-

mystring base64tobinary(mystring source)
{
  int i;
  int index;
  char base64[64] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  char *tmp;
  char chunk[7] = "";
  mystring result;
  result.text[0] = '\0';
  for (i = 0; i < source.length; i++)
  {
    tmp = strchr(base64, source.text[i]);
    index = (int) (tmp - base64);
    dectobinary(index, chunk);
    strcat(result.text, chunk);
  }
  return result;
}

char* dectobinary(int source, char * result)
{
  char *p = result;
  int i, k;
  for (i = 5; i >= 0; i--)
  {
    k = source >> i;

    if (k & 1)
      *p++ = '1';
    else
      *p++ = '0';
  }
  *p = '\0';
  return result;
}