mirror of
https://github.com/bolero-MURAKAMI/Sprout.git
synced 2024-12-25 21:35:41 +00:00
73 lines
2.3 KiB
C++
73 lines
2.3 KiB
C++
#ifndef SPROUT_BIT_LENGTH_HPP
|
|
#define SPROUT_BIT_LENGTH_HPP
|
|
|
|
#include <climits>
|
|
#include <cstddef>
|
|
#include <type_traits>
|
|
#include <sprout/config.hpp>
|
|
|
|
namespace sprout {
|
|
namespace detail {
|
|
SPROUT_STATIC_CONSTEXPR std::size_t bit_len_8_table[std::size_t(UCHAR_MAX) + 1] = {
|
|
0, 1, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4,
|
|
5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
|
|
6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
|
|
6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
|
|
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
|
|
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
|
|
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
|
|
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
|
|
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
|
|
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
|
|
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
|
|
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
|
|
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
|
|
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
|
|
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
|
|
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8
|
|
};
|
|
template<std::size_t Size>
|
|
struct bit_len {
|
|
private:
|
|
SPROUT_STATIC_CONSTEXPR std::size_t next_size = Size - 1;
|
|
SPROUT_STATIC_CONSTEXPR std::size_t shift_bits = next_size * CHAR_BIT;
|
|
private:
|
|
template <typename IntType>
|
|
SPROUT_CONSTEXPR IntType
|
|
impl(IntType x, unsigned char i) const {
|
|
return bit_len_8_table[i]
|
|
? bit_len_8_table[i] + next_size * CHAR_BIT
|
|
: sprout::detail::bit_len<next_size>().template operator()(x)
|
|
;
|
|
}
|
|
public:
|
|
template <typename IntType>
|
|
SPROUT_CONSTEXPR IntType
|
|
operator()(IntType x) const {
|
|
return impl(x, static_cast<unsigned char>((x >> shift_bits) & UCHAR_MAX));
|
|
}
|
|
};
|
|
template<>
|
|
struct bit_len<1> {
|
|
public:
|
|
template<typename IntType>
|
|
SPROUT_CONSTEXPR IntType
|
|
operator()(IntType x) const {
|
|
return bit_len_8_table[static_cast<unsigned char>(x & UCHAR_MAX)];
|
|
}
|
|
};
|
|
} // namespace detail
|
|
//
|
|
// bit_length
|
|
//
|
|
template<typename IntType>
|
|
inline SPROUT_CONSTEXPR typename std::enable_if<
|
|
std::is_integral<IntType>::value,
|
|
IntType
|
|
>::type
|
|
bit_length(IntType x) {
|
|
return sprout::detail::bit_len<sizeof(IntType)>().template operator()(x);
|
|
}
|
|
} // namespace sprout
|
|
|
|
#endif // #ifndef SPROUT_BIT_LENGTH_HPP
|