Merge pull request #1 from Amjad50/master

Bugs and error fixes

src/chip8.rs

@@ -413,7 +413,10 @@ impl Chip8 {
                 // If it is 1, do collision detection and set the pixel.
                 if pixels & 0x80 >> col > 0 {
                     // Get current pixel.
-                    let idx = vx + col + ((vy + row) * 64);
+                    let col = (vx + col) % 64;
+                    let row = (vy + row) % 32;
+
+                    let idx = col + (row * 64);
                     let current_pixel = self.graphics_buffer[idx];
 
                     // If collision, set VF to 1, else 0.

src/main.rs

@@ -129,6 +129,15 @@ impl Debugger {
 
 fn main() {
     let args: Vec<String> = env::args().collect();
+
+    // mostly redundant
+    assert_eq!(args.len() > 0, true);
+
+    if args.len() < 2 {
+        println!("USAGE: {} <rom-file>", args[0]);
+        return;
+    }
+
     let filename = &args[1];
 
     let emulator = Emulator::init(filename);