From 1e6d280b9bbbb249517c8bfbc9b3a811d58452f0 Mon Sep 17 00:00:00 2001
From: Ze-Zheng Wu <zezhengwu@proton.me>
Date: Sat, 22 Jun 2024 12:00:44 +0800
Subject: [PATCH] fix: out-of-bounds access of code units

---
 src/playground/utils.ts | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/playground/utils.ts b/src/playground/utils.ts
index 0d19e48cf..3e0804384 100644
--- a/src/playground/utils.ts
+++ b/src/playground/utils.ts
@@ -315,7 +315,7 @@ function getUtf8ByteLength(codeUnit: string) {
 	if (code < 65536) {
 		return 3;
 	}
-	throw `Bad UTF-16 code unit: ${codeUnit}`;
+	throw new Error(`Bad UTF-16 code unit "${codeUnit}" with code ${code}`);
 }
 
 /**
@@ -333,7 +333,7 @@ export function spanInBytesToSpanInCodeUnits(
 
 	// Scan through the string, looking for the start of the substring
 	let bytePos = 0;
-	while (bytePos < startInBytes) {
+	while (bytePos < startInBytes && currCodeUnitIndex < str.length) {
 		const byteLength = getUtf8ByteLength(str.charAt(currCodeUnitIndex));
 		bytePos += byteLength;
 		++currCodeUnitIndex;
@@ -348,7 +348,7 @@ export function spanInBytesToSpanInCodeUnits(
 	spanInCodeUnits[0] = currCodeUnitIndex;
 
 	// Now scan through the following string to find the end
-	while (bytePos < endInBytes) {
+	while (bytePos < endInBytes && currCodeUnitIndex < str.length) {
 		const byteLength = getUtf8ByteLength(str.charAt(currCodeUnitIndex));
 		bytePos += byteLength;
 		++currCodeUnitIndex;