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diff --git a/src/corelib/thread/qfuture.qdoc b/src/corelib/thread/qfuture.qdoc new file mode 100644 index 0000000000..91414a092a --- /dev/null +++ b/src/corelib/thread/qfuture.qdoc @@ -0,0 +1,697 @@ +/**************************************************************************** +** +** Copyright (C) 2012 Digia Plc and/or its subsidiary(-ies). +** Contact: http://www.qt-project.org/legal +** +** This file is part of the QtCore module of the Qt Toolkit. +** +** $QT_BEGIN_LICENSE:LGPL$ +** Commercial License Usage +** Licensees holding valid commercial Qt licenses may use this file in +** accordance with the commercial license agreement provided with the +** Software or, alternatively, in accordance with the terms contained in +** a written agreement between you and Digia. For licensing terms and +** conditions see http://qt.digia.com/licensing. For further information +** use the contact form at http://qt.digia.com/contact-us. +** +** 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, Digia gives you certain additional +** rights. These rights are described in the Digia Qt LGPL Exception +** version 1.1, included in the file LGPL_EXCEPTION.txt in this package. +** +** GNU General Public License Usage +** Alternatively, this file may be used under the terms of the GNU +** General Public License version 3.0 as published by the Free Software +** Foundation and appearing in the file LICENSE.GPL included in the +** packaging of this file. Please review the following information to +** ensure the GNU General Public License version 3.0 requirements will be +** met: http://www.gnu.org/copyleft/gpl.html. +** +** +** $QT_END_LICENSE$ +** +****************************************************************************/ + +/*! \class QFuture + \threadsafe + \brief The QFuture class represents the result of an asynchronous computation. + \since 4.4 + + \ingroup thread + + To start a computation, use one of the APIs in the + \l {Concurrent Programming}{Qt Concurrent} framework. + + QFuture allows threads to be synchronized against one or more results + which will be ready at a later point in time. The result can be of any type + that has a default constructor and a copy constructor. If a result is not + available at the time of calling the result(), resultAt(), or results() + functions, QFuture will wait until the result becomes available. You can + use the isResultReadyAt() function to determine if a result is ready or + not. For QFuture objects that report more than one result, the + resultCount() function returns the number of continuous results. This + means that it is always safe to iterate through the results from 0 to + resultCount(). + + QFuture provides a \l{Java-style iterators}{Java-style iterator} + (QFutureIterator) and an \l{STL-style iterators}{STL-style iterator} + (QFuture::const_iterator). Using these iterators is another way to access + results in the future. + + QFuture also offers ways to interact with a runnning computation. For + instance, the computation can be canceled with the cancel() function. To + pause the computation, use the setPaused() function or one of the pause(), + resume(), or togglePaused() convenience functions. Be aware that not all + asynchronous computations can be canceled or paused. For example, the + future returned by QtConcurrent::run() cannot be canceled; but the + future returned by QtConcurrent::mappedReduced() can. + + Progress information is provided by the progressValue(), + progressMinimum(), progressMaximum(), and progressText() functions. The + waitForFinished() function causes the calling thread to block and wait for + the computation to finish, ensuring that all results are available. + + The state of the computation represented by a QFuture can be queried using + the isCanceled(), isStarted(), isFinished(), isRunning(), or isPaused() + functions. + + QFuture is a lightweight reference counted class that can be passed by + value. + + QFuture<void> is specialized to not contain any of the result fetching + functions. Any QFuture<T> can be assigned or copied into a QFuture<void> + as well. This is useful if only status or progress information is needed + - not the actual result data. + + To interact with running tasks using signals and slots, use QFutureWatcher. + + \sa QFutureWatcher, {Concurrent Programming}{Qt Concurrent} +*/ + +/*! \fn QFuture::QFuture() + + Constructs an empty future. +*/ + +/*! \fn QFuture::QFuture(const QFuture &other) + + Constructs a copy of \a other. + + \sa operator=() +*/ + +/*! \fn QFuture::QFuture(QFutureInterface<T> *resultHolder) + \internal +*/ + +/*! \fn QFuture::~QFuture() + + Destroys the future. + + Note that this neither waits nor cancels the asynchronous computation. Use + waitForFinished() or QFutureSynchronizer when you need to ensure that the + computation is completed before the future is destroyed. +*/ + +/*! \fn QFuture &QFuture::operator=(const QFuture &other) + + Assigns \a other to this future and returns a reference to this future. +*/ + +/*! \fn bool QFuture::operator==(const QFuture &other) const + + Returns true if \a other is a copy of this future; otherwise returns false. +*/ + +/*! \fn bool QFuture::operator!=(const QFuture &other) const + + Returns true if \a other is \e not a copy of this future; otherwise returns + false. +*/ + +/*! \fn void QFuture::cancel() + + Cancels the asynchronous computation represented by this future. Note that + the cancelation is asynchronous. Use waitForFinished() after calling + cancel() when you need synchronous cancelation. + + Results currently available may still be accessed on a canceled future, + but new results will \e not become available after calling this function. + Any QFutureWatcher object that is watching this future will not deliver + progress and result ready signals on a canceled future. + + Be aware that not all asynchronous computations can be canceled. For + example, the future returned by QtConcurrent::run() cannot be canceled; + but the future returned by QtConcurrent::mappedReduced() can. +*/ + +/*! \fn bool QFuture::isCanceled() const + + Returns true if the asynchronous computation has been canceled with the + cancel() function; otherwise returns false. + + Be aware that the computation may still be running even though this + function returns true. See cancel() for more details. +*/ + +/*! \fn void QFuture::setPaused(bool paused) + + If \a paused is true, this function pauses the asynchronous computation + represented by the future. If the computation is already paused, this + function does nothing. Any QFutureWatcher object that is watching this + future will stop delivering progress and result ready signals while the + future is paused. Signal delivery will continue once the future is + resumed. + + If \a paused is false, this function resumes the asynchronous computation. + If the computation was not previously paused, this function does nothing. + + Be aware that not all computations can be paused. For example, the future + returned by QtConcurrent::run() cannot be paused; but the future returned + by QtConcurrent::mappedReduced() can. + + \sa pause(), resume(), togglePaused() +*/ + +/*! \fn bool QFuture::isPaused() const + + Returns true if the asynchronous computation has been paused with the + pause() function; otherwise returns false. + + Be aware that the computation may still be running even though this + function returns true. See setPaused() for more details. + + \sa setPaused(), togglePaused() +*/ + +/*! \fn void QFuture::pause() + + Pauses the asynchronous computation represented by this future. This is a + convenience method that simply calls setPaused(true). + + \sa resume() +*/ + +/*! \fn void QFuture::resume() + + Resumes the asynchronous computation represented by this future. This is a + convenience method that simply calls setPaused(false). + + \sa pause() +*/ + +/*! \fn void QFuture::togglePaused() + + Toggles the paused state of the asynchronous computation. In other words, + if the computation is currently paused, calling this function resumes it; + if the computation is running, it is paused. This is a convenience method + for calling setPaused(!isPaused()). + + \sa setPaused(), pause(), resume() +*/ + +/*! \fn bool QFuture::isStarted() const + + Returns true if the asynchronous computation represented by this future + has been started; otherwise returns false. +*/ + +/*! \fn bool QFuture::isFinished() const + + Returns true if the asynchronous computation represented by this future + has finished; otherwise returns false. +*/ + +/*! \fn bool QFuture::isRunning() const + + Returns true if the asynchronous computation represented by this future is + currently running; otherwise returns false. +*/ + +/*! \fn int QFuture::resultCount() const + + Returns the number of continuous results available in this future. The real + number of results stored might be different from this value, due to gaps + in the result set. It is always safe to iterate through the results from 0 + to resultCount(). + \sa result(), resultAt(), results() +*/ + +/*! \fn int QFuture::progressValue() const + + Returns the current progress value, which is between the progressMinimum() + and progressMaximum(). + + \sa progressMinimum(), progressMaximum() +*/ + +/*! \fn int QFuture::progressMinimum() const + + Returns the minimum progressValue(). + + \sa progressValue(), progressMaximum() +*/ + +/*! \fn int QFuture::progressMaximum() const + + Returns the maximum progressValue(). + + \sa progressValue(), progressMinimum() +*/ + +/*! \fn QString QFuture::progressText() const + + Returns the (optional) textual representation of the progress as reported + by the asynchronous computation. + + Be aware that not all computations provide a textual representation of the + progress, and as such, this function may return an empty string. +*/ + +/*! \fn void QFuture::waitForFinished() + + Waits for the asynchronous computation to finish (including cancel()ed + computations). +*/ + +/*! \fn T QFuture::result() const + + Returns the first result in the future. If the result is not immediately + available, this function will block and wait for the result to become + available. This is a convenience method for calling resultAt(0). + + \sa resultAt(), results() +*/ + +/*! \fn T QFuture::resultAt(int index) const + + Returns the result at \a index in the future. If the result is not + immediately available, this function will block and wait for the result to + become available. + + \sa result(), results(), resultCount() +*/ + +/*! \fn bool QFuture::isResultReadyAt(int index) const + + Returns true if the result at \a index is immediately available; otherwise + returns false. + + \sa resultAt(), resultCount() +*/ + +/*! \fn QFuture::operator T() const + + Returns the first result in the future. If the result is not immediately + available, this function will block and wait for the result to become + available. This is a convenience method for calling result() or + resultAt(0). + + \sa result(), resultAt(), results() +*/ + +/*! \fn QList<T> QFuture::results() const + + Returns all results from the future. If the results are not immediately + available, this function will block and wait for them to become available. + + \sa result(), resultAt(), resultCount() +*/ + +/*! \fn QFuture::const_iterator QFuture::begin() const + + Returns a const \l{STL-style iterator} pointing to the first result in the + future. + + \sa constBegin(), end() +*/ + +/*! \fn QFuture::const_iterator QFuture::end() const + + Returns a const \l{STL-style iterator} pointing to the imaginary result + after the last result in the future. + + \sa begin(), constEnd() +*/ + +/*! \fn QFuture::const_iterator QFuture::constBegin() const + + Returns a const \l{STL-style iterator} pointing to the first result in the + future. + + \sa begin(), constEnd() +*/ + +/*! \fn QFuture::const_iterator QFuture::constEnd() const + + Returns a const \l{STL-style iterator} pointing to the imaginary result + after the last result in the future. + + \sa constBegin(), end() +*/ + +/*! \class QFuture::const_iterator + \reentrant + \since 4.4 + + \brief The QFuture::const_iterator class provides an STL-style const + iterator for QFuture. + + QFuture provides both \l{STL-style iterators} and \l{Java-style iterators}. + The STL-style iterators are more low-level and more cumbersome to use; on + the other hand, they are slightly faster and, for developers who already + know STL, have the advantage of familiarity. + + The default QFuture::const_iterator constructor creates an uninitialized + iterator. You must initialize it using a QFuture function like + QFuture::constBegin() or QFuture::constEnd() before you start iterating. + Here's a typical loop that prints all the results available in a future: + + \snippet code/src_corelib_thread_qfuture.cpp 0 + + \sa QFutureIterator, QFuture +*/ + +/*! \typedef QFuture::const_iterator::iterator_category + + Typedef for std::bidirectional_iterator_tag. Provided for STL compatibility. +*/ + +/*! \typedef QFuture::const_iterator::difference_type + + Typedef for ptrdiff_t. Provided for STL compatibility. +*/ + +/*! \typedef QFuture::const_iterator::value_type + + Typedef for T. Provided for STL compatibility. +*/ + +/*! \typedef QFuture::const_iterator::pointer + + Typedef for const T *. Provided for STL compatibility. +*/ + +/*! \typedef QFuture::const_iterator::reference + + Typedef for const T &. Provided for STL compatibility. +*/ + +/*! \fn QFuture::const_iterator::const_iterator() + + Constructs an uninitialized iterator. + + Functions like operator*() and operator++() should not be called on an + uninitialized iterartor. Use operator=() to assign a value to it before + using it. + + \sa QFuture::constBegin(), QFuture::constEnd() +*/ + +/*! \fn QFuture::const_iterator::const_iterator(QFuture const * const future, int index) + \internal +*/ + +/*! \fn QFuture::const_iterator::const_iterator(const const_iterator &other) + + Constructs a copy of \a other. +*/ + +/*! \fn QFuture::const_iterator &QFuture::const_iterator::operator=(const const_iterator &other) + + Assigns \a other to this iterator. +*/ + +/*! \fn const T &QFuture::const_iterator::operator*() const + + Returns the current result. +*/ + +/*! \fn const T *QFuture::const_iterator::operator->() const + + Returns a pointer to the current result. +*/ + +/*! \fn bool QFuture::const_iterator::operator!=(const const_iterator &other) const + + Returns true if \a other points to a different result than this iterator; + otherwise returns false. + + \sa operator==() +*/ + +/*! \fn bool QFuture::const_iterator::operator==(const const_iterator &other) const + + Returns true if \a other points to the same result as this iterator; + otherwise returns false. + + \sa operator!=() +*/ + +/*! \fn QFuture::const_iterator &QFuture::const_iterator::operator++() + + The prefix ++ operator (\c{++it}) advances the iterator to the next result + in the future and returns an iterator to the new current result. + + Calling this function on QFuture::constEnd() leads to undefined results. + + \sa operator--() +*/ + +/*! \fn QFuture::const_iterator QFuture::const_iterator::operator++(int) + + \overload + + The postfix ++ operator (\c{it++}) advances the iterator to the next + result in the future and returns an iterator to the previously current + result. +*/ + +/*! \fn QFuture::const_iterator &QFuture::const_iterator::operator--() + + The prefix -- operator (\c{--it}) makes the preceding result current and + returns an iterator to the new current result. + + Calling this function on QFuture::constBegin() leads to undefined results. + + \sa operator++() +*/ + +/*! \fn QFuture::const_iterator QFuture::const_iterator::operator--(int) + + \overload + + The postfix -- operator (\c{it--}) makes the preceding result current and + returns an iterator to the previously current result. +*/ + +/*! \fn QFuture::const_iterator &QFuture::const_iterator::operator+=(int j) + + Advances the iterator by \a j results. (If \a j is negative, the iterator + goes backward.) + + \sa operator-=(), operator+() +*/ + +/*! \fn QFuture::const_iterator &QFuture::const_iterator::operator-=(int j) + + Makes the iterator go back by \a j results. (If \a j is negative, the + iterator goes forward.) + + \sa operator+=(), operator-() +*/ + +/*! \fn QFuture::const_iterator QFuture::const_iterator::operator+(int j) const + + Returns an iterator to the results at \a j positions forward from this + iterator. (If \a j is negative, the iterator goes backward.) + + \sa operator-(), operator+=() +*/ + +/*! \fn QFuture::const_iterator QFuture::const_iterator::operator-(int j) const + + Returns an iterator to the result at \a j positions backward from this + iterator. (If \a j is negative, the iterator goes forward.) + + \sa operator+(), operator-=() +*/ + +/*! \typedef QFuture::ConstIterator + + Qt-style synonym for QFuture::const_iterator. +*/ + +/*! + \class QFutureIterator + \reentrant + \since 4.4 + \inmodule QtCore + + \brief The QFutureIterator class provides a Java-style const iterator for + QFuture. + + QFuture has both \l{Java-style iterators} and \l{STL-style iterators}. The + Java-style iterators are more high-level and easier to use than the + STL-style iterators; on the other hand, they are slightly less efficient. + + An alternative to using iterators is to use index positions. Some QFuture + member functions take an index as their first parameter, making it + possible to access results without using iterators. + + QFutureIterator\<T\> allows you to iterate over a QFuture\<T\>. Note that + there is no mutable iterator for QFuture (unlike the other Java-style + iterators). + + The QFutureIterator constructor takes a QFuture as its argument. After + construction, the iterator is located at the very beginning of the result + list (i.e. before the first result). Here's how to iterate over all the + results sequentially: + + \snippet code/src_corelib_thread_qfuture.cpp 1 + + The next() function returns the next result (waiting for it to become + available, if necessary) from the future and advances the iterator. Unlike + STL-style iterators, Java-style iterators point \e between results rather + than directly \e at results. The first call to next() advances the iterator + to the position between the first and second result, and returns the first + result; the second call to next() advances the iterator to the position + between the second and third result, and returns the second result; and + so on. + + \image javaiterators1.png + + Here's how to iterate over the elements in reverse order: + + \snippet code/src_corelib_thread_qfuture.cpp 2 + + If you want to find all occurrences of a particular value, use findNext() + or findPrevious() in a loop. + + Multiple iterators can be used on the same future. If the future is + modified while a QFutureIterator is active, the QFutureIterator will + continue iterating over the original future, ignoring the modified copy. + + \sa QFuture::const_iterator, QFuture +*/ + +/*! + \fn QFutureIterator::QFutureIterator(const QFuture<T> &future) + + Constructs an iterator for traversing \a future. The iterator is set to be + at the front of the result list (before the first result). + + \sa operator=() +*/ + +/*! \fn QFutureIterator &QFutureIterator::operator=(const QFuture<T> &future) + + Makes the iterator operate on \a future. The iterator is set to be at the + front of the result list (before the first result). + + \sa toFront(), toBack() +*/ + +/*! \fn void QFutureIterator::toFront() + + Moves the iterator to the front of the result list (before the first + result). + + \sa toBack(), next() +*/ + +/*! \fn void QFutureIterator::toBack() + + Moves the iterator to the back of the result list (after the last result). + + \sa toFront(), previous() +*/ + +/*! \fn bool QFutureIterator::hasNext() const + + Returns true if there is at least one result ahead of the iterator, e.g., + the iterator is \e not at the back of the result list; otherwise returns + false. + + \sa hasPrevious(), next() +*/ + +/*! \fn const T &QFutureIterator::next() + + Returns the next result and advances the iterator by one position. + + Calling this function on an iterator located at the back of the result + list leads to undefined results. + + \sa hasNext(), peekNext(), previous() +*/ + +/*! \fn const T &QFutureIterator::peekNext() const + + Returns the next result without moving the iterator. + + Calling this function on an iterator located at the back of the result + list leads to undefined results. + + \sa hasNext(), next(), peekPrevious() +*/ + +/*! \fn bool QFutureIterator::hasPrevious() const + + Returns true if there is at least one result ahead of the iterator, e.g., + the iterator is \e not at the front of the result list; otherwise returns + false. + + \sa hasNext(), previous() +*/ + +/*! \fn const T &QFutureIterator::previous() + + Returns the previous result and moves the iterator back by one position. + + Calling this function on an iterator located at the front of the result + list leads to undefined results. + + \sa hasPrevious(), peekPrevious(), next() +*/ + +/*! \fn const T &QFutureIterator::peekPrevious() const + + Returns the previous result without moving the iterator. + + Calling this function on an iterator located at the front of the result + list leads to undefined results. + + \sa hasPrevious(), previous(), peekNext() +*/ + +/*! \fn bool QFutureIterator::findNext(const T &value) + + Searches for \a value starting from the current iterator position forward. + Returns true if \a value is found; otherwise returns false. + + After the call, if \a value was found, the iterator is positioned just + after the matching result; otherwise, the iterator is positioned at the + back of the result list. + + \sa findPrevious() +*/ + +/*! \fn bool QFutureIterator::findPrevious(const T &value) + + Searches for \a value starting from the current iterator position + backward. Returns true if \a value is found; otherwise returns false. + + After the call, if \a value was found, the iterator is positioned just + before the matching result; otherwise, the iterator is positioned at the + front of the result list. + + \sa findNext() +*/ |