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/****************************************************************************
**
** Copyright (C) 2016 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the QtQml 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.
**
** $QT_END_LICENSE$
**
****************************************************************************/
#include "qv4memberdata_p.h"
#include <private/qv4mm_p.h>
#include "qv4value_p.h"
using namespace QV4;
DEFINE_MANAGED_VTABLE(MemberData);
static size_t nextPowerOfTwo(size_t s)
{
--s;
s |= s >> 1;
s |= s >> 2;
s |= s >> 4;
s |= s >> 8;
s |= s >> 16;
#if (QT_POINTER_SIZE == 8)
s |= s >> 32;
#endif
++s;
return s;
}
Heap::MemberData *MemberData::allocate(ExecutionEngine *e, uint n, Heap::MemberData *old)
{
Q_ASSERT(!old || old->values.size <= n);
if (!n)
n = 4;
size_t alloc = MemoryManager::align(sizeof(Heap::MemberData) + (n - 1)*sizeof(Value));
// round up to next power of two to avoid quadratic behaviour for very large objects
alloc = nextPowerOfTwo(alloc);
// The above code can overflow in a number of interesting ways. All of those are unsigned,
// and therefore defined behavior. Still, apply some sane bounds.
if (alloc > std::numeric_limits<int>::max())
alloc = std::numeric_limits<int>::max();
Heap::MemberData *m;
if (old) {
const size_t oldSize = sizeof(Heap::MemberData) + (old->values.size - 1) * sizeof(Value);
if (oldSize > alloc)
alloc = oldSize;
m = e->memoryManager->allocManaged<MemberData>(alloc);
// no write barrier required here
memcpy(m, old, oldSize);
} else {
m = e->memoryManager->allocManaged<MemberData>(alloc);
m->init();
}
m->values.alloc = static_cast<uint>((alloc - sizeof(Heap::MemberData) + sizeof(Value))/sizeof(Value));
m->values.size = m->values.alloc;
return m;
}
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