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 Chunk_h
27#define Chunk_h
28
29#include "ObjectType.h"
30#include "Sizes.h"
31#include "VMAllocate.h"
32
33namespace bmalloc {
34
35template<class Traits>
36class Chunk {
37public:
38    typedef typename Traits::Page Page;
39    typedef typename Traits::Line Line;
40    static const size_t lineSize = Traits::lineSize;
41    static const size_t chunkSize = Traits::chunkSize;
42    static const size_t chunkOffset = Traits::chunkOffset;
43    static const uintptr_t chunkMask = Traits::chunkMask;
44
45    static Chunk* create();
46    static Chunk* get(void*);
47
48    Page* begin() { return Page::get(Line::get(m_memory)); }
49    Page* end() { return &m_pages[pageCount]; }
50
51    Line* lines() { return m_lines; }
52    Page* pages() { return m_pages; }
53
54private:
55    static_assert(!(vmPageSize % lineSize), "vmPageSize must be an even multiple of line size");
56    static_assert(!(chunkSize % lineSize), "chunk size must be an even multiple of line size");
57
58    static const size_t lineCount = chunkSize / lineSize;
59    static const size_t pageCount = chunkSize / vmPageSize;
60
61    Line m_lines[lineCount];
62    Page m_pages[pageCount];
63
64    // Align to vmPageSize to avoid sharing physical pages with metadata.
65    // Otherwise, we'll confuse the scavenger into trying to scavenge metadata.
66    alignas(vmPageSize) char m_memory[];
67};
68
69template<class Traits>
70inline auto Chunk<Traits>::create() -> Chunk*
71{
72    size_t vmSize = bmalloc::vmSize(chunkSize);
73    std::pair<void*, Range> result = vmAllocate(vmSize, superChunkSize, chunkOffset);
74    return new (result.first) Chunk;
75}
76
77template<class Traits>
78inline auto Chunk<Traits>::get(void* object) -> Chunk*
79{
80    BASSERT(isSmallOrMedium(object));
81    return static_cast<Chunk*>(mask(object, chunkMask));
82}
83
84}; // namespace bmalloc
85
86#endif // Chunk
87