This C++ code, can someone create notes for this and break down what each line means line by line?

int readFloatMap(string fileName, double arr[][4], int rows) { ifstream f(fileName.c_str());

if(f.fail()) { return -1; }

double a, b, c, d;

int r = 0; while((r < rows) && (f >> a >> b >> c >> d)) { arr[r][0] = a; arr[r][1] = b; arr[r][2] = c; arr[r][3] = d; r++; }

return r; // success }