From 89dfeeeb2d47f50360993057d36048cc2dfa748c Mon Sep 17 00:00:00 2001
From: Simon Gellis <simongellis@gmail.com>
Date: Sun, 3 Aug 2025 18:42:19 -0400
Subject: [PATCH] Randomize SRAM when first created

---
 Cargo.lock      |  1 +
 Cargo.toml      |  1 +
 src/emulator.rs | 18 +++++++++++++++---
 3 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index af16434..398d7ac 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1842,6 +1842,7 @@ dependencies = [
  "num-traits",
  "oneshot",
  "pollster",
+ "rand 0.9.2",
  "rfd",
  "rtrb",
  "rubato",
diff --git a/Cargo.toml b/Cargo.toml
index 7e66489..022d750 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -30,6 +30,7 @@ num-derive = "0.4"
 num-traits = "0.2"
 oneshot = "0.1"
 pollster = "0.4"
+rand = "0.9"
 rfd = { version = "0.15", default-features = false, features = ["xdg-portal", "async-std"]}
 rtrb = "0.3"
 rubato = "0.16"
diff --git a/src/emulator.rs b/src/emulator.rs
index 9c55d06..55019ec 100644
--- a/src/emulator.rs
+++ b/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,