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/****************************************************************************
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**
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** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
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** All rights reserved.
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** Contact: Nokia Corporation (qt-info@nokia.com)
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**
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** This file is part of the QtCore module of the Qt Toolkit.
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**
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** $QT_BEGIN_LICENSE:LGPL$
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** No Commercial Usage
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** This file contains pre-release code and may not be distributed.
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** You may use this file in accordance with the terms and conditions
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** contained in the Technology Preview License Agreement accompanying
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** this package.
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**
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** GNU Lesser General Public License Usage
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** Alternatively, this file may be used under the terms of the GNU Lesser
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** General Public License version 2.1 as published by the Free Software
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** Foundation and appearing in the file LICENSE.LGPL included in the
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** packaging of this file. Please review the following information to
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** ensure the GNU Lesser General Public License version 2.1 requirements
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** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
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**
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** In addition, as a special exception, Nokia gives you certain additional
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** rights. These rights are described in the Nokia Qt LGPL Exception
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** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
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**
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** If you have questions regarding the use of this file, please contact
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** Nokia at qt-info@nokia.com.
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**
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**
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**
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**
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**
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** $QT_END_LICENSE$
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**
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****************************************************************************/
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/*!
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\class QAtomicInt
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\brief The QAtomicInt class provides platform-independent atomic operations on integers.
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\since 4.4
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\ingroup thread
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For atomic operations on pointers, see the QAtomicPointer class.
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An complex operation that completes without interruption is said
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to be \e atomic. The QAtomicInt class provides atomic reference
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counting, test-and-set, fetch-and-store, and fetch-and-add for
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integers.
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\section1 Non-atomic convenience operators
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For convenience, QAtomicInt provides integer comparison, cast, and
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assignment operators. Note that a combination of these operators
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is \e not an atomic operation.
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\section1 The Atomic API
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\section2 Reference counting
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The ref() and deref() functions provide an efficient reference
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counting API. The return value of these functions are used to
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indicate when the last reference has been released. These
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functions allow you to implement your own implicitly shared
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classes.
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\snippet doc/src/snippets/code/src_corelib_thread_qatomic.cpp 0
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\section2 Memory ordering
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QAtomicInt provides several implementations of the atomic
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test-and-set, fetch-and-store, and fetch-and-add functions. Each
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implementation defines a memory ordering semantic that describes
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how memory accesses surrounding the atomic instruction are
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executed by the processor. Since many modern architectures allow
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out-of-order execution and memory ordering, using the correct
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semantic is necessary to ensure that your application functions
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properly on all processors.
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\list
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\o Relaxed - memory ordering is unspecified, leaving the compiler
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and processor to freely reorder memory accesses.
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\o Acquire - memory access following the atomic operation (in
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program order) may not be re-ordered before the atomic operation.
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\o Release - memory access before the atomic operation (in program
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order) may not be re-ordered after the atomic operation.
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\o Ordered - the same Acquire and Release semantics combined.
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\endlist
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\section2 Test-and-set
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If the current value of the QAtomicInt is an expected value, the
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test-and-set functions assign a new value to the QAtomicInt and
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return true. If values are \a not the same, these functions do
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nothing and return false. This operation equates to the following
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code:
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\snippet doc/src/snippets/code/src_corelib_thread_qatomic.cpp 1
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There are 4 test-and-set functions: testAndSetRelaxed(),
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testAndSetAcquire(), testAndSetRelease(), and
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testAndSetOrdered(). See above for an explanation of the different
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memory ordering semantics.
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\section2 Fetch-and-store
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The atomic fetch-and-store functions read the current value of the
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QAtomicInt and then assign a new value, returning the original
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value. This operation equates to the following code:
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\snippet doc/src/snippets/code/src_corelib_thread_qatomic.cpp 2
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There are 4 fetch-and-store functions: fetchAndStoreRelaxed(),
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fetchAndStoreAcquire(), fetchAndStoreRelease(), and
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fetchAndStoreOrdered(). See above for an explanation of the
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different memory ordering semantics.
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\section2 Fetch-and-add
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The atomic fetch-and-add functions read the current value of the
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QAtomicInt and then add the given value to the current value,
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returning the original value. This operation equates to the
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following code:
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\snippet doc/src/snippets/code/src_corelib_thread_qatomic.cpp 3
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There are 4 fetch-and-add functions: fetchAndAddRelaxed(),
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fetchAndAddAcquire(), fetchAndAddRelease(), and
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fetchAndAddOrdered(). See above for an explanation of the
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different memory ordering semantics.
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\section1 Feature Tests for the Atomic API
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Providing a platform-independent atomic API that works on all
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processors is challenging. The API provided by QAtomicInt is
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guaranteed to work atomically on all processors. However, since
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not all processors implement support for every operation provided
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by QAtomicInt, it is necessary to expose information about the
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processor.
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You can check at compile time which features are supported on your
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hardware using various macros. These will tell you if your
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hardware always, sometimes, or does not support a particular
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operation. The macros have the form
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Q_ATOMIC_INT_\e{OPERATION}_IS_\e{HOW}_NATIVE. \e{OPERATION}
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is one of REFERENCE_COUNTING, TEST_AND_SET,
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FETCH_AND_STORE, or FETCH_AND_ADD, and \e{HOW} is one of
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ALWAYS, SOMETIMES, or NOT. There will always be exactly one
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defined macro per operation. For example, if
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Q_ATOMIC_INT_REFERENCE_COUNTING_IS_ALWAYS_NATIVE is defined,
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neither Q_ATOMIC_INT_REFERENCE_COUNTING_IS_SOMETIMES_NATIVE nor
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Q_ATOMIC_INT_REFERENCE_COUNTING_IS_NOT_NATIVE will be defined.
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An operation that completes in constant time is said to be
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wait-free. Such operations are not implemented using locks or
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loops of any kind. For atomic operations that are always
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supported, and that are wait-free, Qt defines the
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Q_ATOMIC_INT_\e{OPERATION}_IS_WAIT_FREE in addition to the
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Q_ATOMIC_INT_\e{OPERATION}_IS_ALWAYS_NATIVE.
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In cases where an atomic operation is only supported in newer
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generations of the processor, QAtomicInt also provides a way to
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check at runtime what your hardware supports with the
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isReferenceCountingNative(), isTestAndSetNative(),
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isFetchAndStoreNative(), and isFetchAndAddNative()
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functions. Wait-free implementations can be detected using the
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isReferenceCountingWaitFree(), isTestAndSetWaitFree(),
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isFetchAndStoreWaitFree(), and isFetchAndAddWaitFree() functions.
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Below is a complete list of all feature macros for QAtomicInt:
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\list
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\o Q_ATOMIC_INT_REFERENCE_COUNTING_IS_ALWAYS_NATIVE
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\o Q_ATOMIC_INT_REFERENCE_COUNTING_IS_SOMETIMES_NATIVE
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\o Q_ATOMIC_INT_REFERENCE_COUNTING_IS_NOT_NATIVE
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\o Q_ATOMIC_INT_REFERENCE_COUNTING_IS_WAIT_FREE
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\o Q_ATOMIC_INT_TEST_AND_SET_IS_ALWAYS_NATIVE
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\o Q_ATOMIC_INT_TEST_AND_SET_IS_SOMETIMES_NATIVE
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\o Q_ATOMIC_INT_TEST_AND_SET_IS_NOT_NATIVE
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\o Q_ATOMIC_INT_TEST_AND_SET_IS_WAIT_FREE
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\o Q_ATOMIC_INT_FETCH_AND_STORE_IS_ALWAYS_NATIVE
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\o Q_ATOMIC_INT_FETCH_AND_STORE_IS_SOMETIMES_NATIVE
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\o Q_ATOMIC_INT_FETCH_AND_STORE_IS_NOT_NATIVE
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\o Q_ATOMIC_INT_FETCH_AND_STORE_IS_WAIT_FREE
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\o Q_ATOMIC_INT_FETCH_AND_ADD_IS_ALWAYS_NATIVE
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\o Q_ATOMIC_INT_FETCH_AND_ADD_IS_SOMETIMES_NATIVE
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\o Q_ATOMIC_INT_FETCH_AND_ADD_IS_NOT_NATIVE
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\o Q_ATOMIC_INT_FETCH_AND_ADD_IS_WAIT_FREE
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\endlist
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\sa QAtomicPointer
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*/
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/*! \fn QAtomicInt::QAtomicInt(int value)
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Constructs a QAtomicInt with the given \a value.
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*/
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/*! \fn QAtomicInt::QAtomicInt(const QAtomicInt &other)
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Constructs a copy of \a other.
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*/
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/*! \fn QAtomicInt &QAtomicInt::operator=(int value)
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Assigns the \a value to this QAtomicInt and returns a reference to
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this QAtomicInt.
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*/
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/*! \fn QAtomicInt &QAtomicInt::operator=(const QAtomicInt &other)
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Assigns \a other to this QAtomicInt and returns a reference to
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this QAtomicInt.
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*/
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/*! \fn bool QAtomicInt::operator==(int value) const
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Returns true if the \a value is equal to the value in this
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QAtomicInt; otherwise returns false.
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*/
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/*! \fn bool QAtomicInt::operator!=(int value) const
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Returns true if the value of this QAtomicInt is not equal to \a
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value; otherwise returns false.
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*/
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/*! \fn bool QAtomicInt::operator!() const
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Returns true is the value of this QAtomicInt is zero; otherwise
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returns false.
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*/
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/*! \fn QAtomicInt::operator int() const
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Returns the value stored by the QAtomicInt object as an integer.
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*/
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/*! \fn bool QAtomicInt::isReferenceCountingNative()
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Returns true if reference counting is implemented using atomic
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processor instructions, false otherwise.
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*/
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/*! \fn bool QAtomicInt::isReferenceCountingWaitFree()
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Returns true if atomic reference counting is wait-free, false
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otherwise.
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*/
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/*! \fn bool QAtomicInt::ref()
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Atomically increments the value of this QAtomicInt. Returns true
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if the new value is non-zero, false otherwise.
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This function uses \e ordered \l {QAtomicInt#Memory
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ordering}{memory ordering} semantics, which ensures that memory
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access before and after the atomic operation (in program order)
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may not be re-ordered.
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\sa deref()
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*/
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/*! \fn bool QAtomicInt::deref()
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Atomically decrements the value of this QAtomicInt. Returns true
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if the new value is non-zero, false otherwise.
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This function uses \e ordered \l {QAtomicInt#Memory
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ordering}{memory ordering} semantics, which ensures that memory
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access before and after the atomic operation (in program order)
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may not be re-ordered.
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\sa ref()
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*/
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/*! \fn bool QAtomicInt::isTestAndSetNative()
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Returns true if test-and-set is implemented using atomic processor
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instructions, false otherwise.
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*/
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/*! \fn bool QAtomicInt::isTestAndSetWaitFree()
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Returns true if atomic test-and-set is wait-free, false otherwise.
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*/
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/*! \fn bool QAtomicInt::testAndSetRelaxed(int expectedValue, int newValue)
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Atomic test-and-set.
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If the current value of this QAtomicInt is the \a expectedValue,
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the test-and-set functions assign the \a newValue to this
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QAtomicInt and return true. If the values are \e not the same,
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this function does nothing and returns false.
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This function uses \e relaxed \l {QAtomicInt#Memory
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ordering}{memory ordering} semantics, leaving the compiler and
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processor to freely reorder memory accesses.
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*/
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/*! \fn bool QAtomicInt::testAndSetAcquire(int expectedValue, int newValue)
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Atomic test-and-set.
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If the current value of this QAtomicInt is the \a expectedValue,
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the test-and-set functions assign the \a newValue to this
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QAtomicInt and return true. If the values are \e not the same,
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this function does nothing and returns false.
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This function uses \e acquire \l {QAtomicInt#Memory
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ordering}{memory ordering} semantics, which ensures that memory
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access following the atomic operation (in program order) may not
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be re-ordered before the atomic operation.
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*/
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/*! \fn bool QAtomicInt::testAndSetRelease(int expectedValue, int newValue)
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Atomic test-and-set.
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If the current value of this QAtomicInt is the \a expectedValue,
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the test-and-set functions assign the \a newValue to this
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QAtomicInt and return true. If the values are \e not the same,
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this function does nothing and returns false.
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This function uses \e release \l {QAtomicInt#Memory
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ordering}{memory ordering} semantics, which ensures that memory
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access before the atomic operation (in program order) may not be
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re-ordered after the atomic operation.
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*/
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/*! \fn bool QAtomicInt::testAndSetOrdered(int expectedValue, int newValue)
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Atomic test-and-set.
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If the current value of this QAtomicInt is the \a expectedValue,
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the test-and-set functions assign the \a newValue to this
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QAtomicInt and return true. If the values are \e not the same,
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this function does nothing and returns false.
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This function uses \e ordered \l {QAtomicInt#Memory
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ordering}{memory ordering} semantics, which ensures that memory
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access before and after the atomic operation (in program order)
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may not be re-ordered.
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*/
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/*! \fn bool QAtomicInt::isFetchAndStoreNative()
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Returns true if fetch-and-store is implemented using atomic
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processor instructions, false otherwise.
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*/
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/*! \fn bool QAtomicInt::isFetchAndStoreWaitFree()
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Returns true if atomic fetch-and-store is wait-free, false
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otherwise.
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*/
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/*! \fn int QAtomicInt::fetchAndStoreRelaxed(int newValue)
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Atomic fetch-and-store.
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Reads the current value of this QAtomicInt and then assigns it the
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\a newValue, returning the original value.
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This function uses \e relaxed \l {QAtomicInt#Memory
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ordering}{memory ordering} semantics, leaving the compiler and
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processor to freely reorder memory accesses.
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*/
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/*! \fn int QAtomicInt::fetchAndStoreAcquire(int newValue)
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Atomic fetch-and-store.
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Reads the current value of this QAtomicInt and then assigns it the
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\a newValue, returning the original value.
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This function uses \e acquire \l {QAtomicInt#Memory
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ordering}{memory ordering} semantics, which ensures that memory
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access following the atomic operation (in program order) may not
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be re-ordered before the atomic operation.
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*/
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/*! \fn int QAtomicInt::fetchAndStoreRelease(int newValue)
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Atomic fetch-and-store.
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Reads the current value of this QAtomicInt and then assigns it the
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\a newValue, returning the original value.
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This function uses \e release \l {QAtomicInt#Memory
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ordering}{memory ordering} semantics, which ensures that memory
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access before the atomic operation (in program order) may not be
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re-ordered after the atomic operation.
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*/
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|
409 |
|
|
410 |
/*! \fn int QAtomicInt::fetchAndStoreOrdered(int newValue)
|
|
411 |
|
|
412 |
Atomic fetch-and-store.
|
|
413 |
|
|
414 |
Reads the current value of this QAtomicInt and then assigns it the
|
|
415 |
\a newValue, returning the original value.
|
|
416 |
|
|
417 |
This function uses \e ordered \l {QAtomicInt#Memory
|
|
418 |
ordering}{memory ordering} semantics, which ensures that memory
|
|
419 |
access before and after the atomic operation (in program order)
|
|
420 |
may not be re-ordered.
|
|
421 |
*/
|
|
422 |
|
|
423 |
/*! \fn bool QAtomicInt::isFetchAndAddNative()
|
|
424 |
|
|
425 |
Returns true if fetch-and-add is implemented using atomic
|
|
426 |
processor instructions, false otherwise.
|
|
427 |
*/
|
|
428 |
|
|
429 |
/*! \fn bool QAtomicInt::isFetchAndAddWaitFree()
|
|
430 |
|
|
431 |
Returns true if atomic fetch-and-add is wait-free, false
|
|
432 |
otherwise.
|
|
433 |
*/
|
|
434 |
|
|
435 |
/*! \fn int QAtomicInt::fetchAndAddRelaxed(int valueToAdd)
|
|
436 |
|
|
437 |
Atomic fetch-and-add.
|
|
438 |
|
|
439 |
Reads the current value of this QAtomicInt and then adds
|
|
440 |
\a valueToAdd to the current value, returning the original value.
|
|
441 |
|
|
442 |
This function uses \e relaxed \l {QAtomicInt#Memory
|
|
443 |
ordering}{memory ordering} semantics, leaving the compiler and
|
|
444 |
processor to freely reorder memory accesses.
|
|
445 |
*/
|
|
446 |
|
|
447 |
/*! \fn int QAtomicInt::fetchAndAddAcquire(int valueToAdd)
|
|
448 |
|
|
449 |
Atomic fetch-and-add.
|
|
450 |
|
|
451 |
Reads the current value of this QAtomicInt and then adds
|
|
452 |
\a valueToAdd to the current value, returning the original value.
|
|
453 |
|
|
454 |
This function uses \e acquire \l {QAtomicInt#Memory
|
|
455 |
ordering}{memory ordering} semantics, which ensures that memory
|
|
456 |
access following the atomic operation (in program order) may not
|
|
457 |
be re-ordered before the atomic operation.
|
|
458 |
*/
|
|
459 |
|
|
460 |
/*! \fn int QAtomicInt::fetchAndAddRelease(int valueToAdd)
|
|
461 |
|
|
462 |
Atomic fetch-and-add.
|
|
463 |
|
|
464 |
Reads the current value of this QAtomicInt and then adds
|
|
465 |
\a valueToAdd to the current value, returning the original value.
|
|
466 |
|
|
467 |
This function uses \e release \l {QAtomicInt#Memory
|
|
468 |
ordering}{memory ordering} semantics, which ensures that memory
|
|
469 |
access before the atomic operation (in program order) may not be
|
|
470 |
re-ordered after the atomic operation.
|
|
471 |
*/
|
|
472 |
|
|
473 |
/*! \fn int QAtomicInt::fetchAndAddOrdered(int valueToAdd)
|
|
474 |
|
|
475 |
Atomic fetch-and-add.
|
|
476 |
|
|
477 |
Reads the current value of this QAtomicInt and then adds
|
|
478 |
\a valueToAdd to the current value, returning the original value.
|
|
479 |
|
|
480 |
This function uses \e ordered \l {QAtomicInt#Memory
|
|
481 |
ordering}{memory ordering} semantics, which ensures that memory
|
|
482 |
access before and after the atomic operation (in program order)
|
|
483 |
may not be re-ordered.
|
|
484 |
*/
|
|
485 |
|
|
486 |
/*!
|
|
487 |
\macro Q_ATOMIC_INT_REFERENCE_COUNTING_IS_ALWAYS_NATIVE
|
|
488 |
\relates QAtomicInt
|
|
489 |
|
|
490 |
This macro is defined if and only if all generations of your
|
|
491 |
processor support atomic reference counting.
|
|
492 |
*/
|
|
493 |
|
|
494 |
/*!
|
|
495 |
\macro Q_ATOMIC_INT_REFERENCE_COUNTING_IS_SOMETIMES_NATIVE
|
|
496 |
\relates QAtomicInt
|
|
497 |
|
|
498 |
This macro is defined when only certain generations of the
|
|
499 |
processor support atomic reference counting. Use the
|
|
500 |
QAtomicInt::isReferenceCountingNative() function to check what
|
|
501 |
your processor supports.
|
|
502 |
*/
|
|
503 |
|
|
504 |
/*!
|
|
505 |
\macro Q_ATOMIC_INT_REFERENCE_COUNTING_IS_NOT_NATIVE
|
|
506 |
\relates QAtomicInt
|
|
507 |
|
|
508 |
This macro is defined when the hardware does not support atomic
|
|
509 |
reference counting.
|
|
510 |
*/
|
|
511 |
|
|
512 |
/*!
|
|
513 |
\macro Q_ATOMIC_INT_REFERENCE_COUNTING_IS_WAIT_FREE
|
|
514 |
\relates QAtomicInt
|
|
515 |
|
|
516 |
This macro is defined together with
|
|
517 |
Q_ATOMIC_INT_REFERENCE_COUNTING_IS_ALWAYS_NATIVE to indicate that
|
|
518 |
the reference counting is wait-free.
|
|
519 |
*/
|
|
520 |
|
|
521 |
/*!
|
|
522 |
\macro Q_ATOMIC_INT_TEST_AND_SET_IS_ALWAYS_NATIVE
|
|
523 |
\relates QAtomicInt
|
|
524 |
|
|
525 |
This macro is defined if and only if your processor supports
|
|
526 |
atomic test-and-set on integers.
|
|
527 |
*/
|
|
528 |
|
|
529 |
/*!
|
|
530 |
\macro Q_ATOMIC_INT_TEST_AND_SET_IS_SOMETIMES_NATIVE
|
|
531 |
\relates QAtomicInt
|
|
532 |
|
|
533 |
This macro is defined when only certain generations of the
|
|
534 |
processor support atomic test-and-set on integers. Use the
|
|
535 |
QAtomicInt::isTestAndSetNative() function to check what your
|
|
536 |
processor supports.
|
|
537 |
*/
|
|
538 |
|
|
539 |
/*!
|
|
540 |
\macro Q_ATOMIC_INT_TEST_AND_SET_IS_NOT_NATIVE
|
|
541 |
\relates QAtomicInt
|
|
542 |
|
|
543 |
This macro is defined when the hardware does not support atomic
|
|
544 |
test-and-set on integers.
|
|
545 |
*/
|
|
546 |
|
|
547 |
/*!
|
|
548 |
\macro Q_ATOMIC_INT_TEST_AND_SET_IS_WAIT_FREE
|
|
549 |
\relates QAtomicInt
|
|
550 |
|
|
551 |
This macro is defined together with
|
|
552 |
Q_ATOMIC_INT_TEST_AND_SET_IS_ALWAYS_NATIVE to indicate that the
|
|
553 |
atomic test-and-set on integers is wait-free.
|
|
554 |
*/
|
|
555 |
|
|
556 |
/*!
|
|
557 |
\macro Q_ATOMIC_INT_FETCH_AND_STORE_IS_ALWAYS_NATIVE
|
|
558 |
\relates QAtomicInt
|
|
559 |
|
|
560 |
This macro is defined if and only if your processor supports
|
|
561 |
atomic fetch-and-store on integers.
|
|
562 |
*/
|
|
563 |
|
|
564 |
/*!
|
|
565 |
\macro Q_ATOMIC_INT_FETCH_AND_STORE_IS_SOMETIMES_NATIVE
|
|
566 |
\relates QAtomicInt
|
|
567 |
|
|
568 |
This macro is defined when only certain generations of the
|
|
569 |
processor support atomic fetch-and-store on integers. Use the
|
|
570 |
QAtomicInt::isFetchAndStoreNative() function to check what your
|
|
571 |
processor supports.
|
|
572 |
*/
|
|
573 |
|
|
574 |
/*!
|
|
575 |
\macro Q_ATOMIC_INT_FETCH_AND_STORE_IS_NOT_NATIVE
|
|
576 |
\relates QAtomicInt
|
|
577 |
|
|
578 |
This macro is defined when the hardware does not support atomic
|
|
579 |
fetch-and-store on integers.
|
|
580 |
*/
|
|
581 |
|
|
582 |
/*!
|
|
583 |
\macro Q_ATOMIC_INT_FETCH_AND_STORE_IS_WAIT_FREE
|
|
584 |
\relates QAtomicInt
|
|
585 |
|
|
586 |
This macro is defined together with
|
|
587 |
Q_ATOMIC_INT_FETCH_AND_STORE_IS_ALWAYS_NATIVE to indicate that the
|
|
588 |
atomic fetch-and-store on integers is wait-free.
|
|
589 |
*/
|
|
590 |
|
|
591 |
/*!
|
|
592 |
\macro Q_ATOMIC_INT_FETCH_AND_ADD_IS_ALWAYS_NATIVE
|
|
593 |
\relates QAtomicInt
|
|
594 |
|
|
595 |
This macro is defined if and only if your processor supports
|
|
596 |
atomic fetch-and-add on integers.
|
|
597 |
*/
|
|
598 |
|
|
599 |
/*!
|
|
600 |
\macro Q_ATOMIC_INT_FETCH_AND_ADD_IS_SOMETIMES_NATIVE
|
|
601 |
\relates QAtomicInt
|
|
602 |
|
|
603 |
This macro is defined when only certain generations of the
|
|
604 |
processor support atomic fetch-and-add on integers. Use the
|
|
605 |
QAtomicInt::isFetchAndAddNative() function to check what your
|
|
606 |
processor supports.
|
|
607 |
*/
|
|
608 |
|
|
609 |
/*!
|
|
610 |
\macro Q_ATOMIC_INT_FETCH_AND_ADD_IS_NOT_NATIVE
|
|
611 |
\relates QAtomicInt
|
|
612 |
|
|
613 |
This macro is defined when the hardware does not support atomic
|
|
614 |
fetch-and-add on integers.
|
|
615 |
*/
|
|
616 |
|
|
617 |
/*!
|
|
618 |
\macro Q_ATOMIC_INT_FETCH_AND_ADD_IS_WAIT_FREE
|
|
619 |
\relates QAtomicInt
|
|
620 |
|
|
621 |
This macro is defined together with
|
|
622 |
Q_ATOMIC_INT_FETCH_AND_ADD_IS_ALWAYS_NATIVE to indicate that the
|
|
623 |
atomic fetch-and-add on integers is wait-free.
|
|
624 |
*/
|
|
625 |
|
|
626 |
|
|
627 |
|
|
628 |
|
|
629 |
/*!
|
|
630 |
\class QAtomicPointer
|
|
631 |
\brief The QAtomicPointer class is a template class that provides platform-independent atomic operations on pointers.
|
|
632 |
\since 4.4
|
|
633 |
|
|
634 |
\ingroup thread
|
|
635 |
|
|
636 |
For atomic operations on integers, see the QAtomicInt class.
|
|
637 |
|
|
638 |
An complex operation that completes without interruption is said
|
|
639 |
to be \e atomic. The QAtomicPointer class provides atomic
|
|
640 |
test-and-set, fetch-and-store, and fetch-and-add for pointers.
|
|
641 |
|
|
642 |
\section1 Non-atomic convenience operators
|
|
643 |
|
|
644 |
For convenience, QAtomicPointer provides pointer comparison, cast,
|
|
645 |
dereference, and assignment operators. Note that these operators
|
|
646 |
are \e not atomic.
|
|
647 |
|
|
648 |
\section1 The Atomic API
|
|
649 |
|
|
650 |
\section2 Memory ordering
|
|
651 |
|
|
652 |
QAtomicPointer provides several implementations of the atomic
|
|
653 |
test-and-set, fetch-and-store, and fetch-and-add functions. Each
|
|
654 |
implementation defines a memory ordering semantic that describes
|
|
655 |
how memory accesses surrounding the atomic instruction are
|
|
656 |
executed by the processor. Since many modern architectures allow
|
|
657 |
out-of-order execution and memory ordering, using the correct
|
|
658 |
semantic is necessary to ensure that your application functions
|
|
659 |
properly on all processors.
|
|
660 |
|
|
661 |
\list
|
|
662 |
|
|
663 |
\o Relaxed - memory ordering is unspecified, leaving the compiler
|
|
664 |
and processor to freely reorder memory accesses.
|
|
665 |
|
|
666 |
\o Acquire - memory access following the atomic operation (in
|
|
667 |
program order) may not be re-ordered before the atomic operation.
|
|
668 |
|
|
669 |
\o Release - memory access before the atomic operation (in program
|
|
670 |
order) may not be re-ordered after the atomic operation.
|
|
671 |
|
|
672 |
\o Ordered - the same Acquire and Release semantics combined.
|
|
673 |
|
|
674 |
\endlist
|
|
675 |
|
|
676 |
\section2 Test-and-set
|
|
677 |
|
|
678 |
If the current value of the QAtomicPointer is an expected value,
|
|
679 |
the test-and-set functions assign a new value to the
|
|
680 |
QAtomicPointer and return true. If values are \a not the same,
|
|
681 |
these functions do nothing and return false. This operation
|
|
682 |
equates to the following code:
|
|
683 |
|
|
684 |
\snippet doc/src/snippets/code/src_corelib_thread_qatomic.cpp 4
|
|
685 |
|
|
686 |
There are 4 test-and-set functions: testAndSetRelaxed(),
|
|
687 |
testAndSetAcquire(), testAndSetRelease(), and
|
|
688 |
testAndSetOrdered(). See above for an explanation of the different
|
|
689 |
memory ordering semantics.
|
|
690 |
|
|
691 |
\section2 Fetch-and-store
|
|
692 |
|
|
693 |
The atomic fetch-and-store functions read the current value of the
|
|
694 |
QAtomicPointer and then assign a new value, returning the original
|
|
695 |
value. This operation equates to the following code:
|
|
696 |
|
|
697 |
\snippet doc/src/snippets/code/src_corelib_thread_qatomic.cpp 5
|
|
698 |
|
|
699 |
There are 4 fetch-and-store functions: fetchAndStoreRelaxed(),
|
|
700 |
fetchAndStoreAcquire(), fetchAndStoreRelease(), and
|
|
701 |
fetchAndStoreOrdered(). See above for an explanation of the
|
|
702 |
different memory ordering semantics.
|
|
703 |
|
|
704 |
\section2 Fetch-and-add
|
|
705 |
|
|
706 |
The atomic fetch-and-add functions read the current value of the
|
|
707 |
QAtomicPointer and then add the given value to the current value,
|
|
708 |
returning the original value. This operation equates to the
|
|
709 |
following code:
|
|
710 |
|
|
711 |
\snippet doc/src/snippets/code/src_corelib_thread_qatomic.cpp 6
|
|
712 |
|
|
713 |
There are 4 fetch-and-add functions: fetchAndAddRelaxed(),
|
|
714 |
fetchAndAddAcquire(), fetchAndAddRelease(), and
|
|
715 |
fetchAndAddOrdered(). See above for an explanation of the
|
|
716 |
different memory ordering semantics.
|
|
717 |
|
|
718 |
\section1 Feature Tests for the Atomic API
|
|
719 |
|
|
720 |
Providing a platform-independent atomic API that works on all
|
|
721 |
processors is challenging. The API provided by QAtomicPointer is
|
|
722 |
guaranteed to work atomically on all processors. However, since
|
|
723 |
not all processors implement support for every operation provided
|
|
724 |
by QAtomicPointer, it is necessary to expose information about the
|
|
725 |
processor.
|
|
726 |
|
|
727 |
You can check at compile time which features are supported on your
|
|
728 |
hardware using various macros. These will tell you if your
|
|
729 |
hardware always, sometimes, or does not support a particular
|
|
730 |
operation. The macros have the form
|
|
731 |
Q_ATOMIC_POINTER_\e{OPERATION}_IS_\e{HOW}_NATIVE. \e{OPERATION} is
|
|
732 |
one of TEST_AND_SET, FETCH_AND_STORE, or FETCH_AND_ADD, and
|
|
733 |
\e{HOW} is one of ALWAYS, SOMETIMES, or NOT. There will always be
|
|
734 |
exactly one defined macro per operation. For example, if
|
|
735 |
Q_ATOMIC_POINTER_TEST_AND_SET_IS_ALWAYS_NATIVE is defined, neither
|
|
736 |
Q_ATOMIC_POINTER_TEST_AND_SET_IS_SOMETIMES_NATIVE nor
|
|
737 |
Q_ATOMIC_POINTER_TEST_AND_SET_IS_NOT_NATIVE will be defined.
|
|
738 |
|
|
739 |
An operation that completes in constant time is said to be
|
|
740 |
wait-free. Such operations are not implemented using locks or
|
|
741 |
loops of any kind. For atomic operations that are always
|
|
742 |
supported, and that are wait-free, Qt defines the
|
|
743 |
Q_ATOMIC_POINTER_\e{OPERATION}_IS_WAIT_FREE in addition to the
|
|
744 |
Q_ATOMIC_POINTER_\e{OPERATION}_IS_ALWAYS_NATIVE.
|
|
745 |
|
|
746 |
In cases where an atomic operation is only supported in newer
|
|
747 |
generations of the processor, QAtomicPointer also provides a way
|
|
748 |
to check at runtime what your hardware supports with the
|
|
749 |
isTestAndSetNative(), isFetchAndStoreNative(), and
|
|
750 |
isFetchAndAddNative() functions. Wait-free implementations can be
|
|
751 |
detected using the isTestAndSetWaitFree(),
|
|
752 |
isFetchAndStoreWaitFree(), and isFetchAndAddWaitFree() functions.
|
|
753 |
|
|
754 |
Below is a complete list of all feature macros for QAtomicPointer:
|
|
755 |
|
|
756 |
\list
|
|
757 |
|
|
758 |
\o Q_ATOMIC_POINTER_TEST_AND_SET_IS_ALWAYS_NATIVE
|
|
759 |
\o Q_ATOMIC_POINTER_TEST_AND_SET_IS_SOMETIMES_NATIVE
|
|
760 |
\o Q_ATOMIC_POINTER_TEST_AND_SET_IS_NOT_NATIVE
|
|
761 |
\o Q_ATOMIC_POINTER_TEST_AND_SET_IS_WAIT_FREE
|
|
762 |
|
|
763 |
\o Q_ATOMIC_POINTER_FETCH_AND_STORE_IS_ALWAYS_NATIVE
|
|
764 |
\o Q_ATOMIC_POINTER_FETCH_AND_STORE_IS_SOMETIMES_NATIVE
|
|
765 |
\o Q_ATOMIC_POINTER_FETCH_AND_STORE_IS_NOT_NATIVE
|
|
766 |
\o Q_ATOMIC_POINTER_FETCH_AND_STORE_IS_WAIT_FREE
|
|
767 |
|
|
768 |
\o Q_ATOMIC_POINTER_FETCH_AND_ADD_IS_ALWAYS_NATIVE
|
|
769 |
\o Q_ATOMIC_POINTER_FETCH_AND_ADD_IS_SOMETIMES_NATIVE
|
|
770 |
\o Q_ATOMIC_POINTER_FETCH_AND_ADD_IS_NOT_NATIVE
|
|
771 |
\o Q_ATOMIC_POINTER_FETCH_AND_ADD_IS_WAIT_FREE
|
|
772 |
|
|
773 |
\endlist
|
|
774 |
|
|
775 |
\sa QAtomicInt
|
|
776 |
*/
|
|
777 |
|
|
778 |
/*! \fn QAtomicPointer::QAtomicPointer(T *value)
|
|
779 |
|
|
780 |
Constructs a QAtomicPointer with the given \a value.
|
|
781 |
*/
|
|
782 |
|
|
783 |
/*! \fn QAtomicPointer::QAtomicPointer(const QAtomicPointer<T> &other)
|
|
784 |
|
|
785 |
Constructs a copy of \a other.
|
|
786 |
*/
|
|
787 |
|
|
788 |
/*! \fn QAtomicPointer<T> &QAtomicPointer::operator=(T *value)
|
|
789 |
|
|
790 |
Assigns the \a value to this QAtomicPointer and returns a
|
|
791 |
reference to this QAtomicPointer.
|
|
792 |
*/
|
|
793 |
|
|
794 |
/*! \fn QAtomicPointer<T> &QAtomicPointer::operator=(const QAtomicPointer<T> &other)
|
|
795 |
|
|
796 |
Assigns \a other to this QAtomicPointer and returns a reference to
|
|
797 |
this QAtomicPointer.
|
|
798 |
*/
|
|
799 |
|
|
800 |
/*! \fn bool QAtomicPointer::operator==(T *value) const
|
|
801 |
|
|
802 |
Returns true if the \a value is equal to the value in this
|
|
803 |
QAtomicPointer; otherwise returns false.
|
|
804 |
*/
|
|
805 |
|
|
806 |
/*! \fn bool QAtomicPointer::operator!=(T *value) const
|
|
807 |
|
|
808 |
Returns true if the value of this QAtomicPointer is not equal to
|
|
809 |
\a value; otherwise returns false.
|
|
810 |
*/
|
|
811 |
|
|
812 |
/*! \fn bool QAtomicPointer::operator!() const
|
|
813 |
|
|
814 |
Returns true is the current value of this QAtomicPointer is zero;
|
|
815 |
otherwise returns false.
|
|
816 |
*/
|
|
817 |
|
|
818 |
/*! \fn QAtomicPointer::operator T *() const
|
|
819 |
|
|
820 |
Returns the current pointer value stored by this QAtomicPointer
|
|
821 |
object.
|
|
822 |
*/
|
|
823 |
|
|
824 |
/*! \fn T *QAtomicPointer::operator->() const
|
|
825 |
|
|
826 |
*/
|
|
827 |
|
|
828 |
/*! \fn bool QAtomicPointer::isTestAndSetNative()
|
|
829 |
|
|
830 |
Returns true if test-and-set is implemented using atomic processor
|
|
831 |
instructions, false otherwise.
|
|
832 |
*/
|
|
833 |
|
|
834 |
/*! \fn bool QAtomicPointer::isTestAndSetWaitFree()
|
|
835 |
|
|
836 |
Returns true if atomic test-and-set is wait-free, false otherwise.
|
|
837 |
*/
|
|
838 |
|
|
839 |
/*! \fn bool QAtomicPointer::testAndSetRelaxed(T *expectedValue, T *newValue)
|
|
840 |
|
|
841 |
Atomic test-and-set.
|
|
842 |
|
|
843 |
If the current value of this QAtomicPointer is the \a expectedValue,
|
|
844 |
the test-and-set functions assign the \a newValue to this
|
|
845 |
QAtomicPointer and return true. If the values are \e not the same,
|
|
846 |
this function does nothing and returns false.
|
|
847 |
|
|
848 |
This function uses \e relaxed \l {QAtomicPointer#Memory
|
|
849 |
ordering}{memory ordering} semantics, leaving the compiler and
|
|
850 |
processor to freely reorder memory accesses.
|
|
851 |
*/
|
|
852 |
|
|
853 |
/*! \fn bool QAtomicPointer::testAndSetAcquire(T *expectedValue, T *newValue)
|
|
854 |
|
|
855 |
Atomic test-and-set.
|
|
856 |
|
|
857 |
If the current value of this QAtomicPointer is the \a expectedValue,
|
|
858 |
the test-and-set functions assign the \a newValue to this
|
|
859 |
QAtomicPointer and return true. If the values are \e not the same,
|
|
860 |
this function does nothing and returns false.
|
|
861 |
|
|
862 |
This function uses \e acquire \l {QAtomicPointer#Memory
|
|
863 |
ordering}{memory ordering} semantics, which ensures that memory
|
|
864 |
access following the atomic operation (in program order) may not
|
|
865 |
be re-ordered before the atomic operation.
|
|
866 |
*/
|
|
867 |
|
|
868 |
/*! \fn bool QAtomicPointer::testAndSetRelease(T *expectedValue, T *newValue)
|
|
869 |
|
|
870 |
Atomic test-and-set.
|
|
871 |
|
|
872 |
If the current value of this QAtomicPointer is the \a expectedValue,
|
|
873 |
the test-and-set functions assign the \a newValue to this
|
|
874 |
QAtomicPointer and return true. If the values are \e not the same,
|
|
875 |
this function does nothing and returns false.
|
|
876 |
|
|
877 |
This function uses \e release \l {QAtomicPointer#Memory
|
|
878 |
ordering}{memory ordering} semantics, which ensures that memory
|
|
879 |
access before the atomic operation (in program order) may not be
|
|
880 |
re-ordered after the atomic operation.
|
|
881 |
*/
|
|
882 |
|
|
883 |
/*! \fn bool QAtomicPointer::testAndSetOrdered(T *expectedValue, T *newValue)
|
|
884 |
|
|
885 |
Atomic test-and-set.
|
|
886 |
|
|
887 |
If the current value of this QAtomicPointer is the \a expectedValue,
|
|
888 |
the test-and-set functions assign the \a newValue to this
|
|
889 |
QAtomicPointer and return true. If the values are \e not the same,
|
|
890 |
this function does nothing and returns false.
|
|
891 |
|
|
892 |
This function uses \e ordered \l {QAtomicPointer#Memory
|
|
893 |
ordering}{memory ordering} semantics, which ensures that memory
|
|
894 |
access before and after the atomic operation (in program order)
|
|
895 |
may not be re-ordered.
|
|
896 |
*/
|
|
897 |
|
|
898 |
/*! \fn bool QAtomicPointer::isFetchAndStoreNative()
|
|
899 |
|
|
900 |
Returns true if fetch-and-store is implemented using atomic
|
|
901 |
processor instructions, false otherwise.
|
|
902 |
*/
|
|
903 |
|
|
904 |
/*! \fn bool QAtomicPointer::isFetchAndStoreWaitFree()
|
|
905 |
|
|
906 |
Returns true if atomic fetch-and-store is wait-free, false
|
|
907 |
otherwise.
|
|
908 |
*/
|
|
909 |
|
|
910 |
/*! \fn T *QAtomicPointer::fetchAndStoreRelaxed(T *newValue)
|
|
911 |
|
|
912 |
Atomic fetch-and-store.
|
|
913 |
|
|
914 |
Reads the current value of this QAtomicPointer and then assigns it the
|
|
915 |
\a newValue, returning the original value.
|
|
916 |
|
|
917 |
This function uses \e relaxed \l {QAtomicPointer#Memory
|
|
918 |
ordering}{memory ordering} semantics, leaving the compiler and
|
|
919 |
processor to freely reorder memory accesses.
|
|
920 |
*/
|
|
921 |
|
|
922 |
/*! \fn T *QAtomicPointer::fetchAndStoreAcquire(T *newValue)
|
|
923 |
|
|
924 |
Atomic fetch-and-store.
|
|
925 |
|
|
926 |
Reads the current value of this QAtomicPointer and then assigns it the
|
|
927 |
\a newValue, returning the original value.
|
|
928 |
|
|
929 |
This function uses \e acquire \l {QAtomicPointer#Memory
|
|
930 |
ordering}{memory ordering} semantics, which ensures that memory
|
|
931 |
access following the atomic operation (in program order) may not
|
|
932 |
be re-ordered before the atomic operation.
|
|
933 |
*/
|
|
934 |
|
|
935 |
/*! \fn T *QAtomicPointer::fetchAndStoreRelease(T *newValue)
|
|
936 |
|
|
937 |
Atomic fetch-and-store.
|
|
938 |
|
|
939 |
Reads the current value of this QAtomicPointer and then assigns it the
|
|
940 |
\a newValue, returning the original value.
|
|
941 |
|
|
942 |
This function uses \e release \l {QAtomicPointer#Memory
|
|
943 |
ordering}{memory ordering} semantics, which ensures that memory
|
|
944 |
access before the atomic operation (in program order) may not be
|
|
945 |
re-ordered after the atomic operation.
|
|
946 |
*/
|
|
947 |
|
|
948 |
/*! \fn T *QAtomicPointer::fetchAndStoreOrdered(T *newValue)
|
|
949 |
|
|
950 |
Atomic fetch-and-store.
|
|
951 |
|
|
952 |
Reads the current value of this QAtomicPointer and then assigns it the
|
|
953 |
\a newValue, returning the original value.
|
|
954 |
|
|
955 |
This function uses \e ordered \l {QAtomicPointer#Memory
|
|
956 |
ordering}{memory ordering} semantics, which ensures that memory
|
|
957 |
access before and after the atomic operation (in program order)
|
|
958 |
may not be re-ordered.
|
|
959 |
*/
|
|
960 |
|
|
961 |
/*! \fn bool QAtomicPointer::isFetchAndAddNative()
|
|
962 |
|
|
963 |
Returns true if fetch-and-add is implemented using atomic
|
|
964 |
processor instructions, false otherwise.
|
|
965 |
*/
|
|
966 |
|
|
967 |
/*! \fn bool QAtomicPointer::isFetchAndAddWaitFree()
|
|
968 |
|
|
969 |
Returns true if atomic fetch-and-add is wait-free, false
|
|
970 |
otherwise.
|
|
971 |
*/
|
|
972 |
|
|
973 |
/*! \fn T *QAtomicPointer::fetchAndAddRelaxed(qptrdiff valueToAdd)
|
|
974 |
|
|
975 |
Atomic fetch-and-add.
|
|
976 |
|
|
977 |
Reads the current value of this QAtomicPointer and then adds
|
|
978 |
\a valueToAdd to the current value, returning the original value.
|
|
979 |
|
|
980 |
This function uses \e relaxed \l {QAtomicPointer#Memory
|
|
981 |
ordering}{memory ordering} semantics, leaving the compiler and
|
|
982 |
processor to freely reorder memory accesses.
|
|
983 |
*/
|
|
984 |
|
|
985 |
/*! \fn T *QAtomicPointer::fetchAndAddAcquire(qptrdiff valueToAdd)
|
|
986 |
|
|
987 |
Atomic fetch-and-add.
|
|
988 |
|
|
989 |
Reads the current value of this QAtomicPointer and then adds
|
|
990 |
\a valueToAdd to the current value, returning the original value.
|
|
991 |
|
|
992 |
This function uses \e acquire \l {QAtomicPointer#Memory
|
|
993 |
ordering}{memory ordering} semantics, which ensures that memory
|
|
994 |
access following the atomic operation (in program order) may not
|
|
995 |
be re-ordered before the atomic operation.
|
|
996 |
*/
|
|
997 |
|
|
998 |
/*! \fn T *QAtomicPointer::fetchAndAddRelease(qptrdiff valueToAdd)
|
|
999 |
|
|
1000 |
Atomic fetch-and-add.
|
|
1001 |
|
|
1002 |
Reads the current value of this QAtomicPointer and then adds
|
|
1003 |
\a valueToAdd to the current value, returning the original value.
|
|
1004 |
|
|
1005 |
This function uses \e release \l {QAtomicPointer#Memory
|
|
1006 |
ordering}{memory ordering} semantics, which ensures that memory
|
|
1007 |
access before the atomic operation (in program order) may not be
|
|
1008 |
re-ordered after the atomic operation.
|
|
1009 |
*/
|
|
1010 |
|
|
1011 |
/*! \fn T *QAtomicPointer::fetchAndAddOrdered(qptrdiff valueToAdd)
|
|
1012 |
|
|
1013 |
Atomic fetch-and-add.
|
|
1014 |
|
|
1015 |
Reads the current value of this QAtomicPointer and then adds
|
|
1016 |
\a valueToAdd to the current value, returning the original value.
|
|
1017 |
|
|
1018 |
This function uses \e ordered \l {QAtomicPointer#Memory
|
|
1019 |
ordering}{memory ordering} semantics, which ensures that memory
|
|
1020 |
access before and after the atomic operation (in program order)
|
|
1021 |
may not be re-ordered.
|
|
1022 |
*/
|
|
1023 |
|
|
1024 |
/*!
|
|
1025 |
\macro Q_ATOMIC_POINTER_TEST_AND_SET_IS_ALWAYS_NATIVE
|
|
1026 |
\relates QAtomicPointer
|
|
1027 |
|
|
1028 |
This macro is defined if and only if your processor supports
|
|
1029 |
atomic test-and-set on pointers.
|
|
1030 |
*/
|
|
1031 |
|
|
1032 |
/*!
|
|
1033 |
\macro Q_ATOMIC_POINTER_TEST_AND_SET_IS_SOMETIMES_NATIVE
|
|
1034 |
\relates QAtomicPointer
|
|
1035 |
|
|
1036 |
This macro is defined when only certain generations of the
|
|
1037 |
processor support atomic test-and-set on pointers. Use the
|
|
1038 |
QAtomicPointer::isTestAndSetNative() function to check what your
|
|
1039 |
processor supports.
|
|
1040 |
*/
|
|
1041 |
|
|
1042 |
/*!
|
|
1043 |
\macro Q_ATOMIC_POINTER_TEST_AND_SET_IS_NOT_NATIVE
|
|
1044 |
\relates QAtomicPointer
|
|
1045 |
|
|
1046 |
This macro is defined when the hardware does not support atomic
|
|
1047 |
test-and-set on pointers.
|
|
1048 |
*/
|
|
1049 |
|
|
1050 |
/*!
|
|
1051 |
\macro Q_ATOMIC_POINTER_TEST_AND_SET_IS_WAIT_FREE
|
|
1052 |
\relates QAtomicPointer
|
|
1053 |
|
|
1054 |
This macro is defined together with
|
|
1055 |
Q_ATOMIC_POINTER_TEST_AND_SET_IS_ALWAYS_NATIVE to indicate that
|
|
1056 |
the atomic test-and-set on pointers is wait-free.
|
|
1057 |
*/
|
|
1058 |
|
|
1059 |
/*!
|
|
1060 |
\macro Q_ATOMIC_POINTER_FETCH_AND_STORE_IS_ALWAYS_NATIVE
|
|
1061 |
\relates QAtomicPointer
|
|
1062 |
|
|
1063 |
This macro is defined if and only if your processor supports
|
|
1064 |
atomic fetch-and-store on pointers.
|
|
1065 |
*/
|
|
1066 |
|
|
1067 |
/*!
|
|
1068 |
\macro Q_ATOMIC_POINTER_FETCH_AND_STORE_IS_SOMETIMES_NATIVE
|
|
1069 |
\relates QAtomicPointer
|
|
1070 |
|
|
1071 |
This macro is defined when only certain generations of the
|
|
1072 |
processor support atomic fetch-and-store on pointers. Use the
|
|
1073 |
QAtomicPointer::isFetchAndStoreNative() function to check what
|
|
1074 |
your processor supports.
|
|
1075 |
*/
|
|
1076 |
|
|
1077 |
/*!
|
|
1078 |
\macro Q_ATOMIC_POINTER_FETCH_AND_STORE_IS_NOT_NATIVE
|
|
1079 |
\relates QAtomicPointer
|
|
1080 |
|
|
1081 |
This macro is defined when the hardware does not support atomic
|
|
1082 |
fetch-and-store on pointers.
|
|
1083 |
*/
|
|
1084 |
|
|
1085 |
/*!
|
|
1086 |
\macro Q_ATOMIC_POINTER_FETCH_AND_STORE_IS_WAIT_FREE
|
|
1087 |
\relates QAtomicPointer
|
|
1088 |
|
|
1089 |
This macro is defined together with
|
|
1090 |
Q_ATOMIC_POINTER_FETCH_AND_STORE_IS_ALWAYS_NATIVE to indicate that
|
|
1091 |
the atomic fetch-and-store on pointers is wait-free.
|
|
1092 |
*/
|
|
1093 |
|
|
1094 |
/*!
|
|
1095 |
\macro Q_ATOMIC_POINTER_FETCH_AND_ADD_IS_ALWAYS_NATIVE
|
|
1096 |
\relates QAtomicPointer
|
|
1097 |
|
|
1098 |
This macro is defined if and only if your processor supports
|
|
1099 |
atomic fetch-and-add on pointers.
|
|
1100 |
*/
|
|
1101 |
|
|
1102 |
/*!
|
|
1103 |
\macro Q_ATOMIC_POINTER_FETCH_AND_ADD_IS_SOMETIMES_NATIVE
|
|
1104 |
\relates QAtomicPointer
|
|
1105 |
|
|
1106 |
This macro is defined when only certain generations of the
|
|
1107 |
processor support atomic fetch-and-add on pointers. Use the
|
|
1108 |
QAtomicPointer::isFetchAndAddNative() function to check what your
|
|
1109 |
processor supports.
|
|
1110 |
*/
|
|
1111 |
|
|
1112 |
/*!
|
|
1113 |
\macro Q_ATOMIC_POINTER_FETCH_AND_ADD_IS_NOT_NATIVE
|
|
1114 |
\relates QAtomicPointer
|
|
1115 |
|
|
1116 |
This macro is defined when the hardware does not support atomic
|
|
1117 |
fetch-and-add on pointers.
|
|
1118 |
*/
|
|
1119 |
|
|
1120 |
/*!
|
|
1121 |
\macro Q_ATOMIC_POINTER_FETCH_AND_ADD_IS_WAIT_FREE
|
|
1122 |
\relates QAtomicPointer
|
|
1123 |
|
|
1124 |
This macro is defined together with
|
|
1125 |
Q_ATOMIC_POINTER_FETCH_AND_ADD_IS_ALWAYS_NATIVE to indicate that
|
|
1126 |
the atomic fetch-and-add on pointers is wait-free.
|
|
1127 |
*/
|