Malloc a 3-Dimensional array in C?

Question

I'm translating some MATLAB code into C and the script I'm converting makes heavy use of 3D arrays with 10*100*300 complex entries. The size of the array also depends on the sensor's input, ideally the array should be allocated dynamically. So far I've tried two approaches the first being a flat 1D array along the lines of

value = array[x + (y*xSize) + (z*ySize*xSize)] 

Which hurts my brain to use. I've also tried an array of an array of pointers

int main () {   int ***array = malloc(3*sizeof(int**));   int i, j;    for (i = 0; i < 3; i++) {     *array[i] = malloc(3*sizeof(int*));     for (j = 0; j < 3; j++) {       array[i][j] = malloc(3*sizeof(int));     }   }    array[1][2][1] = 10;    return 0; } 

Which gives a seg fault when I try to assign data.

In a perfect world, I'd like to use the second method with the array notation for cleaner, easier programming. Is there a better way to dynamically allocate a three-dimensional array in C?

Answer 1

I'd go for the first option (the single 1D array) as it will give you a single block of memory to play in rather than potentially thousands of fragmented memory blocks

If accessing the correct element of the array is doing your head in though, I'd write a utility method to convert x, y, z locations into an offset into the 1D array

int offset(int x, int y, int z) {      return (z * xSize * ySize) + (y * xSize) + x;  }