Initial commit

Cargo.lock

@@ -1,4 +1,38 @@
+[[package]]
+name = "lazy_static"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "spin 0.4.9 (registry+https://github.com/rust-lang/crates.io-index)",
+ "version_check 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "os_boot"
 version = "0.1.0"
+dependencies = [
+ "lazy_static 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "spin 0.4.9 (registry+https://github.com/rust-lang/crates.io-index)",
+ "volatile 0.2.4 (registry+https://github.com/rust-lang/crates.io-index)",
+]
 
+[[package]]
+name = "spin"
+version = "0.4.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
+name = "version_check"
+version = "0.1.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
+name = "volatile"
+version = "0.2.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[metadata]
+"checksum lazy_static 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ca488b89a5657b0a2ecd45b95609b3e848cf1755da332a0da46e2b2b1cb371a7"
+"checksum spin 0.4.9 (registry+https://github.com/rust-lang/crates.io-index)" = "37b5646825922b96b5d7d676b5bb3458a54498e96ed7b0ce09dc43a07038fea4"
+"checksum version_check 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)" = "7716c242968ee87e5542f8021178248f267f295a5c4803beae8b8b7fd9bc6051"
+"checksum volatile 0.2.4 (registry+https://github.com/rust-lang/crates.io-index)" = "54d4343a2df2d65144a874f95950754ee7b7e8594f6027aae8c7d0f4858a3fe8"

Cargo.toml

@@ -4,6 +4,12 @@ version = "0.1.0"
 authors = ["ishanjain28 <ishanjain28@gmail.com>"]
 
 [dependencies]
+volatile = "0.2.3"
+spin = "0.4.6"
+
+[dependencies.lazy_static]
+version = "1.0"
+features = ["spin_no_std"]
 
 [package.metadata.bootimage]
 default-target = "x86_64-os.json"

src/main.rs

@@ -2,7 +2,17 @@
 #![no_std] // don't include rust std lib
 #![no_main] // disable all rust entry point
 
+extern crate volatile;
+extern crate spin;
+
+#[macro_use]
+extern crate lazy_static;
+
+mod vga_buffer;
+
+use core::fmt::Write;
 use core::panic::PanicInfo;
+use vga_buffer::{Buffer, Color, ColorCode, Writer};
 
 /// This function is called on panic.
 #[panic_implementation]
@@ -11,18 +21,12 @@ pub fn panic(_info: &PanicInfo) -> ! {
     loop {}
 }
 
-static HELLO: &[u8] = b"Hello World!";
-
 #[no_mangle] // don't change the name of function in symbol table
 pub extern "C" fn _start() -> ! {
-    let vga_buffer = 0xb8000 as *mut u8;
-
-    for (i, &byte) in HELLO.iter().enumerate() {
-        unsafe {
-            *vga_buffer.offset(i as isize * 2) = byte;
-            *vga_buffer.offset(i as isize * 2 + 1) = 0xb;
-        }
-    }
+    use core::fmt::Write;
+    vga_buffer::WRITER.lock().write_str("Hello again").unwrap();
+    write!(vga_buffer::WRITER.lock(), ", some numbers: {} {}", 42, 1.337).unwrap();
 
     loop {}
 }
+

src/vga_buffer.rs

@@ -0,0 +1,133 @@
+use core::fmt;
+use volatile::Volatile;
+use spin::Mutex;
+
+#[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,
+}
+
+// represents a color by combining foreground and background
+#[derive(Debug, Clone, Copy, Eq, PartialEq)]
+pub struct ColorCode(u8);
+
+impl ColorCode {
+    pub fn new(foreground: Color, background: Color) -> ColorCode {
+        // foreground/background use 4 bits
+        // u8 is used because there is no u4 in rust
+        // The 4 most significant bits in ColorCode store background
+        // and 4 least significant bits store foreground color
+        ColorCode((background as u8) << 4 | (foreground as u8))
+    }
+}
+
+#[derive(Debug, Clone, Eq, PartialEq, Copy)]
+#[repr(C)]
+struct ScreenChar {
+    ascii_character: u8,
+    color_code: ColorCode,
+}
+
+const BUFFER_HEIGHT: usize = 25;
+const BUFFER_WIDTH: usize = 80;
+
+// This represents the vga buffer of size 25 * 80.
+pub struct Buffer {
+    chars: [[Volatile<ScreenChar>; BUFFER_WIDTH]; BUFFER_HEIGHT],
+}
+
+pub struct Writer {
+    pub column_position: usize,
+    pub color_code: ColorCode,
+    pub buffer: &'static mut Buffer,
+}
+
+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) },
+    });
+}
+
+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: color_code,
+                });
+
+                self.column_position += 1;
+            }
+        }
+    }
+
+    pub fn write_string(&mut self, ip: &str) {
+        for byte in ip.bytes() {
+            match byte {
+                0x20...0x7e | b'\n' => self.write_byte(byte),
+                _ => self.write_byte(0xfe),
+            }
+        }
+    }
+
+    fn new_line(&mut self) {
+        for row in 1..BUFFER_HEIGHT {
+            for col in 1..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) {
+        let blank = ScreenChar {
+            ascii_character: b' ',
+            color_code: self.color_code,
+        };
+
+        for col in 0..BUFFER_WIDTH {
+            self.buffer.chars[row][col].write(blank);
+        }
+    }
+}
+
+impl fmt::Write for Writer {
+    fn write_str(&mut self, s: &str) -> fmt::Result {
+        self.write_string(s);
+
+        Ok(())
+    }
+}