decoder/DecoderPlugin: container_scan() returns forward_list<DetachedSong>

Speed up container_scan() again, by eliminating the need to call
scan_file() for each item.

Makefile.am

@@ -1894,6 +1894,7 @@ test_run_decoder_LDADD = \
 test_run_decoder_SOURCES = test/run_decoder.cxx \
 	test/FakeDecoderAPI.cxx test/FakeDecoderAPI.hxx \
 	test/ScopeIOThread.hxx \
+	src/DetachedSong.cxx \
 	src/Log.cxx src/LogBackend.cxx \
 	src/IOThread.cxx \
 	src/ReplayGainInfo.cxx
@@ -1915,6 +1916,7 @@ test_read_tags_LDADD = \
 test_read_tags_SOURCES = test/read_tags.cxx \
 	test/FakeDecoderAPI.cxx test/FakeDecoderAPI.hxx \
 	test/ScopeIOThread.hxx \
+	src/DetachedSong.cxx \
 	src/Log.cxx src/LogBackend.cxx \
 	src/IOThread.cxx \
 	src/ReplayGainInfo.cxx
@@ -1946,6 +1948,8 @@ test_ContainerScan_LDADD = \
 	libsystem.a \
 	libutil.a
 test_ContainerScan_SOURCES = test/ContainerScan.cxx \
+	src/DetachedSong.cxx \
+	src/SongSave.cxx src/TagSave.cxx \
 	src/Log.cxx src/LogBackend.cxx \
 	src/ReplayGainInfo.cxx \
 	$(DECODER_SRC)

src/db/update/Container.cxx

@@ -20,6 +20,7 @@
 #include "config.h" /* must be first for large file support */
 #include "Walk.hxx"
 #include "UpdateDomain.hxx"
+#include "DetachedSong.hxx"
 #include "db/DatabaseLock.hxx"
 #include "db/plugins/simple/Directory.hxx"
 #include "db/plugins/simple/Song.hxx"
@@ -28,8 +29,6 @@
 #include "decoder/DecoderList.hxx"
 #include "fs/AllocatedPath.hxx"
 #include "storage/FileInfo.hxx"
-#include "tag/TagHandler.hxx"
-#include "tag/TagBuilder.hxx"
 #include "Log.hxx"
 #include "util/AllocatedString.hxx"
 
@@ -97,34 +96,21 @@ UpdateWalk::UpdateContainerFile(Directory &directory,
 	}
 
 	try {
-		const auto v = plugin.container_scan(pathname);
+		auto v = plugin.container_scan(pathname);
 		if (v.empty()) {
 			editor.LockDeleteDirectory(contdir);
 			return false;
 		}
 
-		TagBuilder tag_builder;
+		for (auto &vtrack : v) {
-		for (const auto &vtrack : v) {
+			Song *song = Song::NewFrom(std::move(vtrack),
-			Song *song = Song::NewFile(vtrack.c_str(), *contdir);
+						   *contdir);
 
 			// shouldn't be necessary but it's there..
 			song->mtime = info.mtime;
 
-			try {
+			FormatDefault(update_domain, "added %s/%s",
-				const auto vtrack_fs =
+				      contdir->GetPath(), song->uri);
-					AllocatedPath::FromUTF8Throw(vtrack.c_str());
-
-				const auto child_path_fs = AllocatedPath::Build(pathname,
-										vtrack_fs);
-				plugin.ScanFile(child_path_fs,
-						add_tag_handler, &tag_builder);
-			} catch (const std::runtime_error &e) {
-				song->Free();
-				LogError(e);
-				continue;
-			}
-
-			tag_builder.Commit(song->tag);
 
 			{
 				const ScopeDatabaseLock protect;
@@ -132,9 +118,6 @@ UpdateWalk::UpdateContainerFile(Directory &directory,
 			}
 
 			modified = true;
-
-			FormatDefault(update_domain, "added %s/%s",
-				      directory.GetPath(), vtrack.c_str());
 		}
 	} catch (const std::runtime_error &e) {
 		editor.LockDeleteDirectory(contdir);

src/decoder/DecoderPlugin.hxx

@@ -23,13 +23,13 @@
 #include "Compiler.h"
 
 #include <forward_list>
-#include <string>
 
 struct ConfigBlock;
 class InputStream;
 struct TagHandler;
 class Path;
 class DecoderClient;
+class DetachedSong;
 
 struct DecoderPlugin {
 	const char *name;
@@ -93,7 +93,7 @@ struct DecoderPlugin {
 	 * a filename for every single track;
 	 * do not include full pathname here, just the "virtual" file
 	 */
-	std::forward_list<std::string> (*container_scan)(Path path_fs);
+	std::forward_list<DetachedSong> (*container_scan)(Path path_fs);
 
 	/* last element in these arrays must always be a nullptr: */
 	const char *const*suffixes;

src/decoder/plugins/GmeDecoderPlugin.cxx

@@ -22,7 +22,9 @@
 #include "../DecoderAPI.hxx"
 #include "config/Block.cxx"
 #include "CheckAudioFormat.hxx"
+#include "DetachedSong.hxx"
 #include "tag/TagHandler.hxx"
+#include "tag/TagBuilder.hxx"
 #include "fs/Path.hxx"
 #include "fs/AllocatedPath.hxx"
 #include "util/ScopeExit.hxx"
@@ -266,10 +268,10 @@ gme_scan_file(Path path_fs,
 	return ScanMusicEmu(emu, container.track, handler, handler_ctx);
 }
 
-static std::forward_list<std::string>
+static std::forward_list<DetachedSong>
 gme_container_scan(Path path_fs)
 {
-	std::forward_list<std::string> list;
+	std::forward_list<DetachedSong> list;
 
 	Music_Emu *emu;
 	const char *gme_err = gme_open_file(path_fs.c_str(), &emu,
@@ -279,20 +281,27 @@ gme_container_scan(Path path_fs)
 		return list;
 	}
 
+	AtScopeExit(emu) { gme_delete(emu); };
+
 	const unsigned num_songs = gme_track_count(emu);
-	gme_delete(emu);
 	/* if it only contains a single tune, don't treat as container */
 	if (num_songs < 2)
 		return list;
 
 	const char *subtune_suffix = uri_get_suffix(path_fs.c_str());
 
+	TagBuilder tag_builder;
+
 	auto tail = list.before_begin();
 	for (unsigned i = 1; i <= num_songs; ++i) {
+		ScanMusicEmu(emu, i,
+			     add_tag_handler, &tag_builder);
+
 		char track_name[64];
 		snprintf(track_name, sizeof(track_name),
 			 SUBTUNE_PREFIX "%03u.%s", i, subtune_suffix);
-		tail = list.emplace_after(tail, track_name);
+		tail = list.emplace_after(tail, track_name,
+					  tag_builder.Commit());
 	}
 
 	return list;

src/decoder/plugins/SidplayDecoderPlugin.cxx

@@ -21,6 +21,8 @@
 #include "SidplayDecoderPlugin.hxx"
 #include "../DecoderAPI.hxx"
 #include "tag/TagHandler.hxx"
+#include "tag/TagBuilder.hxx"
+#include "DetachedSong.hxx"
 #include "fs/Path.hxx"
 #include "fs/AllocatedPath.hxx"
 #include "util/Macros.hxx"
@@ -467,12 +469,16 @@ sidplay_scan_file(Path path_fs,
 	return true;
 }
 
-static std::forward_list<std::string>
+static std::forward_list<DetachedSong>
 sidplay_container_scan(Path path_fs)
 {
-	std::forward_list<std::string> list;
+	std::forward_list<DetachedSong> list;
 
-	SidTune tune(path_fs.c_str(), nullptr, true);
+#ifdef HAVE_SIDPLAYFP
+	SidTune tune(path_fs.c_str());
+#else
+	SidTuneMod tune(path_fs.c_str());
+#endif
 	if (!tune.getStatus())
 		return list;
 
@@ -489,13 +495,21 @@ sidplay_container_scan(Path path_fs)
 	if(!all_files_are_containers && n_tracks < 2)
 		return list;
 
+	TagBuilder tag_builder;
+
 	auto tail = list.before_begin();
 	for (unsigned i = 1; i <= n_tracks; ++i) {
+		tune.selectSong(i);
+
+		ScanSidTuneInfo(info, i, n_tracks,
+				add_tag_handler, &tag_builder);
+
 		char track_name[32];
 		/* Construct container/tune path names, eg.
 		   Delta.sid/tune_001.sid */
 		sprintf(track_name, SUBTUNE_PREFIX "%03u.sid", i);
-		tail = list.emplace_after(tail, track_name);
+		tail = list.emplace_after(tail, track_name,
+					  tag_builder.Commit());
 	}
 
 	return list;

test/ContainerScan.cxx

@@ -19,6 +19,8 @@
 
 #include "config.h"
 #include "Log.hxx"
+#include "DetachedSong.hxx"
+#include "SongSave.hxx"
 #include "decoder/DecoderList.hxx"
 #include "decoder/DecoderPlugin.hxx"
 #include "fs/Path.hxx"
@@ -84,7 +86,7 @@ try {
 	BufferedOutputStream bos(sos);
 
 	for (const auto &song : v)
-		bos.Format("%s\n", song.c_str());
+		song_save(bos, song);
 
 	bos.Flush();