From d12036132e62902a0158aea940890276029c5d98 Mon Sep 17 00:00:00 2001
From: Tim Schumacher <timschumi@gmx.de>
Date: Thu, 1 Jun 2023 23:39:05 +0200
Subject: [PATCH] AK: Allow passing an offset to
 `CircularBuffer::next_read_span()`

---
 AK/CircularBuffer.cpp | 15 +++++++++++++--
 AK/CircularBuffer.h   |  2 +-
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/AK/CircularBuffer.cpp b/AK/CircularBuffer.cpp
index dc42c8bd516..dbb57fc495d 100644
--- a/AK/CircularBuffer.cpp
+++ b/AK/CircularBuffer.cpp
@@ -97,9 +97,20 @@ Bytes CircularBuffer::next_write_span()
     return m_buffer.span().slice(m_reading_head + m_used_space, capacity() - (m_reading_head + m_used_space));
 }
 
-ReadonlyBytes CircularBuffer::next_read_span() const
+ReadonlyBytes CircularBuffer::next_read_span(size_t offset) const
 {
-    return m_buffer.span().slice(m_reading_head, min(capacity() - m_reading_head, m_used_space));
+    auto reading_head = m_reading_head;
+    auto used_space = m_used_space;
+
+    if (offset > 0) {
+        if (offset >= used_space)
+            return Bytes {};
+
+        reading_head = (reading_head + offset) % capacity();
+        used_space -= offset;
+    }
+
+    return m_buffer.span().slice(reading_head, min(capacity() - reading_head, used_space));
 }
 
 ReadonlyBytes CircularBuffer::next_read_span_with_seekback(size_t distance) const
diff --git a/AK/CircularBuffer.h b/AK/CircularBuffer.h
index 11ba360c9c6..962e2a19c9b 100644
--- a/AK/CircularBuffer.h
+++ b/AK/CircularBuffer.h
@@ -50,7 +50,7 @@ protected:
     [[nodiscard]] bool is_wrapping_around() const;
 
     [[nodiscard]] Bytes next_write_span();
-    [[nodiscard]] ReadonlyBytes next_read_span() const;
+    [[nodiscard]] ReadonlyBytes next_read_span(size_t offset = 0) const;
     [[nodiscard]] ReadonlyBytes next_read_span_with_seekback(size_t distance) const;
 
     ByteBuffer m_buffer {};