Add a global interface

src/main.rs

@@ -7,7 +7,15 @@ mod vga_buffer;
 
 #[no_mangle]
 pub extern "C" fn _start() -> ! {
-    vga_buffer::print_something();
+    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

@@ -1,6 +1,16 @@
 use core::fmt;
+use lazy_static::lazy_static;
+use spin::Mutex;
 use volatile::Volatile;
 
+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) },
+    });
+}
+
 #[allow(dead_code)]
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 #[repr(u8)]
@@ -113,16 +123,3 @@ impl fmt::Write for Writer {
         Ok(())
     }
 }
-
-pub fn print_something() {
-    use core::fmt::Write;
-    let mut writer = Writer {
-        column_position: 0,
-        color_code: ColorCode::new(Color::Yellow, Color::Black),
-        buffer: unsafe { &mut *(0xb8000 as *mut Buffer) },
-    };
-
-    writer.write_byte(b'H');
-    writer.write_string("ello! ");
-    write!(writer, "The numbers are {} and {}", 42, 1.0 / 3.0).unwrap();
-}