Skip to content

Commit

Permalink
upgrade memutil::unaligned to fully consteval capable
Browse files Browse the repository at this point in the history
  • Loading branch information
Artur Bać committed Feb 24, 2024
1 parent 7e28271 commit f7a06d1
Show file tree
Hide file tree
Showing 2 changed files with 66 additions and 28 deletions.
55 changes: 40 additions & 15 deletions include/utils/unaligned.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -62,12 +62,17 @@ namespace detail
[[nodiscard, gnu::always_inline]]
inline constexpr output_type unaligned_load(iterator it) noexcept
{
using tmp_value_type = iterator_value_type_t<iterator>;
static_assert(sizeof(tmp_value_type) == 1);
using input_value_type = std::iter_value_t<iterator>;
static_assert(sizeof(input_value_type) == 1);

std::aligned_storage_t<sizeof(output_type), alignof(output_type)> tmp_store;
std::copy_n(it, sizeof(output_type), std::launder(reinterpret_cast<tmp_value_type *>(&tmp_store)));
return *std::launder(reinterpret_cast<output_type *>(&tmp_store));
struct value_buffer_type
{
std::array<input_value_type, sizeof(output_type)> buffer;
};

value_buffer_type store;
std::copy_n(it, sizeof(output_type), store.buffer.begin());
return cxx20::bit_cast<output_type>(store);
}

///\brief loads value from any untyped pointer memory location
Expand All @@ -81,7 +86,7 @@ namespace detail

//---------------------------------------------------------------------------------------------------
///\brief loads value from any forward iterator or unaligned memory location
template<detail::arithmetic_or_bool output_type, typename iterator>
template<detail::trivially_copyable output_type, typename iterator>
[[nodiscard, gnu::always_inline]]
inline constexpr output_type unaligned_load(iterator it) noexcept
{
Expand All @@ -92,7 +97,7 @@ inline constexpr output_type unaligned_load(iterator it) noexcept
///\details specifing expected_storage_size prevents unintended breaking changes with IO to trivially_copyable
/// underlaing type
template<detail::trivially_copyable output_type, std::size_t expected_storage_size, typename iterator>
requires(!detail::arithmetic_or_bool<output_type> && expected_storage_size == sizeof(output_type))
requires(expected_storage_size == sizeof(output_type))
[[nodiscard, gnu::always_inline]]
inline constexpr output_type unaligned_load(iterator it) noexcept
{
Expand All @@ -104,7 +109,7 @@ inline constexpr output_type unaligned_load(iterator it) noexcept
/// size of output_type and forwards the \ref it by the size was read \warning be aware that this function is prone to
/// bugs when used in context of order of evaluation is unspecified, dont use it as function arguments, constructors
/// because \ref it is modified when evaluated
template<detail::arithmetic_or_bool output_type, typename iterator>
template<detail::trivially_copyable output_type, typename iterator>
[[nodiscard, gnu::always_inline]]
inline constexpr output_type unaligned_load_fwd(iterator & it) noexcept
{
Expand All @@ -128,17 +133,38 @@ inline constexpr output_type unaligned_load_fwd(iterator & it) noexcept
}

//---------------------------------------------------------------------------------------------------
namespace detail
{
template<
detail::trivially_copyable store_type,
detail::output_iterator_to_byte iterator,
detail::trivially_copyable input_type>
requires(std::same_as<store_type, input_type>)
[[gnu::always_inline]]
inline constexpr iterator unaligned_store(iterator it, input_type value) noexcept
{
using output_range_type = std::iter_value_t<iterator>;

struct value_buffer_type
{
std::array<output_range_type, sizeof(value)> buffer;
};

value_buffer_type store = cxx20::bit_cast<value_buffer_type>(value);
return std::copy(store.buffer.begin(), store.buffer.end(), it);
}
} // namespace detail

///\brief stores \param value at \param it location, input value type must match requested storage type
template<
detail::arithmetic_or_bool store_type,
detail::trivially_copyable store_type,
detail::output_iterator_to_byte iterator,
detail::arithmetic_or_bool input_type>
detail::trivially_copyable input_type>
requires(std::same_as<store_type, input_type>)
[[gnu::always_inline]]
inline constexpr iterator unaligned_store(iterator it, input_type value) noexcept
{
using output_range_type = std::iter_value_t<iterator>;
return std::copy_n(std::launder(reinterpret_cast<output_range_type const *>(&value)), sizeof(store_type), it);
return detail::unaligned_store<store_type>(it, value);
}

///\brief stores \param value at \param it location, input value type must match requested storage type
Expand All @@ -147,12 +173,11 @@ template<
std::size_t expected_storage_size,
detail::output_iterator_to_byte iterator,
detail::trivially_copyable input_type>
requires(std::same_as<store_type, input_type> && expected_storage_size == sizeof(store_type) && !detail::arithmetic_or_bool<store_type>)
requires(std::same_as<store_type, input_type> && expected_storage_size == sizeof(store_type))
[[gnu::always_inline]]
inline constexpr iterator unaligned_store(iterator it, input_type value) noexcept
{
using output_range_type = std::iter_value_t<iterator>;
return std::copy_n(std::launder(reinterpret_cast<output_range_type const *>(&value)), sizeof(store_type), it);
return detail::unaligned_store<store_type>(it, value);
}

//---------------------------------------------------------------------------------------------------
Expand Down
39 changes: 26 additions & 13 deletions unit_tests/unaligned_ut.cc
View file
Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,7 @@ int main()

metatests::test_result result;

"test int"_test = [&]
"test_int"_test = [&]
{
auto fn_tmpl = []<typename value_type>(value_type const *) -> metatests::test_result
{
Expand All @@ -27,6 +27,7 @@ int main()
return {};
};
result |= run_constexpr_test<traits_list>(fn_tmpl);
result |= run_consteval_test<traits_list>(fn_tmpl);
};

"test double"_test = [&]
Expand All @@ -38,10 +39,11 @@ int main()
type testv = 0.45671974353;
unaligned_store<type>(&store[1], testv);
type r = unaligned_load<type>(&store[1]);
expect(r == testv);
constexpr_test(r == testv);
return {};
};
result |= run_constexpr_test<traits_list>(fn_tmpl);
result |= run_consteval_test<traits_list>(fn_tmpl);
};

"test int64_t"_test = [&]
Expand All @@ -54,30 +56,41 @@ int main()

unaligned_store<type>(&store[1], testv);
type r = unaligned_load<type>(&store[1]);
expect(r == testv);
constexpr_test(r == testv);
return {};
};
result |= run_constexpr_test<traits_list>(fn_tmpl);
result |= run_consteval_test<traits_list>(fn_tmpl);
};

"test enum"_test = [&]
{
enum struct test_enum : uint16_t
{
one,
two,
three
};
auto fn_tmpl = []<typename value_type>(value_type const *) -> metatests::test_result
{
value_type store[128];
enum struct test_enum : uint16_t
{
one,
two,
three
};

using type = test_enum;
type testv = test_enum::two;
unaligned_store<type, 2>(&store[3], testv);
type r = unaligned_load<type, 2>(&store[3]);
expect(r == testv);
{
type testv = test_enum::three;
unaligned_store<type>(&store[3], testv);
type r = unaligned_load<type>(&store[3]);
constexpr_test(r == testv);
}
{
type testv = test_enum::two;
unaligned_store<type, 2>(&store[3], testv);
type r = unaligned_load<type, 2>(&store[3]);
constexpr_test(r == testv);
}
return {};
};
result |= run_constexpr_test<traits_list>(fn_tmpl);
result |= run_consteval_test<traits_list>(fn_tmpl);
};
}

0 comments on commit f7a06d1

Please sign in to comment.