Addresses and extracting the value stored at an address

Hi,
- I am in doubt whether or not the following C code will do as it is intended. For example, does it - as expected - take a whole array (called vector) as input, or is there something very basic in the syntax which makes that not possible as it is now?

- As i've worked in matlab for years, i have forgotten a lot of the fine details in C - like addresses and pointers. I expect the LUT_BASE define is alright - but will *(LUT_BASE+k) take the value at address (LUT_BASE+k) ?
For example, if k is 2, and the memory at address location 0x001002 contains the integer 43 - would *(LUT_BASE+2) then return 43?

- I'm also a little bit confused about the addresses to increment to get the next number in the look-up table. Each number in the look-up-table is stored as signed integers (16 bit) - but wouldn't that mean that i have to increase the addresses for each iteration by 5 (2^4=16, and increment 1 to the next address to find the start)?

Thanks for any hints.

Code:

---

#include <stdio.h>
#define BLOCK_SIZE 2048
#define LUT_BASE ( char *) 0x001000f

void main(int **permute, int *array)
{
 int k;
 int permute[BLOCK_SIZE];
    for(k=0; k<=BLOCK_SIZE-1; k++)
        {
        permute[k]=array[*(LUT_BASE+k)];
        }
 return;
}

---

You need to define a poiner (e.g. char * or int *, depending on what is actually at LUT_BASE), and then assign that pointer to LUT_BASE (using a cast to make the compiler happy that you actually DO want to assign an integer to a pointer). [It is technically possible to do this using no pointer, but it's messy and generally no better].

--
Mats

Thanks,
Hmm something along these lines?
The pointer of p should then be pointing at LUT_BASE

Code:

---

#include <stdio.h>
#define BLOCK_SIZE 2048
#define LUT_BASE ( char *) 0x001000f

void main(int **permute, int *array)
{
 int *p;
 p* = (int)LUT_BASE;
 int k;
 int permute[BLOCK_SIZE];
    for(k=0; k<=BLOCK_SIZE-1; k++)
        {
        permute[k]=array[p+k];
        }
 return;
}

---

wrong cast - it should be

Code:

---

#define LUT_BASE (int *)0x1000f;
int *p = LUT_BASE;

---

and you need to dereference the pointer:

Code:

---

permute[k]=array[*p+k];

---

Also, is LUT_BASE a byte or 32-bit value? If it's a 32-bit value, then you should have a int *, if it's a byte you should have unsigned char (or char, if you want negative values).

--
Mats

Now after some time - that actually makes sense. I don't recall why i had #define LUT_BASE ( char *) 0x001000f with a char to begin with actually, it should have been int, 32 bit.
Thanks again :)