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#include "x86_64/vga/text.hpp"
#include "x86_64/boot/boot.hpp"
#include "x86_64/vga/crtc.hpp"
#include <algorithm>
#include <bit>
#include <cstddef>
#include <string_view>
#include <utility>
namespace teachos::vga::x86_64::text
{
using boot::x86_64::vga_buffer_pointer;
namespace
{
// NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
auto constinit buffer_offset = std::ptrdiff_t{};
constexpr auto DEFAULT_TEXT_BUFFER_WIDTH = 80U;
constexpr auto DEFAULT_TEXT_BUFFER_HEIGHT = 25U;
constexpr auto CURSOR_ENABLED_BIT = 5U;
auto write_char(char code_point, attribute attribute) -> void
{
vga_buffer_pointer[buffer_offset++] = std::pair{code_point, std::bit_cast<std::byte>(attribute)};
};
} // namespace
auto device::clear(attribute attribute) -> void
{
buffer_offset = 0;
std::ranges::fill_n(vga_buffer_pointer.get(), DEFAULT_TEXT_BUFFER_WIDTH * DEFAULT_TEXT_BUFFER_HEIGHT,
std::pair{' ', std::bit_cast<std::byte>(attribute)});
}
auto device::cursor(bool enabled) -> void
{
auto cursor_disable_byte = std::byte{!enabled} << CURSOR_ENABLED_BIT;
crtc::address::write(crtc::registers::cursor_start);
crtc::data::write(crtc::data::read() | cursor_disable_byte);
}
auto device::newline() -> void
{
auto current_line = buffer_offset / DEFAULT_TEXT_BUFFER_WIDTH;
auto next_line = current_line + 1;
if (std::cmp_greater_equal(next_line, DEFAULT_TEXT_BUFFER_HEIGHT))
{
auto begin = vga_buffer_pointer + DEFAULT_TEXT_BUFFER_WIDTH;
auto end = vga_buffer_pointer + DEFAULT_TEXT_BUFFER_WIDTH * DEFAULT_TEXT_BUFFER_HEIGHT;
std::ranges::move(begin, end, vga_buffer_pointer.get());
buffer_offset = current_line * DEFAULT_TEXT_BUFFER_WIDTH;
}
else
{
buffer_offset = next_line * DEFAULT_TEXT_BUFFER_WIDTH;
}
}
auto device::write(std::string_view code_points, attribute attribute) -> void
{
std::ranges::for_each(code_points, [&](auto code_point) -> void { write_char(code_point, attribute); });
}
auto device::writeln(std::string_view code_points, attribute attribute) -> void
{
std::ranges::for_each(code_points, [&](auto code_point) -> void { write_char(code_point, attribute); });
newline();
}
} // namespace teachos::vga::x86_64::text
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