TagHandler: use a TagBuilder internally

Reduce heap allocator overhead.

src/SongUpdate.cxx

@@ -29,6 +29,7 @@
 #include "DecoderPlugin.hxx"
 #include "DecoderList.hxx"
 #include "tag/Tag.hxx"
+#include "tag/TagBuilder.hxx"
 #include "tag/TagHandler.hxx"
 #include "tag/TagId3.hxx"
 #include "tag/ApeTag.hxx"
@@ -113,15 +114,15 @@ Song::UpdateFile()
 	Mutex mutex;
 	Cond cond;
 
+	TagBuilder tag_builder;
+
 	do {
 		/* load file tag */
-		tag = new Tag();
 		if (decoder_plugin_scan_file(plugin, path_fs.c_str(),
-					     &full_tag_handler, tag))
+					     &full_tag_handler, &tag_builder))
 			break;
 
-		delete tag;
-		tag = nullptr;
+		tag_builder.Clear();
 
 		/* fall back to stream tag */
 		if (plugin->scan_stream != NULL) {
@@ -134,14 +135,12 @@ Song::UpdateFile()
 
 			/* now try the stream_tag() method */
 			if (is != NULL) {
-				tag = new Tag();
 				if (decoder_plugin_scan_stream(plugin, is,
 							       &full_tag_handler,
-							       tag))
+							       &tag_builder))
 					break;
 
-				delete tag;
-				tag = nullptr;
+				tag_builder.Clear();
 
 				is->LockSeek(0, SEEK_SET, IgnoreError());
 			}
@@ -153,10 +152,15 @@ Song::UpdateFile()
 	if (is != NULL)
 		is->Close();
 
-	if (tag != nullptr && tag->IsEmpty())
-		tag_scan_fallback(path_fs.c_str(), &full_tag_handler, tag);
+	if (!tag_builder.IsDefined())
+		return false;
 
-	return tag != nullptr;
+	if (tag_builder.IsEmpty())
+		tag_scan_fallback(path_fs.c_str(), &full_tag_handler,
+				  &tag_builder);
+
+	tag = tag_builder.Commit();
+	return true;
 }
 
 bool

src/UpdateContainer.cxx

@@ -28,7 +28,7 @@
 #include "Mapper.hxx"
 #include "fs/Path.hxx"
 #include "tag/TagHandler.hxx"
-#include "tag/Tag.hxx"
+#include "tag/TagBuilder.hxx"
 
 #include <glib.h>
 
@@ -86,6 +86,7 @@ update_container_file(Directory *directory,
 
 	char *vtrack;
 	unsigned int tnum = 0;
+	TagBuilder tag_builder;
 	while ((vtrack = plugin->container_scan(pathname.c_str(), ++tnum)) != NULL) {
 		Song *song = Song::NewFile(vtrack, contdir);
 
@@ -95,9 +96,13 @@ update_container_file(Directory *directory,
 		const Path child_path_fs =
 			map_directory_child_fs(contdir, vtrack);
 
-		song->tag = new Tag();
 		decoder_plugin_scan_file(plugin, child_path_fs.c_str(),
-					 &add_tag_handler, song->tag);
+					 &add_tag_handler, &tag_builder);
+
+		if (tag_builder.IsDefined())
+			song->tag = tag_builder.Commit();
+		else
+			tag_builder.Clear();
 
 		db_lock();
 		contdir->AddSong(song);

src/decoder/FlacMetadata.cxx

@@ -23,6 +23,7 @@
 #include "tag/Tag.hxx"
 #include "tag/TagHandler.hxx"
 #include "tag/TagTable.hxx"
+#include "tag/TagBuilder.hxx"
 #include "replay_gain_info.h"
 
 #include <glib.h>
@@ -231,7 +232,9 @@ void
 flac_vorbis_comments_to_tag(Tag &tag,
 			    const FLAC__StreamMetadata_VorbisComment *comment)
 {
-	flac_scan_comments(comment, &add_tag_handler, &tag);
+	TagBuilder tag_builder;
+	flac_scan_comments(comment, &add_tag_handler, &tag_builder);
+	tag_builder.Commit(tag);
 }
 
 void

src/decoder/OpusDecoderPlugin.cxx

@@ -28,6 +28,7 @@
 #include "OggCodec.hxx"
 #include "CheckAudioFormat.hxx"
 #include "tag/TagHandler.hxx"
+#include "tag/TagBuilder.hxx"
 #include "InputStream.hxx"
 #include "util/Error.hxx"
 
@@ -222,14 +223,16 @@ MPDOpusDecoder::HandleBOS(const ogg_packet &packet)
 inline enum decoder_command
 MPDOpusDecoder::HandleTags(const ogg_packet &packet)
 {
-	Tag tag;
+	TagBuilder tag_builder;
 
 	enum decoder_command cmd;
 	if (ScanOpusTags(packet.packet, packet.bytes,
-			 &add_tag_handler, &tag) &&
-	    !tag.IsEmpty())
+			 &add_tag_handler, &tag_builder) &&
+	    !tag_builder.IsEmpty()) {
+		Tag tag;
+		tag_builder.Commit(tag);
 		cmd = decoder_tag(decoder, input_stream, std::move(tag));
-	else
+	} else
 		cmd = decoder_get_command(decoder);
 
 	return cmd;

src/decoder/VorbisComments.cxx

@@ -23,6 +23,7 @@
 #include "tag/Tag.hxx"
 #include "tag/TagTable.hxx"
 #include "tag/TagHandler.hxx"
+#include "tag/TagBuilder.hxx"
 #include "replay_gain_info.h"
 
 #include <glib.h>
@@ -138,13 +139,9 @@ vorbis_comments_scan(char **comments,
 Tag *
 vorbis_comments_to_tag(char **comments)
 {
-	Tag *tag = new Tag();
-	vorbis_comments_scan(comments, &add_tag_handler, tag);
-
-	if (tag->IsEmpty()) {
-		delete tag;
-		tag = NULL;
-	}
-
-	return tag;
+	TagBuilder tag_builder;
+	vorbis_comments_scan(comments, &add_tag_handler, &tag_builder);
+	return tag_builder.IsEmpty()
+		? nullptr
+		: tag_builder.Commit();
 }

src/tag/TagHandler.cxx

@@ -19,24 +19,24 @@
 
 #include "config.h"
 #include "TagHandler.hxx"
-#include "Tag.hxx"
+#include "TagBuilder.hxx"
 
 #include <glib.h>
 
 static void
 add_tag_duration(unsigned seconds, void *ctx)
 {
-	Tag *tag = (Tag *)ctx;
+	TagBuilder &tag = *(TagBuilder *)ctx;
 
-	tag->time = seconds;
+	tag.SetTime(seconds);
 }
 
 static void
 add_tag_tag(enum tag_type type, const char *value, void *ctx)
 {
-	Tag *tag = (Tag *)ctx;
+	TagBuilder &tag = *(TagBuilder *)ctx;
 
-	tag->AddItem(type, value);
+	tag.AddItem(type, value);
 }
 
 const struct tag_handler add_tag_handler = {
@@ -48,10 +48,10 @@ const struct tag_handler add_tag_handler = {
 static void
 full_tag_pair(const char *name, gcc_unused const char *value, void *ctx)
 {
-	Tag *tag = (Tag *)ctx;
+	TagBuilder &tag = *(TagBuilder *)ctx;
 
 	if (g_ascii_strcasecmp(name, "cuesheet") == 0)
-		tag->has_playlist = true;
+		tag.SetHasPlaylist(true);
 }
 
 const struct tag_handler full_tag_handler = {

src/tag/TagHandler.hxx

@@ -86,13 +86,13 @@ tag_handler_invoke_pair(const struct tag_handler *handler, void *ctx,
 }
 
 /**
- * This #tag_handler implementation adds tag values to a #tag object
+ * This #tag_handler implementation adds tag values to a #TagBuilder object
  * (casted from the context pointer).
  */
 extern const struct tag_handler add_tag_handler;
 
 /**
- * This #tag_handler implementation adds tag values to a #tag object
+ * This #tag_handler implementation adds tag values to a #TagBuilder object
  * (casted from the context pointer), and supports the has_playlist
  * attribute.
  */

src/tag/TagId3.cxx

@@ -22,6 +22,7 @@
 #include "TagHandler.hxx"
 #include "TagTable.hxx"
 #include "Tag.hxx"
+#include "TagBuilder.hxx"
 #include "util/Error.hxx"
 #include "ConfigGlobal.hxx"
 
@@ -387,16 +388,11 @@ scan_id3_tag(struct id3_tag *tag,
 Tag *
 tag_id3_import(struct id3_tag *tag)
 {
-	Tag *ret = new Tag();
-
-	scan_id3_tag(tag, &add_tag_handler, ret);
-
-	if (ret->IsEmpty()) {
-		delete ret;
-		ret = nullptr;
-	}
-
-	return ret;
+	TagBuilder tag_builder;
+	scan_id3_tag(tag, &add_tag_handler, &tag_builder);
+	return tag_builder.IsEmpty()
+		? nullptr
+		: tag_builder.Commit();
 }
 
 static int