accessing a scruct element by relative address?

Hi,

I a large struct named DATA with different datatypes and I want to iterate through it as following:
I want to create an array of struct called TYPES, that describe where and what kind of data have.
Then I want to go through that array and get the date from DATA and processit according to it's type.

How can I get the relative address of a struct element, so I can write it into a TYPES struc as the "where" data?

Thank you!

Greeting from Germany
Christoph

P.S.: Please let me know if something in my descripion wasn't understandable, my english isn't that good.

The & operator

Code:

---

#include <stdio.h>

struct DATA
{
    int y;
    int x;
};

int main(void)
{
    struct DATA someData;
    someData.x = 10;
   
    printf("%p\n",&someData);
    printf("%p\n",&someData.x);
   
    getchar();
   
    return 0;
}

---

Das Problem an der sache ist, dass ich stets ein neues Struct als Zeiger übergeben bekomme (iTunes trackInfo).

Can I then use

Code:

---

Ptr xRelAdr = ((Ptr)&someData.x - (Ptr)&someData); // int is probably the wrong type

(int)(&someData+xRelAdr)*=27;

---

So that I can save the relative address (xRelAdr in this case) and reuse it whenever I get a new pointer to that struct?

Is "Ptr" the right type for a pointer?

The standard type for that is "ptrdiff_t" as defined in stddef.h