SbThreadLocalStorage Class Reference
[Threads]

Thread Local Storage (TLS) class. More...

#include <Inventor/threads/SbThreadLocalStorage.h>

List of all members.

Static Public Member Functions
static void	createStorage (size_t &classThreadId, const size_t byteSize, SoInitTLSClassCB *initFunc=NULL, SoExitTLSClassCB *exitFunc=NULL, const char *funcName=NULL)
static void	deleteStorage (size_t &classThreadId, const char *funcName=NULL)
static bool	isInitialized (const size_t classThreadId)
static void *	getStorage (const size_t classThreadId)

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Detailed Description

Thread Local Storage (TLS) class.

This class allows to create thread local data storage. This allow to manage per thread static global variables in multithread mode.

Example on how to use the Thread Local Storage (TLS):

In this example we move static variables s_myStaticVar1 and s_myStaticVar2 of the class MyClass to Thread Local Storage,

• Original myClass implementation :
  

         class myClass
         {
            
            static void initClass();
            static void exitClass();
            ... 
            static int    s_myStaticVar1;
            static float* s_myStaticVar2;
            ...
         }
  
         void myClass::initClass()
         {
           s_myStaticVar1 = 32;
           s_myStaticVar2 = new float[32];
         }
  
         void myClass::exitClass()
         {
           s_myStaticVar1 = 0;
           delete [] s_myStaticVar2;
         }
  

• Modified myClass implementation to support use TLS :
  

         class myClass
         {
            
            static void initClass();
            static void exitClass();
  
            // Declare necessary members and methods for TLS usage
            SB_THREAD_TLS_HEADER();
            ...
            // structure to handle per thread static variables
            struct MTstruct {
              int    s_myStaticVar1;
              float* s_myStaticVar2;
            }
            ...
         }
  
         // Properly initilize members and methods for TLS usage
         SB_THREAD_TLS_SOURCE( myClass );
  
         void myClass::initClass()
         {
           // register and reserve space for TLS
           SB_THREAD_INIT_CLASS(myClass, MTstruct);
         }
  
         void myClass::exitClass()
         {
         }
  
         void myClass::initTLSClass()
         {
           // get access to TLS and init/allocate variables once per thread
           struct myClass::MTstruct * mtstruct = (struct myClass::MTstruct *)GET_THREAD_LOCAL_STORAGE(myClass) ;
           mtstruct->s_myStaticVar1 = 32;
           mtstruct->s_myStaticVar2 = new float[32];
         }
  
         void myClass::exitTLSClass()
         {
           if (SbThreadLocaStorage::isInitialized(myClass::MT_id))
           {
             // get access to TLS and deallocate variables once per thread
             struct myClass::MTstruct * mtstruct = (struct myClass::MTstruct *)GET_THREAD_LOCAL_STORAGE(myClass) ;
             delete [] mtstruct->s_myStaticVar2;
           }
         }
  

• Each time a variable in Thread Local Storage is used, the structure containing this variable needs to be fetched using the following macro :

         struct myClass::MTstruct * mtstruct = (struct myClass::MTstruct *) GET_THREAD_LOCAL_STORAGE(myClass) ;
  

  The variables can then be used as, for example: mtstruct->variable1.
  Another macro exists to bring back one single variable of the structure :
  

         GET_THREAD_LOCAL_VAR(myClass, MTstruct, variable1)
  

SEE ALSO

SbThread, SbThreadAutoLock, SbThreadAutoReadLock, SbThreadAutoWriteLock, SbThreadBarrier, SbThreadRWMutex, SbThreadSignal

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Member Function Documentation

static void SbThreadLocalStorage::createStorage	(	size_t &	classThreadId,
		const size_t	byteSize,
		SoInitTLSClassCB *	initFunc = NULL,
		SoExitTLSClassCB *	exitFunc = NULL,
		const char *	funcName = NULL
	)			[static]

Creates or updates the local storage for the current thread.

Requests that 'size' bytes of storage should be allocated for all threads for the calling class. Returns a unique classThreadId to be used by getStorage method to access the storage. Used by SB_THREAD_INIT_CLASS

static void SbThreadLocalStorage::deleteStorage	(	size_t &	classThreadId,
		const char *	funcName = NULL
	)			[static]

Deletes the local storage for all threads.

Used by SB_THREAD_EXIT_CLASS macro.

static void* SbThreadLocalStorage::getStorage

(

const size_t

classThreadId

)

[static]

Returns a pointer on the storage for the given classThreadId.

This storage is guaranteed to be local to the current thread. The size of the storage is defined by what was requested by createStorage, unless the pointer returned is NULL.

If the storage has not been created, then it will create it if possible.

static bool SbThreadLocalStorage::isInitialized

(

const size_t

classThreadId

)

[static]

Returns true if a TLS storage has already been allocated for the given classThreadId.

The method is used in exitTLSClass() implementation to avoid calling getStorage() which will create the TLS if not found, which is useless as the purpose of exitTLSClass() is to delete associated resources. Used by SB_THREAD_IS_INITIALIZED macro.

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

• Inventor/threads/SbThreadLocalStorage.h