1 | /**************************************************************************** |
2 | ** |
3 | ** Copyright (C) 2016 The Qt Company Ltd. |
4 | ** Contact: https://www.qt.io/licensing/ |
5 | ** |
6 | ** This file is part of the QtQml module of the Qt Toolkit. |
7 | ** |
8 | ** $QT_BEGIN_LICENSE:LGPL$ |
9 | ** Commercial License Usage |
10 | ** Licensees holding valid commercial Qt licenses may use this file in |
11 | ** accordance with the commercial license agreement provided with the |
12 | ** Software or, alternatively, in accordance with the terms contained in |
13 | ** a written agreement between you and The Qt Company. For licensing terms |
14 | ** and conditions see https://www.qt.io/terms-conditions. For further |
15 | ** information use the contact form at https://www.qt.io/contact-us. |
16 | ** |
17 | ** GNU Lesser General Public License Usage |
18 | ** Alternatively, this file may be used under the terms of the GNU Lesser |
19 | ** General Public License version 3 as published by the Free Software |
20 | ** Foundation and appearing in the file LICENSE.LGPL3 included in the |
21 | ** packaging of this file. Please review the following information to |
22 | ** ensure the GNU Lesser General Public License version 3 requirements |
23 | ** will be met: https://www.gnu.org/licenses/lgpl-3.0.html. |
24 | ** |
25 | ** GNU General Public License Usage |
26 | ** Alternatively, this file may be used under the terms of the GNU |
27 | ** General Public License version 2.0 or (at your option) the GNU General |
28 | ** Public license version 3 or any later version approved by the KDE Free |
29 | ** Qt Foundation. The licenses are as published by the Free Software |
30 | ** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3 |
31 | ** included in the packaging of this file. Please review the following |
32 | ** information to ensure the GNU General Public License requirements will |
33 | ** be met: https://www.gnu.org/licenses/gpl-2.0.html and |
34 | ** https://www.gnu.org/licenses/gpl-3.0.html. |
35 | ** |
36 | ** $QT_END_LICENSE$ |
37 | ** |
38 | ****************************************************************************/ |
39 | |
40 | #include "qv4memberdata_p.h" |
41 | #include <private/qv4mm_p.h> |
42 | #include "qv4value_p.h" |
43 | |
44 | using namespace QV4; |
45 | |
46 | DEFINE_MANAGED_VTABLE(MemberData); |
47 | |
48 | static size_t nextPowerOfTwo(size_t s) |
49 | { |
50 | --s; |
51 | s |= s >> 1; |
52 | s |= s >> 2; |
53 | s |= s >> 4; |
54 | s |= s >> 8; |
55 | s |= s >> 16; |
56 | #if (QT_POINTER_SIZE == 8) |
57 | s |= s >> 32; |
58 | #endif |
59 | ++s; |
60 | return s; |
61 | } |
62 | |
63 | Heap::MemberData *MemberData::allocate(ExecutionEngine *e, uint n, Heap::MemberData *old) |
64 | { |
65 | Q_ASSERT(!old || old->values.size <= n); |
66 | if (!n) |
67 | n = 4; |
68 | |
69 | size_t alloc = MemoryManager::align(size: sizeof(Heap::MemberData) + (n - 1)*sizeof(Value)); |
70 | // round up to next power of two to avoid quadratic behaviour for very large objects |
71 | alloc = nextPowerOfTwo(s: alloc); |
72 | |
73 | // The above code can overflow in a number of interesting ways. All of those are unsigned, |
74 | // and therefore defined behavior. Still, apply some sane bounds. |
75 | const size_t intMax = std::numeric_limits<int>::max(); |
76 | if (alloc > intMax) |
77 | alloc = intMax; |
78 | |
79 | Heap::MemberData *m; |
80 | if (old) { |
81 | const size_t oldSize = sizeof(Heap::MemberData) + (old->values.size - 1) * sizeof(Value); |
82 | if (oldSize > alloc) |
83 | alloc = oldSize; |
84 | m = e->memoryManager->allocManaged<MemberData>(size: alloc); |
85 | // no write barrier required here |
86 | memcpy(dest: m, src: old, n: oldSize); |
87 | } else { |
88 | m = e->memoryManager->allocManaged<MemberData>(size: alloc); |
89 | m->init(); |
90 | } |
91 | |
92 | m->values.alloc = static_cast<uint>((alloc - sizeof(Heap::MemberData) + sizeof(Value))/sizeof(Value)); |
93 | m->values.size = m->values.alloc; |
94 | return m; |
95 | } |
96 | |