#include "comms/field/Variant.h"

Detailed Description

template<typename TFieldBase, typename TMembers, typename... TOptions>
class comms::field::Variant< TFieldBase, TMembers, TOptions >

Defines a "variant" field, that can contain any of the provided ones.

The Variant object contains uninitialised buffer that can fit any of the provided field types (as second template parameter). At any given point of time this space can be initialised and used to contain at most one of the specified field types. It resembles a classic union, but disallows set value of one field type and read it as other. The Variant field abstraction provides expected single field API functions, such as length(), read(), write(), valid().

Refer to Variant Fields for tutorial and usage examples.

Template Parameters

TFieldBase	Base class for this field, expected to be a variant of comms::Field.
TMembers	All supported field types bundled together in std::tuple. This parameter is used to determine the size of the contained buffer to be able to fit any of the specified types.
TOptions	Zero or more options that modify/refine default behaviour of the field. Supported options are: comms::option::def::DefaultValueInitialiser - All wrapped fields may specify their independent default value initialisers. It is also possible to provide initialiser for the Variant field which will set appropriate values to the fields based on some internal logic. comms::option::def::DefaultVariantIndex - By default the Variant field doesn't have any valid contents. This option may be used to specify the index of the default member field. comms::option::def::HasCustomRead - Mark field to have custom read functionality comms::option::def::HasCustomRefresh - Mark field to have custom refresh functionality. comms::option::def::EmptySerialization - Force empty serialization. comms::option::def::VersionStorage - Add version storage. comms::option::def::FieldType - Set actual field type comms::option::def::VariantHasCustomResetOnDestruct - avoid calling default reset() on destruction, assume it is called by the extending class destructor. comms::option::def::HasVersionDependentMembers

See also: COMMS_VARIANT_MEMBERS_NAMES(); COMMS_VARIANT_MEMBERS_ACCESS(); COMMS_VARIANT_MEMBERS_ACCESS_NOTEMPLATE()

Inheritance diagram for comms::field::Variant< TFieldBase, TMembers, TOptions >:

Public Types
using	CommsTag = typename BaseImpl::CommsTag
	Tag indicating type of the field.

using	Endian = typename BaseImpl::Endian
	Endian used for serialisation.

using	FieldBase = TFieldBase
	Base class provided in the first template parameter.

using	FieldType = typename ParsedOptions::FieldType
	Type of actual extending field specified via comms::option::def::FieldType.

using	Members = typename BaseImpl::Members
	All the supported types.

using	ParsedOptions = details::OptionsParser< TOptions... >
	All the options provided to this class bundled into struct.

using	ValueType = typename BaseImpl::ValueType
	Value type.

using	VersionType = typename BaseImpl::VersionType
	Version type.

Public Member Functions
	Variant ()=default
	Default constructor.

	Variant (const ValueType &val)
	Constructor.

	Variant (ValueType &&val)
	Constructor.

template<std::size_t TIdx>
std::tuple_element< TIdx, Members >::type &	accessField ()
	Access already constructed field at specifed index (known at compile time).

template<std::size_t TIdx>
const std::tuple_element< TIdx, Members >::type &	accessField () const
	Access already constructed field at specifed index (known at compile time).

bool	canWrite () const
	Check of whether the field has a consistent value for writing.

std::size_t	currentField () const
	Get index of the current field (within the Members tuple).

template<typename TFunc >
void	currentFieldExec (TFunc &&func)
	Execute provided function object with current field as parameter.

template<typename TFunc >
void	currentFieldExec (TFunc &&func) const
	Execute provided function object with current field as parameter (const variant).

bool	currentFieldValid () const
	Check whether the field contains a valid instance of other field.

template<std::size_t TIdx>
void	deinitField ()
	Destruct previously initialised (via initField()) contained field.

const ValueType &	getValue () const
	Get value.

VersionType	getVersion () const
	Get version of the field.

template<std::size_t TIdx, typename... TArgs>
std::tuple_element< TIdx, Members >::type &	initField (TArgs &&... args)
	Construct and initialise specified contained field in the internal buffer.

std::size_t	length () const
	Get length required to serialise contained fields.

template<typename TIter >
ErrorStatus	read (TIter &iter, std::size_t size)
	Read field value from input data sequence.

template<typename TIter >
void	readNoStatus (TIter &iter)=delete
	Read operation without error check and status report is not supported.

bool	refresh ()
	Refresh the field's value.

void	reset ()
	Invalidate current state.

void	selectField (std::size_t idx)
	Select type of the variant field.

template<typename U >
void	setValue (U &&val)
	Set value.

bool	setVersion (VersionType version)
	Default implementation of version update.

bool	valid () const
	Check validity of all the contained field.

ValueType &	value ()
	Get access to the internal storage buffer.

const ValueType &	value () const
	Get access to the internal storage buffer.

template<typename TIter >
ErrorStatus	write (TIter &iter, std::size_t size) const
	Write current field value to output data sequence.

template<typename TIter >
void	writeNoStatus (TIter &iter) const
	Write current field value to output data sequence without error check and status report.

Static Public Member Functions
static constexpr bool	canWrite ()
	Default check of whether the field has a consistent value for writing.

static constexpr bool	hasEmptySerialization ()
	Compile time inquiry of whether comms::option::def::EmptySerialization option has been used.

static constexpr bool	hasFailOnInvalid ()
	Compile time inquiry of whether comms::option::def::FailOnInvalid option has been used.

static constexpr bool	hasFieldType ()
	Compile time inquiry of whether comms::option::def::FieldType option has been used.

static constexpr bool	hasIgnoreInvalid ()
	Compile time inquiry of whether comms::option::def::IgnoreInvalid option has been used.

static constexpr bool	hasNonDefaultRefresh ()
	Compile time check if this class has non-default refresh functionality.

static constexpr bool	hasReadNoStatus ()
	Compile time check of whether the field has proper readNoStatus() member function.

static constexpr bool	hasVarLength ()
	Default check of whether the field has variable length definition via comms::option::def::VarLength option.

static constexpr bool	hasWriteNoStatus ()
	Compile time check of whether the field has proper writeNoStatus() member function.

static constexpr bool	isVersionDependent ()
	Compile time check if this class is version dependent.

static constexpr std::size_t	maxLength ()
	Get maximal length that is required to serialise all possible contained fields.

static constexpr std::size_t	minLength ()
	Get minimal length that is required to serialise all possible contained fields.

static constexpr bool	valid ()
	Default validity check.

Static Protected Member Functions
template<typename T , typename TIter >
static T	readData (TIter &iter)
	Read data from input buffer.

template<typename T , std::size_t TSize, typename TIter >
static T	readData (TIter &iter)
	Read partial data from input buffer.

template<typename T , typename TIter >
static void	writeData (T value, TIter &iter)
	Write data into the output buffer.

template<std::size_t TSize, typename T , typename TIter >
static void	writeData (T value, TIter &iter)
	Write partial data into the output buffer.

Related Symbols
(Note that these are not member symbols.)
#define	COMMS_VARIANT_MEMBERS_ACCESS(...)
	Add convenience access enum and functions to the members of comms::field::Variant field.

#define	COMMS_VARIANT_MEMBERS_ACCESS_NOTEMPLATE(...)
	Similar to COMMS_VARIANT_MEMBERS_ACCESS(), but dedicated for non-template classes.

#define	COMMS_VARIANT_MEMBERS_NAMES(...)
	Provide names for member fields of comms::field::Variant field.

template<typename T >
constexpr bool	isVariant ()
	Compile time check function of whether a provided type is any variant of comms::field::Variant.

template<typename TFieldBase , typename TMembers , typename... TOptions>
bool	operator!= (const Variant< TFieldBase, TMembers, TOptions... > &field1, const Variant< TFieldBase, TMembers, TOptions... > &field2)
	Non-equality comparison operator.

template<typename TFieldBase , typename TMembers , typename... TOptions>
bool	operator< (const Variant< TFieldBase, TMembers, TOptions... > &field1, const Variant< TFieldBase, TMembers, TOptions... > &field2)
	Order comparison operator.

template<typename TFieldBase , typename TMembers , typename... TOptions>
bool	operator== (const Variant< TFieldBase, TMembers, TOptions... > &field1, const Variant< TFieldBase, TMembers, TOptions... > &field2)
	Equality comparison operator.

template<typename TFieldBase , typename TMembers , typename... TOptions>
const Variant< TFieldBase, TMembers, TOptions... > &	toFieldBase (const Variant< TFieldBase, TMembers, TOptions... > &field)
	Upcast type of the field definition to its parent comms::field::Variant type in order to have access to its internal types.

template<typename TFieldBase , typename TMembers , typename... TOptions>
Variant< TFieldBase, TMembers, TOptions... > &	toFieldBase (Variant< TFieldBase, TMembers, TOptions... > &field)
	Upcast type of the field definition to its parent comms::field::Variant type in order to have access to its internal types.

Member Typedef Documentation

◆ FieldType

template<typename TFieldBase , typename TMembers , typename... TOptions>

using comms::field::Variant< TFieldBase, TMembers, TOptions >::FieldType = typename ParsedOptions::FieldType

Type of actual extending field specified via comms::option::def::FieldType.

void if comms::option::def::FieldType hasn't been applied.

◆ Members

template<typename TFieldBase , typename TMembers , typename... TOptions>

using comms::field::Variant< TFieldBase, TMembers, TOptions >::Members = typename BaseImpl::Members

All the supported types.

Same as TMemebers template argument, i.e. it is std::tuple of all the wrapped fields.

◆ ValueType

template<typename TFieldBase , typename TMembers , typename... TOptions>

using comms::field::Variant< TFieldBase, TMembers, TOptions >::ValueType = typename BaseImpl::ValueType

Value type.

Type of the internal buffer used to store contained field, should not be used in normal operation.

Constructor & Destructor Documentation

◆ Variant()

template<typename TFieldBase , typename TMembers , typename... TOptions>

comms::field::Variant< TFieldBase, TMembers, TOptions >::Variant ( )

default

Default constructor.

Invokes default constructor of every wrapped field

Member Function Documentation

◆ accessField() [1/2]

template<typename TFieldBase , typename TMembers , typename... TOptions>

template<std::size_t TIdx>

std::tuple_element< TIdx, Members >::type & comms::field::Variant< TFieldBase, TMembers, TOptions >::accessField ( )

Access already constructed field at specifed index (known at compile time).

Use this function to get a reference to the contained field type

Template Parameters

TIdx	Index of the field type witin the Members tuple.

Returns: Reference to the contained field.

Precondition: currentField() == TIdx

comms::field::Variant::currentField
std::size_t currentField() const
Get index of the current field (within the Members tuple).
Definition Variant.h:305

◆ accessField() [2/2]

template<typename TFieldBase , typename TMembers , typename... TOptions>

template<std::size_t TIdx>

const std::tuple_element< TIdx, Members >::type & comms::field::Variant< TFieldBase, TMembers, TOptions >::accessField ( ) const

Access already constructed field at specifed index (known at compile time).

Use this function to get a const reference to the contained field type.

Template Parameters

TIdx	Index of the field type witin the Members tuple.

Returns: Const reference to the contained field.

Precondition: currentField() == TIdx

◆ canWrite()

template<typename... TOptions>

static constexpr bool comms::Field< TOptions >::canWrite ( )

staticconstexprinherited

Default check of whether the field has a consistent value for writing.

Returns: Always true.

◆ currentField()

template<typename TFieldBase , typename TMembers , typename... TOptions>

std::size_t comms::field::Variant< TFieldBase, TMembers, TOptions >::currentField ( ) const

Get index of the current field (within the Members tuple).

If the Variant field doesn't contain any valid field, the returned index is equivalent to size of the Members tuple.

◆ currentFieldExec() [1/2]

template<typename TFieldBase , typename TMembers , typename... TOptions>

template<typename TFunc >

void comms::field::Variant< TFieldBase, TMembers, TOptions >::currentFieldExec ( TFunc && func )

Execute provided function object with current field as parameter.

The provided function object must define all the public operator() member functions to handle all possible types.

struct MyFunc
{
    template <std::size_t TIdx>
    void operator()(Type1& field) {...}
 
    template <std::size_t TIdx>
    void operator()(Type2& field) {...}
    ...
}

NOTE, that every operator() is expecting to receive an index of the type within the holding tuple as a template parameter. If the index information is not needed it may be either ignored or static_assert-ed upon.

The operator() may also receive a member field type as a template parameter.

struct MyFunc
{
    template <std::size_t TIdx, typename TField>
    void operator()(TField& field)
    {
        ... // do somethign with the field
    }
}

The TField will be the actual type of the contained field. If the Variant field doesn't contain any valid field, the functor will NOT be called.

◆ currentFieldExec() [2/2]

template<typename TFieldBase , typename TMembers , typename... TOptions>

template<typename TFunc >

void comms::field::Variant< TFieldBase, TMembers, TOptions >::currentFieldExec ( TFunc && func ) const

Execute provided function object with current field as parameter (const variant).

Similar to other currentFieldExec() variant, but with const. Note, the constness of the parameter.

struct MyFunc
{
    template <std::size_t TIdx, typename TField>
    void operator()(const TField& field)
    {
        ... // do somethign with the field
    }
}

The TField will be the actual type of the contained field. If the Variant field doesn't contain any valid field, the functor will NOT be called.

◆ currentFieldValid()

template<typename TFieldBase , typename TMembers , typename... TOptions>

bool comms::field::Variant< TFieldBase, TMembers, TOptions >::currentFieldValid ( ) const

Check whether the field contains a valid instance of other field.

Returns true if and only if currentField() returns a valid index inside the Members tuple.

◆ deinitField()

template<typename TFieldBase , typename TMembers , typename... TOptions>

template<std::size_t TIdx>

void comms::field::Variant< TFieldBase, TMembers, TOptions >::deinitField ( )

Destruct previously initialised (via initField()) contained field.

Template Parameters

TIdx	Index of the field type witin the Members tuple.

Precondition: The field must contain an expected member field
assert(currentField() == TIdx);

◆ getValue()

template<typename TFieldBase , typename TMembers , typename... TOptions>

const ValueType & comms::field::Variant< TFieldBase, TMembers, TOptions >::getValue ( ) const

Get value.

Should not be used in normal operation

◆ getVersion()

template<typename TFieldBase , typename TMembers , typename... TOptions>

VersionType comms::field::Variant< TFieldBase, TMembers, TOptions >::getVersion ( ) const

Get version of the field.

Exists only if comms::option::def::VersionStorage option has been provided and/or any of the member fields is version dependent.

◆ hasVarLength()

template<typename... TOptions>

static constexpr bool comms::Field< TOptions >::hasVarLength ( )

staticconstexprinherited

Default check of whether the field has variable length definition via comms::option::def::VarLength option.

Returns: Always false.

◆ initField()

template<typename TFieldBase , typename TMembers , typename... TOptions>

template<std::size_t TIdx, typename... TArgs>

std::tuple_element< TIdx, Members >::type & comms::field::Variant< TFieldBase, TMembers, TOptions >::initField ( TArgs &&... args )

Construct and initialise specified contained field in the internal buffer.

If the field already contains a valid field it must be cleared via explicit deinitField() or reset() calls.

Template Parameters

TIdx	Index of the field type witin the Members tuple.
TArgs	Types of the agurments for the field's constructor

Parameters

[in] args Arguments for the constructed field.

Precondition: The field must NOT contain any other member field
assert(!currentFieldValid());

comms::field::Variant::currentFieldValid
bool currentFieldValid() const
Check whether the field contains a valid instance of other field.
Definition Variant.h:443

Returns: Reference to the constructed field.

◆ length()

template<typename TFieldBase , typename TMembers , typename... TOptions>

std::size_t comms::field::Variant< TFieldBase, TMembers, TOptions >::length ( ) const

Get length required to serialise contained fields.

If the field doesn't contain a valid instance of other field, the reported length is 0, otherwise the length of the contained field is reported.

Returns: Number of bytes it will take to serialise the field value.

◆ maxLength()

template<typename TFieldBase , typename TMembers , typename... TOptions>

static constexpr std::size_t comms::field::Variant< TFieldBase, TMembers, TOptions >::maxLength ( )

staticconstexpr

Get maximal length that is required to serialise all possible contained fields.

Returns: Maximal number of bytes required serialise the field value.

◆ minLength()

template<typename TFieldBase , typename TMembers , typename... TOptions>

static constexpr std::size_t comms::field::Variant< TFieldBase, TMembers, TOptions >::minLength ( )

staticconstexpr

Get minimal length that is required to serialise all possible contained fields.

Returns: Always returns 0.

◆ read()

template<typename TFieldBase , typename TMembers , typename... TOptions>

template<typename TIter >

ErrorStatus comms::field::Variant< TFieldBase, TMembers, TOptions >::read	(	TIter &	iter,
		std::size_t	size
	)

Read field value from input data sequence.

Invokes read() member function over every possible field in order of definition until comms::ErrorStatus::Success is returned.

Parameters

[in,out]	iter	Iterator to read the data.
[in]	size	Number of bytes available for reading.

Returns: Status of read operation.

Postcondition: Iterator is advanced.

◆ readData() [1/2]

template<typename... TOptions>

template<typename T , typename TIter >

static T comms::Field< TOptions >::readData ( TIter & iter )

staticprotectedinherited

Read data from input buffer.

Use this function to read data from the intput buffer maintained by the caller. The endianness of the data will be as specified in options of the class.

Template Parameters

T	Return type
TIter	Type of input iterator

Parameters

[in,out] iter Input iterator.

Returns: The integral type value.

Precondition: TSize <= sizeof(T); The iterator must be valid and can be successfully dereferenced and incremented at least sizeof(T) times.

Postcondition: The iterator is advanced.

Note: Thread safety: Safe for distinct stream buffers, unsafe otherwise.

◆ readData() [2/2]

template<typename... TOptions>

template<typename T , std::size_t TSize, typename TIter >

static T comms::Field< TOptions >::readData ( TIter & iter )

staticprotectedinherited

Read partial data from input buffer.

Use this function to read data from the intput buffer maintained by the caller. The endianness of the data will be as specified in options of the class.

Template Parameters

T	Return type
TSize	number of bytes to read
TIter	Type of input iterator

Parameters

[in,out] iter Input iterator.

Returns: The integral type value.

Precondition: TSize <= sizeof(T); The iterator must be valid and can be successfully dereferenced and incremented at least TSize times.

Postcondition: The internal pointer of the stream buffer is advanced.

Note: Thread safety: Safe for distinct stream buffers, unsafe otherwise.

◆ refresh()

template<typename TFieldBase , typename TMembers , typename... TOptions>

bool comms::field::Variant< TFieldBase, TMembers, TOptions >::refresh ( )

Refresh the field's value.

Invokes refresh() member function of the current field if such exists, otherwise returns false.

Returns: true if the value has been updated, false otherwise

◆ reset()

template<typename TFieldBase , typename TMembers , typename... TOptions>

void comms::field::Variant< TFieldBase, TMembers, TOptions >::reset ( )

Invalidate current state.

Destructs currently contained field if such exists.

◆ selectField()

template<typename TFieldBase , typename TMembers , typename... TOptions>

void comms::field::Variant< TFieldBase, TMembers, TOptions >::selectField ( std::size_t idx )

Select type of the variant field.

If the same index has been selected before, the function does nothing, otherwise the currently selected member field is destructed, and the new one is default constructed.
If provided index is equal or exceeds the size of the Members tuple, no new field is constructed.

Parameters

[in] idx Index of the type within Members tuple.

◆ setValue()

template<typename TFieldBase , typename TMembers , typename... TOptions>

template<typename U >

void comms::field::Variant< TFieldBase, TMembers, TOptions >::setValue ( U && val )

Set value.

Should not be used in normal operation

◆ setVersion()

template<typename TFieldBase , typename TMembers , typename... TOptions>

bool comms::field::Variant< TFieldBase, TMembers, TOptions >::setVersion ( VersionType version )

Default implementation of version update.

Returns: true in case the field contents have changed, false otherwise

◆ valid() [1/2]

template<typename... TOptions>

static constexpr bool comms::Field< TOptions >::valid ( )

staticconstexprinherited

Default validity check.

Always returns true, can be overriden by the derived class

Returns: Always true

◆ valid() [2/2]

template<typename TFieldBase , typename TMembers , typename... TOptions>

bool comms::field::Variant< TFieldBase, TMembers, TOptions >::valid ( ) const

Check validity of all the contained field.

Returns false if doesn't contain any field.

◆ value() [1/2]

template<typename TFieldBase , typename TMembers , typename... TOptions>

ValueType & comms::field::Variant< TFieldBase, TMembers, TOptions >::value ( )

Get access to the internal storage buffer.

Should not be used in normal operation.

◆ value() [2/2]

template<typename TFieldBase , typename TMembers , typename... TOptions>

const ValueType & comms::field::Variant< TFieldBase, TMembers, TOptions >::value ( ) const

Get access to the internal storage buffer.

Should not be used in normal operation.

◆ write()

template<typename TFieldBase , typename TMembers , typename... TOptions>

template<typename TIter >

ErrorStatus comms::field::Variant< TFieldBase, TMembers, TOptions >::write	(	TIter &	iter,
		std::size_t	size
	)		const

Write current field value to output data sequence.

Invokes write() member function of the contained field if such exists. If the Variant field doesn't contain any valid field, the function doesn't advance the iterator, but returns comms::ErrorStatus::Success.

Parameters

[in,out]	iter	Iterator to write the data.
[in]	size	Maximal number of bytes that can be written.

Returns: Status of write operation.

Postcondition: Iterator is advanced.

◆ writeData() [1/2]

template<typename... TOptions>

template<typename T , typename TIter >

static void comms::Field< TOptions >::writeData	(	T	value,
		TIter &	iter
	)

staticprotectedinherited

Write data into the output buffer.

Use this function to write data to the the buffer maintained by the caller. The endianness of the data will be as specified in the options provided to the class.

Template Parameters

T	Type of the value to write. Must be integral.
Type	of output iterator

Parameters

[in]	value	Integral type value to be written.
[in,out]	iter	Output iterator.

Precondition: The iterator must be valid and can be successfully dereferenced and incremented at least sizeof(T) times.

Postcondition: The iterator is advanced.

Note: Thread safety: Safe for distinct buffers, unsafe otherwise.

◆ writeData() [2/2]

template<typename... TOptions>

template<std::size_t TSize, typename T , typename TIter >

static void comms::Field< TOptions >::writeData	(	T	value,
		TIter &	iter
	)

staticprotectedinherited

Write partial data into the output buffer.

Use this function to write partial data to the buffer maintained by the caller. The endianness of the data will be as specified the class options.

Template Parameters

TSize	Length of the value in bytes known in compile time.
T	Type of the value to write. Must be integral.
TIter	Type of output iterator

Parameters

[in]	value	Integral type value to be written.
[in,out]	iter	Output iterator.

Precondition: TSize <= sizeof(T); The iterator must be valid and can be successfully dereferenced and incremented at least TSize times.

Postcondition: The iterator is advanced.

Note: Thread safety: Safe for distinct buffers, unsafe otherwise.

◆ writeNoStatus()

template<typename TFieldBase , typename TMembers , typename... TOptions>

template<typename TIter >

void comms::field::Variant< TFieldBase, TMembers, TOptions >::writeNoStatus ( TIter & iter ) const

Write current field value to output data sequence without error check and status report.

Similar to write(), but doesn't perform any correctness checks and doesn't report any failures.

Parameters

[in,out] iter Iterator to write the data.

Postcondition: Iterator is advanced.

Friends And Related Symbol Documentation

◆ COMMS_VARIANT_MEMBERS_ACCESS

template<typename TFieldBase , typename TMembers , typename... TOptions>

#define COMMS_VARIANT_MEMBERS_ACCESS ( ... )

    COMMS_EXPAND(COMMS_DEFINE_FIELD_ENUM(__VA_ARGS__)) \
    COMMS_AS_VARIANT_FUNC { \
        auto& var = comms::field::toFieldBase(*this); \
        using Var = typename std::decay<decltype(var)>::type; \
        static_assert(std::tuple_size<typename Var::Members>::value == FieldIdx_numOfValues, \
            "Invalid number of names for variant field"); \
        return var; \
    }\
    COMMS_AS_VARIANT_CONST_FUNC { \
        auto& var = comms::field::toFieldBase(*this); \
        using Var = typename std::decay<decltype(var)>::type; \
        static_assert(std::tuple_size<typename Var::Members>::value == FieldIdx_numOfValues, \
            "Invalid number of names for variant field"); \
        return var; \
    } \
    COMMS_DO_VARIANT_MEM_ACC_FUNC(asVariant(), __VA_ARGS__)

Add convenience access enum and functions to the members of comms::field::Variant field.

Very similar to COMMS_VARIANT_MEMBERS_NAMES(), but does NOT require definition of Base inner member type (for some compilers) and does NOT define inner Field_* types for used member fields.

Parameters

[in] ... List of fields' names.

Warning: Some compilers, such as clang or early versions of g++ may have problems compiling code generated by this macro even though it uses valid C++11 constructs in attempt to automatically identify the type of the base class. If the compilation fails, and this macro resides inside a NON-template class, please use COMMS_VARIANT_MEMBERS_ACCESS_NOTEMPLATE() macro instead. In case this macro needs to reside inside a template class, then there is a need to define inner Base type, which specifies exact type of the comms::field::Variant class. For example:
template <typename... TExtraOptions>

class MyField : public

comms::field::Variant<

MyFieldBase,

std::tuple<Field1, Field2, Field3>,

TExtraOptions...

>

{

// Duplicate the base class definition

using Base =

comms::field::Variant<

MyFieldBase,

std::tuple<Field1, Field2, Field3>,

TExtraOptions...

>;

public:

COMMS_VARIANT_MEMBERS_ACCESS(member1, member2, member3);

};

comms::field::Variant
Defines a "variant" field, that can contain any of the provided ones.
Definition Variant.h:79

◆ COMMS_VARIANT_MEMBERS_ACCESS_NOTEMPLATE

template<typename TFieldBase , typename TMembers , typename... TOptions>

#define COMMS_VARIANT_MEMBERS_ACCESS_NOTEMPLATE ( ... )

COMMS_EXPAND(COMMS_DEFINE_FIELD_ENUM(__VA_ARGS__)) \

COMMS_DO_VARIANT_MEM_ACC_FUNC_NOTEMPLATE(__VA_ARGS__)

Similar to COMMS_VARIANT_MEMBERS_ACCESS(), but dedicated for non-template classes.

The COMMS_VARIANT_MEMBERS_ACCESS() macro is a generic one, which can be used in any class (template, or non-template). However, some compilers (such as g++-4.9 and below, clang-4.0 and below) may fail to compile it even though it uses valid C++11 constructs. If the compilation fails and the class it is being used in is NOT a template one, please use COMMS_VARIANT_MEMBERS_ACCESS_NOTEMPLATE() instead.

◆ COMMS_VARIANT_MEMBERS_NAMES

template<typename TFieldBase , typename TMembers , typename... TOptions>

#define COMMS_VARIANT_MEMBERS_NAMES ( ... )

COMMS_EXPAND(COMMS_VARIANT_MEMBERS_ACCESS(__VA_ARGS__)) \

COMMS_EXPAND(COMMS_DO_FIELD_TYPEDEF(typename Base::Members, Field_, FieldIdx_, __VA_ARGS__))

comms::field::Variant::COMMS_VARIANT_MEMBERS_ACCESS

#define COMMS_VARIANT_MEMBERS_ACCESS(...)

Add convenience access enum and functions to the members of comms::field::Variant field.

Definition Variant.h:746

Provide names for member fields of comms::field::Variant field.

All the possible field types the comms::field::Variant field can contain are bundled in std::tuple and provided as a template parameter to the definition of the comms::field::Variant field.

using MyFieldBase = comms::Field<comms::option::BigEndian>;
using Field1 = ...;
using Field2 = ...;
using Field3 = ...;
using MyField =
    comms::field::Variant<
        MyFieldBase,
        std::tuple<Field1, Field2, Field3>
    >;
 
MyField field;
auto& field1 = field.initField<0>(); // Initialise the field to contain Field1 value
field1.value() = ...;

However, it would be convenient to provide names and easier access to all the poisble variants. The COMMS_VARIANT_MEMBERS_NAMES() macro does exactly that when used inside the field class definition. Just inherit from the comms::field::Variant class and use the macro inside with the names for the member fields:

class MyField : public comms::field::Variant<...>
{
    // (Re)definition of the base class as inner Base type is
    // the required of COMMS_VARIANT_MEMBERS_NAMES() macro.
    using Base = comms::field::Variant<...>;
public:
    COMMS_FIELD_MEMBERS_NAMES(member1, member2, member3);
}

NOTE that there is a required to have Base member type that specifies base class used.

Usage of COMMS_FIELD_MEMBERS_NAMES() macro is equivalent to having the following types and functions definitions:

class MyField : public comms::field::Variant<...>
{
public:
    // Access indices for member fields
    enum FieldIdx {
        FieldIdx_member1,
        FieldIdx_member2,
        FieldIdx_member3,
        FieldIdx_numOfValues
    };
 
    // Initialise as first member (Field1)
    template <typename... TArgs>
    Field1& initField_member1(TArgs&&... args)
    {
        rerturn initField<FieldIdx_member1>(std::forward<TArgs>(args)...);
    }
 
    // De-initialise first member (Field1)
    void deinitField_member1()
    {
        rerturn deinitField<FieldIdx_member1>();
    }
 
    // Accessor to the stored field as first member (Field1)
    Field1& accessField_member1()
    {
        return accessField<FieldIdx_member1>();
    }
 
    // Const variant of the accessor to the stored field as first member (Field1)
    const Field1& accessField_member1() const
    {
        return accessField<FieldIdx_member1>();
    }
 
    // Initialise as second member (Field2)
    template <typename... TArgs>
    Field2& initField_member2(TArgs&&... args)
    {
        rerturn initField<FieldIdx_member2>(std::forward<TArgs>(args)...);
    }
 
    // De-initialise second member (Field2)
    void deinitField_member2()
    {
        rerturn deinitField<FieldIdx_member2>();
    }
 
    // Accessor to the stored field as second member (Field2)
    Field2& accessField_member2()
    {
        return accessField<FieldIdx_member2>();
    }
 
    // Const variant of the accessor to the stored field as second member (Field2)
    const Field2& accessField_member2() const
    {
        return accessField<FieldIdx_member2>();
    }
 
    // Initialise as third member (Field3)
    template <typename... TArgs>
    Field3& initField_member3(TArgs&&... args)
    {
        rerturn initField<FieldIdx_member3>(std::forward<TArgs>(args)...);
    }
 
    // De-initialise third member (Field3)
    void deinitField_member3()
    {
        rerturn deinitField<FieldIdx_member3>();
    }
 
    // Accessor to the stored field as third member (Field3)
    Field3& accessField_member3()
    {
        return accessField<FieldIdx_member3>();
    }
 
    // Const variant of the accessor to the stored field as third member (Field3)
    const Field3& accessField_member3() const
    {
        return accessField<FieldIdx_member3>();
    }
 
    // Redefinition of the field types:
    using Field_member1 = Field1;
    using Field_member2 = Field2;
    using Field_member3 = Field3;
};

NOTE, that provided names member1, member2, and member3, have found their way to the following definitions:

FieldIdx enum. The names are prefixed with FieldIdx_. The FieldIdx_nameOfValues value is automatically added at the end.
Initialisation functions prefixed with initField_
De-initialisation functions prefixed with deinitField_
Accessor functions prefixed with accessField_
Types of fields prefixed with Field_*

See Variant Fields for more examples and details

Parameters

[in] ... List of member fields' names.

Note: Defined in "comms/field/Variant.h"

See also: COMMS_VARIANT_MEMBERS_ACCESS(); Variant Fields

◆ isVariant()

template<typename T >

constexpr bool isVariant ( )

Template Parameters

T Any type.

Returns: true in case provided type is any variant of Variant

◆ operator!=()

template<typename TFieldBase , typename TMembers , typename... TOptions>

bool operator!=	(	const Variant< TFieldBase, TMembers, TOptions... > &	field1,
		const Variant< TFieldBase, TMembers, TOptions... > &	field2
	)

Parameters

[in]	field1	First field.
[in]	field2	Second field.

Returns: true in case fields are NOT equal, false otherwise.

◆ operator<()

template<typename TFieldBase , typename TMembers , typename... TOptions>

bool operator<	(	const Variant< TFieldBase, TMembers, TOptions... > &	field1,
		const Variant< TFieldBase, TMembers, TOptions... > &	field2
	)

Parameters

[in]	field1	First field.
[in]	field2	Second field.

◆ operator==()

template<typename TFieldBase , typename TMembers , typename... TOptions>

bool operator==	(	const Variant< TFieldBase, TMembers, TOptions... > &	field1,
		const Variant< TFieldBase, TMembers, TOptions... > &	field2
	)

Parameters

[in]	field1	First field.
[in]	field2	Second field.

Returns: true in case fields are equal, false otherwise.

The documentation for this class was generated from the following file:

include/comms/field/Variant.h

Detailed Description

Public Types

Public Member Functions

Static Public Member Functions

Static Protected Member Functions

Related Symbols

Member Typedef Documentation

◆ FieldType

◆ Members

◆ ValueType

Constructor & Destructor Documentation

◆ Variant()

Member Function Documentation

◆ accessField() [1/2]

◆ accessField() [2/2]

◆ canWrite()

◆ currentField()

◆ currentFieldExec() [1/2]

◆ currentFieldExec() [2/2]

◆ currentFieldValid()

◆ deinitField()

◆ getValue()

◆ getVersion()

◆ hasVarLength()

◆ initField()

◆ length()

◆ maxLength()

◆ minLength()

◆ read()

◆ readData() [1/2]

◆ readData() [2/2]

◆ refresh()

◆ reset()

◆ selectField()

◆ setValue()

◆ setVersion()

◆ valid() [1/2]

◆ valid() [2/2]

◆ value() [1/2]

◆ value() [2/2]

◆ write()

◆ writeData() [1/2]

◆ writeData() [2/2]

◆ writeNoStatus()

Friends And Related Symbol Documentation

◆ COMMS_VARIANT_MEMBERS_ACCESS

◆ COMMS_VARIANT_MEMBERS_ACCESS_NOTEMPLATE

◆ COMMS_VARIANT_MEMBERS_NAMES

◆ isVariant()

◆ operator!=()

◆ operator<()

◆ operator==()