193 lines
5.9 KiB
Rust
193 lines
5.9 KiB
Rust
// 用 volatile 以防止我们针对内存的操作被优化掉
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// 因为我们是通过对内存地址 0xb8000 写入来操作 VGA Buffer 的
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// 这实际上是通过内存操作的副作用来实现的
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// 但由于我们从未访问过这段内存，所以它可能会在未来的 Rust 编译器中被优化掉
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// 为了告诉编译器，这部分针对内存的操作是我们故意的，就需要用到 volatile crate
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use core::fmt;
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use lazy_static::lazy_static;
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use spin::Mutex;
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use volatile::Volatile;
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#[allow(dead_code)] // 允许未使用的代码
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#[derive(Debug, Clone, Copy, PartialEq, Eq)] // 启用 copy 语义
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#[repr(u8)] // 每个 enum variant 都以 u8 存储
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pub enum Color {
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Black = 0,
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Blue = 1,
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Green = 2,
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Cyan = 3,
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Red = 4,
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Magenta = 5,
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Brown = 6,
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LightGray = 7,
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DarkGray = 8,
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LightBlue = 9,
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LightGreen = 10,
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LightCyan = 11,
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LightRed = 12,
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Pink = 13,
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Yellow = 14,
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White = 15,
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}
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#[derive(Debug, Clone, Copy, PartialEq, Eq)]
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#[repr(transparent)] // 为了保证 ColorCode 和 u8 有同样的数据布局
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struct ColorCode(u8);
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impl ColorCode {
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fn new(foreground: Color, background: Color) -> ColorCode {
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ColorCode((background as u8) << 4 | (foreground as u8))
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}
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}
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#[derive(Debug, Clone, Copy, PartialEq, Eq)]
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#[repr(C)] // 使数据结构的布局和 C 一样，这样才能保证每个成员的顺序一致
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struct ScreenChar {
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ascii_character: u8,
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color_code: ColorCode,
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}
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const BUFFER_HEIGHT: usize = 25;
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const BUFFER_WIDTH: usize = 80;
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#[repr(transparent)]
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struct Buffer {
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chars: [[Volatile<ScreenChar>; BUFFER_WIDTH]; BUFFER_HEIGHT],
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}
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pub struct Writer {
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column_position: usize, // 当前光标所在列
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color_code: ColorCode, // 当前颜色代码
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buffer: &'static mut Buffer, // VGA Buffer 的引用，生命周期是 'static
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}
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impl Writer {
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pub fn write_byte(&mut self, byte: u8) {
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match byte {
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// 如果碰到 '\n' 则创建新行
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b'\n' => self.new_line(),
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byte => {
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// 如果列数超出限定的阈值，则创建新行
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if self.column_position >= BUFFER_WIDTH {
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self.new_line();
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}
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let row = BUFFER_HEIGHT - 1;
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let col = self.column_position;
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let color_code = self.color_code;
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// 将 ScreenChar 写入到 Buffer 的相应位置
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self.buffer.chars[row][col].write(ScreenChar {
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ascii_character: byte,
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color_code,
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});
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self.column_position += 1;
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}
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}
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}
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fn new_line(&mut self) {
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// 将所有字符上移一行
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for row in 1..BUFFER_HEIGHT {
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for col in 0..BUFFER_WIDTH {
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let character = self.buffer.chars[row][col].read();
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self.buffer.chars[row - 1][col].write(character);
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}
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}
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// 清空最下面的一行
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self.clear_row(BUFFER_HEIGHT - 1);
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// 将当前列的位置设为 0
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self.column_position = 0;
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}
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fn clear_row(&mut self, row: usize) {
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let blank = ScreenChar {
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ascii_character: b' ',
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color_code: self.color_code,
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};
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for col in 0..BUFFER_WIDTH {
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self.buffer.chars[row][col].write(blank);
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}
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}
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pub fn write_string(&mut self, s: &str) {
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for byte in s.bytes() {
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// Rust 字符串是以 UTF-8 编码的，然而 VGA Buffer 只支持 ASCII字符，所以有可能存在无法打印的字符
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match byte {
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// 当在 ASCII 字符范围内时，打印它
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0x20..=0x7e | b'\n' => self.write_byte(byte),
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// 否则打印 ■
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_ => self.write_byte(0xfe),
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}
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}
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}
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}
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impl fmt::Write for Writer {
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fn write_str(&mut self, s: &str) -> fmt::Result {
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self.write_string(s);
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Ok(())
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}
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}
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// 将 Writer 设置为静态以便调用
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lazy_static! { // 内置的 static 会用到标准库里的一些东西，所以这里用 lazy_static
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pub static ref WRITER: Mutex<Writer> = Mutex::new(Writer { // 用互斥锁来防止冲突
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column_position: 0,
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color_code: ColorCode::new(Color::Yellow, Color::Black),
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buffer: unsafe { &mut *(0xb8000 as *mut Buffer) }
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});
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}
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// 将宏导出到 crate 的根，这样我们就可以用
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// use crate::println
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// 来使用它
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#[macro_export]
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macro_rules! print { // print!()
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($($arg:tt)*) => ($crate::vga_buffer::_print(format_args!($($arg)*)));
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}
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#[macro_export]
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macro_rules! println { // println!()
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() => ($crate::print!("\n"));
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($($arg:tt)*) => ($crate::print!("{}\n", format_args!($($arg)*)));
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}
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// 由于宏需要从外部调用这个函数，所以它必须是公开的
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// 用 #[doc(hidden)] 来阻止它生成文档
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#[doc(hidden)]
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pub fn _print(args: fmt::Arguments) {
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use core::fmt::Write;
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use x86_64::instructions::interrupts;
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interrupts::without_interrupts(|| {
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WRITER.lock().write_fmt(args).unwrap();
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});
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}
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#[test_case]
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fn test_println_simple() {
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// 测试单行 println!
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println!("test_println_simple output");
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}
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#[test_case]
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fn test_println_many() {
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// 测试多行 println!
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for _ in 0..10 {
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println!("test_println_many output");
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}
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}
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#[test_case]
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fn test_println_output() {
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// 测试字符是否真的打印到了屏幕上
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use core::fmt::Write;
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use x86_64::instructions::interrupts;
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let s = "Some test string that fits on a single line";
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interrupts::without_interrupts(|| {
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let mut writer = WRITER.lock();
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writeln!(writer, "\n{}", s).expect("writeln failed");
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for (i, c) in s.chars().enumerate() {
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let screen_char = writer.buffer.chars[BUFFER_HEIGHT - 2][i].read();
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assert_eq!(char::from(screen_char.ascii_character), c);
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}
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});
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}
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