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I have initialised 3 instances of a cache I have defined using typedef. I have done some processing on them in a serious of if statements in the following way : 

cache cache1;
cache cache2; 
cache cache3; 
int a;

void main(...) {
 if (a == 0) { 
 cache1.attribute = 5; 
} 
else if (a == 1) {
 cache2.attribute = 1;
}
else if (a == 2) {
cache3.attribute = 2 ;
}

However now I need to make the design modular in the following way: 

cache cache1;
cache cache2;
cache cache3;

void cache_operator( cache user_cache, int a ) {
  user_cache.attribute = a;
}

void main(...) {
  if (a == 0) {
    cache_operator(cache1,5);
}
  else if (a == 1) {
  cache_operator(cache2,1);
}
...

I am having trouble with passing the cache to the method. I'm used to java programming and I'm not very familiar with c pointers. However, if I pass the cache itself as shown above I am passing a copy of the cache on the stack which then produces results different to the original code. How do I properly transform the first design into the second design when it comes to passing the appropriate cache to the function and making sure it is accessed properly.

Alk
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1 Answers1

2

In C language, if you want to keep track of the original 'data' instead of creating a copy in the function, you have to pass the pointer of that data to that function.

Pointer in C is just like the reference to object in JAVA.

Following is how you do it.

void cache_operator( cache *user_cache, int a ) 
{
    user_cache->attribute = a;
}

Following is how you call the function.

 cache_operator(&cache1,5);

I also started with JAVA. I don't know why some universities nowadays use JAVA as beginning language... It is quite strange, since JAVA is a high-level language making the abstraction of low-level detail, whereas C is a rather low-level language. In the past, this will never be the case..

Euclid Ye
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  • Yes I know, can you demonstrate how the synthax for that would look when it comes to passing the parameter, the original function definition and accessing the attribute in the method. This is what I have a problem with. – Alk Nov 19 '15 at 04:04
  • So I would call this function like this `cache_operator( * cache1, 5);` ? – Alk Nov 19 '15 at 04:06
  • If you find the solution works, don't forget to accept the answer~ – Euclid Ye Nov 19 '15 at 04:09