| 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, as m gets marked later when member data is set |
| 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 |