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#include "arch/memory/region_allocator.hpp"
#include "kapi/memory/address.hpp"
#include "kapi/memory/frame.hpp"
#include <multiboot2/information.hpp>
#include <algorithm>
#include <cstddef>
#include <optional>
#include <ranges>
#include <utility>
namespace arch::memory
{
namespace
{
constexpr auto last_frame(multiboot2::memory_map::region const & region)
{
return kapi::memory::frame::containing(kapi::memory::physical_address{region.base + region.size_in_B - 1});
}
constexpr auto falls_within(kapi::memory::frame const & candidate, kapi::memory::frame const & start,
kapi::memory::frame const & end)
{
return candidate >= start && candidate <= end;
}
} // namespace
region_allocator::region_allocator(memory_information const & mem_info)
: m_next_frame{}
, m_current_region{}
, m_memory_map{mem_info.memory_map}
, m_kernel_start{kapi::memory::frame::containing(mem_info.image_range.first)}
, m_kernel_end{kapi::memory::frame::containing(mem_info.image_range.second)}
, m_multiboot_start{kapi::memory::frame::containing(mem_info.mbi_range.first)}
, m_multiboot_end{kapi::memory::frame::containing(mem_info.mbi_range.second)}
, m_multiboot_information{mem_info.mbi}
{
choose_next_region();
}
auto region_allocator::choose_next_region() -> void
{
m_current_region.reset();
auto remaining_regions =
m_memory_map | //
std::views::filter(&multiboot2::memory_map::region::available) |
std::views::filter([this](auto const & region) -> bool { return last_frame(region) >= m_next_frame; });
auto lowest_region =
std::ranges::min_element(remaining_regions, [](auto lhs, auto rhs) -> bool { return lhs.base < rhs.base; });
if (lowest_region == remaining_regions.end())
{
return;
}
m_current_region = *lowest_region;
if (auto start_of_region = kapi::memory::frame::containing(kapi::memory::physical_address{m_current_region->base});
start_of_region > m_next_frame)
{
m_next_frame = start_of_region;
}
}
auto region_allocator::find_next_frame() -> std::optional<kapi::memory::frame>
{
if (!m_current_region || m_next_frame > last_frame(*m_current_region))
{
choose_next_region();
if (!m_current_region)
{
return std::nullopt;
}
}
auto advanced = true;
while (advanced)
{
advanced = false;
if (falls_within(m_next_frame, m_kernel_start, m_kernel_end))
{
m_next_frame = m_kernel_end + 1;
advanced = true;
continue;
}
if (falls_within(m_next_frame, m_multiboot_start, m_multiboot_end))
{
m_next_frame = m_multiboot_end + 1;
advanced = true;
continue;
}
if (m_multiboot_information)
{
for (auto const & module : m_multiboot_information->modules())
{
auto module_start = kapi::memory::frame::containing(kapi::memory::physical_address{module.start_address});
auto module_end = kapi::memory::frame::containing(kapi::memory::physical_address{module.end_address});
if (falls_within(m_next_frame, module_start, module_end))
{
m_next_frame = module_end + 1;
advanced = true;
break;
}
}
}
}
if (m_next_frame > last_frame(*m_current_region))
{
choose_next_region();
}
return m_current_region.transform([this](auto) -> auto { return m_next_frame; });
}
auto region_allocator::allocate_many(std::size_t count) noexcept
-> std::optional<std::pair<kapi::memory::frame, std::size_t>>
{
while (m_current_region)
{
auto result = find_next_frame();
if (result)
{
auto region_end = last_frame(*m_current_region);
if ((region_end.number() - result->number()) >= count)
{
m_next_frame = m_next_frame + count;
return std::make_pair(*result, count);
}
else
{
m_next_frame = region_end + 1;
choose_next_region();
}
}
}
return std::nullopt;
}
auto region_allocator::mark_used(kapi::memory::frame frame) -> void
{
if (frame < m_next_frame)
{
m_next_frame = frame;
find_next_frame();
}
}
auto region_allocator::release_many(std::pair<kapi::memory::frame, std::size_t>) -> void {}
auto region_allocator::next_free_frame() noexcept -> std::optional<kapi::memory::frame>
{
return find_next_frame();
}
} // namespace arch::memory
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