Improve Hello World! code

Avoid special core features and complicated iterator chaining to make the code simpler overall.

src/lib.rs

@@ -13,27 +13,26 @@
 // limitations under the License.
 
 #![feature(no_std, lang_items)]
-#![feature(core_slice_ext, core_str_ext, core_intrinsics)]
 #![no_std]
 
 extern crate rlibc;
 
-use core::intrinsics::offset;
-
 #[no_mangle]
 pub extern fn rust_main() {
     // ATTENTION: we have a very small stack and no guard page
-    let x = ["Hello", " ", "World", "!"];
-    let screen_pointer = 0xb8000 as *const u16;
 
-    for (byte, i) in x.iter().flat_map(|s| s.bytes()).zip(0..) {
-        let c = 0x1f00 | (byte as u16);
-        unsafe {
-            let screen_char = offset(screen_pointer, i) as *mut u16;
-            *screen_char = c
-        }
+    let hello = b"Hello World!";
+    let color_byte = 0x1f; // white foreground, blue background
+
+    let mut hello_colored = [color_byte; 24];
+    for (i, char_byte) in hello.into_iter().enumerate() {
+        hello_colored[i*2] = *char_byte;
     }
 
+    // write `Hello World!` to the center of the VGA text buffer
+    let buffer_ptr = (0xb8000 + 1988) as *mut _;
+    unsafe { *buffer_ptr = hello_colored };
+
     loop{}
 }