1/*
2 * Copyright (C) 2014-2018 Apple Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
14 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
17 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
18 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
19 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
20 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
21 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
23 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#ifndef SmallLine_h
27#define SmallLine_h
28
29#include "BAssert.h"
30#include "Mutex.h"
31#include "ObjectType.h"
32#include <mutex>
33
34namespace bmalloc {
35
36class SmallLine {
37public:
38 void ref(std::unique_lock<Mutex>&, unsigned char = 1);
39 bool deref(std::unique_lock<Mutex>&);
40 unsigned refCount(std::unique_lock<Mutex>&) { return m_refCount; }
41
42 char* begin();
43 char* end();
44
45private:
46 unsigned char m_refCount;
47
48static_assert(
49 smallLineSize / alignment <= std::numeric_limits<decltype(m_refCount)>::max(),
50 "maximum object count must fit in SmallLine::m_refCount");
51
52};
53
54inline void SmallLine::ref(std::unique_lock<Mutex>&, unsigned char refCount)
55{
56 BASSERT(!m_refCount);
57 m_refCount = refCount;
58}
59
60inline bool SmallLine::deref(std::unique_lock<Mutex>&)
61{
62 BASSERT(m_refCount);
63 --m_refCount;
64 return !m_refCount;
65}
66
67} // namespace bmalloc
68
69#endif // SmallLine_h
70