brokem implementation on main.rs - no regression

src/main.rs

@@ -12,11 +12,29 @@ use crate::cpu::Cpu;
 
 fn main() {
     let args: Vec<String> = std::env::args().collect();
+    match args.len() {
+        1 => run_nestest(),
+        3 if args[1] == "blargg" => run_blargg(&args[2]),
+        2 => run_cart(&args[1]),
+        _ => eprintln!("usage: rnes [<rom> | blargg <rom>]"),
+    }
+}
 
-    if args.len() > 1 {
-        run_blargg(&args[1]);
-    } else {
-        run_nestest();
+fn run_cart(path: &str) {
+    let cart = Cartridge::from_file(path).unwrap();
+    let mut bus = NesBus::new(cart);
+    let mut cpu = Cpu::new();
+    cpu.reset(&mut bus);                    // boot from $FFFC-$FFFD
+    let mut renderer = PpmRenderer::new();
+
+    for _ in 0..frames {                    // a few frames to settle the title screen
+        while !bus.ppu.frame_done() {
+            let cycles = cpu.step(&mut bus);
+            bus.ppu.tick(&mut bus.cart, cycles as u64);   // 3 PPU dots per CPU cycle
+        }
+        if bus.ppu.take_nmi() { cpu.set_nmi(); }          // loop bridges NMI
+        renderer.present(bus.ppu.framebuffer(), 256, 240);
+        bus.ppu.begin_frame();
     }
 }