lokinet/llarp/util/bits.hpp

#ifndef LLARP_BITS_HPP
#define LLARP_BITS_HPP

#include <bitset>
#include <cstddef>
#include <numeric>
#include <type_traits>
#include <limits>
#include <absl/numeric/int128.h>

namespace llarp
{
  namespace bits
  {
    template < typename Int_t >
    constexpr std::size_t
    count_bits(Int_t i)
    {
      static_assert(std::is_integral< Int_t >::value,
                    "Int_t should be an integer");
      static_assert(std::is_unsigned< Int_t >::value,
                    "Int_t should be unsigned");
      return std::bitset< std::numeric_limits< Int_t >::digits >(i).count();
    }

    constexpr std::size_t
    count_bits_128(const absl::uint128& i)
    {
      return count_bits(absl::Uint128High64(i))
          + count_bits(absl::Uint128Low64(i));
    }

    template < typename InputIt >
    constexpr std::size_t
    __count_array_bits(InputIt begin, InputIt end)
    {
      return std::accumulate(begin, end, 0, [](auto acc, auto val) {
        return acc + count_bits(val);
      });
    }

    template < typename T >
    constexpr std::size_t
    count_array_bits(const T& array)
    {
      return __count_array_bits(std::begin(array), std::end(array));
    }
  }  // namespace bits
}  // namespace llarp

#endif