205 lines
5.7 KiB
Rust
205 lines
5.7 KiB
Rust
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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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lazy_static! {
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/// A global `Writer` instance that can be used for printing to the VGA text buffer.
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///
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/// Used by the `print!` and `println!` macros.
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pub static ref WRITER: Mutex<Writer> = Mutex::new(Writer {
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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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/// The standard color palette in VGA text mode.
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#[allow(dead_code)]
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#[derive(Debug, Clone, Copy, PartialEq, Eq)]
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#[repr(u8)]
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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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/// A combination of a foreground and a background color.
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#[derive(Debug, Clone, Copy, PartialEq, Eq)]
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#[repr(transparent)]
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struct ColorCode(u8);
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impl ColorCode {
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/// Create a new `ColorCode` with the given foreground and background colors.
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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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/// A screen character in the VGA text buffer, consisting of an ASCII character and a `ColorCode`.
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#[derive(Debug, Clone, Copy, PartialEq, Eq)]
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#[repr(C)]
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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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/// The height of the text buffer (normally 25 lines).
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const BUFFER_HEIGHT: usize = 25;
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/// The width of the text buffer (normally 80 columns).
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const BUFFER_WIDTH: usize = 80;
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/// A structure representing the VGA text buffer.
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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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/// A writer type that allows writing ASCII bytes and strings to an underlying `Buffer`.
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///
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/// Wraps lines at `BUFFER_WIDTH`. Supports newline characters and implements the
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/// `core::fmt::Write` trait.
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pub struct Writer {
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column_position: usize,
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color_code: ColorCode,
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buffer: &'static mut Buffer,
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}
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impl Writer {
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/// Writes an ASCII byte to the buffer.
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///
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/// Wraps lines at `BUFFER_WIDTH`. Supports the `\n` newline character.
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pub fn write_byte(&mut self, byte: u8) {
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match byte {
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b'\n' => self.new_line(),
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byte => {
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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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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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/// Writes the given ASCII string to the buffer.
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///
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/// Wraps lines at `BUFFER_WIDTH`. Supports the `\n` newline character. Does **not**
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/// support strings with non-ASCII characters, since they can't be printed in the VGA text
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/// mode.
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fn write_string(&mut self, s: &str) {
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for byte in s.bytes() {
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match byte {
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// printable ASCII byte or newline
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0x20..=0x7e | b'\n' => self.write_byte(byte),
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// not part of printable ASCII range
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_ => self.write_byte(0xfe),
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}
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}
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}
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/// Shifts all lines one line up and clears the last row.
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fn new_line(&mut self) {
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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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self.clear_row(BUFFER_HEIGHT - 1);
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self.column_position = 0;
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}
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/// Clears a row by overwriting it with blank characters.
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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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}
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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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/// Like the `print!` macro in the standard library, but prints to the VGA text buffer.
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#[macro_export]
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macro_rules! print {
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($($arg:tt)*) => ($crate::vga_buffer::_print(format_args!($($arg)*)));
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}
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/// Like the `println!` macro in the standard library, but prints to the VGA text buffer.
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#[macro_export]
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macro_rules! println {
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() => ($crate::print!("\n"));
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($($arg:tt)*) => ($crate::print!("{}\n", format_args!($($arg)*)));
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}
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/// Prints the given formatted string to the VGA text buffer through the global `WRITER` instance.
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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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WRITER.lock().write_fmt(args).unwrap();
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}
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#[cfg(test)]
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use crate::{serial_print, serial_println};
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#[test_case]
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fn test_println_simple() {
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serial_print!("test_println... ");
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println!("test_println_simple output");
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serial_println!("[ok]");
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}
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#[test_case]
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fn test_println_many() {
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serial_print!("test_println_many... ");
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for _ in 0..200 {
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println!("test_println_many output");
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}
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serial_println!("[ok]");
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}
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#[test_case]
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fn test_println_output() {
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serial_print!("test_println_output... ");
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let s = "Some test string that fits on a single line";
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println!("{}", s);
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for (i, c) in s.chars().enumerate() {
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let screen_char = WRITER.lock().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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serial_println!("[ok]");
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}
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