Thread: How to return pointer of a sub array?

As i understood your question " array of 20 and u want to return 4 to 12 index values."
So 1st thing is to return address of 4th element and the no of elements u need to read from there in this case it is12-4)=8. So for 8 we can use the 'pass by address' function calling--

Code:

#define ARRAYSIZE 20
int main()
{
int *ptr,array[ARRAYSIZE],readno=0;
ptr=function(array,ARRAYSIZE,&readno);
return 0;
}
int* function(int* array , int oldsize,int* readno)//u can make oldsize(20) as global variable also and read no is 8 which is initially during calling u can use 0.
{
     int j=4;
     *readno=8;//which can be accessed from main(the function fron u calling function() without returning;
     return array+j;
}

I think this will help u if still there is problem then plz elaborate ur question with an example it took me alot of time to understand your question...

"pointer" is not an array -> it is a pointer.

Also, you can not do the following - It's like saying 4 = something

Code:

int *pointer;
int j;

for(j=0;j<size;j++)
  &pointer[j] = &array[j+size];

What I suggest you do is make a function that returns a pointer to an array - It is a bit tricky to get your head around the declaration, so I'll leave you a link to a tutorial that has helped a lot of people - Also, I have knocked together a little function which demonstrates what I've suggested.

http://untroubled.org/articles/cdecls.txt

Code:

#include <stdio.h>
#include <stddef.h>
#include <stdlib.h>


int (*get_subarr ( int in[10] ))[4];


int main(void)
{
    int grape[10] = {1,2,3,4,5,6,7,8,9,0};
    int (*carrot_ptr)[4];
    int i;


    carrot_ptr = get_subarr(grape);


    for(i=0;i<4;i++)
    {
        printf ("%d ", (*carrot_ptr)[i]);
    }


    return EXIT_SUCCESS;


}


int (*get_subarr(int banana[10]))[4]
{
    return (int (*)[4]) &banana[4];
}

I kept going with my example, and this is what I came up with - I'm sure that you can get something out of this

Code:

#include <stdio.h>
#include <stddef.h>
#include <stdlib.h>


#define BUFF 10


/****************************************************************
 * Function get_subarr (get sub array)
 *
 * Returns a pointer to an array (located in a larger array)
 *
 * param m_buff (main buffer) - The buffer that the sub array will be
 *  allocated from.
 *
 * param m_buf_size (main buffer size) - The size of the m_buff array
 *
 * param idx (index)
 * This is where the function will try to
 * allocate the sub array
 *
 * param s_arr_size (sub array size)
 * This is the size of the sub array
 ****************************************************************/
int (*get_subarr (int m_buf[], size_t m_buf_size, int idx, size_t s_arr_size) )[];


int main(void)
{
    int main_buffer[BUFF] = {0,1,2,3,4,5,6,7,8,9};


    int (*sub_buffer_ptr)[5] = NULL;
    int i;


    int sub_array_size = 4;  //Play around with these two values...
    int sub_array_index = 4; //




    sub_buffer_ptr = get_subarr(main_buffer, BUFF, sub_array_index, sub_array_size);
    if (sub_buffer_ptr == NULL)
    {
        fputs("Error in get_subarr", stderr);
        return EXIT_FAILURE;
    }


    for(i=0;i<sub_array_size;i++)
    {
        printf ("%d ", (*sub_buffer_ptr)[i]);
    }


    return EXIT_SUCCESS;


}


int (*get_subarr (int m_buf[], size_t m_buf_size, int idx, size_t s_arr_size) )[]
{
    if ((s_arr_size+idx) > m_buf_size)
    {
        return NULL;
    }
    else
    {
        return (int (*)[]) &m_buf[idx];
    }
}