blob: caaf5a454cb07dd2dee487eba9651a57c4b6aac8 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
|
#include "kernel/memory/bitmap_allocator.hpp"
#include "kapi/memory.hpp"
#include <algorithm>
#include <cstddef>
#include <cstdint>
#include <optional>
#include <ranges>
#include <span>
#include <utility>
namespace kernel::memory
{
bitmap_frame_allocator::bitmap_frame_allocator(std::span<std::uint64_t> storage, std::size_t frame_count) noexcept
: m_bitmap{storage}
, m_frame_count{frame_count}
, m_last_index{}
{
constexpr auto bits_per_word = 64uz;
auto to_fill = (frame_count + bits_per_word - 1) / bits_per_word;
std::ranges::fill(std::views::take(m_bitmap, to_fill), ~0uz);
}
auto bitmap_frame_allocator::allocate_many(std::size_t count) noexcept
-> std::optional<std::pair<kapi::memory::frame, std::size_t>>
{
if (count == 0)
{
return std::nullopt;
}
auto free_count = 0uz;
auto first_free = 0uz;
for (auto i = 0uz; i < m_frame_count; ++i)
{
auto const current = (m_last_index + i) % m_frame_count;
if (!test(current))
{
if (free_count == 0)
{
first_free = current;
}
++free_count;
if (free_count == count)
{
for (auto j = 0uz; j < count; ++j)
{
set(first_free + j);
}
m_last_index = first_free + count;
return std::make_pair(kapi::memory::frame{first_free}, count);
}
}
else
{
free_count = 0;
}
}
return std::nullopt;
}
auto bitmap_frame_allocator::release_many(std::pair<kapi::memory::frame, std::size_t> frame_set) -> void
{
auto const [start, count] = frame_set;
for (auto i = 0uz; i < count; ++i)
{
clear(start.number() + i);
}
}
auto bitmap_frame_allocator::mark_used(kapi::memory::frame frame) -> void
{
set(frame.number());
}
auto bitmap_frame_allocator::test(std::size_t index) const noexcept -> bool
{
constexpr auto bits_per_word = 64uz;
auto entry_entry = index / bits_per_word;
auto entry_offset = index % bits_per_word;
return (m_bitmap[entry_entry] & (1uz << entry_offset));
}
auto bitmap_frame_allocator::set(std::size_t index) noexcept -> void
{
constexpr auto bits_per_word = 64uz;
auto entry_entry = index / bits_per_word;
auto entry_offset = index % bits_per_word;
m_bitmap[entry_entry] |= (1uz << entry_offset);
}
auto bitmap_frame_allocator::clear(std::size_t index) noexcept -> void
{
constexpr auto bits_per_word = 64uz;
auto entry_entry = index / bits_per_word;
auto entry_offset = index % bits_per_word;
m_bitmap[entry_entry] &= ~(1uz << entry_offset);
}
} // namespace kernel::memory
|
