release v0.22.3

Pass a std::string to PathTraitsUTF8::Relative(), implicitly casting
it to std::string_view.  This selects the right overload which returns
std::string_view instead of `const char *`; the latter could return
`nullptr` which would cause the implicit conversion of the return
value to std::string_view to crash.

Regression caused by commits ead208987d and a98d627c0b.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/995

NEWS

@@ -1,3 +1,24 @@
+ver 0.22.3 (2020/11/06)
+* playlist
+  - add option "as_directory", making CUE file expansion optional
+* storage
+  - curl: fix crash bug
+* filter
+  - fix garbage after "Audio format not supported by filter" message
+  - ffmpeg: support planar output
+  - ffmpeg: support sample formats other than 16 bit
+
+ver 0.22.2 (2020/10/28)
+* database
+  - simple: purge songs and virtual directories for unavailable plugins
+    on update
+* input
+  - qobuz/tidal: fix protocol errors due to newlines in error messages
+  - smbclient: disable by default due to libsmbclient crash bug
+* playlist
+  - soundcloud: fix protocol errors due to newlines in error messages
+* state_file: save on shutdown
+
 ver 0.22.1 (2020/10/17)
 * decoder
   - opus: apply the OpusHead output gain even if there is no EBU R128 tag

doc/conf.py

@@ -38,7 +38,7 @@ author = 'Max Kellermann'
 # built documents.
 #
 # The short X.Y version.
-version = '0.22.1'
+version = '0.22.3'
 # The full version, including alpha/beta/rc tags.
 release = version
 

doc/plugins.rst

@@ -71,6 +71,11 @@ Load music files from a SMB/CIFS server. It is used when
 :code:`music_directory` contains a ``smb://`` URI, for example
 :samp:`smb://myfileserver/Music`.
 
+Note that :file:`libsmbclient` has a serious bug which causes MPD to
+crash, and therefore this plugin is disabled by default and should not
+be used until the bug is fixed:
+https://bugzilla.samba.org/show_bug.cgi?id=11413
+
 nfs
 ---
 
@@ -1224,23 +1229,25 @@ Playlist plugins
 asx
 ---
 
-Reads .asx playlist files.
+Reads :file:`.asx` playlist files.
+
+.. _cue_playlist:
 
 cue
 ---
-Reads .cue files.
+Reads :file:`.cue` files.
 
 embcue
 ------
-Reads CUE sheets from the "CUESHEET" tag of song files.
+Reads CUE sheets from the ``CUESHEET`` tag of song files.
 
 m3u
 ---
-Reads .m3u playlist files.
+Reads :file:`.m3u` playlist files.
 
 extm3u
 ------
-Reads extended .m3u playlist files.
+Reads extended :file:`.m3u` playlist files.
 
 flac
 ----
@@ -1248,11 +1255,11 @@ Reads the cuesheet metablock from a FLAC file.
 
 pls
 ---
-Reads .pls playlist files.
+Reads :file:`.pls` playlist files.
 
 rss
 ---
-Reads music links from .rss files.
+Reads music links from :file:`.rss` files.
 
 soundcloud
 ----------

doc/user.rst

@@ -86,7 +86,7 @@ For example, the following installs a fairly complete list of build dependencies
       libpulse-dev libshout3-dev \
       libsndio-dev \
       libmpdclient-dev \
-      libnfs-dev libsmbclient-dev \
+      libnfs-dev \
       libupnp-dev \
       libavahi-client-dev \
       libsqlite3-dev \
@@ -413,7 +413,7 @@ The following table lists the audio_output options valid for all plugins:
    * - **format samplerate:bits:channels**
      -  Always open the audio output with the specified audio format, regardless of the format of the input file. This is optional for most plugins.
         See :ref:`audio_output_format` for a detailed description of the value.
-   * - **enabed yes|no**
+   * - **enabled yes|no**
      - Specifies whether this audio output is enabled when :program:`MPD` is started. By default, all audio outputs are enabled. This is just the default setting when there is no state file; with a state file, the previous state is restored.
    * - **tags yes|no**
      - If set to no, then :program:`MPD` will not send tags to this output. This is only useful for output plugins that can receive tags, for example the httpd output plugin.
@@ -500,6 +500,11 @@ The following table lists the playlist_plugin options valid for all plugins:
      - The name of the plugin
    * - **enabled yes|no**
      - Allows you to disable a playlist plugin without recompiling. By default, all plugins are enabled.
+   * - **as_directory yes|no**
+     - With this option, a playlist file of this type is parsed during
+       database update and converted to a virtual directory, allowing
+       MPD clients to access individual entries.  By default, this is
+       only enabled for the :ref:`cue plugin <cue_playlist>`.
 
 More information can be found in the :ref:`playlist_plugins`
 reference.

meson.build

@@ -1,11 +1,11 @@
 project(
   'mpd',
   ['c', 'cpp'],
-  version: '0.22.1',
+  version: '0.22.3',
   meson_version: '>= 0.49.0',
   default_options: [
-    'c_std=c99',
-    'build.c_std=c99',
+    'c_std=c11',
+    'build.c_std=c11',
     'cpp_std=c++17',
     'build.cpp_std=c++17',
     'warning_level=3',
@@ -96,6 +96,11 @@ test_cflags = test_common_flags + [
 ]
 
 test_ldflags = [
+  # make relocations read-only (hardening)
+  '-Wl,-z,relro',
+
+  # no lazy binding, please - not worth it for a daemon
+  '-Wl,-z,now',
 ]
 
 if get_option('buildtype') != 'debug'
@@ -224,7 +229,6 @@ log_dep = declare_dependency(
 sources = [
   version_cxx,
   'src/Main.cxx',
-  'src/protocol/Ack.cxx',
   'src/protocol/ArgParser.cxx',
   'src/protocol/Result.cxx',
   'src/command/CommandError.cxx',

meson_options.txt

@@ -92,7 +92,11 @@ option('cdio_paranoia', type: 'feature', description: 'libcdio_paranoia input pl
 option('curl', type: 'feature', description: 'HTTP client using CURL')
 option('mms', type: 'feature', description: 'MMS protocol support using libmms')
 option('nfs', type: 'feature', description: 'NFS protocol support using libnfs')
-option('smbclient', type: 'feature', description: 'SMB support using libsmbclient')
+
+# The "smbclient" plugin is disabled by default because libsmbclient
+# has a serious bug which crashes MPD very quickly:
+# https://bugzilla.samba.org/show_bug.cgi?id=11413
+option('smbclient', type: 'feature', value: 'disabled', description: 'SMB support using libsmbclient')
 
 #
 # Commercial services

src/Main.cxx

@@ -533,6 +533,9 @@ MainConfigured(const struct options &options, const ConfigData &raw_config)
 
 	/* cleanup */
 
+	if (instance.state_file)
+		instance.state_file->Write();
+
 	instance.BeginShutdownUpdate();
 
 	ZeroconfDeinit();

src/SongUpdate.cxx

@@ -23,6 +23,7 @@
 #include "db/plugins/simple/Directory.hxx"
 #include "storage/StorageInterface.hxx"
 #include "storage/FileInfo.hxx"
+#include "decoder/DecoderList.hxx"
 #include "fs/AllocatedPath.hxx"
 #include "fs/FileInfo.hxx"
 #include "tag/Builder.hxx"
@@ -40,6 +41,14 @@
 
 #ifdef ENABLE_DATABASE
 
+bool
+Song::IsPluginAvailable() const noexcept
+{
+	const char *suffix = GetFilenameSuffix();
+	return suffix != nullptr &&
+		decoder_plugins_supports_suffix(suffix);
+}
+
 SongPtr
 Song::LoadFile(Storage &storage, const char *path_utf8, Directory &parent)
 {

src/db/meson.build

@@ -31,6 +31,7 @@ db_glue_sources = [
   'update/Remove.cxx',
   'update/ExcludeList.cxx',
   'update/VirtualDirectory.cxx',
+  'update/SpecialDirectory.cxx',
   'DatabaseGlue.cxx',
   'Configured.cxx',
   'DatabaseSong.cxx',

src/db/plugins/simple/Directory.hxx

@@ -132,6 +132,14 @@ public:
 		return mounted_database != nullptr;
 	}
 
+	/**
+	 * Checks whether this is a "special" directory
+	 * (e.g. #DEVICE_PLAYLIST) and whether the underlying plugin
+	 * is available.
+	 */
+	gcc_pure
+	bool IsPluginAvailable() const noexcept;
+
 	/**
 	 * Remove this #Directory object from its parent and free it.  This
 	 * must not be called with the root Directory.

src/db/plugins/simple/Song.cxx

@@ -34,6 +34,14 @@ Song::Song(DetachedSong &&other, Directory &_parent) noexcept
 {
 }
 
+const char *
+Song::GetFilenameSuffix() const noexcept
+{
+	return target.empty()
+		? PathTraitsUTF8::GetFilenameSuffix(filename.c_str())
+		: PathTraitsUTF8::GetPathSuffix(target.c_str());
+}
+
 std::string
 Song::GetURI() const noexcept
 {

src/db/plugins/simple/Song.hxx

@@ -108,6 +108,16 @@ struct Song {
 
 	Song(DetachedSong &&other, Directory &_parent) noexcept;
 
+	gcc_pure
+	const char *GetFilenameSuffix() const noexcept;
+
+	/**
+	 * Checks whether the decoder plugin for this song is
+	 * available.
+	 */
+	gcc_pure
+	bool IsPluginAvailable() const noexcept;
+
 	/**
 	 * allocate a new song structure with a local file name and attempt to
 	 * load its metadata.  If all decoder plugin fail to read its meta

src/db/update/Playlist.cxx

@@ -95,7 +95,7 @@ UpdateWalk::UpdatePlaylistFile(Directory &directory,
 	if (plugin == nullptr)
 		return false;
 
-	if (plugin->as_folder)
+	if (GetPlaylistPluginAsFolder(*plugin))
 		UpdatePlaylistFile(directory, name, info, *plugin);
 
 	PlaylistInfo pi(name, info.mtime);

src/db/update/SpecialDirectory.cxx

@@ -0,0 +1,83 @@
+/*
+ * Copyright 2003-2020 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "db/plugins/simple/Directory.hxx"
+#include "archive/ArchiveList.hxx"
+#include "decoder/DecoderList.hxx"
+#include "playlist/PlaylistRegistry.hxx"
+#include "fs/Traits.hxx"
+
+gcc_pure
+static bool
+HaveArchivePluginForFilename(const char *filename) noexcept
+{
+#ifdef ENABLE_ARCHIVE
+	const char *suffix = PathTraitsUTF8::GetFilenameSuffix(filename);
+	return suffix != nullptr &&
+		archive_plugin_from_suffix(suffix) != nullptr;
+#else
+	(void)filename;
+	return false;
+#endif
+}
+
+gcc_pure
+static bool
+HaveContainerPluginForFilename(const char *filename) noexcept
+{
+	const char *suffix = PathTraitsUTF8::GetFilenameSuffix(filename);
+	return suffix != nullptr &&
+		// TODO: check if this plugin really supports containers
+		decoder_plugins_supports_suffix(suffix);
+}
+
+gcc_pure
+static bool
+HavePlaylistPluginForFilename(const char *filename) noexcept
+{
+	const char *suffix = PathTraitsUTF8::GetFilenameSuffix(filename);
+	if (suffix == nullptr)
+		return false;
+
+	const auto plugin = FindPlaylistPluginBySuffix(suffix);
+	if (plugin == nullptr)
+		return false;
+
+	/* discard the special directory if the user disables the
+	   plugin's "as_directory" setting */
+	return GetPlaylistPluginAsFolder(*plugin);
+}
+
+bool
+Directory::IsPluginAvailable() const noexcept
+{
+	switch (device) {
+	case DEVICE_INARCHIVE:
+		return HaveArchivePluginForFilename(GetName());
+
+	case DEVICE_CONTAINER:
+		return HaveContainerPluginForFilename(GetName());
+
+	case DEVICE_PLAYLIST:
+		return HavePlaylistPluginForFilename(GetName());
+
+	default:
+		return true;
+	}
+}

src/db/update/Walk.cxx

@@ -69,46 +69,58 @@ UpdateWalk::RemoveExcludedFromDirectory(Directory &directory,
 	const ScopeDatabaseLock protect;
 
 	directory.ForEachChildSafe([&](Directory &child){
-			const auto name_fs =
-				AllocatedPath::FromUTF8(child.GetName());
+		const auto name_fs =
+			AllocatedPath::FromUTF8(child.GetName());
 
-			if (name_fs.IsNull() || exclude_list.Check(name_fs)) {
-				editor.DeleteDirectory(&child);
-				modified = true;
-			}
-		});
+		if (name_fs.IsNull() || exclude_list.Check(name_fs)) {
+			editor.DeleteDirectory(&child);
+			modified = true;
+		}
+	});
 
 	directory.ForEachSongSafe([&](Song &song){
-			assert(&song.parent == &directory);
+		assert(&song.parent == &directory);
 
-			const auto name_fs = AllocatedPath::FromUTF8(song.filename);
-			if (name_fs.IsNull() || exclude_list.Check(name_fs)) {
-				editor.DeleteSong(directory, &song);
-				modified = true;
-			}
-		});
+		const auto name_fs = AllocatedPath::FromUTF8(song.filename);
+		if (name_fs.IsNull() || exclude_list.Check(name_fs)) {
+			editor.DeleteSong(directory, &song);
+			modified = true;
+		}
+	});
 }
 
 inline void
 UpdateWalk::PurgeDeletedFromDirectory(Directory &directory) noexcept
 {
 	directory.ForEachChildSafe([&](Directory &child){
-			if (child.IsMount() || DirectoryExists(storage, child))
-				return;
+		if (child.IsMount())
+			/* mount points are always preserved */
+			return;
 
-			editor.LockDeleteDirectory(&child);
+		if (DirectoryExists(storage, child) &&
+		    child.IsPluginAvailable())
+			return;
 
-			modified = true;
-		});
+		/* the directory was deleted (or the plugin which
+		   handles this "virtual" directory is unavailable) */
+
+		editor.LockDeleteDirectory(&child);
+
+		modified = true;
+	});
 
 	directory.ForEachSongSafe([&](Song &song){
-			if (!directory_child_is_regular(storage, directory,
-							song.filename)) {
-				editor.LockDeleteSong(directory, &song);
+		if (!directory_child_is_regular(storage, directory,
+						song.filename) ||
+		    !song.IsPluginAvailable()) {
+			/* the song file was deleted (or the decoder
+			   plugin is unavailable) */
 
-				modified = true;
-			}
-		});
+			editor.LockDeleteSong(directory, &song);
+
+			modified = true;
+		}
+	});
 
 	for (auto i = directory.playlists.begin(),
 		     end = directory.playlists.end();

src/decoder/plugins/FfmpegDecoderPlugin.cxx

@@ -25,6 +25,7 @@
 #include "lib/ffmpeg/Domain.hxx"
 #include "lib/ffmpeg/Error.hxx"
 #include "lib/ffmpeg/Init.hxx"
+#include "lib/ffmpeg/Interleave.hxx"
 #include "lib/ffmpeg/Buffer.hxx"
 #include "lib/ffmpeg/Frame.hxx"
 #include "lib/ffmpeg/Format.hxx"
@@ -176,48 +177,6 @@ start_time_fallback(const AVStream &stream)
 	return FfmpegTimestampFallback(stream.start_time, 0);
 }
 
-/**
- * Copy PCM data from a non-empty AVFrame to an interleaved buffer.
- *
- * Throws #std::exception on error.
- */
-static ConstBuffer<void>
-copy_interleave_frame(const AVCodecContext &codec_context,
-		      const AVFrame &frame,
-		      FfmpegBuffer &global_buffer)
-{
-	assert(frame.nb_samples > 0);
-
-	int plane_size;
-	const int data_size =
-		av_samples_get_buffer_size(&plane_size,
-					   codec_context.channels,
-					   frame.nb_samples,
-					   codec_context.sample_fmt, 1);
-	assert(data_size != 0);
-	if (data_size < 0)
-		throw MakeFfmpegError(data_size);
-
-	void *output_buffer;
-	if (av_sample_fmt_is_planar(codec_context.sample_fmt) &&
-	    codec_context.channels > 1) {
-		output_buffer = global_buffer.GetT<uint8_t>(data_size);
-		if (output_buffer == nullptr)
-			/* Not enough memory - shouldn't happen */
-			throw std::bad_alloc();
-
-		PcmInterleave(output_buffer,
-			      ConstBuffer<const void *>((const void *const*)frame.extended_data,
-							codec_context.channels),
-			      frame.nb_samples,
-			      av_get_bytes_per_sample(codec_context.sample_fmt));
-	} else {
-		output_buffer = frame.extended_data[0];
-	}
-
-	return { output_buffer, (size_t)data_size };
-}
-
 /**
  * Convert AVPacket::pts to a stream-relative time stamp (still in
  * AVStream::time_base units).  Returns a negative value on error.
@@ -258,7 +217,7 @@ FfmpegSendFrame(DecoderClient &client, InputStream *is,
 		FfmpegBuffer &buffer)
 {
 	ConstBuffer<void> output_buffer =
-		copy_interleave_frame(codec_context, frame, buffer);
+		Ffmpeg::InterleaveFrame(frame, buffer);
 
 	if (skip_bytes > 0) {
 		if (skip_bytes >= output_buffer.size) {

src/filter/LoadChain.cxx

@@ -20,19 +20,24 @@
 #include "LoadChain.hxx"
 #include "Factory.hxx"
 #include "Prepared.hxx"
+#include "plugins/AutoConvertFilterPlugin.hxx"
 #include "plugins/ChainFilterPlugin.hxx"
+#include "util/IterableSplitString.hxx"
 
-#include <algorithm>
 #include <string>
 
-#include <string.h>
-
 static void
 filter_chain_append_new(PreparedFilter &chain, FilterFactory &factory,
-			const char *template_name)
+			std::string_view template_name)
 {
+	/* using the AutoConvert filter just in case the specified
+	   filter plugin does not support the exact input format */
+
 	filter_chain_append(chain, template_name,
-			    factory.MakeFilter(template_name));
+			    /* unfortunately, MakeFilter() wants a
+			       null-terminated string, so we need to
+			       copy it here */
+			    autoconvert_filter_new(factory.MakeFilter(std::string(template_name).c_str())));
 }
 
 void
@@ -40,18 +45,10 @@ filter_chain_parse(PreparedFilter &chain,
 		   FilterFactory &factory,
 		   const char *spec)
 {
-	const char *const end = spec + strlen(spec);
+	for (const std::string_view i : IterableSplitString(spec, ',')) {
+		if (i.empty())
+			continue;
 
-	while (true) {
-		const char *comma = std::find(spec, end, ',');
-		if (comma > spec) {
-			const std::string name(spec, comma);
-			filter_chain_append_new(chain, factory, name.c_str());
-		}
-
-		if (comma == end)
-			break;
-
-		spec = comma + 1;
+		filter_chain_append_new(chain, factory, i);
 	}
 }

src/filter/plugins/AutoConvertFilterPlugin.cxx

@@ -19,6 +19,7 @@
 
 #include "AutoConvertFilterPlugin.hxx"
 #include "ConvertFilterPlugin.hxx"
+#include "TwoFilters.hxx"
 #include "filter/Filter.hxx"
 #include "filter/Prepared.hxx"
 #include "pcm/AudioFormat.hxx"
@@ -27,35 +28,6 @@
 #include <cassert>
 #include <memory>
 
-class AutoConvertFilter final : public Filter {
-	/**
-	 * The underlying filter.
-	 */
-	std::unique_ptr<Filter> filter;
-
-	/**
-	 * A convert_filter, just in case conversion is needed.  nullptr
-	 * if unused.
-	 */
-	std::unique_ptr<Filter> convert;
-
-public:
-	AutoConvertFilter(std::unique_ptr<Filter> &&_filter,
-			  std::unique_ptr<Filter> &&_convert)
-		:Filter(_filter->GetOutAudioFormat()),
-		 filter(std::move(_filter)), convert(std::move(_convert)) {}
-
-	void Reset() noexcept override {
-		filter->Reset();
-
-		if (convert)
-			convert->Reset();
-	}
-
-	ConstBuffer<void> FilterPCM(ConstBuffer<void> src) override;
-	ConstBuffer<void> Flush() override;
-};
-
 class PreparedAutoConvertFilter final : public PreparedFilter {
 	/**
 	 * The underlying filter.
@@ -81,37 +53,17 @@ PreparedAutoConvertFilter::Open(AudioFormat &in_audio_format)
 
 	/* need to convert? */
 
-	std::unique_ptr<Filter> convert;
-	if (in_audio_format != child_audio_format) {
-		/* yes - create a convert_filter */
+	if (in_audio_format == child_audio_format)
+		/* no */
+		return new_filter;
 
-		convert.reset(convert_filter_new(in_audio_format,
-						 child_audio_format));
-	}
+	/* yes - create a convert_filter */
 
-	return std::make_unique<AutoConvertFilter>(std::move(new_filter),
-						   std::move(convert));
-}
+	auto convert = convert_filter_new(in_audio_format,
+					  child_audio_format);
 
-ConstBuffer<void>
-AutoConvertFilter::FilterPCM(ConstBuffer<void> src)
-{
-	if (convert != nullptr)
-		src = convert->FilterPCM(src);
-
-	return filter->FilterPCM(src);
-}
-
-ConstBuffer<void>
-AutoConvertFilter::Flush()
-{
-	if (convert != nullptr) {
-		auto result = convert->Flush();
-		if (!result.IsNull())
-			return filter->FilterPCM(result);
-	}
-
-	return filter->Flush();
+	return std::make_unique<TwoFilters>(std::move(convert),
+					    std::move(new_filter));
 }
 
 std::unique_ptr<PreparedFilter>

src/filter/plugins/ChainFilterPlugin.cxx

@@ -28,15 +28,14 @@
 #include <cassert>
 #include <list>
 #include <memory>
+#include <string>
 
 class ChainFilter final : public Filter {
 	struct Child {
-		const char *name;
 		std::unique_ptr<Filter> filter;
 
-		Child(const char *_name,
-		      std::unique_ptr<Filter> _filter) noexcept
-			:name(_name), filter(std::move(_filter)) {}
+		explicit Child(std::unique_ptr<Filter> &&_filter) noexcept
+			:filter(std::move(_filter)) {}
 	};
 
 	std::list<Child> children;
@@ -50,13 +49,12 @@ public:
 	explicit ChainFilter(AudioFormat _audio_format)
 		:Filter(_audio_format) {}
 
-	void Append(const char *name,
-		    std::unique_ptr<Filter> filter) noexcept {
+	void Append(std::unique_ptr<Filter> filter) noexcept {
 		assert(out_audio_format.IsValid());
 		out_audio_format = filter->GetOutAudioFormat();
 		assert(out_audio_format.IsValid());
 
-		children.emplace_back(name, std::move(filter));
+		children.emplace_back(std::move(filter));
 
 		RewindFlush();
 	}
@@ -75,10 +73,10 @@ private:
 
 class PreparedChainFilter final : public PreparedFilter {
 	struct Child {
-		const char *name;
+		const std::string name;
 		std::unique_ptr<PreparedFilter> filter;
 
-		Child(const char *_name,
+		Child(std::string_view _name,
 		      std::unique_ptr<PreparedFilter> _filter)
 			:name(_name), filter(std::move(_filter)) {}
 
@@ -91,7 +89,7 @@ class PreparedChainFilter final : public PreparedFilter {
 	std::list<Child> children;
 
 public:
-	void Append(const char *name,
+	void Append(std::string_view name,
 		    std::unique_ptr<PreparedFilter> filter) noexcept {
 		children.emplace_back(name, std::move(filter));
 	}
@@ -108,7 +106,7 @@ PreparedChainFilter::Child::Open(const AudioFormat &prev_audio_format)
 
 	if (conv_audio_format != prev_audio_format)
 		throw FormatRuntimeError("Audio format not supported by filter '%s': %s",
-					 name,
+					 name.c_str(),
 					 ToString(prev_audio_format).c_str());
 
 	return new_filter;
@@ -121,7 +119,7 @@ PreparedChainFilter::Open(AudioFormat &in_audio_format)
 
 	for (auto &child : children) {
 		AudioFormat audio_format = chain->GetOutAudioFormat();
-		chain->Append(child.name, child.Open(audio_format));
+		chain->Append(child.Open(audio_format));
 	}
 
 	return chain;
@@ -177,7 +175,7 @@ filter_chain_new() noexcept
 }
 
 void
-filter_chain_append(PreparedFilter &_chain, const char *name,
+filter_chain_append(PreparedFilter &_chain, std::string_view name,
 		    std::unique_ptr<PreparedFilter> filter) noexcept
 {
 	auto &chain = (PreparedChainFilter &)_chain;

src/filter/plugins/ChainFilterPlugin.hxx

@@ -28,6 +28,7 @@
 #define MPD_FILTER_CHAIN_HXX
 
 #include <memory>
+#include <string_view>
 
 class PreparedFilter;
 
@@ -45,7 +46,7 @@ filter_chain_new() noexcept;
  * @param filter the filter to be appended to #chain
  */
 void
-filter_chain_append(PreparedFilter &chain, const char *name,
+filter_chain_append(PreparedFilter &chain, std::string_view name,
 		    std::unique_ptr<PreparedFilter> filter) noexcept;
 
 #endif

src/filter/plugins/ConvertFilterPlugin.cxx

@@ -117,13 +117,13 @@ convert_filter_prepare() noexcept
 	return std::make_unique<PreparedConvertFilter>();
 }
 
-Filter *
+std::unique_ptr<Filter>
 convert_filter_new(const AudioFormat in_audio_format,
 		   const AudioFormat out_audio_format)
 {
 	std::unique_ptr<ConvertFilter> filter(new ConvertFilter(in_audio_format));
 	filter->Set(out_audio_format);
-	return filter.release();
+	return filter;
 }
 
 void

src/filter/plugins/ConvertFilterPlugin.hxx

@@ -29,7 +29,7 @@ struct AudioFormat;
 std::unique_ptr<PreparedFilter>
 convert_filter_prepare() noexcept;
 
-Filter *
+std::unique_ptr<Filter>
 convert_filter_new(AudioFormat in_audio_format,
 		   AudioFormat out_audio_format);
 

src/filter/plugins/FfmpegFilter.cxx

@@ -18,6 +18,7 @@
  */
 
 #include "FfmpegFilter.hxx"
+#include "lib/ffmpeg/Interleave.hxx"
 #include "lib/ffmpeg/SampleFormat.hxx"
 #include "util/ConstBuffer.hxx"
 
@@ -79,5 +80,5 @@ FfmpegFilter::FilterPCM(ConstBuffer<void> src)
 	/* TODO: call av_buffersink_get_frame() repeatedly?  Not
 	   possible with MPD's current Filter API */
 
-	return {frame.GetData(0), frame->nb_samples * GetOutAudioFormat().GetFrameSize()};
+	return Ffmpeg::InterleaveFrame(*frame, interleave_buffer);
 }

src/filter/plugins/FfmpegFilter.hxx

@@ -21,6 +21,7 @@
 #define MPD_FFMPEG_FILTER__HXX
 
 #include "filter/Filter.hxx"
+#include "lib/ffmpeg/Buffer.hxx"
 #include "lib/ffmpeg/Filter.hxx"
 #include "lib/ffmpeg/Frame.hxx"
 
@@ -32,6 +33,8 @@ class FfmpegFilter final : public Filter {
 	Ffmpeg::FilterContext buffer_src, buffer_sink;
 	Ffmpeg::Frame frame;
 
+	FfmpegBuffer interleave_buffer;
+
 	const int in_format, in_sample_rate, in_channels;
 
 	const size_t in_audio_frame_size;

src/filter/plugins/TwoFilters.cxx

@@ -17,7 +17,23 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#include "Ack.hxx"
-#include "util/Domain.hxx"
+#include "TwoFilters.hxx"
+#include "util/ConstBuffer.hxx"
 
-const Domain ack_domain("ack");
+ConstBuffer<void>
+TwoFilters::FilterPCM(ConstBuffer<void> src)
+{
+	return second->FilterPCM(first->FilterPCM(src));
+}
+
+ConstBuffer<void>
+TwoFilters::Flush()
+{
+	auto result = first->Flush();
+	if (!result.IsNull())
+		/* Flush() output from the first Filter must be
+		   filtered by the second Filter */
+		return second->FilterPCM(result);
+
+	return second->Flush();
+}

src/filter/plugins/TwoFilters.hxx

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2003-2020 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef MPD_WITH_CONVERT_FILTER_HXX
+#define MPD_WITH_CONVERT_FILTER_HXX
+
+#include "filter/Filter.hxx"
+
+#include <memory>
+
+/**
+ * A #Filter implementation which chains two other filters.
+ */
+class TwoFilters final : public Filter {
+	std::unique_ptr<Filter> first, second;
+
+public:
+	template<typename F, typename S>
+	TwoFilters(F &&_first, S &&_second) noexcept
+		:Filter(_second->GetOutAudioFormat()),
+		 first(std::forward<F>(_first)),
+		 second(std::forward<S>(_second)) {}
+
+	void Reset() noexcept override {
+		first->Reset();
+		second->Reset();
+	}
+
+	ConstBuffer<void> FilterPCM(ConstBuffer<void> src) override;
+	ConstBuffer<void> Flush() override;
+};
+
+#endif

src/filter/plugins/meson.build

@@ -14,6 +14,7 @@ filter_plugins = static_library(
   'filter_plugins',
   '../../AudioCompress/compress.c',
   'NullFilterPlugin.cxx',
+  'TwoFilters.cxx',
   'ChainFilterPlugin.cxx',
   'AutoConvertFilterPlugin.cxx',
   'ConvertFilterPlugin.cxx',

src/fs/Traits.hxx

@@ -88,6 +88,19 @@ struct PathTraitsFS {
 #endif
 	}
 
+	gcc_pure
+	static const_pointer GetFilenameSuffix(const_pointer filename) noexcept {
+		const_pointer dot = StringFindLast(filename, '.');
+		return dot != nullptr && dot > filename && dot[1] != 0
+			? dot + 1
+			: nullptr;
+	}
+
+	gcc_pure
+	static const_pointer GetPathSuffix(const_pointer path) noexcept {
+		return GetFilenameSuffix(GetBase(path));
+	}
+
 #ifdef _WIN32
 	gcc_pure gcc_nonnull_all
 	static constexpr bool IsDrive(const_pointer p) noexcept {
@@ -199,6 +212,19 @@ struct PathTraitsUTF8 {
 		return std::strrchr(p, SEPARATOR);
 	}
 
+	gcc_pure
+	static const_pointer GetFilenameSuffix(const_pointer filename) noexcept {
+		const_pointer dot = StringFindLast(filename, '.');
+		return dot != nullptr && dot > filename && dot[1] != 0
+			? dot + 1
+			: nullptr;
+	}
+
+	gcc_pure
+	static const_pointer GetPathSuffix(const_pointer path) noexcept {
+		return GetFilenameSuffix(GetBase(path));
+	}
+
 #ifdef _WIN32
 	gcc_pure gcc_nonnull_all
 	static constexpr bool IsDrive(const_pointer p) noexcept {

src/lib/ffmpeg/Buffer.hxx

@@ -20,36 +20,36 @@
 #ifndef MPD_FFMPEG_BUFFER_HXX
 #define MPD_FFMPEG_BUFFER_HXX
 
+#include "util/Compiler.h"
+
 extern "C" {
 #include <libavutil/mem.h>
 }
 
 #include <cstddef>
 
-/* suppress the ffmpeg compatibility macro */
-#ifdef SampleFormat
-#undef SampleFormat
-#endif
-
 class FfmpegBuffer {
-	void *data;
-	unsigned size;
+	void *data = nullptr;
+	unsigned size = 0;
 
 public:
-	FfmpegBuffer():data(nullptr), size(0) {}
+	FfmpegBuffer() noexcept = default;
 
-	~FfmpegBuffer() {
+	~FfmpegBuffer() noexcept {
 		av_free(data);
 	}
 
+	FfmpegBuffer(const FfmpegBuffer &) = delete;
+	FfmpegBuffer &operator=(const FfmpegBuffer &) = delete;
+
 	gcc_malloc
-	void *Get(size_t min_size) {
+	void *Get(size_t min_size) noexcept {
 		av_fast_malloc(&data, &size, min_size);
 		return data;
 	}
 
 	template<typename T>
-	T *GetT(size_t n) {
+	T *GetT(size_t n) noexcept {
 		return (T *)Get(n * sizeof(T));
 	}
 };

src/lib/ffmpeg/Interleave.cxx

@@ -0,0 +1,71 @@
+/*
+ * Copyright 2003-2020 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "Interleave.hxx"
+#include "Buffer.hxx"
+#include "Error.hxx"
+#include "pcm/Interleave.hxx"
+#include "util/ConstBuffer.hxx"
+
+extern "C" {
+#include <libavutil/frame.h>
+}
+
+#include <cassert>
+#include <new> // for std::bad_alloc
+
+namespace Ffmpeg {
+
+ConstBuffer<void>
+InterleaveFrame(const AVFrame &frame, FfmpegBuffer &buffer)
+{
+	assert(frame.nb_samples > 0);
+
+	const AVSampleFormat format = AVSampleFormat(frame.format);
+	const unsigned channels = frame.channels;
+	const std::size_t n_frames = frame.nb_samples;
+
+	int plane_size;
+	const int data_size =
+		av_samples_get_buffer_size(&plane_size, channels,
+					   n_frames, format, 1);
+	assert(data_size != 0);
+	if (data_size < 0)
+		throw MakeFfmpegError(data_size);
+
+	void *output_buffer;
+	if (av_sample_fmt_is_planar(format) && channels > 1) {
+		output_buffer = buffer.GetT<uint8_t>(data_size);
+		if (output_buffer == nullptr)
+			/* Not enough memory - shouldn't happen */
+			throw std::bad_alloc();
+
+		PcmInterleave(output_buffer,
+			      ConstBuffer<const void *>((const void *const*)frame.extended_data,
+							channels),
+			      n_frames,
+			      av_get_bytes_per_sample(format));
+	} else {
+		output_buffer = frame.extended_data[0];
+	}
+
+	return { output_buffer, (size_t)data_size };
+}
+
+} // namespace Ffmpeg

src/lib/ffmpeg/Interleave.hxx

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2003-2020 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef MPD_FFMPEG_INTERLEAVE_HXX
+#define MPD_FFMPEG_INTERLEAVE_HXX
+
+struct AVFrame;
+template<typename T> struct ConstBuffer;
+class FfmpegBuffer;
+
+namespace Ffmpeg {
+
+/**
+ * Return interleaved data from the given non-empty #AVFrame.  If the
+ * data is planar, then the data is copied to a buffer.
+ *
+ * Throws on error.
+ */
+ConstBuffer<void>
+InterleaveFrame(const AVFrame &frame, FfmpegBuffer &buffer);
+
+} // namespace Ffmpeg
+
+#endif

src/lib/ffmpeg/Time.hxx

@@ -31,11 +31,6 @@ extern "C" {
 #include <cassert>
 #include <cstdint>
 
-/* suppress the ffmpeg compatibility macro */
-#ifdef SampleFormat
-#undef SampleFormat
-#endif
-
 /* redefine AV_TIME_BASE_Q because libavutil's macro definition is a
    compound literal, which is illegal in C++ */
 #ifdef AV_TIME_BASE_Q

src/lib/ffmpeg/meson.build

@@ -26,6 +26,7 @@ endif
 ffmpeg = static_library(
   'ffmpeg',
   'Init.cxx',
+  'Interleave.cxx',
   'LogError.cxx',
   'LogCallback.cxx',
   'Error.cxx',

src/lib/yajl/Handle.cxx

@@ -0,0 +1,67 @@
+/*
+ * Copyright 2018-2020 Max Kellermann <max.kellermann@gmail.com>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
+ * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "Handle.hxx"
+#include "util/RuntimeError.hxx"
+#include "util/ScopeExit.hxx"
+#include "util/StringStrip.hxx"
+
+#include <cstring>
+
+/**
+ * Strip whitespace at the beginning and end and replace newline
+ * characters which are illegal in the MPD protocol.
+ */
+static const char *
+StripErrorMessage(char *s) noexcept
+{
+	s = Strip(s);
+
+	while (auto newline = std::strchr(s, '\n'))
+		*newline = ';';
+
+	return s;
+}
+
+namespace Yajl {
+
+void
+Handle::ThrowError()
+{
+	unsigned char *str = yajl_get_error(handle, false,
+					    nullptr, 0);
+	AtScopeExit(this, str) {
+		yajl_free_error(handle, str);
+	};
+
+	throw FormatRuntimeError("Failed to parse JSON: %s",
+				 StripErrorMessage((char *)str));
+}
+
+} // namespace Yajl

src/lib/yajl/Handle.hxx

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2018 Max Kellermann <max.kellermann@gmail.com>
+ * Copyright 2018-2020 Max Kellermann <max.kellermann@gmail.com>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -30,12 +30,8 @@
 #ifndef YAJL_HANDLE_HXX
 #define YAJL_HANDLE_HXX
 
-#include "util/RuntimeError.hxx"
-#include "util/ScopeExit.hxx"
-
 #include <yajl/yajl_parse.h>
 
-#include <stdexcept>
 #include <algorithm>
 
 namespace Yajl {
@@ -77,15 +73,12 @@ public:
 
 private:
 	void HandleStatus(yajl_status status) {
-		if (status == yajl_status_error) {
-			unsigned char *str = yajl_get_error(handle, false,
-							    nullptr, 0);
-			AtScopeExit(this, str) {
-				yajl_free_error(handle, str);
-			};
-			throw FormatRuntimeError("Failed to parse JSON: %s", str);
-		}
+		if (status == yajl_status_error)
+			ThrowError();
 	}
+
+	[[noreturn]]
+	void ThrowError();
 };
 
 } // namespace Yajl

src/lib/yajl/meson.build

@@ -5,6 +5,7 @@ endif
 
 yajl = static_library(
   'yajl',
+  'Handle.cxx',
   'ResponseParser.cxx',
   'ParseInputStream.cxx',
   include_directories: inc,

src/playlist/PlaylistRegistry.cxx

@@ -71,6 +71,9 @@ static constexpr unsigned n_playlist_plugins =
 /** which plugins have been initialized successfully? */
 static bool playlist_plugins_enabled[n_playlist_plugins];
 
+/** which plugins have the "as_folder" option enabled? */
+static bool playlist_plugins_as_folder[n_playlist_plugins];
+
 #define playlist_plugins_for_each_enabled(plugin) \
 	playlist_plugins_for_each(plugin) \
 		if (playlist_plugins_enabled[playlist_plugin_iterator - playlist_plugins])
@@ -96,6 +99,10 @@ playlist_list_global_init(const ConfigData &config)
 
 		playlist_plugins_enabled[i] =
 			playlist_plugin_init(playlist_plugins[i], *param);
+
+		playlist_plugins_as_folder[i] =
+			param->GetBlockValue("as_directory",
+					     playlist_plugins[i]->as_folder);
 	}
 }
 
@@ -106,6 +113,16 @@ playlist_list_global_finish() noexcept
 		playlist_plugin_finish(plugin);
 }
 
+bool
+GetPlaylistPluginAsFolder(const PlaylistPlugin &plugin) noexcept
+{
+	/* this loop has no end condition because it must finish when
+	   the plugin was found */
+	for (std::size_t i = 0;; ++i)
+		if (playlist_plugins[i] == &plugin)
+			return playlist_plugins_as_folder[i];
+}
+
 static std::unique_ptr<SongEnumerator>
 playlist_list_open_uri_scheme(const char *uri, Mutex &mutex,
 			      bool *tried)
@@ -207,11 +224,7 @@ gcc_pure
 static StringView
 ExtractMimeTypeMainPart(StringView s) noexcept
 {
-	const auto separator = s.Find(';');
-	if (separator != nullptr)
-		s.SetEnd(separator);
-
-	return s;
+	return s.Split(';').first;
 }
 
 static std::unique_ptr<SongEnumerator>

src/playlist/PlaylistRegistry.hxx

@@ -59,6 +59,14 @@ public:
 	}
 };
 
+/**
+ * Shall this playlists supported by this plugin be represented as
+ * directories in the database?
+ */
+gcc_const
+bool
+GetPlaylistPluginAsFolder(const PlaylistPlugin &plugin) noexcept;
+
 /**
  * Opens a playlist by its URI.
  */

src/protocol/Ack.hxx

@@ -25,8 +25,6 @@
 #include <stdexcept>
 #include <utility>
 
-class Domain;
-
 enum ack {
 	ACK_ERROR_NOT_LIST = 1,
 	ACK_ERROR_ARG = 2,
@@ -43,8 +41,6 @@ enum ack {
 	ACK_ERROR_EXIST = 56,
 };
 
-extern const Domain ack_domain;
-
 class ProtocolError : public std::runtime_error {
 	enum ack code;
 

src/storage/plugins/CurlStorage.cxx

@@ -80,7 +80,7 @@ std::string_view
 CurlStorage::MapToRelativeUTF8(std::string_view uri_utf8) const noexcept
 {
 	return PathTraitsUTF8::Relative(base,
-					CurlUnescape(uri_utf8).c_str());
+					CurlUnescape(uri_utf8));
 }
 
 class BlockingHttpRequest : protected CurlResponseHandler {

src/util/FormatString.hxx

@@ -27,16 +27,14 @@
 template<typename T> class AllocatedString;
 
 /**
- * Format into a newly allocated string.  The caller frees the return
- * value with delete[].
+ * Format into an #AllocatedString.
  */
 gcc_nonnull_all
 AllocatedString<char>
 FormatStringV(const char *fmt, std::va_list args) noexcept;
 
 /**
- * Format into a newly allocated string.  The caller frees the return
- * value with delete[].
+ * Format into an #AllocatedString.
  */
 gcc_nonnull(1) gcc_printf(1,2)
 AllocatedString<char>

test/meson.build

@@ -264,7 +264,6 @@ if enable_database
   executable(
     'DumpDatabase',
     'DumpDatabase.cxx',
-    '../src/protocol/Ack.cxx',
     '../src/db/Registry.cxx',
     '../src/db/Selection.cxx',
     '../src/db/PlaylistVector.cxx',