starting to implement opcodes...

src/main.rs

@@ -13,6 +13,8 @@ struct Args {
 }
 
 type Register = u16;
+type Instruction = u8;
+type Address = u16;
 type ROM = Vec<u8>;
 
 struct Memory {
@@ -29,7 +31,7 @@ impl Memory {
             ram: [0x0; 8192],
         }
     }
-    fn get(&self, address: u16) -> u8 {
+    fn get(&self, address: Address) -> u8 {
         match address {
             0x0..0x8000 => {
                 // rom access
@@ -100,16 +102,33 @@ struct CPU {
 }
 
 impl CPU {
-    fn execute(&mut self, opcode: u8) {
+    fn exec_next(&mut self) {
+        let opcode = self.next_opcode();
+        let p1 = self.next_opcode();
+        let p2 = self.next_opcode();
         match opcode {
-            0 => {
+            0x0 => {
                 // noop
             }
+            0x01 => {
+                self.state.bc = u8s_to_u16(&p1, &p2);
+            }
+            0x66 => {
+                self.state.hl = u8s_to_u16(&self.memory.get(self.state.hl), &p2);
+            }
+            0xC3 => {
+                self.state.pc = u8s_to_u16(&p1, &p2);
+            }
             _ => {
                 panic!("unimplemented opcode: {:#X}", opcode);
             }
         };
     }
+    fn next_opcode(&mut self) -> u8 {
+        let opcode = self.memory.get(self.state.pc);
+        self.state.pc += 0x1;
+        return opcode;
+    }
 }
 
 fn main() {
@@ -121,8 +140,16 @@ fn main() {
         state: State::default(),
     };
     loop {
-        let op = cpu.memory.get(cpu.state.pc);
+        cpu.exec_next();
-        cpu.state.pc += 1;
-        cpu.execute(op);
     }
 }
+
+fn u8s_to_u16(p1: &u8, p2: &u8) -> u16 {
+    ((*p1 as u16) << 8) | *p2 as u16
+}
+
+fn u16_to_u8s(p: &u16) -> (u8, u8) {
+    let p1 = *p as u8;
+    let p2 = (*p >> 8) as u8;
+    (p1, p2)
+}