Question

I know how to read a file into a 2d array using for loops to direct where you are storing the data in C, but what I am interested in is if you can use one fread() call to do this. That is, can I do something like this:

int A[5][5];
fread(&A, sizeof(int), 25, filePtr);

I am getting seg faults when I tried this so right now so I am wonder if this can be done at all.

EDIT:
Alright, I guess using fread this way isn’t really my problem. My problem is that I have to call fread from within a function and A is defined outside of that function.

func(int size, int ***A)
{
  fread(*A, sizeof(int), size*size, filePtr);
}

main
{
  int A[n][n];
  func(n, &A);
}

So my problem is that my call to fread still seg faults and I HAVE to use a triple pointer for my function prototype. I tried just A (instead of *A) for fun but still got the same seg fault. It looks like I’m just overlooking something with pointers.

Answer 1

My problem was that of contiguous memory. It’s actually very straight forward when you realize that fread is only set up to take single pointers. Therefore it can only take 1-d arrays. However, if your 2-d array is represented in memory contiguously it is analogous to a 1-d array. Therefore, just pass fread a pointer to the first element in your 2-d array, it will start looping through it as if it is a 1-d array and all will be well.

So just make sure your 2-d array is contiguously assigned and you should be fine.

malloc(n*n *sizeof(int)) 

instead of mallocing in a for loop for each row.