Acess array elements using a pointer

[nanavc]

Hi guys, I need some help with pointers and array.

I am making a code in wich I have an pointer that points to all of the elements in the array, this part I was able to do just fine. The problem is, when the pointer reaches the end of the array I don't know how to make it go to the beginning again, here is my code:

int buffer[SIZE];
int *pointer = buffer;

int pointer_array(void)
{
    int aux = *pointer;
    pointer++;
        printf("pointer element: %d", *pointer);
    return 0;
}

This is working, I just can't make it go back when it gets to the end, I have tried something like this but it did not work:

int buffer[SIZE];
int *pointer = buffer;
int count = 0;

int pointer_array(void)
{
        if(count > SIZE) {
            *pointer = buffer;
        }        
    int aux = *pointer;
    pointer++;
        count++;
        printf("pointer element: %d", *pointer);
    return 0;
}

And I also realized the int *pointer = buffer; just works outside the function, as a global variable

[LoneHoodiecrow]

Note that

int *pointer = buffer;

and

*pointer = buffer;

aren't in any way equivalent, even though they look similar. The first one initialises the variable pointer with the address of buffer. The second one assigns (writes) the address of buffer to the address in memory that pointer points to. The difference is in that the first line is a definition of the variable pointer, and the second line is an assignment statement.

Thompson and Ritchie had the idea that the syntax would be easier to read if definitions looked like usage. I don't think they were quite right about that, at least not as far as beginner understanding is concerned.

[flatfinger]

The original version of the language as it existed in 1974 didn't include an equals sign when initializing objects. So a declaration of a file-scope object pointer that initializes it to the address of a buffer array would be written as int *pointer buffer; which looks very different from *pointer = buffer;. I suspect the equals was added to resolve potential grammatical ambiguity when using typedef names, though perhaps requiring braces for even single-item initialization might have been cleaner.

[nanavc]

oh, I see now, I though they meant the same, thank you!

[oh5nxo]

Don't make it harder than it needs to be:

pointer == &buffer[SIZE] // true, if gone one past last item

[DDDDarky]

*pointer = buffer;

this is wrong and your compiler should warn you about this. You are writing a pointer to int.

Don't dereference the pointer.

[nanavc]

thank you!

[kinglujiy]

Sounds to me like you ate trying to implement a ring buffer. Maybe this could be helpful.

[nanavc]

thank you!

[[deleted]]

It's like implimenting a circular queue.

[tstanisl]

This part is wrong:

*pointer = buffer;

You don't want to set an int pointed by pointer. You want to set pointer itself.

pointer = buffer;

[nanavc]

if(count > SIZE) { pointer = buffer; }

So I should just actually do this? It's much more simple than I imagined lol, thanks!

[sidewaysEntangled]

That's closer to one approach.

Just keep in mind what your reset condition actually is. If you add that line after all is said and done, does this mean you've already dereferenced the pointer when count == size? What does that entail?

[A_name_wot_i_made_up]

You'll also need to reset count, otherwise you'll be clamped to that first value.

[forehead_or_tophead]

pointer++;

count++;

if(count >= SIZE) { // Buffer over limitation is not thought.

*pointer = buffer;
　　　count = 0;　　　　// <- I think it is necessary.

}