From 767fb01a8cf54f0760e5bbf408eb89d67239575d Mon Sep 17 00:00:00 2001
From: Tim Schumacher <timschumi@gmx.de>
Date: Tue, 4 Apr 2023 18:29:43 +0200
Subject: [PATCH] AK: Report copied bytes when seekback copying from
 CircularBuffer

Otherwise, we have no way of determining whether our copy was truncated
by accident.
---
 AK/CircularBuffer.cpp | 9 +++++----
 AK/CircularBuffer.h   | 2 +-
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/AK/CircularBuffer.cpp b/AK/CircularBuffer.cpp
index 6d8aa4d742c..884bad0f345 100644
--- a/AK/CircularBuffer.cpp
+++ b/AK/CircularBuffer.cpp
@@ -206,20 +206,21 @@ ErrorOr<size_t> CircularBuffer::fill_from_stream(Stream& stream)
     return bytes.size();
 }
 
-ErrorOr<void> CircularBuffer::copy_from_seekback(size_t distance, size_t length)
+ErrorOr<size_t> CircularBuffer::copy_from_seekback(size_t distance, size_t length)
 {
     if (distance > m_seekback_limit)
         return Error::from_string_literal("Tried a seekback copy beyond the seekback limit");
 
-    while (length > 0) {
+    auto remaining_length = length;
+    while (remaining_length > 0) {
         auto next_span = next_read_span_with_seekback(distance);
         if (next_span.size() == 0)
             break;
 
-        length -= write(next_span.trim(length));
+        remaining_length -= write(next_span.trim(remaining_length));
     }
 
-    return {};
+    return length - remaining_length;
 }
 
 }
diff --git a/AK/CircularBuffer.h b/AK/CircularBuffer.h
index be23b791e47..89861d02151 100644
--- a/AK/CircularBuffer.h
+++ b/AK/CircularBuffer.h
@@ -33,7 +33,7 @@ public:
     /// before the current write pointer and allows for reading already-read data.
     ErrorOr<Bytes> read_with_seekback(Bytes bytes, size_t distance);
 
-    ErrorOr<void> copy_from_seekback(size_t distance, size_t length);
+    ErrorOr<size_t> copy_from_seekback(size_t distance, size_t length);
 
     [[nodiscard]] size_t empty_space() const;
     [[nodiscard]] size_t used_space() const;