QThreadStorage< T > Class Template Reference

\inmodule QtCore More...

#include <qthreadstorage.h>

Collaboration diagram for QThreadStorage< T >:

Public Member Functions
	QThreadStorage ()=default
	Constructs a new per-thread data storage object.
	~QThreadStorage ()=default
	Destroys the per-thread data storage object.
	QThreadStorage (const QThreadStorage &rhs)=delete
QThreadStorage &	operator= (const QThreadStorage &rhs)=delete
bool	hasLocalData () const
	If T is a pointer type, returns true if the calling thread has non-zero data available.
T &	localData ()
	Returns a reference to the data that was set by the calling thread.
T	localData () const
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Returns a copy of the data that was set by the calling thread.
void	setLocalData (T t)
	Sets the local data for the calling thread to data.

Detailed Description

template<class T>
class QThreadStorage< T >

\inmodule QtCore

The QThreadStorage class provides per-thread data storage.

\threadsafe

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.

QThreadStorage<QCache<QString, SomeClass> > caches;
 
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);
}

Definition at line 153 of file qthreadstorage.h.

Constructor & Destructor Documentation

QThreadStorage() [1/2]

template<class T >

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

default

Constructs a new per-thread data storage object.

~QThreadStorage()

template<class T >

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

default

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()

QThreadStorage() [2/2]

template<class T >

QThreadStorage< T >::QThreadStorage ( const QThreadStorage< T > &  rhs )

delete

Member Function Documentation

hasLocalData()

template<class T >

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()

Definition at line 173 of file qthreadstorage.h.

References qThreadStorage_hasLocalData().

Referenced by QHttpThreadDelegate::~QHttpThreadDelegate(), and QHttpThreadDelegate::startRequest().

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localData() [1/2]

template<class T >

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

hasLocalData()

Definition at line 178 of file qthreadstorage.h.

Referenced by QHttpThreadDelegate::~QHttpThreadDelegate(), QCtfLibImpl::doTracepoint(), QOpenGLEngineThreadStorage::engine(), QOpenGLShaderStorage::shadersForThread(), QHttpThreadDelegate::startRequest(), and QHttpThreadDelegate::startRequestSynchronously().

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localData() [2/2]

template<class T >

template< class T > const T QThreadStorage< T >::localData ( ) const

inline

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Returns a copy of the data that was set by the calling thread.

See also

hasLocalData()

Definition at line 185 of file qthreadstorage.h.

operator=()

template<class T >

QThreadStorage & QThreadStorage< T >::operator= ( const QThreadStorage< T > &  rhs )

delete

setLocalData()

template<class T >

template< class T > void QThreadStorage< T >::setLocalData ( T  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()

Definition at line 190 of file qthreadstorage.h.

Referenced by QHttpThreadDelegate::startRequest(), and QHttpThreadDelegate::startRequestSynchronously().

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

• qtbase/src/corelib/thread/qthreadstorage.h
• qtbase/src/corelib/thread/qthreadstorage.cpp