implement rom loading

Cargo.lock

@@ -6,6 +6,7 @@ version = 3
 name = "Chip8Emulator"
 version = "0.1.0"
 dependencies = [
+ "anyhow",
  "env_logger",
  "log",
 ]
@@ -68,6 +69,12 @@ dependencies = [
  "windows-sys",
 ]
 
+[[package]]
+name = "anyhow"
+version = "1.0.93"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4c95c10ba0b00a02636238b814946408b1322d5ac4760326e6fb8ec956d85775"
+
 [[package]]
 name = "colorchoice"
 version = "1.0.3"

Cargo.toml

@@ -6,3 +6,4 @@ edition = "2021"
 [dependencies]
 log = "0.4.22"
 env_logger = "0.11.5"
+anyhow = "1.0.93"

src/emulator.rs

@@ -1,17 +1,31 @@
+use anyhow::anyhow;
 use log::{debug, info};
+use std::fs::File;
+use std::io::Read;
+use std::path::Path;
 
+const MEMORY_SIZE: usize = 4096;
+const NUMBER_OF_REGISTERS: usize = 16;
+
+/// Emulator emulates the Chip8 CPU.
 pub struct Emulator {
-    memory: [u8; 4096]
+    memory: [u8; MEMORY_SIZE],
+    registers: [u16; NUMBER_OF_REGISTERS],
+    program_counter: u16,
 }
 
 impl Emulator {
+    /// Creates a new `Emulator` instance.
+    ///
     pub fn new() -> Emulator {
         let mut emulator = Emulator {
             memory: [0; 4096],
+            registers: [0; 16],
+            program_counter: 0,
         };
-        
+
         emulator.load_font_data();
-        
+
         emulator
     }
 
@@ -33,12 +47,45 @@ impl Emulator {
             0xF0, 0x80, 0x80, 0x80, 0xF0, // C
             0xE0, 0x90, 0x90, 0x90, 0xE0, // D
             0xF0, 0x80, 0xF0, 0x80, 0xF0, // E
-            0xF0, 0x80, 0xF0, 0x80, 0x80  // F
+            0xF0, 0x80, 0xF0, 0x80, 0x80, // F
         ];
-        FONT_SPRITES.iter().enumerate().for_each(|i| {
-            self.memory[0xf0 + i.0] = *i.1
-        });
+        FONT_SPRITES
+            .iter()
+            .enumerate()
+            .for_each(|i| self.memory[0xf0 + i.0] = *i.1);
         info!("Loaded font data...");
         debug!("Memory:\n{}\n", format!("{:?}", self.memory))
     }
-}
+
+    /// Emulates the ROM specified at `path`.
+    pub fn emulate<T>(&mut self, path: T) -> Result<(), anyhow::Error>
+    where
+        T: AsRef<Path> + std::fmt::Display,
+    {
+        self.load_rom(path)?;
+
+        Ok(())
+    }
+
+    /// Loads the ROM found at the rom path in the emulator's RAM memory.
+    fn load_rom<T>(&mut self, rom_file: T) -> Result<(), anyhow::Error>
+    where
+        T: AsRef<Path> + std::fmt::Display,
+    {
+        let mut file = File::open(&rom_file)?;
+
+        // Check ROM length if it overflows max RAM size.
+        let rom_size = file.metadata()?.len();
+        debug!("Open ROM {} of size {} bytes.", &rom_file, rom_size);
+        if rom_size > MEMORY_SIZE as u64 - 0x200 {
+            return Err(anyhow!(
+                "ROM at {} overflows emulator's RAM size of 4kB.",
+                &rom_file
+            ));
+        }
+        file.read(&mut self.memory[0x200..])?;
+
+        debug!("Memory:\n{}\n", format!("{:?}", self.memory));
+        Ok(())
+    }
+}

src/main.rs

@@ -3,8 +3,12 @@ use env_logger;
 
 mod emulator;
 
-fn main() {
+fn main() -> Result<(), anyhow::Error> {
     env_logger::init();
 
-    let emulator = Emulator::new();
+    let mut emulator = Emulator::new();
+
+    emulator.emulate(String::from("./roms/ibm-logo.ch8"))?;
+
+    Ok(())
 }