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Diffstat (limited to 'src/corelib/thread/qthreadstorage.cpp')
-rw-r--r-- | src/corelib/thread/qthreadstorage.cpp | 329 |
1 files changed, 329 insertions, 0 deletions
diff --git a/src/corelib/thread/qthreadstorage.cpp b/src/corelib/thread/qthreadstorage.cpp new file mode 100644 index 0000000000..2b353333ee --- /dev/null +++ b/src/corelib/thread/qthreadstorage.cpp @@ -0,0 +1,329 @@ +/**************************************************************************** +** +** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies). +** All rights reserved. +** Contact: Nokia Corporation (qt-info@nokia.com) +** +** This file is part of the QtCore module of the Qt Toolkit. +** +** $QT_BEGIN_LICENSE:LGPL$ +** No Commercial Usage +** This file contains pre-release code and may not be distributed. +** You may use this file in accordance with the terms and conditions +** contained in the Technology Preview License Agreement accompanying +** this package. +** +** GNU Lesser General Public License Usage +** Alternatively, this file may be used under the terms of the GNU Lesser +** General Public License version 2.1 as published by the Free Software +** Foundation and appearing in the file LICENSE.LGPL included in the +** packaging of this file. Please review the following information to +** ensure the GNU Lesser General Public License version 2.1 requirements +** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html. +** +** In addition, as a special exception, Nokia gives you certain additional +** rights. These rights are described in the Nokia Qt LGPL Exception +** version 1.1, included in the file LGPL_EXCEPTION.txt in this package. +** +** If you have questions regarding the use of this file, please contact +** Nokia at qt-info@nokia.com. +** +** +** +** +** +** +** +** +** $QT_END_LICENSE$ +** +****************************************************************************/ + +#include "qthreadstorage.h" + +#ifndef QT_NO_THREAD +#include "qthread.h" +#include "qthread_p.h" +#include "qmutex.h" + +#include <string.h> + +QT_BEGIN_NAMESPACE + +// #define THREADSTORAGE_DEBUG +#ifdef THREADSTORAGE_DEBUG +# define DEBUG_MSG qtsDebug + +# include <stdio.h> +# include <stdarg.h> +void qtsDebug(const char *fmt, ...) +{ + va_list va; + va_start(va, fmt); + + fprintf(stderr, "QThreadStorage: "); + vfprintf(stderr, fmt, va); + fprintf(stderr, "\n"); + + va_end(va); +} +#else +# define DEBUG_MSG if(false)qDebug +#endif + +Q_GLOBAL_STATIC(QMutex, mutex) +typedef QVector<void (*)(void *)> DestructorMap; +Q_GLOBAL_STATIC(DestructorMap, destructors) + +QThreadStorageData::QThreadStorageData(void (*func)(void *)) +{ + QMutexLocker locker(mutex()); + DestructorMap *destr = destructors(); + if (!destr) { + /* + the destructors vector has already been destroyed, yet a new + QThreadStorage is being allocated. this can only happen during global + destruction, at which point we assume that there is only one thread. + in order to keep QThreadStorage working, we need somewhere to store + the data, best place we have in this situation is at the tail of the + current thread's tls vector. the destructor is ignored, since we have + no where to store it, and no way to actually call it. + */ + QThreadData *data = QThreadData::current(); + id = data->tls.count(); + DEBUG_MSG("QThreadStorageData: Allocated id %d, destructor %p cannot be stored", id, func); + return; + } + for (id = 0; id < destr->count(); id++) { + if (destr->at(id) == 0) + break; + } + if (id == destr->count()) { + destr->append(func); + } else { + (*destr)[id] = func; + } + DEBUG_MSG("QThreadStorageData: Allocated id %d, destructor %p", id, func); +} + +QThreadStorageData::~QThreadStorageData() +{ + DEBUG_MSG("QThreadStorageData: Released id %d", id); + QMutexLocker locker(mutex()); + if (destructors()) + (*destructors())[id] = 0; +} + +void **QThreadStorageData::get() const +{ + QThreadData *data = QThreadData::current(); + if (!data) { + qWarning("QThreadStorage::get: QThreadStorage can only be used with threads started with QThread"); + return 0; + } + QVector<void *> &tls = data->tls; + if (tls.size() <= id) + tls.resize(id + 1); + void **v = &tls[id]; + + DEBUG_MSG("QThreadStorageData: Returning storage %d, data %p, for thread %p", + id, + *v, + data->thread); + + return *v ? v : 0; +} + +void **QThreadStorageData::set(void *p) +{ + QThreadData *data = QThreadData::current(); + if (!data) { + qWarning("QThreadStorage::set: QThreadStorage can only be used with threads started with QThread"); + return 0; + } + QVector<void *> &tls = data->tls; + if (tls.size() <= id) + tls.resize(id + 1); + + void *&value = tls[id]; + // delete any previous data + if (value != 0) { + DEBUG_MSG("QThreadStorageData: Deleting previous storage %d, data %p, for thread %p", + id, + value, + data->thread); + + QMutexLocker locker(mutex()); + DestructorMap *destr = destructors(); + void (*destructor)(void *) = destr ? destr->value(id) : 0; + locker.unlock(); + + void *q = value; + value = 0; + + if (destructor) + destructor(q); + } + + // store new data + value = p; + DEBUG_MSG("QThreadStorageData: Set storage %d for thread %p to %p", id, data->thread, p); + return &value; +} + +void QThreadStorageData::finish(void **p) +{ + QVector<void *> *tls = reinterpret_cast<QVector<void *> *>(p); + if (!tls || tls->isEmpty() || !mutex()) + return; // nothing to do + + DEBUG_MSG("QThreadStorageData: Destroying storage for thread %p", QThread::currentThread()); + while (!tls->isEmpty()) { + void *&value = tls->last(); + void *q = value; + value = 0; + int i = tls->size() - 1; + tls->resize(i); + + if (!q) { + // data already deleted + continue; + } + + QMutexLocker locker(mutex()); + void (*destructor)(void *) = destructors()->value(i); + locker.unlock(); + + if (!destructor) { + if (QThread::currentThread()) + qWarning("QThreadStorage: Thread %p exited after QThreadStorage %d destroyed", + QThread::currentThread(), i); + continue; + } + destructor(q); //crash here might mean the thread exited after qthreadstorage was destroyed + + if (tls->size() > i) { + //re reset the tls in case it has been recreated by its own destructor. + (*tls)[i] = 0; + } + } + tls->clear(); +} + +/*! + \class QThreadStorage + \brief The QThreadStorage class provides per-thread data storage. + + \threadsafe + + \ingroup thread + + 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 initializiation. + + If T is a pointer type, QThreadStorage takes ownership of the data + (which must be created on the heap with \c 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. + + \snippet doc/src/snippets/threads/threads.cpp 7 + \snippet doc/src/snippets/threads/threads.cpp 8 + \snippet doc/src/snippets/threads/threads.cpp 9 + + \section1 Caveats + + \list + + \o 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. + + \o QThreadStorage can be used to store data for the \c main() + thread. QThreadStorage deletes all data set for the \c main() + thread when QApplication is destroyed, regardless of whether or + not the \c main() thread has actually finished. + + \endlist + + \sa QThread +*/ + +/*! + \fn QThreadStorage::QThreadStorage() + + Constructs a new per-thread data storage object. +*/ + +/*! + \fn QThreadStorage::~QThreadStorage() + + 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. + + \sa hasLocalData() +*/ + +/*! + \fn bool QThreadStorage::hasLocalData() const + + 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. + + \sa localData() +*/ + +/*! + \fn T &QThreadStorage::localData() + + 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. + + \sa hasLocalData() +*/ + +/*! + \fn const T QThreadStorage::localData() const + \overload + + Returns a copy of the data that was set by the calling thread. + + \sa hasLocalData() +*/ + +/*! + \fn void QThreadStorage::setLocalData(T data) + + Sets the local data for the calling thread to \a 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. + + \sa localData(), hasLocalData() +*/ + +#endif // QT_NO_THREAD + +QT_END_NAMESPACE |