itk::Semaphore Class Reference

#include <itkSemaphore.h>

Inheritance diagram for itk::Semaphore:

[legend]Collaboration diagram for itk::Semaphore:

[legend]List of all members.

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Detailed Description

The semaphore class is used to synchronize execution between threads.

Semaphore objects maintain a counter value that can be incremented and decremented by atomic calls to Up() and Down(). Semaphores are commonly used to manage the use of a limited pool of system resources among several threads. If Down() is called when the value of the semaphore is zero, the calling thread will block until the semaphore value goes above zero again. When a blocked thread is released, it decrements the Semaphore counter before continuing to execute.

The Up() and Down() operations are standard as defined by E.W. Dijkstra. The Initialize( num ) operation creates the system semaphore object with an initial counter value of num. Initialize must be called before the Semaphore can be used. The Remove() method destroys the system semaphore object. It is not necessary to call Remove() unless you want to re-Initialize() the object.

This class supports 3 types of semaphores on Unix systems, POSIX semaphores, IPC semaphores, and IRIX semaphores from the SGI Sproc library. On Windows systems, POSIX semaphores and WIN32 thread library semaphores are supported.

Definition at line 112 of file itkSemaphore.h.

Public Types
typedef SmartPointer< const Self >	ConstPointer
typedef SmartPointer< Self >	Pointer
typedef Semaphore	Self
typedef LightObject	Superclass
Public Member Functions
virtual Pointer	CreateAnother () const
virtual void	Delete ()
void	Down ()
virtual const char *	GetNameOfClass () const
virtual int	GetReferenceCount () const
void	Initialize (unsigned int value)
void	Print (std::ostream &os, Indent indent=0) const
virtual void	Register () const
void	Remove ()
virtual void	SetReferenceCount (int)
virtual void	UnRegister () const
void	Up ()
Static Public Member Functions
static void	BreakOnError ()
static Pointer	New ()
Protected Member Functions
virtual void	PrintTrailer (std::ostream &os, Indent indent) const
	Semaphore ()
	~Semaphore ()
Protected Attributes
int	m_ReferenceCount
SimpleFastMutexLock	m_ReferenceCountLock
Methods invoked by virtual Print() to print information about the object *including superclasses.Typically not called by the user(use Print()*instead) but used in the hierarchical print process to combine the *output of several classes.*/virtual void PrintSelf(std voi	PrintHeader )(std::ostream &os, Indent indent) const

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Member Typedef Documentation

typedef SmartPointer<const Self> itk::Semaphore::ConstPointer

Reimplemented from itk::LightObject. Definition at line 119 of file itkSemaphore.h.

typedef SmartPointer<Self> itk::Semaphore::Pointer

Reimplemented from itk::LightObject. Definition at line 118 of file itkSemaphore.h.

typedef Semaphore itk::Semaphore::Self

Standard class typedefs. Reimplemented from itk::LightObject. Definition at line 116 of file itkSemaphore.h.

typedef LightObject itk::Semaphore::Superclass

Definition at line 117 of file itkSemaphore.h.

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Constructor & Destructor Documentation

itk::Semaphore::Semaphore (   )  [protected]

itk::Semaphore::~Semaphore (   )  [protected]

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Member Function Documentation

static void itk::LightObject::BreakOnError (   )  [static, inherited]

This method is called when itkExceptionMacro executes. It allows the debugger to break on error.

virtual Pointer itk::LightObject::CreateAnother (   )  const [virtual, inherited]

Create an object from an instance, potentially deferring to a factory. This method allows you to create an instance of an object that is exactly the same type as the referring object. This is useful in cases where an object has been cast back to a base class. Reimplemented in itk::Object.

virtual void itk::LightObject::Delete (   )  [virtual, inherited]

Delete an itk object. This method should always be used to delete an object when the new operator was used to create it. Using the C delete method will not work with reference counting.

void itk::Semaphore::Down (   )

Decrement the semaphore count. If the count is zero, this thread will be blocked until another thread calls the up() method. The order in which threads will be unblocked is not defined, but implementors should give preference to those threads that have waited the longest.

virtual const char* itk::Semaphore::GetNameOfClass (   )  const [virtual]

Run-time type information (and related methods). Reimplemented from itk::LightObject.

virtual int itk::LightObject::GetReferenceCount (   )  const [inline, virtual, inherited]

Gets the reference count on this object. Definition at line 98 of file itkLightObject.h.

void itk::Semaphore::Initialize (  unsigned int  value  )

Initialize the semaphore with a count of value.

static Pointer itk::Semaphore::New (   )  [static]

Method for creation through the object factory. Reimplemented from itk::LightObject.

void itk::LightObject::Print (  std::ostream &  os, Indent  indent = 0 )  const [inherited]

Cause the object to print itself out.

virtual void itk::LightObject::PrintTrailer (  std::ostream &  os, Indent  indent )  const [protected, virtual, inherited]

virtual void itk::LightObject::Register (   )  const [virtual, inherited]

Increase the reference count (mark as used by another object). Reimplemented in itk::Object.

void itk::Semaphore::Remove (   )

Remove the semaphore from the system.

virtual void itk::LightObject::SetReferenceCount (  int   )  [virtual, inherited]

Sets the reference count on this object. This is a dangerous method, use it with care. Reimplemented in itk::Object.

virtual void itk::LightObject::UnRegister (   )  const [virtual, inherited]

Decrease the reference count (release by another object). Reimplemented in itk::Object.

void itk::Semaphore::Up (   )

Increment the semaphore count, unblocking up to one thread that may be blocked in the down() method.

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Member Data Documentation

int itk::LightObject::m_ReferenceCount [mutable, protected, inherited]

Number of uses of this object by other objects. Definition at line 119 of file itkLightObject.h.

SimpleFastMutexLock itk::LightObject::m_ReferenceCountLock [mutable, protected, inherited]

Mutex lock to protect modification to the reference count Definition at line 122 of file itkLightObject.h.

Methods invoked by virtual Print () to print information about the object * including superclasses. Typically not called by the user (use Print() * instead) but used in the hierarchical print process to combine the * output of several classes. */ virtual void PrintSelf(std voi itk::LightObject::PrintHeader)(std::ostream &os, Indent indent) const [protected, inherited]

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

• itkSemaphore.h

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