From 3e3d8c7f9d095daac987a9688b1917e556ae8649 Mon Sep 17 00:00:00 2001
From: Max Kellermann <max@musicpd.org>
Date: Fri, 2 Aug 2019 22:18:45 +0200
Subject: [PATCH] decoder/mad: pad the input buffer with zero bytes and end of
 file

libmad requires padding the input buffer with "MAD_BUFFER_GUARD" zero
bytes at the end of the file, or else it is unable to decode the last
frame.

This fixes yet another bug which prevented this plugin from decoding
the last frame, see
https://github.com/MusicPlayerDaemon/MPD/issues/601
---
 src/decoder/plugins/MadDecoderPlugin.cxx | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/decoder/plugins/MadDecoderPlugin.cxx b/src/decoder/plugins/MadDecoderPlugin.cxx
index 33a9be644..626fec855 100644
--- a/src/decoder/plugins/MadDecoderPlugin.cxx
+++ b/src/decoder/plugins/MadDecoderPlugin.cxx
@@ -132,6 +132,14 @@ class MadDecoder {
 	bool found_replay_gain = false;
 	bool found_first_frame = false;
 	bool decoded_first_frame = false;
+
+	/**
+	 * If this flag is true, then end-of-file was seen and a
+	 * padding of 8 zero bytes were appended to #input_buffer, to
+	 * allow libmad to decode the last frame.
+	 */
+	bool was_eof = false;
+
 	DecoderClient *const client;
 	InputStream &input_stream;
 	enum mad_layer layer = mad_layer(0);
@@ -247,7 +255,12 @@ MadDecoder::FillBuffer() noexcept
 	size_t nbytes = decoder_read(client, input_stream,
 				     dest, max_read_size);
 	if (nbytes == 0) {
-		return false;
+		if (was_eof || max_read_size < MAD_BUFFER_GUARD)
+			return false;
+
+		was_eof = true;
+		nbytes = MAD_BUFFER_GUARD;
+		memset(dest, 0, nbytes);
 	}
 
 	mad_stream_buffer(&stream, input_buffer, rest_size + nbytes);
@@ -922,6 +935,7 @@ MadDecoder::Read() noexcept
 			if (j < highest_frame) {
 				if (Seek(frame_offsets[j])) {
 					current_frame = j;
+					was_eof = false;
 					client->CommandFinished();
 				} else
 					client->SeekError();