From 2afe427ab382b18135d57c5a1414d6d6a3eaa1a2 Mon Sep 17 00:00:00 2001
From: Max Kellermann <max.kellermann@gmail.com>
Date: Mon, 8 Aug 2022 19:20:52 +0200
Subject: [PATCH] output/httpd: copy from returned encoder buffer

This fixes a regression from commits c266fb77581 and 00b8ced09f6,
but really caused by API change in commit 7e14f8f8300f, and this
plugin's failure to adapt to this API change.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1585
---
 src/output/plugins/httpd/HttpdOutputPlugin.cxx | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/output/plugins/httpd/HttpdOutputPlugin.cxx b/src/output/plugins/httpd/HttpdOutputPlugin.cxx
index ed35c1934..fa88bdda3 100644
--- a/src/output/plugins/httpd/HttpdOutputPlugin.cxx
+++ b/src/output/plugins/httpd/HttpdOutputPlugin.cxx
@@ -161,12 +161,21 @@ HttpdOutput::ReadPage() noexcept
 
 	size_t size = 0;
 	do {
-		const auto r = encoder->Read(std::span{buffer}.subspan(size));
+		const auto b = std::span{buffer}.subspan(size);
+		const auto r = encoder->Read(b);
 		if (r.empty())
 			break;
 
 		unflushed_input = 0;
 
+		if (r.data() != b.data()) {
+			/* if the encoder did not write to the given
+			   buffer but instead returned its own buffer,
+			   we need to copy it so we have a contiguous
+			   buffer */
+			std::copy(r.begin(), r.end(), b.begin());
+		}
+
 		size += r.size();
 	} while (size < sizeof(buffer));