vlink::SysSemaphore类 参考

Named cross-process counting semaphore. 更多...

#include <sys_semaphore.h>

vlink::SysSemaphore 的协作图:

Public 成员函数
	SysSemaphore (size_t count=0)
	Constructs a SysSemaphore with the given initial count.
	~SysSemaphore ()
	Destructor. Calls detach() if the semaphore is still attached.
bool	attach (const std::string &name)
	Creates or opens a named semaphore with the given name.
bool	detach (bool force=true)
	Closes the semaphore handle and optionally removes it from the OS namespace.
bool	acquire (size_t n=1, int timeout_ms=kInfinite)
	Decrements the semaphore counter by n, blocking if necessary.
void	release (size_t n=1)
	Increments the semaphore counter by n.
bool	is_attached () const
	Returns true if the semaphore is currently attached to an OS name.
size_t	get_count () const
	Returns the current count of the semaphore.

静态 Public 属性
static constexpr int	kInfinite {-1}
	Sentinel value for acquire() meaning "wait indefinitely".

详细描述

Named cross-process counting semaphore.

Backed by the OS named-semaphore API (POSIX sem_open or Win32 CreateSemaphore) to support synchronisation across process boundaries.

构造及析构函数说明

SysSemaphore()

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

explicit

Constructs a SysSemaphore with the given initial count.

The semaphore is not yet attached to any OS name. Call attach() before using acquire() or release().

参数

count

Initial count used when a new named semaphore is created by attach() (default: 0).

这是这个函数的调用关系图:

~SysSemaphore()

vlink::SysSemaphore::~SysSemaphore

(

)

Destructor. Calls detach() if the semaphore is still attached.

成员函数说明

acquire()

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

Decrements the semaphore counter by n, blocking if necessary.

Blocks the caller until n permits are available or timeout_ms milliseconds elapse.

参数

n	Number of permits to acquire (default: 1).
timeout_ms	Maximum time to wait in milliseconds. Use kInfinite (-1) to wait indefinitely (default).

返回

true if permits were acquired, false on timeout or error.

前置条件

is_attached() must be true.

attach()

bool vlink::SysSemaphore::attach

(

const std::string &

name

)

Creates or opens a named semaphore with the given name.

If a semaphore with name already exists in the OS namespace, it is opened and the constructor-provided initial count is ignored. If it does not exist it is created with that count.

参数

name	OS semaphore name (POSIX: must start with '/').

返回

true on success, false if the semaphore could not be created or opened.

detach()

bool vlink::SysSemaphore::detach

(

bool

force = true

)

Closes the semaphore handle and optionally removes it from the OS namespace.

After detach(), is_attached() returns false.

参数

force

If true, the semaphore is unlinked from the OS namespace (other processes lose access). Default: true.

返回

true on success, false if not attached or unlink failed.

get_count()

size_t vlink::SysSemaphore::get_count ( ) const

nodiscard

Returns the current count of the semaphore.

The value is a snapshot and may change immediately after the call. Intended for diagnostics only.

返回

Current semaphore count, or 0 if not attached or unsupported on the current backend.

函数调用图:

is_attached()

bool vlink::SysSemaphore::is_attached ( ) const

nodiscard

Returns true if the semaphore is currently attached to an OS name.

返回

true if attached, false otherwise.

release()

void vlink::SysSemaphore::release

(

size_t

n = 1

)

Increments the semaphore counter by n.

Wakes at most n threads (from any process) blocked in acquire().

参数

n	Number of permits to release (default: 1).

前置条件

is_attached() must be true.

类成员变量说明

kInfinite

int vlink::SysSemaphore::kInfinite {-1}

staticconstexpr

Sentinel value for acquire() meaning "wait indefinitely".

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该类的文档由以下文件生成:

• include/vlink/base/sys_semaphore.h