reading and writing words at addresses

src/emulator/structs.rs

@@ -23,20 +23,32 @@ pub struct EmulatorState {
 }
 
 impl EmulatorState {
-    // Get the next byte from memory
+    // Read the next byte from memory pointed at by PC
     pub fn next_byte(&mut self) -> u8 {
         self.pc += 1;
         self.memory[self.pc as usize]
     }
 
-    // Get the next 16-bit word from memory, in little endian order
+    // Read the next 16-bit word from memory pointed at by PC, in little endian order
     pub fn next_word(&mut self) -> u16 {
         self.pc += 2;
+        self.read_word(self.pc - 1)
+    }
+
+    // Read a 16-bit word at a specific address
+    pub fn read_word(&mut self, address: u16) -> u16 {
         u16::from_le_bytes([
-            self.memory[self.pc as usize - 1],
-            self.memory[self.pc as usize],
+            self.memory[address as usize],
+            self.memory[address as usize + 1],
         ])
     }
+
+    // Write a 16-bit word at a specific address
+    pub fn write_word(&mut self, address: u16, value: u16) {
+        let [low, high] = u16::to_le_bytes(value);
+        self.memory[address as usize] = low;
+        self.memory[address as usize + 1] = high;
+    }
 }
 
 #[derive(Clone, Copy, PartialEq, Eq, Debug)]