Small refactor and define rom trait

snes-core/src/rom/lo_rom.rs

@@ -0,0 +1,28 @@
+use super::{ROM, load_rom};
+
+pub struct LoROM {
+    data: Vec<u8>,
+}
+
+impl LoROM {
+    pub fn new() -> Self {
+        Self {
+            data: vec![],
+        }
+    }
+}
+
+impl ROM for LoROM {
+    fn load(&mut self, filename: &String) -> std::io::Result<bool> {
+        load_rom(filename, &mut self.data)
+    }
+
+    fn read(&self, address: u32) -> u8 {
+        match self.data.get(address as usize) {
+            Some(byte) => *byte,
+            None => 0xFF,
+        }
+    }
+
+    fn write(&mut self, _address: u32, _value: u8) {}
+}

snes-core/src/rom/mod.rs

@@ -0,0 +1,17 @@
+pub mod lo_rom;
+
+use std::fs::File;
+use std::io::Read;
+
+pub fn load_rom(filename: &String, target: &mut Vec<u8>) -> std::io::Result<bool> {
+    let mut file = File::open(filename)?;
+    file.read_to_end(target)?;
+    // TODO: header checksum here
+    Ok(true)
+}
+
+pub trait ROM {
+    fn load(&mut self, filename: &String) -> std::io::Result<bool>;
+    fn read(&self, address: u32) -> u8;
+    fn write(&mut self, address: u32, value: u8);
+}