qforeach.h

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// Copyright (C) 2022 The Qt Company Ltd.
// Copyright (C) 2019 Intel Corporation.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
 
#ifndef QFOREACH_H
#define QFOREACH_H
 
#include <QtCore/qtclasshelpermacros.h>
#include <QtCore/qtconfigmacros.h>
#include <QtCore/qtdeprecationmarkers.h>
#include <QtCore/qttypetraits.h>
 
QT_BEGIN_NAMESPACE
 
#if 0
#pragma qt_class(QForeach)
#pragma qt_sync_stop_processing
#endif
 
#ifndef QT_NO_FOREACH
 
namespace QtPrivate {
 
template <typename T>
class QForeachContainer {
    Q_DISABLE_COPY_MOVE(QForeachContainer)
public:
    QForeachContainer(const T &t) : c(t), i(std::as_const(c).begin()), e(std::as_const(c).end()) {}
    QForeachContainer(T &&t) : c(std::move(t)), i(std::as_const(c).begin()), e(std::as_const(c).end())  {}
 
    T c;
    typename T::const_iterator i, e;
};
 
// Containers that have a detach function are considered shared, and are OK in a foreach loop
template <typename T, typename = decltype(std::declval<T>().detach())>
inline void warnIfContainerIsNotShared(int) {}
 
#if QT_DEPRECATED_SINCE(6, 0)
// Other containers will copy themselves if used in foreach, this use is deprecated
template <typename T>
QT_DEPRECATED_VERSION_X_6_0("Do not use foreach/Q_FOREACH with containers which are not implicitly shared. "
    "Prefer using a range-based for loop with these containers: `for (const auto &it : container)`, "
    "keeping in mind that range-based for doesn't copy the container as Q_FOREACH does")
inline void warnIfContainerIsNotShared(...) {}
#endif
 
template<typename T>
QForeachContainer<typename std::decay<T>::type> qMakeForeachContainer(T &&t)
{
    warnIfContainerIsNotShared<typename std::decay<T>::type>(0);
    return QForeachContainer<typename std::decay<T>::type>(std::forward<T>(t));
}
 
}
 
// Use C++17 if statement with initializer. User's code ends up in a else so
// scoping of different ifs is not broken
#define Q_FOREACH_IMPL(variable, name, container)
    for (auto name = QtPrivate::qMakeForeachContainer(container); name.i != name.e; ++name.i)
        if (variable = *name.i; false) {} else
 
#define Q_FOREACH_JOIN(A, B) Q_FOREACH_JOIN_IMPL(A, B)
#define Q_FOREACH_JOIN_IMPL(A, B) A ## B
 
#define Q_FOREACH(variable, container)
    Q_FOREACH_IMPL(variable, Q_FOREACH_JOIN(_container_, __LINE__), container)
#endif // QT_NO_FOREACH
 
#define Q_FOREVER for(;;)
#ifndef QT_NO_KEYWORDS
# ifndef QT_NO_FOREACH
#  ifndef foreach
#    define foreach Q_FOREACH
#  endif
# endif // QT_NO_FOREACH
#  ifndef forever
#    define forever Q_FOREVER
#  endif
#endif
 
QT_END_NAMESPACE
 
#endif /* QFOREACH_H */