ezSemaphore Class Reference

A semaphore is used to synchronize threads, similar to a mutex (see ezMutex). More...

#include <Semaphore.h>

Public Member Functions
ezResult	Create (ezUInt32 uiInitialTokenCount=0, ezStringView sSharedName=ezStringView())
	Attempts to create a new semaphore with an initial number of available tokens. More...
ezResult	Open (ezStringView sSharedName)
	Attempts to open an existing named semaphore. More...
void	AcquireToken ()
	Waits until a token is available and acquires it. More...
void	ReturnToken ()
	Returns a single token. If another thread is currently waiting for a token, this will wake it up. More...
ezResult	TryAcquireToken ()
	Same as AcquireToken() but returns immediately with EZ_FAILURE, if currently not tokens are available.

Detailed Description

A semaphore is used to synchronize threads, similar to a mutex (see ezMutex).

There are three main differences to a mutex:

1. The thread that acquires a token from a semaphore and the one that returns a token, don't have to be the same.
2. A semaphore can be locked up to N times by multiple threads in parallel. So it can be used to implement constructs like single-writer / multiple/readers.
3. A 'named' semaphore can be opened by other processes as well, which allows you to implement the basics for inter process communication (IPC).

Semaphores are quite a bit slower than mutexes (10x or so), so don't use them unless you need the added flexibility.

See also

ezMutex, ezConditionVariable

Member Function Documentation

AcquireToken()

void ezSemaphore::AcquireToken

(

)

Waits until a token is available and acquires it.

Use TryAcquireToken() to prevent blocking if desired. AcquireToken() and ReturnToken() may be called from different threads.

Create()

ezResult ezSemaphore::Create	(	ezUInt32	uiInitialTokenCount = 0,
		ezStringView	sSharedName = ezStringView()
	)

Attempts to create a new semaphore with an initial number of available tokens.

If szSharedName is a non-empty string, a 'named' semaphore is created, which can be opened on other processes as well.

This call can fail, if a semaphore with the same name already exists. Use ezSemaphore::Open() instead.

Open()

ezResult ezSemaphore::Open

(

ezStringView

sSharedName

)

Attempts to open an existing named semaphore.

Fails if no such semaphore exists.

ReturnToken()

void ezSemaphore::ReturnToken

(

)

Returns a single token. If another thread is currently waiting for a token, this will wake it up.

AcquireToken() and ReturnToken() may be called from different threads.

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

• /home/runner/work/ezEngine/ezEngine/Code/Engine/Foundation/Threading/Semaphore.h
• /home/runner/work/ezEngine/ezEngine/Code/Engine/Foundation/Platform/Posix/Semaphore_Posix.h