Int to Binary Conversion explanation

Question

My question is based on this post: Decimal to Binary and it\'s chosen solution.

I can get the chosen answer code working, but it only works for 5 bits. How do I modi

Answer 1

After accept answer.

Too many magic numbers.

In the original, there are constants 5, 0x10, 6 that do not show there relationship to the goal of a 5 binary digit number.

Then when going to 8, the constants 8, 0x10, 9 were used. Since 0x10 was not adjusted, code failed.

Instead approach the problem with a more general point-on-view and use code that eliminates or better expresses these magic numbers.

#define BitWidth 5

void getBin(int num, char *str)
{
  int mask = 1 << (BitWidth - 1);
  // skip the original shift left and then immediately shift right
  do {
    *str++ = !!(mask & num) + '0';
  } while (mask >>= 1);
  *str = '\0';  // by appending at the end, no need for a magic number
}  

int main()
{
  char str[BitWidth + 1];
  getBin(10, str);
  printf("%s\n", str);
  return 0;
}

Note: the above approach (and other answers) have a problem when BitWidth matches the int width. But that is another issue easily solved by using unsigned math.