DB_PROBE_LATCH< T > Class Template Reference

Runs a slow probe once on a thread of its own and keeps its answer for good. More...

#include <db_backend_support.h>

Public Member Functions
	DB_PROBE_LATCH (std::function< T()> aProbe)
std::optional< T >	Get (std::chrono::milliseconds aWait)
	The probe's answer, or nothing if it has not finished within aWait. A probe that throws answers T().

Private Attributes
std::function< T()>	m_probe
std::once_flag	m_started
std::shared_future< T >	m_answer

Detailed Description

template<typename T>
class DB_PROBE_LATCH< T >

Runs a slow probe once on a thread of its own and keeps its answer for good.

Only a finished answer is kept. A caller that gives up waiting gets nothing, and the next caller waits on the same probe, so contention that delays the probe is never taken for a negative result.

Definition at line 128 of file db_backend_support.h.

Constructor & Destructor Documentation

DB_PROBE_LATCH()

template<typename T>

DB_PROBE_LATCH< T >::DB_PROBE_LATCH ( std::function< T()> aProbe )

inlineexplicit

Definition at line 131 of file db_backend_support.h.

References m_probe, and move.

Member Function Documentation

Get()

template<typename T>

std::optional< T > DB_PROBE_LATCH< T >::Get ( std::chrono::milliseconds aWait )

inline

The probe's answer, or nothing if it has not finished within aWait. A probe that throws answers T().

Definition at line 137 of file db_backend_support.h.

References m_answer, m_probe, m_started, and T.

Member Data Documentation

m_answer

template<typename T>

std::shared_future<T> DB_PROBE_LATCH< T >::m_answer

private

Definition at line 172 of file db_backend_support.h.

Referenced by Get().

m_probe

template<typename T>

std::function<T()> DB_PROBE_LATCH< T >::m_probe

private

Definition at line 170 of file db_backend_support.h.

Referenced by DB_PROBE_LATCH(), and Get().

m_started

template<typename T>

std::once_flag DB_PROBE_LATCH< T >::m_started

private

Definition at line 171 of file db_backend_support.h.

Referenced by Get().

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

• db_backend_support.h