Question

This question builds off of a previously asked question: Pass by reference multidimensional array with known size

I have been trying to figure out how to get my functions to play nicely with 2d array references. A simplified version of my code is:

    unsigned int ** initialize_BMP_array(int height, int width)     {        unsigned int ** bmparray;        bmparray = (unsigned int **)malloc(height * sizeof(unsigned int *));        for (int i = 0; i < height; i++)        {         bmparray[i] = (unsigned int *)malloc(width * sizeof(unsigned int));        }       for(int i = 0; i < height; i++)         for(int j = 0; j < width; j++)         {              bmparray[i][j] = 0;         }     return bmparray;     } 

I don’t know how I can re-write this function so that it will work where I pass bmparray in as an empty unsigned int ** by reference so that I could allocate the space for the array in one function, and set the values in another.

Answer 1

Use a class to wrap it, then pass objects by reference

class BMP_array { public:     BMP_array(int height, int width)     : buffer(NULL)     {        buffer = (unsigned int **)malloc(height * sizeof(unsigned int *));        for (int i = 0; i < height; i++)        {         buffer[i] = (unsigned int *)malloc(width * sizeof(unsigned int));        }      }      ~BMP_array()     {         // TODO: free() each buffer     }      unsigned int ** data()     {         return buffer;     }  private: // TODO: Hide or implement copy constructor and operator= unsigned int ** buffer };