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any: basic_any_storage, prepare for vtable-less optimizations

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skypjack
2025-10-09 15:52:43 +02:00
parent f2b8177aaf
commit f63f36a411
1 changed files with 43 additions and 31 deletions
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74
src/entt/core/any.hpp
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@@ -28,26 +28,42 @@ enum class any_request : std::uint8_t {
template<std::size_t Len, std::size_t Align>
struct basic_any_storage {
// NOLINTNEXTLINE(cppcoreguidelines-avoid-c-arrays, modernize-avoid-c-arrays)
alignas(Align) std::byte data[Len];
basic_any_storage()
: instance{} {}
basic_any_storage(const void *elem)
: instance{elem} {}
union {
const void *instance;
alignas(Align) std::byte buffer[Len];
};
};
template<std::size_t Align>
struct basic_any_storage<0u, Align> {};
struct basic_any_storage<0u, Align> {
basic_any_storage()
: instance{} {}
basic_any_storage(const void *elem)
: instance{elem} {}
const void *instance{};
};
} // namespace internal
/*! @endcond */
/**
* @brief A SBO friendly, type-safe container for single values of any type.
* @tparam Len Size of the storage reserved for the small buffer optimization.
* @tparam Len Size of the buffer reserved for the small buffer optimization.
* @tparam Align Optional alignment requirement.
*/
template<std::size_t Len, std::size_t Align>
class basic_any {
class basic_any: private internal::basic_any_storage<Len, Align> {
using request = internal::any_request;
using vtable_type = const void *(const request, const basic_any &, const void *);
using storage_type = internal::basic_any_storage<Len, Align>;
using base_type = internal::basic_any_storage<Len, Align>;
template<typename Type>
// NOLINTNEXTLINE(bugprone-sizeof-expression)
@@ -59,7 +75,7 @@ class basic_any {
const Type *elem = nullptr;
if constexpr(in_situ<Type>) {
elem = (value.mode == any_policy::embedded) ? reinterpret_cast<const Type *>(&value.storage) : static_cast<const Type *>(value.instance);
elem = (value.mode == any_policy::embedded) ? reinterpret_cast<const Type *>(&value.buffer) : static_cast<const Type *>(value.instance);
} else {
elem = static_cast<const Type *>(value.instance);
}
@@ -103,7 +119,7 @@ class basic_any {
ENTT_ASSERT(value.mode == any_policy::embedded, "Unexpected policy");
if constexpr(in_situ<Type>) {
// NOLINTNEXTLINE(bugprone-casting-through-void, bugprone-multi-level-implicit-pointer-conversion)
return ::new(&static_cast<basic_any *>(const_cast<void *>(other))->storage) Type{std::move(*const_cast<Type *>(elem))};
return ::new(&static_cast<basic_any *>(const_cast<void *>(other))->buffer) Type{std::move(*const_cast<Type *>(elem))};
}
[[fallthrough]];
case request::get:
@@ -129,33 +145,33 @@ class basic_any {
static_assert((std::is_lvalue_reference_v<Args> && ...) && (sizeof...(Args) == 1u), "Invalid arguments");
mode = std::is_const_v<std::remove_reference_t<Type>> ? any_policy::cref : any_policy::ref;
// NOLINTNEXTLINE(bugprone-multi-level-implicit-pointer-conversion)
instance = (std::addressof(args), ...);
this->instance = (std::addressof(args), ...);
} else if constexpr(in_situ<plain_type>) {
mode = any_policy::embedded;
if constexpr(std::is_aggregate_v<plain_type> && (sizeof...(Args) != 0u || !std::is_default_constructible_v<plain_type>)) {
::new(&storage) plain_type{std::forward<Args>(args)...};
::new(&this->buffer) plain_type{std::forward<Args>(args)...};
} else {
// NOLINTNEXTLINE(cppcoreguidelines-pro-bounds-array-to-pointer-decay)
::new(&storage) plain_type(std::forward<Args>(args)...);
::new(&this->buffer) plain_type(std::forward<Args>(args)...);
}
} else {
mode = any_policy::dynamic;
if constexpr(std::is_aggregate_v<plain_type> && (sizeof...(Args) != 0u || !std::is_default_constructible_v<plain_type>)) {
instance = new plain_type{std::forward<Args>(args)...};
this->instance = new plain_type{std::forward<Args>(args)...};
} else if constexpr(std::is_array_v<plain_type>) {
static_assert(sizeof...(Args) == 0u, "Invalid arguments");
instance = new plain_type[std::extent_v<plain_type>]();
this->instance = new plain_type[std::extent_v<plain_type>]();
} else {
instance = new plain_type(std::forward<Args>(args)...);
this->instance = new plain_type(std::forward<Args>(args)...);
}
}
}
}
basic_any(const basic_any &other, const any_policy pol) noexcept
: instance{other.data()},
: base_type{other.data()},
vtable{other.vtable},
descriptor{other.descriptor},
mode{pol} {}
@@ -167,7 +183,7 @@ class basic_any {
}
public:
/*! @brief Size of the internal storage. */
/*! @brief Size of the internal buffer. */
static constexpr auto length = Len;
/*! @brief Alignment requirement. */
static constexpr auto alignment = Align;
@@ -184,7 +200,7 @@ public:
*/
template<typename Type, typename... Args>
explicit basic_any(std::in_place_type_t<Type>, Args &&...args)
: instance{} {
: base_type{} {
initialize<Type>(std::forward<Args>(args)...);
}
@@ -195,7 +211,7 @@ public:
*/
template<typename Type>
explicit basic_any(std::in_place_t, Type *value)
: instance{} {
: base_type{} {
static_assert(!std::is_const_v<Type> && !std::is_void_v<Type>, "Non-const non-void pointer required");
if(value != nullptr) {
@@ -229,18 +245,18 @@ public:
* @param other The instance to move from.
*/
basic_any(basic_any &&other) noexcept
: instance{},
: base_type{},
vtable{other.vtable},
descriptor{other.descriptor},
mode{other.mode} {
if(other.mode == any_policy::embedded) {
other.vtable(request::move, other, this);
} else if(other.mode != any_policy::empty) {
instance = std::exchange(other.instance, nullptr);
this->instance = std::exchange(other.instance, nullptr);
}
}
/*! @brief Frees the internal storage, whatever it means. */
/*! @brief Frees the internal buffer, whatever it means. */
~basic_any() {
destroy_if_owner();
}
@@ -274,7 +290,7 @@ public:
if(other.mode == any_policy::embedded) {
other.vtable(request::move, other, this);
} else if(other.mode != any_policy::empty) {
instance = std::exchange(other.instance, nullptr);
this->instance = std::exchange(other.instance, nullptr);
}
vtable = other.vtable;
@@ -349,7 +365,7 @@ public:
* @return An opaque pointer the contained instance, if any.
*/
[[nodiscard]] const void *data() const noexcept {
return (mode == any_policy::embedded) ? vtable(request::get, *this, nullptr) : instance;
return (mode == any_policy::embedded) ? vtable(request::get, *this, nullptr) : this->instance;
}
/**
@@ -445,7 +461,7 @@ public:
void reset() {
destroy_if_owner();
instance = nullptr;
this->instance = nullptr;
vtable = nullptr;
descriptor = &type_id<void>;
mode = any_policy::empty;
@@ -511,10 +527,6 @@ public:
}
private:
union {
const void *instance;
storage_type storage;
};
vtable_type *vtable{};
const type_info &(*descriptor)() noexcept {&type_id<void>};
any_policy mode{any_policy::empty};
@@ -523,7 +535,7 @@ private:
/**
* @brief Performs type-safe access to the contained object.
* @tparam Type Type to which conversion is required.
* @tparam Len Size of the storage reserved for the small buffer optimization.
* @tparam Len Size of the buffer reserved for the small buffer optimization.
* @tparam Align Alignment requirement.
* @param data Target any object.
* @return The element converted to the requested type.
@@ -581,7 +593,7 @@ template<typename Type, std::size_t Len, std::size_t Align>
/**
* @brief Constructs a wrapper from a given type, passing it all arguments.
* @tparam Type Type of object to use to initialize the wrapper.
* @tparam Len Size of the storage reserved for the small buffer optimization.
* @tparam Len Size of the buffer reserved for the small buffer optimization.
* @tparam Align Optional alignment requirement.
* @tparam Args Types of arguments to use to construct the new instance.
* @param args Parameters to use to construct the instance.
@@ -594,7 +606,7 @@ template<typename Type, std::size_t Len = basic_any<>::length, std::size_t Align
/**
* @brief Forwards its argument and avoids copies for lvalue references.
* @tparam Len Size of the storage reserved for the small buffer optimization.
* @tparam Len Size of the buffer reserved for the small buffer optimization.
* @tparam Align Optional alignment requirement.
* @tparam Type Type of argument to use to construct the new instance.
* @param value Parameter to use to construct the instance.