OFSemaphore Class Reference

provides an operating system independent abstraction for semaphores. More...

Public Member Functions
	OFSemaphore (unsigned int numResources)
	constructor. More...
	~OFSemaphore ()
	destructor
OFBool	initialized () const
	checks whether creation of the object was successful. More...
int	wait ()
	blocks the calling thread until the semaphore counter is greater than zero and then atomically decreases the counter. More...
int	trywait ()
	atomically decreases the counter if it is larger than zero, otherwise returns OFSemaphore::busy. More...
int	post ()
	atomically increases the counter. More...

Static Public Member Functions
static void	errorstr (OFString &description, int code)
	converts any of the error codes returned by the methods of this class into a textual description, which is written into the string object. More...

Static Public Attributes
static const int	busy
	this constant is returned by the trywait() method if the semaphore is already locked. More...

Private Member Functions
	OFSemaphore (const OFSemaphore &arg)
	unimplemented private copy constructor
OFSemaphore &	operator= (const OFSemaphore &arg)
	unimplemented private assignment operator

Private Attributes
void *	theSemaphore
	semaphore resource

Detailed Description

provides an operating system independent abstraction for semaphores.

A semaphore is a non-negative integer counter that is used to coordinate access to resources. The initial and maximum value of the counter is defined by the constructor. Each call to wait() decreases the counter by one and each call to post() increases the count by one. If a thread calls wait() while the counter is zero, the thread is blocked until another thread has increased the counter using post().

Constructor & Destructor Documentation

OFSemaphore::OFSemaphore

(

unsigned int

numResources

)

constructor.

Parameters

numResources

is the initial and maximum value for the semaphore.

Member Function Documentation

static void OFSemaphore::errorstr ( OFString &  description, int  code  )

static

converts any of the error codes returned by the methods of this class into a textual description, which is written into the string object.

Parameters

description	string object into which the error description is written.
code	error code

OFBool OFSemaphore::initialized

(

)

const

checks whether creation of the object was successful.

Returns

OFTrue if the object was successfully created, OFFalse otherwise.

int OFSemaphore::post

(

)

atomically increases the counter.

If threads are blocked on the semaphore, at least one of them is unblocked.

Returns

0 upon success, an error code otherwise.

int OFSemaphore::trywait

(

)

atomically decreases the counter if it is larger than zero, otherwise returns OFSemaphore::busy.

Returns

0 upon success, OFSemaphore::busy if the semaphore is already locked, an error code otherwise.

int OFSemaphore::wait

(

)

blocks the calling thread until the semaphore counter is greater than zero and then atomically decreases the counter.

Returns

0 upon success, an error code otherwise.

Member Data Documentation

const int OFSemaphore::busy

static

this constant is returned by the trywait() method if the semaphore is already locked.

Since this value is operating system dependent, comparisons should always compare the return value of trywait() with this constant.

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

• ofstd/include/dcmtk/ofstd/ofthread.h