vlink::Semaphore Class Reference

In-process counting semaphore with an optional acquire timeout. More...

#include <semaphore.h>

Collaboration diagram for vlink::Semaphore:

Public Member Functions
	Semaphore (size_t count=0) noexcept
	Constructs a semaphore with the given initial permit count. More...
	~Semaphore () noexcept
	Destructor. Wakes every blocked acquirer before tearing down internal state. More...
bool	acquire (size_t n=1, int timeout_ms=kInfinite) noexcept
	Decrements the counter by n, blocking when not enough permits are available. More...
void	release (size_t n=1) noexcept
	Increments the counter by n and wakes blocked acquirers. More...
void	reset (bool interrupt_waiters=false) noexcept
	Restores the counter to the initial value supplied to the constructor. More...
size_t	get_count () const noexcept
	Returns a non-atomic snapshot of the current counter value. More...

Static Public Attributes
static constexpr int	kInfinite {-1}
	Sentinel value for acquire() meaning wait indefinitely. More...

Detailed Description

In-process counting semaphore with an optional acquire timeout.

The internal counter starts at the value supplied to the constructor; acquire decrements it (blocking when not enough permits are available) and release increments it while waking blocked acquirers.

Constructor & Destructor Documentation

Semaphore()

vlink::Semaphore::Semaphore ( size_t  count = 0 )

explicitnoexcept

Constructs a semaphore with the given initial permit count.

Parameters

count

Initial permit count. Default: 0.

~Semaphore()

vlink::Semaphore::~Semaphore ( )

noexcept

Destructor. Wakes every blocked acquirer before tearing down internal state.

Member Function Documentation

acquire()

bool vlink::Semaphore::acquire ( size_t  n = 1, int  timeout_ms = kInfinite  )

noexcept

Decrements the counter by n, blocking when not enough permits are available.

The call blocks while the counter is less than n. A timeout returns false without modifying the counter. When reset(true) is invoked while a thread is blocked, the wait returns false and the counter is restored to the initial value.

Parameters

n	Number of permits requested. Default: 1.
timeout_ms	Maximum wait in milliseconds; kInfinite waits forever.

Returns

true when the permits were acquired; false on timeout or reset.

get_count()

size_t vlink::Semaphore::get_count ( ) const

noexcept

Returns a non-atomic snapshot of the current counter value.

The value may change immediately after the call returns; treat the result as a diagnostic-only hint.

Returns

Current permit count snapshot.

release()

void vlink::Semaphore::release ( size_t  n = 1 )

noexcept

Increments the counter by n and wakes blocked acquirers.

Broadcasts the condition variable so every blocked acquirer can re-evaluate the permit count. Safe to call from any thread.

Parameters

n	Number of permits to add. Default: 1.

reset()

void vlink::Semaphore::reset ( bool  interrupt_waiters = false )

noexcept

Restores the counter to the initial value supplied to the constructor.

When interrupt_waiters is true every blocked acquirer is woken and its call returns false, which is the recommended way to release waiters during shutdown.

Parameters

interrupt_waiters

When true, wakes blocked acquirers. Default: false.

Member Data Documentation

kInfinite

constexpr int vlink::Semaphore::kInfinite {-1}

staticconstexpr

Sentinel value for acquire() meaning wait indefinitely.

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

• include/vlink/base/semaphore.h