ut::Per_thread< Value > Class Template Reference

Registry of per-thread values owned by one enclosing object. More...

#include <ut0per_thread.h>

Public Member Functions
	Per_thread (std::function< Value()> factory)
	Create an empty registry. More...
	Per_thread (const Per_thread &)=delete
Per_thread &	operator= (const Per_thread &)=delete
Value *	operator-> ()
	Return this thread's Value, creating and storing it on first access. More...

Private Attributes
std::function< Value()>	m_factory
std::mutex	m_mutex
std::unordered_map< std::thread::id, Value >	m_map

Detailed Description

template<typename Value>
class ut::Per_thread< Value >

Registry of per-thread values owned by one enclosing object.

This solves the case in which code needs one Value per participating thread, but the values must follow the lifetime of a registry. Plain thread_local is not enough, because thread-local objects outlive the registry and are destroyed only when their threads exit.

Constructor & Destructor Documentation

Per_thread() [1/2]

template<typename Value >

ut::Per_thread< Value >::Per_thread ( std::function< Value()>  factory )

inlineexplicit

Create an empty registry.

Parameters

[in]

factory

callable used to create the current thread's Value on the first access from that thread; must be non-empty; must not attempt calling the Per_thread::operator->() as it could lead to endless recursion.

Per_thread() [2/2]

template<typename Value >

ut::Per_thread< Value >::Per_thread ( const Per_thread< Value > &  )

delete

Member Function Documentation

operator->()

template<typename Value >

Value * ut::Per_thread< Value >::operator-> ( )

inline

Return this thread's Value, creating and storing it on first access.

Repeated calls from the same thread return the same object until the registry is destroyed.

As thread ids might be reused, it is possible that a new thread "inherits" the Value which was used by an old thread, instead of starting with a fresh one.

Returns

pointer to the Value owned by this registry for the calling thread

operator=()

template<typename Value >

Per_thread & ut::Per_thread< Value >::operator= ( const Per_thread< Value > &  )

delete

Member Data Documentation

m_factory

template<typename Value >

std::function<Value()> ut::Per_thread< Value >::m_factory

private

m_map

template<typename Value >

std::unordered_map<std::thread::id, Value> ut::Per_thread< Value >::m_map

private

m_mutex

template<typename Value >

std::mutex ut::Per_thread< Value >::m_mutex

private

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

• storage/innobase/include/ut0per_thread.h