decoder_plugin: scan tags with callback table

Pass a callback table to scan_file() and scan_stream(), instead of
returning a tag object.

21 files changed, 286 insertions, 213 deletions

diff --git a/src/decoder/audiofile_decoder_plugin.c b/src/decoder/audiofile_decoder_plugin.c
index 8d6236a57..7db7c7517 100644
--- a/src/decoder/audiofile_decoder_plugin.c
+++ b/src/decoder/audiofile_decoder_plugin.c
@@ -20,6 +20,7 @@
 #include "config.h"
 #include "decoder_api.h"
 #include "audio_check.h"
+#include "tag_handler.h"
 
 #include <audiofile.h>
 #include <af_vfs.h>
@@ -222,20 +223,20 @@ audiofile_stream_decode(struct decoder *decoder, struct input_stream *is)
 	afCloseFile(af_fp);
 }
 
-static struct tag *audiofile_tag_dup(const char *file)
+static bool
+audiofile_scan_file(const char *file,
+		    const struct tag_handler *handler, void *handler_ctx)
 {
-	struct tag *ret = NULL;
 	int total_time = audiofile_get_duration(file);
 
-	if (total_time >= 0) {
-		ret = tag_new();
-		ret->time = total_time;
-	} else {
+	if (total_time < 0) {
 		g_debug("Failed to get total song time from: %s\n",
 			file);
+		return false;
 	}
 
-	return ret;
+	tag_handler_invoke_duration(handler, handler_ctx, total_time);
+	return true;
 }
 
 static const char *const audiofile_suffixes[] = {
@@ -251,7 +252,7 @@ static const char *const audiofile_mime_types[] = {
 const struct decoder_plugin audiofile_decoder_plugin = {
 	.name = "audiofile",
 	.stream_decode = audiofile_stream_decode,
-	.tag_dup = audiofile_tag_dup,
+	.scan_file = audiofile_scan_file,
 	.suffixes = audiofile_suffixes,
 	.mime_types = audiofile_mime_types,
 };
diff --git a/src/decoder/dsdiff_decoder_plugin.c b/src/decoder/dsdiff_decoder_plugin.c
index 47b71d8c0..391a5bf78 100644
--- a/src/decoder/dsdiff_decoder_plugin.c
+++ b/src/decoder/dsdiff_decoder_plugin.c
@@ -433,8 +433,10 @@ dsdiff_stream_decode(struct decoder *decoder, struct input_stream *is)
 		dsd2pcm_destroy(dsd2pcm[i]);
 }
 
-static struct tag *
-dsdiff_stream_tag(struct input_stream *is)
+static bool
+dsdiff_scan_stream(struct input_stream *is,
+		   G_GNUC_UNUSED const struct tag_handler *handler,
+		   G_GNUC_UNUSED void *handler_ctx)
 {
 	struct dsdiff_metadata metadata = {
 		.sample_rate = 0,
@@ -443,17 +445,17 @@ dsdiff_stream_tag(struct input_stream *is)
 
 	struct dsdiff_chunk_header chunk_header;
 	if (!dsdiff_read_metadata(NULL, is, &metadata, &chunk_header))
-		return NULL;
+		return false;
 
 	struct audio_format audio_format;
 	if (!audio_format_init_checked(&audio_format, metadata.sample_rate / 8,
 				       SAMPLE_FORMAT_S24_P32,
 				       metadata.channels, NULL))
 		/* refuse to parse files which we cannot play anyway */
-		return NULL;
+		return false;
 
 	/* no total time estimate, no tags implemented yet */
-	return tag_new();
+	return true;
 }
 
 static const char *const dsdiff_suffixes[] = {
@@ -470,7 +472,7 @@ const struct decoder_plugin dsdiff_decoder_plugin = {
 	.name = "dsdiff",
 	.init = dsdiff_init,
 	.stream_decode = dsdiff_stream_decode,
-	.stream_tag = dsdiff_stream_tag,
+	.scan_stream = dsdiff_scan_stream,
 	.suffixes = dsdiff_suffixes,
 	.mime_types = dsdiff_mime_types,
 };
diff --git a/src/decoder/faad_decoder_plugin.c b/src/decoder/faad_decoder_plugin.c
index 91aa5392a..911f033b8 100644
--- a/src/decoder/faad_decoder_plugin.c
+++ b/src/decoder/faad_decoder_plugin.c
@@ -21,6 +21,7 @@
 #include "decoder_api.h"
 #include "decoder_buffer.h"
 #include "audio_check.h"
+#include "tag_handler.h"
 
 #define AAC_MAX_CHANNELS	6
 
@@ -487,18 +488,17 @@ faad_stream_decode(struct decoder *mpd_decoder, struct input_stream *is)
 	faacDecClose(decoder);
 }
 
-static struct tag *
-faad_stream_tag(struct input_stream *is)
+static bool
+faad_scan_stream(struct input_stream *is,
+		 const struct tag_handler *handler, void *handler_ctx)
 {
 	int file_time = faad_get_file_time(is);
-	struct tag *tag;
 
 	if (file_time < 0)
-		return NULL;
+		return false;
 
-	tag = tag_new();
-	tag->time = file_time;
-	return tag;
+	tag_handler_invoke_duration(handler, handler_ctx, file_time);
+	return true;
 }
 
 static const char *const faad_suffixes[] = { "aac", NULL };
@@ -509,7 +509,7 @@ static const char *const faad_mime_types[] = {
 const struct decoder_plugin faad_decoder_plugin = {
 	.name = "faad",
 	.stream_decode = faad_stream_decode,
-	.stream_tag = faad_stream_tag,
+	.scan_stream = faad_scan_stream,
 	.suffixes = faad_suffixes,
 	.mime_types = faad_mime_types,
 };
diff --git a/src/decoder/ffmpeg_decoder_plugin.c b/src/decoder/ffmpeg_decoder_plugin.c
index 20d24f130..6ad10026a 100644
--- a/src/decoder/ffmpeg_decoder_plugin.c
+++ b/src/decoder/ffmpeg_decoder_plugin.c
@@ -21,6 +21,7 @@
 #include "decoder_api.h"
 #include "audio_check.h"
 #include "ffmpeg_metadata.h"
+#include "tag_handler.h"
 
 #include <glib.h>
 
@@ -570,22 +571,23 @@ ffmpeg_decode(struct decoder *decoder, struct input_stream *input)
 }
 
 //no tag reading in ffmpeg, check if playable
-static struct tag *
-ffmpeg_stream_tag(struct input_stream *is)
+static bool
+ffmpeg_scan_stream(struct input_stream *is,
+		   const struct tag_handler *handler, void *handler_ctx)
 {
 	AVInputFormat *input_format = ffmpeg_probe(NULL, is);
 	if (input_format == NULL)
-		return NULL;
+		return false;
 
 	struct mpd_ffmpeg_stream *stream = mpd_ffmpeg_stream_open(NULL, is);
 	if (stream == NULL)
-		return NULL;
+		return false;
 
 	AVFormatContext *f = NULL;
 	if (mpd_ffmpeg_open_input(&f, stream->io, is->uri,
 				  input_format) != 0) {
 		mpd_ffmpeg_stream_close(stream);
-		return NULL;
+		return false;
 	}
 
 #if LIBAVFORMAT_VERSION_INT >= AV_VERSION_INT(53,6,0)
@@ -601,23 +603,22 @@ ffmpeg_stream_tag(struct input_stream *is)
 		av_close_input_stream(f);
 #endif
 		mpd_ffmpeg_stream_close(stream);
-		return NULL;
+		return false;
 	}
 
-	struct tag *tag = tag_new();
-
-	tag->time = f->duration != (int64_t)AV_NOPTS_VALUE
-		? f->duration / AV_TIME_BASE
-		: 0;
+	if (f->duration != (int64_t)AV_NOPTS_VALUE)
+		tag_handler_invoke_duration(handler, handler_ctx,
+					    f->duration / AV_TIME_BASE);
 
 #if LIBAVFORMAT_VERSION_INT < AV_VERSION_INT(52,101,0)
 	av_metadata_conv(f, NULL, f->iformat->metadata_conv);
 #endif
 
-	ffmpeg_copy_dictionary(tag, f->metadata);
+	ffmpeg_scan_dictionary(f->metadata, handler, handler_ctx);
 	int idx = ffmpeg_find_audio_stream(f);
 	if (idx >= 0)
-		ffmpeg_copy_dictionary(tag, f->streams[idx]->metadata);
+		ffmpeg_scan_dictionary(f->streams[idx]->metadata,
+				       handler, handler_ctx);
 
 #if LIBAVFORMAT_VERSION_INT >= AV_VERSION_INT(53,17,0)
 	avformat_close_input(&f);
@@ -626,7 +627,7 @@ ffmpeg_stream_tag(struct input_stream *is)
 #endif
 	mpd_ffmpeg_stream_close(stream);
 
-	return tag;
+	return true;
 }
 
 /**
@@ -745,7 +746,7 @@ const struct decoder_plugin ffmpeg_decoder_plugin = {
 	.name = "ffmpeg",
 	.init = ffmpeg_init,
 	.stream_decode = ffmpeg_decode,
-	.stream_tag = ffmpeg_stream_tag,
+	.scan_stream = ffmpeg_scan_stream,
 	.suffixes = ffmpeg_suffixes,
 	.mime_types = ffmpeg_mime_types
 };
diff --git a/src/decoder/ffmpeg_metadata.c b/src/decoder/ffmpeg_metadata.c
index d091afbc6..5325c1cae 100644
--- a/src/decoder/ffmpeg_metadata.c
+++ b/src/decoder/ffmpeg_metadata.c
@@ -19,8 +19,8 @@
 
 #include "config.h"
 #include "ffmpeg_metadata.h"
-#include "tag.h"
 #include "tag_table.h"
+#include "tag_handler.h"
 
 #undef G_LOG_DOMAIN
 #define G_LOG_DOMAIN "ffmpeg"
@@ -39,23 +39,27 @@ static const struct tag_table ffmpeg_tags[] = {
 };
 
 static void
-ffmpeg_copy_metadata(struct tag *tag, enum tag_type type,
-		     AVDictionary *m, const char *name)
+ffmpeg_copy_metadata(enum tag_type type,
+		     AVDictionary *m, const char *name,
+		     const struct tag_handler *handler, void *handler_ctx)
 {
 	AVDictionaryEntry *mt = NULL;
 
 	while ((mt = av_dict_get(m, name, mt, 0)) != NULL)
-		tag_add_item(tag, type, mt->value);
+		tag_handler_invoke_tag(handler, handler_ctx,
+				       type, mt->value);
 }
 
 void
-ffmpeg_copy_dictionary(struct tag *tag, AVDictionary *dict)
+ffmpeg_scan_dictionary(AVDictionary *dict,
+		       const struct tag_handler *handler, void *handler_ctx)
 {
 	for (unsigned i = 0; i < TAG_NUM_OF_ITEM_TYPES; ++i)
-		ffmpeg_copy_metadata(tag, i,
-				     dict, tag_item_names[i]);
+		ffmpeg_copy_metadata(i, dict, tag_item_names[i],
+				     handler, handler_ctx);
 
 	for (const struct tag_table *i = ffmpeg_tags;
 	     i->name != NULL; ++i)
-		ffmpeg_copy_metadata(tag, i->type, dict, i->name);
+		ffmpeg_copy_metadata(i->type, dict, i->name,
+				     handler, handler_ctx);
 }
diff --git a/src/decoder/ffmpeg_metadata.h b/src/decoder/ffmpeg_metadata.h
index fc10e1ebe..60658f479 100644
--- a/src/decoder/ffmpeg_metadata.h
+++ b/src/decoder/ffmpeg_metadata.h
@@ -32,9 +32,10 @@
 #define av_dict_get av_metadata_get
 #endif
 
-struct tag;
+struct tag_handler;
 
 void
-ffmpeg_copy_dictionary(struct tag *tag, AVDictionary *dict);
+ffmpeg_scan_dictionary(AVDictionary *dict,
+		       const struct tag_handler *handler, void *handler_ctx);
 
 #endif
diff --git a/src/decoder/flac_decoder_plugin.c b/src/decoder/flac_decoder_plugin.c
index 9dc1898d5..fb0b3502d 100644
--- a/src/decoder/flac_decoder_plugin.c
+++ b/src/decoder/flac_decoder_plugin.c
@@ -191,10 +191,11 @@ flac_write_cb(const FLAC__StreamDecoder *dec, const FLAC__Frame *frame,
 	return flac_common_write(data, frame, buf, nbytes);
 }
 
-static struct tag *
-flac_tag_dup(const char *file)
+static bool
+flac_scan_file(const char *file,
+	       const struct tag_handler *handler, void *handler_ctx)
 {
-	return flac_tag_load(file, NULL);
+	return flac_scan_file2(file, NULL, handler, handler_ctx);
 }
 
 /**
@@ -400,38 +401,33 @@ oggflac_init(G_GNUC_UNUSED const struct config_param *param)
 
 #if defined(FLAC_API_VERSION_CURRENT) && FLAC_API_VERSION_CURRENT > 7
 
-static struct tag *
-oggflac_tag_dup(const char *file)
+static bool
+oggflac_scan_file(const char *file,
+		  const struct tag_handler *handler, void *handler_ctx)
 {
-	struct tag *ret = NULL;
 	FLAC__Metadata_Iterator *it;
 	FLAC__StreamMetadata *block;
 	FLAC__Metadata_Chain *chain = FLAC__metadata_chain_new();
 
 	if (!(FLAC__metadata_chain_read_ogg(chain, file))) {
 		FLAC__metadata_chain_delete(chain);
-		return NULL;
+		return false;
 	}
 
 	it = FLAC__metadata_iterator_new();
 	FLAC__metadata_iterator_init(it, chain);
 
-	ret = tag_new();
 	do {
 		if (!(block = FLAC__metadata_iterator_get_block(it)))
 			break;
 
-		flac_tag_apply_metadata(ret, NULL, block);
+		flac_scan_metadata(NULL, block,
+				   handler, handler_ctx);
 	} while (FLAC__metadata_iterator_next(it));
 	FLAC__metadata_iterator_delete(it);
 
-	if (!tag_is_defined(ret)) {
-		tag_free(ret);
-		ret = NULL;
-	}
-
 	FLAC__metadata_chain_delete(chain);
-	return ret;
+	return true;
 }
 
 static void
@@ -464,7 +460,7 @@ const struct decoder_plugin oggflac_decoder_plugin = {
 	.init = oggflac_init,
 #if defined(FLAC_API_VERSION_CURRENT) && FLAC_API_VERSION_CURRENT > 7
 	.stream_decode = oggflac_decode,
-	.tag_dup = oggflac_tag_dup,
+	.scan_file = oggflac_scan_file,
 	.suffixes = oggflac_suffixes,
 	.mime_types = oggflac_mime_types
 #endif
@@ -484,7 +480,7 @@ static const char *const flac_mime_types[] = {
 const struct decoder_plugin flac_decoder_plugin = {
 	.name = "flac",
 	.stream_decode = flac_decode,
-	.tag_dup = flac_tag_dup,
+	.scan_file = flac_scan_file,
 	.suffixes = flac_suffixes,
 	.mime_types = flac_mime_types,
 };
diff --git a/src/decoder/flac_metadata.c b/src/decoder/flac_metadata.c
index 30dedda37..9e138ef96 100644
--- a/src/decoder/flac_metadata.c
+++ b/src/decoder/flac_metadata.c
@@ -21,6 +21,7 @@
 #include "flac_metadata.h"
 #include "replay_gain_info.h"
 #include "tag.h"
+#include "tag_handler.h"
 #include "tag_table.h"
 
 #include <glib.h>
@@ -164,17 +165,19 @@ flac_comment_value(const FLAC__StreamMetadata_VorbisComment_Entry *entry,
  * the comment value into the tag.
  */
 static bool
-flac_copy_comment(struct tag *tag,
-		  const FLAC__StreamMetadata_VorbisComment_Entry *entry,
+flac_copy_comment(const FLAC__StreamMetadata_VorbisComment_Entry *entry,
 		  const char *name, enum tag_type tag_type,
-		  const char *char_tnum)
+		  const char *char_tnum,
+		  const struct tag_handler *handler, void *handler_ctx)
 {
 	const char *value;
 	size_t value_length;
 
 	value = flac_comment_value(entry, name, char_tnum, &value_length);
 	if (value != NULL) {
-		tag_add_item_n(tag, tag_type, value, value_length);
+		char *p = g_strndup(value, value_length);
+		tag_handler_invoke_tag(handler, handler_ctx, tag_type, p);
+		g_free(p);
 		return true;
 	}
 
@@ -189,42 +192,47 @@ static const struct tag_table flac_tags[] = {
 };
 
 static void
-flac_parse_comment(struct tag *tag, const char *char_tnum,
-		   const FLAC__StreamMetadata_VorbisComment_Entry *entry)
+flac_scan_comment(const char *char_tnum,
+		  const FLAC__StreamMetadata_VorbisComment_Entry *entry,
+		  const struct tag_handler *handler, void *handler_ctx)
 {
-	assert(tag != NULL);
-
 	for (const struct tag_table *i = flac_tags; i->name != NULL; ++i)
-		if (flac_copy_comment(tag, entry, i->name, i->type, char_tnum))
+		if (flac_copy_comment(entry, i->name, i->type, char_tnum,
+				      handler, handler_ctx))
 			return;
 
 	for (unsigned i = 0; i < TAG_NUM_OF_ITEM_TYPES; ++i)
-		if (flac_copy_comment(tag, entry,
-				      tag_item_names[i], i, char_tnum))
+		if (flac_copy_comment(entry,
+				      tag_item_names[i], i, char_tnum,
+				      handler, handler_ctx))
 			return;
 }
 
-void
-flac_vorbis_comments_to_tag(struct tag *tag, const char *char_tnum,
-			    const FLAC__StreamMetadata_VorbisComment *comment)
+static void
+flac_scan_comments(const char *char_tnum,
+		   const FLAC__StreamMetadata_VorbisComment *comment,
+		   const struct tag_handler *handler, void *handler_ctx)
 {
 	for (unsigned i = 0; i < comment->num_comments; ++i)
-		flac_parse_comment(tag, char_tnum, &comment->comments[i]);
+		flac_scan_comment(char_tnum, &comment->comments[i],
+				  handler, handler_ctx);
 }
 
 void
-flac_tag_apply_metadata(struct tag *tag, const char *track,
-			const FLAC__StreamMetadata *block)
+flac_scan_metadata(const char *track,
+		   const FLAC__StreamMetadata *block,
+		   const struct tag_handler *handler, void *handler_ctx)
 {
 	switch (block->type) {
 	case FLAC__METADATA_TYPE_VORBIS_COMMENT:
-		flac_vorbis_comments_to_tag(tag, track,
-					    &block->data.vorbis_comment);
+		flac_scan_comments(track, &block->data.vorbis_comment,
+				   handler, handler_ctx);
 		break;
 
 	case FLAC__METADATA_TYPE_STREAMINFO:
 		if (block->data.stream_info.sample_rate > 0)
-			tag->time = flac_duration(&block->data.stream_info);
+			tag_handler_invoke_duration(handler, handler_ctx,
+						    flac_duration(&block->data.stream_info));
 		break;
 
 	default:
@@ -232,10 +240,18 @@ flac_tag_apply_metadata(struct tag *tag, const char *track,
 	}
 }
 
-struct tag *
-flac_tag_load(const char *file, const char *char_tnum)
+void
+flac_vorbis_comments_to_tag(struct tag *tag, const char *char_tnum,
+			    const FLAC__StreamMetadata_VorbisComment *comment)
+{
+	flac_scan_comments(char_tnum, comment,
+			   &add_tag_handler, tag);
+}
+
+bool
+flac_scan_file2(const char *file, const char *char_tnum,
+		const struct tag_handler *handler, void *handler_ctx)
 {
-	struct tag *tag;
 	FLAC__Metadata_SimpleIterator *it;
 	FLAC__StreamMetadata *block = NULL;
 
@@ -262,22 +278,30 @@ flac_tag_load(const char *file, const char *char_tnum)
 		g_debug("Reading '%s' metadata gave the following error: %s\n",
 			file, err);
 		FLAC__metadata_simple_iterator_delete(it);
-		return NULL;
+		return false;
 	}
 
-	tag = tag_new();
 	do {
 		block = FLAC__metadata_simple_iterator_get_block(it);
 		if (!block)
 			break;
 
-		flac_tag_apply_metadata(tag, char_tnum, block);
+		flac_scan_metadata(char_tnum, block, handler, handler_ctx);
 		FLAC__metadata_object_delete(block);
 	} while (FLAC__metadata_simple_iterator_next(it));
 
 	FLAC__metadata_simple_iterator_delete(it);
 
-	if (!tag_is_defined(tag)) {
+	return true;
+}
+
+struct tag *
+flac_tag_load(const char *file, const char *char_tnum)
+{
+	struct tag *tag = tag_new();
+
+	if (!flac_scan_file2(file, char_tnum, &add_tag_handler, tag) ||
+	    tag_is_empty(tag)) {
 		tag_free(tag);
 		tag = NULL;
 	}
diff --git a/src/decoder/flac_metadata.h b/src/decoder/flac_metadata.h
index 01bc1924a..3c463d5d6 100644
--- a/src/decoder/flac_metadata.h
+++ b/src/decoder/flac_metadata.h
@@ -24,6 +24,7 @@
 #include <stdbool.h>
 #include <FLAC/metadata.h>
 
+struct tag_handler;
 struct tag;
 struct replay_gain_info;
 
@@ -49,8 +50,13 @@ flac_vorbis_comments_to_tag(struct tag *tag, const char *char_tnum,
 			    const FLAC__StreamMetadata_VorbisComment *comment);
 
 void
-flac_tag_apply_metadata(struct tag *tag, const char *track,
-			const FLAC__StreamMetadata *block);
+flac_scan_metadata(const char *track,
+		   const FLAC__StreamMetadata *block,
+		   const struct tag_handler *handler, void *handler_ctx);
+
+bool
+flac_scan_file2(const char *file, const char *char_tnum,
+		const struct tag_handler *handler, void *handler_ctx);
 
 struct tag *
 flac_tag_load(const char *file, const char *char_tnum);
diff --git a/src/decoder/gme_decoder_plugin.c b/src/decoder/gme_decoder_plugin.c
index 8fdc39fd1..237a1deb1 100644
--- a/src/decoder/gme_decoder_plugin.c
+++ b/src/decoder/gme_decoder_plugin.c
@@ -2,6 +2,7 @@
 #include "../decoder_api.h"
 #include "audio_check.h"
 #include "uri.h"
+#include "tag_handler.h"
 
 #include <glib.h>
 #include <assert.h>
@@ -180,8 +181,9 @@ gme_file_decode(struct decoder *decoder, const char *path_fs)
 	gme_delete(emu);
 }
 
-static struct tag *
-gme_tag_dup(const char *path_fs)
+static bool
+gme_scan_file(const char *path_fs,
+	      const struct tag_handler *handler, void *handler_ctx)
 {
 	Music_Emu *emu;
 	gme_info_t *ti;
@@ -194,42 +196,49 @@ gme_tag_dup(const char *path_fs)
 	g_free(path_container);
 	if (gme_err != NULL) {
 		g_warning("%s", gme_err);
-		return NULL;
+		return false;
 	}
 	if((gme_err = gme_track_info(emu, &ti, song_num)) != NULL){
 		g_warning("%s", gme_err);
 		gme_delete(emu);
-		return NULL;
+		return false;
 	}
 
 	assert(ti != NULL);
 
-	struct tag *tag = tag_new();
-
 	if(ti->length > 0)
-		tag->time = ti->length / 1000;
+		tag_handler_invoke_duration(handler, handler_ctx,
+					    ti->length / 100);
+
 	if(ti->song != NULL){
 		if(gme_track_count(emu) > 1){
 			/* start numbering subtunes from 1 */
 			char *tag_title=g_strdup_printf("%s (%d/%d)",
 							ti->song, song_num+1, gme_track_count(emu));
-			tag_add_item(tag, TAG_TITLE, tag_title);
+			tag_handler_invoke_tag(handler, handler_ctx,
+					       TAG_TITLE, tag_title);
 			g_free(tag_title);
 		}else
-			tag_add_item(tag, TAG_TITLE, ti->song);
+			tag_handler_invoke_tag(handler, handler_ctx,
+					       TAG_TITLE, ti->song);
 	}
 	if(ti->author != NULL)
-		tag_add_item(tag, TAG_ARTIST, ti->author);
+		tag_handler_invoke_tag(handler, handler_ctx,
+				       TAG_ARTIST, ti->author);
 	if(ti->game != NULL)
-		tag_add_item(tag, TAG_ALBUM, ti->game);
+		tag_handler_invoke_tag(handler, handler_ctx,
+				       TAG_ALBUM, ti->game);
 	if(ti->comment != NULL)
-		tag_add_item(tag, TAG_COMMENT, ti->comment);
+		tag_handler_invoke_tag(handler, handler_ctx,
+				       TAG_COMMENT, ti->comment);
 	if(ti->copyright != NULL)
-		tag_add_item(tag, TAG_DATE, ti->copyright);
+		tag_handler_invoke_tag(handler, handler_ctx,
+				       TAG_DATE, ti->copyright);
 
 	gme_free_info(ti);
 	gme_delete(emu);
-	return tag;
+
+	return true;
 }
 
 static const char *const gme_suffixes[] = {
@@ -242,7 +251,7 @@ extern const struct decoder_plugin gme_decoder_plugin;
 const struct decoder_plugin gme_decoder_plugin = {
 	.name = "gme",
 	.file_decode = gme_file_decode,
-	.tag_dup = gme_tag_dup,
+	.scan_file = gme_scan_file,
 	.suffixes = gme_suffixes,
 	.container_scan = gme_container_scan,
 };
diff --git a/src/decoder/mad_decoder_plugin.c b/src/decoder/mad_decoder_plugin.c
index 8bf3f6546..a69284be5 100644
--- a/src/decoder/mad_decoder_plugin.c
+++ b/src/decoder/mad_decoder_plugin.c
@@ -22,6 +22,7 @@
 #include "conf.h"
 #include "tag_id3.h"
 #include "tag_rva2.h"
+#include "tag_handler.h"
 #include "audio_check.h"
 
 #include <assert.h>
@@ -1176,19 +1177,18 @@ mp3_decode(struct decoder *decoder, struct input_stream *input_stream)
 	mp3_data_finish(&data);
 }
 
-static struct tag *
-mad_decoder_stream_tag(struct input_stream *is)
+static bool
+mad_decoder_scan_stream(struct input_stream *is,
+			const struct tag_handler *handler, void *handler_ctx)
 {
-	struct tag *tag;
 	int total_time;
 
 	total_time = mad_decoder_total_file_time(is);
 	if (total_time < 0)
-		return NULL;
+		return false;
 
-	tag = tag_new();
-	tag->time = total_time;
-	return tag;
+	tag_handler_invoke_duration(handler, handler_ctx, total_time);
+	return true;
 }
 
 static const char *const mp3_suffixes[] = { "mp3", "mp2", NULL };
@@ -1198,7 +1198,7 @@ const struct decoder_plugin mad_decoder_plugin = {
 	.name = "mad",
 	.init = mp3_plugin_init,
 	.stream_decode = mp3_decode,
-	.stream_tag = mad_decoder_stream_tag,
+	.scan_stream = mad_decoder_scan_stream,
 	.suffixes = mp3_suffixes,
 	.mime_types = mp3_mime_types
 };
diff --git a/src/decoder/modplug_decoder_plugin.c b/src/decoder/modplug_decoder_plugin.c
index 9345dd240..21ee79e7e 100644
--- a/src/decoder/modplug_decoder_plugin.c
+++ b/src/decoder/modplug_decoder_plugin.c
@@ -19,6 +19,7 @@
 
 #include "config.h"
 #include "decoder_api.h"
+#include "tag_handler.h"
 
 #include <glib.h>
 #include <modplug.h>
@@ -149,34 +150,33 @@ mod_decode(struct decoder *decoder, struct input_stream *is)
 	ModPlug_Unload(f);
 }
 
-static struct tag *
-modplug_stream_tag(struct input_stream *is)
+static bool
+modplug_scan_stream(struct input_stream *is,
+		    const struct tag_handler *handler, void *handler_ctx)
 {
 	ModPlugFile *f;
-	struct tag *ret = NULL;
 	GByteArray *bdatas;
-	char *title;
 
 	bdatas = mod_loadfile(NULL, is);
 	if (!bdatas)
-		return NULL;
+		return false;
 
 	f = ModPlug_Load(bdatas->data, bdatas->len);
 	g_byte_array_free(bdatas, TRUE);
 	if (f == NULL)
-		return NULL;
+		return false;
 
-	ret = tag_new();
-	ret->time = ModPlug_GetLength(f) / 1000;
+	tag_handler_invoke_duration(handler, handler_ctx,
+				    ModPlug_GetLength(f) / 1000);
 
-	title = g_strdup(ModPlug_GetName(f));
-	if (title)
-		tag_add_item(ret, TAG_TITLE, title);
-	g_free(title);
+	const char *title = ModPlug_GetName(f);
+	if (title != NULL)
+		tag_handler_invoke_tag(handler, handler_ctx,
+				       TAG_TITLE, title);
 
 	ModPlug_Unload(f);
 
-	return ret;
+	return true;
 }
 
 static const char *const mod_suffixes[] = {
@@ -189,6 +189,6 @@ static const char *const mod_suffixes[] = {
 const struct decoder_plugin modplug_decoder_plugin = {
 	.name = "modplug",
 	.stream_decode = mod_decode,
-	.stream_tag = modplug_stream_tag,
+	.scan_stream = modplug_scan_stream,
 	.suffixes = mod_suffixes,
 };
diff --git a/src/decoder/mpcdec_decoder_plugin.c b/src/decoder/mpcdec_decoder_plugin.c
index 7864c0790..d4768b35b 100644
--- a/src/decoder/mpcdec_decoder_plugin.c
+++ b/src/decoder/mpcdec_decoder_plugin.c
@@ -20,6 +20,7 @@
 #include "config.h"
 #include "decoder_api.h"
 #include "audio_check.h"
+#include "tag_handler.h"
 
 #ifdef MPC_IS_OLD_API
 #include <mpcdec/mpcdec.h>
@@ -323,18 +324,17 @@ mpcdec_get_file_duration(struct input_stream *is)
 	return total_time;
 }
 
-static struct tag *
-mpcdec_stream_tag(struct input_stream *is)
+static bool
+mpcdec_scan_stream(struct input_stream *is,
+		   const struct tag_handler *handler, void *handler_ctx)
 {
 	float total_time = mpcdec_get_file_duration(is);
-	struct tag *tag;
 
 	if (total_time < 0)
-		return NULL;
+		return false;
 
-	tag = tag_new();
-	tag->time = total_time;
-	return tag;
+	tag_handler_invoke_duration(handler, handler_ctx, total_time);
+	return true;
 }
 
 static const char *const mpcdec_suffixes[] = { "mpc", NULL };
@@ -342,6 +342,6 @@ static const char *const mpcdec_suffixes[] = { "mpc", NULL };
 const struct decoder_plugin mpcdec_decoder_plugin = {
 	.name = "mpcdec",
 	.stream_decode = mpcdec_decode,
-	.stream_tag = mpcdec_stream_tag,
+	.scan_stream = mpcdec_scan_stream,
 	.suffixes = mpcdec_suffixes,
 };
diff --git a/src/decoder/mpg123_decoder_plugin.c b/src/decoder/mpg123_decoder_plugin.c
index 224f3db2a..657a9c889 100644
--- a/src/decoder/mpg123_decoder_plugin.c
+++ b/src/decoder/mpg123_decoder_plugin.c
@@ -20,6 +20,7 @@
 #include "config.h" /* must be first for large file support */
 #include "decoder_api.h"
 #include "audio_check.h"
+#include "tag_handler.h"
 
 #include <glib.h>
 
@@ -192,41 +193,40 @@ mpd_mpg123_file_decode(struct decoder *decoder, const char *path_fs)
 	mpg123_delete(handle);
 }
 
-static struct tag *
-mpd_mpg123_tag_dup(const char *path_fs)
+static bool
+mpd_mpg123_scan_file(const char *path_fs,
+		     const struct tag_handler *handler, void *handler_ctx)
 {
 	struct audio_format audio_format;
 	mpg123_handle *handle;
 	int error;
 	off_t num_samples;
-	struct tag *tag;
 
 	handle = mpg123_new(NULL, &error);
 	if (handle == NULL) {
 		g_warning("mpg123_new() failed: %s",
 			  mpg123_plain_strerror(error));
-		return NULL;
+		return false;
 	}
 
 	if (!mpd_mpg123_open(handle, path_fs, &audio_format)) {
 		mpg123_delete(handle);
-		return NULL;
+		return false;
 	}
 
 	num_samples = mpg123_length(handle);
 	if (num_samples <= 0) {
 		mpg123_delete(handle);
-		return NULL;
+		return false;
 	}
 
-	tag = tag_new();
-
-	tag->time = num_samples / audio_format.sample_rate;
-
 	/* ID3 tag support not yet implemented */
 
 	mpg123_delete(handle);
-	return tag;
+
+	tag_handler_invoke_duration(handler, handler_ctx,
+				    num_samples / audio_format.sample_rate);
+	return true;
 }
 
 static const char *const mpg123_suffixes[] = {
@@ -240,6 +240,6 @@ const struct decoder_plugin mpg123_decoder_plugin = {
 	.finish = mpd_mpg123_finish,
 	.file_decode = mpd_mpg123_file_decode,
 	/* streaming not yet implemented */
-	.tag_dup = mpd_mpg123_tag_dup,
+	.scan_file = mpd_mpg123_scan_file,
 	.suffixes = mpg123_suffixes,
 };
diff --git a/src/decoder/sidplay_decoder_plugin.cxx b/src/decoder/sidplay_decoder_plugin.cxx
index 9aeec8b51..c4ef20496 100644
--- a/src/decoder/sidplay_decoder_plugin.cxx
+++ b/src/decoder/sidplay_decoder_plugin.cxx
@@ -21,6 +21,7 @@
 
 extern "C" {
 #include "../decoder_api.h"
+#include "tag_handler.h"
 }
 
 #include <errno.h>
@@ -336,8 +337,9 @@ sidplay_file_decode(struct decoder *decoder, const char *path_fs)
 	} while (cmd != DECODE_COMMAND_STOP);
 }
 
-static struct tag *
-sidplay_tag_dup(const char *path_fs)
+static bool
+sidplay_scan_file(const char *path_fs,
+		  const struct tag_handler *handler, void *handler_ctx)
 {
 	int song_num=get_song_num(path_fs);
 	char *path_container=get_container_name(path_fs);
@@ -345,10 +347,9 @@ sidplay_tag_dup(const char *path_fs)
 	SidTune tune(path_container, NULL, true);
 	g_free(path_container);
 	if (!tune)
-		return NULL;
+		return false;
 
 	const SidTuneInfo &info = tune.getInfo();
-	struct tag *tag = tag_new();
 
 	/* title */
 	const char *title;
@@ -360,25 +361,28 @@ sidplay_tag_dup(const char *path_fs)
 	if(info.songs>1) {
 		char *tag_title=g_strdup_printf("%s (%d/%d)",
 			title, song_num, info.songs);
-		tag_add_item(tag, TAG_TITLE, tag_title);
+		tag_handler_invoke_tag(handler, handler_ctx,
+				       TAG_TITLE, tag_title);
 		g_free(tag_title);
 	} else
-		tag_add_item(tag, TAG_TITLE, title);
+		tag_handler_invoke_tag(handler, handler_ctx, TAG_TITLE, title);
 
 	/* artist */
 	if (info.numberOfInfoStrings > 1 && info.infoString[1] != NULL)
-		tag_add_item(tag, TAG_ARTIST, info.infoString[1]);
+		tag_handler_invoke_tag(handler, handler_ctx, TAG_ARTIST,
+				       info.infoString[1]);
 
 	/* track */
 	char *track=g_strdup_printf("%d", song_num);
-	tag_add_item(tag, TAG_TRACK, track);
+	tag_handler_invoke_tag(handler, handler_ctx, TAG_TRACK, track);
 	g_free(track);
 
 	/* time */
 	int song_len=get_song_length(path_fs);
-	if(song_len!=-1) tag->time=song_len;
+	if (song_len >= 0)
+		tag_handler_invoke_duration(handler, handler_ctx, song_len);
 
-	return tag;
+	return true;
 }
 
 static char *
@@ -421,7 +425,7 @@ const struct decoder_plugin sidplay_decoder_plugin = {
 	sidplay_finish,
 	NULL, /* stream_decode() */
 	sidplay_file_decode,
-	sidplay_tag_dup,
+	sidplay_scan_file,
 	NULL, /* stream_tag() */
 	sidplay_container_scan,
 	sidplay_suffixes,
diff --git a/src/decoder/sndfile_decoder_plugin.c b/src/decoder/sndfile_decoder_plugin.c
index 25952dfd5..8dd98236f 100644
--- a/src/decoder/sndfile_decoder_plugin.c
+++ b/src/decoder/sndfile_decoder_plugin.c
@@ -20,6 +20,7 @@
 #include "config.h"
 #include "decoder_api.h"
 #include "audio_check.h"
+#include "tag_handler.h"
 
 #include <sndfile.h>
 
@@ -172,44 +173,47 @@ sndfile_stream_decode(struct decoder *decoder, struct input_stream *is)
 	sf_close(sf);
 }
 
-static struct tag *
-sndfile_tag_dup(const char *path_fs)
+static bool
+sndfile_scan_file(const char *path_fs,
+		  const struct tag_handler *handler, void *handler_ctx)
 {
 	SNDFILE *sf;
 	SF_INFO info;
-	struct tag *tag;
 	const char *p;
 
 	info.format = 0;
 
 	sf = sf_open(path_fs, SFM_READ, &info);
 	if (sf == NULL)
-		return NULL;
+		return false;
 
 	if (!audio_valid_sample_rate(info.samplerate)) {
 		sf_close(sf);
 		g_warning("Invalid sample rate in %s\n", path_fs);
-		return NULL;
+		return false;
 	}
 
-	tag = tag_new();
-	tag->time = info.frames / info.samplerate;
+	tag_handler_invoke_duration(handler, handler_ctx,
+				    info.frames / info.samplerate);
 
 	p = sf_get_string(sf, SF_STR_TITLE);
 	if (p != NULL)
-		tag_add_item(tag, TAG_TITLE, p);
+		tag_handler_invoke_tag(handler, handler_ctx,
+				       TAG_TITLE, p);
 
 	p = sf_get_string(sf, SF_STR_ARTIST);
 	if (p != NULL)
-		tag_add_item(tag, TAG_ARTIST, p);
+		tag_handler_invoke_tag(handler, handler_ctx,
+				       TAG_ARTIST, p);
 
 	p = sf_get_string(sf, SF_STR_DATE);
 	if (p != NULL)
-		tag_add_item(tag, TAG_DATE, p);
+		tag_handler_invoke_tag(handler, handler_ctx,
+				       TAG_DATE, p);
 
 	sf_close(sf);
 
-	return tag;
+	return true;
 }
 
 static const char *const sndfile_suffixes[] = {
@@ -245,7 +249,7 @@ static const char *const sndfile_mime_types[] = {
 const struct decoder_plugin sndfile_decoder_plugin = {
 	.name = "sndfile",
 	.stream_decode = sndfile_stream_decode,
-	.tag_dup = sndfile_tag_dup,
+	.scan_file = sndfile_scan_file,
 	.suffixes = sndfile_suffixes,
 	.mime_types = sndfile_mime_types,
 };
diff --git a/src/decoder/vorbis_comments.c b/src/decoder/vorbis_comments.c
index 9145507dc..e94ee3d0a 100644
--- a/src/decoder/vorbis_comments.c
+++ b/src/decoder/vorbis_comments.c
@@ -21,6 +21,7 @@
 #include "vorbis_comments.h"
 #include "tag.h"
 #include "tag_table.h"
+#include "tag_handler.h"
 #include "replay_gain_info.h"
 
 #include <glib.h>
@@ -79,14 +80,15 @@ vorbis_comments_to_replay_gain(struct replay_gain_info *rgi, char **comments)
  * the comment value into the tag.
  */
 static bool
-vorbis_copy_comment(struct tag *tag, const char *comment,
-		    const char *name, enum tag_type tag_type)
+vorbis_copy_comment(const char *comment,
+		    const char *name, enum tag_type tag_type,
+		    const struct tag_handler *handler, void *handler_ctx)
 {
 	const char *value;
 
 	value = vorbis_comment_value(comment, name);
 	if (value != NULL) {
-		tag_add_item(tag, tag_type, value);
+		tag_handler_invoke_tag(handler, handler_ctx, tag_type, value);
 		return true;
 	}
 
@@ -101,27 +103,36 @@ static const struct tag_table vorbis_tags[] = {
 };
 
 static void
-vorbis_parse_comment(struct tag *tag, const char *comment)
+vorbis_scan_comment(const char *comment,
+		    const struct tag_handler *handler, void *handler_ctx)
 {
-	assert(tag != NULL);
-
 	for (const struct tag_table *i = vorbis_tags; i->name != NULL; ++i)
-		if (vorbis_copy_comment(tag, comment, i->name, i->type))
+		if (vorbis_copy_comment(comment, i->name, i->type,
+					handler, handler_ctx))
 			return;
 
 	for (unsigned i = 0; i < TAG_NUM_OF_ITEM_TYPES; ++i)
-		if (vorbis_copy_comment(tag, comment,
-					tag_item_names[i], i))
+		if (vorbis_copy_comment(comment,
+					tag_item_names[i], i,
+					handler, handler_ctx))
 			return;
 }
 
+void
+vorbis_comments_scan(char **comments,
+		     const struct tag_handler *handler, void *handler_ctx)
+{
+	while (*comments)
+		vorbis_scan_comment(*comments++,
+				    handler, handler_ctx);
+
+}
+
 struct tag *
 vorbis_comments_to_tag(char **comments)
 {
 	struct tag *tag = tag_new();
-
-	while (*comments)
-		vorbis_parse_comment(tag, *comments++);
+	vorbis_comments_scan(comments, &add_tag_handler, tag);
 
 	if (tag_is_empty(tag)) {
 		tag_free(tag);
diff --git a/src/decoder/vorbis_comments.h b/src/decoder/vorbis_comments.h
index 5d2c65e44..c15096930 100644
--- a/src/decoder/vorbis_comments.h
+++ b/src/decoder/vorbis_comments.h
@@ -25,10 +25,15 @@
 #include <stdbool.h>
 
 struct replay_gain_info;
+struct tag_handler;
 
 bool
 vorbis_comments_to_replay_gain(struct replay_gain_info *rgi, char **comments);
 
+void
+vorbis_comments_scan(char **comments,
+		     const struct tag_handler *handler, void *handler_ctx);
+
 struct tag *
 vorbis_comments_to_tag(char **comments);
 
diff --git a/src/decoder/vorbis_decoder_plugin.c b/src/decoder/vorbis_decoder_plugin.c
index f34693844..15cdc0ca9 100644
--- a/src/decoder/vorbis_decoder_plugin.c
+++ b/src/decoder/vorbis_decoder_plugin.c
@@ -22,6 +22,7 @@
 #include "_ogg_common.h"
 #include "audio_check.h"
 #include "uri.h"
+#include "tag_handler.h"
 
 #ifndef HAVE_TREMOR
 #define OV_EXCLUDE_STATIC_CALLBACKS
@@ -268,24 +269,24 @@ vorbis_stream_decode(struct decoder *decoder,
 	ov_clear(&vf);
 }
 
-static struct tag *
-vorbis_stream_tag(struct input_stream *is)
+static bool
+vorbis_scan_stream(struct input_stream *is,
+		   const struct tag_handler *handler, void *handler_ctx)
 {
 	struct vorbis_input_stream vis;
 	OggVorbis_File vf;
 
 	if (!vorbis_is_open(&vis, &vf, NULL, is))
-		return NULL;
+		return false;
 
-	struct tag *tag = vorbis_comments_to_tag(ov_comment(&vf, -1)->user_comments);
+	tag_handler_invoke_duration(handler, handler_ctx,
+				    (int)(ov_time_total(&vf, -1) + 0.5));
 
-	if (tag == NULL)
-		tag = tag_new();
-	tag->time = (int)(ov_time_total(&vf, -1) + 0.5);
+	vorbis_comments_scan(ov_comment(&vf, -1)->user_comments,
+			     handler, handler_ctx);
 
 	ov_clear(&vf);
-
-	return tag;
+	return true;
 }
 
 static const char *const vorbis_suffixes[] = {
@@ -307,7 +308,7 @@ static const char *const vorbis_mime_types[] = {
 const struct decoder_plugin vorbis_decoder_plugin = {
 	.name = "vorbis",
 	.stream_decode = vorbis_stream_decode,
-	.stream_tag = vorbis_stream_tag,
+	.scan_stream = vorbis_scan_stream,
 	.suffixes = vorbis_suffixes,
 	.mime_types = vorbis_mime_types
 };
diff --git a/src/decoder/wavpack_decoder_plugin.c b/src/decoder/wavpack_decoder_plugin.c
index 4945b75ce..794b969c4 100644
--- a/src/decoder/wavpack_decoder_plugin.c
+++ b/src/decoder/wavpack_decoder_plugin.c
@@ -22,6 +22,7 @@
 #include "audio_check.h"
 #include "path.h"
 #include "utils.h"
+#include "tag_handler.h"
 
 #include <wavpack/wavpack.h>
 #include <glib.h>
@@ -275,11 +276,11 @@ wavpack_replaygain(struct replay_gain_info *replay_gain_info,
 /*
  * Reads metainfo from the specified file.
  */
-static struct tag *
-wavpack_tagdup(const char *fname)
+static bool
+wavpack_scan_file(const char *fname,
+		  const struct tag_handler *handler, void *handler_ctx)
 {
 	WavpackContext *wpc;
-	struct tag *tag;
 	char error[ERRORLEN];
 	char *s;
 	int size, allocated_size;
@@ -290,12 +291,12 @@ wavpack_tagdup(const char *fname)
 			"failed to open WavPack file \"%s\": %s\n",
 			fname, error
 		);
-		return NULL;
+		return false;
 	}
 
-	tag = tag_new();
-	tag->time = WavpackGetNumSamples(wpc);
-	tag->time /= WavpackGetSampleRate(wpc);
+	tag_handler_invoke_duration(handler, handler_ctx,
+				    WavpackGetNumSamples(wpc) /
+				    WavpackGetSampleRate(wpc));
 
 	allocated_size = 0;
 	s = NULL;
@@ -315,7 +316,8 @@ wavpack_tagdup(const char *fname)
 			}
 
 			WavpackGetTagItem(wpc, tagtypes[i].name, s, size);
-			tag_add_item(tag, tagtypes[i].type, s);
+			tag_handler_invoke_tag(handler, handler_ctx,
+					       tagtypes[i].type, s);
 		}
 	}
 
@@ -323,7 +325,7 @@ wavpack_tagdup(const char *fname)
 
 	WavpackCloseFile(wpc);
 
-	return tag;
+	return true;
 }
 
 /*
@@ -576,7 +578,7 @@ const struct decoder_plugin wavpack_decoder_plugin = {
 	.name = "wavpack",
 	.stream_decode = wavpack_streamdecode,
 	.file_decode = wavpack_filedecode,
-	.tag_dup = wavpack_tagdup,
+	.scan_file = wavpack_scan_file,
 	.suffixes = wavpack_suffixes,
 	.mime_types = wavpack_mime_types
 };
diff --git a/src/decoder/wildmidi_decoder_plugin.c b/src/decoder/wildmidi_decoder_plugin.c
index 5bc36b4e3..a2224940d 100644
--- a/src/decoder/wildmidi_decoder_plugin.c
+++ b/src/decoder/wildmidi_decoder_plugin.c
@@ -19,6 +19,7 @@
 
 #include "config.h"
 #include "decoder_api.h"
+#include "tag_handler.h"
 
 #include <glib.h>
 
@@ -111,25 +112,26 @@ wildmidi_file_decode(struct decoder *decoder, const char *path_fs)
 	WildMidi_Close(wm);
 }
 
-static struct tag *
-wildmidi_tag_dup(const char *path_fs)
+static bool
+wildmidi_scan_file(const char *path_fs,
+		   const struct tag_handler *handler, void *handler_ctx)
 {
 	midi *wm = WildMidi_Open(path_fs);
 	if (wm == NULL)
-		return NULL;
+		return false;
 
 	const struct _WM_Info *info = WildMidi_GetInfo(wm);
 	if (info == NULL) {
 		WildMidi_Close(wm);
-		return NULL;
+		return false;
 	}
 
-	struct tag *tag = tag_new();
-	tag->time = info->approx_total_samples / WILDMIDI_SAMPLE_RATE;
+	int duration = info->approx_total_samples / WILDMIDI_SAMPLE_RATE;
+	tag_handler_invoke_duration(handler, handler_ctx, duration);
 
 	WildMidi_Close(wm);
 
-	return tag;
+	return true;
 }
 
 static const char *const wildmidi_suffixes[] = {
@@ -142,6 +144,6 @@ const struct decoder_plugin wildmidi_decoder_plugin = {
 	.init = wildmidi_init,
 	.finish = wildmidi_finish,
 	.file_decode = wildmidi_file_decode,
-	.tag_dup = wildmidi_tag_dup,
+	.scan_file = wildmidi_scan_file,
 	.suffixes = wildmidi_suffixes,
 };