1/*
2 * Copyright (C) 2017 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#pragma once
27
28#include "BMalloced.h"
29#include "IsoDirectory.h"
30
31namespace bmalloc {
32
33template<typename Config>
34class IsoDirectoryPage {
35 MAKE_BMALLOCED;
36public:
37 // By my math, this results in an IsoDirectoryPage using 4036 bytes on 64-bit platforms. We allocate it
38 // with malloc, so it doesn't really matter how much memory it uses. But it's nice that this about a
39 // page, since that's quite intuitive.
40 //
41 // On 32-bit platforms, I think that this will be 2112 bytes. That's still quite intuitive.
42 //
43 // Note that this is a multiple of 32 so that it uses bitvectors efficiently.
44 static constexpr unsigned numPages = 480;
45
46 IsoDirectoryPage(IsoHeapImpl<Config>&, unsigned index);
47
48 static IsoDirectoryPage* pageFor(IsoDirectory<Config, numPages>* payload);
49
50 unsigned index() const { return m_index; }
51
52 IsoDirectory<Config, numPages> payload;
53 IsoDirectoryPage* next { nullptr };
54
55private:
56 unsigned m_index;
57};
58
59} // namespace bmalloc
60
61