctest = malloc(sizeof(struct counter)*n){
  for( i=0; i<n ;i++){
    ctest[i].counter = i;
  } 

  for( i=0; i<n ;i++){
    printf("%lld\n", ctest[i].counter);
  }
}

struct instruction itest;

itest.repetitions = 10;
itest.counter = ctest; //1. This actually points itest.counter to ctest[0] right?
                       //2. How do I actually assign a function?    

printf("%d\n", itest.repetitions);
printf("%lld\n", itest.counter.counter); // 3. How do I print the counter of ctest using itest's pointer?

所以我正在努力让这三件事发挥作用。

谢谢

Answer 1

itest.counter = ctest; // This actually points itest.counter to ctest[0] right?

没错。 itest.counter == &ctest[0]。此外，itest.counter[0] 直接引用第一个 ctest 对象，itest.counter[1] 引用第二个，依此类推。

How do I actually assign a function?

itest.work_fn = increment;

How do I print the counter of ctest using itest's pointer?

printf("%lld\n", itest.counter->counter); // useful if itest.counter refers to only one item
printf("%lld\n", itest.counter[0].counter); // useful if itest.counter refers to an array