BlackMATov/meta.hpp
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constexpr hashed_string

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BlackMATov
2023-01-31 07:42:16 +07:00
parent 6a8aa13444
commit 14193a1434
3 changed files with 177 additions and 34 deletions
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58
headers/meta.hpp/meta_base/hashed_string.hpp
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@@ -8,6 +8,35 @@
#include "base.hpp"
namespace meta_hpp::detail
{
template < std::size_t SizeBytes = sizeof(std::size_t) >
struct fnv1a_hash_traits;
template <>
struct fnv1a_hash_traits<4> { // NOLINT(*-magic-numbers)
using underlying_type = std::uint32_t;
static inline constexpr underlying_type prime{16777619U};
static inline constexpr underlying_type offset{2166136261U};
};
template <>
struct fnv1a_hash_traits<8> { // NOLINT(*-magic-numbers)
using underlying_type = std::uint64_t;
static inline constexpr underlying_type prime{1099511628211U};
static inline constexpr underlying_type offset{14695981039346656037U};
};
constexpr std::size_t fnv1a_hash(std::string_view str) noexcept {
std::size_t hash{fnv1a_hash_traits<>::offset};
for ( char ch : str ) {
hash ^= static_cast<std::size_t>(ch);
hash *= fnv1a_hash_traits<>::prime;
}
return hash;
}
}
namespace meta_hpp::detail
{
class hashed_string final {
@@ -21,40 +50,35 @@ namespace meta_hpp::detail
hashed_string& operator=(hashed_string&&) = default;
hashed_string& operator=(const hashed_string&) = default;
hashed_string(const char* str) noexcept
: hash_{std::hash<std::string_view>{}(str)} {}
constexpr hashed_string(const char* str) noexcept : hash_{fnv1a_hash(str)} {}
constexpr hashed_string(std::string_view str) noexcept : hash_{fnv1a_hash(str)} {}
constexpr hashed_string(const std::string& str) noexcept : hash_{fnv1a_hash(str)} {}
hashed_string(std::string_view str) noexcept
: hash_{std::hash<std::string_view>{}(str)} {}
hashed_string(const std::string& str) noexcept
: hash_{std::hash<std::string_view>{}(str)} {}
void swap(hashed_string& other) noexcept {
constexpr void swap(hashed_string& other) noexcept {
std::swap(hash_, other.hash_);
}
[[nodiscard]] std::size_t get_hash() const noexcept {
[[nodiscard]] constexpr std::size_t get_hash() const noexcept {
return hash_;
}
private:
std::size_t hash_{};
std::size_t hash_{fnv1a_hash("")};
};
inline void swap(hashed_string& l, hashed_string& r) noexcept {
constexpr void swap(hashed_string& l, hashed_string& r) noexcept {
l.swap(r);
}
[[nodiscard]] inline bool operator<(hashed_string l, hashed_string r) noexcept {
[[nodiscard]] constexpr bool operator<(hashed_string l, hashed_string r) noexcept {
return l.get_hash() < r.get_hash();
}
[[nodiscard]] inline bool operator==(hashed_string l, hashed_string r) noexcept {
[[nodiscard]] constexpr bool operator==(hashed_string l, hashed_string r) noexcept {
return l.get_hash() == r.get_hash();
}
[[nodiscard]] inline bool operator!=(hashed_string l, hashed_string r) noexcept {
return l.get_hash() == r.get_hash();
[[nodiscard]] constexpr bool operator!=(hashed_string l, hashed_string r) noexcept {
return l.get_hash() != r.get_hash();
}
}
@@ -62,7 +86,7 @@ namespace std
{
template <>
struct hash<meta_hpp::detail::hashed_string> {
size_t operator()(meta_hpp::detail::hashed_string hs) const noexcept {
constexpr size_t operator()(meta_hpp::detail::hashed_string hs) const noexcept {
return hs.get_hash();
}
};