From 56d861ebe0353df4b3a12a51dc1f103e12292f34 Mon Sep 17 00:00:00 2001
From: Tim Schumacher <timschumi@gmx.de>
Date: Thu, 27 Apr 2023 11:33:08 +0200
Subject: [PATCH] AK: Prevent bit counter underflows in the new BitStream

Our current `peek_bits` function allows retrieving more bits than we can
actually provide, so whenever someone discards the requested bit count
afterwards we were underflowing the value instead.
---
 AK/BitStream.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/AK/BitStream.h b/AK/BitStream.h
index 3ddca57267..c03ac22ada 100644
--- a/AK/BitStream.h
+++ b/AK/BitStream.h
@@ -222,6 +222,10 @@ public:
 
     ALWAYS_INLINE void discard_previously_peeked_bits(u8 count)
     {
+        // We allow "retrieving" more bits than we can provide, but we need to make sure that we don't underflow the current bit counter.
+        if (count > m_bit_count)
+            count = m_bit_count;
+
         m_bit_offset += count;
         m_bit_count -= count;
     }