From f1cdbb4279b26c4b17ba61f49cd7eb7d7c59c263 Mon Sep 17 00:00:00 2001
From: Folkert <folkert@folkertdev.nl>
Date: Mon, 23 Oct 2023 19:08:57 +0200
Subject: [PATCH] fix JS bitwise math

---
 www/public/repl/repl.js | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/www/public/repl/repl.js b/www/public/repl/repl.js
index 0b35edee73a..c688e21833e 100644
--- a/www/public/repl/repl.js
+++ b/www/public/repl/repl.js
@@ -176,7 +176,10 @@ function send_panic_msg_to_js(rocstr_ptr, panic_tag) {
     let stringBytes = "";
     if (finalByte < 0) {
         // small string
-        const length = finalByte ^ 0b1000_0000;
+
+        // bitwise ops on negative JS numbers are weird. This clears the bit that we
+        // use to indicate a small string. In rust it's `finalByte as u8 ^ 0b1000_0000`
+        const length = finalByte + 128;
         stringBytes = new Uint8Array(memory.buffer, rocstr_ptr, length);
     } else {
         // big string