Count consecutive ones

#include <cinttypes>
#include <cstdint>
#include <cstdio>
using namespace std;
static uint8_t count_consecutive_ones(uint64_t);
static uint8_t count_consecutive_ones_recursive(uint64_t);
static uint8_t count_consecutive_ones_recursive_sub(uint64_t, uint8_t);

// http://stackoverflow.com/a/12617595
static uint8_t count_consecutive_ones(uint64_t in) {
  uint8_t count = 0;
  while (in) {
    in = (in & (in << 1));
    ++count;
  }
  return count;
}

static uint8_t count_consecutive_ones_recursive(uint64_t in) {
  return count_consecutive_ones_recursive_sub(in, 0);
}

static uint8_t count_consecutive_ones_recursive_sub(uint64_t in, uint8_t acc) {
  if (in == 0) return acc;
  return count_consecutive_ones_recursive_sub((in & (in << 1)), acc + 1);
}

int main() {
  uint64_t test_case[] = { 0xffffffffull, 0xfff0ffffull, 0xff0fffffull };
  for (auto&& e: test_case) {
    printf(
      "%" PRIx64 ", no recur: %" PRId8 ", recur: %" PRId8 "\n",
      e,
      count_consecutive_ones(e),
      count_consecutive_ones_recursive(e)
    );
  }
}