OFSemaphore Class Reference

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

List of all members.

Public Member Functions

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

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.

Static Public Attributes

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

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().

Definition at line 274 of file ofthread.h.

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.

Definition at line 322 of file ofthread.h.

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

Generated on 20 Dec 2005 for OFFIS DCMTK Version 3.5.4 by Doxygen 1.4.5