Temporarily add a private QESDPv2

To unlock work while waiting for QISP. QESDP is lacking
a few crucial APIs (isDetached() / isShared() / reset(ptr) / deep
const), so we can't go there right away.

Change-Id: I647eb0db4ea800488a323f3b64661e848998168d
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

3 files changed, 169 insertions, 0 deletions

diff --git a/src/corelib/CMakeLists.txt b/src/corelib/CMakeLists.txt
index 4685028174..5d79b00bf9 100644
--- a/src/corelib/CMakeLists.txt
+++ b/src/corelib/CMakeLists.txt
@@ -228,6 +228,7 @@ qt_add_module(Core
         tools/qscopeguard.h
         tools/qset.h
         tools/qshareddata.cpp tools/qshareddata.h
+        tools/qshareddata_impl.h
         tools/qsharedpointer.cpp tools/qsharedpointer.h
         tools/qsharedpointer_impl.h
         tools/qsize.cpp tools/qsize.h
diff --git a/src/corelib/tools/qshareddata_impl.h b/src/corelib/tools/qshareddata_impl.h
new file mode 100644
index 0000000000..930c35879f
--- /dev/null
+++ b/src/corelib/tools/qshareddata_impl.h
@@ -0,0 +1,167 @@
+/****************************************************************************
+**
+** Copyright (C) 2020 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
+** Contact: https://www.qt.io/licensing/
+**
+** 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 The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/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 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#if 0
+#pragma qt_sync_skip_header_check
+#pragma qt_sync_stop_processing
+#endif
+
+#ifndef QSHAREDDATA_IMPL_H
+#define QSHAREDDATA_IMPL_H
+
+#include <QtCore/qglobal.h>
+
+QT_BEGIN_NAMESPACE
+
+namespace QtPrivate {
+
+template <typename T>
+class QExplicitlySharedDataPointerV2
+{
+    T *d;
+
+public:
+    constexpr QExplicitlySharedDataPointerV2() noexcept : d(nullptr) {}
+
+    explicit QExplicitlySharedDataPointerV2(T *d) noexcept
+        : d(d)
+    {
+        if (d)
+            d->ref.ref();
+    }
+
+    QExplicitlySharedDataPointerV2(const QExplicitlySharedDataPointerV2 &other) noexcept
+        : d(other.d)
+    {
+        if (d)
+            d->ref.ref();
+    }
+
+    QExplicitlySharedDataPointerV2 &operator=(const QExplicitlySharedDataPointerV2 &other) noexcept
+    {
+        QExplicitlySharedDataPointerV2 copy(other);
+        swap(copy);
+        return *this;
+    }
+
+    QExplicitlySharedDataPointerV2(QExplicitlySharedDataPointerV2 &&other) noexcept
+        : d(qExchange(other.d, nullptr))
+    {
+    }
+
+    QExplicitlySharedDataPointerV2 &operator=(QExplicitlySharedDataPointerV2 &&other) noexcept
+    {
+        QExplicitlySharedDataPointerV2 moved(std::move(other));
+        swap(moved);
+        return *this;
+    }
+
+    ~QExplicitlySharedDataPointerV2()
+    {
+        if (d && !d->ref.deref())
+            delete d;
+    }
+
+    void detach()
+    {
+        if (!d) {
+            // should this codepath be here on in all user's detach()?
+            d = new T;
+            d->ref.ref();
+        } else if (d->ref.loadRelaxed() != 1) {
+            // TODO: qAtomicDetach here...?
+            QExplicitlySharedDataPointerV2 copy(new T(*d));
+            swap(copy);
+        }
+    }
+
+    void reset(T *t = nullptr) noexcept
+    {
+        if (d && !d->ref.deref())
+            delete d;
+        d = t;
+        if (d)
+            d->ref.ref();
+    }
+
+    bool isShared() const noexcept
+    {
+        return d && d->ref.loadRelaxed() != 1;
+    }
+
+    constexpr void swap(QExplicitlySharedDataPointerV2 &other) noexcept
+    {
+        qSwap(d, other.d);
+    }
+
+    // important change from QExplicitlySharedDataPointer: deep const
+    constexpr T &operator*() { return *d; }
+    constexpr T *operator->() { return d; }
+    constexpr const T &operator*() const { return *d; }
+    constexpr const T *operator->() const { return d; }
+
+    constexpr T *data() noexcept { return d; }
+    constexpr const T *data() const noexcept { return d; }
+
+    constexpr explicit operator bool() const noexcept { return d; }
+
+    constexpr friend bool operator==(const QExplicitlySharedDataPointerV2 &lhs,
+                                     const QExplicitlySharedDataPointerV2 &rhs) noexcept
+    {
+        return lhs.d == rhs.d;
+    }
+
+    constexpr friend bool operator!=(const QExplicitlySharedDataPointerV2 &lhs,
+                                     const QExplicitlySharedDataPointerV2 &rhs) noexcept
+    {
+        return lhs.d != rhs.d;
+    }
+};
+
+template <typename T>
+constexpr void swap(QExplicitlySharedDataPointerV2<T> &lhs, QExplicitlySharedDataPointerV2<T> &rhs) noexcept
+{
+    lhs.swap(rhs);
+}
+
+} // namespace QtPrivate
+
+QT_END_NAMESPACE
+
+#endif // QSHAREDDATA_IMPL_H
diff --git a/src/corelib/tools/tools.pri b/src/corelib/tools/tools.pri
index 607a6eaf06..4d3b5e25ff 100644
--- a/src/corelib/tools/tools.pri
+++ b/src/corelib/tools/tools.pri
@@ -37,6 +37,7 @@ HEADERS +=  \
         tools/qscopedpointer_p.h \
         tools/qscopedvaluerollback.h \
         tools/qshareddata.h \
+        tools/qshareddata_impl.h \
         tools/qsharedpointer.h \
         tools/qsharedpointer_impl.h \
         tools/qset.h \