From d7212624b099b9f4e39b39ac9189cdb5613ef5b3 Mon Sep 17 00:00:00 2001
From: Max Kellermann <max.kellermann@gmail.com>
Date: Wed, 29 Jan 2025 12:54:42 +0100
Subject: [PATCH] input/{async,thread}: clear the CircularBuffer when it
 becomes empty

First step towards fixing https://github.com/MusicPlayerDaemon/MPD/issues/2186
---
 src/input/AsyncInputStream.cxx  | 6 ++++++
 src/input/ThreadInputStream.cxx | 8 ++++++++
 2 files changed, 14 insertions(+)

diff --git a/src/input/AsyncInputStream.cxx b/src/input/AsyncInputStream.cxx
index ec59680df..da41d3989 100644
--- a/src/input/AsyncInputStream.cxx
+++ b/src/input/AsyncInputStream.cxx
@@ -200,6 +200,12 @@ AsyncInputStream::Read(std::unique_lock<Mutex> &lock,
 	memcpy(ptr, r.data, nbytes);
 	buffer.Consume(nbytes);
 
+	if (buffer.empty())
+		/* when the buffer becomes empty, reset its head and
+		   tail so the next write can fill the whole buffer
+		   and not just the part after the tail */
+		buffer.Clear();
+
 	offset += (offset_type)nbytes;
 
 	if (paused && buffer.GetSize() < resume_at)
diff --git a/src/input/ThreadInputStream.cxx b/src/input/ThreadInputStream.cxx
index de9bae5ae..382ec8fdc 100644
--- a/src/input/ThreadInputStream.cxx
+++ b/src/input/ThreadInputStream.cxx
@@ -146,6 +146,14 @@ ThreadInputStream::Read(std::unique_lock<Mutex> &lock,
 			size_t nbytes = std::min(read_size, r.size);
 			memcpy(ptr, r.data, nbytes);
 			buffer.Consume(nbytes);
+
+			if (buffer.empty())
+				/* when the buffer becomes empty,
+				   reset its head and tail so the next
+				   write can fill the whole buffer and
+				   not just the part after the tail */
+				buffer.Clear();
+
 			wake_cond.notify_all();
 			offset += nbytes;
 			return nbytes;