How to index a heap allocated matrix in C?-CodePudding

I am making a minesweeper program in C.

I have this as a global variable:

typedef struct box_t
{
  int box_type;
  int num_mines_bordering;
  int is_flagged;
} box_t;

// my global
box_t * gameboard = NULL;

Later in the application it is allocated in the heap based on the number of rows and columns:


gameboard = (box_t *)malloc((rows * cols) * sizeof(box_t));

All is well, however, they way I index it now seems incorrect and error-prone. I can't simply do gameboard[x][y] because I get compiler errors and what I have now seems incorrect:

#define GET_LOC(ROW, COL) gameboard[(ROW * sizeof(box_t))   (COL * sizeof(box_t)) * sizeof(box_t)]
// if you call this it would look like: box_t * loc = &GET_LOC(somerow, somecol);

Is there a better way to index it?

CodePudding user response：

The compiler knows the type and hence the size of each array entry, so the only special thing is the number of columns cols:

box_t *gameboard = malloc((rows * cols) * sizeof(*gameboard));
gameboard[row * cols   col] = ...;