LazyInit Class Reference

#include <lazyinit.h>

Detailed Description

Thread-safe helper class for single-threaded lazy initialization.

Typical usage case is a method which initializes data on first call, for example

class Sample
{
public:
  MyObject* GetObject()
  {
    _state.Init(
      [this]() -> Bool
      {
        // Your init code goes here.
        // Return true if initialization was successful and false if it failed.
        // Using type Result<void> instead of Bool for the return value is supported as well.
        return true;
      });
 
    return _object;
  }
private:
  LazyInit _state;
  MyObject* _object;
  SomeMoreData _xyz;
};

Note

The code of the lambda must be single threaded, using multithreaded code will lead to a deadlock! For potentially multithreaded initialization use LazyInitThreaded. Performance note: Declaring a global LazyInit as a static member of a class will degrade its performance because the compiler will guard its access with a slow and unnecessary mutex. To avoid this move the global state outside of the class.

THREADSAFE.

Public Member Functions
template<typename FN >
MAXON_ATTRIBUTE_FORCE_INLINE auto	Init (FN &&fn) -> decltype(fn())
template<typename FN = decltype(Dummy)>
void	Reset (FN &&fn=Dummy)
Bool	IsInitialized () const
	operator Bool () const
Bool	IsPendingInitialization () const

Private Types
enum class	STATE : Int32 {   UNINITIALIZED ,   PENDING ,   INITIALIZED }

Private Member Functions
enum maxon::LazyInit::STATE Int32	MAXON_ENUM_LIST_CLASS (STATE)

Static Private Member Functions
static void	Dummy ()
static Bool	ToBool (Bool v)
static Bool	ToBool (ResultMem v)
static Bool	ToBool (const Result< void > &v)

Private Attributes
AtomicInt32	_state

Member Enumeration Documentation

STATE

enum STATE : Int32

strongprivate

Enumerator
UNINITIALIZED
PENDING
INITIALIZED

Member Function Documentation

MAXON_ENUM_LIST_CLASS()

enum maxon::LazyInit::STATE Int32 MAXON_ENUM_LIST_CLASS ( STATE  )

private

Dummy()

static void Dummy ( )

staticprivate

ToBool() [1/3]

static Bool ToBool ( Bool  v )

staticprivate

ToBool() [2/3]

static Bool ToBool ( ResultMem  v )

staticprivate

ToBool() [3/3]

static Bool ToBool ( const Result< void > &  v )

staticprivate

Init()

MAXON_ATTRIBUTE_FORCE_INLINE auto Init

(

FN &&

fn

)

-> decltype(fn())

Initializes an object by calling the specified method (and does nothing if the object has already been initialized). The method #fn will be executed on the current thread and must be executing quickly. It is not allowed to perform multithreaded code as part of the initialization because this could deadlock and waiting threads would be busy-idling.

Note

The code of the lambda must be single threaded! Otherwise use LazyInitThreaded (and review your code thoroughly). THREADSAFE.

Parameters

[in]

fn

Method (usually a lambda) to initialize something, must return a Bool or a Result<void>.

Returns

True/OK if initialization was successful or object has already been initialized, otherwise result of failed initialization.

Reset()

void Reset

(

FN &&

fn = Dummy

)

Resets an object by calling the specified method. Does nothing if the object has already been reset. THREADSAFE.

Parameters

[in]

fn

Optional method (usually a lambda) to reset something.

IsInitialized()

Bool IsInitialized

(

)

const

Returns if the object already has been initialized. THREADSAFE.

Returns

True if initialization was successful.

operator Bool()

operator Bool ( ) const

explicit

Returns if the object already has been initialized. THREADSAFE.

Returns

True if initialization was successful.

IsPendingInitialization()

Bool IsPendingInitialization

(

)

const

Returns if the object is currently being initialized (for debugging) THREADSAFE.

Returns

True if the tinitialization is pending.

Member Data Documentation

_state

AtomicInt32 _state

private