1 | // Copyright (C) 2016 The Qt Company Ltd. |
---|---|
2 | // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only |
3 | |
4 | #include "qv4memberdata_p.h" |
5 | #include <private/qv4mm_p.h> |
6 | #include "qv4value_p.h" |
7 | |
8 | using namespace QV4; |
9 | |
10 | DEFINE_MANAGED_VTABLE(MemberData); |
11 | |
12 | static size_t nextPowerOfTwo(size_t s) |
13 | { |
14 | --s; |
15 | s |= s >> 1; |
16 | s |= s >> 2; |
17 | s |= s >> 4; |
18 | s |= s >> 8; |
19 | s |= s >> 16; |
20 | #if (QT_POINTER_SIZE == 8) |
21 | s |= s >> 32; |
22 | #endif |
23 | ++s; |
24 | return s; |
25 | } |
26 | |
27 | Heap::MemberData *MemberData::allocate(ExecutionEngine *e, uint n, Heap::MemberData *old) |
28 | { |
29 | Q_ASSERT(!old || old->values.size <= n); |
30 | if (!n) |
31 | n = 4; |
32 | |
33 | size_t alloc = MemoryManager::align(size: sizeof(Heap::MemberData) + (n - 1)*sizeof(Value)); |
34 | // round up to next power of two to avoid quadratic behaviour for very large objects |
35 | alloc = nextPowerOfTwo(s: alloc); |
36 | |
37 | // The above code can overflow in a number of interesting ways. All of those are unsigned, |
38 | // and therefore defined behavior. Still, apply some sane bounds. |
39 | const size_t intMax = std::numeric_limits<int>::max(); |
40 | if (alloc > intMax) |
41 | alloc = intMax; |
42 | |
43 | Heap::MemberData *m; |
44 | if (old) { |
45 | const size_t oldSize = sizeof(Heap::MemberData) + (old->values.size - 1) * sizeof(Value); |
46 | if (oldSize > alloc) |
47 | alloc = oldSize; |
48 | m = e->memoryManager->allocManaged<MemberData>(size: alloc); |
49 | // no write barrier required here |
50 | memcpy(dest: m, src: old, n: oldSize); |
51 | } else { |
52 | m = e->memoryManager->allocManaged<MemberData>(size: alloc); |
53 | m->init(); |
54 | } |
55 | |
56 | m->values.alloc = static_cast<uint>((alloc - sizeof(Heap::MemberData) + sizeof(Value))/sizeof(Value)); |
57 | m->values.size = m->values.alloc; |
58 | return m; |
59 | } |
60 |