DetachedSong: add method Update()

Don't create an intermediate Song instance when all we want is a
DetachedSong.

src/DetachedSong.hxx

@@ -179,6 +179,13 @@ public:
 
 	gcc_pure
 	double GetDuration() const;
+
+	/**
+	 * Update the #tag and #mtime.
+	 *
+	 * @return true on success
+	 */
+	bool Update();
 };
 
 #endif

src/PlaylistEdit.cxx

@@ -61,13 +61,11 @@ PlaylistResult
 playlist::AppendFile(PlayerControl &pc,
 		     const char *path_utf8, unsigned *added_id)
 {
-	Song *song = Song::LoadFile(path_utf8, nullptr);
-	if (song == nullptr)
+	DetachedSong song(path_utf8);
+	if (!song.Update())
 		return PlaylistResult::NO_SUCH_SONG;
 
-	const auto result = AppendSong(pc, DetachedSong(*song), added_id);
-	song->Free();
-	return result;
+	return AppendSong(pc, std::move(song), added_id);
 }
 
 PlaylistResult

src/PlaylistSong.cxx

@@ -100,12 +100,11 @@ playlist_check_load_song(const DetachedSong *song, const char *uri, bool secure)
 	if (uri_has_scheme(uri)) {
 		dest = new DetachedSong(uri);
 	} else if (PathTraitsUTF8::IsAbsolute(uri) && secure) {
-		Song *tmp = Song::LoadFile(uri, nullptr);
-		if (tmp == nullptr)
+		dest = new DetachedSong(uri);
+		if (!dest->Update()) {
+			delete dest;
 			return nullptr;
-
-		dest = new DetachedSong(*tmp);
-		delete tmp;
+		}
 	} else {
 		const Database *db = GetDatabase();
 		if (db == nullptr)

src/SongUpdate.cxx

@@ -19,6 +19,7 @@
 
 #include "config.h" /* must be first for large file support */
 #include "Song.hxx"
+#include "DetachedSong.hxx"
 #include "util/UriUtil.hxx"
 #include "Directory.hxx"
 #include "Mapper.hxx"
@@ -126,3 +127,39 @@ Song::UpdateFileInArchive()
 	tag = tag_builder.CommitNew();
 	return true;
 }
+
+bool
+DetachedSong::Update()
+{
+	if (IsAbsoluteFile()) {
+		const AllocatedPath path_fs =
+			AllocatedPath::FromUTF8(uri.c_str());
+
+		struct stat st;
+		if (!StatFile(path_fs, st) || !S_ISREG(st.st_mode))
+			return false;
+
+		TagBuilder tag_builder;
+		if (!tag_file_scan(path_fs, full_tag_handler, &tag_builder))
+			return false;
+
+		if (tag_builder.IsEmpty())
+			tag_scan_fallback(path_fs, &full_tag_handler,
+					  &tag_builder);
+
+		mtime = st.st_mtime;
+		tag_builder.Commit(tag);
+		return true;
+	} else if (IsRemote()) {
+		TagBuilder tag_builder;
+		if (!tag_stream_scan(uri.c_str(), full_tag_handler,
+				     &tag_builder))
+			return false;
+
+		mtime = 0;
+		tag_builder.Commit(tag);
+		return true;
+	} else
+		// TODO: implement
+		return false;
+}

src/command/OtherCommands.cxx

@@ -23,7 +23,7 @@
 #include "CommandError.hxx"
 #include "UpdateGlue.hxx"
 #include "Directory.hxx"
-#include "Song.hxx"
+#include "DetachedSong.hxx"
 #include "SongPrint.hxx"
 #include "TagPrint.hxx"
 #include "TagStream.hxx"
@@ -140,15 +140,14 @@ handle_lsinfo(Client &client, int argc, char *argv[])
 		if (!client_allow_file(client, path_fs, error))
 			return print_error(client, error);
 
-		Song *song = Song::LoadFile(path_utf8, nullptr);
-		if (song == nullptr) {
+		DetachedSong song(path_utf8);
+		if (!song.Update()) {
 			command_error(client, ACK_ERROR_NO_EXIST,
 				      "No such file");
 			return CommandResult::ERROR;
 		}
 
-		song_print_info(client, *song);
-		song->Free();
+		song_print_info(client, song);
 		return CommandResult::OK;
 	}