Using a 1D Array as a 2D Array in C

Lately, I’ve been writing a lot of C code and using large multidimensional arrays. I’ve found that using a simple macro to map a 1D array to a 2(or more)D array has simplified my code and may make my code marginally faster.

Macro:

#define DATA(r, c) (data[(r)*width + (c)])

Accessing the array:

DATA(rowNdx, colNdx) = x;

Why?

• Only need to malloc and free once: malloc(sizeof(char) * width * height) instead of mallocing for each row of the array
• Since the preprocessor handles the macro, there isn’t any extra overhead of function calls
• Array access is terse and it’s very clear what is going on - instead of arr[x][y], you have arr(x,y)