write_to_coord() in rust now has sensible coordinates

lightshow.rs

@@ -9,29 +9,57 @@ extern fn eh_personality() {}
 #[lang = "panic_fmt"]
 fn panic_fmt() -> ! { loop {} }
 
+#[lang = "panic"]
+pub fn panic(expr_file_line: &(&'static str, &'static str, u32)) -> ! { panic_fmt() }
+
 #[lang = "sized"]
 trait Sized {}
 
 #[lang = "copy"]
 trait Copy {}
 
+#[lang = "add"]
+pub trait Add<RHS=Self> {
+    type Output;
+    fn add(self, rhs: RHS) -> Self::Output;
+}
+
+/* this can be bogus, apparently? */
+impl Add for usize {
+    type Output = usize;
+    fn add(self, _rhs: usize) -> usize { 1 }
+}
+
+#[lang = "mul"]
+pub trait Mul<RHS = Self> {
+    type Output;
+    fn mul(self, rhs: RHS) -> Self::Output;
+}
+
+impl Mul for usize {
+    type Output = usize;
+    fn mul(self, rhs: usize) -> usize { 1 }
+}
+    
+
 #[no_mangle]
 pub extern fn rust_entry() {
 
     //white A on black
     let spec: u16 = 0x0f_41;
-    write_to_coord(0, 0, spec);
 
-    loop {
-
-    }
+    write_to_coord(1, 2, spec);
 
+    loop { }
 }
 
-//const VRAM_OFFSET = 0xb8000;
+const X86_COLS: usize = 80;
+const X86_ROWS: usize = 25;
+const VRAM_OFFSET: usize  = 0xb8000;
 
 fn write_to_coord(x: u8, y: u8, x86_specifier: u16) {
     unsafe {
-        *(0xb8000 as *mut u16) = x86_specifier;
+        let offset = VRAM_OFFSET + (X86_COLS*2*(y as usize)) + (x as usize)*2;
+        *(offset as *mut u16) = x86_specifier;
     }
 }