From d09441ca03e399fe641da88624c8ea0476967187 Mon Sep 17 00:00:00 2001
From: Jameson Nash <vtjnash@gmail.com>
Date: Thu, 13 Jul 2023 12:22:07 -0400
Subject: [PATCH] fs: fix WTF-8 decoding issue (#4092)

We forgot to mask off the high bits from the first byte, so we ended up
always failing the subsequent range check.

Refs: #2970
Fixes: https://github.com/nodejs/node/issues/48673
---
 src/win/fs.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/win/fs.c b/src/win/fs.c
index fc209c54..4fc13b04 100644
--- a/src/win/fs.c
+++ b/src/win/fs.c
@@ -176,9 +176,11 @@ static int32_t fs__decode_wtf8_char(const char** input) {
   if ((b4 & 0xC0) != 0x80)
     return -1; /* invalid: not a continuation byte */
   code_point = (code_point << 6) | (b4 & 0x3F);
-  if (b1 <= 0xF4)
+  if (b1 <= 0xF4) {
+    code_point &= 0x1FFFFF;
     if (code_point <= 0x10FFFF)
       return code_point; /* four-byte character */
+  }
 
   /* code point too large */
   return -1;