Optional< X > Class Template Reference

Like a smart pointer, allows for object to not exist (nullptr) More...

#include <MemoryX.h>

Inheritance diagram for Optional< X >:

Public Types
using	value_type = X

Public Member Functions
	Optional ()
	Optional (const Optional &that)
Optional &	operator= (const Optional &that)
	Optional (Optional &&that)
Optional &	operator= (Optional &&that)
template<typename... Args>
X &	emplace (Args &&... args)
	~Optional ()
X &	operator* () const
	Dereference, with the usual bad consequences if NULL. More...
X *	operator-> () const
void	reset ()
	operator bool () const
bool	has_value () const

Private Member Functions
X *	address ()

Private Attributes
union {
double   d
char   storage [sizeof(X)]
};
X *	pp { nullptr }

Detailed Description

template<typename X>
class Optional< X >

Like a smart pointer, allows for object to not exist (nullptr)

emulating some of std::optional of C++17

template class Optional<X> Can be used for monomorphic objects that are stack-allocable, but only conditionally constructed. You might also use it as a member. Initialize with emplace(), then use like a smart pointer, with *, ->, reset(), or in if()

Definition at line 144 of file MemoryX.h.

Member Typedef Documentation

value_type

template<typename X >

using Optional< X >::value_type = X

Definition at line 147 of file MemoryX.h.

Constructor & Destructor Documentation

Optional() [1/3]

template<typename X >

Optional< X >::Optional ( )

inline

Definition at line 150 of file MemoryX.h.

{}

Optional() [2/3]

template<typename X >

Optional< X >::Optional ( const Optional< X > &  that )

inline

Definition at line 153 of file MemoryX.h.

   {
      if (that)
         emplace(*that);
   }

Optional() [3/3]

template<typename X >

Optional< X >::Optional ( Optional< X > &&  that )

inline

Definition at line 170 of file MemoryX.h.

   {
      if (that)
         emplace(::std::move(*that));
   }

~Optional()

template<typename X >

Optional< X >::~Optional ( )

inline

Definition at line 203 of file MemoryX.h.

   {
      reset();
   }

Member Function Documentation

address()

template<typename X >

X* Optional< X >::address ( )

inlineprivate

Definition at line 239 of file MemoryX.h.

   {
      return reinterpret_cast<X*>(&storage);
   }

Referenced by Optional< CommandSignature >::emplace().

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emplace()

template<typename X >

template<typename... Args>

X& Optional< X >::emplace ( Args &&...  args )

inline

Make an object in the buffer, passing constructor arguments, but destroying any previous object first Note that if constructor throws, we remain in a consistent NULL state – giving exception safety but only weakly (previous value was lost if present)

Definition at line 193 of file MemoryX.h.

   {
      // Lose any old value
      reset();
      // emplace NEW value
      pp = safenew(address()) X(std::forward<Args>(args)...);
      return **this;
   }

Referenced by ProjectFileManager::DoSave(), OverlayPanel::DrawOverlays(), OldStyleCommandType::GetSignature(), Optional< CommandSignature >::operator=(), Optional< CommandSignature >::Optional(), EffectFindClipping::Process(), NyquistEffect::Process(), FrequencyPlotDialog::Recalc(), and ShuttleGuiBase::StartRadioButtonGroup().

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has_value()

template<typename X >

bool Optional< X >::has_value ( ) const

inline

Definition at line 233 of file MemoryX.h.

   {
      return pp != nullptr;
   }

operator bool()

template<typename X >

Optional< X >::operator bool ( ) const

inlineexplicit

Definition at line 228 of file MemoryX.h.

   {
      return pp != nullptr;
   }

operator*()

template<typename X >

X& Optional< X >::operator* ( ) const

inline

Dereference, with the usual bad consequences if NULL.

Definition at line 211 of file MemoryX.h.

   {
      return *pp;
   }

operator->()

template<typename X >

X* Optional< X >::operator-> ( ) const

inline

Definition at line 216 of file MemoryX.h.

   {
      return pp;
   }

operator=() [1/2]

template<typename X >

Optional& Optional< X >::operator= ( const Optional< X > &  that )

inline

Definition at line 159 of file MemoryX.h.

   {
      if (this != &that) {
         if (that)
            emplace(*that);
         else
            reset();
      }
      return *this;
   }

operator=() [2/2]

template<typename X >

Optional& Optional< X >::operator= ( Optional< X > &&  that )

inline

Definition at line 176 of file MemoryX.h.

   {
      if (this != &that) {
         if (that)
            emplace(::std::move(*that));
         else
            reset();
      }
      return *this;
   }

reset()

template<typename X >

void Optional< X >::reset ( )

inline

Definition at line 221 of file MemoryX.h.

   {
      if (pp)
         pp->~X(), pp = nullptr;
   }

Referenced by Optional< CommandSignature >::emplace(), ShuttleGuiBase::EndRadioButtonGroup(), Optional< CommandSignature >::operator=(), and Optional< CommandSignature >::~Optional().

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Member Data Documentation

@1

union { ... }

d

template<typename X >

double Optional< X >::d

Definition at line 252 of file MemoryX.h.

pp

template<typename X >

X* Optional< X >::pp { nullptr }

private

Definition at line 256 of file MemoryX.h.

Referenced by Optional< CommandSignature >::emplace(), Optional< CommandSignature >::has_value(), Optional< CommandSignature >::operator bool(), Optional< CommandSignature >::operator*(), Optional< CommandSignature >::operator->(), and Optional< CommandSignature >::reset().

storage

template<typename X >

char Optional< X >::storage[sizeof(X)]

Definition at line 253 of file MemoryX.h.

Referenced by Optional< CommandSignature >::address().

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

• MemoryX.h