Trying to make a void function edit a 2D array!

Question

Okay, this is kind of a newbie question, and I understand that the function parameters I gave for the function in question are probably horribly off, but here's what I'm trying to do:

I've got an 80x25 2D array of CHAR_INFO's (buffer) that will be printed to the console screen every iteration of the infinite loop. Because the buffer will be constantly changing (its a nethack like game), I want to change the array every loop.

I could easily just integrate the loop into the main function, but for the sake of learning and organization, I wanted to split it off into its own function WriteBuffer(); I've been looking everywhere on how I can pass the 2D CHAR_INFO array into the function by reference so I can edit it, but nothing seems to work. Please don't tell me to use vectors or anything, I'd like to work with what I've got here.

#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#include <stdlib.h>
#define SCREEN_WIDTH 80
#define SCREEN_HEIGHT 25

using namespace std;
void WriteBuffer(CHAR_INFO **bufferp[][SCREEN_WIDTH]);

int main()
{
    //Initialize screen buffer and cursor
    HANDLE hConsoleOutput( GetStdHandle(STD_OUTPUT_HANDLE) );
    COORD dwBufferSize = { SCREEN_WIDTH,SCREEN_HEIGHT };
    COORD dwBufferCoord = { 0, 0 };
    SMALL_RECT rcRegion = { 0, 0, SCREEN_WIDTH-1, SCREEN_HEIGHT-1 };
    CHAR_INFO buffer[SCREEN_HEIGHT][SCREEN_WIDTH];
    CONSOLE_CURSOR_INFO lpConsoleCursorInfo = { 1, false };
    SetConsoleCursorInfo(hConsoleOutput, &lpConsoleCursorInfo);
    //characters
    char characters[3];
    characters[0] = static_cast<char>(177);
    characters[1] = static_cast<char>(177);
    characters[2] = static_cast<char>(177);
    characters[3] = static_cast<char>(177);
    //colors
    ULONG colors[3];
    colors[0] = 0x0A;
    colors[1] = 0x0B;
    colors[2] = 0x0C;
    colors[3] = 0x0D;
    //begin infinite loop
    while (1)
    {
          ReadConsoleOutput( hConsoleOutput, (CHAR_INFO *)buffer, dwBufferSize,dwBufferCoord, &rcRegion );
          WriteConsoleOutput( hConsoleOutput, (CHAR_INFO *)buffer, dwBufferSize,dwBufferCoord, &rcRegion );
          Sleep(100);
    }
}

void WriteBuffer(CHAR_INFO **bufferp[][SCREEN_WIDTH])
{
    int x, y, i = 0; 
    while(y < SCREEN_HEIGHT)
    {      
           while(x < SCREEN_WIDTH)
           {

               bufferp[y][x].Char.AsciiChar = characters[i];
               bufferp[y][x].Attributes = colors[i];
               x++;
           }
           x = 0;
           y++;
    }
}

Answer 1

In C++ and C, arrays are actually pointers, and so you can pass the value of the pointer. In other words, I don't think you should try passing by reference, but simply pass by value. Furthermore, the "[]" following a variable name means that it is a pointer --- thus, in your declaration of WriteBuffer, you essentially wrote CHARINFO****!

(Note (as I don't have enough rep to comment. :/) In general, it may also be helpful if you included an attempted call to WriteBuffer, and any errors if that occurs).

Answer 2

You can use any of the following equivalent declarations:

void WriteBuffer(CHAR_INFO bufferp[SCREEN_HEIGHT][SCREEN_WIDTH]);
void WriteBuffer(CHAR_INFO bufferp[][SCREEN_WIDTH]);
void WriteBuffer(CHAR_INFO (*bufferp)[SCREEN_WIDTH]);

The second is allowed since you can omit the first array dimension of a multidimensional array*. The third is allowed via pointer decay--an array in a parameter list "decays" to a pointer and is equivalent. Note that this only happens once. You cannot use the following declaration:

Wrong!

void WriteBuffer(CHAR_INFO **bufferp);

That's because CHAR_INFO *bufferp[SCREEN_WIDTH] decays into CHAR **bufferp, but as you see above we have CHAR_INFO (*bufferp)[SCREEN_WIDTH] which is a subtly different beast.

^{* The reason you can omit the first dimension is because the compiler doesn't need it to calculate offsets into the array. If you have array[W][H] and access element array[x][y] the compiler turns that into *(&array[0][0] + y*H + x). Notice how W is not needed in that computation. It can therefore be omitted in a function's parameter list.}