1/*
2 * Copyright (C) 2014 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 SmallAllocator_h
27#define SmallAllocator_h
28
29#include "BAssert.h"
30#include "SmallChunk.h"
31#include "SmallLine.h"
32
33namespace bmalloc {
34
35// Helper object for allocating small objects.
36
37class SmallAllocator {
38public:
39    SmallAllocator();
40    SmallAllocator(size_t);
41
42    bool isNull() { return !m_ptr; }
43    SmallLine* line();
44
45    bool canAllocate() { return !!m_remaining; }
46    void* allocate();
47
48    unsigned short objectCount();
49    unsigned char derefCount();
50    void refill(SmallLine*);
51
52private:
53    char* m_ptr;
54    unsigned short m_size;
55    unsigned char m_remaining;
56    unsigned char m_maxObjectCount;
57};
58
59inline SmallAllocator::SmallAllocator()
60    : m_ptr()
61    , m_size()
62    , m_remaining()
63    , m_maxObjectCount()
64{
65}
66
67inline SmallAllocator::SmallAllocator(size_t size)
68    : m_ptr()
69    , m_size(size)
70    , m_remaining()
71    , m_maxObjectCount(smallLineSize / size)
72{
73}
74
75inline SmallLine* SmallAllocator::line()
76{
77    return SmallLine::get(canAllocate() ? m_ptr : m_ptr - 1);
78}
79
80inline void* SmallAllocator::allocate()
81{
82    BASSERT(m_remaining);
83    BASSERT(m_size >= SmallLine::minimumObjectSize);
84
85    --m_remaining;
86    char* result = m_ptr;
87    m_ptr += m_size;
88    BASSERT(isSmall(result));
89    return result;
90}
91
92inline unsigned short SmallAllocator::objectCount()
93{
94    return m_maxObjectCount - m_remaining;
95}
96
97inline unsigned char SmallAllocator::derefCount()
98{
99    return SmallLine::maxRefCount - objectCount();
100}
101
102inline void SmallAllocator::refill(SmallLine* line)
103{
104    BASSERT(!canAllocate());
105    line->concurrentRef(SmallLine::maxRefCount);
106    m_ptr = line->begin();
107    m_remaining = m_maxObjectCount;
108}
109
110} // namespace bmalloc
111
112#endif // SmallAllocator_h
113