stdx::flags< E > Class Template Reference

a type-safe flags type. More...

#include <flags.h>

Public Types
using	enum_type = std::decay_t< E >
	underlying integer type of the enum_type. More...
using	underlying_type = std::underlying_type_t< enum_type >
	implementation type of the underlying type. More...
using	impl_type = std::make_unsigned_t< underlying_type >
using	size_type = std::size_t

Public Member Functions
constexpr	flags ()=default
	default constructor. More...
constexpr	flags (const flags &other)=default
	copy constructor. More...
constexpr	flags (flags &&other)=default
	move constructor More...
constexpr flags &	operator= (const flags &other)=default
	copy assignment More...
constexpr flags &	operator= (flags &&other)=default
	move assignment More...
constexpr	flags (enum_type v)
	converting constructor from enum_type. More...
constexpr	operator bool () const noexcept
	check if any bit is set. More...
constexpr bool	operator! () const noexcept
	check if no bit is set. More...
constexpr flags	operator~ () const noexcept
	negation of all bits. More...
constexpr flags &	operator|= (const flags &other) noexcept
	bit-or. More...
constexpr flags &	operator&= (const flags &other) noexcept
	bit-and. More...
constexpr flags &	operator^= (const flags &other) noexcept
	bit-xor. More...
constexpr void	underlying_value (underlying_type v) noexcept
	set underlying value. More...
constexpr underlying_type	underlying_value () const noexcept
	get underlying value. More...
constexpr size_type	count () const noexcept
	count bits set to true. More...
constexpr size_type	size () const noexcept
	returns number of bits the flag-type can hold. More...
constexpr void	reset ()
	reset all flags to 0. More...

Private Member Functions
constexpr	flags (impl_type v) noexcept

Private Attributes
impl_type	v_ {}

Friends
constexpr friend flags	operator& (flags a, flags b) noexcept
	bit-and. More...
constexpr friend flags	operator| (flags a, flags b) noexcept
	bit-or. More...
constexpr friend flags	operator^ (flags a, flags b) noexcept
	bit-xor. More...

Detailed Description

template<class E>
class stdx::flags< E >

a type-safe flags type.

abstract

Using flags in the in C++ isn't very ergonimic:

1. using plain C-enum's isn't typesafe
2. using std::bitset requires bit-positions to set/reset/test them
3. scoped-enums (enum class) doesn't have operaters

For ease of use it should be possible to have a flags-type which allows the type-safe operations:

• flags = flags & flag
• flags &= flag
• flags = flags | flag
• flags |= flag
• flags = flags ^ flag
• flags ^= flag
• flags = ~flag
• flag | flag -> flags
• flag & flag -> flags
• flag ^ flag -> flags

example

// underlying scoped-enum
enum class somebits {
  bit0 = 1 << 0,
  bit1 = 1 << 1,
};
 
// activate stdx::flags support for the scoped-enum
namespace stdx {
template<>
struct is_flags<somebits> : std::true_type {}
}
 
{ // default-construct + assignment
  stdx::flags<somebits> someflags;
 
  someflags = somebits::bit0 | somebits::bit1;
 
  // get the underlying bitvalue.
  std::cerr << someflags.underlying_value() << "\n";
}
 
{ // direct initialization from enum
  stdx::flags<somebits> someflags{somebits::bit0 | somebits::bit1};
}
 
{ // testing if bit set
  stdx::flags<somebits> someflags{somebits::bit0 | somebits::bit1};
 
  if (someflags & somebits::bit1) {} // true
}
 
{ // setting raw value
  stdx::flags<somebits> someflags;
  someflags.underlying_value(3);
 
  if (someflags & somebits::bit0) {} // true
  if (someflags & somebits::bit1) {} // true
}

Template Parameters

E	a scoped enum that is tagged with stdx::is_flags.

Member Typedef Documentation

enum_type

template<class E >

using stdx::flags< E >::enum_type = std::decay_t<E>

underlying integer type of the enum_type.

impl_type

template<class E >

using stdx::flags< E >::impl_type = std::make_unsigned_t<underlying_type>

size_type

template<class E >

using stdx::flags< E >::size_type = std::size_t

underlying_type

template<class E >

using stdx::flags< E >::underlying_type = std::underlying_type_t<enum_type>

implementation type of the underlying type.

Constructor & Destructor Documentation

flags() [1/5]

template<class E >

constexpr stdx::flags< E >::flags ( )

constexprdefault

default constructor.

initializes underlying_value to 0 (no-bits-set).

flags() [2/5]

template<class E >

constexpr stdx::flags< E >::flags ( const flags< E > &  other )

constexprdefault

copy constructor.

flags() [3/5]

template<class E >

constexpr stdx::flags< E >::flags ( flags< E > &&  other )

constexprdefault

move constructor

flags() [4/5]

template<class E >

constexpr stdx::flags< E >::flags ( enum_type  v )

inlineconstexpr

converting constructor from enum_type.

flags() [5/5]

template<class E >

constexpr stdx::flags< E >::flags ( impl_type  v )

inlineexplicitconstexprprivatenoexcept

Member Function Documentation

count()

template<class E >

constexpr size_type stdx::flags< E >::count ( ) const

inlineconstexprnoexcept

count bits set to true.

See also

size()

Returns

bits set to true.

operator bool()

template<class E >

constexpr stdx::flags< E >::operator bool ( ) const

inlineconstexprnoexcept

check if any bit is set.

Return values

true	at least one bit is set.
false	no bit is set.

operator!()

template<class E >

constexpr bool stdx::flags< E >::operator! ( ) const

inlineconstexprnoexcept

check if no bit is set.

Return values

true	no bit is set.
false	at least one bit is set.

operator&=()

template<class E >

constexpr flags & stdx::flags< E >::operator&= ( const flags< E > &  other )

inlineconstexprnoexcept

bit-and.

flags &= flags.

operator=() [1/2]

template<class E >

constexpr flags & stdx::flags< E >::operator= ( const flags< E > &  other )

constexprdefault

copy assignment

operator=() [2/2]

template<class E >

constexpr flags & stdx::flags< E >::operator= ( flags< E > &&  other )

constexprdefault

move assignment

operator^=()

template<class E >

constexpr flags & stdx::flags< E >::operator^= ( const flags< E > &  other )

inlineconstexprnoexcept

bit-xor.

flag ^= flag

operator|=()

template<class E >

constexpr flags & stdx::flags< E >::operator|= ( const flags< E > &  other )

inlineconstexprnoexcept

bit-or.

flags |= flags.

operator~()

template<class E >

constexpr flags stdx::flags< E >::operator~ ( ) const

inlineconstexprnoexcept

negation of all bits.

~flags -> flags.

reset()

template<class E >

constexpr void stdx::flags< E >::reset ( )

inlineconstexpr

reset all flags to 0.

size()

template<class E >

constexpr size_type stdx::flags< E >::size ( ) const

inlineconstexprnoexcept

returns number of bits the flag-type can hold.

See also

count()

Returns

number of bits the flag-type can hold.

underlying_value() [1/2]

template<class E >

constexpr underlying_type stdx::flags< E >::underlying_value ( ) const

inlineconstexprnoexcept

get underlying value.

Returns

underlying value.

underlying_value() [2/2]

template<class E >

constexpr void stdx::flags< E >::underlying_value ( underlying_type  v )

inlineconstexprnoexcept

set underlying value.

Parameters

v	underlying value to set.

Friends And Related Function Documentation

operator&

template<class E >

constexpr friend flags operator& ( flags< E >  a, flags< E >  b  )

friend

bit-and.

flags & flags -> flags

operator^

template<class E >

constexpr friend flags operator^ ( flags< E >  a, flags< E >  b  )

friend

bit-xor.

flags ^ flags -> flags

operator|

template<class E >

constexpr friend flags operator| ( flags< E >  a, flags< E >  b  )

friend

bit-or.

flags | flags -> flags

Member Data Documentation

v_

template<class E >

impl_type stdx::flags< E >::v_ {}

private

---

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

• router/src/harness/include/mysql/harness/stdx/flags.h