tag/Handler: convert to class with virtual methods

8 files changed, 130 insertions, 139 deletions

diff --git a/src/tag/ApeTag.cxx b/src/tag/ApeTag.cxx
index ff143e7cd..6d8203dc2 100644
--- a/src/tag/ApeTag.cxx
+++ b/src/tag/ApeTag.cxx
@@ -76,7 +76,7 @@ ForEachValue(const char *value, const char *end, C &&callback)
 static bool
 tag_ape_import_item(unsigned long flags,
 		    const char *key, StringView value,
-		    const TagHandler &handler, void *handler_ctx)
+		    TagHandler &handler) noexcept
 {
 	/* we only care about utf-8 text tags */
 	if ((flags & (0x3 << 1)) != 0)
@@ -85,36 +85,31 @@ tag_ape_import_item(unsigned long flags,
 	const auto begin = value.begin();
 	const auto end = value.end();
 
-	if (handler.pair != nullptr)
-		ForEachValue(begin, end, [handler, handler_ctx,
-					  key](const char *_value) {
-				handler.pair(key, _value, handler_ctx);
+	if (handler.WantPair())
+		ForEachValue(begin, end, [&handler, key](const char *_value) {
+				handler.OnPair(key, _value);
 			});
 
 	TagType type = tag_ape_name_parse(key);
 	if (type == TAG_NUM_OF_ITEM_TYPES)
 		return false;
 
-	ForEachValue(begin, end, [handler, handler_ctx,
-				  type](const char *_value) {
-			tag_handler_invoke_tag(handler, handler_ctx,
-					       type, _value);
+	ForEachValue(begin, end, [&handler, type](const char *_value) {
+			handler.OnTag(type, _value);
 		});
 
 	return true;
 }
 
 bool
-tag_ape_scan2(InputStream &is,
-	      const TagHandler &handler, void *handler_ctx)
+tag_ape_scan2(InputStream &is, TagHandler &handler) noexcept
 {
 	bool recognized = false;
 
-	auto callback = [handler, handler_ctx, &recognized]
+	auto callback = [&handler, &recognized]
 		(unsigned long flags, const char *key,
 		 StringView value) {
-		recognized |= tag_ape_import_item(flags, key, value,
-						  handler, handler_ctx);
+		recognized |= tag_ape_import_item(flags, key, value, handler);
 		return true;
 	};
 
diff --git a/src/tag/ApeTag.hxx b/src/tag/ApeTag.hxx
index 93b8ba126..9d467608d 100644
--- a/src/tag/ApeTag.hxx
+++ b/src/tag/ApeTag.hxx
@@ -20,10 +20,8 @@
 #ifndef MPD_APE_TAG_HXX
 #define MPD_APE_TAG_HXX
 
-#include "Table.hxx"
-
 class InputStream;
-struct TagHandler;
+class TagHandler;
 
 /**
  * Scan the APE tags of a stream.
@@ -31,7 +29,6 @@ struct TagHandler;
  * @param path_fs the path of the file in filesystem encoding
  */
 bool
-tag_ape_scan2(InputStream &is,
-	      const TagHandler &handler, void *handler_ctx);
+tag_ape_scan2(InputStream &is, TagHandler &handler) noexcept;
 
 #endif
diff --git a/src/tag/Generic.cxx b/src/tag/Generic.cxx
index 3aff10c79..1ce736505 100644
--- a/src/tag/Generic.cxx
+++ b/src/tag/Generic.cxx
@@ -30,9 +30,9 @@
 #include <exception>
 
 bool
-ScanGenericTags(InputStream &is, const TagHandler &handler, void *ctx)
+ScanGenericTags(InputStream &is, TagHandler &handler) noexcept
 {
-	if (tag_ape_scan2(is, handler, ctx))
+	if (tag_ape_scan2(is, handler))
 		return true;
 
 #ifdef ENABLE_ID3TAG
@@ -42,19 +42,19 @@ ScanGenericTags(InputStream &is, const TagHandler &handler, void *ctx)
 		return false;
 	}
 
-	return tag_id3_scan(is, handler, ctx);
+	return tag_id3_scan(is, handler);
 #else
 	return false;
 #endif
 }
 
 bool
-ScanGenericTags(Path path, const TagHandler &handler, void *ctx)
+ScanGenericTags(Path path, TagHandler &handler) noexcept
 try {
 	Mutex mutex;
 
 	auto is = OpenLocalInputStream(path, mutex);
-	return ScanGenericTags(*is, handler, ctx);
+	return ScanGenericTags(*is, handler);
 } catch (...) {
 	LogError(std::current_exception());
 	return false;
diff --git a/src/tag/Generic.hxx b/src/tag/Generic.hxx
index 568b0b733..415cd2325 100644
--- a/src/tag/Generic.hxx
+++ b/src/tag/Generic.hxx
@@ -22,7 +22,7 @@
 
 #include "check.h"
 
-struct TagHandler;
+class TagHandler;
 class InputStream;
 class Path;
 
@@ -31,12 +31,12 @@ class Path;
  * stream does not need to be rewound.
  */
 bool
-ScanGenericTags(InputStream &is, const TagHandler &handler, void *ctx);
+ScanGenericTags(InputStream &is, TagHandler &handler) noexcept;
 
 /**
  * Attempts to scan APE or ID3 tags from the specified file.
  */
 bool
-ScanGenericTags(Path path, const TagHandler &handler, void *ctx);
+ScanGenericTags(Path path, TagHandler &handler) noexcept;
 
 #endif
diff --git a/src/tag/Handler.cxx b/src/tag/Handler.cxx
index 7c4210f7d..ad8404161 100644
--- a/src/tag/Handler.cxx
+++ b/src/tag/Handler.cxx
@@ -25,19 +25,15 @@
 
 #include <stdlib.h>
 
-static void
-add_tag_duration(SongTime duration, void *ctx)
+void
+AddTagHandler::OnDuration(SongTime duration) noexcept
 {
-	TagBuilder &tag = *(TagBuilder *)ctx;
-
 	tag.SetDuration(duration);
 }
 
-static void
-add_tag_tag(TagType type, const char *value, void *ctx)
+void
+AddTagHandler::OnTag(TagType type, const char *value) noexcept
 {
-	TagBuilder &tag = *(TagBuilder *)ctx;
-
 	if (type == TAG_TRACK || type == TAG_DISC) {
 		/* filter out this extra data and leading zeroes */
 		char *end;
@@ -48,24 +44,10 @@ add_tag_tag(TagType type, const char *value, void *ctx)
 		tag.AddItem(type, value);
 }
 
-const TagHandler add_tag_handler = {
-	add_tag_duration,
-	add_tag_tag,
-	nullptr,
-};
-
-static void
-full_tag_pair(const char *name, gcc_unused const char *value, void *ctx)
+void
+FullTagHandler::OnPair(const char *name, gcc_unused const char *value) noexcept
 {
-	TagBuilder &tag = *(TagBuilder *)ctx;
-
 	if (StringEqualsCaseASCII(name, "cuesheet"))
 		tag.SetHasPlaylist(true);
 }
 
-const TagHandler full_tag_handler = {
-	add_tag_duration,
-	add_tag_tag,
-	full_tag_pair,
-};
-
diff --git a/src/tag/Handler.hxx b/src/tag/Handler.hxx
index cec04e91d..944c73114 100644
--- a/src/tag/Handler.hxx
+++ b/src/tag/Handler.hxx
@@ -23,19 +23,45 @@
 #include "check.h"
 #include "Type.h"
 #include "Chrono.hxx"
+#include "Compiler.h"
 
-#include <assert.h>
+class TagBuilder;
 
 /**
- * A callback table for receiving metadata of a song.
+ * An interface for receiving metadata of a song.
  */
-struct TagHandler {
+class TagHandler {
+	const unsigned want_mask;
+
+public:
+	static constexpr unsigned WANT_DURATION = 0x1;
+	static constexpr unsigned WANT_TAG = 0x2;
+	static constexpr unsigned WANT_PAIR = 0x4;
+
+	explicit TagHandler(unsigned _want_mask) noexcept
+		:want_mask(_want_mask) {}
+
+	TagHandler(const TagHandler &) = delete;
+	TagHandler &operator=(const TagHandler &) = delete;
+
+	bool WantDuration() const noexcept {
+		return want_mask & WANT_DURATION;
+	}
+
+	bool WantTag() const noexcept {
+		return want_mask & WANT_TAG;
+	}
+
+	bool WantPair() const noexcept {
+		return want_mask & WANT_PAIR;
+	}
+
 	/**
 	 * Declare the duration of a song.  Do not call
 	 * this when the duration could not be determined, because
 	 * there is no magic value for "unknown duration".
 	 */
-	void (*duration)(SongTime duration, void *ctx);
+	virtual void OnDuration(SongTime duration) noexcept = 0;
 
 	/**
 	 * A tag has been read.
@@ -43,56 +69,57 @@ struct TagHandler {
 	 * @param the value of the tag; the pointer will become
 	 * invalid after returning
 	 */
-	void (*tag)(TagType type, const char *value, void *ctx);
+	virtual void OnTag(TagType type, const char *value) noexcept = 0;
 
 	/**
 	 * A name-value pair has been read.  It is the codec specific
 	 * representation of tags.
 	 */
-	void (*pair)(const char *key, const char *value, void *ctx);
+	virtual void OnPair(const char *key, const char *value) noexcept = 0;
 };
 
-static inline void
-tag_handler_invoke_duration(const TagHandler &handler, void *ctx,
-			    SongTime duration) noexcept
-{
-	if (handler.duration != nullptr)
-		handler.duration(duration, ctx);
-}
-
-static inline void
-tag_handler_invoke_tag(const TagHandler &handler, void *ctx,
-		       TagType type, const char *value) noexcept
-{
-	assert((unsigned)type < TAG_NUM_OF_ITEM_TYPES);
-	assert(value != nullptr);
-
-	if (handler.tag != nullptr)
-		handler.tag(type, value, ctx);
-}
-
-static inline void
-tag_handler_invoke_pair(const TagHandler &handler, void *ctx,
-			const char *name, const char *value) noexcept
-{
-	assert(name != nullptr);
-	assert(value != nullptr);
-
-	if (handler.pair != nullptr)
-		handler.pair(name, value, ctx);
-}
+class NullTagHandler : public TagHandler {
+public:
+	explicit NullTagHandler(unsigned _want_mask) noexcept
+		:TagHandler(_want_mask) {}
+
+	void OnDuration(gcc_unused SongTime duration) noexcept override {}
+	void OnTag(gcc_unused TagType type,
+		   gcc_unused const char *value) noexcept override {}
+	void OnPair(gcc_unused const char *key,
+		    gcc_unused const char *value) noexcept override {}
+};
 
 /**
- * This #TagHandler implementation adds tag values to a #TagBuilder object
- * (casted from the context pointer).
+ * This #TagHandler implementation adds tag values to a #TagBuilder
+ * object.
  */
-extern const TagHandler add_tag_handler;
+class AddTagHandler : public NullTagHandler {
+protected:
+	TagBuilder &tag;
+
+	AddTagHandler(unsigned _want_mask, TagBuilder &_builder) noexcept
+		:NullTagHandler(_want_mask), tag(_builder) {}
+
+public:
+	explicit AddTagHandler(TagBuilder &_builder) noexcept
+		:AddTagHandler(WANT_DURATION|WANT_TAG, _builder) {}
+
+	void OnDuration(SongTime duration) noexcept override;
+	void OnTag(TagType type, const char *value) noexcept override;
+};
 
 /**
  * This #TagHandler implementation adds tag values to a #TagBuilder object
  * (casted from the context pointer), and supports the has_playlist
  * attribute.
  */
-extern const TagHandler full_tag_handler;
+class FullTagHandler : public AddTagHandler {
+public:
+	explicit FullTagHandler(TagBuilder &_builder) noexcept
+		:AddTagHandler(WANT_DURATION|WANT_TAG|WANT_PAIR, _builder) {}
+
+	void OnPair(const char *key, const char *value) noexcept override;
+};
 
 #endif
diff --git a/src/tag/Id3Scan.cxx b/src/tag/Id3Scan.cxx
index cd35386e4..aa1caba69 100644
--- a/src/tag/Id3Scan.cxx
+++ b/src/tag/Id3Scan.cxx
@@ -100,7 +100,7 @@ import_id3_string(const id3_ucs4_t *ucs4)
 static void
 tag_id3_import_text_frame(const struct id3_frame *frame,
 			  TagType type,
-			  const TagHandler &handler, void *handler_ctx)
+			  TagHandler &handler) noexcept
 {
 	if (frame->nfields != 2)
 		return;
@@ -133,8 +133,7 @@ tag_id3_import_text_frame(const struct id3_frame *frame,
 
 		AtScopeExit(utf8) { free(utf8); };
 
-		tag_handler_invoke_tag(handler, handler_ctx,
-				       type, (const char *)utf8);
+		handler.OnTag(type, (const char *)utf8);
 	}
 }
 
@@ -144,13 +143,13 @@ tag_id3_import_text_frame(const struct id3_frame *frame,
  */
 static void
 tag_id3_import_text(struct id3_tag *tag, const char *id, TagType type,
-		    const TagHandler &handler, void *handler_ctx)
+		    TagHandler &handler) noexcept
 {
 	const struct id3_frame *frame;
 	for (unsigned i = 0;
 	     (frame = id3_tag_findframe(tag, id, i)) != nullptr; ++i)
 		tag_id3_import_text_frame(frame, type,
-					  handler, handler_ctx);
+					  handler);
 }
 
 /**
@@ -164,8 +163,7 @@ tag_id3_import_text(struct id3_tag *tag, const char *id, TagType type,
  */
 static void
 tag_id3_import_comment_frame(const struct id3_frame *frame, TagType type,
-			     const TagHandler &handler,
-			     void *handler_ctx)
+			     TagHandler &handler) noexcept
 {
 	if (frame->nfields != 4)
 		return;
@@ -185,7 +183,7 @@ tag_id3_import_comment_frame(const struct id3_frame *frame, TagType type,
 
 	AtScopeExit(utf8) { free(utf8); };
 
-	tag_handler_invoke_tag(handler, handler_ctx, type, (const char *)utf8);
+	handler.OnTag(type, (const char *)utf8);
 }
 
 /**
@@ -194,13 +192,13 @@ tag_id3_import_comment_frame(const struct id3_frame *frame, TagType type,
  */
 static void
 tag_id3_import_comment(struct id3_tag *tag, const char *id, TagType type,
-		       const TagHandler &handler, void *handler_ctx)
+		       TagHandler &handler) noexcept
 {
 	const struct id3_frame *frame;
 	for (unsigned i = 0;
 	     (frame = id3_tag_findframe(tag, id, i)) != nullptr; ++i)
 		tag_id3_import_comment_frame(frame, type,
-					     handler, handler_ctx);
+					     handler);
 }
 
 /**
@@ -220,8 +218,7 @@ tag_id3_parse_txxx_name(const char *name) noexcept
  */
 static void
 tag_id3_import_musicbrainz(struct id3_tag *id3_tag,
-			   const TagHandler &handler,
-			   void *handler_ctx)
+			   TagHandler &handler) noexcept
 {
 	for (unsigned i = 0;; ++i) {
 		const id3_frame *frame = id3_tag_findframe(id3_tag, "TXXX", i);
@@ -240,15 +237,12 @@ tag_id3_import_musicbrainz(struct id3_tag *id3_tag,
 
 		AtScopeExit(value) { free(value); };
 
-		tag_handler_invoke_pair(handler, handler_ctx,
-					(const char *)name,
-					(const char *)value);
+		handler.OnPair((const char *)name, (const char *)value);
 
 		TagType type = tag_id3_parse_txxx_name((const char*)name);
 
 		if (type != TAG_NUM_OF_ITEM_TYPES)
-			tag_handler_invoke_tag(handler, handler_ctx,
-					       type, (const char*)value);
+			handler.OnTag(type, (const char*)value);
 	}
 }
 
@@ -257,7 +251,7 @@ tag_id3_import_musicbrainz(struct id3_tag *id3_tag,
  */
 static void
 tag_id3_import_ufid(struct id3_tag *id3_tag,
-		    const TagHandler &handler, void *handler_ctx)
+		    TagHandler &handler) noexcept
 {
 	for (unsigned i = 0;; ++i) {
 		const id3_frame *frame = id3_tag_findframe(id3_tag, "UFID", i);
@@ -284,65 +278,63 @@ tag_id3_import_ufid(struct id3_tag *id3_tag,
 			continue;
 
 		std::string p((const char *)value, length);
-		tag_handler_invoke_tag(handler, handler_ctx,
-				       TAG_MUSICBRAINZ_TRACKID, p.c_str());
+		handler.OnTag(TAG_MUSICBRAINZ_TRACKID, p.c_str());
 	}
 }
 
 void
-scan_id3_tag(struct id3_tag *tag,
-	     const TagHandler &handler, void *handler_ctx)
+scan_id3_tag(struct id3_tag *tag, TagHandler &handler) noexcept
 {
 	tag_id3_import_text(tag, ID3_FRAME_ARTIST, TAG_ARTIST,
-			    handler, handler_ctx);
+			    handler);
 	tag_id3_import_text(tag, ID3_FRAME_ALBUM_ARTIST,
-			    TAG_ALBUM_ARTIST, handler, handler_ctx);
+			    TAG_ALBUM_ARTIST, handler);
 	tag_id3_import_text(tag, ID3_FRAME_ARTIST_SORT,
-			    TAG_ARTIST_SORT, handler, handler_ctx);
+			    TAG_ARTIST_SORT, handler);
 
-	tag_id3_import_text(tag, "TSOA", TAG_ALBUM_SORT, handler, handler_ctx);
+	tag_id3_import_text(tag, "TSOA", TAG_ALBUM_SORT, handler);
 
 	tag_id3_import_text(tag, ID3_FRAME_ALBUM_ARTIST_SORT,
-			    TAG_ALBUM_ARTIST_SORT, handler, handler_ctx);
+			    TAG_ALBUM_ARTIST_SORT, handler);
 	tag_id3_import_text(tag, ID3_FRAME_TITLE, TAG_TITLE,
-			    handler, handler_ctx);
+			    handler);
 	tag_id3_import_text(tag, ID3_FRAME_ALBUM, TAG_ALBUM,
-			    handler, handler_ctx);
+			    handler);
 	tag_id3_import_text(tag, ID3_FRAME_TRACK, TAG_TRACK,
-			    handler, handler_ctx);
+			    handler);
 	tag_id3_import_text(tag, ID3_FRAME_YEAR, TAG_DATE,
-			    handler, handler_ctx);
+			    handler);
 	tag_id3_import_text(tag, ID3_FRAME_ORIGINAL_RELEASE_DATE, TAG_ORIGINAL_DATE,
-			    handler, handler_ctx);
+			    handler);
 	tag_id3_import_text(tag, ID3_FRAME_GENRE, TAG_GENRE,
-			    handler, handler_ctx);
+			    handler);
 	tag_id3_import_text(tag, ID3_FRAME_COMPOSER, TAG_COMPOSER,
-			    handler, handler_ctx);
+			    handler);
 	tag_id3_import_text(tag, "TPE3", TAG_PERFORMER,
-			    handler, handler_ctx);
-	tag_id3_import_text(tag, "TPE4", TAG_PERFORMER, handler, handler_ctx);
+			    handler);
+	tag_id3_import_text(tag, "TPE4", TAG_PERFORMER, handler);
 	tag_id3_import_comment(tag, ID3_FRAME_COMMENT, TAG_COMMENT,
-			       handler, handler_ctx);
+			       handler);
 	tag_id3_import_text(tag, ID3_FRAME_DISC, TAG_DISC,
-			    handler, handler_ctx);
+			    handler);
 
-	tag_id3_import_musicbrainz(tag, handler, handler_ctx);
-	tag_id3_import_ufid(tag, handler, handler_ctx);
+	tag_id3_import_musicbrainz(tag, handler);
+	tag_id3_import_ufid(tag, handler);
 }
 
 std::unique_ptr<Tag>
 tag_id3_import(struct id3_tag *tag)
 {
 	TagBuilder tag_builder;
-	scan_id3_tag(tag, add_tag_handler, &tag_builder);
+	AddTagHandler h(tag_builder);
+	scan_id3_tag(tag, h);
 	return tag_builder.empty()
 		? nullptr
 		: tag_builder.CommitNew();
 }
 
 bool
-tag_id3_scan(InputStream &is,
-	     const TagHandler &handler, void *handler_ctx)
+tag_id3_scan(InputStream &is, TagHandler &handler) noexcept
 {
 	UniqueId3Tag tag;
 
@@ -355,6 +347,6 @@ tag_id3_scan(InputStream &is,
 		return false;
 	}
 
-	scan_id3_tag(tag.get(), handler, handler_ctx);
+	scan_id3_tag(tag.get(), handler);
 	return true;
 }
diff --git a/src/tag/Id3Scan.hxx b/src/tag/Id3Scan.hxx
index d81e154a5..8ce23ad46 100644
--- a/src/tag/Id3Scan.hxx
+++ b/src/tag/Id3Scan.hxx
@@ -25,13 +25,12 @@
 #include <memory>
 
 class InputStream;
-struct TagHandler;
+class TagHandler;
 struct Tag;
 struct id3_tag;
 
 bool
-tag_id3_scan(InputStream &is,
-	     const TagHandler &handler, void *handler_ctx);
+tag_id3_scan(InputStream &is, TagHandler &handler) noexcept;
 
 std::unique_ptr<Tag>
 tag_id3_import(id3_tag *);
@@ -41,7 +40,6 @@ tag_id3_import(id3_tag *);
  *
  */
 void
-scan_id3_tag(id3_tag *tag,
-	     const TagHandler &handler, void *handler_ctx);
+scan_id3_tag(id3_tag *tag, TagHandler &handler) noexcept;
 
 #endif