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vga_buffer.rs
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vga_buffer.rs
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use core::fmt;
use spin::Mutex;
use volatile::Volatile;
use lazy_static::lazy_static;
#[allow(dead_code)]
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[repr(u8)]
pub enum Color {
Black = 0,
Blue = 1,
Green = 2,
Cyan = 3,
Red = 4,
Magenta = 5,
Brown = 6,
LightGray = 7,
DarkGray = 8,
LightBlue = 9,
LightGreen = 10,
LightCyan = 11,
LightRed = 12,
Pink = 13,
Yellow = 14,
White = 15,
}
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[repr(transparent)]
struct ColorCode(u8);
impl ColorCode {
fn new(foreground: Color, backgroud: Color) -> ColorCode {
ColorCode((backgroud as u8) << 4 | (foreground as u8))
}
}
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[repr(C)]
struct ScreenChar {
ascii_character: u8,
color_code: ColorCode,
}
pub const BUFFER_HEIGHT: usize = 25;
pub const BUFFER_WIDTH: usize = 80;
#[repr(transparent)]
struct Buffer {
chars: [[Volatile<ScreenChar>; BUFFER_WIDTH]; BUFFER_HEIGHT],
}
pub struct Writer {
column_position: usize,
color_code: ColorCode,
buffer: &'static mut Buffer,
}
impl Writer {
pub fn write_byte(&mut self, byte: u8) {
match byte {
b'\n' => self.new_line(),
byte => {
if self.column_position >= BUFFER_WIDTH {
self.new_line();
}
let row = BUFFER_HEIGHT - 1;
let col = self.column_position;
let color_code = self.color_code;
self.buffer.chars[row][col].write(ScreenChar {
ascii_character: byte,
color_code,
});
self.column_position += 1;
}
}
}
fn new_line(&mut self) {
for row in 1..BUFFER_HEIGHT {
for col in 0..BUFFER_WIDTH {
let character = self.buffer.chars[row][col].read();
self.buffer.chars[row - 1][col].write(character);
}
}
self.clear_row(BUFFER_HEIGHT - 1);
self.column_position = 0;
}
fn clear_row(&mut self, row: usize) {
for col in 0..BUFFER_WIDTH {
self.buffer.chars[row][col].write(ScreenChar {
ascii_character: b' ',
color_code: self.color_code,
});
}
}
pub fn write_string(&mut self, s: &str) {
for byte in s.bytes() {
match byte {
// printable ASCII byte or newline
0x20..=0x7e | b'\n' => self.write_byte(byte),
// not part of printable ASCII range, we print a ■ character
_ => self.write_byte(0xfe),
}
}
}
}
impl fmt::Write for Writer {
fn write_str(&mut self, s: &str) -> fmt::Result {
self.write_string(s);
Ok(())
}
}
lazy_static! {
pub static ref WRITER: Mutex<Writer> = Mutex::new(Writer {
column_position: 0,
color_code: ColorCode::new(Color::Yellow, Color::Black),
buffer: unsafe { &mut *(0xb8000 as *mut Buffer) },
});
}
// macro for printing
#[macro_export]
macro_rules! println {
() => (print!("\n"));
($($arg:tt)*) => ($crate::print!("{}\n", format_args!($($arg)*)));
}
#[macro_export]
macro_rules! print {
($($arg:tt)*) => ($crate::vga_buffer::_print(format_args!($($arg)*)));
}
#[doc(hidden)]
pub fn _print(args: fmt::Arguments) {
use core::fmt::Write;
use x86_64::instructions::interrupts;
interrupts::without_interrupts(|| {
WRITER.lock().write_fmt(args).unwrap();
})
}
#[cfg(test)]
use crate::{serial_print, serial_println};
#[test_case]
fn test_println_simple() {
serial_print!("test_println... ");
println!("test_println_simple output");
serial_println!("[ok]");
}
#[test_case]
fn test_println_many() {
serial_print!("test_println_many... ");
for _ in 0..200 {
println!("test_println_many output");
}
serial_println!("[ok]");
}
#[test_case]
fn test_println_output() {
use core::fmt::Write;
use x86_64::instructions::interrupts;
serial_print!("test_println_output... ");
let s = "Some test string that fits on a single line";
interrupts::without_interrupts(|| {
let mut writer = WRITER.lock();
writeln!(writer, "\n{}", s).expect("writeln failed");
for (i, c) in s.chars().enumerate() {
let screen_char = writer.buffer.chars[BUFFER_HEIGHT - 2][i].read();
assert_eq!(char::from(screen_char.ascii_character), c);
}
});
serial_println!("[ok]");
}