Randomize SRAM when first created

src/emulator.rs

@@ -16,6 +16,7 @@ use anyhow::Result;
 use atomic::Atomic;
 use bytemuck::NoUninit;
 use egui_notify::Toast;
+use rand::Rng;
 use tracing::{error, warn};
 
 use crate::{
@@ -78,10 +79,21 @@ impl Cart {
             .create(true)
             .truncate(false)
             .open(sram_path(rom_path, sim_id))?;
-        sram_file.set_len(8 * 1024)?;
 
-        let mut sram = vec![];
-        sram_file.read_to_end(&mut sram)?;
+        let sram = if sram_file.metadata()?.len() == 0 {
+            // new SRAM file, randomize the contents
+            let mut sram = vec![0; 8 * 1024];
+            let mut rng = rand::rng();
+            for dst in sram.iter_mut().step_by(2) {
+                *dst = rng.random();
+            }
+            sram
+        } else {
+            let mut sram = Vec::with_capacity(8 * 1024);
+            sram_file.read_to_end(&mut sram)?;
+            sram
+        };
+
         Ok(Cart {
             rom_path: rom_path.to_path_buf(),
             rom,