Variant< Ts > 模板结构体 参考

Implementation of a variant container (similar to C++17's std::variant). 更多...

#include <variant.h>

类 Variant< Ts > 继承关系图:

Public 成员函数
	Variant ()
	The default constructor 更多...
	Variant (const Variant< Ts... > &src)
	The copy constructor 更多...
	Variant (Variant< Ts... > &&src)
	The move constructor 更多...
Variant< Ts... > &	operator= (const Variant< Ts... > &src)
	The copy assignment operator 更多...
Variant< Ts... > &	operator= (Variant< Ts... > &&src)
	The move assignment operator 更多...
	~Variant ()
	The destructor 更多...
template<uint8_t index>
constexpr bool	is () const
	Returns true iff the variant container holds a specific type. 更多...
constexpr bool	valid () const
	Returns true iff the Variant holds a valid type. 更多...
void	invalidate ()
	Invalidate the variant. Will destroy any object that is held. 更多...
constexpr uint8_t	index () const
	Returns the index of the type held by this variant, or invalid_id() if the variant does not hold any type (i.e. 更多...
template<uint8_t index, typename... Args>
void	set (Args &&... args)
	Replaces the contents of the variant container by constructing a type T calling the constructor with Args 更多...
template<uint8_t index>
Type< index > &	get ()
	Return a non-constant reference to the value held by the variant container. 更多...
template<uint8_t index>
const Type< index > &	get () const
	Returns a constant reference to the value held by the variant container. 更多...

Private 类型
using	Data = typename std::aligned_storage< data_size, data_align >::type
	the data type for the Variant's internal memory 更多...
using	HelperT = details::HelperT< Ts... >
	a short hand name for the helper class 更多...
template<uint8_t index>
using	Type = typename VariantType< index, Ts... >::type

静态 Private 成员函数
static uint8_t	invalid_id ()
	The id that represents an invalid type 更多...

Private 属性
Data	m_data
	the actual data 更多...
uint8_t	m_id
	a unique identifier for the type held by this variant 更多...

静态 Private 属性
static const size_t	data_size = details::TMax<sizeof(Ts)...>::value
	constant respresenting the maximum size that can hold all types in the template list 更多...
static const size_t	data_align = details::TMax<alignof(Ts)...>::value
	constant respresenting the maximum alignment requirement for all types in the template list 更多...

详细描述

template<typename... Ts>
struct Variant< Ts >

Implementation of a variant container (similar to C++17's std::variant).

It can hold either no instances (e.g. initially or after calling invalidate()), or hold exactly one instance of an object (after calling set()) whose type is one of the variant's template parameters. Each parameter has an index, the first parameter has index 0. It behaves similar to a C union, in that the memory of all possible object types is shared, but unlike a C union it does allow C++ objects with constructors and destructors to be stored and knows what type is stored.

在文件 variant.h 第 176 行定义.

成员类型定义说明

Data

template<typename... Ts>

using Variant< Ts >::Data = typename std::aligned_storage<data_size, data_align>::type

private

the data type for the Variant's internal memory

在文件 variant.h 第 184 行定义.

HelperT

template<typename... Ts>

using Variant< Ts >::HelperT = details::HelperT<Ts...>

private

a short hand name for the helper class

在文件 variant.h 第 187 行定义.

Type

template<typename... Ts>

template<uint8_t index>

using Variant< Ts >::Type = typename VariantType<index,Ts...>::type

private

在文件 variant.h 第 190 行定义.

构造及析构函数说明

Variant() [1/3]

template<typename... Ts>

Variant< Ts >::Variant ( )

inline

The default constructor

在文件 variant.h 第 202 行定义.

              : m_id(invalid_id())
    {
    }

Variant() [2/3]

template<typename... Ts>

Variant< Ts >::Variant ( const Variant< Ts... > &  src )

inline

The copy constructor

在文件 variant.h 第 207 行定义.

                                       : m_id(src.m_id)
    {
      HelperT::copy(src.m_id, &src.m_data, &m_data);
    }

Variant() [3/3]

template<typename... Ts>

Variant< Ts >::Variant ( Variant< Ts... > &&  src )

inline

The move constructor

在文件 variant.h 第 213 行定义.

                                  : m_id(src.m_id)
    {
      HelperT::move(src.m_id, &src.m_data, &m_data);
    }

~Variant()

template<typename... Ts>

Variant< Ts >::~Variant ( )

inline

The destructor

在文件 variant.h 第 244 行定义.

    {
      HelperT::destroy(m_id, &m_data);
    }

成员函数说明

get() [1/2]

template<typename... Ts>

template<uint8_t index>

Type<index>& Variant< Ts >::get ( )

inline

Return a non-constant reference to the value held by the variant container.

异常

std::bad_cast()

if called on a variant container that does not hold an instance of the type of the variant at index.

在文件 variant.h 第 285 行定义.

    {
      if (m_id != index) throw std::bad_cast();
      return *reinterpret_cast<Type<index>*>(&m_data);
    }

被这些函数引用 TemplateVariant::call(), TemplateVariant::operator==(), TemplateVariant::toBool(), TemplateVariant::toInt(), TemplateVariant::toList(), TemplateVariant::toString() , 以及 TemplateVariant::toStruct().

get() [2/2]

template<typename... Ts>

template<uint8_t index>

const Type<index>& Variant< Ts >::get ( ) const

inline

Returns a constant reference to the value held by the variant container.

异常

std::bad_cast()

if called on a variant container that does not hold an instance of the type of the variant at index.

在文件 variant.h 第 295 行定义.

    {
      if (m_id != index) throw std::bad_cast();
      return *reinterpret_cast<const Type<index>*>(&m_data);
    }

index()

template<typename... Ts>

constexpr uint8_t Variant< Ts >::index ( ) const

inlineconstexpr

Returns the index of the type held by this variant, or invalid_id() if the variant does not hold any type (i.e.

valid() returns false).

在文件 variant.h 第 266 行定义.

{ return m_id; }

被这些函数引用 Variant< bool, int, QCString, TemplateStructIntfPtr, TemplateListIntfPtr, FunctionDelegate, TemplateStructIntfWeakPtr >::get(), Variant< bool, int, QCString, TemplateStructIntfPtr, TemplateListIntfPtr, FunctionDelegate, TemplateStructIntfWeakPtr >::is(), Variant< bool, int, QCString, TemplateStructIntfPtr, TemplateListIntfPtr, FunctionDelegate, TemplateStructIntfWeakPtr >::set() , 以及 TemplateVariant::type().

invalid_id()

template<typename... Ts>

static uint8_t Variant< Ts >::invalid_id ( )

inlinestaticprivate

The id that represents an invalid type

在文件 variant.h 第 193 行定义.

{ return 255; }

被这些函数引用 Variant< bool, int, QCString, TemplateStructIntfPtr, TemplateListIntfPtr, FunctionDelegate, TemplateStructIntfWeakPtr >::invalidate() , 以及 Variant< bool, int, QCString, TemplateStructIntfPtr, TemplateListIntfPtr, FunctionDelegate, TemplateStructIntfWeakPtr >::valid().

invalidate()

template<typename... Ts>

void Variant< Ts >::invalidate ( )

inline

Invalidate the variant. Will destroy any object that is held.

在文件 variant.h 第 258 行定义.

    {
      HelperT::destroy(m_id,&m_data);
      m_id = invalid_id();
    }

is()

template<typename... Ts>

template<uint8_t index>

constexpr bool Variant< Ts >::is ( ) const

inlineconstexpr

Returns true iff the variant container holds a specific type.

模板参数

T	the type to search for.

在文件 variant.h 第 252 行定义.

{ return m_id==index; }

被这些函数引用 TemplateVariant::isBool(), TemplateVariant::isFunction(), TemplateVariant::isInt(), TemplateVariant::isList(), TemplateVariant::isString(), TemplateVariant::isStruct() , 以及 TemplateVariant::isWeakStruct().

operator=() [1/2]

template<typename... Ts>

Variant<Ts...>& Variant< Ts >::operator= ( const Variant< Ts... > &  src )

inline

The copy assignment operator

在文件 variant.h 第 219 行定义.

    {
      if (this!=&src) // prevent self assignment
      {
        // destroy the old value
        if (valid()) HelperT::destroy(m_id,&m_data);
        // and copy over the new one
        m_id = src.m_id;
        HelperT::copy(src.m_id, &src.m_data, &m_data);
      }
      return *this;
    }

operator=() [2/2]

template<typename... Ts>

Variant<Ts...>& Variant< Ts >::operator= ( Variant< Ts... > &&  src )

inline

The move assignment operator

在文件 variant.h 第 233 行定义.

    {
      // destroy the old value
      if (valid()) HelperT::destroy(m_id,&m_data);
      // and move in the new one
      m_id = src.m_id;
      HelperT::move(src.m_id, &src.m_data, &m_data);
      return *this;
    }

set()

template<typename... Ts>

template<uint8_t index, typename... Args>

void Variant< Ts >::set ( Args &&...  args )

inline

Replaces the contents of the variant container by constructing a type T calling the constructor with Args

模板参数

index	the type to make the variant hold an instance of.
Args	The arguments types to pass to the constructor of T.

参数

args	The argument values

在文件 variant.h 第 274 行定义.

    {
      HelperT::destroy(m_id, &m_data);
      m_id = index;
      new (&m_data) Type<index>(std::forward<Args>(args)...);
    }

被这些函数引用 TemplateVariant::TemplateVariant().

valid()

template<typename... Ts>

constexpr bool Variant< Ts >::valid ( ) const

inlineconstexpr

Returns true iff the Variant holds a valid type.

在文件 variant.h 第 255 行定义.

{ return m_id!=invalid_id(); }

被这些函数引用 TemplateVariant::isValid(), Variant< bool, int, QCString, TemplateStructIntfPtr, TemplateListIntfPtr, FunctionDelegate, TemplateStructIntfWeakPtr >::operator=() , 以及 TemplateVariant::operator==().

类成员变量说明

data_align

template<typename... Ts>

const size_t Variant< Ts >::data_align = details::TMax<alignof(Ts)...>::value

staticprivate

constant respresenting the maximum alignment requirement for all types in the template list

在文件 variant.h 第 181 行定义.

data_size

template<typename... Ts>

const size_t Variant< Ts >::data_size = details::TMax<sizeof(Ts)...>::value

staticprivate

constant respresenting the maximum size that can hold all types in the template list

在文件 variant.h 第 179 行定义.

m_data

template<typename... Ts>

Data Variant< Ts >::m_data

private

the actual data

在文件 variant.h 第 196 行定义.

被这些函数引用 Variant< bool, int, QCString, TemplateStructIntfPtr, TemplateListIntfPtr, FunctionDelegate, TemplateStructIntfWeakPtr >::get(), Variant< bool, int, QCString, TemplateStructIntfPtr, TemplateListIntfPtr, FunctionDelegate, TemplateStructIntfWeakPtr >::invalidate(), Variant< bool, int, QCString, TemplateStructIntfPtr, TemplateListIntfPtr, FunctionDelegate, TemplateStructIntfWeakPtr >::operator=(), Variant< bool, int, QCString, TemplateStructIntfPtr, TemplateListIntfPtr, FunctionDelegate, TemplateStructIntfWeakPtr >::set(), Variant< bool, int, QCString, TemplateStructIntfPtr, TemplateListIntfPtr, FunctionDelegate, TemplateStructIntfWeakPtr >::Variant() , 以及 Variant< bool, int, QCString, TemplateStructIntfPtr, TemplateListIntfPtr, FunctionDelegate, TemplateStructIntfWeakPtr >::~Variant().

m_id

template<typename... Ts>

uint8_t Variant< Ts >::m_id

private

a unique identifier for the type held by this variant

在文件 variant.h 第 198 行定义.

被这些函数引用 Variant< bool, int, QCString, TemplateStructIntfPtr, TemplateListIntfPtr, FunctionDelegate, TemplateStructIntfWeakPtr >::get(), Variant< bool, int, QCString, TemplateStructIntfPtr, TemplateListIntfPtr, FunctionDelegate, TemplateStructIntfWeakPtr >::index(), Variant< bool, int, QCString, TemplateStructIntfPtr, TemplateListIntfPtr, FunctionDelegate, TemplateStructIntfWeakPtr >::invalidate(), Variant< bool, int, QCString, TemplateStructIntfPtr, TemplateListIntfPtr, FunctionDelegate, TemplateStructIntfWeakPtr >::is(), Variant< bool, int, QCString, TemplateStructIntfPtr, TemplateListIntfPtr, FunctionDelegate, TemplateStructIntfWeakPtr >::operator=(), Variant< bool, int, QCString, TemplateStructIntfPtr, TemplateListIntfPtr, FunctionDelegate, TemplateStructIntfWeakPtr >::set(), Variant< bool, int, QCString, TemplateStructIntfPtr, TemplateListIntfPtr, FunctionDelegate, TemplateStructIntfWeakPtr >::valid(), Variant< bool, int, QCString, TemplateStructIntfPtr, TemplateListIntfPtr, FunctionDelegate, TemplateStructIntfWeakPtr >::Variant() , 以及 Variant< bool, int, QCString, TemplateStructIntfPtr, TemplateListIntfPtr, FunctionDelegate, TemplateStructIntfWeakPtr >::~Variant().

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该结构体的文档由以下文件生成:

• src/variant.h