Add basic memory for load instruction backing

src/lib.rs

@@ -1,4 +1,5 @@
 #![warn(clippy::all, clippy::pedantic)]
 
+mod memory;
 mod register;
 mod run;

src/memory.rs

@@ -0,0 +1,64 @@
+const MAX_MEMORY_ADDRESS: usize = 0xFFFF;
+
+/// `Memory` is an abstraction over the Gameboy's memory space.
+///
+/// In its current state, this implementation ignores literally all properties.
+/// of the Gameboy's memory, and should not be relied upon for anything other than development
+#[derive(Debug, Clone)]
+struct Memory {
+    data: [u8; MAX_MEMORY_ADDRESS],
+}
+
+impl Memory {
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    pub fn get(&self, index: usize) -> Option<u8> {
+        self.data.get(index).copied()
+    }
+
+    pub fn set(&mut self, index: usize, value: u8) -> Option<u8> {
+        let val_ref = self.data.get_mut(index)?;
+        *val_ref = value;
+
+        Some(*val_ref)
+    }
+}
+
+impl Default for Memory {
+    fn default() -> Self {
+        Self {
+            data: [0_u8; MAX_MEMORY_ADDRESS],
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_get_set_valid_address() {
+        let mut memory = Memory::new();
+        let set_val = memory.set(0xCCCC, 100);
+        assert_eq!(Some(100), set_val);
+
+        let get_val = memory.get(0xCCCC);
+        assert_eq!(Some(100), get_val);
+    }
+
+    #[test]
+    fn test_get_invalid_address() {
+        let memory = Memory::new();
+        let get_val = memory.get(0xCC_CC_CC_CC_CC);
+        assert_eq!(None, get_val);
+    }
+
+    #[test]
+    fn test_set_invalid_address() {
+        let mut memory = Memory::new();
+        let set_val = memory.set(0xCC_CC_CC_CC_CC, 100);
+        assert_eq!(None, set_val);
+    }
+}