CopperSpice API  1.7.2
QThreadStorage< T > Class Template Reference

The QThreadStorage class provides per-thread data storage. More...

Public Methods

 QThreadStorage ()
 
 ~QThreadStorage ()
 
bool hasLocalData () const
 
T & localData ()
 
localData () const
 
void setLocalData (T data)
 

Detailed Description

template<class T>
class QThreadStorage< T >

The QThreadStorage class provides per-thread data storage.

QThreadStorage is a template class that provides per-thread data storage.

The setLocalData() function stores a single thread-specific value for the calling thread. The data can be accessed later using localData().

The hasLocalData() function allows the programmer to determine if data has previously been set using the setLocalData() function. This is also useful for lazy initialization.

If T is a pointer type, QThreadStorage takes ownership of the data (which must be created on the heap with new) and deletes it when the thread exits, either normally or via termination.

For example, the following code uses QThreadStorage to store a single cache for each thread that calls the cacheObject() and removeFromCache() functions. The cache is automatically deleted when the calling thread exits.

void cacheObject(const QString &key, SomeClass *object)
{
caches.localData().insert(key, object);
}
void removeFromCache(const QString &key)
{
if (!caches.hasLocalData())
return;
caches.localData().remove(key);
}

Caveats

  • The QThreadStorage destructor does not delete per-thread data. QThreadStorage only deletes per-thread data when the thread exits or when setLocalData() is called multiple times.
  • QThreadStorage can be used to store data for the main() thread. QThreadStorage deletes all data set for the main() thread when QApplication is destroyed, regardless of whether or not the main() thread has actually finished.
See also
QThread

Constructor & Destructor Documentation

template<class T >
QThreadStorage< T >::QThreadStorage ( )
inline

Constructs a new per-thread data storage object.

template<class T >
QThreadStorage< T >::~QThreadStorage ( )
inline

Destroys the per-thread data storage object.

Note: The per-thread data stored is not deleted. Any data left in QThreadStorage is leaked. Make sure that all threads using QThreadStorage have exited before deleting the QThreadStorage.

See also
hasLocalData()

Method Documentation

template<class T >
bool QThreadStorage< T >::hasLocalData ( ) const
inline

If T is a pointer type, returns true if the calling thread has non-zero data available. If T is a value type, returns whether the data has already been constructed by calling setLocalData or localData.

See also
localData()
template<class T >
T & QThreadStorage< T >::localData ( )
inline

Returns a reference to the data that was set by the calling thread. If no data has been set, this will create a default constructed instance of type T.

See also
setLocalData(), hasLocalData()
template<class T >
T QThreadStorage< T >::localData ( ) const
inline

Returns a copy of the data that was set by the calling thread.

See also
hasLocalData()
template<class T >
void QThreadStorage< T >::setLocalData ( data)
inline

Sets the local data for the calling thread to data. It can be accessed later using the localData() functions.

If T is a pointer type, QThreadStorage takes ownership of the data and deletes it automatically either when the thread exits (either normally or via termination) or when setLocalData() is called again.

See also
localData(), hasLocalData()